[NET]: Allow netdev REGISTER/CHANGENAME events to fail

This patch adds code to allow errors to be passed up from event
handlers of NETDEV_REGISTER and NETDEV_CHANGENAME.  It also adds
the notifier_from_errno/notifier_to_errnor helpers to pass the
errno value up to the notifier caller.

If an error is detected when a device is registered, it causes
that operation to fail.  A NETDEV_UNREGISTER will be sent to
all event handlers.

Similarly if NETDEV_CHANGENAME fails the original name is restored
and a new NETDEV_CHANGENAME event is sent.

As such all event handlers must be idempotent with respect to
these events.

When an event handler is registered NETDEV_REGISTER events are
sent for all devices currently registered.  Should any of them
fail, we will send NETDEV_GOING_DOWN/NETDEV_DOWN/NETDEV_UNREGISTER
events to that handler for the devices which have already been
registered with it.  The handler registration itself will fail.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 52 insertions, 10 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 346cbf66534e..6cc8a70350ac 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -817,7 +817,9 @@ int dev_alloc_name(struct net_device *dev, const char *name)
  */
 int dev_change_name(struct net_device *dev, char *newname)
 {
+        char oldname[IFNAMSIZ];
         int err = 0;
+        int ret;
 
         ASSERT_RTNL();
 
@@ -827,6 +829,8 @@ int dev_change_name(struct net_device *dev, char *newname)
         if (!dev_valid_name(newname))
                 return -EINVAL;
 
+        memcpy(oldname, dev->name, IFNAMSIZ);
+
         if (strchr(newname, '%')) {
                 err = dev_alloc_name(dev, newname);
                 if (err < 0)
@@ -838,6 +842,7 @@ int dev_change_name(struct net_device *dev, char *newname)
         else
                 strlcpy(dev->name, newname, IFNAMSIZ);
 
+rollback:
         device_rename(&dev->dev, dev->name);
 
         write_lock_bh(&dev_base_lock);
@@ -845,7 +850,20 @@ int dev_change_name(struct net_device *dev, char *newname)
         hlist_add_head(&dev->name_hlist, dev_name_hash(dev->name));
         write_unlock_bh(&dev_base_lock);
 
-        raw_notifier_call_chain(&netdev_chain, NETDEV_CHANGENAME, dev);
+        ret = raw_notifier_call_chain(&netdev_chain, NETDEV_CHANGENAME, dev);
+        ret = notifier_to_errno(ret);
+
+        if (ret) {
+                if (err) {
+                        printk(KERN_ERR
+                               "%s: name change rollback failed: %d.\n",
+                               dev->name, ret);
+                } else {
+                        err = ret;
+                        memcpy(dev->name, oldname, IFNAMSIZ);
+                        goto rollback;
+                }
+        }
 
         return err;
 }
@@ -1058,20 +1076,43 @@ int dev_close(struct net_device *dev)
 int register_netdevice_notifier(struct notifier_block *nb)
 {
         struct net_device *dev;
+        struct net_device *last;
         int err;
 
         rtnl_lock();
         err = raw_notifier_chain_register(&netdev_chain, nb);
-        if (!err) {
-                for_each_netdev(dev) {
-                        nb->notifier_call(nb, NETDEV_REGISTER, dev);
+        if (err)
+                goto unlock;
 
-                        if (dev->flags & IFF_UP)
-                                nb->notifier_call(nb, NETDEV_UP, dev);
-                }
+        for_each_netdev(dev) {
+                err = nb->notifier_call(nb, NETDEV_REGISTER, dev);
+                err = notifier_to_errno(err);
+                if (err)
+                        goto rollback;
+
+                if (!(dev->flags & IFF_UP))
+                        continue;
+
+                nb->notifier_call(nb, NETDEV_UP, dev);
         }
+
+unlock:
         rtnl_unlock();
         return err;
+
+rollback:
+        last = dev;
+        for_each_netdev(dev) {
+                if (dev == last)
+                        break;
+
+                if (dev->flags & IFF_UP) {
+                        nb->notifier_call(nb, NETDEV_GOING_DOWN, dev);
+                        nb->notifier_call(nb, NETDEV_DOWN, dev);
+                }
+                nb->notifier_call(nb, NETDEV_UNREGISTER, dev);
+        }
+        goto unlock;
 }
 
 /**
@@ -3434,9 +3475,10 @@ int register_netdevice(struct net_device *dev)
         write_unlock_bh(&dev_base_lock);
 
         /* Notify protocols, that a new device appeared. */
-        raw_notifier_call_chain(&netdev_chain, NETDEV_REGISTER, dev);
-
-        ret = 0;
+        ret = raw_notifier_call_chain(&netdev_chain, NETDEV_REGISTER, dev);
+        ret = notifier_to_errno(ret);
+        if (ret)
+                unregister_netdevice(dev);
 
 out:
         return ret;