netdev - Re: [PATCH] veth: Fix the byte counters

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Message-Id: <20110321.182503.258117496.davem@davemloft.net>
Date:	Mon, 21 Mar 2011 18:25:03 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	ebiederm@...ssion.com
Cc:	netdev@...r.kernel.org, mirq-linux@...e.qmqm.pl,
	eric.dumazet@...il.com, arnd@...db.de, greearb@...delatech.com,
	kaber@...sh.net, daniel.lezcano@...e.fr, xemul@...nvz.org
Subject: Re: [PATCH] veth: Fix the byte counters

From: ebiederm@...ssion.com (Eric W. Biederman)
Date: Mon, 21 Mar 2011 14:40:29 -0700

> 
> Commit 44540960 "veth: move loopback logic to common location" introduced
> a bug in the packet counters.  I don't understand why that happened as it
> is not explained in the comments and the mut check in dev_forward_skb
> retains the assumption that skb->len is the total length of the packet.
> 
> I just measured this emperically by setting up a veth pair between two
> noop network namespaces setting and attempting a telnet connection between
> the two.  I saw three packets in each direction and the byte counters were
> exactly 14*3 = 42 bytes high in each direction.  I got the actual
> packet lengths with tcpdump.
> 
> So remove the extra ETH_HLEN from the veth byte count totals.
> 
> Signed-off-by: Eric W. Biederman <ebiederm@...stanetworks.com>

Applied, thanks.
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