netdev - Re: [PATCH net v3] ipv4: allow local fragmentation in ip_finish_output

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Message-ID: <e5565e1e-cf17-4284-09ba-0c066fe5fa45@stressinduktion.org>
Date:   Thu, 3 Nov 2016 10:42:02 +0100
From:   Hannes Frederic Sowa <hannes@...essinduktion.org>
To:     Lance Richardson <lrichard@...hat.com>, netdev@...r.kernel.org,
        fw@...len.de, jtluka@...hat.com
Subject: Re: [PATCH net v3] ipv4: allow local fragmentation in
 ip_finish_output_gso()

On 02.11.2016 21:36, Lance Richardson wrote:
> Some configurations (e.g. geneve interface with default
> MTU of 1500 over an ethernet interface with 1500 MTU) result
> in the transmission of packets that exceed the configured MTU.
> While this should be considered to be a "bad" configuration,
> it is still allowed and should not result in the sending
> of packets that exceed the configured MTU.
> 
> Fix by dropping the assumption in ip_finish_output_gso() that
> locally originated gso packets will never need fragmentation.
> Basic testing using iperf (observing CPU usage and bandwidth)
> have shown no measurable performance impact for traffic not
> requiring fragmentation.
> 
> Fixes: c7ba65d7b649 ("net: ip: push gso skb forwarding handling down the stack")
> Reported-by: Jan Tluka <jtluka@...hat.com>
> Signed-off-by: Lance Richardson <lrichard@...hat.com>

Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>

Thanks Florian for remembering that we can remove IPSKB_FRAG_SEGS now
again. :)