Reviewing #512771 got me thinking and I'm not sure I see a good reason
to keep this method given the SSH backdoor functionality has a much
better UX.
I'd propose we deprecate it, await 26.11 to see if people complain and
remove it alltogether after that.
This allows the type's return value to be accessed more easily.
Motivating use case:
- Built-in module provides CLI functionality by declaring
an `attrListWith { asAttrs = true; }`, extracting the ordered list
from `valueMeta` for the purpose of creating the `argv`.
- User modules can read the command line's flags directly without
having to parse the list of attrs.
This adds a type for name-value mappings that preserve ordering.
Motivating use case: command line flags for package modules /
wrappers / modular services.
The option value can be transformed into a command line in the
correct order.
Additionally, a convenience readOnly option could be provided
to give easy introspection access to the values in an ad hoc
manner.
`vhost-device-vsock`[1] is a custom implementation of AF_VSOCK, but the
application on the host-side uses a UNIX domain-socket. This gives us
the following nice properties:
* We don't need to do `--arg sandbox-paths /dev/vhost-vsock` anymore for
debugging builds within the sandbox. That means, untrusted users can
also debug these kinds of tests now.
* This prevents CID conflicts on the host-side, i.e. there's no need for
using `sshBackdoor.vsockOffset` for tests anymore.
A big shout-out goes to Allison Karlitskaya, the developer of test.thing[2]
who talked about this approach to do AF_VSOCK on All Systems Go 2025.
This patch requires systemd 258[3] because this contains `vhost-mux` in
its SSH config which is needed to connect to the VMs from now on.
To not blow up the patches even more, this only uses AF_VSOCK for the
debugger. A potential follow-up for the future would be a removal of the
current `backdoor.service` and replace it entirely by this
functionality.
The internal implementation tries to be consistent with how VLANs and
machines are handled, i.e. the processes are started when the Driver's
context is entered and cleaned up in __exit__().
I decided to push the process management and creation of sockets for
vhost-device-vsock into its own class, that's an implementation detail
and not a concern for the test-driver. In fact, `vhost-device-vsock` is
something we can drop once QEMU implements native support for using
AF_UNIX on the host-side[4]. `VsockPair` is its own class since
returning e.g. a triple of `(Path, Path, Int)` would be ambiguous in
what is the guest and what the host path (and frankly, I found it hard
to distinguish the two when reading the docs of `vhost-device-vsock`
initially).
Finally, now that we can do the SSH backdoor without adding additional
devices to the sandbox, I figured, it's time to write a test-case for
it.
[1] https://github.com/rust-vmm/vhost-device/blob/main/vhost-device-vsock/README.md
[2] https://codeberg.org/lis/test.thing
[3] https://github.com/NixOS/nixpkgs/pull/427968
[4] https://gitlab.com/qemu-project/qemu/-/issues/2095
This deprecation is part of a bigger effort to deprecate activation scripts altogether, which will take place over several releases.
There are no in-tree usages of the now-deprecated reload/restart functionality.
This is a follow-up for #460057 to completely remove all mentions of nixos.org/channels/.
The following command was used to generate this change:
```
find . -type f -exec sed -i 's|nixos.org/channels/|channels.nixos.org/|g' {} +
```
As discussed with tfc before, it's probably better in most cases to try
the interactive test-driver with the SSH backdoor first and resort to
this feature for flaky tests.
Without a proper introduction it's really really hard to make sense of the examples, and where values come from; which are arbitrary, which are conventional, which are hard-coded into some part of the framework.
Co-authored-by: Valentin Gagarin <valentin@gagarin.work>
