net_sched: cls_flow: add key rxhash

We can use rxhash to classify the traffic into flows. As rxhash maybe
supplied by NIC or RPS, it is cheaper.
Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Acked-by: Jamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/pkt_cls.h

@@ -332,6 +332,7 @@ enum {
 	FLOW_KEY_SKUID,
 	FLOW_KEY_SKGID,
 	FLOW_KEY_VLAN_TAG,
+	FLOW_KEY_RXHASH,
 	__FLOW_KEY_MAX,
 };
 

net/sched/cls_flow.c

@@ -306,6 +306,11 @@ static u32 flow_get_vlan_tag(const struct sk_buff *skb)
 	return tag & VLAN_VID_MASK;
 }
 
+static u32 flow_get_rxhash(struct sk_buff *skb)
+{
+	return skb_get_rxhash(skb);
+}
+
 static u32 flow_key_get(struct sk_buff *skb, int key)
 {
 	switch (key) {
@@ -343,6 +348,8 @@ static u32 flow_key_get(struct sk_buff *skb, int key)
 		return flow_get_skgid(skb);
 	case FLOW_KEY_VLAN_TAG:
 		return flow_get_vlan_tag(skb);
+	case FLOW_KEY_RXHASH:
+		return flow_get_rxhash(skb);
 	default:
 		WARN_ON(1);
 		return 0;