ipv6: add option to drop unsolicited neighbor advertisements

In certain 802.11 wireless deployments, there will be NA proxies
that use knowledge of the network to correctly answer requests.
To prevent unsolicitd advertisements on the shared medium from
being a problem, on such deployments wireless needs to drop them.

Enable this by providing an option called "drop_unsolicited_na".

Signed-off-by: Johannes Berg <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 4a4c1ae..4b2267e 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -56,6 +56,7 @@
 	__s32           ndisc_notify;
 	__s32		suppress_frag_ndisc;
 	__s32		accept_ra_mtu;
+	__s32		drop_unsolicited_na;
 	struct ipv6_stable_secret {
 		bool initialized;
 		struct in6_addr secret;