ip6_tunnel: ensure to always have a link local address

When an Xin6 tunnel is set up, we check other netdevices to inherit the link-
local address. If none is available, the interface will not have any link-local
address. RFC4862 expects that each interface has a link local address.

Now than this kind of tunnels supports x-netns, it's easy to fall in this case
(by creating the tunnel in a netns where ethernet interfaces stand and then
moving it to a other netns where no ethernet interface is available).

RFC4291, Appendix A suggests two methods: the first is the one currently
implemented, the second is to generate a unique identifier, so that we can
always generate the link-local address. Let's use eth_random_addr() to generate
this interface indentifier.

I remove completly the previous method, hence for the whole life of the
interface, the link-local address remains the same (previously, it depends on
which ethernet interfaces were up when the tunnel interface was set up).

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index cc3bb20..d6e00a3 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -41,6 +41,7 @@
 #include <linux/netfilter_ipv6.h>
 #include <linux/slab.h>
 #include <linux/hash.h>
+#include <linux/etherdevice.h>
 
 #include <asm/uaccess.h>
 #include <linux/atomic.h>
@@ -1471,6 +1472,9 @@ static void ip6_tnl_dev_setup(struct net_device *dev)
 	dev->flags |= IFF_NOARP;
 	dev->addr_len = sizeof(struct in6_addr);
 	dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
+	/* This perm addr will be used as interface identifier by IPv6 */
+	dev->addr_assign_type = NET_ADDR_RANDOM;
+	eth_random_addr(dev->perm_addr);
 }