refactor(multipath): move discovery into EndpointStateActor

[Frando]

Description

Fixes #3642

This moves discovery handling fully into the EndpointStateActor.
The pub(crate) interface to trigger discovery and get a EndpointMappedAddr is now Magicsock::resolve_remote, which sends the provided addresses to the EndpointStateActor. The actor starts discovery if it does not have a selected path and if discovery is not running. It returns either immediately if there are any known paths, or waits for discovery to produce at least one result or an error. Once this returns, resolve_remote returns either with a EndpointMappedAddr or with the discovery error.

This means the current behavior is kept: We only start quinn::Endpoint::connect once we have at least one transport address for the remote. If not, we return the discovery error immediately from iroh::Endpoint::connect.

This opens the door for us to easily tune when to run discovery in other siutations, e.g. when all available paths to a remote are closed. However, for now this PR still only starts discovery when Endpoint::connect is called and no path is selected at the moment.

Breaking Changes

Notes & open questions

Change checklist

• Self-review.
• Documentation updates following the style guide, if relevant.
• Tests if relevant.
• All breaking changes documented.
  • List all breaking changes in the above "Breaking Changes" section.
  • Open an issue or PR on any number0 repos that are affected by this breaking change. Give guidance on how the updates should be handled or do the actual updates themselves. The major ones are:
    • quic-rpc
    • iroh-gossip
    • iroh-blobs
    • dumbpipe
    • sendme

[github-actions]

Documentation for this PR has been generated and is available at: https://n0-computer.github.io/iroh/pr/3645/docs/iroh/

Last updated: 2025-11-12T11:44:04Z

[flub]

I guess most tests needs to be moved the the StaticProvider?

I don't quite follow the WantConnect stuff. Is this trying to make sure you can return an error straight from calling Endpoint::connect when you don't have any discovery results? As otherwise you'd start connecting and then the connection would time out?

[flub]

Yes please!

The EndpointStateActor should collect these addresses as usual but when choosing addresses to send to when handling SendDatagram it should filter out any that are itself. That would mean the possible remote addresses are not lost when you move network. The EndpointStateActor already has access to the local DirectAddrs so this is way more logical.

[Frando]

I don't quite follow the WantConnect stuff. Is this trying to make sure you can return an error straight from calling Endpoint::connect when you don't have any discovery results?

Yes, exactly. It mimics the current behavior that quinn::Endpoint::connect is only started once we have at least one dialable remote address, and if discovery errors or returns no results, we return straight from iroh::Endpoint::connect without touching quinn at all. The alternative would be that all connections time out if discovery yields nothing.

[github-actions]

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Last updated for commit: bdd7c68