[NETNS]: Process ARP in the context of the correct namespace.

Get namespace from a device and pass it to the routing engine. Enable
ARP packet processing and device notifiers after that.
Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/arp.c

@@ -242,7 +242,7 @@ static int arp_constructor(struct neighbour *neigh)
 		return -EINVAL;
 	}
 
-	neigh->type = inet_addr_type(&init_net, addr);
+	neigh->type = inet_addr_type(dev->nd_net, addr);
 
 	parms = in_dev->arp_parms;
 	__neigh_parms_put(neigh->parms);
@@ -341,14 +341,14 @@ static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
 	switch (IN_DEV_ARP_ANNOUNCE(in_dev)) {
 	default:
 	case 0:		/* By default announce any local IP */
-		if (skb && inet_addr_type(&init_net, ip_hdr(skb)->saddr) == RTN_LOCAL)
+		if (skb && inet_addr_type(dev->nd_net, ip_hdr(skb)->saddr) == RTN_LOCAL)
 			saddr = ip_hdr(skb)->saddr;
 		break;
 	case 1:		/* Restrict announcements of saddr in same subnet */
 		if (!skb)
 			break;
 		saddr = ip_hdr(skb)->saddr;
-		if (inet_addr_type(&init_net, saddr) == RTN_LOCAL) {
+		if (inet_addr_type(dev->nd_net, saddr) == RTN_LOCAL) {
 			/* saddr should be known to target */
 			if (inet_addr_onlink(in_dev, target, saddr))
 				break;
@@ -424,7 +424,7 @@ static int arp_filter(__be32 sip, __be32 tip, struct net_device *dev)
 	int flag = 0;
 	/*unsigned long now; */
 
-	if (ip_route_output_key(&init_net, &rt, &fl) < 0)
+	if (ip_route_output_key(dev->nd_net, &rt, &fl) < 0)
 		return 1;
 	if (rt->u.dst.dev != dev) {
 		NET_INC_STATS_BH(LINUX_MIB_ARPFILTER);
@@ -477,7 +477,7 @@ int arp_find(unsigned char *haddr, struct sk_buff *skb)
 
 	paddr = skb->rtable->rt_gateway;
 
-	if (arp_set_predefined(inet_addr_type(&init_net, paddr), haddr, paddr, dev))
+	if (arp_set_predefined(inet_addr_type(dev->nd_net, paddr), haddr, paddr, dev))
 		return 0;
 
 	n = __neigh_lookup(&arp_tbl, &paddr, dev, 1);
@@ -709,6 +709,7 @@ static int arp_process(struct sk_buff *skb)
 	u16 dev_type = dev->type;
 	int addr_type;
 	struct neighbour *n;
+	struct net *net = dev->nd_net;
 
 	/* arp_rcv below verifies the ARP header and verifies the device
 	 * is ARP'able.
@@ -804,7 +805,7 @@ static int arp_process(struct sk_buff *skb)
 	/* Special case: IPv4 duplicate address detection packet (RFC2131) */
 	if (sip == 0) {
 		if (arp->ar_op == htons(ARPOP_REQUEST) &&
-		    inet_addr_type(&init_net, tip) == RTN_LOCAL &&
+		    inet_addr_type(net, tip) == RTN_LOCAL &&
 		    !arp_ignore(in_dev, sip, tip))
 			arp_send(ARPOP_REPLY, ETH_P_ARP, sip, dev, tip, sha,
 				 dev->dev_addr, sha);
@@ -834,7 +835,7 @@ static int arp_process(struct sk_buff *skb)
 			goto out;
 		} else if (IN_DEV_FORWARD(in_dev)) {
 			    if (addr_type == RTN_UNICAST  && rt->u.dst.dev != dev &&
-			     (arp_fwd_proxy(in_dev, rt) || pneigh_lookup(&arp_tbl, &init_net, &tip, dev, 0))) {
+			     (arp_fwd_proxy(in_dev, rt) || pneigh_lookup(&arp_tbl, net, &tip, dev, 0))) {
 				n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
 				if (n)
 					neigh_release(n);
@@ -864,7 +865,7 @@ static int arp_process(struct sk_buff *skb)
 		 */
 		if (n == NULL &&
 		    arp->ar_op == htons(ARPOP_REPLY) &&
-		    inet_addr_type(&init_net, sip) == RTN_UNICAST)
+		    inet_addr_type(net, sip) == RTN_UNICAST)
 			n = __neigh_lookup(&arp_tbl, &sip, dev, 1);
 	}
 
@@ -911,9 +912,6 @@ static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
 {
 	struct arphdr *arp;
 
-	if (dev->nd_net != &init_net)
-		goto freeskb;
-
 	/* ARP header, plus 2 device addresses, plus 2 IP addresses.  */
 	if (!pskb_may_pull(skb, arp_hdr_len(dev)))
 		goto freeskb;
@@ -1198,9 +1196,6 @@ static int arp_netdev_event(struct notifier_block *this, unsigned long event, vo
 {
 	struct net_device *dev = ptr;
 
-	if (dev->nd_net != &init_net)
-		return NOTIFY_DONE;
-
 	switch (event) {
 	case NETDEV_CHANGEADDR:
 		neigh_changeaddr(&arp_tbl, dev);