[Xen-API] Re: [ovs-dev] [Xen-devel] Re: [PATCH] ethtool: ETHTOOL_SFEATURES: remove NETIF_F_COMPAT return

[Jesse Gross <jesse@xxxxxxxxxx>]

2011/5/29 MichaÅ MirosÅaw <mirq-linux@xxxxxxxxxxxx>:
> On Sat, May 28, 2011 at 10:31:03AM -0700, Jesse Gross wrote:
>> 2011/5/28 Ian Campbell <Ian.Campbell@xxxxxxxxxx>:
>> > On Sat, 2011-05-28 at 08:35 +0100, MichaÅ MirosÅaw wrote:
>> >> On Sat, May 28, 2011 at 12:25:55AM +0100, Ben Hutchings wrote:
>> >> > On Fri, 2011-05-27 at 18:34 +0200, MichaÅ MirosÅaw wrote:
>> >> > > On Fri, May 27, 2011 at 04:45:50PM +0100, Ben Hutchings wrote:
>> >> > > > On Fri, 2011-05-27 at 17:28 +0200, MichaÅ MirosÅaw wrote:
>> >> > [...]
>> >> > > > > Â Â Â(note: ETHTOOL_S{SG,...} are not ever going away)
>> >> > > > > Â Â- causes NETIF_F_* to be an ABI
>> >> > > > If feature flag numbers are not stable then what is the point of
>> >> > > > /sys/class/net/<name>/features? ÂAlso, I'm not aware that features 
>> >> > > > have
>> >> > > > ever been renumbered in the past.
>> >> > > Since no NETIF_F_* were exported earlier, I assume 
>> >> > > /sys/class/net/*/features
>> >> > > is a debugging aid. What is it used for besides that?
>> >> > xen-api <https://github.com/xen-org/xen-api> uses it in
>> >> > scripts/InterfaceReconfigureVswitch.py. ÂThough it doesn't seem to be
>> >> > used for a particularly good reason...
>> >> Look like it should use ETHTOOL_GFLAGS instead for 
>> >> netdev_has_vlan_accel().
>> ETHTOOL_GFLAGS didn't expose the vlan acceleration flags until 2.6.37,
>> which is why /sys/class/net was used instead.
>
> https://github.com/xen-org/xen-api/commit/78b8078e6ae3cf48179859bed6350bb326987546
>
> The commit using it was introduced after 2.6.37 kernel was released

Well people do use kernels other than the most recently released one...

> and uses
> undocumented acccess path to the bits in question. What is the kernel patch
> this commit is referring to?

It's a temporary workaround to deal with the fact that many drivers
that support vlan acceleration do not properly handle vlan packets if
the corresponding group isn't configured on them.

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