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Commit 912e27e8 authored by Paul Durrant's avatar Paul Durrant Committed by David S. Miller
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xen-netback: make sure that hashes are not send to unaware frontends 



In the case when a frontend only negotiates a single queue with xen-
netback it is possible for a skbuff with a s/w hash to result in a
hash extra_info segment being sent to the frontend even when no hash
algorithm has been configured. (The ndo_select_queue() entry point makes
sure the hash is not set if no algorithm is configured, but this entry
point is not called when there is only a single queue). This can result
in a frontend that is unable to handle extra_info segments being given
such a segment, causing it to crash.

This patch fixes the problem by clearing the hash in ndo_start_xmit()
instead, which is clearly guaranteed to be called irrespective of the
number of queues.

Signed-off-by: default avatarPaul Durrant <paul.durrant@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Acked-by: default avatarWei Liu <wei.liu2@citrix.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 21d9629a

drivers/net/xen-netback/interface.c

+9 −11
Original line number Diff line number Diff line
@@ -149,17 +149,8 @@ static u16 xenvif_select_queue(struct net_device *dev, struct sk_buff *skb, 
	struct xenvif *vif = netdev_priv(dev);

	unsigned int size = vif->hash.size;



	if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE) {

		u16 index = fallback(dev, skb) % dev->real_num_tx_queues;



		/* Make sure there is no hash information in the socket

		 * buffer otherwise it would be incorrectly forwarded

		 * to the frontend.

		 */

		skb_clear_hash(skb);



		return index;

	}

	if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE)

		return fallback(dev, skb) % dev->real_num_tx_queues;



	xenvif_set_skb_hash(vif, skb);
@@ -208,6 +199,13 @@ static int xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev) 
	cb = XENVIF_RX_CB(skb);

	cb->expires = jiffies + vif->drain_timeout;



	/* If there is no hash algorithm configured then make sure there

	 * is no hash information in the socket buffer otherwise it

	 * would be incorrectly forwarded to the frontend.

	 */

	if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE)

		skb_clear_hash(skb);



	xenvif_rx_queue_tail(queue, skb);

	xenvif_kick_thread(queue);