net, ip_tunnel: fix interface lookup with no key

when creating a new ipip interface with no local/remote configuration,
the lookup is done with TUNNEL_NO_KEY flag, making it impossible to
match the new interface (only possible match being fallback or metada
case interface); e.g: `ip link add tunl1 type ipip dev eth0`

To fix this case, adding a flag check before the key comparison so we
permit to match an interface with no local/remote config; it also avoids
breaking possible userland tools relying on TUNNEL_NO_KEY flag and
uninitialised key.

context being on my side, I'm creating an extra ipip interface attached
to the physical one, and moving it to a dedicated namespace.

Fixes: c54419321455 ("GRE: Refactor GRE tunneling code.")
Signed-off-by: William Dauchy <w.dauchy@criteo.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 74e1d96..cd4b843 100644 (file)
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -142,11 +142,8 @@ struct ip_tunnel *ip_tunnel_lookup(struct ip_tunnel_net *itn,
                        cand = t;
        }
 
-       if (flags & TUNNEL_NO_KEY)
-               goto skip_key_lookup;
-
        hlist_for_each_entry_rcu(t, head, hash_node) {
-               if (t->parms.i_key != key ||
+               if ((!(flags & TUNNEL_NO_KEY) && t->parms.i_key != key) ||
                    t->parms.iph.saddr != 0 ||
                    t->parms.iph.daddr != 0 ||
                    !(t->dev->flags & IFF_UP))
@@ -158,7 +155,6 @@ struct ip_tunnel *ip_tunnel_lookup(struct ip_tunnel_net *itn,
                        cand = t;
        }
 
-skip_key_lookup:
        if (cand)
                return cand;