Commit cbfd6891 authored by Stefano Brivio's avatar Stefano Brivio Committed by David S. Miller

ipv6: Don't use dst gateway directly in ip6_confirm_neigh()

This is the equivalent of commit 2c6b55f4 ("ipv6: fix neighbour
resolution with raw socket") for ip6_confirm_neigh(): we can send a
packet with MSG_CONFIRM on a raw socket for a connected route, so the
gateway would be :: here, and we should pick the next hop using
rt6_nexthop() instead.

This was found by code review and, to the best of my knowledge, doesn't
actually fix a practical issue: the destination address from the packet
is not considered while confirming a neighbour, as ip6_confirm_neigh()
calls choose_neigh_daddr() without passing the packet, so there are no
similar issues as the one fixed by said commit.

A possible source of issues with the existing implementation might come
from the fact that, if we have a cached dst, we won't consider it,
while rt6_nexthop() takes care of that. I might just not be creative
enough to find a practical problem here: the only way to affect this
with cached routes is to have one coming from an ICMPv6 redirect, but
if the next hop is a directly connected host, there should be no
topology for which a redirect applies here, and tests with redirected
routes show no differences for MSG_CONFIRM (and MSG_PROBE) packets on
raw sockets destined to a directly connected host.

However, directly using the dst gateway here is not consistent anymore
with neighbour resolution, and, in general, as we want the next hop,
using rt6_nexthop() looks like the only sane way to fetch it.
Reported-by: default avatarGuillaume Nault <gnault@redhat.com>
Signed-off-by: default avatarStefano Brivio <sbrivio@redhat.com>
Acked-by: default avatarGuillaume Nault <gnault@redhat.com>
Acked-by: default avatarNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ebecb860
......@@ -227,7 +227,7 @@ static void ip6_confirm_neigh(const struct dst_entry *dst, const void *daddr)
struct net_device *dev = dst->dev;
struct rt6_info *rt = (struct rt6_info *)dst;
daddr = choose_neigh_daddr(&rt->rt6i_gateway, NULL, daddr);
daddr = choose_neigh_daddr(rt6_nexthop(rt, &in6addr_any), NULL, daddr);
if (!daddr)
return;
if (dev->flags & (IFF_NOARP | IFF_LOOPBACK))
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment