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

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Message-ID: <CACGkMEtptFWx_v-14e1LM31XH+fOh4U-VO7gZKyqb1J1KM4uag@mail.gmail.com>
Date: Tue, 11 Mar 2025 08:54:55 +0800
From: Jason Wang <jasowang@...hat.com>
To: Stefano Garzarella <sgarzare@...hat.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>, Bobby Eshleman <bobbyeshleman@...il.com>, 
	Jakub Kicinski <kuba@...nel.org>, davem@...emloft.net, 
	Stefan Hajnoczi <stefanha@...hat.com>, linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	virtualization@...ts.linux-foundation.org, linux-hyperv@...r.kernel.org, 
	Dexuan Cui <decui@...rosoft.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 0/3] vsock: support network namespace

On Mon, Mar 10, 2025 at 10:15 PM Stefano Garzarella <sgarzare@...hat.com> wrote:
>
> On Thu, 6 Mar 2025 at 01:17, Jason Wang <jasowang@...hat.com> wrote:
> >
> > On Wed, Mar 5, 2025 at 5:30 PM Stefano Garzarella <sgarzare@...hat.com> wrote:
> > >
> > > On Wed, Mar 05, 2025 at 02:27:12AM -0500, Michael S. Tsirkin wrote:
> > > >On Tue, Mar 04, 2025 at 04:39:02PM -0800, Bobby Eshleman wrote:
> > > >> I think it might be a lot of complexity to bring into the picture from
> > > >> netdev, and I'm not sure there is a big win since the vsock device could
> > > >> also have a vsock->net itself? I think the complexity will come from the
> > > >> address translation, which I don't think netdev buys us because there
> > > >> would still be all of the work work to support vsock in netfilter?
> > > >
> > > >Ugh.
> > > >
> > > >Guys, let's remember what vsock is.
> > > >
> > > >It's a replacement for the serial device with an interface
> > > >that's easier for userspace to consume, as you get
> > > >the demultiplexing by the port number.
> >
> > Interesting, but at least VSOCKETS said:
> >
> > """
> > config VSOCKETS
> >         tristate "Virtual Socket protocol"
> >         help
> >          Virtual Socket Protocol is a socket protocol similar to TCP/IP
> >           allowing communication between Virtual Machines and hypervisor
> >           or host.
> >
> >           You should also select one or more hypervisor-specific transports
> >           below.
> >
> >           To compile this driver as a module, choose M here: the module
> >           will be called vsock. If unsure, say N.
> > """
> >
> > This sounds exactly like networking stuff and spec also said something similar
> >
> > """
> > The virtio socket device is a zero-configuration socket communications
> > device. It facilitates data transfer between the guest and device
> > without using the Ethernet or IP protocols.
> > """
> >
> > > >
> > > >The whole point of vsock is that people do not want
> > > >any firewalling, filtering, or management on it.
> >
> > We won't get this, these are for ethernet and TCP/IP mostly.
> >
> > > >
> > > >It needs to work with no configuration even if networking is
> > > >misconfigured or blocked.
> >
> > I don't see any blockers that prevent us from zero configuration, or I
> > miss something?
> >
> > >
> > > I agree with Michael here.
> > >
> > > It's been 5 years and my memory is bad, but using netdev seemed like a
> > > mess, especially because in vsock we don't have anything related to
> > > IP/Ethernet/ARP, etc.
> >
> > We don't need to bother with that, kernel support protocols other than TCP/IP.
>
> Do we have an example of any other non-Ethernet device that uses
> netdev? Just to see what we should do.

Yes, I think can device is one example and it should have others.

>
> I'm not completely against the idea, but from what I remember when I
> looked at it five years ago, it wasn't that easy and straightforward
> to use.

Can just hook the packets into its own stack, maybe vsock can do the same.

>
> >
> > >
> > > I see vsock more as AF_UNIX than netdev.
> >
> > But you have a device in guest that differs from the AF_UNIX.
>
> Yes, but the device is simply for carrying messages.
> Another thing that makes me think of AF_UNIX is the hybrid-vsock
> developed by Firecracker [1] that we also reused in vhost-user-vsock
> [2], where the mapping between AF_VSOCK and AF_UNIX is really
> implemented.

I see. But the main difference is that vsock can work across the
boundary of guest and host. This makes it hard to be a 100% socket
implementation in the guest.

Thanks

>
> Thanks,
> Stefano
>
> [1] https://github.com/firecracker-microvm/firecracker/blob/main/docs/vsock.md#firecracker-virtio-vsock-design
> [2] https://github.com/rust-vmm/vhost-device/tree/main/vhost-device-vsock
>