udp: Increment UDP_MIB_IGNOREDMULTI for arriving unmatched multicasts

As NIC multicast filtering isn't perfect, and some platforms are
quite content to spew broadcasts, we should not trigger an event
for skb:kfree_skb when we do not have a match for such an incoming
datagram.  We do though want to avoid sweeping the matter under the
rug entirely, so increment a suitable statistic.

This incorporates feedback from David L. Stevens, Karl Neiss and Eric
Dumazet.

V3 - use bool per David Miller

Signed-off-by: Rick Jones <rick.jones2@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index f0d4eb8b99b9..6513ade8d6dc 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -181,6 +181,7 @@ static const struct snmp_mib snmp4_udp_list[] = {
         SNMP_MIB_ITEM("RcvbufErrors", UDP_MIB_RCVBUFERRORS),
         SNMP_MIB_ITEM("SndbufErrors", UDP_MIB_SNDBUFERRORS),
         SNMP_MIB_ITEM("InCsumErrors", UDP_MIB_CSUMERRORS),
+        SNMP_MIB_ITEM("IgnoredMulti", UDP_MIB_IGNOREDMULTI),
         SNMP_MIB_SENTINEL
 };