Merge a00157cc (automated)

92 files changed, 2188 insertions, 763 deletions

diff --git a/pkg/abi/linux/mm.go b/pkg/abi/linux/mm.go
index 0b02f938a..cd043dac3 100644
--- a/pkg/abi/linux/mm.go
+++ b/pkg/abi/linux/mm.go
@@ -114,3 +114,12 @@ const (
 
 	MPOL_MODE_FLAGS = (MPOL_F_STATIC_NODES | MPOL_F_RELATIVE_NODES)
 )
+
+// Flags for mbind(2).
+const (
+	MPOL_MF_STRICT   = 1 << 0
+	MPOL_MF_MOVE     = 1 << 1
+	MPOL_MF_MOVE_ALL = 1 << 2
+
+	MPOL_MF_VALID = MPOL_MF_STRICT | MPOL_MF_MOVE | MPOL_MF_MOVE_ALL
+)
diff --git a/pkg/abi/linux/prctl.go b/pkg/abi/linux/prctl.go
index 0428282dd..391cfaa1c 100644
--- a/pkg/abi/linux/prctl.go
+++ b/pkg/abi/linux/prctl.go
@@ -155,3 +155,10 @@ const (
 	ARCH_GET_GS    = 0x1004
 	ARCH_SET_CPUID = 0x1012
 )
+
+// Flags for prctl(PR_SET_DUMPABLE), defined in include/linux/sched/coredump.h.
+const (
+	SUID_DUMP_DISABLE = 0
+	SUID_DUMP_USER    = 1
+	SUID_DUMP_ROOT    = 2
+)
diff --git a/pkg/abi/linux/socket.go b/pkg/abi/linux/socket.go
index 417840731..a714ac86d 100644
--- a/pkg/abi/linux/socket.go
+++ b/pkg/abi/linux/socket.go
@@ -102,15 +102,19 @@ const (
 	SOL_NETLINK = 270
 )
 
+// A SockType is a type (as opposed to family) of sockets. These are enumerated
+// below as SOCK_* constants.
+type SockType int
+
 // Socket types, from linux/net.h.
 const (
-	SOCK_STREAM    = 1
-	SOCK_DGRAM     = 2
-	SOCK_RAW       = 3
-	SOCK_RDM       = 4
-	SOCK_SEQPACKET = 5
-	SOCK_DCCP      = 6
-	SOCK_PACKET    = 10
+	SOCK_STREAM    SockType = 1
+	SOCK_DGRAM              = 2
+	SOCK_RAW                = 3
+	SOCK_RDM                = 4
+	SOCK_SEQPACKET          = 5
+	SOCK_DCCP               = 6
+	SOCK_PACKET             = 10
 )
 
 // SOCK_TYPE_MASK covers all of the above socket types. The remaining bits are
@@ -200,6 +204,22 @@ const (
 	SS_DISCONNECTING = 4 // In process of disconnecting.
 )
 
+// TCP protocol states, from include/net/tcp_states.h.
+const (
+	TCP_ESTABLISHED uint32 = iota + 1
+	TCP_SYN_SENT
+	TCP_SYN_RECV
+	TCP_FIN_WAIT1
+	TCP_FIN_WAIT2
+	TCP_TIME_WAIT
+	TCP_CLOSE
+	TCP_CLOSE_WAIT
+	TCP_LAST_ACK
+	TCP_LISTEN
+	TCP_CLOSING
+	TCP_NEW_SYN_RECV
+)
+
 // SockAddrMax is the maximum size of a struct sockaddr, from
 // uapi/linux/socket.h.
 const SockAddrMax = 128
diff --git a/pkg/sentry/memutil/memutil_state_autogen.go b/pkg/memutil/memutil_state_autogen.go
index 52f337963..52f337963 100755
--- a/pkg/sentry/memutil/memutil_state_autogen.go
+++ b/pkg/memutil/memutil_state_autogen.go
diff --git a/pkg/sentry/memutil/memutil_unsafe.go b/pkg/memutil/memutil_unsafe.go
index 92eab8a26..979d942a9 100644
--- a/pkg/sentry/memutil/memutil_unsafe.go
+++ b/pkg/memutil/memutil_unsafe.go
@@ -12,6 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// +build linux
+
+// Package memutil provides a wrapper for the memfd_create() system call.
 package memutil
 
 import (
diff --git a/pkg/sentry/fs/dirent.go b/pkg/sentry/fs/dirent.go
index c0bc261a2..a0a35c242 100644
--- a/pkg/sentry/fs/dirent.go
+++ b/pkg/sentry/fs/dirent.go
@@ -805,7 +805,7 @@ func (d *Dirent) Bind(ctx context.Context, root *Dirent, name string, data trans
 	var childDir *Dirent
 	err := d.genericCreate(ctx, root, name, func() error {
 		var e error
-		childDir, e = d.Inode.Bind(ctx, name, data, perms)
+		childDir, e = d.Inode.Bind(ctx, d, name, data, perms)
 		if e != nil {
 			return e
 		}
diff --git a/pkg/sentry/fs/gofer/socket.go b/pkg/sentry/fs/gofer/socket.go
index 7376fd76f..7ac0a421f 100644
--- a/pkg/sentry/fs/gofer/socket.go
+++ b/pkg/sentry/fs/gofer/socket.go
@@ -15,6 +15,7 @@
 package gofer
 
 import (
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
 	"gvisor.googlesource.com/gvisor/pkg/log"
 	"gvisor.googlesource.com/gvisor/pkg/p9"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
@@ -61,13 +62,13 @@ type endpoint struct {
 	path string
 }
 
-func unixSockToP9(t transport.SockType) (p9.ConnectFlags, bool) {
+func sockTypeToP9(t linux.SockType) (p9.ConnectFlags, bool) {
 	switch t {
-	case transport.SockStream:
+	case linux.SOCK_STREAM:
 		return p9.StreamSocket, true
-	case transport.SockSeqpacket:
+	case linux.SOCK_SEQPACKET:
 		return p9.SeqpacketSocket, true
-	case transport.SockDgram:
+	case linux.SOCK_DGRAM:
 		return p9.DgramSocket, true
 	}
 	return 0, false
@@ -75,7 +76,7 @@ func unixSockToP9(t transport.SockType) (p9.ConnectFlags, bool) {
 
 // BidirectionalConnect implements ConnectableEndpoint.BidirectionalConnect.
 func (e *endpoint) BidirectionalConnect(ce transport.ConnectingEndpoint, returnConnect func(transport.Receiver, transport.ConnectedEndpoint)) *syserr.Error {
-	cf, ok := unixSockToP9(ce.Type())
+	cf, ok := sockTypeToP9(ce.Type())
 	if !ok {
 		return syserr.ErrConnectionRefused
 	}
diff --git a/pkg/sentry/fs/host/host_state_autogen.go b/pkg/sentry/fs/host/host_state_autogen.go
index 22cfa1222..ab4e10990 100755
--- a/pkg/sentry/fs/host/host_state_autogen.go
+++ b/pkg/sentry/fs/host/host_state_autogen.go
@@ -98,8 +98,6 @@ func (x *ConnectedEndpoint) save(m state.Map) {
 	m.Save("queue", &x.queue)
 	m.Save("path", &x.path)
 	m.Save("ref", &x.ref)
-	m.Save("readClosed", &x.readClosed)
-	m.Save("writeClosed", &x.writeClosed)
 	m.Save("srfd", &x.srfd)
 	m.Save("stype", &x.stype)
 }
@@ -108,8 +106,6 @@ func (x *ConnectedEndpoint) load(m state.Map) {
 	m.Load("queue", &x.queue)
 	m.Load("path", &x.path)
 	m.Load("ref", &x.ref)
-	m.Load("readClosed", &x.readClosed)
-	m.Load("writeClosed", &x.writeClosed)
 	m.LoadWait("srfd", &x.srfd)
 	m.Load("stype", &x.stype)
 	m.AfterLoad(x.afterLoad)
diff --git a/pkg/sentry/fs/host/socket.go b/pkg/sentry/fs/host/socket.go
index 3ed137006..305eea718 100644
--- a/pkg/sentry/fs/host/socket.go
+++ b/pkg/sentry/fs/host/socket.go
@@ -15,9 +15,11 @@
 package host
 
 import (
+	"fmt"
 	"sync"
 	"syscall"
 
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
 	"gvisor.googlesource.com/gvisor/pkg/fd"
 	"gvisor.googlesource.com/gvisor/pkg/fdnotifier"
 	"gvisor.googlesource.com/gvisor/pkg/log"
@@ -51,25 +53,11 @@ type ConnectedEndpoint struct {
 	// ref keeps track of references to a connectedEndpoint.
 	ref refs.AtomicRefCount
 
-	// mu protects fd, readClosed and writeClosed.
-	mu sync.RWMutex `state:"nosave"`
-
-	// file is an *fd.FD containing the FD backing this endpoint. It must be
-	// set to nil if it has been closed.
-	file *fd.FD `state:"nosave"`
-
-	// readClosed is true if the FD has read shutdown or if it has been closed.
-	readClosed bool
-
-	// writeClosed is true if the FD has write shutdown or if it has been
-	// closed.
-	writeClosed bool
-
 	// If srfd >= 0, it is the host FD that file was imported from.
 	srfd int `state:"wait"`
 
 	// stype is the type of Unix socket.
-	stype transport.SockType
+	stype linux.SockType
 
 	// sndbuf is the size of the send buffer.
 	//
@@ -78,6 +66,13 @@ type ConnectedEndpoint struct {
 	// prevent lots of small messages from filling the real send buffer
 	// size on the host.
 	sndbuf int `state:"nosave"`
+
+	// mu protects the fields below.
+	mu sync.RWMutex `state:"nosave"`
+
+	// file is an *fd.FD containing the FD backing this endpoint. It must be
+	// set to nil if it has been closed.
+	file *fd.FD `state:"nosave"`
 }
 
 // init performs initialization required for creating new ConnectedEndpoints and
@@ -111,7 +106,7 @@ func (c *ConnectedEndpoint) init() *syserr.Error {
 		return syserr.ErrInvalidEndpointState
 	}
 
-	c.stype = transport.SockType(stype)
+	c.stype = linux.SockType(stype)
 	c.sndbuf = sndbuf
 
 	return nil
@@ -169,7 +164,7 @@ func NewSocketWithDirent(ctx context.Context, d *fs.Dirent, f *fd.FD, flags fs.F
 
 	ep := transport.NewExternal(e.stype, uniqueid.GlobalProviderFromContext(ctx), &q, e, e)
 
-	return unixsocket.NewWithDirent(ctx, d, ep, e.stype != transport.SockStream, flags), nil
+	return unixsocket.NewWithDirent(ctx, d, ep, e.stype, flags), nil
 }
 
 // newSocket allocates a new unix socket with host endpoint.
@@ -201,16 +196,13 @@ func newSocket(ctx context.Context, orgfd int, saveable bool) (*fs.File, error)
 
 	ep := transport.NewExternal(e.stype, uniqueid.GlobalProviderFromContext(ctx), &q, e, e)
 
-	return unixsocket.New(ctx, ep, e.stype != transport.SockStream), nil
+	return unixsocket.New(ctx, ep, e.stype), nil
 }
 
 // Send implements transport.ConnectedEndpoint.Send.
 func (c *ConnectedEndpoint) Send(data [][]byte, controlMessages transport.ControlMessages, from tcpip.FullAddress) (uintptr, bool, *syserr.Error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.writeClosed {
-		return 0, false, syserr.ErrClosedForSend
-	}
 
 	if !controlMessages.Empty() {
 		return 0, false, syserr.ErrInvalidEndpointState
@@ -218,7 +210,7 @@ func (c *ConnectedEndpoint) Send(data [][]byte, controlMessages transport.Contro
 
 	// Since stream sockets don't preserve message boundaries, we can write
 	// only as much of the message as fits in the send buffer.
-	truncate := c.stype == transport.SockStream
+	truncate := c.stype == linux.SOCK_STREAM
 
 	n, totalLen, err := fdWriteVec(c.file.FD(), data, c.sndbuf, truncate)
 	if n < totalLen && err == nil {
@@ -244,8 +236,13 @@ func (c *ConnectedEndpoint) SendNotify() {}
 // CloseSend implements transport.ConnectedEndpoint.CloseSend.
 func (c *ConnectedEndpoint) CloseSend() {
 	c.mu.Lock()
-	c.writeClosed = true
-	c.mu.Unlock()
+	defer c.mu.Unlock()
+
+	if err := syscall.Shutdown(c.file.FD(), syscall.SHUT_WR); err != nil {
+		// A well-formed UDS shutdown can't fail. See
+		// net/unix/af_unix.c:unix_shutdown.
+		panic(fmt.Sprintf("failed write shutdown on host socket %+v: %v", c, err))
+	}
 }
 
 // CloseNotify implements transport.ConnectedEndpoint.CloseNotify.
@@ -255,9 +252,7 @@ func (c *ConnectedEndpoint) CloseNotify() {}
 func (c *ConnectedEndpoint) Writable() bool {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.writeClosed {
-		return true
-	}
+
 	return fdnotifier.NonBlockingPoll(int32(c.file.FD()), waiter.EventOut)&waiter.EventOut != 0
 }
 
@@ -285,9 +280,6 @@ func (c *ConnectedEndpoint) EventUpdate() {
 func (c *ConnectedEndpoint) Recv(data [][]byte, creds bool, numRights uintptr, peek bool) (uintptr, uintptr, transport.ControlMessages, bool, tcpip.FullAddress, bool, *syserr.Error) {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.readClosed {
-		return 0, 0, transport.ControlMessages{}, false, tcpip.FullAddress{}, false, syserr.ErrClosedForReceive
-	}
 
 	var cm unet.ControlMessage
 	if numRights > 0 {
@@ -344,31 +336,34 @@ func (c *ConnectedEndpoint) RecvNotify() {}
 // CloseRecv implements transport.Receiver.CloseRecv.
 func (c *ConnectedEndpoint) CloseRecv() {
 	c.mu.Lock()
-	c.readClosed = true
-	c.mu.Unlock()
+	defer c.mu.Unlock()
+
+	if err := syscall.Shutdown(c.file.FD(), syscall.SHUT_RD); err != nil {
+		// A well-formed UDS shutdown can't fail. See
+		// net/unix/af_unix.c:unix_shutdown.
+		panic(fmt.Sprintf("failed read shutdown on host socket %+v: %v", c, err))
+	}
 }
 
 // Readable implements transport.Receiver.Readable.
 func (c *ConnectedEndpoint) Readable() bool {
 	c.mu.RLock()
 	defer c.mu.RUnlock()
-	if c.readClosed {
-		return true
-	}
+
 	return fdnotifier.NonBlockingPoll(int32(c.file.FD()), waiter.EventIn)&waiter.EventIn != 0
 }
 
 // SendQueuedSize implements transport.Receiver.SendQueuedSize.
 func (c *ConnectedEndpoint) SendQueuedSize() int64 {
-	// SendQueuedSize isn't supported for host sockets because we don't allow the
-	// sentry to call ioctl(2).
+	// TODO(gvisor.dev/issue/273): SendQueuedSize isn't supported for host
+	// sockets because we don't allow the sentry to call ioctl(2).
 	return -1
 }
 
 // RecvQueuedSize implements transport.Receiver.RecvQueuedSize.
 func (c *ConnectedEndpoint) RecvQueuedSize() int64 {
-	// RecvQueuedSize isn't supported for host sockets because we don't allow the
-	// sentry to call ioctl(2).
+	// TODO(gvisor.dev/issue/273): RecvQueuedSize isn't supported for host
+	// sockets because we don't allow the sentry to call ioctl(2).
 	return -1
 }
 
diff --git a/pkg/sentry/fs/inode.go b/pkg/sentry/fs/inode.go
index aef1a1cb9..0b54c2e77 100644
--- a/pkg/sentry/fs/inode.go
+++ b/pkg/sentry/fs/inode.go
@@ -220,9 +220,9 @@ func (i *Inode) Rename(ctx context.Context, oldParent *Dirent, renamed *Dirent,
 }
 
 // Bind calls i.InodeOperations.Bind with i as the directory.
-func (i *Inode) Bind(ctx context.Context, name string, data transport.BoundEndpoint, perm FilePermissions) (*Dirent, error) {
+func (i *Inode) Bind(ctx context.Context, parent *Dirent, name string, data transport.BoundEndpoint, perm FilePermissions) (*Dirent, error) {
 	if i.overlay != nil {
-		return overlayBind(ctx, i.overlay, name, data, perm)
+		return overlayBind(ctx, i.overlay, parent, name, data, perm)
 	}
 	return i.InodeOperations.Bind(ctx, i, name, data, perm)
 }
diff --git a/pkg/sentry/fs/inode_overlay.go b/pkg/sentry/fs/inode_overlay.go
index cdffe173b..06506fb20 100644
--- a/pkg/sentry/fs/inode_overlay.go
+++ b/pkg/sentry/fs/inode_overlay.go
@@ -398,14 +398,14 @@ func overlayRename(ctx context.Context, o *overlayEntry, oldParent *Dirent, rena
 	return nil
 }
 
-func overlayBind(ctx context.Context, o *overlayEntry, name string, data transport.BoundEndpoint, perm FilePermissions) (*Dirent, error) {
+func overlayBind(ctx context.Context, o *overlayEntry, parent *Dirent, name string, data transport.BoundEndpoint, perm FilePermissions) (*Dirent, error) {
+	if err := copyUp(ctx, parent); err != nil {
+		return nil, err
+	}
+
 	o.copyMu.RLock()
 	defer o.copyMu.RUnlock()
-	// We do not support doing anything exciting with sockets unless there
-	// is already a directory in the upper filesystem.
-	if o.upper == nil {
-		return nil, syserror.EOPNOTSUPP
-	}
+
 	d, err := o.upper.InodeOperations.Bind(ctx, o.upper, name, data, perm)
 	if err != nil {
 		return nil, err
diff --git a/pkg/sentry/fs/proc/inode.go b/pkg/sentry/fs/proc/inode.go
index 379569823..986bc0a45 100644
--- a/pkg/sentry/fs/proc/inode.go
+++ b/pkg/sentry/fs/proc/inode.go
@@ -21,11 +21,14 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/proc/device"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/mm"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 )
 
 // taskOwnedInodeOps wraps an fs.InodeOperations and overrides the UnstableAttr
-// method to return the task as the owner.
+// method to return either the task or root as the owner, depending on the
+// task's dumpability.
 //
 // +stateify savable
 type taskOwnedInodeOps struct {
@@ -41,9 +44,42 @@ func (i *taskOwnedInodeOps) UnstableAttr(ctx context.Context, inode *fs.Inode) (
 	if err != nil {
 		return fs.UnstableAttr{}, err
 	}
-	// Set the task owner as the file owner.
+
+	// By default, set the task owner as the file owner.
 	creds := i.t.Credentials()
 	uattr.Owner = fs.FileOwner{creds.EffectiveKUID, creds.EffectiveKGID}
+
+	// Linux doesn't apply dumpability adjustments to world
+	// readable/executable directories so that applications can stat
+	// /proc/PID to determine the effective UID of a process. See
+	// fs/proc/base.c:task_dump_owner.
+	if fs.IsDir(inode.StableAttr) && uattr.Perms == fs.FilePermsFromMode(0555) {
+		return uattr, nil
+	}
+
+	// If the task is not dumpable, then root (in the namespace preferred)
+	// owns the file.
+	var m *mm.MemoryManager
+	i.t.WithMuLocked(func(t *kernel.Task) {
+		m = t.MemoryManager()
+	})
+
+	if m == nil {
+		uattr.Owner.UID = auth.RootKUID
+		uattr.Owner.GID = auth.RootKGID
+	} else if m.Dumpability() != mm.UserDumpable {
+		if kuid := creds.UserNamespace.MapToKUID(auth.RootUID); kuid.Ok() {
+			uattr.Owner.UID = kuid
+		} else {
+			uattr.Owner.UID = auth.RootKUID
+		}
+		if kgid := creds.UserNamespace.MapToKGID(auth.RootGID); kgid.Ok() {
+			uattr.Owner.GID = kgid
+		} else {
+			uattr.Owner.GID = auth.RootKGID
+		}
+	}
+
 	return uattr, nil
 }
 
diff --git a/pkg/sentry/fs/proc/net.go b/pkg/sentry/fs/proc/net.go
index 4a107c739..034950158 100644
--- a/pkg/sentry/fs/proc/net.go
+++ b/pkg/sentry/fs/proc/net.go
@@ -27,6 +27,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/ramfs"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/inet"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/socket"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/unix"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/unix/transport"
 )
@@ -213,17 +214,18 @@ func (n *netUnix) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle) ([]s
 	fmt.Fprintf(&buf, "Num       RefCount Protocol Flags    Type St Inode Path\n")
 
 	// Entries
-	for _, sref := range n.k.ListSockets(linux.AF_UNIX) {
-		s := sref.Get()
+	for _, se := range n.k.ListSockets() {
+		s := se.Sock.Get()
 		if s == nil {
-			log.Debugf("Couldn't resolve weakref %v in socket table, racing with destruction?", sref)
+			log.Debugf("Couldn't resolve weakref %v in socket table, racing with destruction?", se.Sock)
 			continue
 		}
 		sfile := s.(*fs.File)
-		sops, ok := sfile.FileOperations.(*unix.SocketOperations)
-		if !ok {
-			panic(fmt.Sprintf("Found non-unix socket file in unix socket table: %+v", sfile))
+		if family, _, _ := sfile.FileOperations.(socket.Socket).Type(); family != linux.AF_UNIX {
+			// Not a unix socket.
+			continue
 		}
+		sops := sfile.FileOperations.(*unix.SocketOperations)
 
 		addr, err := sops.Endpoint().GetLocalAddress()
 		if err != nil {
@@ -240,24 +242,6 @@ func (n *netUnix) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle) ([]s
 			}
 		}
 
-		var sockState int
-		switch sops.Endpoint().Type() {
-		case linux.SOCK_DGRAM:
-			sockState = linux.SS_CONNECTING
-			// Unlike Linux, we don't have unbound connection-less sockets,
-			// so no SS_DISCONNECTING.
-
-		case linux.SOCK_SEQPACKET:
-			fallthrough
-		case linux.SOCK_STREAM:
-			// Connectioned.
-			if sops.Endpoint().(transport.ConnectingEndpoint).Connected() {
-				sockState = linux.SS_CONNECTED
-			} else {
-				sockState = linux.SS_UNCONNECTED
-			}
-		}
-
 		// In the socket entry below, the value for the 'Num' field requires
 		// some consideration. Linux prints the address to the struct
 		// unix_sock representing a socket in the kernel, but may redact the
@@ -282,7 +266,7 @@ func (n *netUnix) ReadSeqFileData(ctx context.Context, h seqfile.SeqHandle) ([]s
 			0,                             // Protocol, always 0 for UDS.
 			sockFlags,                     // Flags.
 			sops.Endpoint().Type(),        // Type.
-			sockState,                     // State.
+			sops.State(),                  // State.
 			sfile.InodeID(),               // Inode.
 		)
 
diff --git a/pkg/sentry/fs/proc/task.go b/pkg/sentry/fs/proc/task.go
index 77e03d349..21a965f90 100644
--- a/pkg/sentry/fs/proc/task.go
+++ b/pkg/sentry/fs/proc/task.go
@@ -96,7 +96,7 @@ func (p *proc) newTaskDir(t *kernel.Task, msrc *fs.MountSource, showSubtasks boo
 		contents["cgroup"] = newCGroupInode(t, msrc, p.cgroupControllers)
 	}
 
-	// TODO(b/31916171): Set EUID/EGID based on dumpability.
+	// N.B. taskOwnedInodeOps enforces dumpability-based ownership.
 	d := &taskDir{
 		Dir: *ramfs.NewDir(t, contents, fs.RootOwner, fs.FilePermsFromMode(0555)),
 		t:   t,
@@ -667,6 +667,21 @@ func newComm(t *kernel.Task, msrc *fs.MountSource) *fs.Inode {
 	return newProcInode(c, msrc, fs.SpecialFile, t)
 }
 
+// Check implements fs.InodeOperations.Check.
+func (c *comm) Check(ctx context.Context, inode *fs.Inode, p fs.PermMask) bool {
+	// This file can always be read or written by members of the same
+	// thread group. See fs/proc/base.c:proc_tid_comm_permission.
+	//
+	// N.B. This check is currently a no-op as we don't yet support writing
+	// and this file is world-readable anyways.
+	t := kernel.TaskFromContext(ctx)
+	if t != nil && t.ThreadGroup() == c.t.ThreadGroup() && !p.Execute {
+		return true
+	}
+
+	return fs.ContextCanAccessFile(ctx, inode, p)
+}
+
 // GetFile implements fs.InodeOperations.GetFile.
 func (c *comm) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
 	return fs.NewFile(ctx, dirent, flags, &commFile{t: c.t}), nil
diff --git a/pkg/sentry/fs/timerfd/timerfd.go b/pkg/sentry/fs/timerfd/timerfd.go
index bce5f091d..c1721f434 100644
--- a/pkg/sentry/fs/timerfd/timerfd.go
+++ b/pkg/sentry/fs/timerfd/timerfd.go
@@ -54,6 +54,8 @@ type TimerOperations struct {
 // NewFile returns a timerfd File that receives time from c.
 func NewFile(ctx context.Context, c ktime.Clock) *fs.File {
 	dirent := fs.NewDirent(anon.NewInode(ctx), "anon_inode:[timerfd]")
+	// Release the initial dirent reference after NewFile takes a reference.
+	defer dirent.DecRef()
 	tops := &TimerOperations{}
 	tops.timer = ktime.NewTimer(c, tops)
 	// Timerfds reject writes, but the Write flag must be set in order to
diff --git a/pkg/sentry/hostmm/cgroup.go b/pkg/sentry/hostmm/cgroup.go
new file mode 100644
index 000000000..e5cc26ab2
--- /dev/null
+++ b/pkg/sentry/hostmm/cgroup.go
@@ -0,0 +1,111 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package hostmm
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"path"
+	"strings"
+)
+
+// currentCgroupDirectory returns the directory for the cgroup for the given
+// controller in which the calling process resides.
+func currentCgroupDirectory(ctrl string) (string, error) {
+	root, err := cgroupRootDirectory(ctrl)
+	if err != nil {
+		return "", err
+	}
+	cg, err := currentCgroup(ctrl)
+	if err != nil {
+		return "", err
+	}
+	return path.Join(root, cg), nil
+}
+
+// cgroupRootDirectory returns the root directory for the cgroup hierarchy in
+// which the given cgroup controller is mounted in the calling process' mount
+// namespace.
+func cgroupRootDirectory(ctrl string) (string, error) {
+	const path = "/proc/self/mounts"
+	file, err := os.Open(path)
+	if err != nil {
+		return "", err
+	}
+	defer file.Close()
+
+	// Per proc(5) -> fstab(5):
+	// Each line of /proc/self/mounts describes a mount.
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		// Each line consists of 6 space-separated fields. Find the line for
+		// which the third field (fs_vfstype) is cgroup, and the fourth field
+		// (fs_mntops, a comma-separated list of mount options) contains
+		// ctrl.
+		var spec, file, vfstype, mntopts, freq, passno string
+		const nrfields = 6
+		line := scanner.Text()
+		n, err := fmt.Sscan(line, &spec, &file, &vfstype, &mntopts, &freq, &passno)
+		if err != nil {
+			return "", fmt.Errorf("failed to parse %s: %v", path, err)
+		}
+		if n != nrfields {
+			return "", fmt.Errorf("failed to parse %s: line %q: got %d fields, wanted %d", path, line, n, nrfields)
+		}
+		if vfstype != "cgroup" {
+			continue
+		}
+		for _, mntopt := range strings.Split(mntopts, ",") {
+			if mntopt == ctrl {
+				return file, nil
+			}
+		}
+	}
+	return "", fmt.Errorf("no cgroup hierarchy mounted for controller %s", ctrl)
+}
+
+// currentCgroup returns the cgroup for the given controller in which the
+// calling process resides. The returned string is a path that should be
+// interpreted as relative to cgroupRootDirectory(ctrl).
+func currentCgroup(ctrl string) (string, error) {
+	const path = "/proc/self/cgroup"
+	file, err := os.Open(path)
+	if err != nil {
+		return "", err
+	}
+	defer file.Close()
+
+	// Per proc(5) -> cgroups(7):
+	// Each line of /proc/self/cgroups describes a cgroup hierarchy.
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		// Each line consists of 3 colon-separated fields. Find the line for
+		// which the second field (controller-list, a comma-separated list of
+		// cgroup controllers) contains ctrl.
+		line := scanner.Text()
+		const nrfields = 3
+		fields := strings.Split(line, ":")
+		if len(fields) != nrfields {
+			return "", fmt.Errorf("failed to parse %s: line %q: got %d fields, wanted %d", path, line, len(fields), nrfields)
+		}
+		for _, controller := range strings.Split(fields[1], ",") {
+			if controller == ctrl {
+				return fields[2], nil
+			}
+		}
+	}
+	return "", fmt.Errorf("not a member of a cgroup hierarchy for controller %s", ctrl)
+}
diff --git a/pkg/sentry/hostmm/hostmm.go b/pkg/sentry/hostmm/hostmm.go
new file mode 100644
index 000000000..5432cada9
--- /dev/null
+++ b/pkg/sentry/hostmm/hostmm.go
@@ -0,0 +1,130 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package hostmm provides tools for interacting with the host Linux kernel's
+// virtual memory management subsystem.
+package hostmm
+
+import (
+	"fmt"
+	"os"
+	"path"
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/fd"
+	"gvisor.googlesource.com/gvisor/pkg/log"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+// NotifyCurrentMemcgPressureCallback requests that f is called whenever the
+// calling process' memory cgroup indicates memory pressure of the given level,
+// as specified by Linux's Documentation/cgroup-v1/memory.txt.
+//
+// If NotifyCurrentMemcgPressureCallback succeeds, it returns a function that
+// terminates the requested memory pressure notifications. This function may be
+// called at most once.
+func NotifyCurrentMemcgPressureCallback(f func(), level string) (func(), error) {
+	cgdir, err := currentCgroupDirectory("memory")
+	if err != nil {
+		return nil, err
+	}
+
+	pressurePath := path.Join(cgdir, "memory.pressure_level")
+	pressureFile, err := os.Open(pressurePath)
+	if err != nil {
+		return nil, err
+	}
+	defer pressureFile.Close()
+
+	eventControlPath := path.Join(cgdir, "cgroup.event_control")
+	eventControlFile, err := os.OpenFile(eventControlPath, os.O_WRONLY, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer eventControlFile.Close()
+
+	eventFD, err := newEventFD()
+	if err != nil {
+		return nil, err
+	}
+
+	// Don't use fmt.Fprintf since the whole string needs to be written in a
+	// single syscall.
+	eventControlStr := fmt.Sprintf("%d %d %s", eventFD.FD(), pressureFile.Fd(), level)
+	if n, err := eventControlFile.Write([]byte(eventControlStr)); n != len(eventControlStr) || err != nil {
+		eventFD.Close()
+		return nil, fmt.Errorf("error writing %q to %s: got (%d, %v), wanted (%d, nil)", eventControlStr, eventControlPath, n, err, len(eventControlStr))
+	}
+
+	log.Debugf("Receiving memory pressure level notifications from %s at level %q", pressurePath, level)
+	const sizeofUint64 = 8
+	// The most significant bit of the eventfd value is set by the stop
+	// function, which is practically unambiguous since it's not plausible for
+	// 2**63 pressure events to occur between eventfd reads.
+	const stopVal = 1 << 63
+	stopCh := make(chan struct{})
+	go func() { // S/R-SAFE: f provides synchronization if necessary
+		rw := fd.NewReadWriter(eventFD.FD())
+		var buf [sizeofUint64]byte
+		for {
+			n, err := rw.Read(buf[:])
+			if err != nil {
+				if err == syscall.EINTR {
+					continue
+				}
+				panic(fmt.Sprintf("failed to read from memory pressure level eventfd: %v", err))
+			}
+			if n != sizeofUint64 {
+				panic(fmt.Sprintf("short read from memory pressure level eventfd: got %d bytes, wanted %d", n, sizeofUint64))
+			}
+			val := usermem.ByteOrder.Uint64(buf[:])
+			if val >= stopVal {
+				// Assume this was due to the notifier's "destructor" (the
+				// function returned by NotifyCurrentMemcgPressureCallback
+				// below) being called.
+				eventFD.Close()
+				close(stopCh)
+				return
+			}
+			f()
+		}
+	}()
+	return func() {
+		rw := fd.NewReadWriter(eventFD.FD())
+		var buf [sizeofUint64]byte
+		usermem.ByteOrder.PutUint64(buf[:], stopVal)
+		for {
+			n, err := rw.Write(buf[:])
+			if err != nil {
+				if err == syscall.EINTR {
+					continue
+				}
+				panic(fmt.Sprintf("failed to write to memory pressure level eventfd: %v", err))
+			}
+			if n != sizeofUint64 {
+				panic(fmt.Sprintf("short write to memory pressure level eventfd: got %d bytes, wanted %d", n, sizeofUint64))
+			}
+			break
+		}
+		<-stopCh
+	}, nil
+}
+
+func newEventFD() (*fd.FD, error) {
+	f, _, e := syscall.Syscall(syscall.SYS_EVENTFD2, 0, 0, 0)
+	if e != 0 {
+		return nil, fmt.Errorf("failed to create eventfd: %v", e)
+	}
+	return fd.New(int(f)), nil
+}
diff --git a/pkg/sentry/hostmm/hostmm_state_autogen.go b/pkg/sentry/hostmm/hostmm_state_autogen.go
new file mode 100755
index 000000000..730de5101
--- /dev/null
+++ b/pkg/sentry/hostmm/hostmm_state_autogen.go
@@ -0,0 +1,4 @@
+// automatically generated by stateify.
+
+package hostmm
+
diff --git a/pkg/sentry/kernel/epoll/epoll.go b/pkg/sentry/kernel/epoll/epoll.go
index bbacba1f4..43ae22a5d 100644
--- a/pkg/sentry/kernel/epoll/epoll.go
+++ b/pkg/sentry/kernel/epoll/epoll.go
@@ -156,6 +156,8 @@ var cycleMu sync.Mutex
 func NewEventPoll(ctx context.Context) *fs.File {
 	// name matches fs/eventpoll.c:epoll_create1.
 	dirent := fs.NewDirent(anon.NewInode(ctx), fmt.Sprintf("anon_inode:[eventpoll]"))
+	// Release the initial dirent reference after NewFile takes a reference.
+	defer dirent.DecRef()
 	return fs.NewFile(ctx, dirent, fs.FileFlags{}, &EventPoll{
 		files: make(map[FileIdentifier]*pollEntry),
 	})
diff --git a/pkg/sentry/kernel/eventfd/eventfd.go b/pkg/sentry/kernel/eventfd/eventfd.go
index 2f900be38..fe474cbf0 100644
--- a/pkg/sentry/kernel/eventfd/eventfd.go
+++ b/pkg/sentry/kernel/eventfd/eventfd.go
@@ -69,6 +69,8 @@ type EventOperations struct {
 func New(ctx context.Context, initVal uint64, semMode bool) *fs.File {
 	// name matches fs/eventfd.c:eventfd_file_create.
 	dirent := fs.NewDirent(anon.NewInode(ctx), "anon_inode:[eventfd]")
+	// Release the initial dirent reference after NewFile takes a reference.
+	defer dirent.DecRef()
 	return fs.NewFile(ctx, dirent, fs.FileFlags{Read: true, Write: true}, &EventOperations{
 		val:     initVal,
 		semMode: semMode,
diff --git a/pkg/sentry/kernel/kernel.go b/pkg/sentry/kernel/kernel.go
index 85d73ace2..f253a81d9 100644
--- a/pkg/sentry/kernel/kernel.go
+++ b/pkg/sentry/kernel/kernel.go
@@ -182,9 +182,13 @@ type Kernel struct {
 	// danglingEndpoints is used to save / restore tcpip.DanglingEndpoints.
 	danglingEndpoints struct{} `state:".([]tcpip.Endpoint)"`
 
-	// socketTable is used to track all sockets on the system. Protected by
+	// sockets is the list of all network sockets the system. Protected by
 	// extMu.
-	socketTable map[int]map[*refs.WeakRef]struct{}
+	sockets socketList
+
+	// nextSocketEntry is the next entry number to use in sockets. Protected
+	// by extMu.
+	nextSocketEntry uint64
 
 	// deviceRegistry is used to save/restore device.SimpleDevices.
 	deviceRegistry struct{} `state:".(*device.Registry)"`
@@ -283,7 +287,6 @@ func (k *Kernel) Init(args InitKernelArgs) error {
 	k.monotonicClock = &timekeeperClock{tk: args.Timekeeper, c: sentrytime.Monotonic}
 	k.futexes = futex.NewManager()
 	k.netlinkPorts = port.New()
-	k.socketTable = make(map[int]map[*refs.WeakRef]struct{})
 
 	return nil
 }
@@ -1137,51 +1140,43 @@ func (k *Kernel) EmitUnimplementedEvent(ctx context.Context) {
 	})
 }
 
-// socketEntry represents a socket recorded in Kernel.socketTable. It implements
+// SocketEntry represents a socket recorded in Kernel.sockets. It implements
 // refs.WeakRefUser for sockets stored in the socket table.
 //
 // +stateify savable
-type socketEntry struct {
-	k      *Kernel
-	sock   *refs.WeakRef
-	family int
+type SocketEntry struct {
+	socketEntry
+	k    *Kernel
+	Sock *refs.WeakRef
+	ID   uint64 // Socket table entry number.
 }
 
 // WeakRefGone implements refs.WeakRefUser.WeakRefGone.
-func (s *socketEntry) WeakRefGone() {
+func (s *SocketEntry) WeakRefGone() {
 	s.k.extMu.Lock()
-	// k.socketTable is guaranteed to point to a valid socket table for s.family
-	// at this point, since we made sure of the fact when we created this
-	// socketEntry, and we never delete socket tables.
-	delete(s.k.socketTable[s.family], s.sock)
+	s.k.sockets.Remove(s)
 	s.k.extMu.Unlock()
 }
 
 // RecordSocket adds a socket to the system-wide socket table for tracking.
 //
 // Precondition: Caller must hold a reference to sock.
-func (k *Kernel) RecordSocket(sock *fs.File, family int) {
+func (k *Kernel) RecordSocket(sock *fs.File) {
 	k.extMu.Lock()
-	table, ok := k.socketTable[family]
-	if !ok {
-		table = make(map[*refs.WeakRef]struct{})
-		k.socketTable[family] = table
-	}
-	se := socketEntry{k: k, family: family}
-	se.sock = refs.NewWeakRef(sock, &se)
-	table[se.sock] = struct{}{}
+	id := k.nextSocketEntry
+	k.nextSocketEntry++
+	s := &SocketEntry{k: k, ID: id}
+	s.Sock = refs.NewWeakRef(sock, s)
+	k.sockets.PushBack(s)
 	k.extMu.Unlock()
 }
 
-// ListSockets returns a snapshot of all sockets of a given family.
-func (k *Kernel) ListSockets(family int) []*refs.WeakRef {
+// ListSockets returns a snapshot of all sockets.
+func (k *Kernel) ListSockets() []*SocketEntry {
 	k.extMu.Lock()
-	socks := []*refs.WeakRef{}
-	if table, ok := k.socketTable[family]; ok {
-		socks = make([]*refs.WeakRef, 0, len(table))
-		for s := range table {
-			socks = append(socks, s)
-		}
+	var socks []*SocketEntry
+	for s := k.sockets.Front(); s != nil; s = s.Next() {
+		socks = append(socks, s)
 	}
 	k.extMu.Unlock()
 	return socks
diff --git a/pkg/sentry/kernel/kernel_state_autogen.go b/pkg/sentry/kernel/kernel_state_autogen.go
index 82fd0abfd..86394d893 100755
--- a/pkg/sentry/kernel/kernel_state_autogen.go
+++ b/pkg/sentry/kernel/kernel_state_autogen.go
@@ -139,7 +139,8 @@ func (x *Kernel) save(m state.Map) {
 	m.Save("uniqueID", &x.uniqueID)
 	m.Save("nextInotifyCookie", &x.nextInotifyCookie)
 	m.Save("netlinkPorts", &x.netlinkPorts)
-	m.Save("socketTable", &x.socketTable)
+	m.Save("sockets", &x.sockets)
+	m.Save("nextSocketEntry", &x.nextSocketEntry)
 	m.Save("DirentCacheLimiter", &x.DirentCacheLimiter)
 }
 
@@ -167,25 +168,28 @@ func (x *Kernel) load(m state.Map) {
 	m.Load("uniqueID", &x.uniqueID)
 	m.Load("nextInotifyCookie", &x.nextInotifyCookie)
 	m.Load("netlinkPorts", &x.netlinkPorts)
-	m.Load("socketTable", &x.socketTable)
+	m.Load("sockets", &x.sockets)
+	m.Load("nextSocketEntry", &x.nextSocketEntry)
 	m.Load("DirentCacheLimiter", &x.DirentCacheLimiter)
 	m.LoadValue("danglingEndpoints", new([]tcpip.Endpoint), func(y interface{}) { x.loadDanglingEndpoints(y.([]tcpip.Endpoint)) })
 	m.LoadValue("deviceRegistry", new(*device.Registry), func(y interface{}) { x.loadDeviceRegistry(y.(*device.Registry)) })
 }
 
-func (x *socketEntry) beforeSave() {}
-func (x *socketEntry) save(m state.Map) {
+func (x *SocketEntry) beforeSave() {}
+func (x *SocketEntry) save(m state.Map) {
 	x.beforeSave()
+	m.Save("socketEntry", &x.socketEntry)
 	m.Save("k", &x.k)
-	m.Save("sock", &x.sock)
-	m.Save("family", &x.family)
+	m.Save("Sock", &x.Sock)
+	m.Save("ID", &x.ID)
 }
 
-func (x *socketEntry) afterLoad() {}
-func (x *socketEntry) load(m state.Map) {
+func (x *SocketEntry) afterLoad() {}
+func (x *SocketEntry) load(m state.Map) {
+	m.Load("socketEntry", &x.socketEntry)
 	m.Load("k", &x.k)
-	m.Load("sock", &x.sock)
-	m.Load("family", &x.family)
+	m.Load("Sock", &x.Sock)
+	m.Load("ID", &x.ID)
 }
 
 func (x *pendingSignals) beforeSave() {}
@@ -452,6 +456,32 @@ func (x *SignalHandlers) load(m state.Map) {
 	m.Load("actions", &x.actions)
 }
 
+func (x *socketList) beforeSave() {}
+func (x *socketList) save(m state.Map) {
+	x.beforeSave()
+	m.Save("head", &x.head)
+	m.Save("tail", &x.tail)
+}
+
+func (x *socketList) afterLoad() {}
+func (x *socketList) load(m state.Map) {
+	m.Load("head", &x.head)
+	m.Load("tail", &x.tail)
+}
+
+func (x *socketEntry) beforeSave() {}
+func (x *socketEntry) save(m state.Map) {
+	x.beforeSave()
+	m.Save("next", &x.next)
+	m.Save("prev", &x.prev)
+}
+
+func (x *socketEntry) afterLoad() {}
+func (x *socketEntry) load(m state.Map) {
+	m.Load("next", &x.next)
+	m.Load("prev", &x.prev)
+}
+
 func (x *SyscallTable) beforeSave() {}
 func (x *SyscallTable) save(m state.Map) {
 	x.beforeSave()
@@ -1090,7 +1120,7 @@ func init() {
 	state.Register("kernel.FSContext", (*FSContext)(nil), state.Fns{Save: (*FSContext).save, Load: (*FSContext).load})
 	state.Register("kernel.IPCNamespace", (*IPCNamespace)(nil), state.Fns{Save: (*IPCNamespace).save, Load: (*IPCNamespace).load})
 	state.Register("kernel.Kernel", (*Kernel)(nil), state.Fns{Save: (*Kernel).save, Load: (*Kernel).load})
-	state.Register("kernel.socketEntry", (*socketEntry)(nil), state.Fns{Save: (*socketEntry).save, Load: (*socketEntry).load})
+	state.Register("kernel.SocketEntry", (*SocketEntry)(nil), state.Fns{Save: (*SocketEntry).save, Load: (*SocketEntry).load})
 	state.Register("kernel.pendingSignals", (*pendingSignals)(nil), state.Fns{Save: (*pendingSignals).save, Load: (*pendingSignals).load})
 	state.Register("kernel.pendingSignalQueue", (*pendingSignalQueue)(nil), state.Fns{Save: (*pendingSignalQueue).save, Load: (*pendingSignalQueue).load})
 	state.Register("kernel.pendingSignal", (*pendingSignal)(nil), state.Fns{Save: (*pendingSignal).save, Load: (*pendingSignal).load})
@@ -1108,6 +1138,8 @@ func init() {
 	state.Register("kernel.Session", (*Session)(nil), state.Fns{Save: (*Session).save, Load: (*Session).load})
 	state.Register("kernel.ProcessGroup", (*ProcessGroup)(nil), state.Fns{Save: (*ProcessGroup).save, Load: (*ProcessGroup).load})
 	state.Register("kernel.SignalHandlers", (*SignalHandlers)(nil), state.Fns{Save: (*SignalHandlers).save, Load: (*SignalHandlers).load})
+	state.Register("kernel.socketList", (*socketList)(nil), state.Fns{Save: (*socketList).save, Load: (*socketList).load})
+	state.Register("kernel.socketEntry", (*socketEntry)(nil), state.Fns{Save: (*socketEntry).save, Load: (*socketEntry).load})
 	state.Register("kernel.SyscallTable", (*SyscallTable)(nil), state.Fns{Save: (*SyscallTable).save, Load: (*SyscallTable).load})
 	state.Register("kernel.syslog", (*syslog)(nil), state.Fns{Save: (*syslog).save, Load: (*syslog).load})
 	state.Register("kernel.Task", (*Task)(nil), state.Fns{Save: (*Task).save, Load: (*Task).load})
diff --git a/pkg/sentry/kernel/pipe/node.go b/pkg/sentry/kernel/pipe/node.go
index 926c4c623..dc7da529e 100644
--- a/pkg/sentry/kernel/pipe/node.go
+++ b/pkg/sentry/kernel/pipe/node.go
@@ -38,7 +38,11 @@ type inodeOperations struct {
 	fsutil.InodeNotMappable          `state:"nosave"`
 	fsutil.InodeNotSocket            `state:"nosave"`
 	fsutil.InodeNotSymlink           `state:"nosave"`
-	fsutil.InodeNotVirtual           `state:"nosave"`
+
+	// Marking pipe inodes as virtual allows them to be saved and restored
+	// even if they have been unlinked. We can get away with this because
+	// their state exists entirely within the sentry.
+	fsutil.InodeVirtual `state:"nosave"`
 
 	fsutil.InodeSimpleAttributes
 
@@ -86,7 +90,7 @@ func (i *inodeOperations) GetFile(ctx context.Context, d *fs.Dirent, flags fs.Fi
 
 	switch {
 	case flags.Read && !flags.Write: // O_RDONLY.
-		r := i.p.Open(ctx, flags)
+		r := i.p.Open(ctx, d, flags)
 		i.newHandleLocked(&i.rWakeup)
 
 		if i.p.isNamed && !flags.NonBlocking && !i.p.HasWriters() {
@@ -102,7 +106,7 @@ func (i *inodeOperations) GetFile(ctx context.Context, d *fs.Dirent, flags fs.Fi
 		return r, nil
 
 	case flags.Write && !flags.Read: // O_WRONLY.
-		w := i.p.Open(ctx, flags)
+		w := i.p.Open(ctx, d, flags)
 		i.newHandleLocked(&i.wWakeup)
 
 		if i.p.isNamed && !i.p.HasReaders() {
@@ -122,7 +126,7 @@ func (i *inodeOperations) GetFile(ctx context.Context, d *fs.Dirent, flags fs.Fi
 
 	case flags.Read && flags.Write: // O_RDWR.
 		// Pipes opened for read-write always succeeds without blocking.
-		rw := i.p.Open(ctx, flags)
+		rw := i.p.Open(ctx, d, flags)
 		i.newHandleLocked(&i.rWakeup)
 		i.newHandleLocked(&i.wWakeup)
 		return rw, nil
diff --git a/pkg/sentry/kernel/pipe/pipe.go b/pkg/sentry/kernel/pipe/pipe.go
index b65204492..73438dc62 100644
--- a/pkg/sentry/kernel/pipe/pipe.go
+++ b/pkg/sentry/kernel/pipe/pipe.go
@@ -71,11 +71,6 @@ type Pipe struct {
 	// This value is immutable.
 	atomicIOBytes int64
 
-	// The dirent backing this pipe. Shared by all readers and writers.
-	//
-	// This value is immutable.
-	Dirent *fs.Dirent
-
 	// The number of active readers for this pipe.
 	//
 	// Access atomically.
@@ -130,14 +125,20 @@ func NewPipe(ctx context.Context, isNamed bool, sizeBytes, atomicIOBytes int64)
 	if atomicIOBytes > sizeBytes {
 		atomicIOBytes = sizeBytes
 	}
-	p := &Pipe{
+	return &Pipe{
 		isNamed:       isNamed,
 		max:           sizeBytes,
 		atomicIOBytes: atomicIOBytes,
 	}
+}
 
-	// Build the fs.Dirent of this pipe, shared by all fs.Files associated
-	// with this pipe.
+// NewConnectedPipe initializes a pipe and returns a pair of objects
+// representing the read and write ends of the pipe.
+func NewConnectedPipe(ctx context.Context, sizeBytes, atomicIOBytes int64) (*fs.File, *fs.File) {
+	p := NewPipe(ctx, false /* isNamed */, sizeBytes, atomicIOBytes)
+
+	// Build an fs.Dirent for the pipe which will be shared by both
+	// returned files.
 	perms := fs.FilePermissions{
 		User: fs.PermMask{Read: true, Write: true},
 	}
@@ -150,36 +151,32 @@ func NewPipe(ctx context.Context, isNamed bool, sizeBytes, atomicIOBytes int64)
 		BlockSize: int64(atomicIOBytes),
 	}
 	ms := fs.NewPseudoMountSource()
-	p.Dirent = fs.NewDirent(fs.NewInode(iops, ms, sattr), fmt.Sprintf("pipe:[%d]", ino))
-	return p
-}
-
-// NewConnectedPipe initializes a pipe and returns a pair of objects
-// representing the read and write ends of the pipe.
-func NewConnectedPipe(ctx context.Context, sizeBytes, atomicIOBytes int64) (*fs.File, *fs.File) {
-	p := NewPipe(ctx, false /* isNamed */, sizeBytes, atomicIOBytes)
-	return p.Open(ctx, fs.FileFlags{Read: true}), p.Open(ctx, fs.FileFlags{Write: true})
+	d := fs.NewDirent(fs.NewInode(iops, ms, sattr), fmt.Sprintf("pipe:[%d]", ino))
+	// The p.Open calls below will each take a reference on the Dirent. We
+	// must drop the one we already have.
+	defer d.DecRef()
+	return p.Open(ctx, d, fs.FileFlags{Read: true}), p.Open(ctx, d, fs.FileFlags{Write: true})
 }
 
 // Open opens the pipe and returns a new file.
 //
 // Precondition: at least one of flags.Read or flags.Write must be set.
-func (p *Pipe) Open(ctx context.Context, flags fs.FileFlags) *fs.File {
+func (p *Pipe) Open(ctx context.Context, d *fs.Dirent, flags fs.FileFlags) *fs.File {
 	switch {
 	case flags.Read && flags.Write:
 		p.rOpen()
 		p.wOpen()
-		return fs.NewFile(ctx, p.Dirent, flags, &ReaderWriter{
+		return fs.NewFile(ctx, d, flags, &ReaderWriter{
 			Pipe: p,
 		})
 	case flags.Read:
 		p.rOpen()
-		return fs.NewFile(ctx, p.Dirent, flags, &Reader{
+		return fs.NewFile(ctx, d, flags, &Reader{
 			ReaderWriter: ReaderWriter{Pipe: p},
 		})
 	case flags.Write:
 		p.wOpen()
-		return fs.NewFile(ctx, p.Dirent, flags, &Writer{
+		return fs.NewFile(ctx, d, flags, &Writer{
 			ReaderWriter: ReaderWriter{Pipe: p},
 		})
 	default:
diff --git a/pkg/sentry/kernel/pipe/pipe_state_autogen.go b/pkg/sentry/kernel/pipe/pipe_state_autogen.go
index 5d3686109..095d2e713 100755
--- a/pkg/sentry/kernel/pipe/pipe_state_autogen.go
+++ b/pkg/sentry/kernel/pipe/pipe_state_autogen.go
@@ -67,7 +67,6 @@ func (x *Pipe) save(m state.Map) {
 	x.beforeSave()
 	m.Save("isNamed", &x.isNamed)
 	m.Save("atomicIOBytes", &x.atomicIOBytes)
-	m.Save("Dirent", &x.Dirent)
 	m.Save("readers", &x.readers)
 	m.Save("writers", &x.writers)
 	m.Save("data", &x.data)
@@ -80,7 +79,6 @@ func (x *Pipe) afterLoad() {}
 func (x *Pipe) load(m state.Map) {
 	m.Load("isNamed", &x.isNamed)
 	m.Load("atomicIOBytes", &x.atomicIOBytes)
-	m.Load("Dirent", &x.Dirent)
 	m.Load("readers", &x.readers)
 	m.Load("writers", &x.writers)
 	m.Load("data", &x.data)
diff --git a/pkg/sentry/kernel/ptrace.go b/pkg/sentry/kernel/ptrace.go
index 4423e7efd..193447b17 100644
--- a/pkg/sentry/kernel/ptrace.go
+++ b/pkg/sentry/kernel/ptrace.go
@@ -19,6 +19,7 @@ import (
 
 	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/mm"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 	"gvisor.googlesource.com/gvisor/pkg/syserror"
 )
@@ -92,6 +93,14 @@ const (
 // ptrace(2), subsection "Ptrace access mode checking". If attach is true, it
 // checks for access mode PTRACE_MODE_ATTACH; otherwise, it checks for access
 // mode PTRACE_MODE_READ.
+//
+// NOTE(b/30815691): The result of CanTrace is immediately stale (e.g., a
+// racing setuid(2) may change traceability). This may pose a risk when a task
+// changes from traceable to not traceable. This is only problematic across
+// execve, where privileges may increase.
+//
+// We currently do not implement privileged executables (set-user/group-ID bits
+// and file capabilities), so that case is not reachable.
 func (t *Task) CanTrace(target *Task, attach bool) bool {
 	// "1. If the calling thread and the target thread are in the same thread
 	// group, access is always allowed." - ptrace(2)
@@ -162,7 +171,13 @@ func (t *Task) CanTrace(target *Task, attach bool) bool {
 	if cgid := callerCreds.RealKGID; cgid != targetCreds.RealKGID || cgid != targetCreds.EffectiveKGID || cgid != targetCreds.SavedKGID {
 		return false
 	}
-	// TODO(b/31916171): dumpability check
+	var targetMM *mm.MemoryManager
+	target.WithMuLocked(func(t *Task) {
+		targetMM = t.MemoryManager()
+	})
+	if targetMM != nil && targetMM.Dumpability() != mm.UserDumpable {
+		return false
+	}
 	if callerCreds.UserNamespace != targetCreds.UserNamespace {
 		return false
 	}
diff --git a/pkg/sentry/kernel/seqatomic_taskgoroutineschedinfo.go b/pkg/sentry/kernel/seqatomic_taskgoroutineschedinfo.go
index 532b33b9e..5b4ad3062 100755
--- a/pkg/sentry/kernel/seqatomic_taskgoroutineschedinfo.go
+++ b/pkg/sentry/kernel/seqatomic_taskgoroutineschedinfo.go
@@ -2,10 +2,11 @@ package kernel
 
 import (
 	"fmt"
-	"gvisor.googlesource.com/gvisor/third_party/gvsync"
 	"reflect"
 	"strings"
 	"unsafe"
+
+	"gvisor.googlesource.com/gvisor/third_party/gvsync"
 )
 
 // SeqAtomicLoad returns a copy of *ptr, ensuring that the read does not race
diff --git a/pkg/sentry/kernel/socket_list.go b/pkg/sentry/kernel/socket_list.go
new file mode 100755
index 000000000..aed0a555e
--- /dev/null
+++ b/pkg/sentry/kernel/socket_list.go
@@ -0,0 +1,173 @@
+package kernel
+
+// ElementMapper provides an identity mapping by default.
+//
+// This can be replaced to provide a struct that maps elements to linker
+// objects, if they are not the same. An ElementMapper is not typically
+// required if: Linker is left as is, Element is left as is, or Linker and
+// Element are the same type.
+type socketElementMapper struct{}
+
+// linkerFor maps an Element to a Linker.
+//
+// This default implementation should be inlined.
+//
+//go:nosplit
+func (socketElementMapper) linkerFor(elem *SocketEntry) *SocketEntry { return elem }
+
+// List is an intrusive list. Entries can be added to or removed from the list
+// in O(1) time and with no additional memory allocations.
+//
+// The zero value for List is an empty list ready to use.
+//
+// To iterate over a list (where l is a List):
+//      for e := l.Front(); e != nil; e = e.Next() {
+// 		// do something with e.
+//      }
+//
+// +stateify savable
+type socketList struct {
+	head *SocketEntry
+	tail *SocketEntry
+}
+
+// Reset resets list l to the empty state.
+func (l *socketList) Reset() {
+	l.head = nil
+	l.tail = nil
+}
+
+// Empty returns true iff the list is empty.
+func (l *socketList) Empty() bool {
+	return l.head == nil
+}
+
+// Front returns the first element of list l or nil.
+func (l *socketList) Front() *SocketEntry {
+	return l.head
+}
+
+// Back returns the last element of list l or nil.
+func (l *socketList) Back() *SocketEntry {
+	return l.tail
+}
+
+// PushFront inserts the element e at the front of list l.
+func (l *socketList) PushFront(e *SocketEntry) {
+	socketElementMapper{}.linkerFor(e).SetNext(l.head)
+	socketElementMapper{}.linkerFor(e).SetPrev(nil)
+
+	if l.head != nil {
+		socketElementMapper{}.linkerFor(l.head).SetPrev(e)
+	} else {
+		l.tail = e
+	}
+
+	l.head = e
+}
+
+// PushBack inserts the element e at the back of list l.
+func (l *socketList) PushBack(e *SocketEntry) {
+	socketElementMapper{}.linkerFor(e).SetNext(nil)
+	socketElementMapper{}.linkerFor(e).SetPrev(l.tail)
+
+	if l.tail != nil {
+		socketElementMapper{}.linkerFor(l.tail).SetNext(e)
+	} else {
+		l.head = e
+	}
+
+	l.tail = e
+}
+
+// PushBackList inserts list m at the end of list l, emptying m.
+func (l *socketList) PushBackList(m *socketList) {
+	if l.head == nil {
+		l.head = m.head
+		l.tail = m.tail
+	} else if m.head != nil {
+		socketElementMapper{}.linkerFor(l.tail).SetNext(m.head)
+		socketElementMapper{}.linkerFor(m.head).SetPrev(l.tail)
+
+		l.tail = m.tail
+	}
+
+	m.head = nil
+	m.tail = nil
+}
+
+// InsertAfter inserts e after b.
+func (l *socketList) InsertAfter(b, e *SocketEntry) {
+	a := socketElementMapper{}.linkerFor(b).Next()
+	socketElementMapper{}.linkerFor(e).SetNext(a)
+	socketElementMapper{}.linkerFor(e).SetPrev(b)
+	socketElementMapper{}.linkerFor(b).SetNext(e)
+
+	if a != nil {
+		socketElementMapper{}.linkerFor(a).SetPrev(e)
+	} else {
+		l.tail = e
+	}
+}
+
+// InsertBefore inserts e before a.
+func (l *socketList) InsertBefore(a, e *SocketEntry) {
+	b := socketElementMapper{}.linkerFor(a).Prev()
+	socketElementMapper{}.linkerFor(e).SetNext(a)
+	socketElementMapper{}.linkerFor(e).SetPrev(b)
+	socketElementMapper{}.linkerFor(a).SetPrev(e)
+
+	if b != nil {
+		socketElementMapper{}.linkerFor(b).SetNext(e)
+	} else {
+		l.head = e
+	}
+}
+
+// Remove removes e from l.
+func (l *socketList) Remove(e *SocketEntry) {
+	prev := socketElementMapper{}.linkerFor(e).Prev()
+	next := socketElementMapper{}.linkerFor(e).Next()
+
+	if prev != nil {
+		socketElementMapper{}.linkerFor(prev).SetNext(next)
+	} else {
+		l.head = next
+	}
+
+	if next != nil {
+		socketElementMapper{}.linkerFor(next).SetPrev(prev)
+	} else {
+		l.tail = prev
+	}
+}
+
+// Entry is a default implementation of Linker. Users can add anonymous fields
+// of this type to their structs to make them automatically implement the
+// methods needed by List.
+//
+// +stateify savable
+type socketEntry struct {
+	next *SocketEntry
+	prev *SocketEntry
+}
+
+// Next returns the entry that follows e in the list.
+func (e *socketEntry) Next() *SocketEntry {
+	return e.next
+}
+
+// Prev returns the entry that precedes e in the list.
+func (e *socketEntry) Prev() *SocketEntry {
+	return e.prev
+}
+
+// SetNext assigns 'entry' as the entry that follows e in the list.
+func (e *socketEntry) SetNext(elem *SocketEntry) {
+	e.next = elem
+}
+
+// SetPrev assigns 'entry' as the entry that precedes e in the list.
+func (e *socketEntry) SetPrev(elem *SocketEntry) {
+	e.prev = elem
+}
diff --git a/pkg/sentry/kernel/task.go b/pkg/sentry/kernel/task.go
index f9378c2de..4d889422f 100644
--- a/pkg/sentry/kernel/task.go
+++ b/pkg/sentry/kernel/task.go
@@ -455,12 +455,13 @@ type Task struct {
 	// single numa node, all policies are no-ops. We only track this information
 	// so that we can return reasonable values if the application calls
 	// get_mempolicy(2) after setting a non-default policy. Note that in the
-	// real syscall, nodemask can be longer than 4 bytes, but we always report a
-	// single node so never need to save more than a single bit.
+	// real syscall, nodemask can be longer than a single unsigned long, but we
+	// always report a single node so never need to save more than a single
+	// bit.
 	//
 	// numaPolicy and numaNodeMask are protected by mu.
 	numaPolicy   int32
-	numaNodeMask uint32
+	numaNodeMask uint64
 
 	// If netns is true, the task is in a non-root network namespace. Network
 	// namespaces aren't currently implemented in full; being in a network
diff --git a/pkg/sentry/kernel/task_exec.go b/pkg/sentry/kernel/task_exec.go
index 5d1425d5c..35d5cb90c 100644
--- a/pkg/sentry/kernel/task_exec.go
+++ b/pkg/sentry/kernel/task_exec.go
@@ -68,6 +68,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/mm"
 	"gvisor.googlesource.com/gvisor/pkg/syserror"
 )
 
@@ -198,6 +199,12 @@ func (r *runSyscallAfterExecStop) execute(t *Task) taskRunState {
 		return flags.CloseOnExec
 	})
 
+	// NOTE(b/30815691): We currently do not implement privileged
+	// executables (set-user/group-ID bits and file capabilities). This
+	// allows us to unconditionally enable user dumpability on the new mm.
+	// See fs/exec.c:setup_new_exec.
+	r.tc.MemoryManager.SetDumpability(mm.UserDumpable)
+
 	// Switch to the new process.
 	t.MemoryManager().Deactivate()
 	t.mu.Lock()
diff --git a/pkg/sentry/kernel/task_identity.go b/pkg/sentry/kernel/task_identity.go
index 17f08729a..ec95f78d0 100644
--- a/pkg/sentry/kernel/task_identity.go
+++ b/pkg/sentry/kernel/task_identity.go
@@ -17,6 +17,7 @@ package kernel
 import (
 	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/mm"
 	"gvisor.googlesource.com/gvisor/pkg/syserror"
 )
 
@@ -206,8 +207,17 @@ func (t *Task) setKUIDsUncheckedLocked(newR, newE, newS auth.KUID) {
 	// (filesystem UIDs aren't implemented, nor are any of the capabilities in
 	// question)
 
-	// Not documented, but compare Linux's kernel/cred.c:commit_creds().
 	if oldE != newE {
+		// "[dumpability] is reset to the current value contained in
+		// the file /proc/sys/fs/suid_dumpable (which by default has
+		// the value 0), in the following circumstances: The process's
+		// effective user or group ID is changed." - prctl(2)
+		//
+		// (suid_dumpable isn't implemented, so we just use the
+		// default.
+		t.MemoryManager().SetDumpability(mm.NotDumpable)
+
+		// Not documented, but compare Linux's kernel/cred.c:commit_creds().
 		t.parentDeathSignal = 0
 	}
 }
@@ -303,8 +313,18 @@ func (t *Task) setKGIDsUncheckedLocked(newR, newE, newS auth.KGID) {
 	t.creds = t.creds.Fork() // See doc for creds.
 	t.creds.RealKGID, t.creds.EffectiveKGID, t.creds.SavedKGID = newR, newE, newS
 
-	// Not documented, but compare Linux's kernel/cred.c:commit_creds().
 	if oldE != newE {
+		// "[dumpability] is reset to the current value contained in
+		// the file /proc/sys/fs/suid_dumpable (which by default has
+		// the value 0), in the following circumstances: The process's
+		// effective user or group ID is changed." - prctl(2)
+		//
+		// (suid_dumpable isn't implemented, so we just use the
+		// default.
+		t.MemoryManager().SetDumpability(mm.NotDumpable)
+
+		// Not documented, but compare Linux's
+		// kernel/cred.c:commit_creds().
 		t.parentDeathSignal = 0
 	}
 }
diff --git a/pkg/sentry/kernel/task_sched.go b/pkg/sentry/kernel/task_sched.go
index 5455f6ea9..1c94ab11b 100644
--- a/pkg/sentry/kernel/task_sched.go
+++ b/pkg/sentry/kernel/task_sched.go
@@ -622,14 +622,14 @@ func (t *Task) SetNiceness(n int) {
 }
 
 // NumaPolicy returns t's current numa policy.
-func (t *Task) NumaPolicy() (policy int32, nodeMask uint32) {
+func (t *Task) NumaPolicy() (policy int32, nodeMask uint64) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 	return t.numaPolicy, t.numaNodeMask
 }
 
 // SetNumaPolicy sets t's numa policy.
-func (t *Task) SetNumaPolicy(policy int32, nodeMask uint32) {
+func (t *Task) SetNumaPolicy(policy int32, nodeMask uint64) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 	t.numaPolicy = policy
diff --git a/pkg/sentry/memutil/memutil.go b/pkg/sentry/memutil/memutil.go
deleted file mode 100644
index a4154c42a..000000000
--- a/pkg/sentry/memutil/memutil.go
+++ /dev/null
@@ -1,16 +0,0 @@
-// Copyright 2018 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-// Package memutil contains the utility functions for memory operations.
-package memutil
diff --git a/pkg/sentry/mm/lifecycle.go b/pkg/sentry/mm/lifecycle.go
index 7a65a62a2..7646d5ab2 100644
--- a/pkg/sentry/mm/lifecycle.go
+++ b/pkg/sentry/mm/lifecycle.go
@@ -37,6 +37,7 @@ func NewMemoryManager(p platform.Platform, mfp pgalloc.MemoryFileProvider) *Memo
 		privateRefs: &privateRefs{},
 		users:       1,
 		auxv:        arch.Auxv{},
+		dumpability: UserDumpable,
 		aioManager:  aioManager{contexts: make(map[uint64]*AIOContext)},
 	}
 }
@@ -79,8 +80,9 @@ func (mm *MemoryManager) Fork(ctx context.Context) (*MemoryManager, error) {
 		envv:                 mm.envv,
 		auxv:                 append(arch.Auxv(nil), mm.auxv...),
 		// IncRef'd below, once we know that there isn't an error.
-		executable: mm.executable,
-		aioManager: aioManager{contexts: make(map[uint64]*AIOContext)},
+		executable:  mm.executable,
+		dumpability: mm.dumpability,
+		aioManager:  aioManager{contexts: make(map[uint64]*AIOContext)},
 	}
 
 	// Copy vmas.
diff --git a/pkg/sentry/mm/metadata.go b/pkg/sentry/mm/metadata.go
index 9768e51f1..c218006ee 100644
--- a/pkg/sentry/mm/metadata.go
+++ b/pkg/sentry/mm/metadata.go
@@ -20,6 +20,36 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 )
 
+// Dumpability describes if and how core dumps should be created.
+type Dumpability int
+
+const (
+	// NotDumpable indicates that core dumps should never be created.
+	NotDumpable Dumpability = iota
+
+	// UserDumpable indicates that core dumps should be created, owned by
+	// the current user.
+	UserDumpable
+
+	// RootDumpable indicates that core dumps should be created, owned by
+	// root.
+	RootDumpable
+)
+
+// Dumpability returns the dumpability.
+func (mm *MemoryManager) Dumpability() Dumpability {
+	mm.metadataMu.Lock()
+	defer mm.metadataMu.Unlock()
+	return mm.dumpability
+}
+
+// SetDumpability sets the dumpability.
+func (mm *MemoryManager) SetDumpability(d Dumpability) {
+	mm.metadataMu.Lock()
+	defer mm.metadataMu.Unlock()
+	mm.dumpability = d
+}
+
 // ArgvStart returns the start of the application argument vector.
 //
 // There is no guarantee that this value is sensible w.r.t. ArgvEnd.
diff --git a/pkg/sentry/mm/mm.go b/pkg/sentry/mm/mm.go
index eb6defa2b..604866d04 100644
--- a/pkg/sentry/mm/mm.go
+++ b/pkg/sentry/mm/mm.go
@@ -219,6 +219,12 @@ type MemoryManager struct {
 	// executable is protected by metadataMu.
 	executable *fs.Dirent
 
+	// dumpability describes if and how this MemoryManager may be dumped to
+	// userspace.
+	//
+	// dumpability is protected by metadataMu.
+	dumpability Dumpability
+
 	// aioManager keeps track of AIOContexts used for async IOs. AIOManager
 	// must be cloned when CLONE_VM is used.
 	aioManager aioManager
@@ -270,6 +276,12 @@ type vma struct {
 
 	mlockMode memmap.MLockMode
 
+	// numaPolicy is the NUMA policy for this vma set by mbind().
+	numaPolicy int32
+
+	// numaNodemask is the NUMA nodemask for this vma set by mbind().
+	numaNodemask uint64
+
 	// If id is not nil, it controls the lifecycle of mappable and provides vma
 	// metadata shown in /proc/[pid]/maps, and the vma holds a reference.
 	id memmap.MappingIdentity
diff --git a/pkg/sentry/mm/mm_state_autogen.go b/pkg/sentry/mm/mm_state_autogen.go
index 160f347f8..7d69f438f 100755
--- a/pkg/sentry/mm/mm_state_autogen.go
+++ b/pkg/sentry/mm/mm_state_autogen.go
@@ -159,6 +159,7 @@ func (x *MemoryManager) save(m state.Map) {
 	m.Save("envv", &x.envv)
 	m.Save("auxv", &x.auxv)
 	m.Save("executable", &x.executable)
+	m.Save("dumpability", &x.dumpability)
 	m.Save("aioManager", &x.aioManager)
 }
 
@@ -181,6 +182,7 @@ func (x *MemoryManager) load(m state.Map) {
 	m.Load("envv", &x.envv)
 	m.Load("auxv", &x.auxv)
 	m.Load("executable", &x.executable)
+	m.Load("dumpability", &x.dumpability)
 	m.Load("aioManager", &x.aioManager)
 	m.AfterLoad(x.afterLoad)
 }
@@ -193,6 +195,8 @@ func (x *vma) save(m state.Map) {
 	m.Save("mappable", &x.mappable)
 	m.Save("off", &x.off)
 	m.Save("mlockMode", &x.mlockMode)
+	m.Save("numaPolicy", &x.numaPolicy)
+	m.Save("numaNodemask", &x.numaNodemask)
 	m.Save("id", &x.id)
 	m.Save("hint", &x.hint)
 }
@@ -202,6 +206,8 @@ func (x *vma) load(m state.Map) {
 	m.Load("mappable", &x.mappable)
 	m.Load("off", &x.off)
 	m.Load("mlockMode", &x.mlockMode)
+	m.Load("numaPolicy", &x.numaPolicy)
+	m.Load("numaNodemask", &x.numaNodemask)
 	m.Load("id", &x.id)
 	m.Load("hint", &x.hint)
 	m.LoadValue("realPerms", new(int), func(y interface{}) { x.loadRealPerms(y.(int)) })
diff --git a/pkg/sentry/mm/syscalls.go b/pkg/sentry/mm/syscalls.go
index af1e53f5d..9cf136532 100644
--- a/pkg/sentry/mm/syscalls.go
+++ b/pkg/sentry/mm/syscalls.go
@@ -973,6 +973,59 @@ func (mm *MemoryManager) MLockAll(ctx context.Context, opts MLockAllOpts) error
 	return nil
 }
 
+// NumaPolicy implements the semantics of Linux's get_mempolicy(MPOL_F_ADDR).
+func (mm *MemoryManager) NumaPolicy(addr usermem.Addr) (int32, uint64, error) {
+	mm.mappingMu.RLock()
+	defer mm.mappingMu.RUnlock()
+	vseg := mm.vmas.FindSegment(addr)
+	if !vseg.Ok() {
+		return 0, 0, syserror.EFAULT
+	}
+	vma := vseg.ValuePtr()
+	return vma.numaPolicy, vma.numaNodemask, nil
+}
+
+// SetNumaPolicy implements the semantics of Linux's mbind().
+func (mm *MemoryManager) SetNumaPolicy(addr usermem.Addr, length uint64, policy int32, nodemask uint64) error {
+	if !addr.IsPageAligned() {
+		return syserror.EINVAL
+	}
+	// Linux allows this to overflow.
+	la, _ := usermem.Addr(length).RoundUp()
+	ar, ok := addr.ToRange(uint64(la))
+	if !ok {
+		return syserror.EINVAL
+	}
+	if ar.Length() == 0 {
+		return nil
+	}
+
+	mm.mappingMu.Lock()
+	defer mm.mappingMu.Unlock()
+	defer func() {
+		mm.vmas.MergeRange(ar)
+		mm.vmas.MergeAdjacent(ar)
+	}()
+	vseg := mm.vmas.LowerBoundSegment(ar.Start)
+	lastEnd := ar.Start
+	for {
+		if !vseg.Ok() || lastEnd < vseg.Start() {
+			// "EFAULT: ... there was an unmapped hole in the specified memory
+			// range specified [sic] by addr and len." - mbind(2)
+			return syserror.EFAULT
+		}
+		vseg = mm.vmas.Isolate(vseg, ar)
+		vma := vseg.ValuePtr()
+		vma.numaPolicy = policy
+		vma.numaNodemask = nodemask
+		lastEnd = vseg.End()
+		if ar.End <= lastEnd {
+			return nil
+		}
+		vseg, _ = vseg.NextNonEmpty()
+	}
+}
+
 // Decommit implements the semantics of Linux's madvise(MADV_DONTNEED).
 func (mm *MemoryManager) Decommit(addr usermem.Addr, length uint64) error {
 	ar, ok := addr.ToRange(length)
diff --git a/pkg/sentry/mm/vma.go b/pkg/sentry/mm/vma.go
index 02203f79f..0af8de5b0 100644
--- a/pkg/sentry/mm/vma.go
+++ b/pkg/sentry/mm/vma.go
@@ -107,6 +107,7 @@ func (mm *MemoryManager) createVMALocked(ctx context.Context, opts memmap.MMapOp
 		private:        opts.Private,
 		growsDown:      opts.GrowsDown,
 		mlockMode:      opts.MLockMode,
+		numaPolicy:     linux.MPOL_DEFAULT,
 		id:             opts.MappingIdentity,
 		hint:           opts.Hint,
 	}
@@ -436,6 +437,8 @@ func (vmaSetFunctions) Merge(ar1 usermem.AddrRange, vma1 vma, ar2 usermem.AddrRa
 		vma1.private != vma2.private ||
 		vma1.growsDown != vma2.growsDown ||
 		vma1.mlockMode != vma2.mlockMode ||
+		vma1.numaPolicy != vma2.numaPolicy ||
+		vma1.numaNodemask != vma2.numaNodemask ||
 		vma1.id != vma2.id ||
 		vma1.hint != vma2.hint {
 		return vma{}, false
diff --git a/pkg/sentry/pgalloc/pgalloc.go b/pkg/sentry/pgalloc/pgalloc.go
index 2b9924ad7..6d91f1a7b 100644
--- a/pkg/sentry/pgalloc/pgalloc.go
+++ b/pkg/sentry/pgalloc/pgalloc.go
@@ -32,6 +32,7 @@ import (
 
 	"gvisor.googlesource.com/gvisor/pkg/log"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/hostmm"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usage"
@@ -162,6 +163,11 @@ type MemoryFile struct {
 
 	// evictionWG counts the number of goroutines currently performing evictions.
 	evictionWG sync.WaitGroup
+
+	// stopNotifyPressure stops memory cgroup pressure level
+	// notifications used to drive eviction. stopNotifyPressure is
+	// immutable.
+	stopNotifyPressure func()
 }
 
 // MemoryFileOpts provides options to NewMemoryFile.
@@ -169,6 +175,11 @@ type MemoryFileOpts struct {
 	// DelayedEviction controls the extent to which the MemoryFile may delay
 	// eviction of evictable allocations.
 	DelayedEviction DelayedEvictionType
+
+	// If UseHostMemcgPressure is true, use host memory cgroup pressure level
+	// notifications to determine when eviction is necessary. This option has
+	// no effect unless DelayedEviction is DelayedEvictionEnabled.
+	UseHostMemcgPressure bool
 }
 
 // DelayedEvictionType is the type of MemoryFileOpts.DelayedEviction.
@@ -186,9 +197,14 @@ const (
 	// evictable allocations until doing so is considered necessary to avoid
 	// performance degradation due to host memory pressure, or OOM kills.
 	//
-	// As of this writing, DelayedEvictionEnabled delays evictions until the
-	// reclaimer goroutine is out of work (pages to reclaim), then evicts all
-	// pending evictable allocations immediately.
+	// As of this writing, the behavior of DelayedEvictionEnabled depends on
+	// whether or not MemoryFileOpts.UseHostMemcgPressure is enabled:
+	//
+	// - If UseHostMemcgPressure is true, evictions are delayed until memory
+	// pressure is indicated.
+	//
+	// - Otherwise, evictions are only delayed until the reclaimer goroutine
+	// is out of work (pages to reclaim).
 	DelayedEvictionEnabled
 
 	// DelayedEvictionManual requires that evictable allocations are only
@@ -292,6 +308,22 @@ func NewMemoryFile(file *os.File, opts MemoryFileOpts) (*MemoryFile, error) {
 	}
 	f.mappings.Store(make([]uintptr, initialSize/chunkSize))
 	f.reclaimCond.L = &f.mu
+
+	if f.opts.DelayedEviction == DelayedEvictionEnabled && f.opts.UseHostMemcgPressure {
+		stop, err := hostmm.NotifyCurrentMemcgPressureCallback(func() {
+			f.mu.Lock()
+			startedAny := f.startEvictionsLocked()
+			f.mu.Unlock()
+			if startedAny {
+				log.Debugf("pgalloc.MemoryFile performing evictions due to memcg pressure")
+			}
+		}, "low")
+		if err != nil {
+			return nil, fmt.Errorf("failed to configure memcg pressure level notifications: %v", err)
+		}
+		f.stopNotifyPressure = stop
+	}
+
 	go f.runReclaim() // S/R-SAFE: f.mu
 
 	// The Linux kernel contains an optional feature called "Integrity
@@ -692,9 +724,11 @@ func (f *MemoryFile) MarkEvictable(user EvictableMemoryUser, er EvictableRange)
 			// Kick off eviction immediately.
 			f.startEvictionGoroutineLocked(user, info)
 		case DelayedEvictionEnabled:
-			// Ensure that the reclaimer goroutine is running, so that it can
-			// start eviction when necessary.
-			f.reclaimCond.Signal()
+			if !f.opts.UseHostMemcgPressure {
+				// Ensure that the reclaimer goroutine is running, so that it
+				// can start eviction when necessary.
+				f.reclaimCond.Signal()
+			}
 		}
 	}
 }
@@ -992,11 +1026,12 @@ func (f *MemoryFile) runReclaim() {
 		}
 		f.markReclaimed(fr)
 	}
+
 	// We only get here if findReclaimable finds f.destroyed set and returns
 	// false.
 	f.mu.Lock()
-	defer f.mu.Unlock()
 	if !f.destroyed {
+		f.mu.Unlock()
 		panic("findReclaimable broke out of reclaim loop, but destroyed is no longer set")
 	}
 	f.file.Close()
@@ -1016,6 +1051,13 @@ func (f *MemoryFile) runReclaim() {
 	}
 	// Similarly, invalidate f.mappings. (atomic.Value.Store(nil) panics.)
 	f.mappings.Store([]uintptr{})
+	f.mu.Unlock()
+
+	// This must be called without holding f.mu to avoid circular lock
+	// ordering.
+	if f.stopNotifyPressure != nil {
+		f.stopNotifyPressure()
+	}
 }
 
 func (f *MemoryFile) findReclaimable() (platform.FileRange, bool) {
@@ -1029,7 +1071,7 @@ func (f *MemoryFile) findReclaimable() (platform.FileRange, bool) {
 			if f.reclaimable {
 				break
 			}
-			if f.opts.DelayedEviction == DelayedEvictionEnabled {
+			if f.opts.DelayedEviction == DelayedEvictionEnabled && !f.opts.UseHostMemcgPressure {
 				// No work to do. Evict any pending evictable allocations to
 				// get more reclaimable pages before going to sleep.
 				f.startEvictionsLocked()
@@ -1089,14 +1131,17 @@ func (f *MemoryFile) StartEvictions() {
 }
 
 // Preconditions: f.mu must be locked.
-func (f *MemoryFile) startEvictionsLocked() {
+func (f *MemoryFile) startEvictionsLocked() bool {
+	startedAny := false
 	for user, info := range f.evictable {
 		// Don't start multiple goroutines to evict the same user's
 		// allocations.
 		if !info.evicting {
 			f.startEvictionGoroutineLocked(user, info)
+			startedAny = true
 		}
 	}
+	return startedAny
 }
 
 // Preconditions: info == f.evictable[user]. !info.evicting. f.mu must be
diff --git a/pkg/sentry/platform/ring0/defs_impl.go b/pkg/sentry/platform/ring0/defs_impl.go
index 582553bc7..1f48fa176 100755
--- a/pkg/sentry/platform/ring0/defs_impl.go
+++ b/pkg/sentry/platform/ring0/defs_impl.go
@@ -1,14 +1,14 @@
 package ring0
 
 import (
+	"gvisor.googlesource.com/gvisor/pkg/cpuid"
+	"io"
+	"reflect"
 	"syscall"
 
 	"fmt"
-	"gvisor.googlesource.com/gvisor/pkg/cpuid"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform/ring0/pagetables"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
-	"io"
-	"reflect"
 )
 
 var (
diff --git a/pkg/sentry/socket/epsocket/epsocket.go b/pkg/sentry/socket/epsocket/epsocket.go
index de4b963da..f67451179 100644
--- a/pkg/sentry/socket/epsocket/epsocket.go
+++ b/pkg/sentry/socket/epsocket/epsocket.go
@@ -44,7 +44,6 @@ import (
 	ktime "gvisor.googlesource.com/gvisor/pkg/sentry/kernel/time"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/socket"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/unimpl"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 	"gvisor.googlesource.com/gvisor/pkg/syserr"
@@ -52,6 +51,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/tcpip"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/stack"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/transport/tcp"
 	"gvisor.googlesource.com/gvisor/pkg/waiter"
 )
 
@@ -227,7 +227,8 @@ type SocketOperations struct {
 
 	family   int
 	Endpoint tcpip.Endpoint
-	skType   transport.SockType
+	skType   linux.SockType
+	protocol int
 
 	// readMu protects access to the below fields.
 	readMu sync.Mutex `state:"nosave"`
@@ -252,8 +253,8 @@ type SocketOperations struct {
 }
 
 // New creates a new endpoint socket.
-func New(t *kernel.Task, family int, skType transport.SockType, queue *waiter.Queue, endpoint tcpip.Endpoint) (*fs.File, *syserr.Error) {
-	if skType == transport.SockStream {
+func New(t *kernel.Task, family int, skType linux.SockType, protocol int, queue *waiter.Queue, endpoint tcpip.Endpoint) (*fs.File, *syserr.Error) {
+	if skType == linux.SOCK_STREAM {
 		if err := endpoint.SetSockOpt(tcpip.DelayOption(1)); err != nil {
 			return nil, syserr.TranslateNetstackError(err)
 		}
@@ -266,6 +267,7 @@ func New(t *kernel.Task, family int, skType transport.SockType, queue *waiter.Qu
 		family:   family,
 		Endpoint: endpoint,
 		skType:   skType,
+		protocol: protocol,
 	}), nil
 }
 
@@ -550,7 +552,7 @@ func (s *SocketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 		}
 	}
 
-	ns, err := New(t, s.family, s.skType, wq, ep)
+	ns, err := New(t, s.family, s.skType, s.protocol, wq, ep)
 	if err != nil {
 		return 0, nil, 0, err
 	}
@@ -578,7 +580,7 @@ func (s *SocketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 	}
 	fd, e := t.FDMap().NewFDFrom(0, ns, fdFlags, t.ThreadGroup().Limits())
 
-	t.Kernel().RecordSocket(ns, s.family)
+	t.Kernel().RecordSocket(ns)
 
 	return fd, addr, addrLen, syserr.FromError(e)
 }
@@ -637,7 +639,7 @@ func (s *SocketOperations) GetSockOpt(t *kernel.Task, level, name, outLen int) (
 
 // GetSockOpt can be used to implement the linux syscall getsockopt(2) for
 // sockets backed by a commonEndpoint.
-func GetSockOpt(t *kernel.Task, s socket.Socket, ep commonEndpoint, family int, skType transport.SockType, level, name, outLen int) (interface{}, *syserr.Error) {
+func GetSockOpt(t *kernel.Task, s socket.Socket, ep commonEndpoint, family int, skType linux.SockType, level, name, outLen int) (interface{}, *syserr.Error) {
 	switch level {
 	case linux.SOL_SOCKET:
 		return getSockOptSocket(t, s, ep, family, skType, name, outLen)
@@ -663,7 +665,7 @@ func GetSockOpt(t *kernel.Task, s socket.Socket, ep commonEndpoint, family int,
 }
 
 // getSockOptSocket implements GetSockOpt when level is SOL_SOCKET.
-func getSockOptSocket(t *kernel.Task, s socket.Socket, ep commonEndpoint, family int, skType transport.SockType, name, outLen int) (interface{}, *syserr.Error) {
+func getSockOptSocket(t *kernel.Task, s socket.Socket, ep commonEndpoint, family int, skType linux.SockType, name, outLen int) (interface{}, *syserr.Error) {
 	// TODO(b/124056281): Stop rejecting short optLen values in getsockopt.
 	switch name {
 	case linux.SO_TYPE:
@@ -2281,3 +2283,51 @@ func nicStateFlagsToLinux(f stack.NICStateFlags) uint32 {
 	}
 	return rv
 }
+
+// State implements socket.Socket.State. State translates the internal state
+// returned by netstack to values defined by Linux.
+func (s *SocketOperations) State() uint32 {
+	if s.family != linux.AF_INET && s.family != linux.AF_INET6 {
+		// States not implemented for this socket's family.
+		return 0
+	}
+
+	if !s.isPacketBased() {
+		// TCP socket.
+		switch tcp.EndpointState(s.Endpoint.State()) {
+		case tcp.StateEstablished:
+			return linux.TCP_ESTABLISHED
+		case tcp.StateSynSent:
+			return linux.TCP_SYN_SENT
+		case tcp.StateSynRecv:
+			return linux.TCP_SYN_RECV
+		case tcp.StateFinWait1:
+			return linux.TCP_FIN_WAIT1
+		case tcp.StateFinWait2:
+			return linux.TCP_FIN_WAIT2
+		case tcp.StateTimeWait:
+			return linux.TCP_TIME_WAIT
+		case tcp.StateClose, tcp.StateInitial, tcp.StateBound, tcp.StateConnecting, tcp.StateError:
+			return linux.TCP_CLOSE
+		case tcp.StateCloseWait:
+			return linux.TCP_CLOSE_WAIT
+		case tcp.StateLastAck:
+			return linux.TCP_LAST_ACK
+		case tcp.StateListen:
+			return linux.TCP_LISTEN
+		case tcp.StateClosing:
+			return linux.TCP_CLOSING
+		default:
+			// Internal or unknown state.
+			return 0
+		}
+	}
+
+	// TODO(b/112063468): Export states for UDP, ICMP, and raw sockets.
+	return 0
+}
+
+// Type implements socket.Socket.Type.
+func (s *SocketOperations) Type() (family int, skType linux.SockType, protocol int) {
+	return s.family, s.skType, s.protocol
+}
diff --git a/pkg/sentry/socket/epsocket/epsocket_state_autogen.go b/pkg/sentry/socket/epsocket/epsocket_state_autogen.go
index 4b407b796..37e0276fb 100755
--- a/pkg/sentry/socket/epsocket/epsocket_state_autogen.go
+++ b/pkg/sentry/socket/epsocket/epsocket_state_autogen.go
@@ -14,6 +14,7 @@ func (x *SocketOperations) save(m state.Map) {
 	m.Save("family", &x.family)
 	m.Save("Endpoint", &x.Endpoint)
 	m.Save("skType", &x.skType)
+	m.Save("protocol", &x.protocol)
 	m.Save("readView", &x.readView)
 	m.Save("readCM", &x.readCM)
 	m.Save("sender", &x.sender)
@@ -29,6 +30,7 @@ func (x *SocketOperations) load(m state.Map) {
 	m.Load("family", &x.family)
 	m.Load("Endpoint", &x.Endpoint)
 	m.Load("skType", &x.skType)
+	m.Load("protocol", &x.protocol)
 	m.Load("readView", &x.readView)
 	m.Load("readCM", &x.readCM)
 	m.Load("sender", &x.sender)
diff --git a/pkg/sentry/socket/epsocket/provider.go b/pkg/sentry/socket/epsocket/provider.go
index ec930d8d5..516582828 100644
--- a/pkg/sentry/socket/epsocket/provider.go
+++ b/pkg/sentry/socket/epsocket/provider.go
@@ -23,7 +23,6 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/socket"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.googlesource.com/gvisor/pkg/syserr"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
@@ -42,7 +41,7 @@ type provider struct {
 
 // getTransportProtocol figures out transport protocol. Currently only TCP,
 // UDP, and ICMP are supported.
-func getTransportProtocol(ctx context.Context, stype transport.SockType, protocol int) (tcpip.TransportProtocolNumber, *syserr.Error) {
+func getTransportProtocol(ctx context.Context, stype linux.SockType, protocol int) (tcpip.TransportProtocolNumber, *syserr.Error) {
 	switch stype {
 	case linux.SOCK_STREAM:
 		if protocol != 0 && protocol != syscall.IPPROTO_TCP {
@@ -80,7 +79,7 @@ func getTransportProtocol(ctx context.Context, stype transport.SockType, protoco
 }
 
 // Socket creates a new socket object for the AF_INET or AF_INET6 family.
-func (p *provider) Socket(t *kernel.Task, stype transport.SockType, protocol int) (*fs.File, *syserr.Error) {
+func (p *provider) Socket(t *kernel.Task, stype linux.SockType, protocol int) (*fs.File, *syserr.Error) {
 	// Fail right away if we don't have a stack.
 	stack := t.NetworkContext()
 	if stack == nil {
@@ -112,11 +111,11 @@ func (p *provider) Socket(t *kernel.Task, stype transport.SockType, protocol int
 		return nil, syserr.TranslateNetstackError(e)
 	}
 
-	return New(t, p.family, stype, wq, ep)
+	return New(t, p.family, stype, protocol, wq, ep)
 }
 
 // Pair just returns nil sockets (not supported).
-func (*provider) Pair(*kernel.Task, transport.SockType, int) (*fs.File, *fs.File, *syserr.Error) {
+func (*provider) Pair(*kernel.Task, linux.SockType, int) (*fs.File, *fs.File, *syserr.Error) {
 	return nil, nil, nil
 }
 
diff --git a/pkg/sentry/socket/hostinet/socket.go b/pkg/sentry/socket/hostinet/socket.go
index 41f9693bb..c62c8d8f1 100644
--- a/pkg/sentry/socket/hostinet/socket.go
+++ b/pkg/sentry/socket/hostinet/socket.go
@@ -19,7 +19,9 @@ import (
 	"syscall"
 
 	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/binary"
 	"gvisor.googlesource.com/gvisor/pkg/fdnotifier"
+	"gvisor.googlesource.com/gvisor/pkg/log"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
@@ -28,7 +30,6 @@ import (
 	ktime "gvisor.googlesource.com/gvisor/pkg/sentry/kernel/time"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/socket"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 	"gvisor.googlesource.com/gvisor/pkg/syserr"
 	"gvisor.googlesource.com/gvisor/pkg/syserror"
@@ -55,15 +56,22 @@ type socketOperations struct {
 	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
 	socket.SendReceiveTimeout
 
-	family int // Read-only.
-	fd     int // must be O_NONBLOCK
-	queue  waiter.Queue
+	family   int            // Read-only.
+	stype    linux.SockType // Read-only.
+	protocol int            // Read-only.
+	fd       int            // must be O_NONBLOCK
+	queue    waiter.Queue
 }
 
 var _ = socket.Socket(&socketOperations{})
 
-func newSocketFile(ctx context.Context, family int, fd int, nonblock bool) (*fs.File, *syserr.Error) {
-	s := &socketOperations{family: family, fd: fd}
+func newSocketFile(ctx context.Context, family int, stype linux.SockType, protocol int, fd int, nonblock bool) (*fs.File, *syserr.Error) {
+	s := &socketOperations{
+		family:   family,
+		stype:    stype,
+		protocol: protocol,
+		fd:       fd,
+	}
 	if err := fdnotifier.AddFD(int32(fd), &s.queue); err != nil {
 		return nil, syserr.FromError(err)
 	}
@@ -221,7 +229,7 @@ func (s *socketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 		return 0, peerAddr, peerAddrlen, syserr.FromError(syscallErr)
 	}
 
-	f, err := newSocketFile(t, s.family, fd, flags&syscall.SOCK_NONBLOCK != 0)
+	f, err := newSocketFile(t, s.family, s.stype, s.protocol, fd, flags&syscall.SOCK_NONBLOCK != 0)
 	if err != nil {
 		syscall.Close(fd)
 		return 0, nil, 0, err
@@ -232,7 +240,7 @@ func (s *socketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 		CloseOnExec: flags&syscall.SOCK_CLOEXEC != 0,
 	}
 	kfd, kerr := t.FDMap().NewFDFrom(0, f, fdFlags, t.ThreadGroup().Limits())
-	t.Kernel().RecordSocket(f, s.family)
+	t.Kernel().RecordSocket(f)
 	return kfd, peerAddr, peerAddrlen, syserr.FromError(kerr)
 }
 
@@ -519,12 +527,39 @@ func translateIOSyscallError(err error) error {
 	return err
 }
 
+// State implements socket.Socket.State.
+func (s *socketOperations) State() uint32 {
+	info := linux.TCPInfo{}
+	buf, err := getsockopt(s.fd, syscall.SOL_TCP, syscall.TCP_INFO, linux.SizeOfTCPInfo)
+	if err != nil {
+		if err != syscall.ENOPROTOOPT {
+			log.Warningf("Failed to get TCP socket info from %+v: %v", s, err)
+		}
+		// For non-TCP sockets, silently ignore the failure.
+		return 0
+	}
+	if len(buf) != linux.SizeOfTCPInfo {
+		// Unmarshal below will panic if getsockopt returns a buffer of
+		// unexpected size.
+		log.Warningf("Failed to get TCP socket info from %+v: getsockopt(2) returned %d bytes, expecting %d bytes.", s, len(buf), linux.SizeOfTCPInfo)
+		return 0
+	}
+
+	binary.Unmarshal(buf, usermem.ByteOrder, &info)
+	return uint32(info.State)
+}
+
+// Type implements socket.Socket.Type.
+func (s *socketOperations) Type() (family int, skType linux.SockType, protocol int) {
+	return s.family, s.stype, s.protocol
+}
+
 type socketProvider struct {
 	family int
 }
 
 // Socket implements socket.Provider.Socket.
-func (p *socketProvider) Socket(t *kernel.Task, stypeflags transport.SockType, protocol int) (*fs.File, *syserr.Error) {
+func (p *socketProvider) Socket(t *kernel.Task, stypeflags linux.SockType, protocol int) (*fs.File, *syserr.Error) {
 	// Check that we are using the host network stack.
 	stack := t.NetworkContext()
 	if stack == nil {
@@ -535,7 +570,7 @@ func (p *socketProvider) Socket(t *kernel.Task, stypeflags transport.SockType, p
 	}
 
 	// Only accept TCP and UDP.
-	stype := int(stypeflags) & linux.SOCK_TYPE_MASK
+	stype := stypeflags & linux.SOCK_TYPE_MASK
 	switch stype {
 	case syscall.SOCK_STREAM:
 		switch protocol {
@@ -558,15 +593,15 @@ func (p *socketProvider) Socket(t *kernel.Task, stypeflags transport.SockType, p
 	// Conservatively ignore all flags specified by the application and add
 	// SOCK_NONBLOCK since socketOperations requires it. Pass a protocol of 0
 	// to simplify the syscall filters, since 0 and IPPROTO_* are equivalent.
-	fd, err := syscall.Socket(p.family, stype|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
+	fd, err := syscall.Socket(p.family, int(stype)|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, 0)
 	if err != nil {
 		return nil, syserr.FromError(err)
 	}
-	return newSocketFile(t, p.family, fd, stypeflags&syscall.SOCK_NONBLOCK != 0)
+	return newSocketFile(t, p.family, stype, protocol, fd, stypeflags&syscall.SOCK_NONBLOCK != 0)
 }
 
 // Pair implements socket.Provider.Pair.
-func (p *socketProvider) Pair(t *kernel.Task, stype transport.SockType, protocol int) (*fs.File, *fs.File, *syserr.Error) {
+func (p *socketProvider) Pair(t *kernel.Task, stype linux.SockType, protocol int) (*fs.File, *fs.File, *syserr.Error) {
 	// Not supported by AF_INET/AF_INET6.
 	return nil, nil, nil
 }
diff --git a/pkg/sentry/socket/netlink/netlink_state_autogen.go b/pkg/sentry/socket/netlink/netlink_state_autogen.go
index 59d902798..e51a86b19 100755
--- a/pkg/sentry/socket/netlink/netlink_state_autogen.go
+++ b/pkg/sentry/socket/netlink/netlink_state_autogen.go
@@ -12,6 +12,7 @@ func (x *Socket) save(m state.Map) {
 	m.Save("SendReceiveTimeout", &x.SendReceiveTimeout)
 	m.Save("ports", &x.ports)
 	m.Save("protocol", &x.protocol)
+	m.Save("skType", &x.skType)
 	m.Save("ep", &x.ep)
 	m.Save("connection", &x.connection)
 	m.Save("bound", &x.bound)
@@ -24,6 +25,7 @@ func (x *Socket) load(m state.Map) {
 	m.Load("SendReceiveTimeout", &x.SendReceiveTimeout)
 	m.Load("ports", &x.ports)
 	m.Load("protocol", &x.protocol)
+	m.Load("skType", &x.skType)
 	m.Load("ep", &x.ep)
 	m.Load("connection", &x.connection)
 	m.Load("bound", &x.bound)
diff --git a/pkg/sentry/socket/netlink/provider.go b/pkg/sentry/socket/netlink/provider.go
index 76cf12fd4..5dc103877 100644
--- a/pkg/sentry/socket/netlink/provider.go
+++ b/pkg/sentry/socket/netlink/provider.go
@@ -22,7 +22,6 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/socket"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.googlesource.com/gvisor/pkg/syserr"
 )
 
@@ -66,10 +65,10 @@ type socketProvider struct {
 }
 
 // Socket implements socket.Provider.Socket.
-func (*socketProvider) Socket(t *kernel.Task, stype transport.SockType, protocol int) (*fs.File, *syserr.Error) {
+func (*socketProvider) Socket(t *kernel.Task, stype linux.SockType, protocol int) (*fs.File, *syserr.Error) {
 	// Netlink sockets must be specified as datagram or raw, but they
 	// behave the same regardless of type.
-	if stype != transport.SockDgram && stype != transport.SockRaw {
+	if stype != linux.SOCK_DGRAM && stype != linux.SOCK_RAW {
 		return nil, syserr.ErrSocketNotSupported
 	}
 
@@ -83,7 +82,7 @@ func (*socketProvider) Socket(t *kernel.Task, stype transport.SockType, protocol
 		return nil, err
 	}
 
-	s, err := NewSocket(t, p)
+	s, err := NewSocket(t, stype, p)
 	if err != nil {
 		return nil, err
 	}
@@ -94,7 +93,7 @@ func (*socketProvider) Socket(t *kernel.Task, stype transport.SockType, protocol
 }
 
 // Pair implements socket.Provider.Pair by returning an error.
-func (*socketProvider) Pair(*kernel.Task, transport.SockType, int) (*fs.File, *fs.File, *syserr.Error) {
+func (*socketProvider) Pair(*kernel.Task, linux.SockType, int) (*fs.File, *fs.File, *syserr.Error) {
 	// Netlink sockets never supports creating socket pairs.
 	return nil, nil, syserr.ErrNotSupported
 }
diff --git a/pkg/sentry/socket/netlink/socket.go b/pkg/sentry/socket/netlink/socket.go
index afd06ca33..62659784a 100644
--- a/pkg/sentry/socket/netlink/socket.go
+++ b/pkg/sentry/socket/netlink/socket.go
@@ -80,6 +80,10 @@ type Socket struct {
 	// protocol is the netlink protocol implementation.
 	protocol Protocol
 
+	// skType is the socket type. This is either SOCK_DGRAM or SOCK_RAW for
+	// netlink sockets.
+	skType linux.SockType
+
 	// ep is a datagram unix endpoint used to buffer messages sent from the
 	// kernel to userspace. RecvMsg reads messages from this endpoint.
 	ep transport.Endpoint
@@ -105,7 +109,7 @@ type Socket struct {
 var _ socket.Socket = (*Socket)(nil)
 
 // NewSocket creates a new Socket.
-func NewSocket(t *kernel.Task, protocol Protocol) (*Socket, *syserr.Error) {
+func NewSocket(t *kernel.Task, skType linux.SockType, protocol Protocol) (*Socket, *syserr.Error) {
 	// Datagram endpoint used to buffer kernel -> user messages.
 	ep := transport.NewConnectionless()
 
@@ -126,6 +130,7 @@ func NewSocket(t *kernel.Task, protocol Protocol) (*Socket, *syserr.Error) {
 	return &Socket{
 		ports:          t.Kernel().NetlinkPorts(),
 		protocol:       protocol,
+		skType:         skType,
 		ep:             ep,
 		connection:     connection,
 		sendBufferSize: defaultSendBufferSize,
@@ -616,3 +621,13 @@ func (s *Socket) Write(ctx context.Context, _ *fs.File, src usermem.IOSequence,
 	n, err := s.sendMsg(ctx, src, nil, 0, socket.ControlMessages{})
 	return int64(n), err.ToError()
 }
+
+// State implements socket.Socket.State.
+func (s *Socket) State() uint32 {
+	return s.ep.State()
+}
+
+// Type implements socket.Socket.Type.
+func (s *Socket) Type() (family int, skType linux.SockType, protocol int) {
+	return linux.AF_NETLINK, s.skType, s.protocol.Protocol()
+}
diff --git a/pkg/sentry/socket/rpcinet/socket.go b/pkg/sentry/socket/rpcinet/socket.go
index 55e0b6665..c22ff1ff0 100644
--- a/pkg/sentry/socket/rpcinet/socket.go
+++ b/pkg/sentry/socket/rpcinet/socket.go
@@ -32,7 +32,6 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/rpcinet/conn"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/rpcinet/notifier"
 	pb "gvisor.googlesource.com/gvisor/pkg/sentry/socket/rpcinet/syscall_rpc_go_proto"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/unimpl"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 	"gvisor.googlesource.com/gvisor/pkg/syserr"
@@ -54,7 +53,10 @@ type socketOperations struct {
 	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
 	socket.SendReceiveTimeout
 
-	family   int    // Read-only.
+	family   int            // Read-only.
+	stype    linux.SockType // Read-only.
+	protocol int            // Read-only.
+
 	fd       uint32 // must be O_NONBLOCK
 	wq       *waiter.Queue
 	rpcConn  *conn.RPCConnection
@@ -70,7 +72,7 @@ type socketOperations struct {
 var _ = socket.Socket(&socketOperations{})
 
 // New creates a new RPC socket.
-func newSocketFile(ctx context.Context, stack *Stack, family int, skType int, protocol int) (*fs.File, *syserr.Error) {
+func newSocketFile(ctx context.Context, stack *Stack, family int, skType linux.SockType, protocol int) (*fs.File, *syserr.Error) {
 	id, c := stack.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_Socket{&pb.SocketRequest{Family: int64(family), Type: int64(skType | syscall.SOCK_NONBLOCK), Protocol: int64(protocol)}}}, false /* ignoreResult */)
 	<-c
 
@@ -87,6 +89,8 @@ func newSocketFile(ctx context.Context, stack *Stack, family int, skType int, pr
 	defer dirent.DecRef()
 	return fs.NewFile(ctx, dirent, fs.FileFlags{Read: true, Write: true}, &socketOperations{
 		family:   family,
+		stype:    skType,
+		protocol: protocol,
 		wq:       &wq,
 		fd:       fd,
 		rpcConn:  stack.rpcConn,
@@ -333,7 +337,7 @@ func (s *socketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 	if err != nil {
 		return 0, nil, 0, syserr.FromError(err)
 	}
-	t.Kernel().RecordSocket(file, s.family)
+	t.Kernel().RecordSocket(file)
 
 	if peerRequested {
 		return fd, payload.Address.Address, payload.Address.Length, nil
@@ -830,12 +834,23 @@ func (s *socketOperations) SendMsg(t *kernel.Task, src usermem.IOSequence, to []
 	}
 }
 
+// State implements socket.Socket.State.
+func (s *socketOperations) State() uint32 {
+	// TODO(b/127845868): Define a new rpc to query the socket state.
+	return 0
+}
+
+// Type implements socket.Socket.Type.
+func (s *socketOperations) Type() (family int, skType linux.SockType, protocol int) {
+	return s.family, s.stype, s.protocol
+}
+
 type socketProvider struct {
 	family int
 }
 
 // Socket implements socket.Provider.Socket.
-func (p *socketProvider) Socket(t *kernel.Task, stypeflags transport.SockType, protocol int) (*fs.File, *syserr.Error) {
+func (p *socketProvider) Socket(t *kernel.Task, stypeflags linux.SockType, protocol int) (*fs.File, *syserr.Error) {
 	// Check that we are using the RPC network stack.
 	stack := t.NetworkContext()
 	if stack == nil {
@@ -851,7 +866,7 @@ func (p *socketProvider) Socket(t *kernel.Task, stypeflags transport.SockType, p
 	//
 	// Try to restrict the flags we will accept to minimize backwards
 	// incompatibility with netstack.
-	stype := int(stypeflags) & linux.SOCK_TYPE_MASK
+	stype := stypeflags & linux.SOCK_TYPE_MASK
 	switch stype {
 	case syscall.SOCK_STREAM:
 		switch protocol {
@@ -871,11 +886,11 @@ func (p *socketProvider) Socket(t *kernel.Task, stypeflags transport.SockType, p
 		return nil, nil
 	}
 
-	return newSocketFile(t, s, p.family, stype, 0)
+	return newSocketFile(t, s, p.family, stype, protocol)
 }
 
 // Pair implements socket.Provider.Pair.
-func (p *socketProvider) Pair(t *kernel.Task, stype transport.SockType, protocol int) (*fs.File, *fs.File, *syserr.Error) {
+func (p *socketProvider) Pair(t *kernel.Task, stype linux.SockType, protocol int) (*fs.File, *fs.File, *syserr.Error) {
 	// Not supported by AF_INET/AF_INET6.
 	return nil, nil, nil
 }
diff --git a/pkg/sentry/socket/socket.go b/pkg/sentry/socket/socket.go
index 9393acd28..d60944b6b 100644
--- a/pkg/sentry/socket/socket.go
+++ b/pkg/sentry/socket/socket.go
@@ -116,6 +116,13 @@ type Socket interface {
 	// SendTimeout gets the current timeout (in ns) for send operations. Zero
 	// means no timeout, and negative means DONTWAIT.
 	SendTimeout() int64
+
+	// State returns the current state of the socket, as represented by Linux in
+	// procfs. The returned state value is protocol-specific.
+	State() uint32
+
+	// Type returns the family, socket type and protocol of the socket.
+	Type() (family int, skType linux.SockType, protocol int)
 }
 
 // Provider is the interface implemented by providers of sockets for specific
@@ -126,12 +133,12 @@ type Provider interface {
 	// If a nil Socket _and_ a nil error is returned, it means that the
 	// protocol is not supported. A non-nil error should only be returned
 	// if the protocol is supported, but an error occurs during creation.
-	Socket(t *kernel.Task, stype transport.SockType, protocol int) (*fs.File, *syserr.Error)
+	Socket(t *kernel.Task, stype linux.SockType, protocol int) (*fs.File, *syserr.Error)
 
 	// Pair creates a pair of connected sockets.
 	//
 	// See Socket for error information.
-	Pair(t *kernel.Task, stype transport.SockType, protocol int) (*fs.File, *fs.File, *syserr.Error)
+	Pair(t *kernel.Task, stype linux.SockType, protocol int) (*fs.File, *fs.File, *syserr.Error)
 }
 
 // families holds a map of all known address families and their providers.
@@ -145,14 +152,14 @@ func RegisterProvider(family int, provider Provider) {
 }
 
 // New creates a new socket with the given family, type and protocol.
-func New(t *kernel.Task, family int, stype transport.SockType, protocol int) (*fs.File, *syserr.Error) {
+func New(t *kernel.Task, family int, stype linux.SockType, protocol int) (*fs.File, *syserr.Error) {
 	for _, p := range families[family] {
 		s, err := p.Socket(t, stype, protocol)
 		if err != nil {
 			return nil, err
 		}
 		if s != nil {
-			t.Kernel().RecordSocket(s, family)
+			t.Kernel().RecordSocket(s)
 			return s, nil
 		}
 	}
@@ -162,7 +169,7 @@ func New(t *kernel.Task, family int, stype transport.SockType, protocol int) (*f
 
 // Pair creates a new connected socket pair with the given family, type and
 // protocol.
-func Pair(t *kernel.Task, family int, stype transport.SockType, protocol int) (*fs.File, *fs.File, *syserr.Error) {
+func Pair(t *kernel.Task, family int, stype linux.SockType, protocol int) (*fs.File, *fs.File, *syserr.Error) {
 	providers, ok := families[family]
 	if !ok {
 		return nil, nil, syserr.ErrAddressFamilyNotSupported
@@ -175,8 +182,8 @@ func Pair(t *kernel.Task, family int, stype transport.SockType, protocol int) (*
 		}
 		if s1 != nil && s2 != nil {
 			k := t.Kernel()
-			k.RecordSocket(s1, family)
-			k.RecordSocket(s2, family)
+			k.RecordSocket(s1)
+			k.RecordSocket(s2)
 			return s1, s2, nil
 		}
 	}
diff --git a/pkg/sentry/socket/unix/transport/connectioned.go b/pkg/sentry/socket/unix/transport/connectioned.go
index 18e492862..db79ac904 100644
--- a/pkg/sentry/socket/unix/transport/connectioned.go
+++ b/pkg/sentry/socket/unix/transport/connectioned.go
@@ -17,6 +17,7 @@ package transport
 import (
 	"sync"
 
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
 	"gvisor.googlesource.com/gvisor/pkg/syserr"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip"
 	"gvisor.googlesource.com/gvisor/pkg/waiter"
@@ -44,7 +45,7 @@ type ConnectingEndpoint interface {
 	// Type returns the socket type, typically either SockStream or
 	// SockSeqpacket. The connection attempt must be aborted if this
 	// value doesn't match the ConnectableEndpoint's type.
-	Type() SockType
+	Type() linux.SockType
 
 	// GetLocalAddress returns the bound path.
 	GetLocalAddress() (tcpip.FullAddress, *tcpip.Error)
@@ -100,7 +101,7 @@ type connectionedEndpoint struct {
 	// stype is used by connecting sockets to ensure that they are the
 	// same type. The value is typically either tcpip.SockSeqpacket or
 	// tcpip.SockStream.
-	stype SockType
+	stype linux.SockType
 
 	// acceptedChan is per the TCP endpoint implementation. Note that the
 	// sockets in this channel are _already in the connected state_, and
@@ -111,7 +112,7 @@ type connectionedEndpoint struct {
 }
 
 // NewConnectioned creates a new unbound connectionedEndpoint.
-func NewConnectioned(stype SockType, uid UniqueIDProvider) Endpoint {
+func NewConnectioned(stype linux.SockType, uid UniqueIDProvider) Endpoint {
 	return &connectionedEndpoint{
 		baseEndpoint: baseEndpoint{Queue: &waiter.Queue{}},
 		id:           uid.UniqueID(),
@@ -121,7 +122,7 @@ func NewConnectioned(stype SockType, uid UniqueIDProvider) Endpoint {
 }
 
 // NewPair allocates a new pair of connected unix-domain connectionedEndpoints.
-func NewPair(stype SockType, uid UniqueIDProvider) (Endpoint, Endpoint) {
+func NewPair(stype linux.SockType, uid UniqueIDProvider) (Endpoint, Endpoint) {
 	a := &connectionedEndpoint{
 		baseEndpoint: baseEndpoint{Queue: &waiter.Queue{}},
 		id:           uid.UniqueID(),
@@ -138,7 +139,7 @@ func NewPair(stype SockType, uid UniqueIDProvider) (Endpoint, Endpoint) {
 	q1 := &queue{ReaderQueue: a.Queue, WriterQueue: b.Queue, limit: initialLimit}
 	q2 := &queue{ReaderQueue: b.Queue, WriterQueue: a.Queue, limit: initialLimit}
 
-	if stype == SockStream {
+	if stype == linux.SOCK_STREAM {
 		a.receiver = &streamQueueReceiver{queueReceiver: queueReceiver{q1}}
 		b.receiver = &streamQueueReceiver{queueReceiver: queueReceiver{q2}}
 	} else {
@@ -162,7 +163,7 @@ func NewPair(stype SockType, uid UniqueIDProvider) (Endpoint, Endpoint) {
 
 // NewExternal creates a new externally backed Endpoint. It behaves like a
 // socketpair.
-func NewExternal(stype SockType, uid UniqueIDProvider, queue *waiter.Queue, receiver Receiver, connected ConnectedEndpoint) Endpoint {
+func NewExternal(stype linux.SockType, uid UniqueIDProvider, queue *waiter.Queue, receiver Receiver, connected ConnectedEndpoint) Endpoint {
 	return &connectionedEndpoint{
 		baseEndpoint: baseEndpoint{Queue: queue, receiver: receiver, connected: connected},
 		id:           uid.UniqueID(),
@@ -177,7 +178,7 @@ func (e *connectionedEndpoint) ID() uint64 {
 }
 
 // Type implements ConnectingEndpoint.Type and Endpoint.Type.
-func (e *connectionedEndpoint) Type() SockType {
+func (e *connectionedEndpoint) Type() linux.SockType {
 	return e.stype
 }
 
@@ -293,7 +294,7 @@ func (e *connectionedEndpoint) BidirectionalConnect(ce ConnectingEndpoint, retur
 	}
 
 	writeQueue := &queue{ReaderQueue: ne.Queue, WriterQueue: ce.WaiterQueue(), limit: initialLimit}
-	if e.stype == SockStream {
+	if e.stype == linux.SOCK_STREAM {
 		ne.receiver = &streamQueueReceiver{queueReceiver: queueReceiver{readQueue: writeQueue}}
 	} else {
 		ne.receiver = &queueReceiver{readQueue: writeQueue}
@@ -308,7 +309,7 @@ func (e *connectionedEndpoint) BidirectionalConnect(ce ConnectingEndpoint, retur
 			writeQueue: writeQueue,
 		}
 		readQueue.IncRef()
-		if e.stype == SockStream {
+		if e.stype == linux.SOCK_STREAM {
 			returnConnect(&streamQueueReceiver{queueReceiver: queueReceiver{readQueue: readQueue}}, connected)
 		} else {
 			returnConnect(&queueReceiver{readQueue: readQueue}, connected)
@@ -428,7 +429,7 @@ func (e *connectionedEndpoint) Bind(addr tcpip.FullAddress, commit func() *syser
 func (e *connectionedEndpoint) SendMsg(data [][]byte, c ControlMessages, to BoundEndpoint) (uintptr, *syserr.Error) {
 	// Stream sockets do not support specifying the endpoint. Seqpacket
 	// sockets ignore the passed endpoint.
-	if e.stype == SockStream && to != nil {
+	if e.stype == linux.SOCK_STREAM && to != nil {
 		return 0, syserr.ErrNotSupported
 	}
 	return e.baseEndpoint.SendMsg(data, c, to)
@@ -458,3 +459,11 @@ func (e *connectionedEndpoint) Readiness(mask waiter.EventMask) waiter.EventMask
 
 	return ready
 }
+
+// State implements socket.Socket.State.
+func (e *connectionedEndpoint) State() uint32 {
+	if e.Connected() {
+		return linux.SS_CONNECTED
+	}
+	return linux.SS_UNCONNECTED
+}
diff --git a/pkg/sentry/socket/unix/transport/connectionless.go b/pkg/sentry/socket/unix/transport/connectionless.go
index 43ff875e4..81ebfba10 100644
--- a/pkg/sentry/socket/unix/transport/connectionless.go
+++ b/pkg/sentry/socket/unix/transport/connectionless.go
@@ -15,6 +15,7 @@
 package transport
 
 import (
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
 	"gvisor.googlesource.com/gvisor/pkg/syserr"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip"
 	"gvisor.googlesource.com/gvisor/pkg/waiter"
@@ -118,8 +119,8 @@ func (e *connectionlessEndpoint) SendMsg(data [][]byte, c ControlMessages, to Bo
 }
 
 // Type implements Endpoint.Type.
-func (e *connectionlessEndpoint) Type() SockType {
-	return SockDgram
+func (e *connectionlessEndpoint) Type() linux.SockType {
+	return linux.SOCK_DGRAM
 }
 
 // Connect attempts to connect directly to server.
@@ -194,3 +195,18 @@ func (e *connectionlessEndpoint) Readiness(mask waiter.EventMask) waiter.EventMa
 
 	return ready
 }
+
+// State implements socket.Socket.State.
+func (e *connectionlessEndpoint) State() uint32 {
+	e.Lock()
+	defer e.Unlock()
+
+	switch {
+	case e.isBound():
+		return linux.SS_UNCONNECTED
+	case e.Connected():
+		return linux.SS_CONNECTING
+	default:
+		return linux.SS_DISCONNECTING
+	}
+}
diff --git a/pkg/sentry/socket/unix/transport/unix.go b/pkg/sentry/socket/unix/transport/unix.go
index 37d82bb6b..5c55c529e 100644
--- a/pkg/sentry/socket/unix/transport/unix.go
+++ b/pkg/sentry/socket/unix/transport/unix.go
@@ -19,6 +19,7 @@ import (
 	"sync"
 	"sync/atomic"
 
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
 	"gvisor.googlesource.com/gvisor/pkg/syserr"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
@@ -28,21 +29,6 @@ import (
 // initialLimit is the starting limit for the socket buffers.
 const initialLimit = 16 * 1024
 
-// A SockType is a type (as opposed to family) of sockets. These are enumerated
-// in the syscall package as syscall.SOCK_* constants.
-type SockType int
-
-const (
-	// SockStream corresponds to syscall.SOCK_STREAM.
-	SockStream SockType = 1
-	// SockDgram corresponds to syscall.SOCK_DGRAM.
-	SockDgram SockType = 2
-	// SockRaw corresponds to syscall.SOCK_RAW.
-	SockRaw SockType = 3
-	// SockSeqpacket corresponds to syscall.SOCK_SEQPACKET.
-	SockSeqpacket SockType = 5
-)
-
 // A RightsControlMessage is a control message containing FDs.
 type RightsControlMessage interface {
 	// Clone returns a copy of the RightsControlMessage.
@@ -175,7 +161,7 @@ type Endpoint interface {
 
 	// Type return the socket type, typically either SockStream, SockDgram
 	// or SockSeqpacket.
-	Type() SockType
+	Type() linux.SockType
 
 	// GetLocalAddress returns the address to which the endpoint is bound.
 	GetLocalAddress() (tcpip.FullAddress, *tcpip.Error)
@@ -191,6 +177,10 @@ type Endpoint interface {
 	// GetSockOpt gets a socket option. opt should be a pointer to one of the
 	// tcpip.*Option types.
 	GetSockOpt(opt interface{}) *tcpip.Error
+
+	// State returns the current state of the socket, as represented by Linux in
+	// procfs.
+	State() uint32
 }
 
 // A Credentialer is a socket or endpoint that supports the SO_PASSCRED socket
@@ -625,7 +615,7 @@ type connectedEndpoint struct {
 		GetLocalAddress() (tcpip.FullAddress, *tcpip.Error)
 
 		// Type implements Endpoint.Type.
-		Type() SockType
+		Type() linux.SockType
 	}
 
 	writeQueue *queue
@@ -649,7 +639,7 @@ func (e *connectedEndpoint) Send(data [][]byte, controlMessages ControlMessages,
 	}
 
 	truncate := false
-	if e.endpoint.Type() == SockStream {
+	if e.endpoint.Type() == linux.SOCK_STREAM {
 		// Since stream sockets don't preserve message boundaries, we
 		// can write only as much of the message as fits in the queue.
 		truncate = true
diff --git a/pkg/sentry/socket/unix/unix.go b/pkg/sentry/socket/unix/unix.go
index 388cc0d8b..b07e8d67b 100644
--- a/pkg/sentry/socket/unix/unix.go
+++ b/pkg/sentry/socket/unix/unix.go
@@ -17,6 +17,7 @@
 package unix
 
 import (
+	"fmt"
 	"strings"
 	"syscall"
 
@@ -55,22 +56,22 @@ type SocketOperations struct {
 	refs.AtomicRefCount
 	socket.SendReceiveTimeout
 
-	ep       transport.Endpoint
-	isPacket bool
+	ep    transport.Endpoint
+	stype linux.SockType
 }
 
 // New creates a new unix socket.
-func New(ctx context.Context, endpoint transport.Endpoint, isPacket bool) *fs.File {
+func New(ctx context.Context, endpoint transport.Endpoint, stype linux.SockType) *fs.File {
 	dirent := socket.NewDirent(ctx, unixSocketDevice)
 	defer dirent.DecRef()
-	return NewWithDirent(ctx, dirent, endpoint, isPacket, fs.FileFlags{Read: true, Write: true})
+	return NewWithDirent(ctx, dirent, endpoint, stype, fs.FileFlags{Read: true, Write: true})
 }
 
 // NewWithDirent creates a new unix socket using an existing dirent.
-func NewWithDirent(ctx context.Context, d *fs.Dirent, ep transport.Endpoint, isPacket bool, flags fs.FileFlags) *fs.File {
+func NewWithDirent(ctx context.Context, d *fs.Dirent, ep transport.Endpoint, stype linux.SockType, flags fs.FileFlags) *fs.File {
 	return fs.NewFile(ctx, d, flags, &SocketOperations{
-		ep:       ep,
-		isPacket: isPacket,
+		ep:    ep,
+		stype: stype,
 	})
 }
 
@@ -88,6 +89,18 @@ func (s *SocketOperations) Release() {
 	s.DecRef()
 }
 
+func (s *SocketOperations) isPacket() bool {
+	switch s.stype {
+	case linux.SOCK_DGRAM, linux.SOCK_SEQPACKET:
+		return true
+	case linux.SOCK_STREAM:
+		return false
+	default:
+		// We shouldn't have allowed any other socket types during creation.
+		panic(fmt.Sprintf("Invalid socket type %d", s.stype))
+	}
+}
+
 // Endpoint extracts the transport.Endpoint.
 func (s *SocketOperations) Endpoint() transport.Endpoint {
 	return s.ep
@@ -193,7 +206,7 @@ func (s *SocketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 		}
 	}
 
-	ns := New(t, ep, s.isPacket)
+	ns := New(t, ep, s.stype)
 	defer ns.DecRef()
 
 	if flags&linux.SOCK_NONBLOCK != 0 {
@@ -221,7 +234,7 @@ func (s *SocketOperations) Accept(t *kernel.Task, peerRequested bool, flags int,
 		return 0, nil, 0, syserr.FromError(e)
 	}
 
-	t.Kernel().RecordSocket(ns, linux.AF_UNIX)
+	t.Kernel().RecordSocket(ns)
 
 	return fd, addr, addrLen, nil
 }
@@ -487,6 +500,7 @@ func (s *SocketOperations) RecvMsg(t *kernel.Task, dst usermem.IOSequence, flags
 	peek := flags&linux.MSG_PEEK != 0
 	dontWait := flags&linux.MSG_DONTWAIT != 0
 	waitAll := flags&linux.MSG_WAITALL != 0
+	isPacket := s.isPacket()
 
 	// Calculate the number of FDs for which we have space and if we are
 	// requesting credentials.
@@ -528,8 +542,8 @@ func (s *SocketOperations) RecvMsg(t *kernel.Task, dst usermem.IOSequence, flags
 			msgFlags |= linux.MSG_CTRUNC
 		}
 
-		if err != nil || dontWait || !waitAll || s.isPacket || n >= dst.NumBytes() {
-			if s.isPacket && n < int64(r.MsgSize) {
+		if err != nil || dontWait || !waitAll || isPacket || n >= dst.NumBytes() {
+			if isPacket && n < int64(r.MsgSize) {
 				msgFlags |= linux.MSG_TRUNC
 			}
 
@@ -570,11 +584,11 @@ func (s *SocketOperations) RecvMsg(t *kernel.Task, dst usermem.IOSequence, flags
 				total += n
 			}
 
-			if err != nil || !waitAll || s.isPacket || n >= dst.NumBytes() {
+			if err != nil || !waitAll || isPacket || n >= dst.NumBytes() {
 				if total > 0 {
 					err = nil
 				}
-				if s.isPacket && n < int64(r.MsgSize) {
+				if isPacket && n < int64(r.MsgSize) {
 					msgFlags |= linux.MSG_TRUNC
 				}
 				return int(total), msgFlags, from, fromLen, socket.ControlMessages{Unix: r.Control}, syserr.FromError(err)
@@ -596,11 +610,22 @@ func (s *SocketOperations) RecvMsg(t *kernel.Task, dst usermem.IOSequence, flags
 	}
 }
 
+// State implements socket.Socket.State.
+func (s *SocketOperations) State() uint32 {
+	return s.ep.State()
+}
+
+// Type implements socket.Socket.Type.
+func (s *SocketOperations) Type() (family int, skType linux.SockType, protocol int) {
+	// Unix domain sockets always have a protocol of 0.
+	return linux.AF_UNIX, s.stype, 0
+}
+
 // provider is a unix domain socket provider.
 type provider struct{}
 
 // Socket returns a new unix domain socket.
-func (*provider) Socket(t *kernel.Task, stype transport.SockType, protocol int) (*fs.File, *syserr.Error) {
+func (*provider) Socket(t *kernel.Task, stype linux.SockType, protocol int) (*fs.File, *syserr.Error) {
 	// Check arguments.
 	if protocol != 0 && protocol != linux.AF_UNIX /* PF_UNIX */ {
 		return nil, syserr.ErrProtocolNotSupported
@@ -608,43 +633,36 @@ func (*provider) Socket(t *kernel.Task, stype transport.SockType, protocol int)
 
 	// Create the endpoint and socket.
 	var ep transport.Endpoint
-	var isPacket bool
 	switch stype {
 	case linux.SOCK_DGRAM:
-		isPacket = true
 		ep = transport.NewConnectionless()
-	case linux.SOCK_SEQPACKET:
-		isPacket = true
-		fallthrough
-	case linux.SOCK_STREAM:
+	case linux.SOCK_SEQPACKET, linux.SOCK_STREAM:
 		ep = transport.NewConnectioned(stype, t.Kernel())
 	default:
 		return nil, syserr.ErrInvalidArgument
 	}
 
-	return New(t, ep, isPacket), nil
+	return New(t, ep, stype), nil
 }
 
 // Pair creates a new pair of AF_UNIX connected sockets.
-func (*provider) Pair(t *kernel.Task, stype transport.SockType, protocol int) (*fs.File, *fs.File, *syserr.Error) {
+func (*provider) Pair(t *kernel.Task, stype linux.SockType, protocol int) (*fs.File, *fs.File, *syserr.Error) {
 	// Check arguments.
 	if protocol != 0 && protocol != linux.AF_UNIX /* PF_UNIX */ {
 		return nil, nil, syserr.ErrProtocolNotSupported
 	}
 
-	var isPacket bool
 	switch stype {
-	case linux.SOCK_STREAM:
-	case linux.SOCK_DGRAM, linux.SOCK_SEQPACKET:
-		isPacket = true
+	case linux.SOCK_STREAM, linux.SOCK_DGRAM, linux.SOCK_SEQPACKET:
+		// Ok
 	default:
 		return nil, nil, syserr.ErrInvalidArgument
 	}
 
 	// Create the endpoints and sockets.
 	ep1, ep2 := transport.NewPair(stype, t.Kernel())
-	s1 := New(t, ep1, isPacket)
-	s2 := New(t, ep2, isPacket)
+	s1 := New(t, ep1, stype)
+	s2 := New(t, ep2, stype)
 
 	return s1, s2, nil
 }
diff --git a/pkg/sentry/socket/unix/unix_state_autogen.go b/pkg/sentry/socket/unix/unix_state_autogen.go
index 6f8d24b44..605f6fb59 100755
--- a/pkg/sentry/socket/unix/unix_state_autogen.go
+++ b/pkg/sentry/socket/unix/unix_state_autogen.go
@@ -12,7 +12,7 @@ func (x *SocketOperations) save(m state.Map) {
 	m.Save("AtomicRefCount", &x.AtomicRefCount)
 	m.Save("SendReceiveTimeout", &x.SendReceiveTimeout)
 	m.Save("ep", &x.ep)
-	m.Save("isPacket", &x.isPacket)
+	m.Save("stype", &x.stype)
 }
 
 func (x *SocketOperations) afterLoad() {}
@@ -20,7 +20,7 @@ func (x *SocketOperations) load(m state.Map) {
 	m.Load("AtomicRefCount", &x.AtomicRefCount)
 	m.Load("SendReceiveTimeout", &x.SendReceiveTimeout)
 	m.Load("ep", &x.ep)
-	m.Load("isPacket", &x.isPacket)
+	m.Load("stype", &x.stype)
 }
 
 func init() {
diff --git a/pkg/sentry/strace/socket.go b/pkg/sentry/strace/socket.go
index dbe53b9a2..0b5ef84c4 100644
--- a/pkg/sentry/strace/socket.go
+++ b/pkg/sentry/strace/socket.go
@@ -76,13 +76,13 @@ var SocketFamily = abi.ValueSet{
 
 // SocketType are the possible socket(2) types.
 var SocketType = abi.ValueSet{
-	linux.SOCK_STREAM:    "SOCK_STREAM",
-	linux.SOCK_DGRAM:     "SOCK_DGRAM",
-	linux.SOCK_RAW:       "SOCK_RAW",
-	linux.SOCK_RDM:       "SOCK_RDM",
-	linux.SOCK_SEQPACKET: "SOCK_SEQPACKET",
-	linux.SOCK_DCCP:      "SOCK_DCCP",
-	linux.SOCK_PACKET:    "SOCK_PACKET",
+	uint64(linux.SOCK_STREAM):    "SOCK_STREAM",
+	uint64(linux.SOCK_DGRAM):     "SOCK_DGRAM",
+	uint64(linux.SOCK_RAW):       "SOCK_RAW",
+	uint64(linux.SOCK_RDM):       "SOCK_RDM",
+	uint64(linux.SOCK_SEQPACKET): "SOCK_SEQPACKET",
+	uint64(linux.SOCK_DCCP):      "SOCK_DCCP",
+	uint64(linux.SOCK_PACKET):    "SOCK_PACKET",
 }
 
 // SocketFlagSet are the possible socket(2) flags.
diff --git a/pkg/sentry/syscalls/linux/linux64.go b/pkg/sentry/syscalls/linux/linux64.go
index 3e4d312af..ad88b1391 100644
--- a/pkg/sentry/syscalls/linux/linux64.go
+++ b/pkg/sentry/syscalls/linux/linux64.go
@@ -360,8 +360,7 @@ var AMD64 = &kernel.SyscallTable{
 		235: Utimes,
 		// @Syscall(Vserver, note:Not implemented by Linux)
 		236: syscalls.Error(syscall.ENOSYS), // Vserver, not implemented by Linux
-		// @Syscall(Mbind, returns:EPERM or ENOSYS, note:Returns EPERM if the process does not have cap_sys_nice; ENOSYS otherwise), TODO(b/117792295)
-		237: syscalls.CapError(linux.CAP_SYS_NICE), // may require cap_sys_nice
+		237: Mbind,
 		238: SetMempolicy,
 		239: GetMempolicy,
 		//     240: @Syscall(MqOpen), TODO(b/29354921)
diff --git a/pkg/sentry/syscalls/linux/sys_mempolicy.go b/pkg/sentry/syscalls/linux/sys_mempolicy.go
new file mode 100644
index 000000000..652b2c206
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/sys_mempolicy.go
@@ -0,0 +1,312 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package linux
+
+import (
+	"fmt"
+
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+// We unconditionally report a single NUMA node. This also means that our
+// "nodemask_t" is a single unsigned long (uint64).
+const (
+	maxNodes        = 1
+	allowedNodemask = (1 << maxNodes) - 1
+)
+
+func copyInNodemask(t *kernel.Task, addr usermem.Addr, maxnode uint32) (uint64, error) {
+	// "nodemask points to a bit mask of node IDs that contains up to maxnode
+	// bits. The bit mask size is rounded to the next multiple of
+	// sizeof(unsigned long), but the kernel will use bits only up to maxnode.
+	// A NULL value of nodemask or a maxnode value of zero specifies the empty
+	// set of nodes. If the value of maxnode is zero, the nodemask argument is
+	// ignored." - set_mempolicy(2). Unfortunately, most of this is inaccurate
+	// because of what appears to be a bug: mm/mempolicy.c:get_nodes() uses
+	// maxnode-1, not maxnode, as the number of bits.
+	bits := maxnode - 1
+	if bits > usermem.PageSize*8 { // also handles overflow from maxnode == 0
+		return 0, syserror.EINVAL
+	}
+	if bits == 0 {
+		return 0, nil
+	}
+	// Copy in the whole nodemask.
+	numUint64 := (bits + 63) / 64
+	buf := t.CopyScratchBuffer(int(numUint64) * 8)
+	if _, err := t.CopyInBytes(addr, buf); err != nil {
+		return 0, err
+	}
+	val := usermem.ByteOrder.Uint64(buf)
+	// Check that only allowed bits in the first unsigned long in the nodemask
+	// are set.
+	if val&^allowedNodemask != 0 {
+		return 0, syserror.EINVAL
+	}
+	// Check that all remaining bits in the nodemask are 0.
+	for i := 8; i < len(buf); i++ {
+		if buf[i] != 0 {
+			return 0, syserror.EINVAL
+		}
+	}
+	return val, nil
+}
+
+func copyOutNodemask(t *kernel.Task, addr usermem.Addr, maxnode uint32, val uint64) error {
+	// mm/mempolicy.c:copy_nodes_to_user() also uses maxnode-1 as the number of
+	// bits.
+	bits := maxnode - 1
+	if bits > usermem.PageSize*8 { // also handles overflow from maxnode == 0
+		return syserror.EINVAL
+	}
+	if bits == 0 {
+		return nil
+	}
+	// Copy out the first unsigned long in the nodemask.
+	buf := t.CopyScratchBuffer(8)
+	usermem.ByteOrder.PutUint64(buf, val)
+	if _, err := t.CopyOutBytes(addr, buf); err != nil {
+		return err
+	}
+	// Zero out remaining unsigned longs in the nodemask.
+	if bits > 64 {
+		remAddr, ok := addr.AddLength(8)
+		if !ok {
+			return syserror.EFAULT
+		}
+		remUint64 := (bits - 1) / 64
+		if _, err := t.MemoryManager().ZeroOut(t, remAddr, int64(remUint64)*8, usermem.IOOpts{
+			AddressSpaceActive: true,
+		}); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// GetMempolicy implements the syscall get_mempolicy(2).
+func GetMempolicy(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	mode := args[0].Pointer()
+	nodemask := args[1].Pointer()
+	maxnode := args[2].Uint()
+	addr := args[3].Pointer()
+	flags := args[4].Uint()
+
+	if flags&^(linux.MPOL_F_NODE|linux.MPOL_F_ADDR|linux.MPOL_F_MEMS_ALLOWED) != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+	nodeFlag := flags&linux.MPOL_F_NODE != 0
+	addrFlag := flags&linux.MPOL_F_ADDR != 0
+	memsAllowed := flags&linux.MPOL_F_MEMS_ALLOWED != 0
+
+	// "EINVAL: The value specified by maxnode is less than the number of node
+	// IDs supported by the system." - get_mempolicy(2)
+	if nodemask != 0 && maxnode < maxNodes {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// "If flags specifies MPOL_F_MEMS_ALLOWED [...], the mode argument is
+	// ignored and the set of nodes (memories) that the thread is allowed to
+	// specify in subsequent calls to mbind(2) or set_mempolicy(2) (in the
+	// absence of any mode flags) is returned in nodemask."
+	if memsAllowed {
+		// "It is not permitted to combine MPOL_F_MEMS_ALLOWED with either
+		// MPOL_F_ADDR or MPOL_F_NODE."
+		if nodeFlag || addrFlag {
+			return 0, nil, syserror.EINVAL
+		}
+		if err := copyOutNodemask(t, nodemask, maxnode, allowedNodemask); err != nil {
+			return 0, nil, err
+		}
+		return 0, nil, nil
+	}
+
+	// "If flags specifies MPOL_F_ADDR, then information is returned about the
+	// policy governing the memory address given in addr. ... If the mode
+	// argument is not NULL, then get_mempolicy() will store the policy mode
+	// and any optional mode flags of the requested NUMA policy in the location
+	// pointed to by this argument. If nodemask is not NULL, then the nodemask
+	// associated with the policy will be stored in the location pointed to by
+	// this argument."
+	if addrFlag {
+		policy, nodemaskVal, err := t.MemoryManager().NumaPolicy(addr)
+		if err != nil {
+			return 0, nil, err
+		}
+		if nodeFlag {
+			// "If flags specifies both MPOL_F_NODE and MPOL_F_ADDR,
+			// get_mempolicy() will return the node ID of the node on which the
+			// address addr is allocated into the location pointed to by mode.
+			// If no page has yet been allocated for the specified address,
+			// get_mempolicy() will allocate a page as if the thread had
+			// performed a read (load) access to that address, and return the
+			// ID of the node where that page was allocated."
+			buf := t.CopyScratchBuffer(1)
+			_, err := t.CopyInBytes(addr, buf)
+			if err != nil {
+				return 0, nil, err
+			}
+			policy = 0 // maxNodes == 1
+		}
+		if mode != 0 {
+			if _, err := t.CopyOut(mode, policy); err != nil {
+				return 0, nil, err
+			}
+		}
+		if nodemask != 0 {
+			if err := copyOutNodemask(t, nodemask, maxnode, nodemaskVal); err != nil {
+				return 0, nil, err
+			}
+		}
+		return 0, nil, nil
+	}
+
+	// "EINVAL: ... flags specified MPOL_F_ADDR and addr is NULL, or flags did
+	// not specify MPOL_F_ADDR and addr is not NULL." This is partially
+	// inaccurate: if flags specifies MPOL_F_ADDR,
+	// mm/mempolicy.c:do_get_mempolicy() doesn't special-case NULL; it will
+	// just (usually) fail to find a VMA at address 0 and return EFAULT.
+	if addr != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// "If flags is specified as 0, then information about the calling thread's
+	// default policy (as set by set_mempolicy(2)) is returned, in the buffers
+	// pointed to by mode and nodemask. ... If flags specifies MPOL_F_NODE, but
+	// not MPOL_F_ADDR, and the thread's current policy is MPOL_INTERLEAVE,
+	// then get_mempolicy() will return in the location pointed to by a
+	// non-NULL mode argument, the node ID of the next node that will be used
+	// for interleaving of internal kernel pages allocated on behalf of the
+	// thread."
+	policy, nodemaskVal := t.NumaPolicy()
+	if nodeFlag {
+		if policy&^linux.MPOL_MODE_FLAGS != linux.MPOL_INTERLEAVE {
+			return 0, nil, syserror.EINVAL
+		}
+		policy = 0 // maxNodes == 1
+	}
+	if mode != 0 {
+		if _, err := t.CopyOut(mode, policy); err != nil {
+			return 0, nil, err
+		}
+	}
+	if nodemask != 0 {
+		if err := copyOutNodemask(t, nodemask, maxnode, nodemaskVal); err != nil {
+			return 0, nil, err
+		}
+	}
+	return 0, nil, nil
+}
+
+// SetMempolicy implements the syscall set_mempolicy(2).
+func SetMempolicy(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	modeWithFlags := args[0].Int()
+	nodemask := args[1].Pointer()
+	maxnode := args[2].Uint()
+
+	modeWithFlags, nodemaskVal, err := copyInMempolicyNodemask(t, modeWithFlags, nodemask, maxnode)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	t.SetNumaPolicy(modeWithFlags, nodemaskVal)
+	return 0, nil, nil
+}
+
+// Mbind implements the syscall mbind(2).
+func Mbind(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	addr := args[0].Pointer()
+	length := args[1].Uint64()
+	mode := args[2].Int()
+	nodemask := args[3].Pointer()
+	maxnode := args[4].Uint()
+	flags := args[5].Uint()
+
+	if flags&^linux.MPOL_MF_VALID != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+	// "If MPOL_MF_MOVE_ALL is passed in flags ... [the] calling thread must be
+	// privileged (CAP_SYS_NICE) to use this flag." - mbind(2)
+	if flags&linux.MPOL_MF_MOVE_ALL != 0 && !t.HasCapability(linux.CAP_SYS_NICE) {
+		return 0, nil, syserror.EPERM
+	}
+
+	mode, nodemaskVal, err := copyInMempolicyNodemask(t, mode, nodemask, maxnode)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	// Since we claim to have only a single node, all flags can be ignored
+	// (since all pages must already be on that single node).
+	err = t.MemoryManager().SetNumaPolicy(addr, length, mode, nodemaskVal)
+	return 0, nil, err
+}
+
+func copyInMempolicyNodemask(t *kernel.Task, modeWithFlags int32, nodemask usermem.Addr, maxnode uint32) (int32, uint64, error) {
+	flags := modeWithFlags & linux.MPOL_MODE_FLAGS
+	mode := modeWithFlags &^ linux.MPOL_MODE_FLAGS
+	if flags == linux.MPOL_MODE_FLAGS {
+		// Can't specify both mode flags simultaneously.
+		return 0, 0, syserror.EINVAL
+	}
+	if mode < 0 || mode >= linux.MPOL_MAX {
+		// Must specify a valid mode.
+		return 0, 0, syserror.EINVAL
+	}
+
+	var nodemaskVal uint64
+	if nodemask != 0 {
+		var err error
+		nodemaskVal, err = copyInNodemask(t, nodemask, maxnode)
+		if err != nil {
+			return 0, 0, err
+		}
+	}
+
+	switch mode {
+	case linux.MPOL_DEFAULT:
+		// "nodemask must be specified as NULL." - set_mempolicy(2). This is inaccurate;
+		// Linux allows a nodemask to be specified, as long as it is empty.
+		if nodemaskVal != 0 {
+			return 0, 0, syserror.EINVAL
+		}
+	case linux.MPOL_BIND, linux.MPOL_INTERLEAVE:
+		// These require a non-empty nodemask.
+		if nodemaskVal == 0 {
+			return 0, 0, syserror.EINVAL
+		}
+	case linux.MPOL_PREFERRED:
+		// This permits an empty nodemask, as long as no flags are set.
+		if nodemaskVal == 0 && flags != 0 {
+			return 0, 0, syserror.EINVAL
+		}
+	case linux.MPOL_LOCAL:
+		// This requires an empty nodemask and no flags set ...
+		if nodemaskVal != 0 || flags != 0 {
+			return 0, 0, syserror.EINVAL
+		}
+		// ... and is implemented as MPOL_PREFERRED.
+		mode = linux.MPOL_PREFERRED
+	default:
+		// Unknown mode, which we should have rejected above.
+		panic(fmt.Sprintf("unknown mode: %v", mode))
+	}
+
+	return mode | flags, nodemaskVal, nil
+}
diff --git a/pkg/sentry/syscalls/linux/sys_mmap.go b/pkg/sentry/syscalls/linux/sys_mmap.go
index 64a6e639c..9926f0ac5 100644
--- a/pkg/sentry/syscalls/linux/sys_mmap.go
+++ b/pkg/sentry/syscalls/linux/sys_mmap.go
@@ -204,151 +204,6 @@ func Madvise(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysca
 	}
 }
 
-func copyOutIfNotNull(t *kernel.Task, ptr usermem.Addr, val interface{}) (int, error) {
-	if ptr != 0 {
-		return t.CopyOut(ptr, val)
-	}
-	return 0, nil
-}
-
-// GetMempolicy implements the syscall get_mempolicy(2).
-func GetMempolicy(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	mode := args[0].Pointer()
-	nodemask := args[1].Pointer()
-	maxnode := args[2].Uint()
-	addr := args[3].Pointer()
-	flags := args[4].Uint()
-
-	memsAllowed := flags&linux.MPOL_F_MEMS_ALLOWED != 0
-	nodeFlag := flags&linux.MPOL_F_NODE != 0
-	addrFlag := flags&linux.MPOL_F_ADDR != 0
-
-	// TODO(rahat): Once sysfs is implemented, report a single numa node in
-	// /sys/devices/system/node.
-	if nodemask != 0 && maxnode < 1 {
-		return 0, nil, syserror.EINVAL
-	}
-
-	// 'addr' provided iff 'addrFlag' set.
-	if addrFlag == (addr == 0) {
-		return 0, nil, syserror.EINVAL
-	}
-
-	// Default policy for the thread.
-	if flags == 0 {
-		policy, nodemaskVal := t.NumaPolicy()
-		if _, err := copyOutIfNotNull(t, mode, policy); err != nil {
-			return 0, nil, syserror.EFAULT
-		}
-		if _, err := copyOutIfNotNull(t, nodemask, nodemaskVal); err != nil {
-			return 0, nil, syserror.EFAULT
-		}
-		return 0, nil, nil
-	}
-
-	// Report all nodes available to caller.
-	if memsAllowed {
-		// MPOL_F_NODE and MPOL_F_ADDR not allowed with MPOL_F_MEMS_ALLOWED.
-		if nodeFlag || addrFlag {
-			return 0, nil, syserror.EINVAL
-		}
-
-		// Report a single numa node.
-		if _, err := copyOutIfNotNull(t, nodemask, uint32(0x1)); err != nil {
-			return 0, nil, syserror.EFAULT
-		}
-		return 0, nil, nil
-	}
-
-	if addrFlag {
-		if nodeFlag {
-			// Return the id for the node where 'addr' resides, via 'mode'.
-			//
-			// The real get_mempolicy(2) allocates the page referenced by 'addr'
-			// by simulating a read, if it is unallocated before the call. It
-			// then returns the node the page is allocated on through the mode
-			// pointer.
-			b := t.CopyScratchBuffer(1)
-			_, err := t.CopyInBytes(addr, b)
-			if err != nil {
-				return 0, nil, syserror.EFAULT
-			}
-			if _, err := copyOutIfNotNull(t, mode, int32(0)); err != nil {
-				return 0, nil, syserror.EFAULT
-			}
-		} else {
-			storedPolicy, _ := t.NumaPolicy()
-			// Return the policy governing the memory referenced by 'addr'.
-			if _, err := copyOutIfNotNull(t, mode, int32(storedPolicy)); err != nil {
-				return 0, nil, syserror.EFAULT
-			}
-		}
-		return 0, nil, nil
-	}
-
-	storedPolicy, _ := t.NumaPolicy()
-	if nodeFlag && (storedPolicy&^linux.MPOL_MODE_FLAGS == linux.MPOL_INTERLEAVE) {
-		// Policy for current thread is to interleave memory between
-		// nodes. Return the next node we'll allocate on. Since we only have a
-		// single node, this is always node 0.
-		if _, err := copyOutIfNotNull(t, mode, int32(0)); err != nil {
-			return 0, nil, syserror.EFAULT
-		}
-		return 0, nil, nil
-	}
-
-	return 0, nil, syserror.EINVAL
-}
-
-func allowedNodesMask() uint32 {
-	const maxNodes = 1
-	return ^uint32((1 << maxNodes) - 1)
-}
-
-// SetMempolicy implements the syscall set_mempolicy(2).
-func SetMempolicy(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
-	modeWithFlags := args[0].Int()
-	nodemask := args[1].Pointer()
-	maxnode := args[2].Uint()
-
-	if nodemask != 0 && maxnode < 1 {
-		return 0, nil, syserror.EINVAL
-	}
-
-	if modeWithFlags&linux.MPOL_MODE_FLAGS == linux.MPOL_MODE_FLAGS {
-		// Can't specify multiple modes simultaneously.
-		return 0, nil, syserror.EINVAL
-	}
-
-	mode := modeWithFlags &^ linux.MPOL_MODE_FLAGS
-	if mode < 0 || mode >= linux.MPOL_MAX {
-		// Must specify a valid mode.
-		return 0, nil, syserror.EINVAL
-	}
-
-	var nodemaskVal uint32
-	// Nodemask may be empty for some policy modes.
-	if nodemask != 0 && maxnode > 0 {
-		if _, err := t.CopyIn(nodemask, &nodemaskVal); err != nil {
-			return 0, nil, syserror.EFAULT
-		}
-	}
-
-	if (mode == linux.MPOL_INTERLEAVE || mode == linux.MPOL_BIND) && nodemaskVal == 0 {
-		// Mode requires a non-empty nodemask, but got an empty nodemask.
-		return 0, nil, syserror.EINVAL
-	}
-
-	if nodemaskVal&allowedNodesMask() != 0 {
-		// Invalid node specified.
-		return 0, nil, syserror.EINVAL
-	}
-
-	t.SetNumaPolicy(int32(modeWithFlags), nodemaskVal)
-
-	return 0, nil, nil
-}
-
 // Mincore implements the syscall mincore(2).
 func Mincore(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
 	addr := args[0].Pointer()
diff --git a/pkg/sentry/syscalls/linux/sys_prctl.go b/pkg/sentry/syscalls/linux/sys_prctl.go
index 117ae1a0e..1b7e5616b 100644
--- a/pkg/sentry/syscalls/linux/sys_prctl.go
+++ b/pkg/sentry/syscalls/linux/sys_prctl.go
@@ -15,6 +15,7 @@
 package linux
 
 import (
+	"fmt"
 	"syscall"
 
 	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
@@ -23,6 +24,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/kdefs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/mm"
 )
 
 // Prctl implements linux syscall prctl(2).
@@ -44,6 +46,33 @@ func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 		_, err := t.CopyOut(args[1].Pointer(), int32(t.ParentDeathSignal()))
 		return 0, nil, err
 
+	case linux.PR_GET_DUMPABLE:
+		d := t.MemoryManager().Dumpability()
+		switch d {
+		case mm.NotDumpable:
+			return linux.SUID_DUMP_DISABLE, nil, nil
+		case mm.UserDumpable:
+			return linux.SUID_DUMP_USER, nil, nil
+		case mm.RootDumpable:
+			return linux.SUID_DUMP_ROOT, nil, nil
+		default:
+			panic(fmt.Sprintf("Unknown dumpability %v", d))
+		}
+
+	case linux.PR_SET_DUMPABLE:
+		var d mm.Dumpability
+		switch args[1].Int() {
+		case linux.SUID_DUMP_DISABLE:
+			d = mm.NotDumpable
+		case linux.SUID_DUMP_USER:
+			d = mm.UserDumpable
+		default:
+			// N.B. Userspace may not pass SUID_DUMP_ROOT.
+			return 0, nil, syscall.EINVAL
+		}
+		t.MemoryManager().SetDumpability(d)
+		return 0, nil, nil
+
 	case linux.PR_GET_KEEPCAPS:
 		if t.Credentials().KeepCaps {
 			return 1, nil, nil
@@ -171,9 +200,7 @@ func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 		}
 		return 0, nil, t.DropBoundingCapability(cp)
 
-	case linux.PR_GET_DUMPABLE,
-		linux.PR_SET_DUMPABLE,
-		linux.PR_GET_TIMING,
+	case linux.PR_GET_TIMING,
 		linux.PR_SET_TIMING,
 		linux.PR_GET_TSC,
 		linux.PR_SET_TSC,
diff --git a/pkg/sentry/syscalls/linux/sys_socket.go b/pkg/sentry/syscalls/linux/sys_socket.go
index 8f4dbf3bc..31295a6a9 100644
--- a/pkg/sentry/syscalls/linux/sys_socket.go
+++ b/pkg/sentry/syscalls/linux/sys_socket.go
@@ -188,7 +188,7 @@ func Socket(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 	}
 
 	// Create the new socket.
-	s, e := socket.New(t, domain, transport.SockType(stype&0xf), protocol)
+	s, e := socket.New(t, domain, linux.SockType(stype&0xf), protocol)
 	if e != nil {
 		return 0, nil, e.ToError()
 	}
@@ -227,7 +227,7 @@ func SocketPair(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 	}
 
 	// Create the socket pair.
-	s1, s2, e := socket.Pair(t, domain, transport.SockType(stype&0xf), protocol)
+	s1, s2, e := socket.Pair(t, domain, linux.SockType(stype&0xf), protocol)
 	if e != nil {
 		return 0, nil, e.ToError()
 	}
diff --git a/pkg/sentry/time/seqatomic_parameters.go b/pkg/sentry/time/seqatomic_parameters.go
index f142c681a..54152a39a 100755
--- a/pkg/sentry/time/seqatomic_parameters.go
+++ b/pkg/sentry/time/seqatomic_parameters.go
@@ -2,10 +2,11 @@ package time
 
 import (
 	"fmt"
-	"gvisor.googlesource.com/gvisor/third_party/gvsync"
 	"reflect"
 	"strings"
 	"unsafe"
+
+	"gvisor.googlesource.com/gvisor/third_party/gvsync"
 )
 
 // SeqAtomicLoad returns a copy of *ptr, ensuring that the read does not race
diff --git a/pkg/sentry/usage/memory.go b/pkg/sentry/usage/memory.go
index c316f1597..9ed974ccb 100644
--- a/pkg/sentry/usage/memory.go
+++ b/pkg/sentry/usage/memory.go
@@ -22,7 +22,7 @@ import (
 	"syscall"
 
 	"gvisor.googlesource.com/gvisor/pkg/bits"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/memutil"
+	"gvisor.googlesource.com/gvisor/pkg/memutil"
 )
 
 // MemoryKind represents a type of memory used by the application.
diff --git a/pkg/sentry/usermem/usermem.go b/pkg/sentry/usermem/usermem.go
index 31e4d6ada..9dde327a2 100644
--- a/pkg/sentry/usermem/usermem.go
+++ b/pkg/sentry/usermem/usermem.go
@@ -222,9 +222,11 @@ func CopyObjectIn(ctx context.Context, uio IO, addr Addr, dst interface{}, opts
 	return int(r.Addr - addr), nil
 }
 
-// copyStringIncrement is the maximum number of bytes that are copied from
-// virtual memory at a time by CopyStringIn.
-const copyStringIncrement = 64
+// CopyStringIn tuning parameters, defined outside that function for tests.
+const (
+	copyStringIncrement     = 64
+	copyStringMaxInitBufLen = 256
+)
 
 // CopyStringIn copies a NUL-terminated string of unknown length from the
 // memory mapped at addr in uio and returns it as a string (not including the
@@ -234,31 +236,38 @@ const copyStringIncrement = 64
 //
 // Preconditions: As for IO.CopyFromUser. maxlen >= 0.
 func CopyStringIn(ctx context.Context, uio IO, addr Addr, maxlen int, opts IOOpts) (string, error) {
-	buf := make([]byte, maxlen)
+	initLen := maxlen
+	if initLen > copyStringMaxInitBufLen {
+		initLen = copyStringMaxInitBufLen
+	}
+	buf := make([]byte, initLen)
 	var done int
 	for done < maxlen {
-		start, ok := addr.AddLength(uint64(done))
-		if !ok {
-			// Last page of kernel memory. The application can't use this
-			// anyway.
-			return stringFromImmutableBytes(buf[:done]), syserror.EFAULT
-		}
 		// Read up to copyStringIncrement bytes at a time.
 		readlen := copyStringIncrement
 		if readlen > maxlen-done {
 			readlen = maxlen - done
 		}
-		end, ok := start.AddLength(uint64(readlen))
+		end, ok := addr.AddLength(uint64(readlen))
 		if !ok {
 			return stringFromImmutableBytes(buf[:done]), syserror.EFAULT
 		}
 		// Shorten the read to avoid crossing page boundaries, since faulting
 		// in a page unnecessarily is expensive. This also ensures that partial
 		// copies up to the end of application-mappable memory succeed.
-		if start.RoundDown() != end.RoundDown() {
+		if addr.RoundDown() != end.RoundDown() {
 			end = end.RoundDown()
+			readlen = int(end - addr)
+		}
+		// Ensure that our buffer is large enough to accommodate the read.
+		if done+readlen > len(buf) {
+			newBufLen := len(buf) * 2
+			if newBufLen > maxlen {
+				newBufLen = maxlen
+			}
+			buf = append(buf, make([]byte, newBufLen-len(buf))...)
 		}
-		n, err := uio.CopyIn(ctx, start, buf[done:done+int(end-start)], opts)
+		n, err := uio.CopyIn(ctx, addr, buf[done:done+readlen], opts)
 		// Look for the terminating zero byte, which may have occurred before
 		// hitting err.
 		for i, c := range buf[done : done+n] {
@@ -270,6 +279,7 @@ func CopyStringIn(ctx context.Context, uio IO, addr Addr, maxlen int, opts IOOpt
 		if err != nil {
 			return stringFromImmutableBytes(buf[:done]), err
 		}
+		addr = end
 	}
 	return stringFromImmutableBytes(buf), syserror.ENAMETOOLONG
 }
diff --git a/pkg/tcpip/link/fdbased/endpoint.go b/pkg/tcpip/link/fdbased/endpoint.go
index 1f889c2a0..b88e2e7bf 100644
--- a/pkg/tcpip/link/fdbased/endpoint.go
+++ b/pkg/tcpip/link/fdbased/endpoint.go
@@ -21,12 +21,29 @@
 // FD based endpoints can be used in the networking stack by calling New() to
 // create a new endpoint, and then passing it as an argument to
 // Stack.CreateNIC().
+//
+// FD based endpoints can use more than one file descriptor to read incoming
+// packets. If there are more than one FDs specified and the underlying FD is an
+// AF_PACKET then the endpoint will enable FANOUT mode on the socket so that the
+// host kernel will consistently hash the packets to the sockets. This ensures
+// that packets for the same TCP streams are not reordered.
+//
+// Similarly if more than one FD's are specified where the underlying FD is not
+// AF_PACKET then it's the caller's responsibility to ensure that all inbound
+// packets on the descriptors are consistently 5 tuple hashed to one of the
+// descriptors to prevent TCP reordering.
+//
+// Since netstack today does not compute 5 tuple hashes for outgoing packets we
+// only use the first FD to write outbound packets. Once 5 tuple hashes for
+// all outbound packets are available we will make use of all underlying FD's to
+// write outbound packets.
 package fdbased
 
 import (
 	"fmt"
 	"syscall"
 
+	"golang.org/x/sys/unix"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
 	"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
@@ -65,8 +82,10 @@ const (
 )
 
 type endpoint struct {
-	// fd is the file descriptor used to send and receive packets.
-	fd int
+	// fds is the set of file descriptors each identifying one inbound/outbound
+	// channel. The endpoint will dispatch from all inbound channels as well as
+	// hash outbound packets to specific channels based on the packet hash.
+	fds []int
 
 	// mtu (maximum transmission unit) is the maximum size of a packet.
 	mtu uint32
@@ -85,8 +104,8 @@ type endpoint struct {
 	// its end of the communication pipe.
 	closed func(*tcpip.Error)
 
-	inboundDispatcher linkDispatcher
-	dispatcher        stack.NetworkDispatcher
+	inboundDispatchers []linkDispatcher
+	dispatcher         stack.NetworkDispatcher
 
 	// packetDispatchMode controls the packet dispatcher used by this
 	// endpoint.
@@ -99,17 +118,47 @@ type endpoint struct {
 
 // Options specify the details about the fd-based endpoint to be created.
 type Options struct {
-	FD                 int
-	MTU                uint32
-	EthernetHeader     bool
-	ClosedFunc         func(*tcpip.Error)
-	Address            tcpip.LinkAddress
-	SaveRestore        bool
-	DisconnectOk       bool
-	GSOMaxSize         uint32
+	// FDs is a set of FDs used to read/write packets.
+	FDs []int
+
+	// MTU is the mtu to use for this endpoint.
+	MTU uint32
+
+	// EthernetHeader if true, indicates that the endpoint should read/write
+	// ethernet frames instead of IP packets.
+	EthernetHeader bool
+
+	// ClosedFunc is a function to be called when an endpoint's peer (if
+	// any) closes its end of the communication pipe.
+	ClosedFunc func(*tcpip.Error)
+
+	// Address is the link address for this endpoint. Only used if
+	// EthernetHeader is true.
+	Address tcpip.LinkAddress
+
+	// SaveRestore if true, indicates that this NIC capability set should
+	// include CapabilitySaveRestore
+	SaveRestore bool
+
+	// DisconnectOk if true, indicates that this NIC capability set should
+	// include CapabilityDisconnectOk.
+	DisconnectOk bool
+
+	// GSOMaxSize is the maximum GSO packet size. It is zero if GSO is
+	// disabled.
+	GSOMaxSize uint32
+
+	// PacketDispatchMode specifies the type of inbound dispatcher to be
+	// used for this endpoint.
 	PacketDispatchMode PacketDispatchMode
-	TXChecksumOffload  bool
-	RXChecksumOffload  bool
+
+	// TXChecksumOffload if true, indicates that this endpoints capability
+	// set should include CapabilityTXChecksumOffload.
+	TXChecksumOffload bool
+
+	// RXChecksumOffload if true, indicates that this endpoints capability
+	// set should include CapabilityRXChecksumOffload.
+	RXChecksumOffload bool
 }
 
 // New creates a new fd-based endpoint.
@@ -117,10 +166,6 @@ type Options struct {
 // Makes fd non-blocking, but does not take ownership of fd, which must remain
 // open for the lifetime of the returned endpoint.
 func New(opts *Options) (tcpip.LinkEndpointID, error) {
-	if err := syscall.SetNonblock(opts.FD, true); err != nil {
-		return 0, fmt.Errorf("syscall.SetNonblock(%v) failed: %v", opts.FD, err)
-	}
-
 	caps := stack.LinkEndpointCapabilities(0)
 	if opts.RXChecksumOffload {
 		caps |= stack.CapabilityRXChecksumOffload
@@ -144,8 +189,12 @@ func New(opts *Options) (tcpip.LinkEndpointID, error) {
 		caps |= stack.CapabilityDisconnectOk
 	}
 
+	if len(opts.FDs) == 0 {
+		return 0, fmt.Errorf("opts.FD is empty, at least one FD must be specified")
+	}
+
 	e := &endpoint{
-		fd:                 opts.FD,
+		fds:                opts.FDs,
 		mtu:                opts.MTU,
 		caps:               caps,
 		closed:             opts.ClosedFunc,
@@ -154,46 +203,71 @@ func New(opts *Options) (tcpip.LinkEndpointID, error) {
 		packetDispatchMode: opts.PacketDispatchMode,
 	}
 
-	isSocket, err := isSocketFD(e.fd)
-	if err != nil {
-		return 0, err
-	}
-	if isSocket {
-		if opts.GSOMaxSize != 0 {
-			e.caps |= stack.CapabilityGSO
-			e.gsoMaxSize = opts.GSOMaxSize
+	// Create per channel dispatchers.
+	for i := 0; i < len(e.fds); i++ {
+		fd := e.fds[i]
+		if err := syscall.SetNonblock(fd, true); err != nil {
+			return 0, fmt.Errorf("syscall.SetNonblock(%v) failed: %v", fd, err)
 		}
-	}
-	e.inboundDispatcher, err = createInboundDispatcher(e, isSocket)
-	if err != nil {
-		return 0, fmt.Errorf("createInboundDispatcher(...) = %v", err)
+
+		isSocket, err := isSocketFD(fd)
+		if err != nil {
+			return 0, err
+		}
+		if isSocket {
+			if opts.GSOMaxSize != 0 {
+				e.caps |= stack.CapabilityGSO
+				e.gsoMaxSize = opts.GSOMaxSize
+			}
+		}
+		inboundDispatcher, err := createInboundDispatcher(e, fd, isSocket)
+		if err != nil {
+			return 0, fmt.Errorf("createInboundDispatcher(...) = %v", err)
+		}
+		e.inboundDispatchers = append(e.inboundDispatchers, inboundDispatcher)
 	}
 
 	return stack.RegisterLinkEndpoint(e), nil
 }
 
-func createInboundDispatcher(e *endpoint, isSocket bool) (linkDispatcher, error) {
+func createInboundDispatcher(e *endpoint, fd int, isSocket bool) (linkDispatcher, error) {
 	// By default use the readv() dispatcher as it works with all kinds of
 	// FDs (tap/tun/unix domain sockets and af_packet).
-	inboundDispatcher, err := newReadVDispatcher(e.fd, e)
+	inboundDispatcher, err := newReadVDispatcher(fd, e)
 	if err != nil {
-		return nil, fmt.Errorf("newReadVDispatcher(%d, %+v) = %v", e.fd, e, err)
+		return nil, fmt.Errorf("newReadVDispatcher(%d, %+v) = %v", fd, e, err)
 	}
 
 	if isSocket {
+		sa, err := unix.Getsockname(fd)
+		if err != nil {
+			return nil, fmt.Errorf("unix.Getsockname(%d) = %v", fd, err)
+		}
+		switch sa.(type) {
+		case *unix.SockaddrLinklayer:
+			// enable PACKET_FANOUT mode is the underlying socket is
+			// of type AF_PACKET.
+			const fanoutID = 1
+			const fanoutType = 0x8000 // PACKET_FANOUT_HASH | PACKET_FANOUT_FLAG_DEFRAG
+			fanoutArg := fanoutID | fanoutType<<16
+			if err := syscall.SetsockoptInt(fd, syscall.SOL_PACKET, unix.PACKET_FANOUT, fanoutArg); err != nil {
+				return nil, fmt.Errorf("failed to enable PACKET_FANOUT option: %v", err)
+			}
+		}
+
 		switch e.packetDispatchMode {
 		case PacketMMap:
-			inboundDispatcher, err = newPacketMMapDispatcher(e.fd, e)
+			inboundDispatcher, err = newPacketMMapDispatcher(fd, e)
 			if err != nil {
-				return nil, fmt.Errorf("newPacketMMapDispatcher(%d, %+v) = %v", e.fd, e, err)
+				return nil, fmt.Errorf("newPacketMMapDispatcher(%d, %+v) = %v", fd, e, err)
 			}
 		case RecvMMsg:
 			// If the provided FD is a socket then we optimize
 			// packet reads by using recvmmsg() instead of read() to
 			// read packets in a batch.
-			inboundDispatcher, err = newRecvMMsgDispatcher(e.fd, e)
+			inboundDispatcher, err = newRecvMMsgDispatcher(fd, e)
 			if err != nil {
-				return nil, fmt.Errorf("newRecvMMsgDispatcher(%d, %+v) = %v", e.fd, e, err)
+				return nil, fmt.Errorf("newRecvMMsgDispatcher(%d, %+v) = %v", fd, e, err)
 			}
 		}
 	}
@@ -215,7 +289,9 @@ func (e *endpoint) Attach(dispatcher stack.NetworkDispatcher) {
 	// Link endpoints are not savable. When transportation endpoints are
 	// saved, they stop sending outgoing packets and all incoming packets
 	// are rejected.
-	go e.dispatchLoop() // S/R-SAFE: See above.
+	for i := range e.inboundDispatchers {
+		go e.dispatchLoop(e.inboundDispatchers[i]) // S/R-SAFE: See above.
+	}
 }
 
 // IsAttached implements stack.LinkEndpoint.IsAttached.
@@ -305,26 +381,26 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prepen
 			}
 		}
 
-		return rawfile.NonBlockingWrite3(e.fd, vnetHdrBuf, hdr.View(), payload.ToView())
+		return rawfile.NonBlockingWrite3(e.fds[0], vnetHdrBuf, hdr.View(), payload.ToView())
 	}
 
 	if payload.Size() == 0 {
-		return rawfile.NonBlockingWrite(e.fd, hdr.View())
+		return rawfile.NonBlockingWrite(e.fds[0], hdr.View())
 	}
 
-	return rawfile.NonBlockingWrite3(e.fd, hdr.View(), payload.ToView(), nil)
+	return rawfile.NonBlockingWrite3(e.fds[0], hdr.View(), payload.ToView(), nil)
 }
 
 // WriteRawPacket writes a raw packet directly to the file descriptor.
 func (e *endpoint) WriteRawPacket(dest tcpip.Address, packet []byte) *tcpip.Error {
-	return rawfile.NonBlockingWrite(e.fd, packet)
+	return rawfile.NonBlockingWrite(e.fds[0], packet)
 }
 
 // dispatchLoop reads packets from the file descriptor in a loop and dispatches
 // them to the network stack.
-func (e *endpoint) dispatchLoop() *tcpip.Error {
+func (e *endpoint) dispatchLoop(inboundDispatcher linkDispatcher) *tcpip.Error {
 	for {
-		cont, err := e.inboundDispatcher.dispatch()
+		cont, err := inboundDispatcher.dispatch()
 		if err != nil || !cont {
 			if e.closed != nil {
 				e.closed(err)
@@ -363,7 +439,7 @@ func NewInjectable(fd int, mtu uint32, capabilities stack.LinkEndpointCapabiliti
 	syscall.SetNonblock(fd, true)
 
 	e := &InjectableEndpoint{endpoint: endpoint{
-		fd:   fd,
+		fds:  []int{fd},
 		mtu:  mtu,
 		caps: capabilities,
 	}}
diff --git a/pkg/tcpip/link/sniffer/sniffer.go b/pkg/tcpip/link/sniffer/sniffer.go
index fccabd554..98581e50e 100644
--- a/pkg/tcpip/link/sniffer/sniffer.go
+++ b/pkg/tcpip/link/sniffer/sniffer.go
@@ -118,7 +118,7 @@ func NewWithFile(lower tcpip.LinkEndpointID, file *os.File, snapLen uint32) (tcp
 // logs the packet before forwarding to the actual dispatcher.
 func (e *endpoint) DeliverNetworkPacket(linkEP stack.LinkEndpoint, remote, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, vv buffer.VectorisedView) {
 	if atomic.LoadUint32(&LogPackets) == 1 && e.file == nil {
-		logPacket("recv", protocol, vv.First())
+		logPacket("recv", protocol, vv.First(), nil)
 	}
 	if e.file != nil && atomic.LoadUint32(&LogPacketsToFile) == 1 {
 		vs := vv.Views()
@@ -198,7 +198,7 @@ func (e *endpoint) GSOMaxSize() uint32 {
 // the request to the lower endpoint.
 func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
 	if atomic.LoadUint32(&LogPackets) == 1 && e.file == nil {
-		logPacket("send", protocol, hdr.View())
+		logPacket("send", protocol, hdr.View(), gso)
 	}
 	if e.file != nil && atomic.LoadUint32(&LogPacketsToFile) == 1 {
 		hdrBuf := hdr.View()
@@ -240,7 +240,7 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prepen
 	return e.lower.WritePacket(r, gso, hdr, payload, protocol)
 }
 
-func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, b buffer.View) {
+func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, b buffer.View, gso *stack.GSO) {
 	// Figure out the network layer info.
 	var transProto uint8
 	src := tcpip.Address("unknown")
@@ -404,5 +404,9 @@ func logPacket(prefix string, protocol tcpip.NetworkProtocolNumber, b buffer.Vie
 		return
 	}
 
+	if gso != nil {
+		details += fmt.Sprintf(" gso: %+v", gso)
+	}
+
 	log.Infof("%s %s %v:%v -> %v:%v len:%d id:%04x %s", prefix, transName, src, srcPort, dst, dstPort, size, id, details)
 }
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index da07a39e5..44b1d5b9b 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -215,7 +215,9 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prepen
 		views[0] = hdr.View()
 		views = append(views, payload.Views()...)
 		vv := buffer.NewVectorisedView(len(views[0])+payload.Size(), views)
-		e.HandlePacket(r, vv)
+		loopedR := r.MakeLoopedRoute()
+		e.HandlePacket(&loopedR, vv)
+		loopedR.Release()
 	}
 	if loop&stack.PacketOut == 0 {
 		return nil
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 4b8cd496b..bcae98e1f 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -108,7 +108,9 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prepen
 		views[0] = hdr.View()
 		views = append(views, payload.Views()...)
 		vv := buffer.NewVectorisedView(len(views[0])+payload.Size(), views)
-		e.HandlePacket(r, vv)
+		loopedR := r.MakeLoopedRoute()
+		e.HandlePacket(&loopedR, vv)
+		loopedR.Release()
 	}
 	if loop&stack.PacketOut == 0 {
 		return nil
diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go
index 3d4c282a9..55ed02479 100644
--- a/pkg/tcpip/stack/route.go
+++ b/pkg/tcpip/stack/route.go
@@ -187,3 +187,13 @@ func (r *Route) Clone() Route {
 	r.ref.incRef()
 	return *r
 }
+
+// MakeLoopedRoute duplicates the given route and tweaks it in case of multicast.
+func (r *Route) MakeLoopedRoute() Route {
+	l := r.Clone()
+	if header.IsV4MulticastAddress(r.RemoteAddress) || header.IsV6MulticastAddress(r.RemoteAddress) {
+		l.RemoteAddress, l.LocalAddress = l.LocalAddress, l.RemoteAddress
+		l.RemoteLinkAddress = l.LocalLinkAddress
+	}
+	return l
+}
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index f9886c6e4..85ef014d0 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -377,6 +377,10 @@ type Endpoint interface {
 	// GetSockOpt gets a socket option. opt should be a pointer to one of the
 	// *Option types.
 	GetSockOpt(opt interface{}) *Error
+
+	// State returns a socket's lifecycle state. The returned value is
+	// protocol-specific and is primarily used for diagnostics.
+	State() uint32
 }
 
 // WriteOptions contains options for Endpoint.Write.
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index e2b90ef10..b8005093a 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -708,3 +708,9 @@ func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, vv
 // HandleControlPacket implements stack.TransportEndpoint.HandleControlPacket.
 func (e *endpoint) HandleControlPacket(id stack.TransportEndpointID, typ stack.ControlType, extra uint32, vv buffer.VectorisedView) {
 }
+
+// State implements tcpip.Endpoint.State. The ICMP endpoint currently doesn't
+// expose internal socket state.
+func (e *endpoint) State() uint32 {
+	return 0
+}
diff --git a/pkg/tcpip/transport/raw/endpoint.go b/pkg/tcpip/transport/raw/endpoint.go
index 1daf5823f..e4ff50c91 100644
--- a/pkg/tcpip/transport/raw/endpoint.go
+++ b/pkg/tcpip/transport/raw/endpoint.go
@@ -519,3 +519,8 @@ func (ep *endpoint) HandlePacket(route *stack.Route, netHeader buffer.View, vv b
 		ep.waiterQueue.Notify(waiter.EventIn)
 	}
 }
+
+// State implements socket.Socket.State.
+func (ep *endpoint) State() uint32 {
+	return 0
+}
diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go
index 31e365ae5..a32e20b06 100644
--- a/pkg/tcpip/transport/tcp/accept.go
+++ b/pkg/tcpip/transport/tcp/accept.go
@@ -226,7 +226,6 @@ func (l *listenContext) createConnectingEndpoint(s *segment, iss seqnum.Value, i
 	}
 
 	n.isRegistered = true
-	n.state = stateConnecting
 
 	// Create sender and receiver.
 	//
@@ -258,8 +257,9 @@ func (l *listenContext) createEndpointAndPerformHandshake(s *segment, opts *head
 		ep.Close()
 		return nil, err
 	}
-
-	ep.state = stateConnected
+	ep.mu.Lock()
+	ep.state = StateEstablished
+	ep.mu.Unlock()
 
 	// Update the receive window scaling. We can't do it before the
 	// handshake because it's possible that the peer doesn't support window
@@ -276,7 +276,7 @@ func (e *endpoint) deliverAccepted(n *endpoint) {
 	e.mu.RLock()
 	state := e.state
 	e.mu.RUnlock()
-	if state == stateListen {
+	if state == StateListen {
 		e.acceptedChan <- n
 		e.waiterQueue.Notify(waiter.EventIn)
 	} else {
@@ -406,7 +406,7 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) {
 		n.tsOffset = 0
 
 		// Switch state to connected.
-		n.state = stateConnected
+		n.state = StateEstablished
 
 		// Do the delivery in a separate goroutine so
 		// that we don't block the listen loop in case
@@ -429,7 +429,7 @@ func (e *endpoint) protocolListenLoop(rcvWnd seqnum.Size) *tcpip.Error {
 		// handleSynSegment() from attempting to queue new connections
 		// to the endpoint.
 		e.mu.Lock()
-		e.state = stateClosed
+		e.state = StateClose
 
 		// Do cleanup if needed.
 		e.completeWorkerLocked()
diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index 2aed6f286..0ad7bfb38 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -151,6 +151,9 @@ func (h *handshake) resetToSynRcvd(iss seqnum.Value, irs seqnum.Value, opts *hea
 	h.mss = opts.MSS
 	h.sndWndScale = opts.WS
 	h.listenEP = listenEP
+	h.ep.mu.Lock()
+	h.ep.state = StateSynRecv
+	h.ep.mu.Unlock()
 }
 
 // checkAck checks if the ACK number, if present, of a segment received during
@@ -219,6 +222,9 @@ func (h *handshake) synSentState(s *segment) *tcpip.Error {
 	// but resend our own SYN and wait for it to be acknowledged in the
 	// SYN-RCVD state.
 	h.state = handshakeSynRcvd
+	h.ep.mu.Lock()
+	h.ep.state = StateSynRecv
+	h.ep.mu.Unlock()
 	synOpts := header.TCPSynOptions{
 		WS:    h.rcvWndScale,
 		TS:    rcvSynOpts.TS,
@@ -284,14 +290,19 @@ func (h *handshake) synRcvdState(s *segment) *tcpip.Error {
 		// listenContext is also used by a tcp.Forwarder and in that
 		// context we do not have a listening endpoint to check the
 		// backlog. So skip this check if listenEP is nil.
-		if h.listenEP != nil && len(h.listenEP.acceptedChan) == cap(h.listenEP.acceptedChan) {
-			// If there is no space in the accept queue to accept
-			// this endpoint then silently drop this ACK. The peer
-			// will anyway resend the ack and we can complete the
-			// connection the next time it's retransmitted.
-			h.ep.stack.Stats().TCP.ListenOverflowAckDrop.Increment()
-			h.ep.stack.Stats().DroppedPackets.Increment()
-			return nil
+		if h.listenEP != nil {
+			h.listenEP.mu.Lock()
+			if len(h.listenEP.acceptedChan) == cap(h.listenEP.acceptedChan) {
+				h.listenEP.mu.Unlock()
+				// If there is no space in the accept queue to accept
+				// this endpoint then silently drop this ACK. The peer
+				// will anyway resend the ack and we can complete the
+				// connection the next time it's retransmitted.
+				h.ep.stack.Stats().TCP.ListenOverflowAckDrop.Increment()
+				h.ep.stack.Stats().DroppedPackets.Increment()
+				return nil
+			}
+			h.listenEP.mu.Unlock()
 		}
 		// If the timestamp option is negotiated and the segment does
 		// not carry a timestamp option then the segment must be dropped
@@ -663,7 +674,7 @@ func (e *endpoint) makeOptions(sackBlocks []header.SACKBlock) []byte {
 // sendRaw sends a TCP segment to the endpoint's peer.
 func (e *endpoint) sendRaw(data buffer.VectorisedView, flags byte, seq, ack seqnum.Value, rcvWnd seqnum.Size) *tcpip.Error {
 	var sackBlocks []header.SACKBlock
-	if e.state == stateConnected && e.rcv.pendingBufSize > 0 && (flags&header.TCPFlagAck != 0) {
+	if e.state == StateEstablished && e.rcv.pendingBufSize > 0 && (flags&header.TCPFlagAck != 0) {
 		sackBlocks = e.sack.Blocks[:e.sack.NumBlocks]
 	}
 	options := e.makeOptions(sackBlocks)
@@ -714,8 +725,7 @@ func (e *endpoint) handleClose() *tcpip.Error {
 // protocol goroutine.
 func (e *endpoint) resetConnectionLocked(err *tcpip.Error) {
 	e.sendRaw(buffer.VectorisedView{}, header.TCPFlagAck|header.TCPFlagRst, e.snd.sndUna, e.rcv.rcvNxt, 0)
-
-	e.state = stateError
+	e.state = StateError
 	e.hardError = err
 }
 
@@ -871,14 +881,19 @@ func (e *endpoint) protocolMainLoop(handshake bool) *tcpip.Error {
 		// handshake, and then inform potential waiters about its
 		// completion.
 		h := newHandshake(e, seqnum.Size(e.receiveBufferAvailable()))
+		e.mu.Lock()
+		h.ep.state = StateSynSent
+		e.mu.Unlock()
+
 		if err := h.execute(); err != nil {
 			e.lastErrorMu.Lock()
 			e.lastError = err
 			e.lastErrorMu.Unlock()
 
 			e.mu.Lock()
-			e.state = stateError
+			e.state = StateError
 			e.hardError = err
+
 			// Lock released below.
 			epilogue()
 
@@ -900,7 +915,7 @@ func (e *endpoint) protocolMainLoop(handshake bool) *tcpip.Error {
 
 	// Tell waiters that the endpoint is connected and writable.
 	e.mu.Lock()
-	e.state = stateConnected
+	e.state = StateEstablished
 	drained := e.drainDone != nil
 	e.mu.Unlock()
 	if drained {
@@ -1000,7 +1015,7 @@ func (e *endpoint) protocolMainLoop(handshake bool) *tcpip.Error {
 							return err
 						}
 					}
-					if e.state != stateError {
+					if e.state != StateError {
 						close(e.drainDone)
 						<-e.undrain
 					}
@@ -1056,8 +1071,8 @@ func (e *endpoint) protocolMainLoop(handshake bool) *tcpip.Error {
 
 	// Mark endpoint as closed.
 	e.mu.Lock()
-	if e.state != stateError {
-		e.state = stateClosed
+	if e.state != StateError {
+		e.state = StateClose
 	}
 	// Lock released below.
 	epilogue()
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index fd697402e..23422ca5e 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -32,18 +32,81 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/waiter"
 )
 
-type endpointState int
+// EndpointState represents the state of a TCP endpoint.
+type EndpointState uint32
 
+// Endpoint states. Note that are represented in a netstack-specific manner and
+// may not be meaningful externally. Specifically, they need to be translated to
+// Linux's representation for these states if presented to userspace.
 const (
-	stateInitial endpointState = iota
-	stateBound
-	stateListen
-	stateConnecting
-	stateConnected
-	stateClosed
-	stateError
+	// Endpoint states internal to netstack. These map to the TCP state CLOSED.
+	StateInitial EndpointState = iota
+	StateBound
+	StateConnecting // Connect() called, but the initial SYN hasn't been sent.
+	StateError
+
+	// TCP protocol states.
+	StateEstablished
+	StateSynSent
+	StateSynRecv
+	StateFinWait1
+	StateFinWait2
+	StateTimeWait
+	StateClose
+	StateCloseWait
+	StateLastAck
+	StateListen
+	StateClosing
 )
 
+// connected is the set of states where an endpoint is connected to a peer.
+func (s EndpointState) connected() bool {
+	switch s {
+	case StateEstablished, StateFinWait1, StateFinWait2, StateTimeWait, StateCloseWait, StateLastAck, StateClosing:
+		return true
+	default:
+		return false
+	}
+}
+
+// String implements fmt.Stringer.String.
+func (s EndpointState) String() string {
+	switch s {
+	case StateInitial:
+		return "INITIAL"
+	case StateBound:
+		return "BOUND"
+	case StateConnecting:
+		return "CONNECTING"
+	case StateError:
+		return "ERROR"
+	case StateEstablished:
+		return "ESTABLISHED"
+	case StateSynSent:
+		return "SYN-SENT"
+	case StateSynRecv:
+		return "SYN-RCVD"
+	case StateFinWait1:
+		return "FIN-WAIT1"
+	case StateFinWait2:
+		return "FIN-WAIT2"
+	case StateTimeWait:
+		return "TIME-WAIT"
+	case StateClose:
+		return "CLOSED"
+	case StateCloseWait:
+		return "CLOSE-WAIT"
+	case StateLastAck:
+		return "LAST-ACK"
+	case StateListen:
+		return "LISTEN"
+	case StateClosing:
+		return "CLOSING"
+	default:
+		panic("unreachable")
+	}
+}
+
 // Reasons for notifying the protocol goroutine.
 const (
 	notifyNonZeroReceiveWindow = 1 << iota
@@ -108,10 +171,14 @@ type endpoint struct {
 	rcvBufUsed int
 
 	// The following fields are protected by the mutex.
-	mu                sync.RWMutex `state:"nosave"`
-	id                stack.TransportEndpointID
-	state             endpointState `state:".(endpointState)"`
-	isPortReserved    bool          `state:"manual"`
+	mu sync.RWMutex `state:"nosave"`
+	id stack.TransportEndpointID
+
+	// state             endpointState `state:".(endpointState)"`
+	// pState            ProtocolState
+	state EndpointState `state:".(EndpointState)"`
+
+	isPortReserved    bool `state:"manual"`
 	isRegistered      bool
 	boundNICID        tcpip.NICID `state:"manual"`
 	route             stack.Route `state:"manual"`
@@ -304,6 +371,7 @@ func newEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, waite
 		stack:       stack,
 		netProto:    netProto,
 		waiterQueue: waiterQueue,
+		state:       StateInitial,
 		rcvBufSize:  DefaultBufferSize,
 		sndBufSize:  DefaultBufferSize,
 		sndMTU:      int(math.MaxInt32),
@@ -351,14 +419,14 @@ func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 	defer e.mu.RUnlock()
 
 	switch e.state {
-	case stateInitial, stateBound, stateConnecting:
+	case StateInitial, StateBound, StateConnecting, StateSynSent, StateSynRecv:
 		// Ready for nothing.
 
-	case stateClosed, stateError:
+	case StateClose, StateError:
 		// Ready for anything.
 		result = mask
 
-	case stateListen:
+	case StateListen:
 		// Check if there's anything in the accepted channel.
 		if (mask & waiter.EventIn) != 0 {
 			if len(e.acceptedChan) > 0 {
@@ -366,7 +434,7 @@ func (e *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 			}
 		}
 
-	case stateConnected:
+	case StateEstablished, StateFinWait1, StateFinWait2, StateTimeWait, StateCloseWait, StateLastAck, StateClosing:
 		// Determine if the endpoint is writable if requested.
 		if (mask & waiter.EventOut) != 0 {
 			e.sndBufMu.Lock()
@@ -427,7 +495,7 @@ func (e *endpoint) Close() {
 	// are immediately available for reuse after Close() is called. If also
 	// registered, we unregister as well otherwise the next user would fail
 	// in Listen() when trying to register.
-	if e.state == stateListen && e.isPortReserved {
+	if e.state == StateListen && e.isPortReserved {
 		if e.isRegistered {
 			e.stack.UnregisterTransportEndpoint(e.boundNICID, e.effectiveNetProtos, ProtocolNumber, e.id, e)
 			e.isRegistered = false
@@ -487,15 +555,15 @@ func (e *endpoint) Read(*tcpip.FullAddress) (buffer.View, tcpip.ControlMessages,
 	e.mu.RLock()
 	// The endpoint can be read if it's connected, or if it's already closed
 	// but has some pending unread data. Also note that a RST being received
-	// would cause the state to become stateError so we should allow the
+	// would cause the state to become StateError so we should allow the
 	// reads to proceed before returning a ECONNRESET.
 	e.rcvListMu.Lock()
 	bufUsed := e.rcvBufUsed
-	if s := e.state; s != stateConnected && s != stateClosed && bufUsed == 0 {
+	if s := e.state; !s.connected() && s != StateClose && bufUsed == 0 {
 		e.rcvListMu.Unlock()
 		he := e.hardError
 		e.mu.RUnlock()
-		if s == stateError {
+		if s == StateError {
 			return buffer.View{}, tcpip.ControlMessages{}, he
 		}
 		return buffer.View{}, tcpip.ControlMessages{}, tcpip.ErrInvalidEndpointState
@@ -511,7 +579,7 @@ func (e *endpoint) Read(*tcpip.FullAddress) (buffer.View, tcpip.ControlMessages,
 
 func (e *endpoint) readLocked() (buffer.View, *tcpip.Error) {
 	if e.rcvBufUsed == 0 {
-		if e.rcvClosed || e.state != stateConnected {
+		if e.rcvClosed || !e.state.connected() {
 			return buffer.View{}, tcpip.ErrClosedForReceive
 		}
 		return buffer.View{}, tcpip.ErrWouldBlock
@@ -547,9 +615,9 @@ func (e *endpoint) Write(p tcpip.Payload, opts tcpip.WriteOptions) (uintptr, <-c
 	defer e.mu.RUnlock()
 
 	// The endpoint cannot be written to if it's not connected.
-	if e.state != stateConnected {
+	if !e.state.connected() {
 		switch e.state {
-		case stateError:
+		case StateError:
 			return 0, nil, e.hardError
 		default:
 			return 0, nil, tcpip.ErrClosedForSend
@@ -612,8 +680,8 @@ func (e *endpoint) Peek(vec [][]byte) (uintptr, tcpip.ControlMessages, *tcpip.Er
 
 	// The endpoint can be read if it's connected, or if it's already closed
 	// but has some pending unread data.
-	if s := e.state; s != stateConnected && s != stateClosed {
-		if s == stateError {
+	if s := e.state; !s.connected() && s != StateClose {
+		if s == StateError {
 			return 0, tcpip.ControlMessages{}, e.hardError
 		}
 		return 0, tcpip.ControlMessages{}, tcpip.ErrInvalidEndpointState
@@ -623,7 +691,7 @@ func (e *endpoint) Peek(vec [][]byte) (uintptr, tcpip.ControlMessages, *tcpip.Er
 	defer e.rcvListMu.Unlock()
 
 	if e.rcvBufUsed == 0 {
-		if e.rcvClosed || e.state != stateConnected {
+		if e.rcvClosed || !e.state.connected() {
 			return 0, tcpip.ControlMessages{}, tcpip.ErrClosedForReceive
 		}
 		return 0, tcpip.ControlMessages{}, tcpip.ErrWouldBlock
@@ -789,7 +857,7 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 		defer e.mu.Unlock()
 
 		// We only allow this to be set when we're in the initial state.
-		if e.state != stateInitial {
+		if e.state != StateInitial {
 			return tcpip.ErrInvalidEndpointState
 		}
 
@@ -841,7 +909,7 @@ func (e *endpoint) readyReceiveSize() (int, *tcpip.Error) {
 	defer e.mu.RUnlock()
 
 	// The endpoint cannot be in listen state.
-	if e.state == stateListen {
+	if e.state == StateListen {
 		return 0, tcpip.ErrInvalidEndpointState
 	}
 
@@ -1057,7 +1125,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) (er
 
 	nicid := addr.NIC
 	switch e.state {
-	case stateBound:
+	case StateBound:
 		// If we're already bound to a NIC but the caller is requesting
 		// that we use a different one now, we cannot proceed.
 		if e.boundNICID == 0 {
@@ -1070,16 +1138,16 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) (er
 
 		nicid = e.boundNICID
 
-	case stateInitial:
-		// Nothing to do. We'll eventually fill-in the gaps in the ID
-		// (if any) when we find a route.
+	case StateInitial:
+		// Nothing to do. We'll eventually fill-in the gaps in the ID (if any)
+		// when we find a route.
 
-	case stateConnecting:
-		// A connection request has already been issued but hasn't
-		// completed yet.
+	case StateConnecting, StateSynSent, StateSynRecv:
+		// A connection request has already been issued but hasn't completed
+		// yet.
 		return tcpip.ErrAlreadyConnecting
 
-	case stateConnected:
+	case StateEstablished:
 		// The endpoint is already connected. If caller hasn't been notified yet, return success.
 		if !e.isConnectNotified {
 			e.isConnectNotified = true
@@ -1088,7 +1156,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) (er
 		// Otherwise return that it's already connected.
 		return tcpip.ErrAlreadyConnected
 
-	case stateError:
+	case StateError:
 		return e.hardError
 
 	default:
@@ -1154,7 +1222,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) (er
 	}
 
 	e.isRegistered = true
-	e.state = stateConnecting
+	e.state = StateConnecting
 	e.route = r.Clone()
 	e.boundNICID = nicid
 	e.effectiveNetProtos = netProtos
@@ -1175,7 +1243,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) (er
 		}
 		e.segmentQueue.mu.Unlock()
 		e.snd.updateMaxPayloadSize(int(e.route.MTU()), 0)
-		e.state = stateConnected
+		e.state = StateEstablished
 	}
 
 	if run {
@@ -1199,8 +1267,8 @@ func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) *tcpip.Error {
 	defer e.mu.Unlock()
 	e.shutdownFlags |= flags
 
-	switch e.state {
-	case stateConnected:
+	switch {
+	case e.state.connected():
 		// Close for read.
 		if (e.shutdownFlags & tcpip.ShutdownRead) != 0 {
 			// Mark read side as closed.
@@ -1241,7 +1309,7 @@ func (e *endpoint) Shutdown(flags tcpip.ShutdownFlags) *tcpip.Error {
 			e.sndCloseWaker.Assert()
 		}
 
-	case stateListen:
+	case e.state == StateListen:
 		// Tell protocolListenLoop to stop.
 		if flags&tcpip.ShutdownRead != 0 {
 			e.notifyProtocolGoroutine(notifyClose)
@@ -1269,7 +1337,7 @@ func (e *endpoint) Listen(backlog int) (err *tcpip.Error) {
 	// When the endpoint shuts down, it sets workerCleanup to true, and from
 	// that point onward, acceptedChan is the responsibility of the cleanup()
 	// method (and should not be touched anywhere else, including here).
-	if e.state == stateListen && !e.workerCleanup {
+	if e.state == StateListen && !e.workerCleanup {
 		// Adjust the size of the channel iff we can fix existing
 		// pending connections into the new one.
 		if len(e.acceptedChan) > backlog {
@@ -1288,7 +1356,7 @@ func (e *endpoint) Listen(backlog int) (err *tcpip.Error) {
 	}
 
 	// Endpoint must be bound before it can transition to listen mode.
-	if e.state != stateBound {
+	if e.state != StateBound {
 		return tcpip.ErrInvalidEndpointState
 	}
 
@@ -1298,7 +1366,7 @@ func (e *endpoint) Listen(backlog int) (err *tcpip.Error) {
 	}
 
 	e.isRegistered = true
-	e.state = stateListen
+	e.state = StateListen
 	if e.acceptedChan == nil {
 		e.acceptedChan = make(chan *endpoint, backlog)
 	}
@@ -1325,7 +1393,7 @@ func (e *endpoint) Accept() (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
 	defer e.mu.RUnlock()
 
 	// Endpoint must be in listen state before it can accept connections.
-	if e.state != stateListen {
+	if e.state != StateListen {
 		return nil, nil, tcpip.ErrInvalidEndpointState
 	}
 
@@ -1353,7 +1421,7 @@ func (e *endpoint) Bind(addr tcpip.FullAddress) (err *tcpip.Error) {
 	// Don't allow binding once endpoint is not in the initial state
 	// anymore. This is because once the endpoint goes into a connected or
 	// listen state, it is already bound.
-	if e.state != stateInitial {
+	if e.state != StateInitial {
 		return tcpip.ErrAlreadyBound
 	}
 
@@ -1408,7 +1476,7 @@ func (e *endpoint) Bind(addr tcpip.FullAddress) (err *tcpip.Error) {
 	}
 
 	// Mark endpoint as bound.
-	e.state = stateBound
+	e.state = StateBound
 
 	return nil
 }
@@ -1430,7 +1498,7 @@ func (e *endpoint) GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error) {
 	e.mu.RLock()
 	defer e.mu.RUnlock()
 
-	if e.state != stateConnected {
+	if !e.state.connected() {
 		return tcpip.FullAddress{}, tcpip.ErrNotConnected
 	}
 
@@ -1739,3 +1807,11 @@ func (e *endpoint) initGSO() {
 	gso.MaxSize = e.route.GSOMaxSize()
 	e.gso = gso
 }
+
+// State implements tcpip.Endpoint.State. It exports the endpoint's protocol
+// state for diagnostics.
+func (e *endpoint) State() uint32 {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	return uint32(e.state)
+}
diff --git a/pkg/tcpip/transport/tcp/endpoint_state.go b/pkg/tcpip/transport/tcp/endpoint_state.go
index e8aed2875..5f30c2374 100644
--- a/pkg/tcpip/transport/tcp/endpoint_state.go
+++ b/pkg/tcpip/transport/tcp/endpoint_state.go
@@ -49,8 +49,8 @@ func (e *endpoint) beforeSave() {
 	defer e.mu.Unlock()
 
 	switch e.state {
-	case stateInitial, stateBound:
-	case stateConnected:
+	case StateInitial, StateBound:
+	case StateEstablished, StateSynSent, StateSynRecv, StateFinWait1, StateFinWait2, StateTimeWait, StateCloseWait, StateLastAck, StateClosing:
 		if e.route.Capabilities()&stack.CapabilitySaveRestore == 0 {
 			if e.route.Capabilities()&stack.CapabilityDisconnectOk == 0 {
 				panic(tcpip.ErrSaveRejection{fmt.Errorf("endpoint cannot be saved in connected state: local %v:%d, remote %v:%d", e.id.LocalAddress, e.id.LocalPort, e.id.RemoteAddress, e.id.RemotePort)})
@@ -66,17 +66,17 @@ func (e *endpoint) beforeSave() {
 			break
 		}
 		fallthrough
-	case stateListen, stateConnecting:
+	case StateListen, StateConnecting:
 		e.drainSegmentLocked()
-		if e.state != stateClosed && e.state != stateError {
+		if e.state != StateClose && e.state != StateError {
 			if !e.workerRunning {
 				panic("endpoint has no worker running in listen, connecting, or connected state")
 			}
 			break
 		}
 		fallthrough
-	case stateError, stateClosed:
-		for e.state == stateError && e.workerRunning {
+	case StateError, StateClose:
+		for e.state == StateError && e.workerRunning {
 			e.mu.Unlock()
 			time.Sleep(100 * time.Millisecond)
 			e.mu.Lock()
@@ -92,7 +92,7 @@ func (e *endpoint) beforeSave() {
 		panic("endpoint still has waiters upon save")
 	}
 
-	if e.state != stateClosed && !((e.state == stateBound || e.state == stateListen) == e.isPortReserved) {
+	if e.state != StateClose && !((e.state == StateBound || e.state == StateListen) == e.isPortReserved) {
 		panic("endpoints which are not in the closed state must have a reserved port IFF they are in bound or listen state")
 	}
 }
@@ -132,7 +132,7 @@ func (e *endpoint) loadAcceptedChan(acceptedEndpoints []*endpoint) {
 }
 
 // saveState is invoked by stateify.
-func (e *endpoint) saveState() endpointState {
+func (e *endpoint) saveState() EndpointState {
 	return e.state
 }
 
@@ -146,15 +146,15 @@ var connectingLoading sync.WaitGroup
 // Bound endpoint loading happens last.
 
 // loadState is invoked by stateify.
-func (e *endpoint) loadState(state endpointState) {
+func (e *endpoint) loadState(state EndpointState) {
 	// This is to ensure that the loading wait groups include all applicable
 	// endpoints before any asynchronous calls to the Wait() methods.
 	switch state {
-	case stateConnected:
+	case StateEstablished, StateFinWait1, StateFinWait2, StateTimeWait, StateCloseWait, StateLastAck, StateClosing:
 		connectedLoading.Add(1)
-	case stateListen:
+	case StateListen:
 		listenLoading.Add(1)
-	case stateConnecting:
+	case StateConnecting, StateSynSent, StateSynRecv:
 		connectingLoading.Add(1)
 	}
 	e.state = state
@@ -168,7 +168,7 @@ func (e *endpoint) afterLoad() {
 
 	state := e.state
 	switch state {
-	case stateInitial, stateBound, stateListen, stateConnecting, stateConnected:
+	case StateInitial, StateBound, StateListen, StateConnecting, StateEstablished:
 		var ss SendBufferSizeOption
 		if err := e.stack.TransportProtocolOption(ProtocolNumber, &ss); err == nil {
 			if e.sndBufSize < ss.Min || e.sndBufSize > ss.Max {
@@ -181,7 +181,7 @@ func (e *endpoint) afterLoad() {
 	}
 
 	bind := func() {
-		e.state = stateInitial
+		e.state = StateInitial
 		if len(e.bindAddress) == 0 {
 			e.bindAddress = e.id.LocalAddress
 		}
@@ -191,7 +191,7 @@ func (e *endpoint) afterLoad() {
 	}
 
 	switch state {
-	case stateConnected:
+	case StateEstablished, StateFinWait1, StateFinWait2, StateTimeWait, StateCloseWait, StateLastAck, StateClosing:
 		bind()
 		if len(e.connectingAddress) == 0 {
 			// This endpoint is accepted by netstack but not yet by
@@ -211,7 +211,7 @@ func (e *endpoint) afterLoad() {
 			panic("endpoint connecting failed: " + err.String())
 		}
 		connectedLoading.Done()
-	case stateListen:
+	case StateListen:
 		tcpip.AsyncLoading.Add(1)
 		go func() {
 			connectedLoading.Wait()
@@ -223,7 +223,7 @@ func (e *endpoint) afterLoad() {
 			listenLoading.Done()
 			tcpip.AsyncLoading.Done()
 		}()
-	case stateConnecting:
+	case StateConnecting, StateSynSent, StateSynRecv:
 		tcpip.AsyncLoading.Add(1)
 		go func() {
 			connectedLoading.Wait()
@@ -235,7 +235,7 @@ func (e *endpoint) afterLoad() {
 			connectingLoading.Done()
 			tcpip.AsyncLoading.Done()
 		}()
-	case stateBound:
+	case StateBound:
 		tcpip.AsyncLoading.Add(1)
 		go func() {
 			connectedLoading.Wait()
@@ -244,7 +244,7 @@ func (e *endpoint) afterLoad() {
 			bind()
 			tcpip.AsyncLoading.Done()
 		}()
-	case stateClosed:
+	case StateClose:
 		if e.isPortReserved {
 			tcpip.AsyncLoading.Add(1)
 			go func() {
@@ -252,12 +252,12 @@ func (e *endpoint) afterLoad() {
 				listenLoading.Wait()
 				connectingLoading.Wait()
 				bind()
-				e.state = stateClosed
+				e.state = StateClose
 				tcpip.AsyncLoading.Done()
 			}()
 		}
 		fallthrough
-	case stateError:
+	case StateError:
 		tcpip.DeleteDanglingEndpoint(e)
 	}
 }
diff --git a/pkg/tcpip/transport/tcp/rcv.go b/pkg/tcpip/transport/tcp/rcv.go
index b08a0e356..f02fa6105 100644
--- a/pkg/tcpip/transport/tcp/rcv.go
+++ b/pkg/tcpip/transport/tcp/rcv.go
@@ -134,6 +134,7 @@ func (r *receiver) consumeSegment(s *segment, segSeq seqnum.Value, segLen seqnum
 	// sequence numbers that have been consumed.
 	TrimSACKBlockList(&r.ep.sack, r.rcvNxt)
 
+	// Handle FIN or FIN-ACK.
 	if s.flagIsSet(header.TCPFlagFin) {
 		r.rcvNxt++
 
@@ -144,6 +145,25 @@ func (r *receiver) consumeSegment(s *segment, segSeq seqnum.Value, segLen seqnum
 		r.closed = true
 		r.ep.readyToRead(nil)
 
+		// We just received a FIN, our next state depends on whether we sent a
+		// FIN already or not.
+		r.ep.mu.Lock()
+		switch r.ep.state {
+		case StateEstablished:
+			r.ep.state = StateCloseWait
+		case StateFinWait1:
+			if s.flagIsSet(header.TCPFlagAck) {
+				// FIN-ACK, transition to TIME-WAIT.
+				r.ep.state = StateTimeWait
+			} else {
+				// Simultaneous close, expecting a final ACK.
+				r.ep.state = StateClosing
+			}
+		case StateFinWait2:
+			r.ep.state = StateTimeWait
+		}
+		r.ep.mu.Unlock()
+
 		// Flush out any pending segments, except the very first one if
 		// it happens to be the one we're handling now because the
 		// caller is using it.
@@ -156,6 +176,23 @@ func (r *receiver) consumeSegment(s *segment, segSeq seqnum.Value, segLen seqnum
 			r.pendingRcvdSegments[i].decRef()
 		}
 		r.pendingRcvdSegments = r.pendingRcvdSegments[:first]
+
+		return true
+	}
+
+	// Handle ACK (not FIN-ACK, which we handled above) during one of the
+	// shutdown states.
+	if s.flagIsSet(header.TCPFlagAck) {
+		r.ep.mu.Lock()
+		switch r.ep.state {
+		case StateFinWait1:
+			r.ep.state = StateFinWait2
+		case StateClosing:
+			r.ep.state = StateTimeWait
+		case StateLastAck:
+			r.ep.state = StateClose
+		}
+		r.ep.mu.Unlock()
 	}
 
 	return true
diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go
index afc1d0a55..b236d7af2 100644
--- a/pkg/tcpip/transport/tcp/snd.go
+++ b/pkg/tcpip/transport/tcp/snd.go
@@ -632,6 +632,10 @@ func (s *sender) maybeSendSegment(seg *segment, limit int, end seqnum.Value) (se
 		}
 		seg.flags = header.TCPFlagAck | header.TCPFlagFin
 		segEnd = seg.sequenceNumber.Add(1)
+		// Transition to FIN-WAIT1 state since we're initiating an active close.
+		s.ep.mu.Lock()
+		s.ep.state = StateFinWait1
+		s.ep.mu.Unlock()
 	} else {
 		// We're sending a non-FIN segment.
 		if seg.flags&header.TCPFlagFin != 0 {
@@ -779,7 +783,7 @@ func (s *sender) sendData() {
 				break
 			}
 			dataSent = true
-			s.outstanding++
+			s.outstanding += s.pCount(seg)
 			s.writeNext = seg.Next()
 		}
 	}
diff --git a/pkg/tcpip/transport/tcp/tcp_state_autogen.go b/pkg/tcpip/transport/tcp/tcp_state_autogen.go
index 9049a99b2..5d7e11715 100755
--- a/pkg/tcpip/transport/tcp/tcp_state_autogen.go
+++ b/pkg/tcpip/transport/tcp/tcp_state_autogen.go
@@ -24,7 +24,7 @@ func (x *endpoint) save(m state.Map) {
 	x.beforeSave()
 	var lastError string = x.saveLastError()
 	m.SaveValue("lastError", lastError)
-	var state endpointState = x.saveState()
+	var state EndpointState = x.saveState()
 	m.SaveValue("state", state)
 	var hardError string = x.saveHardError()
 	m.SaveValue("hardError", hardError)
@@ -116,7 +116,7 @@ func (x *endpoint) load(m state.Map) {
 	m.Load("connectingAddress", &x.connectingAddress)
 	m.Load("gso", &x.gso)
 	m.LoadValue("lastError", new(string), func(y interface{}) { x.loadLastError(y.(string)) })
-	m.LoadValue("state", new(endpointState), func(y interface{}) { x.loadState(y.(endpointState)) })
+	m.LoadValue("state", new(EndpointState), func(y interface{}) { x.loadState(y.(EndpointState)) })
 	m.LoadValue("hardError", new(string), func(y interface{}) { x.loadHardError(y.(string)) })
 	m.LoadValue("acceptedChan", new([]*endpoint), func(y interface{}) { x.loadAcceptedChan(y.([]*endpoint)) })
 	m.AfterLoad(x.afterLoad)
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 3d52a4f31..fa7278286 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -1000,3 +1000,9 @@ func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, vv
 // HandleControlPacket implements stack.TransportEndpoint.HandleControlPacket.
 func (e *endpoint) HandleControlPacket(id stack.TransportEndpointID, typ stack.ControlType, extra uint32, vv buffer.VectorisedView) {
 }
+
+// State implements socket.Socket.State.
+func (e *endpoint) State() uint32 {
+	// TODO(b/112063468): Translate internal state to values returned by Linux.
+	return 0
+}
diff --git a/pkg/urpc/urpc.go b/pkg/urpc/urpc.go
index 0f155ec74..4ea684659 100644
--- a/pkg/urpc/urpc.go
+++ b/pkg/urpc/urpc.go
@@ -35,7 +35,7 @@ import (
 )
 
 // maxFiles determines the maximum file payload.
-const maxFiles = 16
+const maxFiles = 32
 
 // ErrTooManyFiles is returned when too many file descriptors are mapped.
 var ErrTooManyFiles = errors.New("too many files")
diff --git a/runsc/boot/config.go b/runsc/boot/config.go
index 15f624f9b..8564c502d 100644
--- a/runsc/boot/config.go
+++ b/runsc/boot/config.go
@@ -221,6 +221,11 @@ type Config struct {
 	// user, and without chrooting the sandbox process. This can be
 	// necessary in test environments that have limited capabilities.
 	TestOnlyAllowRunAsCurrentUserWithoutChroot bool
+
+	// NumNetworkChannels controls the number of AF_PACKET sockets that map
+	// to the same underlying network device. This allows netstack to better
+	// scale for high throughput use cases.
+	NumNetworkChannels int
 }
 
 // ToFlags returns a slice of flags that correspond to the given Config.
@@ -244,6 +249,7 @@ func (c *Config) ToFlags() []string {
 		"--panic-signal=" + strconv.Itoa(c.PanicSignal),
 		"--profile=" + strconv.FormatBool(c.ProfileEnable),
 		"--net-raw=" + strconv.FormatBool(c.EnableRaw),
+		"--num-network-channels=" + strconv.Itoa(c.NumNetworkChannels),
 	}
 	if c.TestOnlyAllowRunAsCurrentUserWithoutChroot {
 		// Only include if set since it is never to be used by users.
diff --git a/runsc/boot/filter/config.go b/runsc/boot/filter/config.go
index 652da1cef..ef2dbfad2 100644
--- a/runsc/boot/filter/config.go
+++ b/runsc/boot/filter/config.go
@@ -246,6 +246,10 @@ var allowedSyscalls = seccomp.SyscallRules{
 	},
 	syscall.SYS_SETITIMER: {},
 	syscall.SYS_SHUTDOWN: []seccomp.Rule{
+		// Used by fs/host to shutdown host sockets.
+		{seccomp.AllowAny{}, seccomp.AllowValue(syscall.SHUT_RD)},
+		{seccomp.AllowAny{}, seccomp.AllowValue(syscall.SHUT_WR)},
+		// Used by unet to shutdown connections.
 		{seccomp.AllowAny{}, seccomp.AllowValue(syscall.SHUT_RDWR)},
 	},
 	syscall.SYS_SIGALTSTACK:     {},
diff --git a/runsc/boot/loader.go b/runsc/boot/loader.go
index a997776f8..42bddb2e8 100644
--- a/runsc/boot/loader.go
+++ b/runsc/boot/loader.go
@@ -29,6 +29,7 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
 	"gvisor.googlesource.com/gvisor/pkg/cpuid"
 	"gvisor.googlesource.com/gvisor/pkg/log"
+	"gvisor.googlesource.com/gvisor/pkg/memutil"
 	"gvisor.googlesource.com/gvisor/pkg/rand"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/control"
@@ -37,7 +38,6 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/loader"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/memutil"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/pgalloc"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/platform/kvm"
@@ -424,6 +424,9 @@ func createMemoryFile() (*pgalloc.MemoryFile, error) {
 		return nil, fmt.Errorf("error creating memfd: %v", err)
 	}
 	memfile := os.NewFile(uintptr(memfd), memfileName)
+	// We can't enable pgalloc.MemoryFileOpts.UseHostMemcgPressure even if
+	// there are memory cgroups specified, because at this point we're already
+	// in a mount namespace in which the relevant cgroupfs is not visible.
 	mf, err := pgalloc.NewMemoryFile(memfile, pgalloc.MemoryFileOpts{})
 	if err != nil {
 		memfile.Close()
diff --git a/runsc/boot/network.go b/runsc/boot/network.go
index 0a154d90b..82c259f47 100644
--- a/runsc/boot/network.go
+++ b/runsc/boot/network.go
@@ -57,6 +57,10 @@ type FDBasedLink struct {
 	Routes      []Route
 	GSOMaxSize  uint32
 	LinkAddress []byte
+
+	// NumChannels controls how many underlying FD's are to be used to
+	// create this endpoint.
+	NumChannels int
 }
 
 // LoopbackLink configures a loopback li nk.
@@ -68,8 +72,9 @@ type LoopbackLink struct {
 
 // CreateLinksAndRoutesArgs are arguments to CreateLinkAndRoutes.
 type CreateLinksAndRoutesArgs struct {
-	// FilePayload contains the fds associated with the FDBasedLinks.  The
-	// two slices must have the same length.
+	// FilePayload contains the fds associated with the FDBasedLinks. The
+	// number of fd's should match the sum of the NumChannels field of the
+	// FDBasedLink entries below.
 	urpc.FilePayload
 
 	LoopbackLinks []LoopbackLink
@@ -95,8 +100,12 @@ func (r *Route) toTcpipRoute(id tcpip.NICID) tcpip.Route {
 // CreateLinksAndRoutes creates links and routes in a network stack.  It should
 // only be called once.
 func (n *Network) CreateLinksAndRoutes(args *CreateLinksAndRoutesArgs, _ *struct{}) error {
-	if len(args.FilePayload.Files) != len(args.FDBasedLinks) {
-		return fmt.Errorf("FilePayload must be same length at FDBasedLinks")
+	wantFDs := 0
+	for _, l := range args.FDBasedLinks {
+		wantFDs += l.NumChannels
+	}
+	if got := len(args.FilePayload.Files); got != wantFDs {
+		return fmt.Errorf("args.FilePayload.Files has %d FD's but we need %d entries based on FDBasedLinks", got, wantFDs)
 	}
 
 	var nicID tcpip.NICID
@@ -123,20 +132,26 @@ func (n *Network) CreateLinksAndRoutes(args *CreateLinksAndRoutesArgs, _ *struct
 		}
 	}
 
-	for i, link := range args.FDBasedLinks {
+	fdOffset := 0
+	for _, link := range args.FDBasedLinks {
 		nicID++
 		nicids[link.Name] = nicID
 
-		// Copy the underlying FD.
-		oldFD := args.FilePayload.Files[i].Fd()
-		newFD, err := syscall.Dup(int(oldFD))
-		if err != nil {
-			return fmt.Errorf("failed to dup FD %v: %v", oldFD, err)
+		FDs := []int{}
+		for j := 0; j < link.NumChannels; j++ {
+			// Copy the underlying FD.
+			oldFD := args.FilePayload.Files[fdOffset].Fd()
+			newFD, err := syscall.Dup(int(oldFD))
+			if err != nil {
+				return fmt.Errorf("failed to dup FD %v: %v", oldFD, err)
+			}
+			FDs = append(FDs, newFD)
+			fdOffset++
 		}
 
 		mac := tcpip.LinkAddress(link.LinkAddress)
 		linkEP, err := fdbased.New(&fdbased.Options{
-			FD:                 newFD,
+			FDs:                FDs,
 			MTU:                uint32(link.MTU),
 			EthernetHeader:     true,
 			Address:            mac,
@@ -148,7 +163,7 @@ func (n *Network) CreateLinksAndRoutes(args *CreateLinksAndRoutesArgs, _ *struct
 			return err
 		}
 
-		log.Infof("Enabling interface %q with id %d on addresses %+v (%v)", link.Name, nicID, link.Addresses, mac)
+		log.Infof("Enabling interface %q with id %d on addresses %+v (%v) w/ %d channels", link.Name, nicID, link.Addresses, mac, link.NumChannels)
 		if err := n.createNICWithAddrs(nicID, link.Name, linkEP, link.Addresses, false /* loopback */); err != nil {
 			return err
 		}
diff --git a/runsc/cmd/cmd.go b/runsc/cmd/cmd.go
index a2fc377d1..5b4cc4a39 100644
--- a/runsc/cmd/cmd.go
+++ b/runsc/cmd/cmd.go
@@ -17,34 +17,15 @@ package cmd
 
 import (
 	"fmt"
-	"os"
 	"runtime"
 	"strconv"
 	"syscall"
 
-	"github.com/google/subcommands"
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 	"gvisor.googlesource.com/gvisor/pkg/log"
 	"gvisor.googlesource.com/gvisor/runsc/specutils"
 )
 
-// Errorf logs to stderr and returns subcommands.ExitFailure.
-func Errorf(s string, args ...interface{}) subcommands.ExitStatus {
-	// If runsc is being invoked by docker or cri-o, then we might not have
-	// access to stderr, so we log a serious-looking warning in addition to
-	// writing to stderr.
-	log.Warningf("FATAL ERROR: "+s, args...)
-	fmt.Fprintf(os.Stderr, s+"\n", args...)
-	// Return an error that is unlikely to be used by the application.
-	return subcommands.ExitFailure
-}
-
-// Fatalf logs to stderr and exits with a failure status code.
-func Fatalf(s string, args ...interface{}) {
-	Errorf(s, args...)
-	os.Exit(128)
-}
-
 // intFlags can be used with int flags that appear multiple times.
 type intFlags []int
 
diff --git a/runsc/cmd/create.go b/runsc/cmd/create.go
index 629c198fd..8bf9b7dcf 100644
--- a/runsc/cmd/create.go
+++ b/runsc/cmd/create.go
@@ -16,7 +16,6 @@ package cmd
 
 import (
 	"context"
-
 	"flag"
 	"github.com/google/subcommands"
 	"gvisor.googlesource.com/gvisor/runsc/boot"
diff --git a/runsc/cmd/error.go b/runsc/cmd/error.go
new file mode 100644
index 000000000..700b19f14
--- /dev/null
+++ b/runsc/cmd/error.go
@@ -0,0 +1,72 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cmd
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"time"
+
+	"github.com/google/subcommands"
+	"gvisor.googlesource.com/gvisor/pkg/log"
+)
+
+// ErrorLogger is where error messages should be written to. These messages are
+// consumed by containerd and show up to users of command line tools,
+// like docker/kubectl.
+var ErrorLogger io.Writer
+
+type jsonError struct {
+	Msg   string    `json:"msg"`
+	Level string    `json:"level"`
+	Time  time.Time `json:"time"`
+}
+
+// Errorf logs error to containerd log (--log), to stderr, and debug logs. It
+// returns subcommands.ExitFailure for convenience with subcommand.Execute()
+// methods:
+//    return Errorf("Danger! Danger!")
+//
+func Errorf(format string, args ...interface{}) subcommands.ExitStatus {
+	// If runsc is being invoked by docker or cri-o, then we might not have
+	// access to stderr, so we log a serious-looking warning in addition to
+	// writing to stderr.
+	log.Warningf("FATAL ERROR: "+format, args...)
+	fmt.Fprintf(os.Stderr, format+"\n", args...)
+
+	j := jsonError{
+		Msg:   fmt.Sprintf(format, args...),
+		Level: "error",
+		Time:  time.Now(),
+	}
+	b, err := json.Marshal(j)
+	if err != nil {
+		panic(err)
+	}
+	if ErrorLogger != nil {
+		ErrorLogger.Write(b)
+	}
+
+	return subcommands.ExitFailure
+}
+
+// Fatalf logs the same way as Errorf() does, plus *exits* the process.
+func Fatalf(format string, args ...interface{}) {
+	Errorf(format, args...)
+	// Return an error that is unlikely to be used by the application.
+	os.Exit(128)
+}
diff --git a/runsc/cmd/exec.go b/runsc/cmd/exec.go
index 8cd070e61..0eeaaadba 100644
--- a/runsc/cmd/exec.go
+++ b/runsc/cmd/exec.go
@@ -143,13 +143,16 @@ func (ex *Exec) Execute(_ context.Context, f *flag.FlagSet, args ...interface{})
 	// write the child's PID to the pid file. So when the container returns, the
 	// child process will also return and signal containerd.
 	if ex.detach {
-		return ex.execAndWait(waitStatus)
+		return ex.execChildAndWait(waitStatus)
 	}
+	return ex.exec(c, e, waitStatus)
+}
 
+func (ex *Exec) exec(c *container.Container, e *control.ExecArgs, waitStatus *syscall.WaitStatus) subcommands.ExitStatus {
 	// Start the new process and get it pid.
 	pid, err := c.Execute(e)
 	if err != nil {
-		Fatalf("executing processes for container: %v", err)
+		return Errorf("executing processes for container: %v", err)
 	}
 
 	if e.StdioIsPty {
@@ -163,29 +166,29 @@ func (ex *Exec) Execute(_ context.Context, f *flag.FlagSet, args ...interface{})
 	if ex.internalPidFile != "" {
 		pidStr := []byte(strconv.Itoa(int(pid)))
 		if err := ioutil.WriteFile(ex.internalPidFile, pidStr, 0644); err != nil {
-			Fatalf("writing internal pid file %q: %v", ex.internalPidFile, err)
+			return Errorf("writing internal pid file %q: %v", ex.internalPidFile, err)
 		}
 	}
 
-	// Generate the pid file after the internal pid file is generated, so that users
-	// can safely assume that the internal pid file is ready after `runsc exec -d`
-	// returns.
+	// Generate the pid file after the internal pid file is generated, so that
+	// users can safely assume that the internal pid file is ready after
+	// `runsc exec -d` returns.
 	if ex.pidFile != "" {
 		if err := ioutil.WriteFile(ex.pidFile, []byte(strconv.Itoa(os.Getpid())), 0644); err != nil {
-			Fatalf("writing pid file: %v", err)
+			return Errorf("writing pid file: %v", err)
 		}
 	}
 
 	// Wait for the process to exit.
 	ws, err := c.WaitPID(pid)
 	if err != nil {
-		Fatalf("waiting on pid %d: %v", pid, err)
+		return Errorf("waiting on pid %d: %v", pid, err)
 	}
 	*waitStatus = ws
 	return subcommands.ExitSuccess
 }
 
-func (ex *Exec) execAndWait(waitStatus *syscall.WaitStatus) subcommands.ExitStatus {
+func (ex *Exec) execChildAndWait(waitStatus *syscall.WaitStatus) subcommands.ExitStatus {
 	var args []string
 	for _, a := range os.Args[1:] {
 		if !strings.Contains(a, "detach") {
@@ -193,7 +196,7 @@ func (ex *Exec) execAndWait(waitStatus *syscall.WaitStatus) subcommands.ExitStat
 		}
 	}
 
-	// The command needs to write a pid file so that execAndWait can tell
+	// The command needs to write a pid file so that execChildAndWait can tell
 	// when it has started. If no pid-file was provided, we should use a
 	// filename in a temp directory.
 	pidFile := ex.pidFile
@@ -262,7 +265,10 @@ func (ex *Exec) execAndWait(waitStatus *syscall.WaitStatus) subcommands.ExitStat
 		return false, nil
 	}
 	if err := specutils.WaitForReady(cmd.Process.Pid, 10*time.Second, ready); err != nil {
-		Fatalf("unexpected error waiting for PID file, err: %v", err)
+		// Don't log fatal error here, otherwise it will override the error logged
+		// by the child process that has failed to start.
+		log.Warningf("Unexpected error waiting for PID file, err: %v", err)
+		return subcommands.ExitFailure
 	}
 
 	*waitStatus = 0
diff --git a/runsc/cmd/start.go b/runsc/cmd/start.go
index 657726251..31e8f42bb 100644
--- a/runsc/cmd/start.go
+++ b/runsc/cmd/start.go
@@ -16,7 +16,6 @@ package cmd
 
 import (
 	"context"
-
 	"flag"
 	"github.com/google/subcommands"
 	"gvisor.googlesource.com/gvisor/runsc/boot"
diff --git a/runsc/main.go b/runsc/main.go
index 11bc73f75..6f8e6e378 100644
--- a/runsc/main.go
+++ b/runsc/main.go
@@ -48,11 +48,12 @@ var (
 	// system that are not covered by the runtime spec.
 
 	// Debugging flags.
-	debugLog       = flag.String("debug-log", "", "additional location for logs. If it ends with '/', log files are created inside the directory with default names. The following variables are available: %TIMESTAMP%, %COMMAND%.")
-	logPackets     = flag.Bool("log-packets", false, "enable network packet logging")
-	logFD          = flag.Int("log-fd", -1, "file descriptor to log to.  If set, the 'log' flag is ignored.")
-	debugLogFD     = flag.Int("debug-log-fd", -1, "file descriptor to write debug logs to.  If set, the 'debug-log-dir' flag is ignored.")
-	debugLogFormat = flag.String("debug-log-format", "text", "log format: text (default), json, or json-k8s")
+	debugLog        = flag.String("debug-log", "", "additional location for logs. If it ends with '/', log files are created inside the directory with default names. The following variables are available: %TIMESTAMP%, %COMMAND%.")
+	logPackets      = flag.Bool("log-packets", false, "enable network packet logging")
+	logFD           = flag.Int("log-fd", -1, "file descriptor to log to.  If set, the 'log' flag is ignored.")
+	debugLogFD      = flag.Int("debug-log-fd", -1, "file descriptor to write debug logs to.  If set, the 'debug-log-dir' flag is ignored.")
+	debugLogFormat  = flag.String("debug-log-format", "text", "log format: text (default), json, or json-k8s")
+	alsoLogToStderr = flag.Bool("alsologtostderr", false, "send log messages to stderr")
 
 	// Debugging flags: strace related
 	strace         = flag.Bool("strace", false, "enable strace")
@@ -60,16 +61,16 @@ var (
 	straceLogSize  = flag.Uint("strace-log-size", 1024, "default size (in bytes) to log data argument blobs")
 
 	// Flags that control sandbox runtime behavior.
-	platform       = flag.String("platform", "ptrace", "specifies which platform to use: ptrace (default), kvm")
-	network        = flag.String("network", "sandbox", "specifies which network to use: sandbox (default), host, none. Using network inside the sandbox is more secure because it's isolated from the host network.")
-	gso            = flag.Bool("gso", true, "enable generic segmenation offload")
-	fileAccess     = flag.String("file-access", "exclusive", "specifies which filesystem to use for the root mount: exclusive (default), shared. Volume mounts are always shared.")
-	overlay        = flag.Bool("overlay", false, "wrap filesystem mounts with writable overlay. All modifications are stored in memory inside the sandbox.")
-	watchdogAction = flag.String("watchdog-action", "log", "sets what action the watchdog takes when triggered: log (default), panic.")
-	panicSignal    = flag.Int("panic-signal", -1, "register signal handling that panics. Usually set to SIGUSR2(12) to troubleshoot hangs. -1 disables it.")
-	profile        = flag.Bool("profile", false, "prepares the sandbox to use Golang profiler. Note that enabling profiler loosens the seccomp protection added to the sandbox (DO NOT USE IN PRODUCTION).")
-	netRaw         = flag.Bool("net-raw", false, "enable raw sockets. When false, raw sockets are disabled by removing CAP_NET_RAW from containers (`runsc exec` will still be able to utilize raw sockets). Raw sockets allow malicious containers to craft packets and potentially attack the network.")
-
+	platform                                   = flag.String("platform", "ptrace", "specifies which platform to use: ptrace (default), kvm")
+	network                                    = flag.String("network", "sandbox", "specifies which network to use: sandbox (default), host, none. Using network inside the sandbox is more secure because it's isolated from the host network.")
+	gso                                        = flag.Bool("gso", true, "enable generic segmenation offload")
+	fileAccess                                 = flag.String("file-access", "exclusive", "specifies which filesystem to use for the root mount: exclusive (default), shared. Volume mounts are always shared.")
+	overlay                                    = flag.Bool("overlay", false, "wrap filesystem mounts with writable overlay. All modifications are stored in memory inside the sandbox.")
+	watchdogAction                             = flag.String("watchdog-action", "log", "sets what action the watchdog takes when triggered: log (default), panic.")
+	panicSignal                                = flag.Int("panic-signal", -1, "register signal handling that panics. Usually set to SIGUSR2(12) to troubleshoot hangs. -1 disables it.")
+	profile                                    = flag.Bool("profile", false, "prepares the sandbox to use Golang profiler. Note that enabling profiler loosens the seccomp protection added to the sandbox (DO NOT USE IN PRODUCTION).")
+	netRaw                                     = flag.Bool("net-raw", false, "enable raw sockets. When false, raw sockets are disabled by removing CAP_NET_RAW from containers (`runsc exec` will still be able to utilize raw sockets). Raw sockets allow malicious containers to craft packets and potentially attack the network.")
+	numNetworkChannels                         = flag.Int("num-network-channels", 1, "number of underlying channels(FDs) to use for network link endpoints.")
 	testOnlyAllowRunAsCurrentUserWithoutChroot = flag.Bool("TESTONLY-unsafe-nonroot", false, "TEST ONLY; do not ever use! This skips many security measures that isolate the host from the sandbox.")
 )
 
@@ -117,6 +118,22 @@ func main() {
 		os.Exit(0)
 	}
 
+	var errorLogger io.Writer
+	if *logFD > -1 {
+		errorLogger = os.NewFile(uintptr(*logFD), "error log file")
+
+	} else if *logFilename != "" {
+		// We must set O_APPEND and not O_TRUNC because Docker passes
+		// the same log file for all commands (and also parses these
+		// log files), so we can't destroy them on each command.
+		var err error
+		errorLogger, err = os.OpenFile(*logFilename, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0644)
+		if err != nil {
+			cmd.Fatalf("error opening log file %q: %v", *logFilename, err)
+		}
+	}
+	cmd.ErrorLogger = errorLogger
+
 	platformType, err := boot.MakePlatformType(*platform)
 	if err != nil {
 		cmd.Fatalf("%v", err)
@@ -141,6 +158,10 @@ func main() {
 		cmd.Fatalf("%v", err)
 	}
 
+	if *numNetworkChannels <= 0 {
+		cmd.Fatalf("num_network_channels must be > 0, got: %d", *numNetworkChannels)
+	}
+
 	// Create a new Config from the flags.
 	conf := &boot.Config{
 		RootDir:        *rootDir,
@@ -162,6 +183,7 @@ func main() {
 		ProfileEnable:  *profile,
 		EnableRaw:      *netRaw,
 		TestOnlyAllowRunAsCurrentUserWithoutChroot: *testOnlyAllowRunAsCurrentUserWithoutChroot,
+		NumNetworkChannels:                         *numNetworkChannels,
 	}
 	if len(*straceSyscalls) != 0 {
 		conf.StraceSyscalls = strings.Split(*straceSyscalls, ",")
@@ -174,24 +196,7 @@ func main() {
 
 	subcommand := flag.CommandLine.Arg(0)
 
-	var logFile io.Writer = os.Stderr
-	if *logFD > -1 {
-		logFile = os.NewFile(uintptr(*logFD), "log file")
-	} else if *logFilename != "" {
-		// We must set O_APPEND and not O_TRUNC because Docker passes
-		// the same log file for all commands (and also parses these
-		// log files), so we can't destroy them on each command.
-		f, err := os.OpenFile(*logFilename, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0644)
-		if err != nil {
-			cmd.Fatalf("error opening log file %q: %v", *logFilename, err)
-		}
-		logFile = f
-	} else if subcommand == "do" {
-		logFile = ioutil.Discard
-	}
-
-	e := newEmitter(*logFormat, logFile)
-
+	var e log.Emitter
 	if *debugLogFD > -1 {
 		f := os.NewFile(uintptr(*debugLogFD), "debug log file")
 
@@ -201,28 +206,31 @@ func main() {
 			cmd.Fatalf("flag --debug-log-fd should only be passed to 'boot' and 'gofer' command, but was passed to %q", subcommand)
 		}
 
-		// If we are the boot process, then we own our stdio FDs and
-		// can do what we want with them. Since Docker and Containerd
-		// both eat boot's stderr, we dup our stderr to the provided
-		// log FD so that panics will appear in the logs, rather than
-		// just disappear.
+		// If we are the boot process, then we own our stdio FDs and can do what we
+		// want with them. Since Docker and Containerd both eat boot's stderr, we
+		// dup our stderr to the provided log FD so that panics will appear in the
+		// logs, rather than just disappear.
 		if err := syscall.Dup2(int(f.Fd()), int(os.Stderr.Fd())); err != nil {
 			cmd.Fatalf("error dup'ing fd %d to stderr: %v", f.Fd(), err)
 		}
 
-		if logFile == os.Stderr {
-			// Suppress logging to stderr when debug log is enabled. Otherwise all
-			// messages will be duplicated in the debug log (see Dup2() call above).
-			e = newEmitter(*debugLogFormat, f)
-		} else {
-			e = log.MultiEmitter{e, newEmitter(*debugLogFormat, f)}
-		}
+		e = newEmitter(*debugLogFormat, f)
+
 	} else if *debugLog != "" {
 		f, err := specutils.DebugLogFile(*debugLog, subcommand)
 		if err != nil {
 			cmd.Fatalf("error opening debug log file in %q: %v", *debugLog, err)
 		}
-		e = log.MultiEmitter{e, newEmitter(*debugLogFormat, f)}
+		e = newEmitter(*debugLogFormat, f)
+
+	} else {
+		// Stderr is reserved for the application, just discard the logs if no debug
+		// log is specified.
+		e = newEmitter("text", ioutil.Discard)
+	}
+
+	if *alsoLogToStderr {
+		e = log.MultiEmitter{e, newEmitter(*debugLogFormat, os.Stderr)}
 	}
 
 	log.SetTarget(e)
diff --git a/runsc/sandbox/network.go b/runsc/sandbox/network.go
index 0460d5f1a..1fd091514 100644
--- a/runsc/sandbox/network.go
+++ b/runsc/sandbox/network.go
@@ -68,7 +68,7 @@ func setupNetwork(conn *urpc.Client, pid int, spec *specs.Spec, conf *boot.Confi
 		// Build the path to the net namespace of the sandbox process.
 		// This is what we will copy.
 		nsPath := filepath.Join("/proc", strconv.Itoa(pid), "ns/net")
-		if err := createInterfacesAndRoutesFromNS(conn, nsPath, conf.GSO); err != nil {
+		if err := createInterfacesAndRoutesFromNS(conn, nsPath, conf.GSO, conf.NumNetworkChannels); err != nil {
 			return fmt.Errorf("creating interfaces from net namespace %q: %v", nsPath, err)
 		}
 	case boot.NetworkHost:
@@ -138,7 +138,7 @@ func isRootNS() (bool, error) {
 // createInterfacesAndRoutesFromNS scrapes the interface and routes from the
 // net namespace with the given path, creates them in the sandbox, and removes
 // them from the host.
-func createInterfacesAndRoutesFromNS(conn *urpc.Client, nsPath string, enableGSO bool) error {
+func createInterfacesAndRoutesFromNS(conn *urpc.Client, nsPath string, enableGSO bool, numNetworkChannels int) error {
 	// Join the network namespace that we will be copying.
 	restore, err := joinNetNS(nsPath)
 	if err != nil {
@@ -202,25 +202,6 @@ func createInterfacesAndRoutesFromNS(conn *urpc.Client, nsPath string, enableGSO
 			continue
 		}
 
-		// Create the socket.
-		const protocol = 0x0300 // htons(ETH_P_ALL)
-		fd, err := syscall.Socket(syscall.AF_PACKET, syscall.SOCK_RAW, protocol)
-		if err != nil {
-			return fmt.Errorf("unable to create raw socket: %v", err)
-		}
-		deviceFile := os.NewFile(uintptr(fd), "raw-device-fd")
-
-		// Bind to the appropriate device.
-		ll := syscall.SockaddrLinklayer{
-			Protocol: protocol,
-			Ifindex:  iface.Index,
-			Hatype:   0, // No ARP type.
-			Pkttype:  syscall.PACKET_OTHERHOST,
-		}
-		if err := syscall.Bind(fd, &ll); err != nil {
-			return fmt.Errorf("unable to bind to %q: %v", iface.Name, err)
-		}
-
 		// Scrape the routes before removing the address, since that
 		// will remove the routes as well.
 		routes, def, err := routesForIface(iface)
@@ -236,9 +217,10 @@ func createInterfacesAndRoutesFromNS(conn *urpc.Client, nsPath string, enableGSO
 		}
 
 		link := boot.FDBasedLink{
-			Name:   iface.Name,
-			MTU:    iface.MTU,
-			Routes: routes,
+			Name:        iface.Name,
+			MTU:         iface.MTU,
+			Routes:      routes,
+			NumChannels: numNetworkChannels,
 		}
 
 		// Get the link for the interface.
@@ -248,30 +230,23 @@ func createInterfacesAndRoutesFromNS(conn *urpc.Client, nsPath string, enableGSO
 		}
 		link.LinkAddress = []byte(ifaceLink.Attrs().HardwareAddr)
 
-		if enableGSO {
-			gso, err := isGSOEnabled(fd, iface.Name)
+		log.Debugf("Setting up network channels")
+		// Create the socket for the device.
+		for i := 0; i < link.NumChannels; i++ {
+			log.Debugf("Creating Channel %d", i)
+			socketEntry, err := createSocket(iface, ifaceLink, enableGSO)
 			if err != nil {
-				return fmt.Errorf("getting GSO for interface %q: %v", iface.Name, err)
+				return fmt.Errorf("failed to createSocket for %s : %v", iface.Name, err)
 			}
-			if gso {
-				if err := syscall.SetsockoptInt(fd, syscall.SOL_PACKET, unix.PACKET_VNET_HDR, 1); err != nil {
-					return fmt.Errorf("unable to enable the PACKET_VNET_HDR option: %v", err)
-				}
-				link.GSOMaxSize = ifaceLink.Attrs().GSOMaxSize
+			if i == 0 {
+				link.GSOMaxSize = socketEntry.gsoMaxSize
 			} else {
-				log.Infof("GSO not available in host.")
+				if link.GSOMaxSize != socketEntry.gsoMaxSize {
+					return fmt.Errorf("inconsistent gsoMaxSize %d and %d when creating multiple channels for same interface: %s",
+						link.GSOMaxSize, socketEntry.gsoMaxSize, iface.Name)
+				}
 			}
-		}
-
-		// Use SO_RCVBUFFORCE because on linux the receive buffer for an
-		// AF_PACKET socket is capped by "net.core.rmem_max". rmem_max
-		// defaults to a unusually low value of 208KB. This is too low
-		// for gVisor to be able to receive packets at high throughputs
-		// without incurring packet drops.
-		const rcvBufSize = 4 << 20 // 4MB.
-
-		if err := syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_RCVBUFFORCE, rcvBufSize); err != nil {
-			return fmt.Errorf("failed to increase socket rcv buffer to %d: %v", rcvBufSize, err)
+			args.FilePayload.Files = append(args.FilePayload.Files, socketEntry.deviceFile)
 		}
 
 		// Collect the addresses for the interface, enable forwarding,
@@ -285,7 +260,6 @@ func createInterfacesAndRoutesFromNS(conn *urpc.Client, nsPath string, enableGSO
 			}
 		}
 
-		args.FilePayload.Files = append(args.FilePayload.Files, deviceFile)
 		args.FDBasedLinks = append(args.FDBasedLinks, link)
 	}
 
@@ -296,6 +270,61 @@ func createInterfacesAndRoutesFromNS(conn *urpc.Client, nsPath string, enableGSO
 	return nil
 }
 
+type socketEntry struct {
+	deviceFile *os.File
+	gsoMaxSize uint32
+}
+
+// createSocket creates an underlying AF_PACKET socket and configures it for use by
+// the sentry and returns an *os.File that wraps the underlying socket fd.
+func createSocket(iface net.Interface, ifaceLink netlink.Link, enableGSO bool) (*socketEntry, error) {
+	// Create the socket.
+	const protocol = 0x0300 // htons(ETH_P_ALL)
+	fd, err := syscall.Socket(syscall.AF_PACKET, syscall.SOCK_RAW, protocol)
+	if err != nil {
+		return nil, fmt.Errorf("unable to create raw socket: %v", err)
+	}
+	deviceFile := os.NewFile(uintptr(fd), "raw-device-fd")
+	// Bind to the appropriate device.
+	ll := syscall.SockaddrLinklayer{
+		Protocol: protocol,
+		Ifindex:  iface.Index,
+		Hatype:   0, // No ARP type.
+		Pkttype:  syscall.PACKET_OTHERHOST,
+	}
+	if err := syscall.Bind(fd, &ll); err != nil {
+		return nil, fmt.Errorf("unable to bind to %q: %v", iface.Name, err)
+	}
+
+	gsoMaxSize := uint32(0)
+	if enableGSO {
+		gso, err := isGSOEnabled(fd, iface.Name)
+		if err != nil {
+			return nil, fmt.Errorf("getting GSO for interface %q: %v", iface.Name, err)
+		}
+		if gso {
+			if err := syscall.SetsockoptInt(fd, syscall.SOL_PACKET, unix.PACKET_VNET_HDR, 1); err != nil {
+				return nil, fmt.Errorf("unable to enable the PACKET_VNET_HDR option: %v", err)
+			}
+			gsoMaxSize = ifaceLink.Attrs().GSOMaxSize
+		} else {
+			log.Infof("GSO not available in host.")
+		}
+	}
+
+	// Use SO_RCVBUFFORCE because on linux the receive buffer for an
+	// AF_PACKET socket is capped by "net.core.rmem_max". rmem_max
+	// defaults to a unusually low value of 208KB. This is too low
+	// for gVisor to be able to receive packets at high throughputs
+	// without incurring packet drops.
+	const rcvBufSize = 4 << 20 // 4MB.
+
+	if err := syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_RCVBUFFORCE, rcvBufSize); err != nil {
+		return nil, fmt.Errorf("failed to increase socket rcv buffer to %d: %v", rcvBufSize, err)
+	}
+	return &socketEntry{deviceFile, gsoMaxSize}, nil
+}
+
 // loopbackLinks collects the links for a loopback interface.
 func loopbackLinks(iface net.Interface, addrs []net.Addr) ([]boot.LoopbackLink, error) {
 	var links []boot.LoopbackLink