From: Wei Yongjun <yjwei@cn.fujitsu.com>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: netdev@vger.kernel.org
Subject: Re: [PATCH] Fix bug of update IPv4 PMTU when received ICMP Fragmentation Needed message
Date: Mon, 04 Jun 2007 08:39:21 +0800 [thread overview]
Message-ID: <46635F39.2090009@cn.fujitsu.com> (raw)
In-Reply-To: <E1HuRAd-0002Wl-00@gondolin.me.apana.org.au>
>> 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 <yjwei@cn.fujitsu.com>
--- 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 &&
next prev parent reply other threads:[~2007-06-04 0:45 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-06-01 3:51 [PATCH] Fix bug of update IPv4 PMTU when received ICMP Fragmentation Needed message Wei Yongjun
2007-06-02 10:49 ` Herbert Xu
2007-06-04 0:39 ` Wei Yongjun [this message]
2007-06-04 2:55 ` Herbert Xu
2007-06-04 4:03 ` Wei Yongjun
2007-06-04 4:14 ` Herbert Xu
2007-06-04 4:32 ` Wei Yongjun
2007-06-04 4:55 ` Herbert Xu
2007-06-04 5:38 ` Wei Yongjun
2012-03-21 11:40 ` Ranjeeth
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