[IPV4] ARP: Alloc acceptance of unsolicited ARP via netdevice sysctl.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/inetdevice.h

@@ -25,6 +25,7 @@ struct ipv4_devconf
 	int     arp_filter;
 	int	arp_announce;
 	int	arp_ignore;
+	int	arp_accept;
 	int	medium_id;
 	int	no_xfrm;
 	int	no_policy;

include/linux/sysctl.h

@@ -456,6 +456,7 @@ enum
 	NET_IPV4_CONF_ARP_ANNOUNCE=18,
 	NET_IPV4_CONF_ARP_IGNORE=19,
 	NET_IPV4_CONF_PROMOTE_SECONDARIES=20,
+	NET_IPV4_CONF_ARP_ACCEPT=21,
 	__NET_IPV4_CONF_MAX
 };
 

net/ipv4/arp.c

@@ -879,7 +879,7 @@ static int arp_process(struct sk_buff *skb)
 
 	n = __neigh_lookup(&arp_tbl, &sip, dev, 0);
 
-#ifdef CONFIG_IP_ACCEPT_UNSOLICITED_ARP
+	if (ipv4_devconf.arp_accept) {
 		/* Unsolicited ARP is not accepted by default.
 		   It is possible, that this option should be enabled for some
 		   devices (strip is candidate)
@@ -888,7 +888,7 @@ static int arp_process(struct sk_buff *skb)
 		    arp->ar_op == htons(ARPOP_REPLY) &&
 		    inet_addr_type(sip) == RTN_UNICAST)
 			n = __neigh_lookup(&arp_tbl, &sip, dev, -1);
-#endif
+	}
 
 	if (n) {
 		int state = NUD_REACHABLE;

net/ipv4/devinet.c

@@ -1393,6 +1393,14 @@ static struct devinet_sysctl_table {
 			.mode		= 0644,
 			.proc_handler	= &proc_dointvec,
 		},
+		{
+			.ctl_name	= NET_IPV4_CONF_ARP_ACCEPT,
+			.procname	= "arp_accept",
+			.data		= &ipv4_devconf.arp_accept,
+			.maxlen		= sizeof(int),
+			.mode		= 0644,
+			.proc_handler	= &proc_dointvec,
+		},
 		{
 			.ctl_name	= NET_IPV4_CONF_NOXFRM,
 			.procname	= "disable_xfrm",