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 12:03:57 +0800 [thread overview]
Message-ID: <46638F2D.90608@cn.fujitsu.com> (raw)
In-Reply-To: <20070604025528.GA27750@gondor.apana.org.au>
> On Mon, Jun 04, 2007 at 08:39:21AM +0800, Wei Yongjun wrote:
>
>>> Huh? The test new_mtu >= old_mtu should only hold if the sending router
>>> is buggy which is what the hack is for.
>>>
>> 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.
>>
>
> The size of the packet that caused the ICMP is what we want here. That's
> why the router must be buggy.
>
>
So I want to know how the route announce a MTU larger then 576, such as
1280? RFC says ICMP error message return as much as we can without
exceeding 576 bytes.
And ipv4 router alaways return as a packet size 576 because of this.
If MTU is greater then 576, HOST will used "mtu = guess_mtu(old_mtu)" to
get a MTU. Method of send ICMP Fragmentation Needed message is
difference from receive,
how can this resolve? Change the method of send ICMP Fragmentation
Needed message? I do not think so, the only think we can do is to
change the method of receive ICMP message.
Do you agree this?
--
A new email address of FJWAN is launched from Apr.1 2007.
The updated address is: yjwei@cn.fujitsu.com
--------------------------------------------------
Wei Yongjun
Development Dept.I
Nanjing Fujitsu Nanda Software Tech. Co., Ltd.(FNST)
8/F., Civil Defense Building, No.189 Guangzhou Road,
Nanjing, 210029, China
TEL: +86+25-86630523-858
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MAIL: yjwei@cn.fujitsu.com
--------------------------------------------------
next prev parent reply other threads:[~2007-06-04 4:10 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
2007-06-04 2:55 ` Herbert Xu
2007-06-04 4:03 ` Wei Yongjun [this message]
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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