net: simplify and make pkt_type_ok() available for other users

Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -37,6 +37,7 @@
 #include <net/flow_dissector.h>
 #include <linux/splice.h>
 #include <linux/in6.h>
+#include <linux/if_packet.h>
 #include <net/flow.h>
 
 /* The interface for checksum offload between the stack and networking drivers
@@ -881,6 +882,15 @@ static inline struct rtable *skb_rtable(const struct sk_buff *skb)
 	return (struct rtable *)skb_dst(skb);
 }
 
+/* For mangling skb->pkt_type from user space side from applications
+ * such as nft, tc, etc, we only allow a conservative subset of
+ * possible pkt_types to be set.
+*/
+static inline bool skb_pkt_type_ok(u32 ptype)
+{
+	return ptype <= PACKET_OTHERHOST;
+}
+
 void kfree_skb(struct sk_buff *skb);
 void kfree_skb_list(struct sk_buff *segs);
 void skb_tx_error(struct sk_buff *skb);

net/netfilter/nft_meta.c

@@ -199,13 +199,6 @@ err:
 }
 EXPORT_SYMBOL_GPL(nft_meta_get_eval);
 
-/* don't change or set _LOOPBACK, _USER, etc. */
-static bool pkt_type_ok(u32 p)
-{
-	return p == PACKET_HOST || p == PACKET_BROADCAST ||
-	       p == PACKET_MULTICAST || p == PACKET_OTHERHOST;
-}
-
 void nft_meta_set_eval(const struct nft_expr *expr,
 		       struct nft_regs *regs,
 		       const struct nft_pktinfo *pkt)
@@ -223,7 +216,7 @@ void nft_meta_set_eval(const struct nft_expr *expr,
 		break;
 	case NFT_META_PKTTYPE:
 		if (skb->pkt_type != value &&
-		    pkt_type_ok(value) && pkt_type_ok(skb->pkt_type))
+		    skb_pkt_type_ok(value) && skb_pkt_type_ok(skb->pkt_type))
 			skb->pkt_type = value;
 		break;
 	case NFT_META_NFTRACE: