netdev - Re: [RFC] netem: de-GSO packets before enqueing

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Message-ID: <1326470097.3826.12.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
Date:	Fri, 13 Jan 2012 16:54:57 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	Ben Hutchings <bhutchings@...arflare.com>,
	netdev <netdev@...r.kernel.org>,
	netfilter-devel <netfilter-devel@...r.kernel.org>
Subject: Re: [RFC] netem:  de-GSO packets before enqueing

Le jeudi 12 janvier 2012 à 16:57 -0800, Stephen Hemminger a écrit :
> Probably something like this is needed (untested).
> 
> This issue was discovered when looking at the skb_checksum path for the
> netem corruption operation, but it is a general problem.
> Network emulation operations like corruption and drop want to operate
> on a per-packet (not per-segment) basis. This patch does GSO in software
> if necessary to break up packets.  Code is similar to logic in xfrm_output.
> 
> Although it appears that the operation is not work conserving, it is okay
> because the higher level qdisc operations account for packets by incrementing
> by gso_size.

gso_size ok, but what about qlen ?

We end up splitting one GSO skb in multiple segments, but shouldnt we
instruct upper qdisc(s) that qlen was increased, sort of
qdisc_tree_increase_qlen() call ?



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