netstack: tcp socket connected state S/R support.

PiperOrigin-RevId: 201596247
Change-Id: Id22f47b2cdcbe14aa0d930f7807ba75f91a56724

1 files changed, 8 insertions, 3 deletions

diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go
index 85adeef0e..410dfdad4 100644
--- a/pkg/tcpip/transport/tcp/accept.go
+++ b/pkg/tcpip/transport/tcp/accept.go
@@ -68,7 +68,8 @@ func encodeMSS(mss uint16) uint32 {
 // to go above a threshold.
 var synRcvdCount struct {
 	sync.Mutex
-	value uint64
+	value   uint64
+	pending sync.WaitGroup
 }
 
 // listenContext is used by a listening endpoint to store state used while
@@ -102,6 +103,7 @@ func incSynRcvdCount() bool {
 		return false
 	}
 
+	synRcvdCount.pending.Add(1)
 	synRcvdCount.value++
 
 	return true
@@ -115,6 +117,7 @@ func decSynRcvdCount() {
 	defer synRcvdCount.Unlock()
 
 	synRcvdCount.value--
+	synRcvdCount.pending.Done()
 }
 
 // newListenContext creates a new listen context.
@@ -292,7 +295,7 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) {
 		opts := parseSynSegmentOptions(s)
 		if incSynRcvdCount() {
 			s.incRef()
-			go e.handleSynSegment(ctx, s, &opts) // S/R-FIXME
+			go e.handleSynSegment(ctx, s, &opts) // S/R-SAFE: synRcvdCount is the barrier.
 		} else {
 			cookie := ctx.createCookie(s.id, s.sequenceNumber, encodeMSS(opts.MSS))
 			// Send SYN with window scaling because we currently
@@ -381,10 +384,12 @@ func (e *endpoint) protocolListenLoop(rcvWnd seqnum.Size) *tcpip.Error {
 				return nil
 			}
 			if n&notifyDrain != 0 {
-				for s := e.segmentQueue.dequeue(); s != nil; s = e.segmentQueue.dequeue() {
+				for !e.segmentQueue.empty() {
+					s := e.segmentQueue.dequeue()
 					e.handleListenSegment(ctx, s)
 					s.decRef()
 				}
+				synRcvdCount.pending.Wait()
 				close(e.drainDone)
 				<-e.undrain
 			}