[PATCH 3.16 007/294] net/packet: Fix Tx queue selection for AF_PACKET

[Ben Hutchings]

3.16.50-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: IvÃn Briano <ivan.briano@xxxxxxxxx>

commit ccd4eb49f3392ebf989d58bd013a7bf44cdca4d6 upstream.

When PACKET_QDISC_BYPASS is not used, Tx queue selection will be done
before the packet is enqueued, taking into account any mappings set by
a queuing discipline such as mqprio without hardware offloading. This
selection may be affected by a previously saved queue_mapping, either on
the Rx path, or done before the packet reaches the device, as it's
currently the case for AF_PACKET.

In order for queue selection to work as expected when using traffic
control, there can't be another selection done before that point is
reached, so move the call to packet_pick_tx_queue to
packet_direct_xmit, leaving the default xmit path as it was before
PACKET_QDISC_BYPASS was introduced.

A forward declaration of packet_pick_tx_queue() is introduced to avoid
the need to reorder the functions within the file.

Fixes: d346a3fae3ff ("packet: introduce PACKET_QDISC_BYPASS socket option")
Signed-off-by: IvÃn Briano <ivan.briano@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 net/packet/af_packet.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -214,6 +214,7 @@ static void prb_clear_rxhash(struct tpac
 static void prb_fill_vlan_info(struct tpacket_kbdq_core *,
 		struct tpacket3_hdr *);
 static void packet_flush_mclist(struct sock *sk);
+static void packet_pick_tx_queue(struct net_device *dev, struct sk_buff *skb);
 
 struct packet_skb_cb {
 	unsigned int origlen;
@@ -266,6 +267,7 @@ static int packet_direct_xmit(struct sk_
 			goto drop;
 	}
 
+	packet_pick_tx_queue(dev, skb);
 	queue_map = skb_get_queue_mapping(skb);
 	txq = netdev_get_tx_queue(dev, queue_map);
 
@@ -2343,8 +2345,6 @@ static int tpacket_snd(struct packet_soc
 			}
 		}
 
-		packet_pick_tx_queue(dev, skb);
-
 		skb->destructor = tpacket_destruct_skb;
 		__packet_set_status(po, ph, TP_STATUS_SENDING);
 		packet_inc_pending(&po->tx_ring);
@@ -2551,8 +2551,6 @@ static int packet_snd(struct socket *soc
 	skb->priority = sk->sk_priority;
 	skb->mark = sk->sk_mark;
 
-	packet_pick_tx_queue(dev, skb);
-
 	if (po->has_vnet_hdr) {
 		if (vnet_hdr.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
 			if (!skb_partial_csum_set(skb, vnet_hdr.csum_start,