netfilter: nf_tables: Add meta expression key for bridge interface name

NFT_META_BRI_IIFNAME to get packet input bridge interface name
NFT_META_BRI_OIFNAME to get packet output bridge interface name

Such meta key are accessible only through NFPROTO_BRIDGE family, on a
dedicated nft meta module: nft_meta_bridge.

Suggested-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/uapi/linux/netfilter/nf_tables.h

@@ -563,6 +563,8 @@ enum nft_exthdr_attributes {
  * @NFT_META_SECMARK: packet secmark (skb->secmark)
  * @NFT_META_NFPROTO: netfilter protocol
  * @NFT_META_L4PROTO: layer 4 protocol number
+ * @NFT_META_BRI_IIFNAME: packet input bridge interface name
+ * @NFT_META_BRI_OIFNAME: packet output bridge interface name
  */
 enum nft_meta_keys {
 	NFT_META_LEN,
@@ -582,6 +584,8 @@ enum nft_meta_keys {
 	NFT_META_SECMARK,
 	NFT_META_NFPROTO,
 	NFT_META_L4PROTO,
+	NFT_META_BRI_IIFNAME,
+	NFT_META_BRI_OIFNAME,
 };
 
 /**