filter: Add SKF_AD_QUEUE instruction

It can help being able to filter packets on their queue_mapping.

If filter performance is not good, we could add a "numqueue" field
in struct packet_type, so that netif_nit_deliver() and other functions
can directly ignore packets with not expected queue number.

Lets experiment this simple filter extension first.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/filter.h

@@ -124,7 +124,8 @@ struct sock_fprog	/* Required for SO_ATTACH_FILTER. */
 #define SKF_AD_NLATTR	12
 #define SKF_AD_NLATTR_NEST	16
 #define SKF_AD_MARK 	20
-#define SKF_AD_MAX	24
+#define SKF_AD_QUEUE	24
+#define SKF_AD_MAX	28
 #define SKF_NET_OFF   (-0x100000)
 #define SKF_LL_OFF    (-0x200000)
 

net/core/filter.c

@@ -306,6 +306,9 @@ load_b:
 		case SKF_AD_MARK:
 			A = skb->mark;
 			continue;
+		case SKF_AD_QUEUE:
+			A = skb->queue_mapping;
+			continue;
 		case SKF_AD_NLATTR: {
 			struct nlattr *nla;