feat: prune old, inactive paths

[ramfox]

Description

Whenever we insert a new path, trigger pruning paths.

We currently only prune IP paths, and pruning paths only occurs if we have more than 30 IP paths.

We will prune any paths that did not successfully holepunch.

If there are still over 30 IP paths left, then we order the "inactive" paths (paths that have been closed, but at one point holepunched), and prune the paths that were closed earliest.

Notes and Questions

• Added constants:
  • MAX_IP_PATHS = 30 - maximum IP paths per endpoint
  • MAX_INACTIVE_IP_PATHS = 10 - maximum inactive IP paths to keep
• New PathState field:
  • status - tracks the PathStatus of the path
• New PathStatus enum:
  • PathStatus::Open - is an open path
  • PathStatus::Inactive(Instant) - was opened once, but currently inactive
  • PathStatus::Unusable - we attempted to use it, but it never connected
  • PathStatus::Unknown - we don't know the status yet
• New methods on RemotePathState:
  • abandoned_path - marks a path as abandoned with timestamp, triggered when we get the PathEvent::Abandoned event
  • prune_paths - triggers path pruning, occurs whenever we insert a path to the RemotePathState
  • changed insert to insert_open_path
• New prune_ip_paths function with sophisticated logic:
  • Only prunes if IP paths exceed MAX_IP_PATHS
  • Never prunes active paths or paths of unknown status
  • Always prunes failed holepunch attempts (PathStatus::Unusable)
  • Keeps 10 most recently inactive paths that were previously
    successful
  • Special case: if all paths failed, keeps MAX_IP_PATHS instead of pruning everything
• Added tests for edge cases and the typical case

[github-actions]

Documentation for this PR has been generated and is available at: https://n0-computer.github.io/iroh/pr/3666/docs/iroh/

Last updated: 2025-12-02T17:16:02Z

[github-actions]

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Last updated for commit: 2492e77

[ramfox]

@flub can I merge into feat-multipath-quic-nat? Looks like the same tests are failing.

[matheus23]

With the previous comments addressed, this is good to go from my side.
Sorry that I effectively blocked this so long that we ended up with a bigger merge conflict :S

[flub]

Logic to prune seems ok. Though haven't really reviewed since the diff seems off, probably because the target branch has moved under your feet...

[ramfox]

@flub this is reviewable now w/ rebases

same tests failing here that fail on feat-multipath