net: dropreason: add SKB_CONSUMED reason

This will allow to simply use in the future:

	kfree_skb_reason(skb, reason);

Instead of repeating sequences like:

	if (dropped)
	    kfree_skb_reason(skb, reason);
	else
	    consume_skb(skb);

For instance, following patch in the series is adding
@reason to skb_release_data() and skb_release_all(),
so that we can propagate a meaningful @reason whenever
consume_skb()/kfree_skb() have to take care of a potential frag_list.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/dropreason.h

@@ -80,6 +80,8 @@ enum skb_drop_reason {
 	 * @SKB_NOT_DROPPED_YET: skb is not dropped yet (used for no-drop case)
 	 */
 	SKB_NOT_DROPPED_YET = 0,
+	/** @SKB_CONSUMED: packet has been consumed */
+	SKB_CONSUMED,
 	/** @SKB_DROP_REASON_NOT_SPECIFIED: drop reason is not specified */
 	SKB_DROP_REASON_NOT_SPECIFIED,
 	/** @SKB_DROP_REASON_NO_SOCKET: socket not found */

net/core/skbuff.c

@@ -94,6 +94,7 @@ EXPORT_SYMBOL(sysctl_max_skb_frags);
 #undef FN
 #define FN(reason) [SKB_DROP_REASON_##reason] = #reason,
 const char * const drop_reasons[] = {
+	[SKB_CONSUMED] = "CONSUMED",
 	DEFINE_DROP_REASON(FN, FN)
 };
 EXPORT_SYMBOL(drop_reasons);
@@ -894,7 +895,10 @@ kfree_skb_reason(struct sk_buff *skb, enum skb_drop_reason reason)
 
 	DEBUG_NET_WARN_ON_ONCE(reason <= 0 || reason >= SKB_DROP_REASON_MAX);
 
-	trace_kfree_skb(skb, __builtin_return_address(0), reason);
+	if (reason == SKB_CONSUMED)
+		trace_consume_skb(skb);
+	else
+		trace_kfree_skb(skb, __builtin_return_address(0), reason);
 	__kfree_skb(skb);
 }
 EXPORT_SYMBOL(kfree_skb_reason);