ipv6:introduce function to find route for redirect

RFC 4861 says that the IP source address of the Redirect is the
same as the current first-hop router for the specified ICMP
Destination Address, so the gateway should be taken into
consideration when we find the route for redirect.

There was once a check in commit
a6279458c534d01ccc39498aba61c93083ee0372 ("NDISC: Search over
all possible rules on receipt of redirect.") and the check
went away in commit b94f1c0904da9b8bf031667afc48080ba7c3e8c9
("ipv6: Use icmpv6_notify() to propagate redirect, instead of
rt6_redirect()").

The bug is only "exploitable" on layer-2 because the source
address of the redirect is checked to be a valid link-local
address but it makes spoofing a lot easier in the same L2
domain nonetheless.

Thanks very much for Hannes's help.

Signed-off-by: Duan Jiong <duanj.fnst@cn.fujitsu.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 7cfc8d284870..73681c227453 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -92,7 +92,7 @@ static void icmpv6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
         if (type == ICMPV6_PKT_TOOBIG)
                 ip6_update_pmtu(skb, net, info, 0, 0);
         else if (type == NDISC_REDIRECT)
-                ip6_redirect(skb, net, 0, 0);
+                ip6_redirect(skb, net, skb->dev->ifindex, 0);
 
         if (!(type & ICMPV6_INFOMSG_MASK))
                 if (icmp6->icmp6_type == ICMPV6_ECHO_REQUEST)