net: skb_free_datagram_locked() doesnt drop all packets

dropwatch wrongly diagnose all received UDP packets as drops.

This patch removes trace_kfree_skb() done in skb_free_datagram_locked().

Locations calling skb_free_datagram_locked() should do it on their own.

As a result, drops are accounted on the right function.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index db017ef..ee37d47 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -108,6 +108,7 @@
 #include <net/xfrm.h>
 #include <trace/events/udp.h>
 #include <linux/static_key.h>
+#include <trace/events/skb.h>
 #include "udp_impl.h"
 
 struct udp_table udp_table __read_mostly;
@@ -1220,8 +1221,10 @@
 			goto csum_copy_err;
 	}
 
-	if (err)
+	if (unlikely(err)) {
+		trace_kfree_skb(skb, udp_recvmsg);
 		goto out_free;
+	}
 
 	if (!peeked)
 		UDP_INC_STATS_USER(sock_net(sk),