Re: [PATCH net-next 0/3] vsock: support network namespace

Jason Wang
2025-03-11T01:00:00Z

On Tue, Mar 11, 2025 at 4:14 AM Bobby Eshleman <bobbyeshleman@gmail.com> wrote:
>
> On Wed, Mar 05, 2025 at 01:46:54PM +0800, Jason Wang wrote:
> > On Wed, Mar 5, 2025 at 8:39 AM Bobby Eshleman <bobbyeshleman@gmail.com> wrote:
> > >
> > > On Tue, Apr 28, 2020 at 06:00:52PM +0200, Stefano Garzarella wrote:
> > > > On Tue, Apr 28, 2020 at 04:13:22PM +0800, Jason Wang wrote:
> > >
> > > WRT netdev, do we foresee big gains beyond just leveraging the netdev's
> > > namespace?
> >
> > It's a leverage of the network subsystem (netdevice, steering, uAPI,
> > tracing, probably a lot of others), not only its namespace. It can
> > avoid duplicating existing mechanisms in a vsock specific way. If we
> > manage to do that, namespace support will be a "byproduct".
> >
> [...]
> >
> > Yes, it can. I think we need to evaluate both approaches (that's why I
> > raise the approach of reusing netdevice). We can hear from others.
> >
>
> I agree it is worth evaluating. If netdev is being considered, then it
> is probably also worth considering your suggestion from a few years back
> to add these capabilities by building vsock on top of virtio-net [1].
>
> [1] https://lore.kernel.org/all/2747ac1f-390e-99f9-b24e-f179af79a9da@redhat.com/

Yes. I think having a dedicated netdev might be simpler than reusing
the virito-net.

>
> Considering that the current vsock protocol will only ever be able to
> enjoy a restricted feature set of these other net subsystems due to its
> lack of tolerance for packet loss (e.g., no multiqueue steering, no
> packet scheduling), I wonder if it would be best to a) wait until a user
> requires these capabilities, and b) at that point extend vsock to tolerate
> packet loss (add a seqnum)?

Maybe, a question back to this proposal. What's the plan for the
userspace? For example, do we expect to extend iproute2 and other and
how (e.g having a new vsock dedicated tool)?

>
> > >
> > > Some other thoughts I had: netdev's flow control features would all have
> > > to be ignored or disabled somehow (I think dev_direct_xmit()?), because
> > > queueing introduces packet loss and the vsock protocol is unable to
> > > survive packet loss.
> >
> > Or just allow it and then configuring a qdisc that may drop packets
> > could be treated as a misconfiguration.
> >
>
> That is possible, but when I was playing with vsock qdisc the only one
> that worked was pfifo_fast/pfifo, as the others that I tested async drop
> packets.

I guess it should work with qdiscs with TCQ_F_CAN_BYPASS. Or if it
turns out to be hard we can just bypass the qdisc layer as you said.

Thanks

>
> Thanks,
> Bobby
>