Re: [PATCH bpf-next] netkit: Add some ethtool ops to provide information to user

[Daniel Borkmann]

On 12/1/23 9:42 AM, Feng Zhou wrote:
> 在 2023/11/30 18:56, Daniel Borkmann 写道:
> > On 11/30/23 10:24 AM, Feng Zhou wrote:
> > > 在 2023/11/30 17:06, Nikolay Aleksandrov 写道:
> > > > On 11/30/23 09:58, Feng zhou wrote:
> > > > > From: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
> > > > >
> > > > > Add get_strings, get_sset_count, get_ethtool_stats to get peer
> > > > > ifindex.
> > > > > ethtool -S nk1
> > > > > NIC statistics:
> > > > >       peer_ifindex: 36
> > > > >
> > > > > Add get_link, get_link_ksettings to get link stat.
> > > > > ethtool nk1
> > > > > Settings for nk1:
> > > > >     ...
> > > > >     Link detected: yes
> > > > >
> > > > > Add get_ts_info.
> > > > > ethtool -T nk1
> > > > > Time stamping parameters for nk1:
> > > > > ...
> > > > >
> > > > > Signed-off-by: Feng Zhou <zhoufeng.zf@xxxxxxxxxxxxx>
> > > > > ---
> > > > >   drivers/net/netkit.c | 53 ++++++++++++++++++++++++++++++++++++++++++++
> > > > >   1 file changed, 53 insertions(+)
> > > >
> > > > I don't see any point in sending peer_ifindex through ethtool, even
> > > > worse through ethtool stats. That is definitely the wrong place for it.
> > > > You can already retrieve that through netlink. About the speed/duplex
> > > > this one makes more sense, but this is the wrong way to do it.
> > > > See how we did it for virtio_net (you are free to set speed/duplex
> > > > to anything to please bonding for example). Although I doubt anyone will use netkit with bonding, so even that is questionable. :)
> > > >
> > > > Nacked-by: Nikolay Aleksandrov <razor@xxxxxxxxxxxxx>
> > >
> > > We use netkit to replace veth to improve performance, veth can be used ethtool -S veth to get peer_ifindex, so this part is added, as long as it is to keep the netkit part and veth unified, to ensure the same usage habits, and to replace it without perception.
> >
> > Could you elaborate some more on the use case why you need to retrieve it
> > via ethtool, what alternatives were tried and don't work?
> >
> > Please also elaborate on the case for netkit_get_link_ksettings() and which
> > concrete problem you are trying to address with this extension?
> >
> > The commit message only explains what is done but does not go into the detail
> > of _why_ you need it.
>
> In general, this information can be obtained through ip commands or netlink, and netkit_get_link_ksettings really not necessary. The reason why ethtool supports this is that when we use veth, our business colleagues are used to using ethtool to obtain peer_ifindex, and then replace netkit, found that it could not be used, resulting in their script failure, so they asked us for a request.

Thanks, so the netkit_get_link_ksettings is optional. I don't quite follow what you
mean with regards to your business logic in veth to obtain peer ifindex. What does
the script do exactly with the peer ifindex (aka /why/ is it needed), could you
elaborate some more - it's still somewhat too vague? :) E.g. why it does not suffice
to look at the device type or other kind of attributes?

Thanks,
Daniel