[PATCH net-next] ipv6, token: allow for clearing the current device token

[Daniel Borkmann]

The original tokenized iid support implemented via f53adae4eae5 ("net: ipv6:
add tokenized interface identifier support") didn't allow for clearing a
device token as it was intended that this addressing mode was the only one
active for globally scoped IPv6 addresses. Later we relaxed that restriction
via 617fe29d45bd ("net: ipv6: only invalidate previously tokenized addresses"),
and we should also allow for clearing tokens as there's no good reason why
it shouldn't be allowed.

Fixes: 617fe29d45bd ("net: ipv6: only invalidate previously tokenized 
addresses")
Reported-by: Robin H. Johnson <robb...@gentoo.org>
Signed-off-by: Daniel Borkmann <dan...@iogearbox.net>
Cc: Hannes Frederic Sowa <han...@stressinduktion.org>
---
 Dave, I think net-next is fine, but don't have any objections if you rather
 want to put it into net. Thanks!

 net/ipv6/addrconf.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 27aed1a..a6c9927 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4995,15 +4995,13 @@ static int inet6_set_iftoken(struct inet6_dev *idev, 
struct in6_addr *token)
 {
        struct inet6_ifaddr *ifp;
        struct net_device *dev = idev->dev;
-       bool update_rs = false;
+       bool clear_token, update_rs = false;
        struct in6_addr ll_addr;
 
        ASSERT_RTNL();
 
        if (!token)
                return -EINVAL;
-       if (ipv6_addr_any(token))
-               return -EINVAL;
        if (dev->flags & (IFF_LOOPBACK | IFF_NOARP))
                return -EINVAL;
        if (!ipv6_accept_ra(idev))
@@ -5018,10 +5016,13 @@ static int inet6_set_iftoken(struct inet6_dev *idev, 
struct in6_addr *token)
 
        write_unlock_bh(&idev->lock);
 
+       clear_token = ipv6_addr_any(token);
+       if (clear_token)
+               goto update_lft;
+
        if (!idev->dead && (idev->if_flags & IF_READY) &&
            !ipv6_get_lladdr(dev, &ll_addr, IFA_F_TENTATIVE |
                             IFA_F_OPTIMISTIC)) {
-
                /* If we're not ready, then normal ifup will take care
                 * of this. Otherwise, we need to request our rs here.
                 */
@@ -5029,6 +5030,7 @@ static int inet6_set_iftoken(struct inet6_dev *idev, 
struct in6_addr *token)
                update_rs = true;
        }
 
+update_lft:
        write_lock_bh(&idev->lock);
 
        if (update_rs) {
-- 
1.9.3