ipv6: Add __in6_dev_get_rtnl_net().

We will convert rtnl_lock() with rtnl_net_lock(), and we want to
convert __in6_dev_get() too.

__in6_dev_get() uses rcu_dereference_rtnl(), but as written in its
comment, rtnl_dereference() or rcu_dereference() is preferable.

Let's add __in6_dev_get_rtnl_net() that uses rtnl_net_dereference().

We can add the RCU version helper later if needed.

Signed-off-by: Kuniyuki Iwashima <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: q2ven

include/net/addrconf.h

@@ -347,6 +347,11 @@ static inline struct inet6_dev *__in6_dev_get(const struct net_device *dev)
 	return rcu_dereference_rtnl(dev->ip6_ptr);
 }
 
+static inline struct inet6_dev *__in6_dev_get_rtnl_net(const struct net_device *dev)
+{
+	return rtnl_net_dereference(dev_net(dev), dev->ip6_ptr);
+}
+
 /**
  * __in6_dev_stats_get - get inet6_dev pointer for stats
  * @dev: network device