Merge release-20210125.0-11-gb85b23e50 (automated)

2 files changed, 19 insertions, 0 deletions

diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go
index 62954d7e4..6df4e6525 100644
--- a/pkg/tcpip/transport/tcp/connect.go
+++ b/pkg/tcpip/transport/tcp/connect.go
@@ -1335,6 +1335,14 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{
 		}
 	}
 
+	// Reaching this point means that we successfully completed the 3-way
+	// handshake with our peer.
+	//
+	// Completing the 3-way handshake is an indication that the route is valid
+	// and the remote is reachable as the only way we can complete a handshake
+	// is if our SYN reached the remote and their ACK reached us.
+	e.route.ConfirmReachable()
+
 	drained := e.drainDone != nil
 	if drained {
 		close(e.drainDone)
diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go
index 28ef9f899..027c2a4a8 100644
--- a/pkg/tcpip/transport/tcp/snd.go
+++ b/pkg/tcpip/transport/tcp/snd.go
@@ -1390,6 +1390,17 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
 		acked := s.sndUna.Size(ack)
 		s.sndUna = ack
 
+		// The remote ACK-ing at least 1 byte is an indication that we have a
+		// full-duplex connection to the remote as the only way we will receive an
+		// ACK is if the remote received data that we previously sent.
+		//
+		// As of writing, linux seems to only confirm a route as reachable when
+		// forward progress is made which is indicated by an ACK that removes data
+		// from the retransmit queue.
+		if acked > 0 {
+			s.ep.route.ConfirmReachable()
+		}
+
 		ackLeft := acked
 		originalOutstanding := s.outstanding
 		for ackLeft > 0 {