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

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Message-Id: <20161103.161244.1518109748163260273.davem@davemloft.net>
Date:   Thu, 03 Nov 2016 16:12:44 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     lrichard@...hat.com
Cc:     netdev@...r.kernel.org, fw@...len.de, jtluka@...hat.com,
        hannes@...essinduktion.org
Subject: Re: [PATCH net v3] ipv4: allow local fragmentation in
 ip_finish_output_gso()

From: Lance Richardson <lrichard@...hat.com>
Date: Wed,  2 Nov 2016 16:36:17 -0400

> 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>

Applied and queued up for -stable.