net: make dev_set_mtu() honor notification return code
Currently, after changing the MTU for a device, dev_set_mtu() calls
NETDEV_CHANGEMTU notification, however doesn't verify it's return code -
which can be NOTIFY_BAD - i.e. some of the net notifier blocks refused this
change, and continues nevertheless.
To fix this, verify the return code, and if it's an error - then revert the
MTU to the original one, notify again and pass the error code.
CC: Jiri Pirko <jiri@resnulli.us>
CC: "David S. Miller" <davem@davemloft.net>
CC: Eric Dumazet <edumazet@google.com>
CC: Alexander Duyck <alexander.h.duyck@intel.com>
CC: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
Reviewed-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index a828015..87312dc 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5300,6 +5300,17 @@
}
EXPORT_SYMBOL(dev_change_flags);
+static int __dev_set_mtu(struct net_device *dev, int new_mtu)
+{
+ const struct net_device_ops *ops = dev->netdev_ops;
+
+ if (ops->ndo_change_mtu)
+ return ops->ndo_change_mtu(dev, new_mtu);
+
+ dev->mtu = new_mtu;
+ return 0;
+}
+
/**
* dev_set_mtu - Change maximum transfer unit
* @dev: device
@@ -5309,8 +5320,7 @@
*/
int dev_set_mtu(struct net_device *dev, int new_mtu)
{
- const struct net_device_ops *ops = dev->netdev_ops;
- int err;
+ int err, orig_mtu;
if (new_mtu == dev->mtu)
return 0;
@@ -5322,14 +5332,20 @@
if (!netif_device_present(dev))
return -ENODEV;
- err = 0;
- if (ops->ndo_change_mtu)
- err = ops->ndo_change_mtu(dev, new_mtu);
- else
- dev->mtu = new_mtu;
+ orig_mtu = dev->mtu;
+ err = __dev_set_mtu(dev, new_mtu);
- if (!err)
- call_netdevice_notifiers(NETDEV_CHANGEMTU, dev);
+ if (!err) {
+ err = call_netdevice_notifiers(NETDEV_CHANGEMTU, dev);
+ err = notifier_to_errno(err);
+ if (err) {
+ /* setting mtu back and notifying everyone again,
+ * so that they have a chance to revert changes.
+ */
+ __dev_set_mtu(dev, orig_mtu);
+ call_netdevice_notifiers(NETDEV_CHANGEMTU, dev);
+ }
+ }
return err;
}
EXPORT_SYMBOL(dev_set_mtu);
