netdev - Re: [PATCH v2] vlan: allow TSO setting on vlan interfaces

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Date:	Thu, 08 Jul 2010 18:00:30 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Patrick McHardy <kaber@...sh.net>
Subject: Re: [PATCH v2] vlan: allow TSO setting on vlan interfaces

Le jeudi 08 juillet 2010 à 16:49 +0100, Ben Hutchings a écrit :
> On Thu, 2010-07-08 at 16:43 +0100, Ben Hutchings wrote:
> > On Thu, 2010-07-08 at 11:39 +0200, Eric Dumazet wrote:
> > > When we need to shape traffic with low speeds, we need to disable tso on
> > > network interface :
> > > 
> > > ethtool -K eth0.2240 tso off
> > > 
> > > It seems vlan interfaces miss the set_tso() ethtool method.
> > > Propagating tso changes from lower device is not always wanted, some
> > > vlans want TSO on, others want TSO off.
> [...]
> > I think the vlan driver should also have a netdev notifier to handle
> > feature changes on the underlying device.
> 
> To clarify, I think offload features should be disabled on a vlan device
> if they are later disabled on the underlying device.  Propagating
> changes to enable features, as you say, might not be wanted.

OK, but isnt it already done ?

Check vlan_transfer_features() in net/8021q/vlan.c


# ethtool -k eth3|grep tcp-segmentation
tcp-segmentation-offload: on
# ethtool -k eth3.103|grep tcp-segmentation
tcp-segmentation-offload: on

# ethtool -K eth3 tso off

# ethtool -k eth3|grep tcp-segmentation
tcp-segmentation-offload: off
# ethtool -k eth3.103|grep tcp-segmentation
tcp-segmentation-offload: off

# ethtool -K eth3 tso on
# ethtool -k eth3.103|grep tcp-segmentation
tcp-segmentation-offload: on


We should not change it to avoid ORing TSO, it might break some setups.



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