netdev - Re: ppp_generic: fix multilink fragment MTU calculation (again)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 20 Sep 2011 15:21:28 -0400 (EDT)
From:	David Miller <davem@...hat.com>
To:	v4l@...ffedcow.net
Cc:	netdev@...r.kernel.org
Subject: Re: ppp_generic: fix multilink fragment MTU calculation (again)

From: Henry Wong <v4l@...ffedcow.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@...ffedcow.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.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html