netdev - Re: Is skb->queue_mapping valid for received packets?

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Message-ID: <20110614022159.GL21309@gospo.rdu.redhat.com>
Date:	Mon, 13 Jun 2011 22:21:59 -0400
From:	Andy Gospodarek <andy@...yhouse.net>
To:	Ben Greear <greearb@...delatech.com>
Cc:	NetDev <netdev@...r.kernel.org>
Subject: Re: Is skb->queue_mapping valid for received packets?

On Mon, Jun 13, 2011 at 07:06:53PM -0700, Ben Greear wrote:
> On 06/13/2011 06:59 PM, Ben Greear wrote:
>>
>> Anyone know if skb->queue_mapping is set for incoming packets, ie to
>> notify which queue they came in on? I can't find it set anywhere,
>> and it appears it is sometimes set to 1 when it should be 0 in
>> my system.
>>
>> Maybe it's never actually set, and I'm just reading some stale
>> data?
>
> Bleh, found it the second I posted.
>
> Seems it's skb_record_rx_queue(), and funny enough, it seems to add +1,
> so if you are trying to bridge pkts from eth0 to eth1 on the same queues,
> looks like you need to subtract one on xmit before finding the txqueue.
>
> Or something like that.
>

Just saw your response after I replied. :-)

The queue_mapping storage is a bit odd, but it generally works.  The
value stored in queue_mapping should be decremented properly in
dev_pick_tx and it should go out of your card with a tx queue that
matches the rx queue.

There were some issues discovered and fixed with bonding last week
related to queue_mapping and I would not be surprised if another stacked
interface like bridging had an issue.

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