Re: [dpdk-dev] [PATCH 2/2] virtio: allow running w/o vlan filtering

[Stephen Hemminger <stephen@networkplumber.org>]

In Linux and BSD, if driver does not support filtering, the kernel takes
care of the situation.
A DPDK application will need a device layer; maybe some part of the
port/pipeline would
be a good place for it.

On Tue, Aug 4, 2015 at 6:01 PM, Ouyang, Changchun <
changchun.ouyang@intel.com> wrote:

>
> Hi Vincent,
>
> > -----Original Message-----
> > From: Vincent JARDIN [mailto:vincent.jardin@6wind.com]
> > Sent: Tuesday, August 4, 2015 8:52 PM
> > To: Thomas Monjalon; Ouyang, Changchun
> > Cc: dev@dpdk.org; Stephen Hemminger
> > Subject: Re: [dpdk-dev] [PATCH 2/2] virtio: allow running w/o vlan
> filtering
> >
> > Thomas, Changchun,
> >
> > On 29/07/2015 14:56, Thomas Monjalon wrote:
> > > Back on this old patch, it seems justified but nobody agreed.
> > >
> > > --- a/lib/librte_pmd_virtio/virtio_ethdev.c
> > > +++ b/lib/librte_pmd_virtio/virtio_ethdev.c
> > > @@ -1288,7 +1288,6 @@ virtio_dev_configure(struct rte_eth_dev *dev)
> > >              && !vtpci_with_feature(hw, VIRTIO_NET_F_CTRL_VLAN)) {
> > >                  PMD_DRV_LOG(NOTICE,
> > >                              "vlan filtering not available on this
> host");
> > > -               return -ENOTSUP;
> > >          }
> > >
> > > 2015-03-06 08:24, Stephen Hemminger:
> > >> "Ouyang, Changchun" <changchun.ouyang@intel.com> wrote:
> > >>>> From: Stephen Hemminger
> > >>>> Vlan filtering is an option, and not a requirement.
> > >>>> If host does not support filtering then it can be done in software.
> >
> > +1 with Stephen, remove return -ENOTSUP;
> >
> > applications must not fail, software stacks will handle it. We did
> experiment
> Do you mean handling it in software stack outside the virtio pmd?
> AFAIK, inside virtio PMD, we have no codes to handle it currently.
>
> > some issues when testpmd was failing while it was supposed to run. A
> notice
> > would be good enough.
> >
>
> Use '--disable-hw-vlan-filter'  in testpmd command line will allow it
> continue to work.
> You can have a try.
>
> >
> > >>>
> > >>> The question is that guest only send command, no real action to do
> the
> > vlan filter.
> > >>> So if both host and guest have no real action for vlan filter, who
> will do it?
> > >>
> > >> The virtio driver has features.
> > >> Guest can not send commands to host where feature bit not enabled.
> > >> Application can call filter_set and check if filter worked or not.
> > >>
> > >> Our code already had to do MAC and VLAN validation of incoming
> > >> packets therefore if hardware can't do vlan match, there is no
> problem.
> > >> I would expect other applications would do the same thing.
> > >>
> > >> Failing during configuration is bad. DPDK API should never force
> > >> application to play "guess the working configuration" with the device
> > >> driver or do string match on "which device is this anyway"
> >
> > Agree, it is not a failure of a configuration, it is a failure of
> negotiation of
> > virtio's capabilities.
>
> I am not sure which one is better when app configures one feature but fail
> to negotiate it with host(which means has
> no such capability to support this feature currently).
> 1)The driver cheat the app, and continue to do the rest of work(of course
> need some hints).
> 2)give hints and exit, then user re-run app with correct configuration.
>
> >
> > Let's use another example: we do not expect a guest kernel to panic()
> > because it is not properly negotiated? So why should a DPDK application
> fail
> > and return -ENOTSUP?
> I think user mode driver/app and kernel is different thing :-)
>
> Changchun
>
>