[PATCH net-next] net/core: ensure features get disabled on new lower devs

From: Jarod Wilson
Date: Tue Nov 03 2015 - 15:37:23 EST

With moving netdev_sync_lower_features() after the .ndo_set_features
calls, I neglected to verify that devices added *after* a flag had been
disabled on an upper device were properly added with that flag disabled as
well. This currently happens, because we exit __netdev_update_features()
when we see dev->features == features for the upper dev. We can retain the
optimization of leaving without calling .ndo_set_features with a bit of
tweaking and a goto here.

Changing err to ret was somewhat arbitrary and makes the patch look more
involved, but seems to better fit the altered use.

Fixes: fd867d51f ("net/core: generic support for disabling netdev features down stack")
CC: "David S. Miller" <davem@xxxxxxxxxxxxx>
CC: Eric Dumazet <edumazet@xxxxxxxxxx>
CC: Jay Vosburgh <j.vosburgh@xxxxxxxxx>
CC: Veaceslav Falico <vfalico@xxxxxxxxx>
CC: Andy Gospodarek <gospo@xxxxxxxxxxxxxxxxxxx>
CC: Jiri Pirko <jiri@xxxxxxxxxxx>
CC: Nikolay Aleksandrov <razor@xxxxxxxxxxxxx>
CC: Michal Kubecek <mkubecek@xxxxxxx>
CC: Alexander Duyck <alexander.duyck@xxxxxxxxx>
CC: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Jarod Wilson <jarod@xxxxxxxxxx>
net/core/dev.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 8ce3f74..90e0a62 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6402,7 +6402,7 @@ int __netdev_update_features(struct net_device *dev)
struct net_device *upper, *lower;
netdev_features_t features;
struct list_head *iter;
- int err = 0;
+ int ret = 0;


@@ -6419,31 +6419,34 @@ int __netdev_update_features(struct net_device *dev)
features = netdev_sync_upper_features(dev, upper, features);

if (dev->features == features)
- return 0;
+ goto sync_lower;

netdev_dbg(dev, "Features changed: %pNF -> %pNF\n",
&dev->features, &features);

if (dev->netdev_ops->ndo_set_features)
- err = dev->netdev_ops->ndo_set_features(dev, features);
+ ret = dev->netdev_ops->ndo_set_features(dev, features);

- if (unlikely(err < 0)) {
+ if (unlikely(ret < 0)) {
"set_features() failed (%d); wanted %pNF, left %pNF\n",
- err, &features, &dev->features);
+ ret, &features, &dev->features);
return -1;

+ if (!ret) {
+ dev->features = features;
+ ret = 1;
+ }
/* some features must be disabled on lower devices when disabled
* on an upper device (think: bonding master or bridge)
netdev_for_each_lower_dev(dev, lower, iter)
netdev_sync_lower_features(dev, lower, features);

- if (!err)
- dev->features = features;
- return 1;
+ return ret;


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