netdev - Re: [PATCH v6 2/2] net: ip, ipv6: handle gso skbs in forwarding path

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Date:	Thu, 13 Feb 2014 17:17:57 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	fw@...len.de
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH v6 2/2] net: ip, ipv6: handle gso skbs in forwarding
 path

From: Florian Westphal <fw@...len.de>
Date: Thu, 13 Feb 2014 23:09:12 +0100

> Marcelo Ricardo Leitner reported problems when the forwarding link path
> has a lower mtu than the incoming one if the inbound interface supports GRO.
 ...
> However it turns out that skb_segment() assumes skb nr_frags is related
> to mss size so we would BUG there.  I don't want to mess with it considering
> Herbert and Eric disagree on what the correct behavior should be.
> 
> Hannes Frederic Sowa notes that when we would shrink gso_size
> skb_segment would then also need to deal with the case where
> SKB_MAX_FRAGS would be exceeded.
> 
> This uses sofware segmentation in the forward path when we hit ipv4
> non-DF packets and the outgoing link mtu is too small.  Its not perfect,
> but given the lack of bug reports wrt. GRO fwd being broken this is a
> rare case anyway.  Also its not like this could not be improved later
> once the dust settles.
> 
> Acked-by: Herbert Xu <herbert@...dor.apana.org.au>
> Reported-by: Marcelo Ricardo Leitner <mleitner@...hat.com>
> Signed-off-by: Florian Westphal <fw@...len.de>

Also applied and queued up for -stable, thanks.
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