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/include/net/pkt_sched.h b/include/net/pkt_sched.h
index 27a3383..fe6e7aa 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -3,6 +3,7 @@
 
 #include <linux/jiffies.h>
 #include <linux/ktime.h>
+#include <linux/if_vlan.h>
 #include <net/sch_generic.h>
 
 struct qdisc_walker {
@@ -114,6 +115,17 @@
 int tc_classify(struct sk_buff *skb, const struct tcf_proto *tp,
 		struct tcf_result *res);
 
+static inline __be16 tc_skb_protocol(const struct sk_buff *skb)
+{
+	/* We need to take extra care in case the skb came via
+	 * vlan accelerated path. In that case, use skb->vlan_proto
+	 * as the original vlan header was already stripped.
+	 */
+	if (vlan_tx_tag_present(skb))
+		return skb->vlan_proto;
+	return skb->protocol;
+}
+
 /* Calculate maximal size of packet seen by hard_start_xmit
    routine of this device.
  */