From: Henry Wong <v4l@stuffedcow•net>
To: David Miller <davem@redhat•com>
Cc: netdev@vger•kernel.org
Subject: Re: ppp_generic: fix multilink fragment MTU calculation (again)
Date: Tue, 20 Sep 2011 15:54:32 -0400 [thread overview]
Message-ID: <4E78EF78.7060106@stuffedcow.net> (raw)
In-Reply-To: <20110920.152128.1875285861948423018.davem@redhat.com>
On 9/20/2011 3:21 PM, David Miller wrote:
> From: Henry Wong<v4l@stuffedcow•net>
> Date: Sun, 18 Sep 2011 19:41:49 -0400
>
>> When using MLPPP, the maximum size of a fragment is incorrectly
>> calculated with an offset of -2.
>> This patch reverses the changes in the patch found here:
>> http://marc.info/?l=linux-netdev&m=123541324010539&w=2
>>
>> The value of hdrlen includes the size of both the 2-byte PPP protocol
>> field and the 2- or 4-byte multilink header (2+4=6 for long sequence
>> numbers, 2+2=4 for short sequence numbers). Section 2 of RFC1661 says
>> that the MRU that is negotiated (i.e., the MTU of the sending system)
>> includes only the PPP payload but not the protocol field, thus the
>> correct MTU should be the link's MTU minus the multilink header (mtu -
>> (hdrlen-2)).
>>
>> The incorrect calculation causes Linux to fragment packets to a size
>> two bytes smaller than the allowed MTU. While not technically illegal,
>> this behaviour confounds MRU-tuning to avoid PPP-layer fragmentation.
>>
>> Signed-off-by: Henry Wong<henry@stuffedcow•net>
> Applied, thanks.
>
> There were several cases of trailing whitespace in your patch which I
> needed to fix up. Please don't be so careless in the future.
>
> Thanks.
>
Thanks.
Out of curiosity, were the trailing whitespaces on Lines 10 and 11? Or
was there a problem with file attachments that cause some whitespace I
don't see? I'll be more careful next time :)
next prev parent reply other threads:[~2011-09-20 19:53 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-18 23:41 ppp_generic: fix multilink fragment MTU calculation (again) Henry Wong
2011-09-20 19:21 ` David Miller
2011-09-20 19:54 ` Henry Wong [this message]
2011-09-20 20:01 ` David Miller
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