feat(iroh-dns): Improve error messages

[Frando]

Description

This improves the error message we show when calling endpoint.connect(endpoint_id, alpn) without internet connectivity, or with DNS blocked or similar.

Before:

No addressing information available: All address lookup services failed or produced no results
    Service 'dns' failed: no calls succeeded: [Failed to resolve TXT recordFailed to resolve TXT recordFailed to resolve TXT recordFailed to resolve TXT recordFailed to resolve TXT
 recordFailed to resolve TXT recordFailed to resolve TXT record]

After:

Failed to resolve remote address: All address lookup services failed or produced no results
    Service 'dns' failed: Failed to retrieve TXT record for _iroh.38g86cenj4anit756ah78o5ea84nmfgsyhmn64ibxosgyc9jku8y.staging-dns.iroh.link.: no connections available

Breaking Changes

None.

Notes & open questions

The no connections available at the end of the message is, unfortunately, all we get from hickory-resolver. This can be improved once we land #4036

Change checklist

• Self-review.
• Documentation updates following the style guide, if relevant.
• Tests if relevant.
• All breaking changes documented.
• This PR was created by a human that thought critically about the
  proposed change and wrote an as clear and concise description as
  they could.
• This PR isn't slop, and is carefully crafted to do have the
  intented effect.

[github-actions]

Documentation for this PR has been generated and is available at: https://n0-computer.github.io/iroh/pr/4410/docs/iroh/

Last updated: 2026-07-15T11:02:52Z

[github-actions]

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Last updated for commit: 4622dc4

[flub]

AnyError has a downcast_ref method. Can this not be done without breaking the API by trying to downcast it, if it works you get something that carries the host and kind, if not you have to fallback to the current version.

[flub]

Please use the checklist as well :)