ipv6: enable IPV6_FLOWLABEL_MGR for getsockopt

It is already possible to set/put/renew a label
with IPV6_FLOWLABEL_MGR and setsockopt. This patch
add the possibility to get information about this
label (current value, time before expiration, etc).

It helps application to take decision for a renew
or a release of the label.

v2:
 * Add spin_lock to prevent race condition
 * return -ENOENT if no result found
 * check if flr_action is GET

v3:
 * move the spin_lock to protect only the
   relevant code

Signed-off-by: Florent Fourcot <florent.fourcot@enst-bretagne.fr>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index dd96638..2a5f668 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -250,6 +250,7 @@
 					 struct ipv6_txoptions *fopt);
 void fl6_free_socklist(struct sock *sk);
 int ipv6_flowlabel_opt(struct sock *sk, char __user *optval, int optlen);
+int ipv6_flowlabel_opt_get(struct sock *sk, struct in6_flowlabel_req *freq);
 int ip6_flowlabel_init(void);
 void ip6_flowlabel_cleanup(void);