netdev - [PATCH] net: drop NETIF_F_GSO from hw_features without NETIF_F

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Message-ID: <20110318195030.GA22350@core.hellgate.ch>
Date:	Fri, 18 Mar 2011 20:50:30 +0100
From:	Roger Luethi <rl@...lgate.ch>
To:	netdev@...r.kernel.org
Cc:	mirqus@...il.com
Subject: [PATCH] net: drop NETIF_F_GSO from hw_features without NETIF_F_SG

register_netdevice() removes NETIF_F_GSO from dev->features and
dev->wanted_features for hardware without NETIF_F_SG to "avoid warning from
netdev_fix_features()".

However, as the flag remains set in dev->hw_features, users trying to
enable GSO via ethtool will still end up with NETIF_F_GSO stuck in
wanted_features, resulting in a warning every time they try to change any
feature (until they use ethtool to "disable" GSO):

# ethtool -K eth2 gso on
via-rhine 0000:03:00.0: eth2: Dropping NETIF_F_GSO since no SG feature.
# ethtool -K eth2 rx on
via-rhine 0000:03:00.0: eth2: Dropping NETIF_F_GSO since no SG feature.
via-rhine 0000:03:00.0: eth2: Features changed: 0x00004380 -> 0x20004380
# ethtool -K eth2 rx off
via-rhine 0000:03:00.0: eth2: Dropping NETIF_F_GSO since no SG feature.
via-rhine 0000:03:00.0: eth2: Features changed: 0x20004380 -> 0x00004380
# ethtool -K eth2 gso off
#

With NETIF_F_GSO depending on NETIF_F_SG, it seems we should not
advertise the former as a changeable option if the latter is missing.
---
 net/core/dev.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 0d39032..122d4ca 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5433,6 +5433,7 @@ int register_netdevice(struct net_device *dev)

 	/* Avoid warning from netdev_fix_features() for GSO without SG */
 	if (!(dev->wanted_features & NETIF_F_SG)) {
+		dev->hw_features &= ~NETIF_F_GSO;
 		dev->wanted_features &= ~NETIF_F_GSO;
 		dev->features &= ~NETIF_F_GSO;
 	}
-- 
1.7.3.4

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