Now that 25c4dc5fd70 removed unregistering hooks and made them into
slices, just expose the slices and remove the setter funcs.
This removes boilerplate ceremony around adding new hooks.
This does export the hooks and make them mutable at runtime in theory,
but that'd be a data race. If we really wanted to lock it down in the
future we could make the feature.Hooks slice type be an opaque struct
with an All() iterator and a "frozen" bool and we could freeze all the
hooks after init. But that doesn't seem worth it.
This means that hook registration is also now all in one place, rather
than being mixed into ProfilesService vs ipnext.Host vs FooService vs
BarService. I view that as a feature. When we have a ton of hooks and
the list is long, then we can rearrange the fields in the Hooks struct
as needed, or make sub-structs, or big comments.
Updates #12614
Change-Id: I05ce5baa45a61e79c04591c2043c05f3288d8587
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
In this PR, we refactor the LocalBackend extension system, moving from direct callbacks to a more organized extension host model.
Specifically, we:
- Extract interface and callback types used by packages extending LocalBackend functionality into a new ipn/ipnext package.
- Define ipnext.Host as a new interface that bridges extensions with LocalBackend.
It enables extensions to register callbacks and interact with LocalBackend in a concurrency-safe, well-defined, and controlled way.
- Move existing callback registration and invocation code from ipnlocal.LocalBackend into a new type called ipnlocal.ExtensionHost,
implementing ipnext.Host.
- Improve docs for existing types and methods while adding docs for the new interfaces.
- Add test coverage for both the extracted and the new code.
- Remove ipn/desktop.SessionManager from tsd.System since ipn/desktop is now self-contained.
- Update existing extensions (e.g., ipn/auditlog and ipn/desktop) to use the new interfaces where appropriate.
We're not introducing new callback and hook types (e.g., for ipn.Prefs changes) just yet, nor are we enhancing current callbacks,
such as by improving conflict resolution when more than one extension tries to influence profile selection via a background profile resolver.
These further improvements will be submitted separately.
Updates #12614
Updates tailscale/corp#27645
Updates tailscale/corp#26435
Updates tailscale/corp#18342
Signed-off-by: Nick Khyl <nickk@tailscale.com>
