When received ICMP Fragmentation Needed message, PATH MTU is always set
to the 576 even if MTU in ICMP message is lager then 576. This is
because of error condition in function ip_rt_frag_needed(), now if
packet size of that ICMP message is less then new MTU, packet size will
be used ,but RFC says ICMP error message return as much as we can
without exceeding 576 bytes.
This patch has Fixed this BUG.
Huh? The test new_mtu >= old_mtu should only hold if the sending router
is buggy which is what the hack is for.
Cheers,
Note here old_mtu is not the real old mtu, is the received message's size:
unsigned short old_mtu = ntohs(iph->tot_len);
So maybe the patch would like following.
Signed-off-by: Wei Yongjun <[EMAIL PROTECTED]>
--- net/ipv4/route.c.orig 2007-05-25 05:22:47.000000000 +0800
+++ net/ipv4/route.c 2007-06-04 08:31:36.000000000 +0800
@@ -1424,7 +1424,7 @@ unsigned short ip_rt_frag_needed(struct
!(dst_metric_locked(&rth->u.dst, RTAX_MTU))) {
unsigned short mtu = new_mtu;
- if (new_mtu < 68 || new_mtu >= old_mtu) {
+ if (new_mtu < 68 || new_mtu >=
rth->u.dst.metrics[RTAX_MTU-1]) {
/* BSD 4.2 compatibility hack :-( */
if (mtu == 0 &&
-
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