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

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Message-ID: <CAGxU2F7SWG0m0KwODbKsbQipz6WzrRSuE1cUe6mYxZskqkbneQ@mail.gmail.com>
Date: Mon, 10 Mar 2025 15:14:59 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Jason Wang <jasowang@...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 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.

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.

>
> >
> > 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.

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