netdev - [PATCH net] macvlan: filter out unsupported feature flags

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Message-Id: <1520554643-3024-1-git-send-email-shannon.nelson@oracle.com>
Date:   Thu,  8 Mar 2018 16:17:23 -0800
From:   Shannon Nelson <shannon.nelson@...cle.com>
To:     davem@...emloft.net, netdev@...r.kernel.org
Cc:     steffen.klassert@...unet.com
Subject: [PATCH net] macvlan: filter out unsupported feature flags

Adding a macvlan device on top of a lowerdev that supports
the xfrm offloads fails with a new regression:
  # ip link add link ens1f0 mv0 type macvlan
  RTNETLINK answers: Operation not permitted

Tracing down the failure shows that the macvlan device inherits
the NETIF_F_HW_ESP and NETIF_F_HW_ESP_TX_CSUM feature flags
from the lowerdev, but with no dev->xfrmdev_ops API filled
in, it doesn't actually support xfrm.  When the request is
made to add the new macvlan device, the XFRM listener for
NETDEV_REGISTER calls xfrm_api_check() which fails the new
registration because dev->xfrmdev_ops is NULL.

The macvlan creation succeeds when we filter out the ESP
feature flags in macvlan_fix_features(), so let's filter them
out like we're already filtering out ~NETIF_F_NETNS_LOCAL.
When XFRM support is added in the future, we can add the flags
into MACVLAN_FEATURES.

This same problem could crop up in the future with any other
new feature flags, so let's filter out any flags that aren't
defined as supported in macvlan.

Fixes: d77e38e612a0 ("xfrm: Add an IPsec hardware offloading API")
Reported-by: Alexey Kodanev <alexey.kodanev@...cle.com>
Signed-off-by: Shannon Nelson <shannon.nelson@...cle.com>
---
 drivers/net/macvlan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 8fc02d9..725f4b4 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -1036,7 +1036,7 @@ static netdev_features_t macvlan_fix_features(struct net_device *dev,
 	lowerdev_features &= (features | ~NETIF_F_LRO);
 	features = netdev_increment_features(lowerdev_features, features, mask);
 	features |= ALWAYS_ON_FEATURES;
-	features &= ~NETIF_F_NETNS_LOCAL;
+	features &= (ALWAYS_ON_FEATURES | MACVLAN_FEATURES);

 	return features;
 }
-- 
2.7.4