arp: Convert SIOCDARP and SIOCSARP to per-netns RTNL.

ioctl(SIOCDARP/SIOCSARP) operates on a single netns fetched from
an AF_INET socket in inet_ioctl().

Let's hold rtnl_net_lock() for SIOCDARP and SIOCSARP.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: NipaLocal <nipa@local>

Author: q2ven

net/ipv4/arp.c

@@ -1064,8 +1064,8 @@ static int arp_req_set_proxy(struct net *net, struct net_device *dev, int on)
 		IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
 		return 0;
 	}
-	if (__in_dev_get_rtnl(dev)) {
-		IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, on);
+	if (__in_dev_get_rtnl_net(dev)) {
+		IN_DEV_CONF_SET(__in_dev_get_rtnl_net(dev), PROXY_ARP, on);
 		return 0;
 	}
 	return -ENXIO;
@@ -1295,14 +1295,14 @@ int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
 
 	switch (cmd) {
 	case SIOCDARP:
-		rtnl_lock();
+		rtnl_net_lock(net);
 		err = arp_req_delete(net, &r);
-		rtnl_unlock();
+		rtnl_net_unlock(net);
 		break;
 	case SIOCSARP:
-		rtnl_lock();
+		rtnl_net_lock(net);
 		err = arp_req_set(net, &r);
-		rtnl_unlock();
+		rtnl_net_unlock(net);
 		break;
 	case SIOCGARP:
 		rcu_read_lock();