diff options
Diffstat (limited to 'pkg/tcpip/transport/tcp/accept.go')
| -rw-r--r-- | pkg/tcpip/transport/tcp/accept.go | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go index f24b51b91..023045ec1 100644 --- a/pkg/tcpip/transport/tcp/accept.go +++ b/pkg/tcpip/transport/tcp/accept.go @@ -419,8 +419,8 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) { // TODO(b/143300739): Use the userMSS of the listening socket // for accepted sockets. - switch s.flags { - case header.TCPFlagSyn: + switch { + case s.flags == header.TCPFlagSyn: opts := parseSynSegmentOptions(s) if incSynRcvdCount() { // Only handle the syn if the following conditions hold @@ -464,7 +464,7 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) { e.stack.Stats().TCP.ListenOverflowSynCookieSent.Increment() } - case header.TCPFlagAck: + case (s.flags & header.TCPFlagAck) != 0: if e.acceptQueueIsFull() { // Silently drop the ack as the application can't accept // the connection at this point. The ack will be @@ -478,6 +478,14 @@ func (e *endpoint) handleListenSegment(ctx *listenContext, s *segment) { } if !synCookiesInUse() { + // When not using SYN cookies, as per RFC 793, section 3.9, page 64: + // Any acknowledgment is bad if it arrives on a connection still in + // the LISTEN state. An acceptable reset segment should be formed + // for any arriving ACK-bearing segment. The RST should be + // formatted as follows: + // + // <SEQ=SEG.ACK><CTL=RST> + // // Send a reset as this is an ACK for which there is no // half open connections and we are not using cookies // yet. |