[PATCH net-next 6/6] net: udp: use kfree_skb_reason() in __udp_queue_rcv_skb()

[menglong8.dong@gmail.com]

From: Menglong Dong <imagedong@tencent.com>

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

For example, following log will be printed by ftrace when udp socket
receive buff overflow:

> 3345.537796: kfree_skb: skbaddr=00000000f013dfb6 protocol=2048 location=00000000c74d2ddd reason: SOCKET_RCVBUFF
> 3345.638805: kfree_skb: skbaddr=00000000cbc73bc7 protocol=2048 location=00000000c74d2ddd reason: SOCKET_RCVBUFF
> 3345.739975: kfree_skb: skbaddr=00000000717f24bb protocol=2048 location=00000000c74d2ddd reason: SOCKET_RCVBUFF
> 3345.841172: kfree_skb: skbaddr=00000000c62d20e9 protocol=2048 location=00000000c74d2ddd reason: SOCKET_RCVBUFF
> 3345.941353: kfree_skb: skbaddr=000000007eea9d4d protocol=2048 location=00000000c74d2ddd reason: SOCKET_RCVBUFF
> 3346.042610: kfree_skb: skbaddr=00000000c62d20e9 protocol=2048 location=00000000c74d2ddd reason: SOCKET_RCVBUFF
> 3346.142723: kfree_skb: skbaddr=00000000717f24bb protocol=2048 location=00000000c74d2ddd reason: SOCKET_RCVBUFF
> 3346.242785: kfree_skb: skbaddr=00000000cbc73bc7 protocol=2048 location=00000000c74d2ddd reason: SOCKET_RCVBUFF

Signed-off-by: Menglong Dong <imagedong@tencent.com>
---
 include/linux/skbuff.h     |  5 +++++
 include/trace/events/skb.h |  2 ++
 net/ipv4/udp.c             | 10 +++++++---
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index dd64a4f2ff1d..723fc1cbbe3c 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -331,6 +331,11 @@ enum skb_drop_reason {
 	SKB_DROP_REASON_XFRM_POLICY,
 	SKB_DROP_REASON_IP_NOPROTO,
 	SKB_DROP_REASON_UDP_FILTER,
+	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,
 };
 
diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 6db61ce4d6f5..0496bbb0fe08 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -28,6 +28,8 @@
 	EM(SKB_DROP_REASON_XFRM_POLICY, XFRM_POLICY)		\
 	EM(SKB_DROP_REASON_IP_NOPROTO, IP_NOPROTO)		\
 	EM(SKB_DROP_REASON_UDP_FILTER, UDP_FILTER)		\
+	EM(SKB_DROP_REASON_SOCKET_RCVBUFF, SOCKET_RCVBUFF)	\
+	EM(SKB_DROP_REASON_PROTO_MEM, PROTO_MEM)		\
 	EMe(SKB_DROP_REASON_MAX, MAX)
 
 #undef EM
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 57681e98e6bf..ca9ed24704ec 100644
--- a/net/ipv4/udp.c
+++ b/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;
 	}
-- 
2.34.1