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Consider the following situation:

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1. A packet comes in that is to be forwarded
2. The destination of the packet is rewritten by some firewall code
3. The next link's MTU is too small
4. The packet has the DF bit set

Then the current code is such that instead of setting the next
link's MTU in the ICMP error, ip_next_mtu() is called and a guess
is sent as to which MTU is supposed to be tried next. This is because
in this case ip_forward() is called with srcrt set to 1. In that
case the ia pointer remains NULL but it is needed to get the MTU
of the interface the packet is to be sent out from.
Thus, we always set ia to the outgoing interface.

MFC after:	2 weeks
This commit is contained in:
Guido van Rooij 2007-12-02 13:00:47 +00:00
parent b21a1da537
commit d23d475fb4
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=174171
1 changed files with 2 additions and 1 deletions
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3
sys/netinet/ip_input.c
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@ -1268,7 +1268,8 @@ ip_forward(struct mbuf *m, int srcrt)
}
#endif
if (!srcrt && (ia = ip_rtaddr(ip->ip_dst)) == NULL) {
ia = ip_rtaddr(ip->ip_dst);
if (!srcrt && ia == NULL) {
icmp_error(m, ICMP_UNREACH, ICMP_UNREACH_HOST, 0, 0);
return;
}