Merge eefa817c (automated)

12 files changed, 184 insertions, 73 deletions

diff --git a/pkg/sentry/platform/ring0/defs_impl.go b/pkg/sentry/platform/ring0/defs_impl.go
index 8efc3825f..a30a9dd4a 100755
--- a/pkg/sentry/platform/ring0/defs_impl.go
+++ b/pkg/sentry/platform/ring0/defs_impl.go
@@ -1,13 +1,13 @@
 package ring0
 
 import (
-	"fmt"
 	"gvisor.dev/gvisor/pkg/cpuid"
-	"gvisor.dev/gvisor/pkg/sentry/platform/ring0/pagetables"
 	"io"
 	"reflect"
 	"syscall"
 
+	"fmt"
+	"gvisor.dev/gvisor/pkg/sentry/platform/ring0/pagetables"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 )
 
diff --git a/pkg/sentry/socket/control/control.go b/pkg/sentry/socket/control/control.go
index 4f4a20dfe..4e95101b7 100644
--- a/pkg/sentry/socket/control/control.go
+++ b/pkg/sentry/socket/control/control.go
@@ -225,14 +225,14 @@ func putCmsg(buf []byte, flags int, msgType uint32, align uint, data []int32) ([
 	return alignSlice(buf, align), flags
 }
 
-func putCmsgStruct(buf []byte, msgType uint32, align uint, data interface{}) []byte {
+func putCmsgStruct(buf []byte, msgLevel, msgType uint32, align uint, data interface{}) []byte {
 	if cap(buf)-len(buf) < linux.SizeOfControlMessageHeader {
 		return buf
 	}
 	ob := buf
 
 	buf = putUint64(buf, uint64(linux.SizeOfControlMessageHeader))
-	buf = putUint32(buf, linux.SOL_SOCKET)
+	buf = putUint32(buf, msgLevel)
 	buf = putUint32(buf, msgType)
 
 	hdrBuf := buf
@@ -307,12 +307,24 @@ func alignSlice(buf []byte, align uint) []byte {
 func PackTimestamp(t *kernel.Task, timestamp int64, buf []byte) []byte {
 	return putCmsgStruct(
 		buf,
+		linux.SOL_SOCKET,
 		linux.SO_TIMESTAMP,
 		t.Arch().Width(),
 		linux.NsecToTimeval(timestamp),
 	)
 }
 
+// PackInq packs a TCP_INQ socket control message.
+func PackInq(t *kernel.Task, inq int32, buf []byte) []byte {
+	return putCmsgStruct(
+		buf,
+		linux.SOL_TCP,
+		linux.TCP_INQ,
+		4,
+		inq,
+	)
+}
+
 // Parse parses a raw socket control message into portable objects.
 func Parse(t *kernel.Task, socketOrEndpoint interface{}, buf []byte) (transport.ControlMessages, error) {
 	var (
diff --git a/pkg/sentry/socket/epsocket/epsocket.go b/pkg/sentry/socket/epsocket/epsocket.go
index 69eff7373..e57aed927 100644
--- a/pkg/sentry/socket/epsocket/epsocket.go
+++ b/pkg/sentry/socket/epsocket/epsocket.go
@@ -207,6 +207,10 @@ type commonEndpoint interface {
 	// GetSockOpt implements tcpip.Endpoint.GetSockOpt and
 	// transport.Endpoint.GetSockOpt.
 	GetSockOpt(interface{}) *tcpip.Error
+
+	// GetSockOptInt implements tcpip.Endpoint.GetSockOptInt and
+	// transport.Endpoint.GetSockOpt.
+	GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error)
 }
 
 // SocketOperations encapsulates all the state needed to represent a network stack
@@ -249,6 +253,10 @@ type SocketOperations struct {
 	// timestampNS holds the timestamp to use with SIOCTSTAMP. It is only
 	// valid when timestampValid is true. It is protected by readMu.
 	timestampNS int64
+
+	// sockOptInq corresponds to TCP_INQ. It is implemented on the epsocket
+	// level, because it takes into account data from readView.
+	sockOptInq bool
 }
 
 // New creates a new endpoint socket.
@@ -634,6 +642,18 @@ func (s *SocketOperations) GetSockOpt(t *kernel.Task, level, name, outLen int) (
 		}
 		return val, nil
 	}
+	if level == linux.SOL_TCP && name == linux.TCP_INQ {
+		if outLen < sizeOfInt32 {
+			return nil, syserr.ErrInvalidArgument
+		}
+		val := int32(0)
+		s.readMu.Lock()
+		defer s.readMu.Unlock()
+		if s.sockOptInq {
+			val = 1
+		}
+		return val, nil
+	}
 
 	return GetSockOpt(t, s, s.Endpoint, s.family, s.skType, level, name, outLen)
 }
@@ -1048,6 +1068,15 @@ func (s *SocketOperations) SetSockOpt(t *kernel.Task, level int, name int, optVa
 		s.sockOptTimestamp = usermem.ByteOrder.Uint32(optVal) != 0
 		return nil
 	}
+	if level == linux.SOL_TCP && name == linux.TCP_INQ {
+		if len(optVal) < sizeOfInt32 {
+			return syserr.ErrInvalidArgument
+		}
+		s.readMu.Lock()
+		defer s.readMu.Unlock()
+		s.sockOptInq = usermem.ByteOrder.Uint32(optVal) != 0
+		return nil
+	}
 
 	return SetSockOpt(t, s, s.Endpoint, level, name, optVal)
 }
@@ -1267,6 +1296,7 @@ func setSockOptTCP(t *kernel.Task, ep commonEndpoint, name int, optVal []byte) *
 			return syserr.TranslateNetstackError(err)
 		}
 		return nil
+
 	case linux.TCP_REPAIR_OPTIONS:
 		t.Kernel().EmitUnimplementedEvent(t)
 
@@ -1492,7 +1522,6 @@ func emitUnimplementedEventTCP(t *kernel.Task, name int) {
 		linux.TCP_FASTOPEN_CONNECT,
 		linux.TCP_FASTOPEN_KEY,
 		linux.TCP_FASTOPEN_NO_COOKIE,
-		linux.TCP_INQ,
 		linux.TCP_KEEPCNT,
 		linux.TCP_KEEPIDLE,
 		linux.TCP_KEEPINTVL,
@@ -1747,6 +1776,18 @@ func (s *SocketOperations) coalescingRead(ctx context.Context, dst usermem.IOSeq
 	return 0, err
 }
 
+func (s *SocketOperations) fillCmsgInq(cmsg *socket.ControlMessages) {
+	if !s.sockOptInq {
+		return
+	}
+	rcvBufUsed, err := s.Endpoint.GetSockOptInt(tcpip.ReceiveQueueSizeOption)
+	if err != nil {
+		return
+	}
+	cmsg.IP.HasInq = true
+	cmsg.IP.Inq = int32(len(s.readView) + rcvBufUsed)
+}
+
 // nonBlockingRead issues a non-blocking read.
 //
 // TODO(b/78348848): Support timestamps for stream sockets.
@@ -1766,7 +1807,9 @@ func (s *SocketOperations) nonBlockingRead(ctx context.Context, dst usermem.IOSe
 		s.readMu.Lock()
 		n, err := s.coalescingRead(ctx, dst, trunc)
 		s.readMu.Unlock()
-		return n, 0, nil, 0, socket.ControlMessages{}, err
+		cmsg := s.controlMessages()
+		s.fillCmsgInq(&cmsg)
+		return n, 0, nil, 0, cmsg, err
 	}
 
 	s.readMu.Lock()
@@ -1779,8 +1822,8 @@ func (s *SocketOperations) nonBlockingRead(ctx context.Context, dst usermem.IOSe
 	if !isPacket && peek && trunc {
 		// MSG_TRUNC with MSG_PEEK on a TCP socket returns the
 		// amount that could be read.
-		var rql tcpip.ReceiveQueueSizeOption
-		if err := s.Endpoint.GetSockOpt(&rql); err != nil {
+		rql, err := s.Endpoint.GetSockOptInt(tcpip.ReceiveQueueSizeOption)
+		if err != nil {
 			return 0, 0, nil, 0, socket.ControlMessages{}, syserr.TranslateNetstackError(err)
 		}
 		available := len(s.readView) + int(rql)
@@ -1848,7 +1891,9 @@ func (s *SocketOperations) nonBlockingRead(ctx context.Context, dst usermem.IOSe
 		n = msgLen
 	}
 
-	return n, flags, addr, addrLen, s.controlMessages(), syserr.FromError(err)
+	cmsg := s.controlMessages()
+	s.fillCmsgInq(&cmsg)
+	return n, flags, addr, addrLen, cmsg, syserr.FromError(err)
 }
 
 func (s *SocketOperations) controlMessages() socket.ControlMessages {
@@ -2086,9 +2131,9 @@ func Ioctl(ctx context.Context, ep commonEndpoint, io usermem.IO, args arch.Sysc
 		return 0, err
 
 	case linux.TIOCINQ:
-		var v tcpip.ReceiveQueueSizeOption
-		if err := ep.GetSockOpt(&v); err != nil {
-			return 0, syserr.TranslateNetstackError(err).ToError()
+		v, terr := ep.GetSockOptInt(tcpip.ReceiveQueueSizeOption)
+		if terr != nil {
+			return 0, syserr.TranslateNetstackError(terr).ToError()
 		}
 
 		if v > math.MaxInt32 {
diff --git a/pkg/sentry/socket/epsocket/epsocket_state_autogen.go b/pkg/sentry/socket/epsocket/epsocket_state_autogen.go
index 8a743a4ef..c69c145bd 100755
--- a/pkg/sentry/socket/epsocket/epsocket_state_autogen.go
+++ b/pkg/sentry/socket/epsocket/epsocket_state_autogen.go
@@ -21,6 +21,7 @@ func (x *SocketOperations) save(m state.Map) {
 	m.Save("sockOptTimestamp", &x.sockOptTimestamp)
 	m.Save("timestampValid", &x.timestampValid)
 	m.Save("timestampNS", &x.timestampNS)
+	m.Save("sockOptInq", &x.sockOptInq)
 }
 
 func (x *SocketOperations) afterLoad() {}
@@ -37,6 +38,7 @@ func (x *SocketOperations) load(m state.Map) {
 	m.Load("sockOptTimestamp", &x.sockOptTimestamp)
 	m.Load("timestampValid", &x.timestampValid)
 	m.Load("timestampNS", &x.timestampNS)
+	m.Load("sockOptInq", &x.sockOptInq)
 }
 
 func (x *Stack) beforeSave() {}
diff --git a/pkg/sentry/socket/unix/transport/unix.go b/pkg/sentry/socket/unix/transport/unix.go
index b0765ba55..7fb9cb1e0 100644
--- a/pkg/sentry/socket/unix/transport/unix.go
+++ b/pkg/sentry/socket/unix/transport/unix.go
@@ -179,6 +179,10 @@ type Endpoint interface {
 	// tcpip.*Option types.
 	GetSockOpt(opt interface{}) *tcpip.Error
 
+	// GetSockOptInt gets a socket option for simple cases when a return
+	// value has the int type.
+	GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error)
+
 	// State returns the current state of the socket, as represented by Linux in
 	// procfs.
 	State() uint32
@@ -834,33 +838,39 @@ func (e *baseEndpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 	return nil
 }
 
-// GetSockOpt implements tcpip.Endpoint.GetSockOpt.
-func (e *baseEndpoint) GetSockOpt(opt interface{}) *tcpip.Error {
-	switch o := opt.(type) {
-	case tcpip.ErrorOption:
-		return nil
-
-	case *tcpip.SendQueueSizeOption:
+func (e *baseEndpoint) GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error) {
+	switch opt {
+	case tcpip.ReceiveQueueSizeOption:
+		v := 0
 		e.Lock()
 		if !e.Connected() {
 			e.Unlock()
-			return tcpip.ErrNotConnected
+			return -1, tcpip.ErrNotConnected
 		}
-		qs := tcpip.SendQueueSizeOption(e.connected.SendQueuedSize())
+		v = int(e.receiver.RecvQueuedSize())
 		e.Unlock()
-		if qs < 0 {
-			return tcpip.ErrQueueSizeNotSupported
+		if v < 0 {
+			return -1, tcpip.ErrQueueSizeNotSupported
 		}
-		*o = qs
+		return v, nil
+	default:
+		return -1, tcpip.ErrUnknownProtocolOption
+	}
+}
+
+// GetSockOpt implements tcpip.Endpoint.GetSockOpt.
+func (e *baseEndpoint) GetSockOpt(opt interface{}) *tcpip.Error {
+	switch o := opt.(type) {
+	case tcpip.ErrorOption:
 		return nil
 
-	case *tcpip.ReceiveQueueSizeOption:
+	case *tcpip.SendQueueSizeOption:
 		e.Lock()
 		if !e.Connected() {
 			e.Unlock()
 			return tcpip.ErrNotConnected
 		}
-		qs := tcpip.ReceiveQueueSizeOption(e.receiver.RecvQueuedSize())
+		qs := tcpip.SendQueueSizeOption(e.connected.SendQueuedSize())
 		e.Unlock()
 		if qs < 0 {
 			return tcpip.ErrQueueSizeNotSupported
diff --git a/pkg/sentry/syscalls/linux/sys_socket.go b/pkg/sentry/syscalls/linux/sys_socket.go
index 195734257..fa568a660 100644
--- a/pkg/sentry/syscalls/linux/sys_socket.go
+++ b/pkg/sentry/syscalls/linux/sys_socket.go
@@ -802,6 +802,11 @@ func recvSingleMsg(t *kernel.Task, s socket.Socket, msgPtr usermem.Addr, flags i
 		controlData = control.PackTimestamp(t, cms.IP.Timestamp, controlData)
 	}
 
+	if cms.IP.HasInq {
+		// In Linux, TCP_CM_INQ is added after SO_TIMESTAMP.
+		controlData = control.PackInq(t, cms.IP.Inq, controlData)
+	}
+
 	if cms.Unix.Rights != nil {
 		controlData, mflags = control.PackRights(t, cms.Unix.Rights.(control.SCMRights), flags&linux.MSG_CMSG_CLOEXEC != 0, controlData, mflags)
 	}
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index c4076666a..c5d79da5e 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -288,6 +288,12 @@ type ControlMessages struct {
 	// Timestamp is the time (in ns) that the last packed used to create
 	// the read data was received.
 	Timestamp int64
+
+	// HasInq indicates whether Inq is valid/set.
+	HasInq bool
+
+	// Inq is the number of bytes ready to be received.
+	Inq int32
 }
 
 // Endpoint is the interface implemented by transport protocols (e.g., tcp, udp)
@@ -383,6 +389,10 @@ type Endpoint interface {
 	// *Option types.
 	GetSockOpt(opt interface{}) *Error
 
+	// GetSockOptInt gets a socket option for simple cases where a return
+	// value has the int type.
+	GetSockOptInt(SockOpt) (int, *Error)
+
 	// State returns a socket's lifecycle state. The returned value is
 	// protocol-specific and is primarily used for diagnostics.
 	State() uint32
@@ -408,6 +418,18 @@ type WriteOptions struct {
 	EndOfRecord bool
 }
 
+// SockOpt represents socket options which values have the int type.
+type SockOpt int
+
+const (
+	// ReceiveQueueSizeOption is used in GetSockOpt to specify that the number of
+	// unread bytes in the input buffer should be returned.
+	ReceiveQueueSizeOption SockOpt = iota
+
+	// TODO(b/137664753): convert all int socket options to be handled via
+	// GetSockOptInt.
+)
+
 // ErrorOption is used in GetSockOpt to specify that the last error reported by
 // the endpoint should be cleared and returned.
 type ErrorOption struct{}
@@ -424,10 +446,6 @@ type ReceiveBufferSizeOption int
 // unread bytes in the output buffer should be returned.
 type SendQueueSizeOption int
 
-// ReceiveQueueSizeOption is used in GetSockOpt to specify that the number of
-// unread bytes in the input buffer should be returned.
-type ReceiveQueueSizeOption int
-
 // V6OnlyOption is used by SetSockOpt/GetSockOpt to specify whether an IPv6
 // socket is to be restricted to sending and receiving IPv6 packets only.
 type V6OnlyOption int
diff --git a/pkg/tcpip/tcpip_state_autogen.go b/pkg/tcpip/tcpip_state_autogen.go
index 36beffe67..054f95858 100755
--- a/pkg/tcpip/tcpip_state_autogen.go
+++ b/pkg/tcpip/tcpip_state_autogen.go
@@ -26,12 +26,16 @@ func (x *ControlMessages) save(m state.Map) {
 	x.beforeSave()
 	m.Save("HasTimestamp", &x.HasTimestamp)
 	m.Save("Timestamp", &x.Timestamp)
+	m.Save("HasInq", &x.HasInq)
+	m.Save("Inq", &x.Inq)
 }
 
 func (x *ControlMessages) afterLoad() {}
 func (x *ControlMessages) load(m state.Map) {
 	m.Load("HasTimestamp", &x.HasTimestamp)
 	m.Load("Timestamp", &x.Timestamp)
+	m.Load("HasInq", &x.HasInq)
+	m.Load("Inq", &x.Inq)
 }
 
 func init() {
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index a80ceafd0..ba6671c26 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -314,6 +314,22 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 	return nil
 }
 
+// GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
+func (e *endpoint) GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error) {
+	switch opt {
+	case tcpip.ReceiveQueueSizeOption:
+		v := 0
+		e.rcvMu.Lock()
+		if !e.rcvList.Empty() {
+			p := e.rcvList.Front()
+			v = p.data.Size()
+		}
+		e.rcvMu.Unlock()
+		return v, nil
+	}
+	return -1, tcpip.ErrUnknownProtocolOption
+}
+
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
 func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 	switch o := opt.(type) {
@@ -332,17 +348,6 @@ func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 		e.rcvMu.Unlock()
 		return nil
 
-	case *tcpip.ReceiveQueueSizeOption:
-		e.rcvMu.Lock()
-		if e.rcvList.Empty() {
-			*o = 0
-		} else {
-			p := e.rcvList.Front()
-			*o = tcpip.ReceiveQueueSizeOption(p.data.Size())
-		}
-		e.rcvMu.Unlock()
-		return nil
-
 	case *tcpip.KeepaliveEnabledOption:
 		*o = 0
 		return nil
diff --git a/pkg/tcpip/transport/raw/endpoint.go b/pkg/tcpip/transport/raw/endpoint.go
index a29587658..b633cd9d8 100644
--- a/pkg/tcpip/transport/raw/endpoint.go
+++ b/pkg/tcpip/transport/raw/endpoint.go
@@ -487,6 +487,23 @@ func (ep *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 	return nil
 }
 
+// GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
+func (ep *endpoint) GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error) {
+	switch opt {
+	case tcpip.ReceiveQueueSizeOption:
+		v := 0
+		ep.rcvMu.Lock()
+		if !ep.rcvList.Empty() {
+			p := ep.rcvList.Front()
+			v = p.data.Size()
+		}
+		ep.rcvMu.Unlock()
+		return v, nil
+	}
+
+	return -1, tcpip.ErrUnknownProtocolOption
+}
+
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
 func (ep *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 	switch o := opt.(type) {
@@ -505,17 +522,6 @@ func (ep *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 		ep.rcvMu.Unlock()
 		return nil
 
-	case *tcpip.ReceiveQueueSizeOption:
-		ep.rcvMu.Lock()
-		if ep.rcvList.Empty() {
-			*o = 0
-		} else {
-			p := ep.rcvList.Front()
-			*o = tcpip.ReceiveQueueSizeOption(p.data.Size())
-		}
-		ep.rcvMu.Unlock()
-		return nil
-
 	case *tcpip.KeepaliveEnabledOption:
 		*o = 0
 		return nil
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index beb90afb5..89154391b 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -1100,6 +1100,15 @@ func (e *endpoint) readyReceiveSize() (int, *tcpip.Error) {
 	return e.rcvBufUsed, nil
 }
 
+// GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
+func (e *endpoint) GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error) {
+	switch opt {
+	case tcpip.ReceiveQueueSizeOption:
+		return e.readyReceiveSize()
+	}
+	return -1, tcpip.ErrUnknownProtocolOption
+}
+
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
 func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 	switch o := opt.(type) {
@@ -1130,15 +1139,6 @@ func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 		e.rcvListMu.Unlock()
 		return nil
 
-	case *tcpip.ReceiveQueueSizeOption:
-		v, err := e.readyReceiveSize()
-		if err != nil {
-			return err
-		}
-
-		*o = tcpip.ReceiveQueueSizeOption(v)
-		return nil
-
 	case *tcpip.DelayOption:
 		*o = 0
 		if v := atomic.LoadUint32(&e.delay); v != 0 {
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index cb0ea83a6..70f4a2b8c 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -189,7 +189,6 @@ func (e *endpoint) Read(addr *tcpip.FullAddress) (buffer.View, tcpip.ControlMess
 	p := e.rcvList.Front()
 	e.rcvList.Remove(p)
 	e.rcvBufSize -= p.data.Size()
-
 	e.rcvMu.Unlock()
 
 	if addr != nil {
@@ -539,6 +538,22 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 	return nil
 }
 
+// GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
+func (e *endpoint) GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error) {
+	switch opt {
+	case tcpip.ReceiveQueueSizeOption:
+		v := 0
+		e.rcvMu.Lock()
+		if !e.rcvList.Empty() {
+			p := e.rcvList.Front()
+			v = p.data.Size()
+		}
+		e.rcvMu.Unlock()
+		return v, nil
+	}
+	return -1, tcpip.ErrUnknownProtocolOption
+}
+
 // GetSockOpt implements tcpip.Endpoint.GetSockOpt.
 func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 	switch o := opt.(type) {
@@ -573,17 +588,6 @@ func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 		}
 		return nil
 
-	case *tcpip.ReceiveQueueSizeOption:
-		e.rcvMu.Lock()
-		if e.rcvList.Empty() {
-			*o = 0
-		} else {
-			p := e.rcvList.Front()
-			*o = tcpip.ReceiveQueueSizeOption(p.data.Size())
-		}
-		e.rcvMu.Unlock()
-		return nil
-
 	case *tcpip.MulticastTTLOption:
 		e.mu.Lock()
 		*o = tcpip.MulticastTTLOption(e.multicastTTL)