netdev - Re: problem forwarding IP fragments with DF bit set (caused by ipv4: fix path MTU discovery with connection tracking)

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]

Message-ID: <1398785021.4033.19.camel@sakura.staff.proxad.net>
Date:	Tue, 29 Apr 2014 17:23:41 +0200
From:	Maxime Bizon <mbizon@...ebox.fr>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	Eric Dumazet <edumazet@...gle.com>, davem@...emloft.net,
	netdev <netdev@...r.kernel.org>
Subject: Re: problem forwarding IP fragments with DF bit set (caused by
 ipv4: fix path MTU discovery with connection tracking)


On Tue, 2014-04-29 at 15:45 +0100, Patrick McHardy wrote:

> Right, that is not correct of course. We save the original packet size
> and should either refragment to that size or send an ICMP frag required
> if the original size exceeds the outgoing MTU.

yep indeed, if any fragment is bigger than outgoing MTU

> So your patch does look correct, however we should probably only set
> local_df in conntrack defrag.

I thought of putting it in conntrack code first, but I had some doubts.
There are a lot of possible paths that can be taken after reassembly
(ipsec, tunnel, ...), and I did not audit all of them.

Since the patch that caused this regression modified the generic
fragmentation code, it may have caused other silent breakage.

Eric/David, could I get your feeling about this ?

Thanks,

-- 
Maxime


--
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