rtnetlink: allow to register ops without ops->setup set

So far, it is assumed that ops->setup is filled up. But there might be
case that ops might make sense even without ->setup. In that case,
forbid to newlink and dellink.

This allows to register simple rtnl link ops containing only ->kind.
That allows consistent way of passing device kind (either device-kind or
slave-kind) to userspace.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 2 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 1063996f8317..27acaf7ff6d7 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -299,7 +299,12 @@ int __rtnl_link_register(struct rtnl_link_ops *ops)
         if (rtnl_link_ops_get(ops->kind))
                 return -EEXIST;
 
-        if (!ops->dellink)
+        /* The check for setup is here because if ops
+         * does not have that filled up, it is not possible
+         * to use the ops for creating device. So do not
+         * fill up dellink as well. That disables rtnl_dellink.
+         */
+        if (ops->setup && !ops->dellink)
                 ops->dellink = unregister_netdevice_queue;
 
         list_add_tail(&ops->list, &link_ops);
@@ -1777,7 +1782,7 @@ static int rtnl_dellink(struct sk_buff *skb, struct nlmsghdr *nlh)
                 return -ENODEV;
 
         ops = dev->rtnl_link_ops;
-        if (!ops)
+        if (!ops || !ops->dellink)
                 return -EOPNOTSUPP;
 
         ops->dellink(dev, &list_kill);
@@ -2038,6 +2043,9 @@ replay:
                         return -EOPNOTSUPP;
                 }
 
+                if (!ops->setup)
+                        return -EOPNOTSUPP;
+
                 if (!ifname[0])
                         snprintf(ifname, IFNAMSIZ, "%s%%d", ops->kind);