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Avoid a situation where we do not set persist timer after a zero window

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condition.
If you send a 0-length packet, but there is data is the socket buffer, and
neither the rexmt or persist timer is already set, then activate the persist
timer.

PR:			192599
Differential Revision:	D2946
Submitted by:		jlott at averesystems dot com
Reviewed by:		jhb, jch, gnn, hiren
Tested by:		jlott at averesystems dot com, jch
MFC after:		2 weeks
This commit is contained in:
Hiren Panchasara 2015-06-29 21:23:54 +00:00
parent 8971c13ffa
commit f85680793b
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=284941
1 changed files with 24 additions and 0 deletions
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24
sys/netinet/tcp_output.c
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@ -1394,6 +1394,30 @@ tcp_output(struct tcpcb *tp)
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 {
/*