ipv4: add option to drop gratuitous ARP packets

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

Enable this by providing an option called "drop_gratuitous_arp".

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/ip.h

@@ -166,6 +166,7 @@ enum
 	IPV4_DEVCONF_IGMPV3_UNSOLICITED_REPORT_INTERVAL,
 	IPV4_DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN,
 	IPV4_DEVCONF_DROP_UNICAST_IN_L2_MULTICAST,
+	IPV4_DEVCONF_DROP_GRATUITOUS_ARP,
 	__IPV4_DEVCONF_MAX
 };