Merge release-20200323.0-136-g5d885d7 (automated)

5 files changed, 1232 insertions, 19 deletions

diff --git a/pkg/sentry/kernel/fd_table.go b/pkg/sentry/kernel/fd_table.go
index d09d97825..ed40b5303 100644
--- a/pkg/sentry/kernel/fd_table.go
+++ b/pkg/sentry/kernel/fd_table.go
@@ -307,6 +307,61 @@ func (f *FDTable) NewFDs(ctx context.Context, fd int32, files []*fs.File, flags
 	return fds, nil
 }
 
+// NewFDsVFS2 allocates new FDs guaranteed to be the lowest number available
+// greater than or equal to the fd parameter. All files will share the set
+// flags. Success is guaranteed to be all or none.
+func (f *FDTable) NewFDsVFS2(ctx context.Context, fd int32, files []*vfs.FileDescription, flags FDFlags) (fds []int32, err error) {
+	if fd < 0 {
+		// Don't accept negative FDs.
+		return nil, syscall.EINVAL
+	}
+
+	// Default limit.
+	end := int32(math.MaxInt32)
+
+	// Ensure we don't get past the provided limit.
+	if limitSet := limits.FromContext(ctx); limitSet != nil {
+		lim := limitSet.Get(limits.NumberOfFiles)
+		if lim.Cur != limits.Infinity {
+			end = int32(lim.Cur)
+		}
+		if fd >= end {
+			return nil, syscall.EMFILE
+		}
+	}
+
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	// From f.next to find available fd.
+	if fd < f.next {
+		fd = f.next
+	}
+
+	// Install all entries.
+	for i := fd; i < end && len(fds) < len(files); i++ {
+		if d, _, _ := f.getVFS2(i); d == nil {
+			f.setVFS2(i, files[len(fds)], flags) // Set the descriptor.
+			fds = append(fds, i)                 // Record the file descriptor.
+		}
+	}
+
+	// Failure? Unwind existing FDs.
+	if len(fds) < len(files) {
+		for _, i := range fds {
+			f.setVFS2(i, nil, FDFlags{}) // Zap entry.
+		}
+		return nil, syscall.EMFILE
+	}
+
+	if fd == f.next {
+		// Update next search start position.
+		f.next = fds[len(fds)-1] + 1
+	}
+
+	return fds, nil
+}
+
 // NewFDVFS2 allocates a file descriptor greater than or equal to minfd for
 // the given file description. If it succeeds, it takes a reference on file.
 func (f *FDTable) NewFDVFS2(ctx context.Context, minfd int32, file *vfs.FileDescription, flags FDFlags) (int32, error) {
diff --git a/pkg/sentry/kernel/task.go b/pkg/sentry/kernel/task.go
index d6546735e..e5d133d6c 100644
--- a/pkg/sentry/kernel/task.go
+++ b/pkg/sentry/kernel/task.go
@@ -777,6 +777,15 @@ func (t *Task) NewFDs(fd int32, files []*fs.File, flags FDFlags) ([]int32, error
 	return t.fdTable.NewFDs(t, fd, files, flags)
 }
 
+// NewFDsVFS2 is a convenience wrapper for t.FDTable().NewFDsVFS2.
+//
+// This automatically passes the task as the context.
+//
+// Precondition: same as FDTable.
+func (t *Task) NewFDsVFS2(fd int32, files []*vfs.FileDescription, flags FDFlags) ([]int32, error) {
+	return t.fdTable.NewFDsVFS2(t, fd, files, flags)
+}
+
 // NewFDFrom is a convenience wrapper for t.FDTable().NewFDs with a single file.
 //
 // This automatically passes the task as the context.
diff --git a/pkg/sentry/syscalls/linux/sys_socket.go b/pkg/sentry/syscalls/linux/sys_socket.go
index 2919228d0..61b2576ac 100644
--- a/pkg/sentry/syscalls/linux/sys_socket.go
+++ b/pkg/sentry/syscalls/linux/sys_socket.go
@@ -31,6 +31,8 @@ import (
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
+// LINT.IfChange
+
 // minListenBacklog is the minimum reasonable backlog for listening sockets.
 const minListenBacklog = 8
 
@@ -244,7 +246,10 @@ func SocketPair(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 
 	// Copy the file descriptors out.
 	if _, err := t.CopyOut(socks, fds); err != nil {
-		// Note that we don't close files here; see pipe(2) also.
+		for _, fd := range fds {
+			_, file := t.FDTable().Remove(fd)
+			file.DecRef()
+		}
 		return 0, nil, err
 	}
 
@@ -1128,3 +1133,5 @@ func SendTo(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 	n, err := sendTo(t, fd, bufPtr, bufLen, flags, namePtr, nameLen)
 	return n, nil, err
 }
+
+// LINT.ThenChange(./vfs2/socket.go)
diff --git a/pkg/sentry/syscalls/linux/vfs2/linux64_override_amd64.go b/pkg/sentry/syscalls/linux/vfs2/linux64_override_amd64.go
index 63febc2f7..645e0bcb8 100755
--- a/pkg/sentry/syscalls/linux/vfs2/linux64_override_amd64.go
+++ b/pkg/sentry/syscalls/linux/vfs2/linux64_override_amd64.go
@@ -44,21 +44,22 @@ func Override(table map[uintptr]kernel.Syscall) {
 	table[32] = syscalls.Supported("dup", Dup)
 	table[33] = syscalls.Supported("dup2", Dup2)
 	delete(table, 40) // sendfile
-	delete(table, 41) // socket
-	delete(table, 42) // connect
-	delete(table, 43) // accept
-	delete(table, 44) // sendto
-	delete(table, 45) // recvfrom
-	delete(table, 46) // sendmsg
-	delete(table, 47) // recvmsg
-	delete(table, 48) // shutdown
-	delete(table, 49) // bind
-	delete(table, 50) // listen
-	delete(table, 51) // getsockname
-	delete(table, 52) // getpeername
-	delete(table, 53) // socketpair
-	delete(table, 54) // setsockopt
-	delete(table, 55) // getsockopt
+	// TODO(gvisor.dev/issue/1485): Port all socket variants to VFS2.
+	table[41] = syscalls.PartiallySupported("socket", Socket, "In process of porting socket syscalls to VFS2.", nil)
+	table[42] = syscalls.PartiallySupported("connect", Connect, "In process of porting socket syscalls to VFS2.", nil)
+	table[43] = syscalls.PartiallySupported("accept", Accept, "In process of porting socket syscalls to VFS2.", nil)
+	table[44] = syscalls.PartiallySupported("sendto", SendTo, "In process of porting socket syscalls to VFS2.", nil)
+	table[45] = syscalls.PartiallySupported("recvfrom", RecvFrom, "In process of porting socket syscalls to VFS2.", nil)
+	table[46] = syscalls.PartiallySupported("sendmsg", SendMsg, "In process of porting socket syscalls to VFS2.", nil)
+	table[47] = syscalls.PartiallySupported("recvmsg", RecvMsg, "In process of porting socket syscalls to VFS2.", nil)
+	table[48] = syscalls.PartiallySupported("shutdown", Shutdown, "In process of porting socket syscalls to VFS2.", nil)
+	table[49] = syscalls.PartiallySupported("bind", Bind, "In process of porting socket syscalls to VFS2.", nil)
+	table[50] = syscalls.PartiallySupported("listen", Listen, "In process of porting socket syscalls to VFS2.", nil)
+	table[51] = syscalls.PartiallySupported("getsockname", GetSockName, "In process of porting socket syscalls to VFS2.", nil)
+	table[52] = syscalls.PartiallySupported("getpeername", GetPeerName, "In process of porting socket syscalls to VFS2.", nil)
+	table[53] = syscalls.PartiallySupported("socketpair", SocketPair, "In process of porting socket syscalls to VFS2.", nil)
+	table[54] = syscalls.PartiallySupported("getsockopt", GetSockOpt, "In process of porting socket syscalls to VFS2.", nil)
+	table[55] = syscalls.PartiallySupported("setsockopt", SetSockOpt, "In process of porting socket syscalls to VFS2.", nil)
 	table[59] = syscalls.Supported("execve", Execve)
 	table[72] = syscalls.Supported("fcntl", Fcntl)
 	delete(table, 73) // flock
@@ -144,7 +145,8 @@ func Override(table map[uintptr]kernel.Syscall) {
 	delete(table, 285) // fallocate
 	table[286] = syscalls.Supported("timerfd_settime", TimerfdSettime)
 	table[287] = syscalls.Supported("timerfd_gettime", TimerfdGettime)
-	delete(table, 288) // accept4
+	// TODO(gvisor.dev/issue/1485): Port all socket variants to VFS2.
+	table[288] = syscalls.PartiallySupported("accept4", Accept4, "In process of porting socket syscalls to VFS2.", nil)
 	delete(table, 289) // signalfd4
 	delete(table, 290) // eventfd2
 	table[291] = syscalls.Supported("epoll_create1", EpollCreate1)
@@ -153,9 +155,11 @@ func Override(table map[uintptr]kernel.Syscall) {
 	delete(table, 294) // inotify_init1
 	table[295] = syscalls.Supported("preadv", Preadv)
 	table[296] = syscalls.Supported("pwritev", Pwritev)
-	delete(table, 299) // recvmmsg
+	// TODO(gvisor.dev/issue/1485): Port all socket variants to VFS2.
+	table[299] = syscalls.PartiallySupported("recvmmsg", RecvMMsg, "In process of porting socket syscalls to VFS2.", nil)
 	table[306] = syscalls.Supported("syncfs", Syncfs)
-	delete(table, 307) // sendmmsg
+	// TODO(gvisor.dev/issue/1485): Port all socket variants to VFS2.
+	table[307] = syscalls.PartiallySupported("sendmmsg", SendMMsg, "In process of porting socket syscalls to VFS2.", nil)
 	table[316] = syscalls.Supported("renameat2", Renameat2)
 	delete(table, 319) // memfd_create
 	table[322] = syscalls.Supported("execveat", Execveat)
diff --git a/pkg/sentry/syscalls/linux/vfs2/socket.go b/pkg/sentry/syscalls/linux/vfs2/socket.go
new file mode 100755
index 000000000..79a4a7ada
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/vfs2/socket.go
@@ -0,0 +1,1138 @@
+// 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 vfs2
+
+import (
+	"time"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/binary"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
+	"gvisor.dev/gvisor/pkg/sentry/socket"
+	"gvisor.dev/gvisor/pkg/sentry/socket/control"
+	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	slinux "gvisor.dev/gvisor/pkg/sentry/syscalls/linux"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserr"
+	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+// minListenBacklog is the minimum reasonable backlog for listening sockets.
+const minListenBacklog = 8
+
+// maxListenBacklog is the maximum allowed backlog for listening sockets.
+const maxListenBacklog = 1024
+
+// maxAddrLen is the maximum socket address length we're willing to accept.
+const maxAddrLen = 200
+
+// maxOptLen is the maximum sockopt parameter length we're willing to accept.
+const maxOptLen = 1024 * 8
+
+// maxControlLen is the maximum length of the msghdr.msg_control buffer we're
+// willing to accept. Note that this limit is smaller than Linux, which allows
+// buffers upto INT_MAX.
+const maxControlLen = 10 * 1024 * 1024
+
+// nameLenOffset is the offset from the start of the MessageHeader64 struct to
+// the NameLen field.
+const nameLenOffset = 8
+
+// controlLenOffset is the offset form the start of the MessageHeader64 struct
+// to the ControlLen field.
+const controlLenOffset = 40
+
+// flagsOffset is the offset form the start of the MessageHeader64 struct
+// to the Flags field.
+const flagsOffset = 48
+
+const sizeOfInt32 = 4
+
+// messageHeader64Len is the length of a MessageHeader64 struct.
+var messageHeader64Len = uint64(binary.Size(MessageHeader64{}))
+
+// multipleMessageHeader64Len is the length of a multipeMessageHeader64 struct.
+var multipleMessageHeader64Len = uint64(binary.Size(multipleMessageHeader64{}))
+
+// baseRecvFlags are the flags that are accepted across recvmsg(2),
+// recvmmsg(2), and recvfrom(2).
+const baseRecvFlags = linux.MSG_OOB | linux.MSG_DONTROUTE | linux.MSG_DONTWAIT | linux.MSG_NOSIGNAL | linux.MSG_WAITALL | linux.MSG_TRUNC | linux.MSG_CTRUNC
+
+// MessageHeader64 is the 64-bit representation of the msghdr struct used in
+// the recvmsg and sendmsg syscalls.
+type MessageHeader64 struct {
+	// Name is the optional pointer to a network address buffer.
+	Name uint64
+
+	// NameLen is the length of the buffer pointed to by Name.
+	NameLen uint32
+	_       uint32
+
+	// Iov is a pointer to an array of io vectors that describe the memory
+	// locations involved in the io operation.
+	Iov uint64
+
+	// IovLen is the length of the array pointed to by Iov.
+	IovLen uint64
+
+	// Control is the optional pointer to ancillary control data.
+	Control uint64
+
+	// ControlLen is the length of the data pointed to by Control.
+	ControlLen uint64
+
+	// Flags on the sent/received message.
+	Flags int32
+	_     int32
+}
+
+// multipleMessageHeader64 is the 64-bit representation of the mmsghdr struct used in
+// the recvmmsg and sendmmsg syscalls.
+type multipleMessageHeader64 struct {
+	msgHdr MessageHeader64
+	msgLen uint32
+	_      int32
+}
+
+// CopyInMessageHeader64 copies a message header from user to kernel memory.
+func CopyInMessageHeader64(t *kernel.Task, addr usermem.Addr, msg *MessageHeader64) error {
+	b := t.CopyScratchBuffer(52)
+	if _, err := t.CopyInBytes(addr, b); err != nil {
+		return err
+	}
+
+	msg.Name = usermem.ByteOrder.Uint64(b[0:])
+	msg.NameLen = usermem.ByteOrder.Uint32(b[8:])
+	msg.Iov = usermem.ByteOrder.Uint64(b[16:])
+	msg.IovLen = usermem.ByteOrder.Uint64(b[24:])
+	msg.Control = usermem.ByteOrder.Uint64(b[32:])
+	msg.ControlLen = usermem.ByteOrder.Uint64(b[40:])
+	msg.Flags = int32(usermem.ByteOrder.Uint32(b[48:]))
+
+	return nil
+}
+
+// CaptureAddress allocates memory for and copies a socket address structure
+// from the untrusted address space range.
+func CaptureAddress(t *kernel.Task, addr usermem.Addr, addrlen uint32) ([]byte, error) {
+	if addrlen > maxAddrLen {
+		return nil, syserror.EINVAL
+	}
+
+	addrBuf := make([]byte, addrlen)
+	if _, err := t.CopyInBytes(addr, addrBuf); err != nil {
+		return nil, err
+	}
+
+	return addrBuf, nil
+}
+
+// writeAddress writes a sockaddr structure and its length to an output buffer
+// in the unstrusted address space range. If the address is bigger than the
+// buffer, it is truncated.
+func writeAddress(t *kernel.Task, addr interface{}, addrLen uint32, addrPtr usermem.Addr, addrLenPtr usermem.Addr) error {
+	// Get the buffer length.
+	var bufLen uint32
+	if _, err := t.CopyIn(addrLenPtr, &bufLen); err != nil {
+		return err
+	}
+
+	if int32(bufLen) < 0 {
+		return syserror.EINVAL
+	}
+
+	// Write the length unconditionally.
+	if _, err := t.CopyOut(addrLenPtr, addrLen); err != nil {
+		return err
+	}
+
+	if addr == nil {
+		return nil
+	}
+
+	if bufLen > addrLen {
+		bufLen = addrLen
+	}
+
+	// Copy as much of the address as will fit in the buffer.
+	encodedAddr := binary.Marshal(nil, usermem.ByteOrder, addr)
+	if bufLen > uint32(len(encodedAddr)) {
+		bufLen = uint32(len(encodedAddr))
+	}
+	_, err := t.CopyOutBytes(addrPtr, encodedAddr[:int(bufLen)])
+	return err
+}
+
+// Socket implements the linux syscall socket(2).
+func Socket(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	domain := int(args[0].Int())
+	stype := args[1].Int()
+	protocol := int(args[2].Int())
+
+	// Check and initialize the flags.
+	if stype & ^(0xf|linux.SOCK_NONBLOCK|linux.SOCK_CLOEXEC) != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Create the new socket.
+	s, e := socket.NewVFS2(t, domain, linux.SockType(stype&0xf), protocol)
+	if e != nil {
+		return 0, nil, e.ToError()
+	}
+	defer s.DecRef()
+
+	if err := s.SetStatusFlags(t, t.Credentials(), uint32(stype&linux.SOCK_NONBLOCK)); err != nil {
+		return 0, nil, err
+	}
+
+	fd, err := t.NewFDFromVFS2(0, s, kernel.FDFlags{
+		CloseOnExec: stype&linux.SOCK_CLOEXEC != 0,
+	})
+	if err != nil {
+		return 0, nil, err
+	}
+
+	return uintptr(fd), nil, nil
+}
+
+// SocketPair implements the linux syscall socketpair(2).
+func SocketPair(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	domain := int(args[0].Int())
+	stype := args[1].Int()
+	protocol := int(args[2].Int())
+	addr := args[3].Pointer()
+
+	// Check and initialize the flags.
+	if stype & ^(0xf|linux.SOCK_NONBLOCK|linux.SOCK_CLOEXEC) != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Create the socket pair.
+	s1, s2, e := socket.PairVFS2(t, domain, linux.SockType(stype&0xf), protocol)
+	if e != nil {
+		return 0, nil, e.ToError()
+	}
+	// Adding to the FD table will cause an extra reference to be acquired.
+	defer s1.DecRef()
+	defer s2.DecRef()
+
+	nonblocking := uint32(stype & linux.SOCK_NONBLOCK)
+	if err := s1.SetStatusFlags(t, t.Credentials(), nonblocking); err != nil {
+		return 0, nil, err
+	}
+	if err := s2.SetStatusFlags(t, t.Credentials(), nonblocking); err != nil {
+		return 0, nil, err
+	}
+
+	// Create the FDs for the sockets.
+	flags := kernel.FDFlags{
+		CloseOnExec: stype&linux.SOCK_CLOEXEC != 0,
+	}
+	fds, err := t.NewFDsVFS2(0, []*vfs.FileDescription{s1, s2}, flags)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	if _, err := t.CopyOut(addr, fds); err != nil {
+		for _, fd := range fds {
+			_, file := t.FDTable().Remove(fd)
+			file.DecRef()
+		}
+		return 0, nil, err
+	}
+
+	return 0, nil, nil
+}
+
+// Connect implements the linux syscall connect(2).
+func Connect(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	addr := args[1].Pointer()
+	addrlen := args[2].Uint()
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, nil, syserror.ENOTSOCK
+	}
+
+	// Capture address and call syscall implementation.
+	a, err := CaptureAddress(t, addr, addrlen)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	blocking := (file.StatusFlags() & linux.SOCK_NONBLOCK) == 0
+	return 0, nil, syserror.ConvertIntr(s.Connect(t, a, blocking).ToError(), kernel.ERESTARTSYS)
+}
+
+// accept is the implementation of the accept syscall. It is called by accept
+// and accept4 syscall handlers.
+func accept(t *kernel.Task, fd int32, addr usermem.Addr, addrLen usermem.Addr, flags int) (uintptr, error) {
+	// Check that no unsupported flags are passed in.
+	if flags & ^(linux.SOCK_NONBLOCK|linux.SOCK_CLOEXEC) != 0 {
+		return 0, syserror.EINVAL
+	}
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, syserror.ENOTSOCK
+	}
+
+	// Call the syscall implementation for this socket, then copy the
+	// output address if one is specified.
+	blocking := (file.StatusFlags() & linux.SOCK_NONBLOCK) == 0
+
+	peerRequested := addrLen != 0
+	nfd, peer, peerLen, e := s.Accept(t, peerRequested, flags, blocking)
+	if e != nil {
+		return 0, syserror.ConvertIntr(e.ToError(), kernel.ERESTARTSYS)
+	}
+	if peerRequested {
+		// NOTE(magi): Linux does not give you an error if it can't
+		// write the data back out so neither do we.
+		if err := writeAddress(t, peer, peerLen, addr, addrLen); err == syserror.EINVAL {
+			return 0, err
+		}
+	}
+	return uintptr(nfd), nil
+}
+
+// Accept4 implements the linux syscall accept4(2).
+func Accept4(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	addr := args[1].Pointer()
+	addrlen := args[2].Pointer()
+	flags := int(args[3].Int())
+
+	n, err := accept(t, fd, addr, addrlen, flags)
+	return n, nil, err
+}
+
+// Accept implements the linux syscall accept(2).
+func Accept(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	addr := args[1].Pointer()
+	addrlen := args[2].Pointer()
+
+	n, err := accept(t, fd, addr, addrlen, 0)
+	return n, nil, err
+}
+
+// Bind implements the linux syscall bind(2).
+func Bind(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	addr := args[1].Pointer()
+	addrlen := args[2].Uint()
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, nil, syserror.ENOTSOCK
+	}
+
+	// Capture address and call syscall implementation.
+	a, err := CaptureAddress(t, addr, addrlen)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	return 0, nil, s.Bind(t, a).ToError()
+}
+
+// Listen implements the linux syscall listen(2).
+func Listen(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	backlog := args[1].Int()
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, nil, syserror.ENOTSOCK
+	}
+
+	// Per Linux, the backlog is silently capped to reasonable values.
+	if backlog <= 0 {
+		backlog = minListenBacklog
+	}
+	if backlog > maxListenBacklog {
+		backlog = maxListenBacklog
+	}
+
+	return 0, nil, s.Listen(t, int(backlog)).ToError()
+}
+
+// Shutdown implements the linux syscall shutdown(2).
+func Shutdown(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	how := args[1].Int()
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, nil, syserror.ENOTSOCK
+	}
+
+	// Validate how, then call syscall implementation.
+	switch how {
+	case linux.SHUT_RD, linux.SHUT_WR, linux.SHUT_RDWR:
+	default:
+		return 0, nil, syserror.EINVAL
+	}
+
+	return 0, nil, s.Shutdown(t, int(how)).ToError()
+}
+
+// GetSockOpt implements the linux syscall getsockopt(2).
+func GetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	level := args[1].Int()
+	name := args[2].Int()
+	optValAddr := args[3].Pointer()
+	optLenAddr := args[4].Pointer()
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, nil, syserror.ENOTSOCK
+	}
+
+	// Read the length. Reject negative values.
+	optLen := int32(0)
+	if _, err := t.CopyIn(optLenAddr, &optLen); err != nil {
+		return 0, nil, err
+	}
+	if optLen < 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Call syscall implementation then copy both value and value len out.
+	v, e := getSockOpt(t, s, int(level), int(name), optValAddr, int(optLen))
+	if e != nil {
+		return 0, nil, e.ToError()
+	}
+
+	vLen := int32(binary.Size(v))
+	if _, err := t.CopyOut(optLenAddr, vLen); err != nil {
+		return 0, nil, err
+	}
+
+	if v != nil {
+		if _, err := t.CopyOut(optValAddr, v); err != nil {
+			return 0, nil, err
+		}
+	}
+
+	return 0, nil, nil
+}
+
+// getSockOpt tries to handle common socket options, or dispatches to a specific
+// socket implementation.
+func getSockOpt(t *kernel.Task, s socket.SocketVFS2, level, name int, optValAddr usermem.Addr, len int) (interface{}, *syserr.Error) {
+	if level == linux.SOL_SOCKET {
+		switch name {
+		case linux.SO_TYPE, linux.SO_DOMAIN, linux.SO_PROTOCOL:
+			if len < sizeOfInt32 {
+				return nil, syserr.ErrInvalidArgument
+			}
+		}
+
+		switch name {
+		case linux.SO_TYPE:
+			_, skType, _ := s.Type()
+			return int32(skType), nil
+		case linux.SO_DOMAIN:
+			family, _, _ := s.Type()
+			return int32(family), nil
+		case linux.SO_PROTOCOL:
+			_, _, protocol := s.Type()
+			return int32(protocol), nil
+		}
+	}
+
+	return s.GetSockOpt(t, level, name, optValAddr, len)
+}
+
+// SetSockOpt implements the linux syscall setsockopt(2).
+//
+// Note that unlike Linux, enabling SO_PASSCRED does not autobind the socket.
+func SetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	level := args[1].Int()
+	name := args[2].Int()
+	optValAddr := args[3].Pointer()
+	optLen := args[4].Int()
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, nil, syserror.ENOTSOCK
+	}
+
+	if optLen < 0 {
+		return 0, nil, syserror.EINVAL
+	}
+	if optLen > maxOptLen {
+		return 0, nil, syserror.EINVAL
+	}
+	buf := t.CopyScratchBuffer(int(optLen))
+	if _, err := t.CopyIn(optValAddr, &buf); err != nil {
+		return 0, nil, err
+	}
+
+	// Call syscall implementation.
+	if err := s.SetSockOpt(t, int(level), int(name), buf); err != nil {
+		return 0, nil, err.ToError()
+	}
+
+	return 0, nil, nil
+}
+
+// GetSockName implements the linux syscall getsockname(2).
+func GetSockName(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	addr := args[1].Pointer()
+	addrlen := args[2].Pointer()
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, nil, syserror.ENOTSOCK
+	}
+
+	// Get the socket name and copy it to the caller.
+	v, vl, err := s.GetSockName(t)
+	if err != nil {
+		return 0, nil, err.ToError()
+	}
+
+	return 0, nil, writeAddress(t, v, vl, addr, addrlen)
+}
+
+// GetPeerName implements the linux syscall getpeername(2).
+func GetPeerName(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	addr := args[1].Pointer()
+	addrlen := args[2].Pointer()
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, nil, syserror.ENOTSOCK
+	}
+
+	// Get the socket peer name and copy it to the caller.
+	v, vl, err := s.GetPeerName(t)
+	if err != nil {
+		return 0, nil, err.ToError()
+	}
+
+	return 0, nil, writeAddress(t, v, vl, addr, addrlen)
+}
+
+// RecvMsg implements the linux syscall recvmsg(2).
+func RecvMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	msgPtr := args[1].Pointer()
+	flags := args[2].Int()
+
+	if t.Arch().Width() != 8 {
+		// We only handle 64-bit for now.
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, nil, syserror.ENOTSOCK
+	}
+
+	// Reject flags that we don't handle yet.
+	if flags & ^(baseRecvFlags|linux.MSG_PEEK|linux.MSG_CMSG_CLOEXEC|linux.MSG_ERRQUEUE) != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	if (file.StatusFlags() & linux.SOCK_NONBLOCK) != 0 {
+		flags |= linux.MSG_DONTWAIT
+	}
+
+	var haveDeadline bool
+	var deadline ktime.Time
+	if dl := s.RecvTimeout(); dl > 0 {
+		deadline = t.Kernel().MonotonicClock().Now().Add(time.Duration(dl) * time.Nanosecond)
+		haveDeadline = true
+	} else if dl < 0 {
+		flags |= linux.MSG_DONTWAIT
+	}
+
+	n, err := recvSingleMsg(t, s, msgPtr, flags, haveDeadline, deadline)
+	return n, nil, err
+}
+
+// RecvMMsg implements the linux syscall recvmmsg(2).
+func RecvMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	msgPtr := args[1].Pointer()
+	vlen := args[2].Uint()
+	flags := args[3].Int()
+	toPtr := args[4].Pointer()
+
+	if t.Arch().Width() != 8 {
+		// We only handle 64-bit for now.
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Reject flags that we don't handle yet.
+	if flags & ^(baseRecvFlags|linux.MSG_CMSG_CLOEXEC|linux.MSG_ERRQUEUE) != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, nil, syserror.ENOTSOCK
+	}
+
+	if (file.StatusFlags() & linux.SOCK_NONBLOCK) != 0 {
+		flags |= linux.MSG_DONTWAIT
+	}
+
+	var haveDeadline bool
+	var deadline ktime.Time
+	if toPtr != 0 {
+		var ts linux.Timespec
+		if _, err := ts.CopyIn(t, toPtr); err != nil {
+			return 0, nil, err
+		}
+		if !ts.Valid() {
+			return 0, nil, syserror.EINVAL
+		}
+		deadline = t.Kernel().MonotonicClock().Now().Add(ts.ToDuration())
+		haveDeadline = true
+	}
+
+	if !haveDeadline {
+		if dl := s.RecvTimeout(); dl > 0 {
+			deadline = t.Kernel().MonotonicClock().Now().Add(time.Duration(dl) * time.Nanosecond)
+			haveDeadline = true
+		} else if dl < 0 {
+			flags |= linux.MSG_DONTWAIT
+		}
+	}
+
+	var count uint32
+	var err error
+	for i := uint64(0); i < uint64(vlen); i++ {
+		mp, ok := msgPtr.AddLength(i * multipleMessageHeader64Len)
+		if !ok {
+			return 0, nil, syserror.EFAULT
+		}
+		var n uintptr
+		if n, err = recvSingleMsg(t, s, mp, flags, haveDeadline, deadline); err != nil {
+			break
+		}
+
+		// Copy the received length to the caller.
+		lp, ok := mp.AddLength(messageHeader64Len)
+		if !ok {
+			return 0, nil, syserror.EFAULT
+		}
+		if _, err = t.CopyOut(lp, uint32(n)); err != nil {
+			break
+		}
+		count++
+	}
+
+	if count == 0 {
+		return 0, nil, err
+	}
+	return uintptr(count), nil, nil
+}
+
+func recvSingleMsg(t *kernel.Task, s socket.SocketVFS2, msgPtr usermem.Addr, flags int32, haveDeadline bool, deadline ktime.Time) (uintptr, error) {
+	// Capture the message header and io vectors.
+	var msg MessageHeader64
+	if err := CopyInMessageHeader64(t, msgPtr, &msg); err != nil {
+		return 0, err
+	}
+
+	if msg.IovLen > linux.UIO_MAXIOV {
+		return 0, syserror.EMSGSIZE
+	}
+	dst, err := t.IovecsIOSequence(usermem.Addr(msg.Iov), int(msg.IovLen), usermem.IOOpts{
+		AddressSpaceActive: true,
+	})
+	if err != nil {
+		return 0, err
+	}
+
+	// FIXME(b/63594852): Pretend we have an empty error queue.
+	if flags&linux.MSG_ERRQUEUE != 0 {
+		return 0, syserror.EAGAIN
+	}
+
+	// Fast path when no control message nor name buffers are provided.
+	if msg.ControlLen == 0 && msg.NameLen == 0 {
+		n, mflags, _, _, cms, err := s.RecvMsg(t, dst, int(flags), haveDeadline, deadline, false, 0)
+		if err != nil {
+			return 0, syserror.ConvertIntr(err.ToError(), kernel.ERESTARTSYS)
+		}
+		if !cms.Unix.Empty() {
+			mflags |= linux.MSG_CTRUNC
+			cms.Release()
+		}
+
+		if int(msg.Flags) != mflags {
+			// Copy out the flags to the caller.
+			if _, err := t.CopyOut(msgPtr+flagsOffset, int32(mflags)); err != nil {
+				return 0, err
+			}
+		}
+
+		return uintptr(n), nil
+	}
+
+	if msg.ControlLen > maxControlLen {
+		return 0, syserror.ENOBUFS
+	}
+	n, mflags, sender, senderLen, cms, e := s.RecvMsg(t, dst, int(flags), haveDeadline, deadline, msg.NameLen != 0, msg.ControlLen)
+	if e != nil {
+		return 0, syserror.ConvertIntr(e.ToError(), kernel.ERESTARTSYS)
+	}
+	defer cms.Release()
+
+	controlData := make([]byte, 0, msg.ControlLen)
+	controlData = control.PackControlMessages(t, cms, controlData)
+
+	if cr, ok := s.(transport.Credentialer); ok && cr.Passcred() {
+		creds, _ := cms.Unix.Credentials.(control.SCMCredentials)
+		controlData, mflags = control.PackCredentials(t, creds, controlData, mflags)
+	}
+
+	if cms.Unix.Rights != nil {
+		controlData, mflags = control.PackRights(t, cms.Unix.Rights.(control.SCMRights), flags&linux.MSG_CMSG_CLOEXEC != 0, controlData, mflags)
+	}
+
+	// Copy the address to the caller.
+	if msg.NameLen != 0 {
+		if err := writeAddress(t, sender, senderLen, usermem.Addr(msg.Name), usermem.Addr(msgPtr+nameLenOffset)); err != nil {
+			return 0, err
+		}
+	}
+
+	// Copy the control data to the caller.
+	if _, err := t.CopyOut(msgPtr+controlLenOffset, uint64(len(controlData))); err != nil {
+		return 0, err
+	}
+	if len(controlData) > 0 {
+		if _, err := t.CopyOut(usermem.Addr(msg.Control), controlData); err != nil {
+			return 0, err
+		}
+	}
+
+	// Copy out the flags to the caller.
+	if _, err := t.CopyOut(msgPtr+flagsOffset, int32(mflags)); err != nil {
+		return 0, err
+	}
+
+	return uintptr(n), nil
+}
+
+// recvFrom is the implementation of the recvfrom syscall. It is called by
+// recvfrom and recv syscall handlers.
+func recvFrom(t *kernel.Task, fd int32, bufPtr usermem.Addr, bufLen uint64, flags int32, namePtr usermem.Addr, nameLenPtr usermem.Addr) (uintptr, error) {
+	if int(bufLen) < 0 {
+		return 0, syserror.EINVAL
+	}
+
+	// Reject flags that we don't handle yet.
+	if flags & ^(baseRecvFlags|linux.MSG_PEEK|linux.MSG_CONFIRM) != 0 {
+		return 0, syserror.EINVAL
+	}
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, syserror.ENOTSOCK
+	}
+
+	if (file.StatusFlags() & linux.SOCK_NONBLOCK) != 0 {
+		flags |= linux.MSG_DONTWAIT
+	}
+
+	dst, err := t.SingleIOSequence(bufPtr, int(bufLen), usermem.IOOpts{
+		AddressSpaceActive: true,
+	})
+	if err != nil {
+		return 0, err
+	}
+
+	var haveDeadline bool
+	var deadline ktime.Time
+	if dl := s.RecvTimeout(); dl > 0 {
+		deadline = t.Kernel().MonotonicClock().Now().Add(time.Duration(dl) * time.Nanosecond)
+		haveDeadline = true
+	} else if dl < 0 {
+		flags |= linux.MSG_DONTWAIT
+	}
+
+	n, _, sender, senderLen, cm, e := s.RecvMsg(t, dst, int(flags), haveDeadline, deadline, nameLenPtr != 0, 0)
+	cm.Release()
+	if e != nil {
+		return 0, syserror.ConvertIntr(e.ToError(), kernel.ERESTARTSYS)
+	}
+
+	// Copy the address to the caller.
+	if nameLenPtr != 0 {
+		if err := writeAddress(t, sender, senderLen, namePtr, nameLenPtr); err != nil {
+			return 0, err
+		}
+	}
+
+	return uintptr(n), nil
+}
+
+// RecvFrom implements the linux syscall recvfrom(2).
+func RecvFrom(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	bufPtr := args[1].Pointer()
+	bufLen := args[2].Uint64()
+	flags := args[3].Int()
+	namePtr := args[4].Pointer()
+	nameLenPtr := args[5].Pointer()
+
+	n, err := recvFrom(t, fd, bufPtr, bufLen, flags, namePtr, nameLenPtr)
+	return n, nil, err
+}
+
+// SendMsg implements the linux syscall sendmsg(2).
+func SendMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	msgPtr := args[1].Pointer()
+	flags := args[2].Int()
+
+	if t.Arch().Width() != 8 {
+		// We only handle 64-bit for now.
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, nil, syserror.ENOTSOCK
+	}
+
+	// Reject flags that we don't handle yet.
+	if flags & ^(linux.MSG_DONTWAIT|linux.MSG_EOR|linux.MSG_MORE|linux.MSG_NOSIGNAL) != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	if (file.StatusFlags() & linux.SOCK_NONBLOCK) != 0 {
+		flags |= linux.MSG_DONTWAIT
+	}
+
+	n, err := sendSingleMsg(t, s, file, msgPtr, flags)
+	return n, nil, err
+}
+
+// SendMMsg implements the linux syscall sendmmsg(2).
+func SendMMsg(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	msgPtr := args[1].Pointer()
+	vlen := args[2].Uint()
+	flags := args[3].Int()
+
+	if t.Arch().Width() != 8 {
+		// We only handle 64-bit for now.
+		return 0, nil, syserror.EINVAL
+	}
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, nil, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, nil, syserror.ENOTSOCK
+	}
+
+	// Reject flags that we don't handle yet.
+	if flags & ^(linux.MSG_DONTWAIT|linux.MSG_EOR|linux.MSG_MORE|linux.MSG_NOSIGNAL) != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	if (file.StatusFlags() & linux.SOCK_NONBLOCK) != 0 {
+		flags |= linux.MSG_DONTWAIT
+	}
+
+	var count uint32
+	var err error
+	for i := uint64(0); i < uint64(vlen); i++ {
+		mp, ok := msgPtr.AddLength(i * multipleMessageHeader64Len)
+		if !ok {
+			return 0, nil, syserror.EFAULT
+		}
+		var n uintptr
+		if n, err = sendSingleMsg(t, s, file, mp, flags); err != nil {
+			break
+		}
+
+		// Copy the received length to the caller.
+		lp, ok := mp.AddLength(messageHeader64Len)
+		if !ok {
+			return 0, nil, syserror.EFAULT
+		}
+		if _, err = t.CopyOut(lp, uint32(n)); err != nil {
+			break
+		}
+		count++
+	}
+
+	if count == 0 {
+		return 0, nil, err
+	}
+	return uintptr(count), nil, nil
+}
+
+func sendSingleMsg(t *kernel.Task, s socket.SocketVFS2, file *vfs.FileDescription, msgPtr usermem.Addr, flags int32) (uintptr, error) {
+	// Capture the message header.
+	var msg MessageHeader64
+	if err := CopyInMessageHeader64(t, msgPtr, &msg); err != nil {
+		return 0, err
+	}
+
+	var controlData []byte
+	if msg.ControlLen > 0 {
+		// Put an upper bound to prevent large allocations.
+		if msg.ControlLen > maxControlLen {
+			return 0, syserror.ENOBUFS
+		}
+		controlData = make([]byte, msg.ControlLen)
+		if _, err := t.CopyIn(usermem.Addr(msg.Control), &controlData); err != nil {
+			return 0, err
+		}
+	}
+
+	// Read the destination address if one is specified.
+	var to []byte
+	if msg.NameLen != 0 {
+		var err error
+		to, err = CaptureAddress(t, usermem.Addr(msg.Name), msg.NameLen)
+		if err != nil {
+			return 0, err
+		}
+	}
+
+	// Read data then call the sendmsg implementation.
+	if msg.IovLen > linux.UIO_MAXIOV {
+		return 0, syserror.EMSGSIZE
+	}
+	src, err := t.IovecsIOSequence(usermem.Addr(msg.Iov), int(msg.IovLen), usermem.IOOpts{
+		AddressSpaceActive: true,
+	})
+	if err != nil {
+		return 0, err
+	}
+
+	controlMessages, err := control.Parse(t, s, controlData)
+	if err != nil {
+		return 0, err
+	}
+
+	var haveDeadline bool
+	var deadline ktime.Time
+	if dl := s.SendTimeout(); dl > 0 {
+		deadline = t.Kernel().MonotonicClock().Now().Add(time.Duration(dl) * time.Nanosecond)
+		haveDeadline = true
+	} else if dl < 0 {
+		flags |= linux.MSG_DONTWAIT
+	}
+
+	// Call the syscall implementation.
+	n, e := s.SendMsg(t, src, to, int(flags), haveDeadline, deadline, controlMessages)
+	err = slinux.HandleIOErrorVFS2(t, n != 0, e.ToError(), kernel.ERESTARTSYS, "sendmsg", file)
+	if err != nil {
+		controlMessages.Release()
+	}
+	return uintptr(n), err
+}
+
+// sendTo is the implementation of the sendto syscall. It is called by sendto
+// and send syscall handlers.
+func sendTo(t *kernel.Task, fd int32, bufPtr usermem.Addr, bufLen uint64, flags int32, namePtr usermem.Addr, nameLen uint32) (uintptr, error) {
+	bl := int(bufLen)
+	if bl < 0 {
+		return 0, syserror.EINVAL
+	}
+
+	// Get socket from the file descriptor.
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		return 0, syserror.EBADF
+	}
+	defer file.DecRef()
+
+	// Extract the socket.
+	s, ok := file.Impl().(socket.SocketVFS2)
+	if !ok {
+		return 0, syserror.ENOTSOCK
+	}
+
+	if (file.StatusFlags() & linux.SOCK_NONBLOCK) != 0 {
+		flags |= linux.MSG_DONTWAIT
+	}
+
+	// Read the destination address if one is specified.
+	var to []byte
+	var err error
+	if namePtr != 0 {
+		to, err = CaptureAddress(t, namePtr, nameLen)
+		if err != nil {
+			return 0, err
+		}
+	}
+
+	src, err := t.SingleIOSequence(bufPtr, bl, usermem.IOOpts{
+		AddressSpaceActive: true,
+	})
+	if err != nil {
+		return 0, err
+	}
+
+	var haveDeadline bool
+	var deadline ktime.Time
+	if dl := s.SendTimeout(); dl > 0 {
+		deadline = t.Kernel().MonotonicClock().Now().Add(time.Duration(dl) * time.Nanosecond)
+		haveDeadline = true
+	} else if dl < 0 {
+		flags |= linux.MSG_DONTWAIT
+	}
+
+	// Call the syscall implementation.
+	n, e := s.SendMsg(t, src, to, int(flags), haveDeadline, deadline, socket.ControlMessages{Unix: control.New(t, s, nil)})
+	return uintptr(n), slinux.HandleIOErrorVFS2(t, n != 0, e.ToError(), kernel.ERESTARTSYS, "sendto", file)
+}
+
+// SendTo implements the linux syscall sendto(2).
+func SendTo(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	fd := args[0].Int()
+	bufPtr := args[1].Pointer()
+	bufLen := args[2].Uint64()
+	flags := args[3].Int()
+	namePtr := args[4].Pointer()
+	nameLen := args[5].Uint()
+
+	n, err := sendTo(t, fd, bufPtr, bufLen, flags, namePtr, nameLen)
+	return n, nil, err
+}