missing bits of net-namespace / sysctl

Piss-poor sysctl registration API strikes again, film at 11...

What we really need is _pathname_ required to be present in already
registered table, so that kernel could warn about bad order.  That's the
next target for sysctl stuff (and generally saner and more explicit
order of initialization of ipv[46] internals wouldn't hurt either).

For the time being, here are full fixups required by ..._rotable()
stuff; we make per-net sysctl sets descendents of "ro" one and make sure
that sufficient skeleton is there before we start registering per-net
sysctls.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

net/ipv6/sysctl_net_ipv6.c

@@ -150,3 +150,19 @@ void ipv6_sysctl_unregister(void)
 	unregister_net_sysctl_table(ip6_header);
 	unregister_pernet_subsys(&ipv6_sysctl_net_ops);
 }
+
+static struct ctl_table_header *ip6_base;
+
+int ipv6_static_sysctl_register(void)
+{
+	static struct ctl_table empty[1];
+	ip6_base = register_net_sysctl_rotable(net_ipv6_ctl_path, empty);
+	if (ip6_base == NULL)
+		return -ENOMEM;
+	return 0;
+}
+
+void ipv6_static_sysctl_unregister(void)
+{
+	unregister_net_sysctl_table(ip6_base);
+}