Merge release-20200804.0-27-g35312a95c (automated)

10 files changed, 326 insertions, 13 deletions

diff --git a/pkg/abi/linux/linux_abi_autogen_unsafe.go b/pkg/abi/linux/linux_abi_autogen_unsafe.go
index c3a167228..ffc0b7833 100644
--- a/pkg/abi/linux/linux_abi_autogen_unsafe.go
+++ b/pkg/abi/linux/linux_abi_autogen_unsafe.go
@@ -145,7 +145,7 @@ func (s *Statx) UnmarshalBytes(src []byte) {
 // Packed implements marshal.Marshallable.Packed.
 //go:nosplit
 func (s *Statx) Packed() bool {
-    return s.Ctime.Packed() && s.Mtime.Packed() && s.Atime.Packed() && s.Btime.Packed()
+    return s.Atime.Packed() && s.Btime.Packed() && s.Ctime.Packed() && s.Mtime.Packed()
 }
 
 // MarshalUnsafe implements marshal.Marshallable.MarshalUnsafe.
@@ -171,7 +171,7 @@ func (s *Statx) UnmarshalUnsafe(src []byte) {
 // CopyOutN implements marshal.Marshallable.CopyOutN.
 //go:nosplit
 func (s *Statx) CopyOutN(task marshal.Task, addr usermem.Addr, limit int) (int, error) {
-    if !s.Btime.Packed() && s.Ctime.Packed() && s.Mtime.Packed() && s.Atime.Packed() {
+    if !s.Ctime.Packed() && s.Mtime.Packed() && s.Atime.Packed() && s.Btime.Packed() {
         // Type Statx doesn't have a packed layout in memory, fall back to MarshalBytes.
         buf := task.CopyScratchBuffer(s.SizeBytes()) // escapes: okay.
         s.MarshalBytes(buf) // escapes: fallback.
@@ -201,7 +201,7 @@ func (s *Statx) CopyOut(task marshal.Task, addr usermem.Addr) (int, error) {
 // CopyIn implements marshal.Marshallable.CopyIn.
 //go:nosplit
 func (s *Statx) CopyIn(task marshal.Task, addr usermem.Addr) (int, error) {
-    if !s.Btime.Packed() && s.Ctime.Packed() && s.Mtime.Packed() && s.Atime.Packed() {
+    if !s.Atime.Packed() && s.Btime.Packed() && s.Ctime.Packed() && s.Mtime.Packed() {
         // Type Statx doesn't have a packed layout in memory, fall back to UnmarshalBytes.
         buf := task.CopyScratchBuffer(s.SizeBytes()) // escapes: okay.
         length, err := task.CopyInBytes(addr, buf) // escapes: okay.
@@ -625,7 +625,7 @@ func (f *FUSEHeaderIn) Packed() bool {
 
 // MarshalUnsafe implements marshal.Marshallable.MarshalUnsafe.
 func (f *FUSEHeaderIn) MarshalUnsafe(dst []byte) {
-    if f.Unique.Packed() && f.Opcode.Packed() {
+    if f.Opcode.Packed() && f.Unique.Packed() {
         safecopy.CopyIn(dst, unsafe.Pointer(f))
     } else {
         // Type FUSEHeaderIn doesn't have a packed layout in memory, fallback to MarshalBytes.
@@ -635,7 +635,7 @@ func (f *FUSEHeaderIn) MarshalUnsafe(dst []byte) {
 
 // UnmarshalUnsafe implements marshal.Marshallable.UnmarshalUnsafe.
 func (f *FUSEHeaderIn) UnmarshalUnsafe(src []byte) {
-    if f.Unique.Packed() && f.Opcode.Packed() {
+    if f.Opcode.Packed() && f.Unique.Packed() {
         safecopy.CopyOut(unsafe.Pointer(f), src)
     } else {
         // Type FUSEHeaderIn doesn't have a packed layout in memory, fallback to UnmarshalBytes.
@@ -646,7 +646,7 @@ func (f *FUSEHeaderIn) UnmarshalUnsafe(src []byte) {
 // CopyOutN implements marshal.Marshallable.CopyOutN.
 //go:nosplit
 func (f *FUSEHeaderIn) CopyOutN(task marshal.Task, addr usermem.Addr, limit int) (int, error) {
-    if !f.Opcode.Packed() && f.Unique.Packed() {
+    if !f.Unique.Packed() && f.Opcode.Packed() {
         // Type FUSEHeaderIn doesn't have a packed layout in memory, fall back to MarshalBytes.
         buf := task.CopyScratchBuffer(f.SizeBytes()) // escapes: okay.
         f.MarshalBytes(buf) // escapes: fallback.
@@ -676,7 +676,7 @@ func (f *FUSEHeaderIn) CopyOut(task marshal.Task, addr usermem.Addr) (int, error
 // CopyIn implements marshal.Marshallable.CopyIn.
 //go:nosplit
 func (f *FUSEHeaderIn) CopyIn(task marshal.Task, addr usermem.Addr) (int, error) {
-    if !f.Unique.Packed() && f.Opcode.Packed() {
+    if !f.Opcode.Packed() && f.Unique.Packed() {
         // Type FUSEHeaderIn doesn't have a packed layout in memory, fall back to UnmarshalBytes.
         buf := task.CopyScratchBuffer(f.SizeBytes()) // escapes: okay.
         length, err := task.CopyInBytes(addr, buf) // escapes: okay.
@@ -1635,7 +1635,7 @@ func (i *IPTEntry) Packed() bool {
 
 // MarshalUnsafe implements marshal.Marshallable.MarshalUnsafe.
 func (i *IPTEntry) MarshalUnsafe(dst []byte) {
-    if i.IP.Packed() && i.Counters.Packed() {
+    if i.Counters.Packed() && i.IP.Packed() {
         safecopy.CopyIn(dst, unsafe.Pointer(i))
     } else {
         // Type IPTEntry doesn't have a packed layout in memory, fallback to MarshalBytes.
@@ -1645,7 +1645,7 @@ func (i *IPTEntry) MarshalUnsafe(dst []byte) {
 
 // UnmarshalUnsafe implements marshal.Marshallable.UnmarshalUnsafe.
 func (i *IPTEntry) UnmarshalUnsafe(src []byte) {
-    if i.Counters.Packed() && i.IP.Packed() {
+    if i.IP.Packed() && i.Counters.Packed() {
         safecopy.CopyOut(unsafe.Pointer(i), src)
     } else {
         // Type IPTEntry doesn't have a packed layout in memory, fallback to UnmarshalBytes.
@@ -1656,7 +1656,7 @@ func (i *IPTEntry) UnmarshalUnsafe(src []byte) {
 // CopyOutN implements marshal.Marshallable.CopyOutN.
 //go:nosplit
 func (i *IPTEntry) CopyOutN(task marshal.Task, addr usermem.Addr, limit int) (int, error) {
-    if !i.Counters.Packed() && i.IP.Packed() {
+    if !i.IP.Packed() && i.Counters.Packed() {
         // Type IPTEntry doesn't have a packed layout in memory, fall back to MarshalBytes.
         buf := task.CopyScratchBuffer(i.SizeBytes()) // escapes: okay.
         i.MarshalBytes(buf) // escapes: fallback.
@@ -1833,7 +1833,7 @@ func (i *IPTIP) MarshalUnsafe(dst []byte) {
 
 // UnmarshalUnsafe implements marshal.Marshallable.UnmarshalUnsafe.
 func (i *IPTIP) UnmarshalUnsafe(src []byte) {
-    if i.SrcMask.Packed() && i.DstMask.Packed() && i.Src.Packed() && i.Dst.Packed() {
+    if i.Src.Packed() && i.Dst.Packed() && i.SrcMask.Packed() && i.DstMask.Packed() {
         safecopy.CopyOut(unsafe.Pointer(i), src)
     } else {
         // Type IPTIP doesn't have a packed layout in memory, fallback to UnmarshalBytes.
@@ -1844,7 +1844,7 @@ func (i *IPTIP) UnmarshalUnsafe(src []byte) {
 // CopyOutN implements marshal.Marshallable.CopyOutN.
 //go:nosplit
 func (i *IPTIP) CopyOutN(task marshal.Task, addr usermem.Addr, limit int) (int, error) {
-    if !i.Src.Packed() && i.Dst.Packed() && i.SrcMask.Packed() && i.DstMask.Packed() {
+    if !i.Dst.Packed() && i.SrcMask.Packed() && i.DstMask.Packed() && i.Src.Packed() {
         // Type IPTIP doesn't have a packed layout in memory, fall back to MarshalBytes.
         buf := task.CopyScratchBuffer(i.SizeBytes()) // escapes: okay.
         i.MarshalBytes(buf) // escapes: fallback.
diff --git a/pkg/sentry/fs/proc/proc_state_autogen.go b/pkg/sentry/fs/proc/proc_state_autogen.go
index 87c979909..37ce12115 100644
--- a/pkg/sentry/fs/proc/proc_state_autogen.go
+++ b/pkg/sentry/fs/proc/proc_state_autogen.go
@@ -821,6 +821,61 @@ func (x *tcpSackFile) StateLoad(m state.Source) {
 	m.LoadWait(1, &x.stack)
 }
 
+func (x *tcpRecovery) StateTypeName() string {
+	return "pkg/sentry/fs/proc.tcpRecovery"
+}
+
+func (x *tcpRecovery) StateFields() []string {
+	return []string{
+		"SimpleFileInode",
+		"stack",
+		"recovery",
+	}
+}
+
+func (x *tcpRecovery) beforeSave() {}
+
+func (x *tcpRecovery) StateSave(m state.Sink) {
+	x.beforeSave()
+	m.Save(0, &x.SimpleFileInode)
+	m.Save(1, &x.stack)
+	m.Save(2, &x.recovery)
+}
+
+func (x *tcpRecovery) afterLoad() {}
+
+func (x *tcpRecovery) StateLoad(m state.Source) {
+	m.Load(0, &x.SimpleFileInode)
+	m.LoadWait(1, &x.stack)
+	m.Load(2, &x.recovery)
+}
+
+func (x *tcpRecoveryFile) StateTypeName() string {
+	return "pkg/sentry/fs/proc.tcpRecoveryFile"
+}
+
+func (x *tcpRecoveryFile) StateFields() []string {
+	return []string{
+		"tcpRecovery",
+		"stack",
+	}
+}
+
+func (x *tcpRecoveryFile) beforeSave() {}
+
+func (x *tcpRecoveryFile) StateSave(m state.Sink) {
+	x.beforeSave()
+	m.Save(0, &x.tcpRecovery)
+	m.Save(1, &x.stack)
+}
+
+func (x *tcpRecoveryFile) afterLoad() {}
+
+func (x *tcpRecoveryFile) StateLoad(m state.Source) {
+	m.Load(0, &x.tcpRecovery)
+	m.LoadWait(1, &x.stack)
+}
+
 func (x *taskDir) StateTypeName() string {
 	return "pkg/sentry/fs/proc.taskDir"
 }
@@ -1410,6 +1465,8 @@ func init() {
 	state.Register((*tcpMemFile)(nil))
 	state.Register((*tcpSack)(nil))
 	state.Register((*tcpSackFile)(nil))
+	state.Register((*tcpRecovery)(nil))
+	state.Register((*tcpRecoveryFile)(nil))
 	state.Register((*taskDir)(nil))
 	state.Register((*subtasks)(nil))
 	state.Register((*subtasksFile)(nil))
diff --git a/pkg/sentry/fs/proc/sys_net.go b/pkg/sentry/fs/proc/sys_net.go
index 702fdd392..8615b60f0 100644
--- a/pkg/sentry/fs/proc/sys_net.go
+++ b/pkg/sentry/fs/proc/sys_net.go
@@ -272,6 +272,96 @@ func (f *tcpSackFile) Write(ctx context.Context, _ *fs.File, src usermem.IOSeque
 	return n, f.tcpSack.stack.SetTCPSACKEnabled(*f.tcpSack.enabled)
 }
 
+// +stateify savable
+type tcpRecovery struct {
+	fsutil.SimpleFileInode
+
+	stack    inet.Stack `state:"wait"`
+	recovery inet.TCPLossRecovery
+}
+
+func newTCPRecoveryInode(ctx context.Context, msrc *fs.MountSource, s inet.Stack) *fs.Inode {
+	ts := &tcpRecovery{
+		SimpleFileInode: *fsutil.NewSimpleFileInode(ctx, fs.RootOwner, fs.FilePermsFromMode(0644), linux.PROC_SUPER_MAGIC),
+		stack:           s,
+	}
+	sattr := fs.StableAttr{
+		DeviceID:  device.ProcDevice.DeviceID(),
+		InodeID:   device.ProcDevice.NextIno(),
+		BlockSize: usermem.PageSize,
+		Type:      fs.SpecialFile,
+	}
+	return fs.NewInode(ctx, ts, msrc, sattr)
+}
+
+// Truncate implements fs.InodeOperations.Truncate.
+func (*tcpRecovery) Truncate(context.Context, *fs.Inode, int64) error {
+	return nil
+}
+
+// GetFile implements fs.InodeOperations.GetFile.
+func (r *tcpRecovery) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
+	flags.Pread = true
+	flags.Pwrite = true
+	return fs.NewFile(ctx, dirent, flags, &tcpRecoveryFile{
+		tcpRecovery: r,
+		stack:       r.stack,
+	}), nil
+}
+
+// +stateify savable
+type tcpRecoveryFile struct {
+	fsutil.FileGenericSeek          `state:"nosave"`
+	fsutil.FileNoIoctl              `state:"nosave"`
+	fsutil.FileNoMMap               `state:"nosave"`
+	fsutil.FileNoSplice             `state:"nosave"`
+	fsutil.FileNoopRelease          `state:"nosave"`
+	fsutil.FileNoopFlush            `state:"nosave"`
+	fsutil.FileNoopFsync            `state:"nosave"`
+	fsutil.FileNotDirReaddir        `state:"nosave"`
+	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
+	waiter.AlwaysReady              `state:"nosave"`
+
+	tcpRecovery *tcpRecovery
+
+	stack inet.Stack `state:"wait"`
+}
+
+// Read implements fs.FileOperations.Read.
+func (f *tcpRecoveryFile) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
+	if offset != 0 {
+		return 0, io.EOF
+	}
+
+	recovery, err := f.stack.TCPRecovery()
+	if err != nil {
+		return 0, err
+	}
+	f.tcpRecovery.recovery = recovery
+	s := fmt.Sprintf("%d\n", f.tcpRecovery.recovery)
+	n, err := dst.CopyOut(ctx, []byte(s))
+	return int64(n), err
+}
+
+// Write implements fs.FileOperations.Write.
+func (f *tcpRecoveryFile) Write(ctx context.Context, _ *fs.File, src usermem.IOSequence, offset int64) (int64, error) {
+	if src.NumBytes() == 0 {
+		return 0, nil
+	}
+	src = src.TakeFirst(usermem.PageSize - 1)
+
+	var v int32
+	n, err := usermem.CopyInt32StringInVec(ctx, src.IO, src.Addrs, &v, src.Opts)
+	if err != nil {
+		return 0, err
+	}
+	f.tcpRecovery.recovery = inet.TCPLossRecovery(v)
+	if err := f.tcpRecovery.stack.SetTCPRecovery(f.tcpRecovery.recovery); err != nil {
+		return 0, err
+	}
+	return n, nil
+}
+
 func (p *proc) newSysNetCore(ctx context.Context, msrc *fs.MountSource, s inet.Stack) *fs.Inode {
 	// The following files are simple stubs until they are implemented in
 	// netstack, most of these files are configuration related. We use the
@@ -351,6 +441,11 @@ func (p *proc) newSysNetIPv4Dir(ctx context.Context, msrc *fs.MountSource, s ine
 		contents["tcp_wmem"] = newTCPMemInode(ctx, msrc, s, tcpWMem)
 	}
 
+	// Add tcp_recovery.
+	if _, err := s.TCPRecovery(); err == nil {
+		contents["tcp_recovery"] = newTCPRecoveryInode(ctx, msrc, s)
+	}
+
 	d := ramfs.NewDir(ctx, contents, fs.RootOwner, fs.FilePermsFromMode(0555))
 	return newProcInode(ctx, d, msrc, fs.SpecialDirectory, nil)
 }
diff --git a/pkg/sentry/fsimpl/proc/proc_state_autogen.go b/pkg/sentry/fsimpl/proc/proc_state_autogen.go
index e297a6257..eca33249c 100644
--- a/pkg/sentry/fsimpl/proc/proc_state_autogen.go
+++ b/pkg/sentry/fsimpl/proc/proc_state_autogen.go
@@ -1173,6 +1173,32 @@ func (x *tcpSackData) StateLoad(m state.Source) {
 	m.Load(2, &x.enabled)
 }
 
+func (x *tcpRecoveryData) StateTypeName() string {
+	return "pkg/sentry/fsimpl/proc.tcpRecoveryData"
+}
+
+func (x *tcpRecoveryData) StateFields() []string {
+	return []string{
+		"DynamicBytesFile",
+		"stack",
+	}
+}
+
+func (x *tcpRecoveryData) beforeSave() {}
+
+func (x *tcpRecoveryData) StateSave(m state.Sink) {
+	x.beforeSave()
+	m.Save(0, &x.DynamicBytesFile)
+	m.Save(1, &x.stack)
+}
+
+func (x *tcpRecoveryData) afterLoad() {}
+
+func (x *tcpRecoveryData) StateLoad(m state.Source) {
+	m.Load(0, &x.DynamicBytesFile)
+	m.LoadWait(1, &x.stack)
+}
+
 func init() {
 	state.Register((*FilesystemType)(nil))
 	state.Register((*subtasksInode)(nil))
@@ -1215,4 +1241,5 @@ func init() {
 	state.Register((*mmapMinAddrData)(nil))
 	state.Register((*hostnameData)(nil))
 	state.Register((*tcpSackData)(nil))
+	state.Register((*tcpRecoveryData)(nil))
 }
diff --git a/pkg/sentry/fsimpl/proc/tasks_sys.go b/pkg/sentry/fsimpl/proc/tasks_sys.go
index 6dac2afa4..b71778128 100644
--- a/pkg/sentry/fsimpl/proc/tasks_sys.go
+++ b/pkg/sentry/fsimpl/proc/tasks_sys.go
@@ -55,7 +55,8 @@ func (fs *filesystem) newSysNetDir(root *auth.Credentials, k *kernel.Kernel) *ke
 	if stack := k.RootNetworkNamespace().Stack(); stack != nil {
 		contents = map[string]*kernfs.Dentry{
 			"ipv4": kernfs.NewStaticDir(root, linux.UNNAMED_MAJOR, fs.devMinor, fs.NextIno(), 0555, map[string]*kernfs.Dentry{
-				"tcp_sack": fs.newDentry(root, fs.NextIno(), 0644, &tcpSackData{stack: stack}),
+				"tcp_recovery": fs.newDentry(root, fs.NextIno(), 0644, &tcpRecoveryData{stack: stack}),
+				"tcp_sack":     fs.newDentry(root, fs.NextIno(), 0644, &tcpSackData{stack: stack}),
 
 				// The following files are simple stubs until they are implemented in
 				// netstack, most of these files are configuration related. We use the
@@ -207,3 +208,49 @@ func (d *tcpSackData) Write(ctx context.Context, src usermem.IOSequence, offset
 	*d.enabled = v != 0
 	return n, d.stack.SetTCPSACKEnabled(*d.enabled)
 }
+
+// tcpRecoveryData implements vfs.WritableDynamicBytesSource for
+// /proc/sys/net/ipv4/tcp_recovery.
+//
+// +stateify savable
+type tcpRecoveryData struct {
+	kernfs.DynamicBytesFile
+
+	stack inet.Stack `state:"wait"`
+}
+
+var _ vfs.WritableDynamicBytesSource = (*tcpRecoveryData)(nil)
+
+// Generate implements vfs.DynamicBytesSource.
+func (d *tcpRecoveryData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+	recovery, err := d.stack.TCPRecovery()
+	if err != nil {
+		return err
+	}
+
+	buf.WriteString(fmt.Sprintf("%d\n", recovery))
+	return nil
+}
+
+func (d *tcpRecoveryData) Write(ctx context.Context, src usermem.IOSequence, offset int64) (int64, error) {
+	if offset != 0 {
+		// No need to handle partial writes thus far.
+		return 0, syserror.EINVAL
+	}
+	if src.NumBytes() == 0 {
+		return 0, nil
+	}
+
+	// Limit the amount of memory allocated.
+	src = src.TakeFirst(usermem.PageSize - 1)
+
+	var v int32
+	n, err := usermem.CopyInt32StringInVec(ctx, src.IO, src.Addrs, &v, src.Opts)
+	if err != nil {
+		return 0, err
+	}
+	if err := d.stack.SetTCPRecovery(inet.TCPLossRecovery(v)); err != nil {
+		return 0, err
+	}
+	return n, nil
+}
diff --git a/pkg/sentry/inet/inet.go b/pkg/sentry/inet/inet.go
index 2916a0644..c0b4831d1 100644
--- a/pkg/sentry/inet/inet.go
+++ b/pkg/sentry/inet/inet.go
@@ -56,6 +56,12 @@ type Stack interface {
 	// settings.
 	SetTCPSACKEnabled(enabled bool) error
 
+	// TCPRecovery returns the TCP loss detection algorithm.
+	TCPRecovery() (TCPLossRecovery, error)
+
+	// SetTCPRecovery attempts to change TCP loss detection algorithm.
+	SetTCPRecovery(recovery TCPLossRecovery) error
+
 	// Statistics reports stack statistics.
 	Statistics(stat interface{}, arg string) error
 
@@ -189,3 +195,14 @@ type StatSNMPUDP [8]uint64
 
 // StatSNMPUDPLite describes UdpLite line of /proc/net/snmp.
 type StatSNMPUDPLite [8]uint64
+
+// TCPLossRecovery indicates TCP loss detection and recovery methods to use.
+type TCPLossRecovery int32
+
+// Loss recovery constants from include/net/tcp.h which are used to set
+// /proc/sys/net/ipv4/tcp_recovery.
+const (
+	TCP_RACK_LOSS_DETECTION TCPLossRecovery = 1 << iota
+	TCP_RACK_STATIC_REO_WND
+	TCP_RACK_NO_DUPTHRESH
+)
diff --git a/pkg/sentry/inet/test_stack.go b/pkg/sentry/inet/test_stack.go
index d8961fc94..9771f01fc 100644
--- a/pkg/sentry/inet/test_stack.go
+++ b/pkg/sentry/inet/test_stack.go
@@ -25,6 +25,7 @@ type TestStack struct {
 	TCPRecvBufSize    TCPBufferSize
 	TCPSendBufSize    TCPBufferSize
 	TCPSACKFlag       bool
+	Recovery          TCPLossRecovery
 }
 
 // NewTestStack returns a TestStack with no network interfaces. The value of
@@ -91,6 +92,17 @@ func (s *TestStack) SetTCPSACKEnabled(enabled bool) error {
 	return nil
 }
 
+// TCPRecovery implements Stack.TCPRecovery.
+func (s *TestStack) TCPRecovery() (TCPLossRecovery, error) {
+	return s.Recovery, nil
+}
+
+// SetTCPRecovery implements Stack.SetTCPRecovery.
+func (s *TestStack) SetTCPRecovery(recovery TCPLossRecovery) error {
+	s.Recovery = recovery
+	return nil
+}
+
 // Statistics implements inet.Stack.Statistics.
 func (s *TestStack) Statistics(stat interface{}, arg string) error {
 	return nil
diff --git a/pkg/sentry/socket/hostinet/stack.go b/pkg/sentry/socket/hostinet/stack.go
index a48082631..fda3dcb35 100644
--- a/pkg/sentry/socket/hostinet/stack.go
+++ b/pkg/sentry/socket/hostinet/stack.go
@@ -53,6 +53,7 @@ type Stack struct {
 	interfaceAddrs map[int32][]inet.InterfaceAddr
 	routes         []inet.Route
 	supportsIPv6   bool
+	tcpRecovery    inet.TCPLossRecovery
 	tcpRecvBufSize inet.TCPBufferSize
 	tcpSendBufSize inet.TCPBufferSize
 	tcpSACKEnabled bool
@@ -350,6 +351,16 @@ func (s *Stack) SetTCPSACKEnabled(enabled bool) error {
 	return syserror.EACCES
 }
 
+// TCPRecovery implements inet.Stack.TCPRecovery.
+func (s *Stack) TCPRecovery() (inet.TCPLossRecovery, error) {
+	return s.tcpRecovery, nil
+}
+
+// SetTCPRecovery implements inet.Stack.SetTCPRecovery.
+func (s *Stack) SetTCPRecovery(recovery inet.TCPLossRecovery) error {
+	return syserror.EACCES
+}
+
 // getLine reads one line from proc file, with specified prefix.
 // The last argument, withHeader, specifies if it contains line header.
 func getLine(f *os.File, prefix string, withHeader bool) string {
diff --git a/pkg/sentry/socket/netstack/stack.go b/pkg/sentry/socket/netstack/stack.go
index 67737ae87..f0fe18684 100644
--- a/pkg/sentry/socket/netstack/stack.go
+++ b/pkg/sentry/socket/netstack/stack.go
@@ -207,6 +207,20 @@ func (s *Stack) SetTCPSACKEnabled(enabled bool) error {
 	return syserr.TranslateNetstackError(s.Stack.SetTransportProtocolOption(tcp.ProtocolNumber, tcp.SACKEnabled(enabled))).ToError()
 }
 
+// TCPRecovery implements inet.Stack.TCPRecovery.
+func (s *Stack) TCPRecovery() (inet.TCPLossRecovery, error) {
+	var recovery tcp.Recovery
+	if err := s.Stack.TransportProtocolOption(tcp.ProtocolNumber, &recovery); err != nil {
+		return 0, syserr.TranslateNetstackError(err).ToError()
+	}
+	return inet.TCPLossRecovery(recovery), nil
+}
+
+// SetTCPRecovery implements inet.Stack.SetTCPRecovery.
+func (s *Stack) SetTCPRecovery(recovery inet.TCPLossRecovery) error {
+	return syserr.TranslateNetstackError(s.Stack.SetTransportProtocolOption(tcp.ProtocolNumber, tcp.Recovery(recovery))).ToError()
+}
+
 // Statistics implements inet.Stack.Statistics.
 func (s *Stack) Statistics(stat interface{}, arg string) error {
 	switch stats := stat.(type) {
diff --git a/pkg/tcpip/transport/tcp/protocol.go b/pkg/tcpip/transport/tcp/protocol.go
index b34e47bbd..d9abb8d94 100644
--- a/pkg/tcpip/transport/tcp/protocol.go
+++ b/pkg/tcpip/transport/tcp/protocol.go
@@ -80,6 +80,25 @@ const (
 // enable/disable SACK support in TCP. See: https://tools.ietf.org/html/rfc2018.
 type SACKEnabled bool
 
+// Recovery is used by stack.(*Stack).TransportProtocolOption to
+// set loss detection algorithm in TCP.
+type Recovery int32
+
+const (
+	// RACKLossDetection indicates RACK is used for loss detection and
+	// recovery.
+	RACKLossDetection Recovery = 1 << iota
+
+	// RACKStaticReoWnd indicates the reordering window should not be
+	// adjusted when DSACK is received.
+	RACKStaticReoWnd
+
+	// RACKNoDupTh indicates RACK should not consider the classic three
+	// duplicate acknowledgements rule to mark the segments as lost. This
+	// is used when reordering is not detected.
+	RACKNoDupTh
+)
+
 // DelayEnabled is used by stack.(Stack*).TransportProtocolOption to
 // enable/disable Nagle's algorithm in TCP.
 type DelayEnabled bool
@@ -161,6 +180,7 @@ func (s *synRcvdCounter) Threshold() uint64 {
 type protocol struct {
 	mu                         sync.RWMutex
 	sackEnabled                bool
+	recovery                   Recovery
 	delayEnabled               bool
 	sendBufferSize             SendBufferSizeOption
 	recvBufferSize             ReceiveBufferSizeOption
@@ -280,6 +300,12 @@ func (p *protocol) SetOption(option interface{}) *tcpip.Error {
 		p.mu.Unlock()
 		return nil
 
+	case Recovery:
+		p.mu.Lock()
+		p.recovery = Recovery(v)
+		p.mu.Unlock()
+		return nil
+
 	case DelayEnabled:
 		p.mu.Lock()
 		p.delayEnabled = bool(v)
@@ -394,6 +420,12 @@ func (p *protocol) Option(option interface{}) *tcpip.Error {
 		p.mu.RUnlock()
 		return nil
 
+	case *Recovery:
+		p.mu.RLock()
+		*v = Recovery(p.recovery)
+		p.mu.RUnlock()
+		return nil
+
 	case *DelayEnabled:
 		p.mu.RLock()
 		*v = DelayEnabled(p.delayEnabled)
@@ -535,6 +567,7 @@ func NewProtocol() stack.TransportProtocol {
 		minRTO:                     MinRTO,
 		maxRTO:                     MaxRTO,
 		maxRetries:                 MaxRetries,
+		recovery:                   RACKLossDetection,
 	}
 	p.dispatcher.init(runtime.GOMAXPROCS(0))
 	return &p