[PATCH net-next] ipv4: correct dropwatch false positive in ip_local_deliver_finish

[PATCH net-next] ipv4: correct dropwatch false positive in ip_local_deliver_finish

[Neil Horman]

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>
---
 net/ipv4/ip_input.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index 87abd3e..2bdf802 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -228,9 +228,11 @@ static int ip_local_deliver_finish(struct sk_buff *skb)
 					icmp_send(skb, ICMP_DEST_UNREACH,
 						  ICMP_PROT_UNREACH, 0);
 				}
-			} else
+				kfree_skb(skb);
+			} else {
 				IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS);
-			kfree_skb(skb);
+				consume_skb(skb);
+			}
 		}
 	}
  out:
-- 
1.7.11.7

Re: [PATCH net-next] ipv4: correct dropwatch false positive in ip_local_deliver_finish

[Eric Dumazet]

On Fri, 2013-03-01 at 11:18 -0500, Neil Horman wrote:
> 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>
> ---
>  net/ipv4/ip_input.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
> index 87abd3e..2bdf802 100644
> --- a/net/ipv4/ip_input.c
> +++ b/net/ipv4/ip_input.c
> @@ -228,9 +228,11 @@ static int ip_local_deliver_finish(struct sk_buff *skb)
>  					icmp_send(skb, ICMP_DEST_UNREACH,
>  						  ICMP_PROT_UNREACH, 0);
>  				}
> -			} else
> +				kfree_skb(skb);
> +			} else {
>  				IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS);
> -			kfree_skb(skb);
> +				consume_skb(skb);
> +			}
>  		}
>  	}
>   out:

Acked-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH net-next] ipv4: correct dropwatch false positive in ip_local_deliver_finish

[Eric Dumazet]

On Fri, 2013-03-01 at 11:18 -0500, Neil Horman wrote:
> 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>
> ---
>  net/ipv4/ip_input.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

Hmm, could you perhaps do the similar fix for IPv6 in the same patch ?

Thanks !

Re: [PATCH net-next] ipv4: correct dropwatch false positive in ip_local_deliver_finish

[Neil Horman]

On Fri, Mar 01, 2013 at 08:38:32AM -0800, Eric Dumazet wrote:
> On Fri, 2013-03-01 at 11:18 -0500, Neil Horman wrote:
> > 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>
> > ---
> >  net/ipv4/ip_input.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> Hmm, could you perhaps do the similar fix for IPv6 in the same patch ?
> 
> Thanks !
> 
Sure, give me a moment, and I'll respin it.
Neil

> 
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