diff options
| -rw-r--r-- | sys/netinet/tcp_output.c | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c index eb4cb47..111f22e 100644 --- a/sys/netinet/tcp_output.c +++ b/sys/netinet/tcp_output.c @@ -1394,6 +1394,30 @@ timer: tp->t_rxtshift = 0; } tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); + } else if (len == 0 && sbavail(&so->so_snd) && + !tcp_timer_active(tp, TT_REXMT) && + !tcp_timer_active(tp, TT_PERSIST)) { + /* + * 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 { /* |
