Subject: IPv6 and rt6_lookup()

From: Nicolas DICHTEL <[email-masked]>
Date: Thu, 02 Nov 2006 17:25:27 +0100

Hello,

Suppose that a host has autoconfiguration enabled. It will take RA to
autoconfigure an IPv6 address. For example, 
2001:0db8:3008:c1ca:2d0:b7ff:febb:4aee/64.
This host will create a route entry for this onlink prefix (dst: 
2001:0db8:3008:c1ca::/64)
in the MAIN table with the lifetime present in prefix option in RA.
Each time this host will receive a RA, it will update this lifetime. To 
do this,
it will call rt6_lookup() (in addrconf_prefix_rcv()) to find the entry.

Now, suppose that our host joins this anycast group: 
"2001:0db8:3008:c1ca::0". A route
entry will be added in the LOCAL table (see addrconf_join_anycast()).
Problem is that, next time our host will receive a RA and will perform a 
rt6_lookup(),
this function will return the local entry (LOCAL table), and not the 
"dynamic" entry
(MAIN table). Consequence is that the lifetime of the dynamic entry will 
never been updated,
and so will expire, whereas the host will keep the corresponding address.

Maybe, when strict is set to 1 in rt6_lookup(), kernel must not return 
an anycast route.
What about this patch ?

Regards,
Nicolas

[IPv6] Don't return anycast route when strict is enable

Signed-off-by: Nicolas DICHTEL <[email-masked]>

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index c953466..51a8c1d 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -248,6 +248,8 @@ static __inline__ struct rt6_info *rt6_d
 			if (dev->ifindex == oif)
 				return sprt;
 			if (dev->flags & IFF_LOOPBACK) {
+				if (strict && sprt->rt6i_flags & RTF_ANYCAST)
+					continue;
 				if (sprt->rt6i_idev == NULL ||
 				    sprt->rt6i_idev->dev->ifindex != oif) {
 					if (strict && oif)