From mboxrd@z Thu Jan 1 00:00:00 1970 From: Henry Wong Subject: Re: ppp_generic: fix multilink fragment MTU calculation (again) Date: Tue, 20 Sep 2011 15:54:32 -0400 Message-ID: <4E78EF78.7060106@stuffedcow.net> References: <4E7681BD.2040902@stuffedcow.net> <20110920.152128.1875285861948423018.davem@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: David Miller Return-path: Received: from mail.stuffedcow.net ([206.248.137.124]:40693 "EHLO mail.stuffedcow.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751314Ab1ITTx5 (ORCPT ); Tue, 20 Sep 2011 15:53:57 -0400 In-Reply-To: <20110920.152128.1875285861948423018.davem@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On 9/20/2011 3:21 PM, David Miller wrote: > From: Henry Wong > 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 > 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 :)