Automated rollback of changelist 634071568

PiperOrigin-RevId: 653421213

pkg/tcpip/transport/tcp/rack.go

@@ -357,13 +357,11 @@ func (rc *rackControl) detectLoss(rcvTime tcpip.MonotonicTime) int {
 	var timeout time.Duration
 	numLost := 0
 	for seg := rc.snd.writeList.Front(); seg != nil && seg.xmitCount != 0; seg = seg.Next() {
-		// xmitCount can be 0 for packets that are broken up for PMTUD.
-		// The initial transmission "doesn't count" WRT loss detection.
-		if rc.snd.ep.scoreboard.IsSACKED(seg.sackBlock()) || seg.xmitCount == 0 {
+		if rc.snd.ep.scoreboard.IsSACKED(seg.sackBlock()) {
 			continue
 		}
 
-		if seg.lost && seg.xmitCount > 1 {
+		if seg.lost && seg.xmitCount == 1 {
 			numLost++
 			continue
 		}

pkg/tcpip/transport/tcp/snd.go

@@ -342,16 +342,10 @@ func (s *sender) updateMaxPayloadSize(mtu, count int) {
 			break
 		}
 
-		if seg.payloadSize() > m {
-			// xmitCount is used for loss detection, but
-			// retransmission doesn't indicate congestion here,
-			// it's just PMTUD.
-			seg.xmitCount = 0
-			if nextSeg == s.writeNext {
-				// We found a segment exceeding the MTU. Rewind
-				// writeNext and try to retransmit it.
-				nextSeg = seg
-			}
+		if nextSeg == s.writeNext && seg.payloadSize() > m {
+			// We found a segment exceeding the MTU. Rewind
+			// writeNext and try to retransmit it.
+			nextSeg = seg
 		}
 
 		if s.ep.SACKPermitted && s.ep.scoreboard.IsSACKED(seg.sackBlock()) {

pkg/tcpip/transport/tcp/test/e2e/tcp_test.go

@@ -5739,7 +5739,6 @@ func TestPathMTUDiscovery(t *testing.T) {
 			}
 			checker.IPv4(t, p,
 				checker.PayloadLen(size+header.TCPMinimumSize),
-				checker.FragmentFlags(header.IPv4FlagDontFragment),
 				checker.TCP(
 					checker.DstPort(context.TestPort),
 					checker.TCPSeqNum(seqNum),