netdev - Re: [net-next PATCH V3] qdisc: validate frames going through the direct

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Date:	Wed, 03 Sep 2014 09:08:27 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Alexander Duyck <alexander.duyck@...il.com>,
	netdev@...r.kernel.org
Subject: Re: [net-next PATCH V3] qdisc: validate frames going through the
 direct_xmit path

On Wed, 2014-09-03 at 17:56 +0200, Jesper Dangaard Brouer wrote:
> In commit 50cbe9ab5f8d ("net: Validate xmit SKBs right when we
> pull them out of the qdisc") the validation code was moved out of
> dev_hard_start_xmit and into dequeue_skb.
> 
> However this overlooked the fact that we do not always enqueue
> the skb onto a qdisc. First situation is if qdisc have flag
> TCQ_F_CAN_BYPASS and qdisc is empty.  Second situation is if
> there is no qdisc on the device, which is a common case for
> software devices.
> 
> Originally spotted and inital patch by Alexander Duyck.
> As a result Alex was seeing issues trying to connect to a
> vhost_net interface after commit 50cbe9ab5f8d was applied.
> 
> Added a call to validate_xmit_skb() in __dev_xmit_skb(), in the
> code path for qdiscs with TCQ_F_CAN_BYPASS flag, and in
> __dev_queue_xmit() when no qdisc.
> 
> Also handle the error situation where dev_hard_start_xmit() could
> return a skb list, and does not return dev_xmit_complete(rc) and
> falls through to the kfree_skb(), in that situation it should
> call kfree_skb_list().

It seems that in this situation, we will return rc = -ENETDOWN,
I do not think this is the right error code. Not sure if that matters...



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