netdev - Re: [IPv6] interface-local multicast escapes the local node

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Date:	Wed, 6 Feb 2013 13:12:48 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Erik Hugne <erik.hugne@...csson.com>
Cc:	netdev@...r.kernel.org, yoshfuji@...ux-ipv6.org
Subject: Re: [IPv6] interface-local multicast escapes the local node

On Wed, Feb 06, 2013 at 09:49:49AM +0100, Erik Hugne wrote:
> It seems that packets sent to interface-local scoped multicast
> addresses (ff01::/16) escape out on the network.
> According to RFC4291 (section 2.7):
>     Interface-Local scope spans only a single interface on a node
>     and is useful only for loopback transmission of multicast.
> 
> Example program here:
> https://gist.github.com/Hugne/4721151

Fixing the output path should be relatively straightforward, please test
the following patch.

Looking at the input path, I think there is also no input protection
for ff01::/16 addresses from the wire if you bind such an address.

[PATCH net-next] ipv6: don't let node/interface scoped multicast traffic escape on the wire

Reported-by: Erik Hugne <erik.hugne@...csson.com>
Cc: Erik Hugne <erik.hugne@...csson.com>
Cc: YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
---
 net/ipv6/ip6_output.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 906b7e6..b21ff3d 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -118,6 +118,12 @@ static int ip6_finish_output2(struct sk_buff *skb)
 			}
 		}
 
+		if (IPV6_ADDR_MC_SCOPE(&ipv6_hdr(skb)->daddr) <=
+		    IPV6_ADDR_SCOPE_NODELOCAL) {
+			kfree_skb(skb);
+			return 0;
+		}
+
 		IP6_UPD_PO_STATS(dev_net(dev), idev, IPSTATS_MIB_OUTMCAST,
 				skb->len);
 	}
-- 
1.8.1

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