netdev - Re: [PATCH 5/5 v4] net: add old_queue

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Date:	Fri, 17 Dec 2010 08:09:23 -0500
From:	jamal <hadi@...erus.ca>
To:	Changli Gao <xiaosuo@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Tom Herbert <therbert@...gle.com>,
	Jiri Pirko <jpirko@...hat.com>, netdev@...r.kernel.org,
	netem@...ts.linux-foundation.org
Subject: Re: [PATCH 5/5 v4] net: add old_queue_mapping into skb->cb

On Thu, 2010-12-16 at 12:56 +0800, Changli Gao wrote:
> For the skbs returned from ifb, we should use the queue_mapping
> saved before ifb.
> 
> We save old queue_mapping in old_queue_mapping just before calling 
> dev_queue_xmit, and restore the old_queue_mapping to queue_mapping
> just before reinjecting the ingress packets.
> 
> A new struct dev_skb_cb is added, and valid in qdisc and gso layer.
> The original qdisc_skb_cb and DEV_GSO_CB use dev_skb_cb as the first
> member.
> 
> netem_skb_cb is changed to contain qdisc_skb_cb.

I am sorry Changli - I think we are talking past each other. I
a conflicted on the whole point of saving and restoring these
devqueue mappings. I understand that for ifb, saving and restoring the
original devs is fundamental for its operation- but i am not sure i see
it for the queues. As an example:

---
# For all packets arriving on ifb0, change mapping to 3 and
# redirect to to ifb1

tc filter add dev ifb0 parent 1:0 protocol ip prio 10 u32 \
match u32 0 0 flowid 1:2 \
action skbedit queue_mapping 4 \
action mirred egress redirect dev ifb1
#
# redirect all packets arriving in eth0 to ifb0
$TC filter add eth0 parent 1:0 protocol ip prio 10 u32 \
match u32 0 0 flowid 1:2 action mirred egress redirect dev ifb0
----

what is the expected behavior?

cheers,
jamal

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