udp: add tracepoints for queueing skb to rcvbuf

This patch adds a tracepoint to __udp_queue_rcv_skb to get the
return value of ip_queue_rcv_skb. It indicates why kernel drops
a packet at this point.

ip_queue_rcv_skb returns following values in the packet drop case:

rcvbuf is full                 : -ENOMEM
sk_filter returns error        : -EINVAL, -EACCESS, -ENOMEM, etc.
__sk_mem_schedule returns error: -ENOBUF

Signed-off-by: Satoru Moriya <satoru.moriya@hds.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index abca870d8ff6..37aa9bf8d382 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -105,6 +105,7 @@
 #include <net/route.h>
 #include <net/checksum.h>
 #include <net/xfrm.h>
+#include <trace/events/udp.h>
 #include "udp_impl.h"
 
 struct udp_table udp_table __read_mostly;
@@ -1363,6 +1364,7 @@ static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
                                          is_udplite);
                 UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
                 kfree_skb(skb);
+                trace_udp_fail_queue_rcv_skb(rc, sk);
                 return -1;
         }