net: neigh: use kfree_skb_reason() for __neigh_event_send()

Replace kfree_skb() used in __neigh_event_send() with
kfree_skb_reason(). Following drop reasons are added:

SKB_DROP_REASON_NEIGH_FAILED
SKB_DROP_REASON_NEIGH_QUEUEFULL
SKB_DROP_REASON_NEIGH_DEAD

The first two reasons above should be the hot path that skb drops
in neighbour subsystem.
Reviewed-by: Mengen Sun <mengensun@tencent.com>
Reviewed-by: Hao Peng <flyingpeng@tencent.com>
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -389,6 +389,11 @@ enum skb_drop_reason {
 	SKB_DROP_REASON_NEIGH_CREATEFAIL,	/* failed to create neigh
 						 * entry
 						 */
+	SKB_DROP_REASON_NEIGH_FAILED,	/* neigh entry in failed state */
+	SKB_DROP_REASON_NEIGH_QUEUEFULL,	/* arp_queue for neigh
+						 * entry is full
+						 */
+	SKB_DROP_REASON_NEIGH_DEAD,	/* neigh entry is dead */
 	SKB_DROP_REASON_MAX,
 };
 

include/trace/events/skb.h

@@ -42,6 +42,9 @@
 	   BPF_CGROUP_EGRESS)					\
 	EM(SKB_DROP_REASON_IPV6DISABLED, IPV6DISABLED)		\
 	EM(SKB_DROP_REASON_NEIGH_CREATEFAIL, NEIGH_CREATEFAIL)	\
+	EM(SKB_DROP_REASON_NEIGH_FAILED, NEIGH_FAILED)		\
+	EM(SKB_DROP_REASON_NEIGH_QUEUEFULL, NEIGH_QUEUEFULL)	\
+	EM(SKB_DROP_REASON_NEIGH_DEAD, NEIGH_DEAD)		\
 	EMe(SKB_DROP_REASON_MAX, MAX)
 
 #undef EM

net/core/neighbour.c

@@ -1171,7 +1171,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb,
 			neigh->updated = jiffies;
 			write_unlock_bh(&neigh->lock);
 
-			kfree_skb(skb);
+			kfree_skb_reason(skb, SKB_DROP_REASON_NEIGH_FAILED);
 			return 1;
 		}
 	} else if (neigh->nud_state & NUD_STALE) {
@@ -1193,7 +1193,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb,
 				if (!buff)
 					break;
 				neigh->arp_queue_len_bytes -= buff->truesize;
-				kfree_skb(buff);
+				kfree_skb_reason(buff, SKB_DROP_REASON_NEIGH_QUEUEFULL);
 				NEIGH_CACHE_STAT_INC(neigh->tbl, unres_discards);
 			}
 			skb_dst_force(skb);
@@ -1215,7 +1215,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb,
 	if (neigh->nud_state & NUD_STALE)
 		goto out_unlock_bh;
 	write_unlock_bh(&neigh->lock);
-	kfree_skb(skb);
+	kfree_skb_reason(skb, SKB_DROP_REASON_NEIGH_DEAD);
 	trace_neigh_event_send_dead(neigh, 1);
 	return 1;
 }