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From: Florian Westphal <fw@strlen.de>
To: David Miller <davem@davemloft.net>
Cc: koct9i@gmail.com, netdev@vger.kernel.org, dev@openvswitch.org,
	cascardo@redhat.com, edumazet@google.com, fw@strlen.de,
	linux-kernel@vger.kernel.org, pshelar@nicira.com,
	xiyou.wangcong@gmail.com
Subject: Re: [PATCH v2] net: preserve IP control block during GSO segmentation
Date: Thu, 14 Jan 2016 00:36:28 +0100	[thread overview]
Message-ID: <20160113233628.GA10507@breakpoint.cc> (raw)
In-Reply-To: <20160113.155112.119405358547782630.davem@davemloft.net>

David Miller <davem@davemloft.net> wrote:
> From: Konstantin Khlebnikov <koct9i@gmail.com>
> Date: Fri, 08 Jan 2016 15:21:46 +0300
> 
> > Skb_gso_segment() uses skb control block during segmentation.
> > This patch adds 32-bytes room for previous control block which
> > will be copied into all resulting segments.
> > 
> > This patch fixes kernel crash during fragmenting forwarded packets.
> > Fragmentation requires valid IP CB in skb for clearing ip options.
> > Also patch removes custom save/restore in ovs code, now it's redundant.
> > 
> > Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
> > Link: http://lkml.kernel.org/r/CALYGNiP-0MZ-FExV2HutTvE9U-QQtkKSoE--KN=JQE5STYsjAA@mail.gmail.com
> 
> If this works I definitely prefer this approach to the other patch
> where the CB is copied back and forth.

I quite frankly don't care and just like you to apply one or the other;
use coin toss if needed :-}

I would prefer to use a on-stack state since there is no need to
use skb->cb (no queueing) but when I gave it a try it got out of hand
rather quick :-/

Anyway Konstantins approach is safe since we only need this in
ovs/ip forward + nfnetlink_queue cases and in all of these there is
enough room at the cb end (for now at least).

WARNING: multiple messages have this Message-ID (diff)
From: Florian Westphal <fw-HFFVJYpyMKqzQB+pC5nmwQ@public.gmane.org>
To: David Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>
Cc: dev-yBygre7rU0TnMu66kgdUjQ@public.gmane.org,
	netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	fw-HFFVJYpyMKqzQB+pC5nmwQ@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	edumazet-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
	xiyou.wangcong-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
	koct9i-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
Subject: Re: [PATCH v2] net: preserve IP control block during GSO segmentation
Date: Thu, 14 Jan 2016 00:36:28 +0100	[thread overview]
Message-ID: <20160113233628.GA10507@breakpoint.cc> (raw)
In-Reply-To: <20160113.155112.119405358547782630.davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>

David Miller <davem@davemloft.net> wrote:
> From: Konstantin Khlebnikov <koct9i@gmail.com>
> Date: Fri, 08 Jan 2016 15:21:46 +0300
> 
> > Skb_gso_segment() uses skb control block during segmentation.
> > This patch adds 32-bytes room for previous control block which
> > will be copied into all resulting segments.
> > 
> > This patch fixes kernel crash during fragmenting forwarded packets.
> > Fragmentation requires valid IP CB in skb for clearing ip options.
> > Also patch removes custom save/restore in ovs code, now it's redundant.
> > 
> > Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
> > Link: http://lkml.kernel.org/r/CALYGNiP-0MZ-FExV2HutTvE9U-QQtkKSoE--KN=JQE5STYsjAA@mail.gmail.com
> 
> If this works I definitely prefer this approach to the other patch
> where the CB is copied back and forth.

I quite frankly don't care and just like you to apply one or the other;
use coin toss if needed :-}

I would prefer to use a on-stack state since there is no need to
use skb->cb (no queueing) but when I gave it a try it got out of hand
rather quick :-/

Anyway Konstantins approach is safe since we only need this in
ovs/ip forward + nfnetlink_queue cases and in all of these there is
enough room at the cb end (for now at least).
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  reply	other threads:[~2016-01-13 23:36 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-08 12:21 [PATCH v2] net: preserve IP control block during GSO segmentation Konstantin Khlebnikov
2016-01-13 20:51 ` David Miller
2016-01-13 20:51   ` David Miller
2016-01-13 23:36   ` Florian Westphal [this message]
2016-01-13 23:36     ` Florian Westphal
2016-01-14 23:22     ` Hannes Frederic Sowa
2016-01-14 23:22       ` Hannes Frederic Sowa
2016-01-15 19:35     ` David Miller

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