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Commit fcc5a03a authored by Herbert Xu's avatar Herbert Xu Committed by David S. Miller
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[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: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent aeed9e82

include/linux/notifier.h

+13 −0
Original line number Diff line number Diff line
@@ -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

net/core/dev.c

+52 −10
Original line number Diff line number Diff line
@@ -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) {

	if (err)

		goto unlock;



	for_each_netdev(dev) {

			nb->notifier_call(nb, NETDEV_REGISTER, dev);

		err = nb->notifier_call(nb, NETDEV_REGISTER, dev);

		err = notifier_to_errno(err);

		if (err)

			goto rollback;



		if (!(dev->flags & IFF_UP))

			continue;



			if (dev->flags & IFF_UP)

		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;