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When processing ICMP need frag message, ignore the suggested MTU unless it

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is smaller than the current one for this connection. This is behavior
specified by RFC 1191, and this is how original BSD stack behaved, but this
was unintentionally regressed in r182851.

Reported & tested by:	Richard Russo <russor whatsapp.com>
Differential Revision:	D3567
Sponsored by:		Nginx, Inc.
This commit is contained in:
Gleb Smirnoff 2015-09-30 03:37:37 +00:00
parent 9e07e493b3
commit 794ac42374
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=288412
1 changed files with 10 additions and 11 deletions
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21
sys/netinet/tcp_subr.c
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@ -1541,11 +1541,6 @@ tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip)
* in the route to the suggested new
* value (if given) and then notify.
*/
bzero(&inc, sizeof(inc));
inc.inc_faddr = faddr;
inc.inc_fibnum =
inp->inp_inc.inc_fibnum;
mtu = ntohs(icp->icmp_nextmtu);
/*
* If no alternative MTU was
@ -1560,14 +1555,18 @@ tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip)
mtu = V_tcp_minmss +
sizeof(struct tcpiphdr);
/*
* Only cache the MTU if it
* is smaller than the interface
* or route MTU. tcp_mtudisc()
* will do right thing by itself.
* Only process the offered MTU if it
* is smaller than the current one.
*/
if (mtu <= tcp_maxmtu(&inc, NULL))
if (mtu < tp->t_maxopd +
sizeof(struct tcpiphdr)) {
bzero(&inc, sizeof(inc));
inc.inc_faddr = faddr;
inc.inc_fibnum =
inp->inp_inc.inc_fibnum;
tcp_hc_updatemtu(&inc, mtu);
tcp_mtudisc(inp, mtu);
tcp_mtudisc(inp, mtu);
}
} else
inp = (*notify)(inp,
inetctlerrmap[cmd]);