netfilter: nf_tables: add nfproto support to meta expression

Needed by multi-family tables to distinguish IPv4 and IPv6 packets.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/uapi/linux/netfilter/nf_tables.h

@@ -531,6 +531,7 @@ enum nft_exthdr_attributes {
  * @NFT_META_NFTRACE: packet nftrace bit
  * @NFT_META_RTCLASSID: realm value of packet's route (skb->dst->tclassid)
  * @NFT_META_SECMARK: packet secmark (skb->secmark)
+ * @NFT_META_NFPROTO: netfilter protocol
  */
 enum nft_meta_keys {
 	NFT_META_LEN,
@@ -548,6 +549,7 @@ enum nft_meta_keys {
 	NFT_META_NFTRACE,
 	NFT_META_RTCLASSID,
 	NFT_META_SECMARK,
+	NFT_META_NFPROTO,
 };
 
 /**

net/netfilter/nft_meta.c

@@ -43,6 +43,9 @@ static void nft_meta_get_eval(const struct nft_expr *expr,
 	case NFT_META_PROTOCOL:
 		*(__be16 *)dest->data = skb->protocol;
 		break;
+	case NFT_META_NFPROTO:
+		dest->data[0] = pkt->ops->pf;
+		break;
 	case NFT_META_PRIORITY:
 		dest->data[0] = skb->priority;
 		break;
@@ -181,6 +184,7 @@ static int nft_meta_init_validate_get(uint32_t key)
 	switch (key) {
 	case NFT_META_LEN:
 	case NFT_META_PROTOCOL:
+	case NFT_META_NFPROTO:
 	case NFT_META_PRIORITY:
 	case NFT_META_MARK:
 	case NFT_META_IIF: