ipv[4|6]: correct dropwatch false positive in local_deliver_finish

I had a report recently of a user trying to use dropwatch to localise some frame
loss, and they were getting false positives.  Turned out they were using a user
space SCTP stack that used raw sockets to grab frames.  When we don't have a
registered protocol for a given packet, we record it as a drop, even if a raw
socket receieves the frame.  We should only record the drop in the event a raw
socket doesnt exist to receive the frames

Tested by the reported successfully

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Reported-by: William Reich <reich@ulticom.com>
Tested-by: William Reich <reich@ulticom.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: William Reich <reich@ulticom.com>
CC: eric.dumazet@gmail.com
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 2 deletions

diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index 5b10414e619e..b1876e52091e 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -241,9 +241,11 @@ resubmit:
                                 icmpv6_send(skb, ICMPV6_PARAMPROB,
                                             ICMPV6_UNK_NEXTHDR, nhoff);
                         }
-                } else
+                        kfree_skb(skb);
+                } else {
                         IP6_INC_STATS_BH(net, idev, IPSTATS_MIB_INDELIVERS);
-                kfree_skb(skb);
+                        consume_skb(skb);
+                }
         }
         rcu_read_unlock();
         return 0;