netfilter: nft_meta: Add cpu attribute support

Add cpu support to meta expresion.

This allows you to match packets with cpu number.
Signed-off-by: Ana Rey <anarey@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/uapi/linux/netfilter/nf_tables.h

@@ -572,6 +572,7 @@ enum nft_exthdr_attributes {
  * @NFT_META_BRI_IIFNAME: packet input bridge interface name
  * @NFT_META_BRI_OIFNAME: packet output bridge interface name
  * @NFT_META_PKTTYPE: packet type (skb->pkt_type), special handling for loopback
+ * @NFT_META_CPU: cpu id through smp_processor_id()
  */
 enum nft_meta_keys {
 	NFT_META_LEN,
@@ -594,6 +595,7 @@ enum nft_meta_keys {
 	NFT_META_BRI_IIFNAME,
 	NFT_META_BRI_OIFNAME,
 	NFT_META_PKTTYPE,
+	NFT_META_CPU,
 };
 
 /**

net/netfilter/nft_meta.c

@@ -17,6 +17,7 @@
 #include <linux/in.h>
 #include <linux/ip.h>
 #include <linux/ipv6.h>
+#include <linux/smp.h>
 #include <net/dst.h>
 #include <net/sock.h>
 #include <net/tcp_states.h> /* for TCP_TIME_WAIT */
@@ -151,6 +152,9 @@ void nft_meta_get_eval(const struct nft_expr *expr,
 			goto err;
 		}
 		break;
+	case NFT_META_CPU:
+		dest->data[0] = smp_processor_id();
+		break;
 	default:
 		WARN_ON(1);
 		goto err;
@@ -223,6 +227,7 @@ int nft_meta_get_init(const struct nft_ctx *ctx,
 	case NFT_META_SECMARK:
 #endif
 	case NFT_META_PKTTYPE:
+	case NFT_META_CPU:
 		break;
 	default:
 		return -EOPNOTSUPP;