Re: [PATCH] net: reset skb queue mapping when rx'ing over tunnel

[Eric Dumazet <eric.dumazet@gmail.com>]

Le jeudi 23 septembre 2010 à 14:19 -0700, Tom Herbert a écrit :
> Reset queue mapping when an skb is reentering the stack via a tunnel.
> On second pass, the queue mapping from the original device is no
> longer valid.
> 
> Signed-off-by: Tom Herbert <therbert@google.com>
> ---
> diff --git a/include/net/dst.h b/include/net/dst.h
> index 81d1413..0238650 100644
> --- a/include/net/dst.h
> +++ b/include/net/dst.h
> @@ -242,6 +242,7 @@ static inline void skb_tunnel_rx(struct sk_buff *skb, struct net_device *dev)
>  	dev->stats.rx_packets++;
>  	dev->stats.rx_bytes += skb->len;
>  	skb->rxhash = 0;
> +	skb_set_queue_mapping(skb, 0);
>  	skb_dst_drop(skb);
>  	nf_reset(skb);
>  }
> --

Hmm...

This would need to be reverted later when tunnels are updated to be
multiqueue aware ? I made an attempt with GRE some days ago.

I dont understand why this patch is needed, since get_rps_cpu() has a
check anyway

        if (skb_rx_queue_recorded(skb)) {
                u16 index = skb_get_rx_queue(skb);
                if (unlikely(index >= dev->num_rx_queues)) {
                        WARN_ONCE(dev->num_rx_queues > 1, "%s received packet "
                                "on queue %u, but number of RX queues is %u\n",
                                dev->name, index, dev->num_rx_queues);
                        goto done;
                }
                rxqueue = dev->_rx + index;
        } else
                rxqueue = dev->_rx;