diff options
| -rw-r--r-- | pkg/tcpip/transport/tcp/snd.go | 18 |
1 files changed, 15 insertions, 3 deletions
diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go index 37f064aaf..7911e6b85 100644 --- a/pkg/tcpip/transport/tcp/snd.go +++ b/pkg/tcpip/transport/tcp/snd.go @@ -1131,6 +1131,14 @@ func (s *sender) SetPipe() { s.outstanding = pipe } +// shouldEnterRecovery returns true if the sender should enter fast recovery +// based on dupAck count and sack scoreboard. +// See RFC 6675 section 5. +func (s *sender) shouldEnterRecovery() bool { + return s.dupAckCount >= nDupAckThreshold || + (s.ep.sackPermitted && s.ep.tcpRecovery&tcpip.TCPRACKLossDetection == 0 && s.ep.scoreboard.IsLost(s.sndUna)) +} + // detectLoss is called when an ack is received and returns whether a loss is // detected. It manages the state related to duplicate acks and determines if // a retransmit is needed according to the rules in RFC 6582 (NewReno). @@ -1155,7 +1163,7 @@ func (s *sender) detectLoss(seg *segment) (fastRetransmit bool) { // Do not enter fast recovery until we reach nDupAckThreshold or the // first unacknowledged byte is considered lost as per SACK scoreboard. - if s.dupAckCount < nDupAckThreshold || (s.ep.sackPermitted && !s.ep.scoreboard.IsLost(s.sndUna)) { + if !s.shouldEnterRecovery() { // RFC 6675 Step 3. s.fr.highRxt = s.sndUna - 1 // Do run SetPipe() to calculate the outstanding segments. @@ -1169,7 +1177,11 @@ func (s *sender) detectLoss(seg *segment) (fastRetransmit bool) { // We only do the check here, the incrementing of last to the highest // sequence number transmitted till now is done when enterRecovery // is invoked. - if !s.fr.last.LessThan(seg.ackNumber) { + // + // Note that we only enter recovery when at least one more byte of data + // beyond s.fr.last (the highest byte that was outstanding when fast + // retransmit was last entered) is acked. + if !s.fr.last.LessThan(seg.ackNumber - 1) { s.dupAckCount = 0 return false } @@ -1351,7 +1363,7 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) { if s.fr.active { // Leave fast recovery if it acknowledges all the data covered by // this fast recovery session. - if ack.InRange(s.sndUna, s.sndNxt+1) && s.fr.last.LessThan(ack) { + if (ack-1).InRange(s.sndUna, s.sndNxt) && s.fr.last.LessThan(ack) { s.leaveRecovery() } } else { |