net: sched: fix skb->protocol use in case of accelerated vlan path

tc code implicitly considers skb->protocol even in case of accelerated
vlan paths and expects vlan protocol type here. However, on rx path,
if the vlan header was already stripped, skb->protocol contains value
of next header. Similar situation is on tx path.

So for skbs that use skb->vlan_tci for tagging, use skb->vlan_proto instead.

Reported-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
index edbf40d..4cd5cf1 100644
--- a/net/sched/act_csum.c
+++ b/net/sched/act_csum.c
@@ -509,7 +509,7 @@
 	if (unlikely(action == TC_ACT_SHOT))
 		goto drop;
 
-	switch (skb->protocol) {
+	switch (tc_skb_protocol(skb)) {
 	case cpu_to_be16(ETH_P_IP):
 		if (!tcf_csum_ipv4(skb, update_flags))
 			goto drop;