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>

net/core/datagram.c

@@ -248,7 +248,6 @@ void skb_free_datagram_locked(struct sock *sk, struct sk_buff *skb)
 	unlock_sock_fast(sk, slow);
 
 	/* skb is now orphaned, can be freed outside of locked section */
-	trace_kfree_skb(skb, skb_free_datagram_locked);
 	__kfree_skb(skb);
 }
 EXPORT_SYMBOL(skb_free_datagram_locked);

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 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 			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),

net/ipv6/udp.c

@@ -48,6 +48,7 @@
 
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
+#include <trace/events/skb.h>
 #include "udp_impl.h"
 
 int ipv6_rcv_saddr_equal(const struct sock *sk, const struct sock *sk2)
@@ -385,15 +386,16 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
 
 	if (skb_csum_unnecessary(skb))
 		err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr),
-					      msg->msg_iov, copied       );
+					      msg->msg_iov, copied);
 	else {
 		err = skb_copy_and_csum_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov);
 		if (err == -EINVAL)
 			goto csum_copy_err;
 	}
-	if (err)
+	if (unlikely(err)) {
+		trace_kfree_skb(skb, udpv6_recvmsg);
 		goto out_free;
-
+	}
 	if (!peeked) {
 		if (is_udp4)
 			UDP_INC_STATS_USER(sock_net(sk),

net/sunrpc/svcsock.c

@@ -43,6 +43,7 @@
 #include <net/tcp_states.h>
 #include <asm/uaccess.h>
 #include <asm/ioctls.h>
+#include <trace/events/skb.h>
 
 #include <linux/sunrpc/types.h>
 #include <linux/sunrpc/clnt.h>
@@ -619,6 +620,8 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 	if (!svc_udp_get_dest_address(rqstp, cmh)) {
 		net_warn_ratelimited("svc: received unknown control message %d/%d; dropping RPC reply datagram\n",
 				     cmh->cmsg_level, cmh->cmsg_type);
+out_free:
+		trace_kfree_skb(skb, svc_udp_recvfrom);
 		skb_free_datagram_locked(svsk->sk_sk, skb);
 		return 0;
 	}
@@ -630,8 +633,7 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 		if (csum_partial_copy_to_xdr(&rqstp->rq_arg, skb)) {
 			local_bh_enable();
 			/* checksum error */
-			skb_free_datagram_locked(svsk->sk_sk, skb);
-			return 0;
+			goto out_free;
 		}
 		local_bh_enable();
 		skb_free_datagram_locked(svsk->sk_sk, skb);
@@ -640,10 +642,8 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp)
 		rqstp->rq_arg.head[0].iov_base = skb->data +
 			sizeof(struct udphdr);
 		rqstp->rq_arg.head[0].iov_len = len;
-		if (skb_checksum_complete(skb)) {
-			skb_free_datagram_locked(svsk->sk_sk, skb);
-			return 0;
-		}
+		if (skb_checksum_complete(skb))
+			goto out_free;
 		rqstp->rq_xprt_ctxt = skb;
 	}