When processing ICMP need frag message, ignore the suggested MTU unless it
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.
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=288412
@ -1541,11 +1541,6 @@ tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip)
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* in the route to the suggested new
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* value (if given) and then notify.
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*/
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bzero(&inc, sizeof(inc));
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inc.inc_faddr = faddr;
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inc.inc_fibnum =
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inp->inp_inc.inc_fibnum;
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mtu = ntohs(icp->icmp_nextmtu);
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/*
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* If no alternative MTU was
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@ -1560,14 +1555,18 @@ tcp_ctlinput(int cmd, struct sockaddr *sa, void *vip)
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mtu = V_tcp_minmss +
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sizeof(struct tcpiphdr);
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/*
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* Only cache the MTU if it
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* is smaller than the interface
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* or route MTU. tcp_mtudisc()
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* will do right thing by itself.
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* Only process the offered MTU if it
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* is smaller than the current one.
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*/
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if (mtu <= tcp_maxmtu(&inc, NULL))
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if (mtu < tp->t_maxopd +
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sizeof(struct tcpiphdr)) {
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bzero(&inc, sizeof(inc));
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inc.inc_faddr = faddr;
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inc.inc_fibnum =
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inp->inp_inc.inc_fibnum;
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tcp_hc_updatemtu(&inc, mtu);
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tcp_mtudisc(inp, mtu);
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tcp_mtudisc(inp, mtu);
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}
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} else
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inp = (*notify)(inp,
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inetctlerrmap[cmd]);
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