[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>

diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index be3f2bb6fcf39a6b4b911bb71158d04ef246bdb6..fad7ff17e468ded82fc2e797bc42f6bb4a2f95fe 100644 (file)
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -157,6 +157,19 @@ extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
  */
 #define NOTIFY_STOP            (NOTIFY_OK|NOTIFY_STOP_MASK)
 
+/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */
+static inline int notifier_from_errno(int err)
+{
+       return NOTIFY_STOP_MASK | (NOTIFY_OK - err);
+}
+
+/* Restore (negative) errno value from notify return value. */
+static inline int notifier_to_errno(int ret)
+{
+       ret &= ~NOTIFY_STOP_MASK;
+       return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0;
+}
+
 /*
  *     Declared notifiers so far. I can imagine quite a few more chains
  *     over time (eg laptop power reset chains, reboot chain (to clean 

diff --git a/net/core/dev.c b/net/core/dev.c
index 346cbf66534e3fce06abae3ec6cd536eb4d5526f..6cc8a70350ac05bb9526e244f7b5b427ee9d2ea1 100644 (file)
--- 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;