diff options
Diffstat (limited to 'sys/netinet/tcp_output.c')
| -rw-r--r-- | sys/netinet/tcp_output.c | 28 |
1 files changed, 27 insertions, 1 deletions
diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c index 734403d0c61..f52ea666340 100644 --- a/sys/netinet/tcp_output.c +++ b/sys/netinet/tcp_output.c @@ -1,4 +1,4 @@ -/* $OpenBSD: tcp_output.c,v 1.112 2015/06/30 15:30:17 mpi Exp $ */ +/* $OpenBSD: tcp_output.c,v 1.113 2015/07/13 23:11:37 bluhm Exp $ */ /* $NetBSD: tcp_output.c,v 1.16 1997/06/03 16:17:09 kml Exp $ */ /* @@ -1008,6 +1008,32 @@ send: tp->t_rxtshift = 0; } } + + if (len == 0 && so->so_snd.sb_cc && + TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 && + TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) { + /* + * Avoid a situation where we do not set persist timer + * after a zero window condition. For example: + * 1) A -> B: packet with enough data to fill the window + * 2) B -> A: ACK for #1 + new data (0 window + * advertisement) + * 3) A -> B: ACK for #2, 0 len packet + * + * In this case, A will not activate the persist timer, + * because it chose to send a packet. Unless tcp_output + * is called for some other reason (delayed ack timer, + * another input packet from B, socket syscall), A will + * not send zero window probes. + * + * So, if you send a 0-length packet, but there is data + * in the socket buffer, and neither the rexmt or + * persist timer is already set, then activate the + * persist timer. + */ + tp->t_rxtshift = 0; + tcp_setpersist(tp); + } } else if (SEQ_GT(tp->snd_nxt + len, tp->snd_max)) tp->snd_max = tp->snd_nxt + len; |