Make stack.Route safe to access concurrently

Multiple goroutines may use the same stack.Route concurrently so
the stack.Route should make sure that any functions called on it
are thread-safe.

Fixes #4073

PiperOrigin-RevId: 344320491

4 files changed, 14 insertions, 10 deletions

diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go
index 6e5adc383..5f2221f1b 100644
--- a/pkg/tcpip/transport/tcp/accept.go
+++ b/pkg/tcpip/transport/tcp/accept.go
@@ -599,7 +599,7 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) *tcpip.Er
 				ack:    s.sequenceNumber + 1,
 				rcvWnd: ctx.rcvWnd,
 			}
-			if err := e.sendSynTCP(&route, fields, synOpts); err != nil {
+			if err := e.sendSynTCP(route, fields, synOpts); err != nil {
 				return err
 			}
 			e.stack.Stats().TCP.ListenOverflowSynCookieSent.Increment()
diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index 88a632019..e38488d4d 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -300,7 +300,7 @@ func (h *handshake) synSentState(s *segment) *tcpip.Error {
 	if ttl == 0 {
 		ttl = h.ep.route.DefaultTTL()
 	}
-	h.ep.sendSynTCP(&h.ep.route, tcpFields{
+	h.ep.sendSynTCP(h.ep.route, tcpFields{
 		id:     h.ep.ID,
 		ttl:    ttl,
 		tos:    h.ep.sendTOS,
@@ -361,7 +361,7 @@ func (h *handshake) synRcvdState(s *segment) *tcpip.Error {
 			SACKPermitted: h.ep.sackPermitted,
 			MSS:           h.ep.amss,
 		}
-		h.ep.sendSynTCP(&h.ep.route, tcpFields{
+		h.ep.sendSynTCP(h.ep.route, tcpFields{
 			id:     h.ep.ID,
 			ttl:    h.ep.ttl,
 			tos:    h.ep.sendTOS,
@@ -547,7 +547,7 @@ func (h *handshake) start() *tcpip.Error {
 	}
 
 	h.sendSYNOpts = synOpts
-	h.ep.sendSynTCP(&h.ep.route, tcpFields{
+	h.ep.sendSynTCP(h.ep.route, tcpFields{
 		id:     h.ep.ID,
 		ttl:    h.ep.ttl,
 		tos:    h.ep.sendTOS,
@@ -596,7 +596,7 @@ func (h *handshake) complete() *tcpip.Error {
 			// the connection with another ACK or data (as ACKs are never
 			// retransmitted on their own).
 			if h.active || !h.acked || h.deferAccept != 0 && time.Since(h.startTime) > h.deferAccept {
-				h.ep.sendSynTCP(&h.ep.route, tcpFields{
+				h.ep.sendSynTCP(h.ep.route, tcpFields{
 					id:     h.ep.ID,
 					ttl:    h.ep.ttl,
 					tos:    h.ep.sendTOS,
@@ -939,7 +939,7 @@ func (e *endpoint) sendRaw(data buffer.VectorisedView, flags byte, seq, ack seqn
 		sackBlocks = e.sack.Blocks[:e.sack.NumBlocks]
 	}
 	options := e.makeOptions(sackBlocks)
-	err := e.sendTCP(&e.route, tcpFields{
+	err := e.sendTCP(e.route, tcpFields{
 		id:     e.ID,
 		ttl:    e.ttl,
 		tos:    e.sendTOS,
diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go
index 64563a8ba..713a70b47 100644
--- a/pkg/tcpip/transport/tcp/endpoint.go
+++ b/pkg/tcpip/transport/tcp/endpoint.go
@@ -440,7 +440,7 @@ type endpoint struct {
 	isPortReserved    bool `state:"manual"`
 	isRegistered      bool `state:"manual"`
 	boundNICID        tcpip.NICID
-	route             stack.Route `state:"manual"`
+	route             *stack.Route `state:"manual"`
 	ttl               uint8
 	v6only            bool
 	isConnectNotified bool
@@ -705,7 +705,7 @@ func (e *endpoint) UniqueID() uint64 {
 //
 // If userMSS is non-zero and is not greater than the maximum possible MSS for
 // r, it will be used; otherwise, the maximum possible MSS will be used.
-func calculateAdvertisedMSS(userMSS uint16, r stack.Route) uint16 {
+func calculateAdvertisedMSS(userMSS uint16, r *stack.Route) uint16 {
 	// The maximum possible MSS is dependent on the route.
 	// TODO(b/143359391): Respect TCP Min and Max size.
 	maxMSS := uint16(r.MTU() - header.TCPMinimumSize)
@@ -1173,7 +1173,11 @@ func (e *endpoint) cleanupLocked() {
 	e.boundPortFlags = ports.Flags{}
 	e.boundDest = tcpip.FullAddress{}
 
-	e.route.Release()
+	if e.route != nil {
+		e.route.Release()
+		e.route = nil
+	}
+
 	e.stack.CompleteTransportEndpointCleanup(e)
 	tcpip.DeleteDanglingEndpoint(e)
 }
diff --git a/pkg/tcpip/transport/tcp/protocol.go b/pkg/tcpip/transport/tcp/protocol.go
index 2329aca4b..672159eed 100644
--- a/pkg/tcpip/transport/tcp/protocol.go
+++ b/pkg/tcpip/transport/tcp/protocol.go
@@ -250,7 +250,7 @@ func replyWithReset(stack *stack.Stack, s *segment, tos, ttl uint8) *tcpip.Error
 		ttl = route.DefaultTTL()
 	}
 
-	return sendTCP(&route, tcpFields{
+	return sendTCP(route, tcpFields{
 		id:     s.id,
 		ttl:    ttl,
 		tos:    tos,