rtnetlink: move type calculation out of loop

[ Upstream commit 87ccbb1f ]

I don't see how the type - which is one of
RTM_{GETADDR,GETROUTE,GETNETCONF} - can change. So do the message type
calculation once before entering the for loop.
Signed-off-by: Christian Brauner <christian@brauner.io>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

net/core/rtnetlink.c

@@ -3268,13 +3268,13 @@ static int rtnl_dump_all(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	int idx;
 	int s_idx = cb->family;
+	int type = cb->nlh->nlmsg_type - RTM_BASE;
 
 	if (s_idx == 0)
 		s_idx = 1;
 
 	for (idx = 1; idx <= RTNL_FAMILY_MAX; idx++) {
 		struct rtnl_link **tab;
-		int type = cb->nlh->nlmsg_type-RTM_BASE;
 		struct rtnl_link *link;
 		rtnl_dumpit_func dumpit;