ipv4: add LINUX_MIB_IPRPFILTER snmp counter

Christoph Lameter mentioned that packets could be dropped in input path
because of rp_filter settings, without any SNMP counter being
incremented. System administrator can have a hard time to track the
problem.

This patch introduces a new counter, LINUX_MIB_IPRPFILTER, incremented
each time we drop a packet because Reverse Path Filter triggers.

(We receive an IPv4 datagram on a given interface, and find the route to
send an answer would use another interface)

netstat -s | grep IPReversePathFilter
    IPReversePathFilter: 21714

Reported-by: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index d930dc5e4d85..d52c9da644cf 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -340,6 +340,9 @@ static int ip_rcv_finish(struct sk_buff *skb)
                         else if (err == -ENETUNREACH)
                                 IP_INC_STATS_BH(dev_net(skb->dev),
                                                 IPSTATS_MIB_INNOROUTES);
+                        else if (err == -EXDEV)
+                                NET_INC_STATS_BH(dev_net(skb->dev),
+                                                 LINUX_MIB_IPRPFILTER);
                         goto drop;
                 }
         }