Re: [PATCH] conf: allow --fd 0

[Stefano Brivio <sbrivio@redhat.com>]

On Mon, 28 Apr 2025 14:36:02 +0200
Stefano Brivio <sbrivio@redhat.com> wrote:

> On Sat, 26 Apr 2025 10:44:25 +0200
> Alyssa Ross <hi@alyssa.is> wrote:
> 
> > inetd-style socket passing traditionally starts a service with a
> > connected socket on file descriptors 0 and 1.  passt disallowing
> > obtaining its socket from either of these descriptors made it
> > difficult to use with super-servers providing this interface — in my
> > case I wanted to use passt with s6-ipcserver[1].  
> 
> Hah, interesting usage, first report I've seen with s6. Is that to
> dispatch passt processes for a network / set of guests or something?

Never mind, I just found:

  https://spectrum-os.org/git/spectrum/commit/?id=aac74f6165740a6b041a7205ec86665744937a77

and related commits. I'm glad to see passt being useful there!

By the way, if it helps:

- you can actually use QEMU with e1000e and passt, it's somewhat slower
  than virtio-net (especially with vhost-user), about 1-2 Gbps in my
  experience, but perfectly usable. For a command line example, see:
  https://bugs.passt.top/show_bug.cgi?id=107#c0

- libkrun, which is somewhat similar to / shares some code with Cloud
  Hypervisor, also uses passt, like this:

    https://github.com/containers/libkrun/blob/main/src/devices/src/virtio/net/passt.rs

  ...that's without vhost-user support, so far. I had no idea you got
  Cloud Hypervisor and crosvm to use passt *with* vhost-user supprt,
  though. That looks like one step further :)

- muvm, which uses libkrun to run arbitrary commands in micro VMs (it
  has conceptually a couple of things in common with Qubes and Spectrum
  I guess), uses passt's NDP responder and DHCP server to configure its
  guest network:

    https://github.com/AsahiLinux/muvm/blob/dc874d4e6c261624b7c6cc9aab151d4d33d413ed/crates/muvm/src/guest/net.rs#L268

-- 
Stefano