net: skb: use kfree_skb_reason() in __udp4_lib_rcv()

Replace kfree_skb() with kfree_skb_reason() in __udp4_lib_rcv.
New drop reason 'SKB_DROP_REASON_UDP_CSUM' is added for udp csum
error.
Signed-off-by: Menglong Dong <imagedong@tencent.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/skbuff.h

@@ -317,6 +317,7 @@ enum skb_drop_reason {
 	SKB_DROP_REASON_PKT_TOO_SMALL,
 	SKB_DROP_REASON_TCP_CSUM,
 	SKB_DROP_REASON_TCP_FILTER,
+	SKB_DROP_REASON_UDP_CSUM,
 	SKB_DROP_REASON_MAX,
 };
 

include/trace/events/skb.h

@@ -15,6 +15,7 @@
 	EM(SKB_DROP_REASON_PKT_TOO_SMALL, PKT_TOO_SMALL)	\
 	EM(SKB_DROP_REASON_TCP_CSUM, TCP_CSUM)			\
 	EM(SKB_DROP_REASON_TCP_FILTER, TCP_FILTER)		\
+	EM(SKB_DROP_REASON_UDP_CSUM, UDP_CSUM)			\
 	EMe(SKB_DROP_REASON_MAX, MAX)
 
 #undef EM

net/ipv4/udp.c

@@ -2411,6 +2411,9 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 	__be32 saddr, daddr;
 	struct net *net = dev_net(skb->dev);
 	bool refcounted;
+	int drop_reason;
+
+	drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
 
 	/*
 	 *  Validate the packet.
@@ -2466,6 +2469,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 	if (udp_lib_checksum_complete(skb))
 		goto csum_error;
 
+	drop_reason = SKB_DROP_REASON_NO_SOCKET;
 	__UDP_INC_STATS(net, UDP_MIB_NOPORTS, proto == IPPROTO_UDPLITE);
 	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
 
@@ -2473,10 +2477,11 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 	 * Hmm.  We got an UDP packet to a port to which we
 	 * don't wanna listen.  Ignore it.
 	 */
-	kfree_skb(skb);
+	kfree_skb_reason(skb, drop_reason);
 	return 0;
 
 short_packet:
+	drop_reason = SKB_DROP_REASON_PKT_TOO_SMALL;
 	net_dbg_ratelimited("UDP%s: short packet: From %pI4:%u %d/%d to %pI4:%u\n",
 			    proto == IPPROTO_UDPLITE ? "Lite" : "",
 			    &saddr, ntohs(uh->source),
@@ -2489,6 +2494,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 	 * RFC1122: OK.  Discards the bad packet silently (as far as
 	 * the network is concerned, anyway) as per 4.1.3.4 (MUST).
 	 */
+	drop_reason = SKB_DROP_REASON_UDP_CSUM;
 	net_dbg_ratelimited("UDP%s: bad checksum. From %pI4:%u to %pI4:%u ulen %d\n",
 			    proto == IPPROTO_UDPLITE ? "Lite" : "",
 			    &saddr, ntohs(uh->source), &daddr, ntohs(uh->dest),
@@ -2496,7 +2502,7 @@ int __udp4_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
 	__UDP_INC_STATS(net, UDP_MIB_CSUMERRORS, proto == IPPROTO_UDPLITE);
 drop:
 	__UDP_INC_STATS(net, UDP_MIB_INERRORS, proto == IPPROTO_UDPLITE);
-	kfree_skb(skb);
+	kfree_skb_reason(skb, drop_reason);
 	return 0;
 }