net: add support for netdev notifier error injection

This module allows to insert errors in some of netdevice's notifier
events. All network drivers use these notifiers to signal various events
and to check if they are allowed, e.g. PRECHANGEMTU and CHANGEMTU
afterwards. Until recently I had to run failure tests by injecting
a custom module, but now this infrastructure makes it trivial to test
these failure paths. Some of the recent bugs I fixed were found using
this module.
Here's an example:
 $ cd /sys/kernel/debug/notifier-error-inject/netdev
 $ echo -22 > actions/NETDEV_CHANGEMTU/error
 $ ip link set eth0 mtu 1024
 RTNETLINK answers: Invalid argument

CC: Akinobu Mita <akinobu.mita@gmail.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: netdev <netdev@vger.kernel.org>
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 24 insertions, 0 deletions

diff --git a/Documentation/fault-injection/notifier-error-inject.txt b/Documentation/fault-injection/notifier-error-inject.txt
index 09adabef513f..71e638a4c497 100644
--- a/Documentation/fault-injection/notifier-error-inject.txt
+++ b/Documentation/fault-injection/notifier-error-inject.txt
@@ -10,6 +10,7 @@ modules that can be used to test the following notifiers.
  * PM notifier
  * Memory hotplug notifier
  * powerpc pSeries reconfig notifier
+ * Netdevice notifier
 
 CPU notifier error injection module
 -----------------------------------
@@ -87,6 +88,29 @@ Possible pSeries reconfig notifier events to be failed are:
  * PSERIES_DRCONF_MEM_ADD
  * PSERIES_DRCONF_MEM_REMOVE
 
+Netdevice notifier error injection module
+----------------------------------------------
+This feature is controlled through debugfs interface
+/sys/kernel/debug/notifier-error-inject/netdev/actions/<notifier event>/error
+
+Netdevice notifier events which can be failed are:
+
+ * NETDEV_REGISTER
+ * NETDEV_CHANGEMTU
+ * NETDEV_CHANGENAME
+ * NETDEV_PRE_UP
+ * NETDEV_PRE_TYPE_CHANGE
+ * NETDEV_POST_INIT
+ * NETDEV_PRECHANGEMTU
+ * NETDEV_PRECHANGEUPPER
+
+Example: Inject netdevice mtu change error (-22 == -EINVAL)
+
+        # cd /sys/kernel/debug/notifier-error-inject/netdev
+        # echo -22 > actions/NETDEV_CHANGEMTU/error
+        # ip link set eth0 mtu 1024
+        RTNETLINK answers: Invalid argument
+
 For more usage examples
 -----------------------
 There are tools/testing/selftests using the notifier error injection features