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

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Date:	Tue, 14 Dec 2010 07:58:52 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Jamal Hadi Salim <hadi@...erus.ca>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 5/5] net: add skb.old_queue_mapping

On Tue, Dec 14, 2010 at 12:56 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> Le lundi 13 décembre 2010 à 22:43 +0800, Changli Gao a écrit :
>> 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 skb.
>>
>> dev_pick_tx() use the current queue_mapping for the skbs reinjected
>> by ifb.
>>
>> Signed-off-by: Changli Gao <xiaosuo@...il.com>
>> ---
>>  drivers/net/ifb.c      |    1 +
>>  include/linux/skbuff.h |    3 +++
>>  net/core/dev.c         |    5 +++++
>>  net/sched/act_mirred.c |    1 +
>>  4 files changed, 10 insertions(+)
>> diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
>> index 16c767b..481e4b1 100644
>> --- a/drivers/net/ifb.c
>> +++ b/drivers/net/ifb.c
>> @@ -95,6 +95,7 @@ static void ri_tasklet(unsigned long _dev)
>>               u64_stats_update_end(&qp->syncp);
>>               skb->skb_iif = dev->ifindex;
>>
>> +             skb->queue_mapping = skb->old_queue_mapping;
>>               if (from & AT_EGRESS) {
>>                       dev_queue_xmit(skb);
>>               } else if (from & AT_INGRESS) {
>> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
>> index 19f37a6..2ce2a96 100644
>> --- a/include/linux/skbuff.h
>> +++ b/include/linux/skbuff.h
>> @@ -403,6 +403,9 @@ struct sk_buff {
>>       };
>>
>>       __u16                   vlan_tci;
>> +#ifdef CONFIG_NET_CLS_ACT
>> +     __u16                   old_queue_mapping;
>> +#endif
>>
>
> Are you sure we need this field here ? Why not using cb[] for example ?
>

skb->cb can only be used in the same layer, so we can't use it to save
a value crossing layers. A quick grep finds sch_netem just uses
skb->cb. Maybe we can put all the skb->cb in the qdisc layer and
old_queue_mapping in a structure as a new skb->cb. Is it OK? Thanks.


-- 
Regards,
Changli Gao(xiaosuo@...il.com)
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