net: Add IPv6 flow label to flow_keys

In flow_dissector set the flow label in flow_keys for IPv6. This also
removes the shortcircuiting of flow dissection when a non-zero label
is present, the flow label can be considered to provide additional
entropy for a hash.
Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/flow_dissector.h

@@ -28,7 +28,8 @@ struct flow_dissector_key_basic {
 };
 
 struct flow_dissector_key_tags {
-	u32	vlan_id:12;
+	u32	vlan_id:12,
+		flow_label:20;
 };
 
 /**
@@ -111,6 +112,7 @@ enum flow_dissector_key_id {
 	FLOW_DISSECTOR_KEY_ETH_ADDRS, /* struct flow_dissector_key_eth_addrs */
 	FLOW_DISSECTOR_KEY_TIPC_ADDRS, /* struct flow_dissector_key_tipc_addrs */
 	FLOW_DISSECTOR_KEY_VLANID, /* struct flow_dissector_key_flow_tags */
+	FLOW_DISSECTOR_KEY_FLOW_LABEL, /* struct flow_dissector_key_flow_tags */
 
 	FLOW_DISSECTOR_KEY_MAX,
 };

net/core/flow_dissector.c

@@ -210,30 +210,17 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 
 			memcpy(key_ipv6_addrs, &iph->saddr, sizeof(*key_ipv6_addrs));
 			key_control->addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;
-			goto flow_label;
 		}
-		break;
-flow_label:
+
 		flow_label = ip6_flowlabel(iph);
 		if (flow_label) {
-			/* Awesome, IPv6 packet has a flow label so we can
-			 * use that to represent the ports without any
-			 * further dissection.
-			 */
-
-			key_basic->n_proto = proto;
-			key_basic->ip_proto = ip_proto;
-			key_control->thoff = (u16)nhoff;
-
 			if (skb_flow_dissector_uses_key(flow_dissector,
-							FLOW_DISSECTOR_KEY_PORTS)) {
-				key_ports = skb_flow_dissector_target(flow_dissector,
-								      FLOW_DISSECTOR_KEY_PORTS,
-								      target_container);
-				key_ports->ports = flow_label;
+				FLOW_DISSECTOR_KEY_FLOW_LABEL)) {
+				key_tags = skb_flow_dissector_target(flow_dissector,
+								     FLOW_DISSECTOR_KEY_FLOW_LABEL,
+								     target_container);
+				key_tags->flow_label = ntohl(flow_label);
 			}
-
-			return true;
 		}
 
 		break;
@@ -659,6 +646,10 @@ static const struct flow_dissector_key flow_keys_dissector_keys[] = {
 		.key_id = FLOW_DISSECTOR_KEY_VLANID,
 		.offset = offsetof(struct flow_keys, tags),
 	},
+	{
+		.key_id = FLOW_DISSECTOR_KEY_FLOW_LABEL,
+		.offset = offsetof(struct flow_keys, tags),
+	},
 };
 
 static const struct flow_dissector_key flow_keys_buf_dissector_keys[] = {