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Ensure that TCP RST-segments announce consistently a receiver window of

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zero. This was already done when sending them via tcp_respond().

Reviewed by:		rrs@
MFC after:		1 week
Sponsored by:		Netflix, Inc.
Differential Revision:	https://reviews.freebsd.org/D17949
This commit is contained in:
tuexen 2018-11-22 19:49:52 +00:00
parent fbbdea9acc
commit 3ece71ca83
2 changed files with 22 additions and 13 deletions
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16
sys/netinet/tcp_output.c
View File

@ -1172,14 +1172,18 @@ tcp_output(struct tcpcb *tp)
/*
* Calculate receive window. Don't shrink window,
* but avoid silly window syndrome.
* If a RST segment is sent, advertise a window of zero.
*/
if (recwin < (so->so_rcv.sb_hiwat / 4) &&
recwin < tp->t_maxseg)
if (flags & TH_RST) {
recwin = 0;
if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
recwin < (tp->rcv_adv - tp->rcv_nxt))
recwin = (tp->rcv_adv - tp->rcv_nxt);
} else {
if (recwin < (so->so_rcv.sb_hiwat / 4) &&
recwin < tp->t_maxseg)
recwin = 0;
if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
recwin < (tp->rcv_adv - tp->rcv_nxt))
recwin = (tp->rcv_adv - tp->rcv_nxt);
}
/*
* According to RFC1323 the window field in a SYN (i.e., a <SYN>
* or <SYN,ACK>) segment itself is never scaled. The <SYN,ACK>

19
sys/netinet/tcp_stacks/rack.c
View File

@ -8189,15 +8189,20 @@ rack_output(struct tcpcb *tp)
/*
* Calculate receive window. Don't shrink window, but avoid silly
* window syndrome.
* If a RST segment is sent, advertise a window of zero.
*/
if (recwin < (long)(so->so_rcv.sb_hiwat / 4) &&
recwin < (long)tp->t_maxseg)
if (flags & TH_RST) {
recwin = 0;
if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
recwin < (long)(tp->rcv_adv - tp->rcv_nxt))
recwin = (long)(tp->rcv_adv - tp->rcv_nxt);
if (recwin > (long)TCP_MAXWIN << tp->rcv_scale)
recwin = (long)TCP_MAXWIN << tp->rcv_scale;
} else {
if (recwin < (long)(so->so_rcv.sb_hiwat / 4) &&
recwin < (long)tp->t_maxseg)
recwin = 0;
if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt) &&
recwin < (long)(tp->rcv_adv - tp->rcv_nxt))
recwin = (long)(tp->rcv_adv - tp->rcv_nxt);
if (recwin > (long)TCP_MAXWIN << tp->rcv_scale)
recwin = (long)TCP_MAXWIN << tp->rcv_scale;
}
/*
* According to RFC1323 the window field in a SYN (i.e., a <SYN> or