net: udp: use kfree_skb_reason() in __udp_queue_rcv_skb()

Replace kfree_skb() with kfree_skb_reason() in __udp_queue_rcv_skb().
Following new drop reasons are introduced:

SKB_DROP_REASON_SOCKET_RCVBUFF
SKB_DROP_REASON_PROTO_MEM
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

@@ -341,6 +341,11 @@ enum skb_drop_reason {
 						  */
 	SKB_DROP_REASON_XFRM_POLICY,	/* xfrm policy check failed */
 	SKB_DROP_REASON_IP_NOPROTO,	/* no support for IP protocol */
+	SKB_DROP_REASON_SOCKET_RCVBUFF,	/* socket receive buff is full */
+	SKB_DROP_REASON_PROTO_MEM,	/* proto memory limition, such as
+					 * udp packet drop out of
+					 * udp_memory_allocated.
+					 */
 	SKB_DROP_REASON_MAX,
 };
 

include/trace/events/skb.h

@@ -25,6 +25,8 @@
 	   UNICAST_IN_L2_MULTICAST)				\
 	EM(SKB_DROP_REASON_XFRM_POLICY, XFRM_POLICY)		\
 	EM(SKB_DROP_REASON_IP_NOPROTO, IP_NOPROTO)		\
+	EM(SKB_DROP_REASON_SOCKET_RCVBUFF, SOCKET_RCVBUFF)	\
+	EM(SKB_DROP_REASON_PROTO_MEM, PROTO_MEM)		\
 	EMe(SKB_DROP_REASON_MAX, MAX)
 
 #undef EM

net/ipv4/udp.c

@@ -2093,16 +2093,20 @@ static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 	rc = __udp_enqueue_schedule_skb(sk, skb);
 	if (rc < 0) {
 		int is_udplite = IS_UDPLITE(sk);
+		int drop_reason;
 
 		/* Note that an ENOMEM error is charged twice */
-		if (rc == -ENOMEM)
+		if (rc == -ENOMEM) {
 			UDP_INC_STATS(sock_net(sk), UDP_MIB_RCVBUFERRORS,
 					is_udplite);
-		else
+			drop_reason = SKB_DROP_REASON_SOCKET_RCVBUFF;
+		} else {
 			UDP_INC_STATS(sock_net(sk), UDP_MIB_MEMERRORS,
 				      is_udplite);
+			drop_reason = SKB_DROP_REASON_PROTO_MEM;
+		}
 		UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
-		kfree_skb(skb);
+		kfree_skb_reason(skb, drop_reason);
 		trace_udp_fail_queue_rcv_skb(rc, sk);
 		return -1;
 	}