gre: add link local route when local addr is any

[ Upstream commit 08b44656c08c8c2f73cdac2a058be2880e3361f2 ]

This bug was reported by Steinar H. Gunderson and was introduced by commit
f7cb8886335d ("sit/gre6: don't try to add the same route two times").

root@morgental:~# ip tunnel add foo mode gre remote 1.2.3.4 ttl 64
root@morgental:~# ip link set foo up mtu 1468
root@morgental:~# ip -6 route show dev foo
fe80::/64  proto kernel  metric 256

but after the above commit, no such route shows up.

There is no link local route because dev->dev_addr is 0 (because local ipv4
address is 0), hence no link local address is configured.

In this scenario, the link local address is added manually: 'ip -6 addr add
fe80::1 dev foo' and because prefix is /128, no link local route is added by the
kernel.

Even if the right things to do is to add the link local address with a /64
prefix, we need to restore the previous behavior to avoid breaking userpace.

Reported-by: Steinar H. Gunderson <sesse@samfundet.no>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 4b6b720971b9294910280c6ebd9d46a34ea07e35..9c05d77a20d4aef8c063b1fdf8fc7d9f34df0cd0 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2726,6 +2726,8 @@ static void addrconf_gre_config(struct net_device *dev)
        ipv6_addr_set(&addr,  htonl(0xFE800000), 0, 0, 0);
        if (!ipv6_generate_eui64(addr.s6_addr + 8, dev))
                addrconf_add_linklocal(idev, &addr);
+       else
+               addrconf_prefix_route(&addr, 64, dev, 0, 0);
 }
 #endif