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Date: Thu, 26 Jul 2007 17:09:36 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
Patrick McHardy <kaber@...sh.net>,
Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH 4/6] [NET]: Allow netdev REGISTER/CHANGENAME events to fail
[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@...dor.apana.org.au>
---
include/linux/notifier.h | 13 +++++++++
net/core/dev.c | 62 +++++++++++++++++++++++++++++++++++++++--------
2 files changed, 65 insertions(+), 10 deletions(-)
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index be3f2bb..fad7ff1 100644
--- 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 0a35c15..d94b178 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;
}
/**
@@ -3430,9 +3471,10 @@ 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;
-
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