1 files changed, 38 insertions, 11 deletions

diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index ee60ebf58..89154391b 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -117,6 +117,7 @@ const (
 	notifyDrain
 	notifyReset
 	notifyKeepaliveChanged
+	notifyMSSChanged
 )
 
 // SACKInfo holds TCP SACK related information for a given endpoint.
@@ -218,8 +219,6 @@ type endpoint struct {
 	mu sync.RWMutex `state:"nosave"`
 	id stack.TransportEndpointID
 
-	// state             endpointState `state:".(endpointState)"`
-	// pState            ProtocolState
 	state EndpointState `state:".(EndpointState)"`
 
 	isPortReserved    bool `state:"manual"`
@@ -313,6 +312,10 @@ type endpoint struct {
 	// in SYN-RCVD state.
 	synRcvdCount int
 
+	// userMSS if non-zero is the MSS value explicitly set by the user
+	// for this endpoint using the TCP_MAXSEG setsockopt.
+	userMSS int
+
 	// The following fields are used to manage the send buffer. When
 	// segments are ready to be sent, they are added to sndQueue and the
 	// protocol goroutine is signaled via sndWaker.
@@ -917,6 +920,17 @@ func (e *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
 		}
 		return nil
 
+	case tcpip.MaxSegOption:
+		userMSS := v
+		if userMSS < header.TCPMinimumMSS || userMSS > header.TCPMaximumMSS {
+			return tcpip.ErrInvalidOptionValue
+		}
+		e.mu.Lock()
+		e.userMSS = int(userMSS)
+		e.mu.Unlock()
+		e.notifyProtocolGoroutine(notifyMSSChanged)
+		return nil
+
 	case tcpip.ReceiveBufferSizeOption:
 		// Make sure the receive buffer size is within the min and max
 		// allowed.
@@ -1086,6 +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) {
@@ -1096,6 +1119,14 @@ func (e *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
 		e.lastErrorMu.Unlock()
 		return err
 
+	case *tcpip.MaxSegOption:
+		// This is just stubbed out. Linux never returns the user_mss
+		// value as it either returns the defaultMSS or returns the
+		// actual current MSS. Netstack just returns the defaultMSS
+		// always for now.
+		*o = header.TCPDefaultMSS
+		return nil
+
 	case *tcpip.SendBufferSizeOption:
 		e.sndBufMu.Lock()
 		*o = tcpip.SendBufferSizeOption(e.sndBufSize)
@@ -1108,15 +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 {
@@ -1271,6 +1293,11 @@ func (e *endpoint) checkV4Mapped(addr *tcpip.FullAddress) (tcpip.NetworkProtocol
 
 // Connect connects the endpoint to its peer.
 func (e *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
+	if addr.Addr == "" && addr.Port == 0 {
+		// AF_UNSPEC isn't supported.
+		return tcpip.ErrAddressFamilyNotSupported
+	}
+
 	return e.connect(addr, true, true)
 }