net: Push capable(CAP_NET_ADMIN) into the rtnl methods

- In rtnetlink_rcv_msg convert the capable(CAP_NET_ADMIN) check
  to ns_capable(net->user-ns, CAP_NET_ADMIN).  Allowing unprivileged
  users to make netlink calls to modify their local network
  namespace.

- In the rtnetlink doit methods add capable(CAP_NET_ADMIN) so
  that calls that are not safe for unprivileged users are still
  protected.

Later patches will remove the extra capable calls from methods
that are safe for unprivilged users.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index f1c0c2e..7adcdaf 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1620,6 +1620,9 @@
 	struct net_device *dev = NULL;
 	int err = -EINVAL;
 
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
 	ASSERT_RTNL();
 	if (nlmsg_len(nlh) < sizeof(*ndm))
 		goto out;
@@ -1684,6 +1687,9 @@
 	struct net_device *dev = NULL;
 	int err;
 
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
 	ASSERT_RTNL();
 	err = nlmsg_parse(nlh, sizeof(*ndm), tb, NDA_MAX, NULL);
 	if (err < 0)
@@ -1962,6 +1968,9 @@
 	struct nlattr *tb[NDTA_MAX+1];
 	int err;
 
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
 	err = nlmsg_parse(nlh, sizeof(*ndtmsg), tb, NDTA_MAX,
 			  nl_neightbl_policy);
 	if (err < 0)