Date: Thu, 12 Sep 2002 20:18:21 +0400 (MSD) From: Maxim Konovalov <maxim@macomnet.ru> To: freebsd-net@freebsd.org Subject: ip reassembling patch Message-ID: <20020912194517.K2218-100000@news1.macomnet.ru>
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Hello -net,
There is a minor bug in reassembling code.
sys/netinet/ip_input.c::ip_input():
730 if (ip->ip_off & IP_MF) {
731 /*
732 * Make sure that fragments have a data length
733 * that's a non-zero multiple of 8 bytes.
734 */
735 if (ip->ip_len == 0 || (ip->ip_len & 0x7) != 0) {
736 ipstat.ips_toosmall++; /* XXX */
737 goto bad;
738 }
739 m->m_flags |= M_FRAG;
740 }
In the code above we go through all mbufs with fragments and set
M_FRAG for all mbufs except the last one.
sys/netinet/ip_input.c::ip_reass() checks this flag later:
1013 /* Make sure the last packet didn't have the IP_MF flag */
1014 if (p->m_flags & M_FRAG)
1015 return (0);
It doesn't work for simplex interfaces because ip_output() sets M_FRAG
for *all* mbufs with fragments.
That is why
# ifconfig lo0 mtu 16384 && ping -s 20000 localhost
doesn't work. (It works for mtu ~= MCLBYTES due to looutput()'s
feature/bug).
I have already discussed this problem with bde and jlemon, I made
several patches, the less intrusive one is below:
Index: sys/netinet/ip_input.c
===================================================================
RCS file: /home/ncvs/src/sys/netinet/ip_input.c,v
retrieving revision 1.130.2.38
diff -u -r1.130.2.38 ip_input.c
--- sys/netinet/ip_input.c 9 Aug 2002 14:49:22 -0000 1.130.2.38
+++ sys/netinet/ip_input.c 9 Sep 2002 14:35:39 -0000
@@ -714,7 +714,8 @@
goto bad;
}
m->m_flags |= M_FRAG;
- }
+ } else
+ m->m_flags &= ~M_FRAG;
ip->ip_off <<= 3;
/*
%%%
Any objections?
--
Maxim Konovalov, MAcomnet, Internet Dept., system engineer
phone: +7 (095) 796-9079, mailto:maxim@macomnet.ru
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