asyn-ares: bump required c-ares version to >= 1.16.0

[bagder]

No description provided.

[Copilot]

Pull request overview

This PR raises the minimum supported c-ares version for the async resolver backend to >= 1.16.0, allowing removal of legacy compatibility paths and simplifying the resolver implementation accordingly.

Changes:

• Enforce c-ares >= 1.16.0 in the c-ares resolver backend and remove the pre-1.16.0 code paths (including the non-ares_getaddrinfo() flow).
• Simplify c-ares feature gating by removing several version-dependent HAVE_CARES_* compile-time branches that are now always true under the new minimum.
• Update internal documentation to reflect the new minimum supported c-ares version.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
lib/asyn-ares.c	Enforces the new minimum c-ares version and removes legacy resolver code paths/feature gates tied to older c-ares versions.
docs/INTERNALS.md	Updates the documented minimum supported c-ares dependency version to 1.16.0.

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[testclutch]

Analysis of PR #20911 at eaefb959:

Test 799 failed, which has NOT been flaky recently, so there could be a real issue in this PR. Note that this test has failed in 12 different CI jobs (the link just goes to one of them). Note that this CI job has had a number of other flaky tests recently (7, to be exact) so it may be that this failure is rather a systemic issue with this job and not with this specific PR.

Generated by Testclutch

[bagder]

augment review

[augmentcode]

🤖 Augment PR Summary

Summary: This PR raises the minimum supported c-ares version for the async resolver backend to >= 1.16.0 and removes legacy compatibility paths.

Changes:

• Update INTERNALS dependency matrix to list c-ares 1.16.0 as the baseline.
• Enforce the new minimum in lib/asyn-ares.c and lib/asyn-base.c via compile-time checks.
• Remove pre-1.16 resolver fallback code and rely on ares_getaddrinfo()-based resolution.
• Simplify c-ares option handling (e.g., always using ares_set_servers_ports_csv() and local bind APIs under the new minimum).
• Update Autotools detection to require ares_getaddrinfo and adjust the “linux-old” CI workflow to disable c-ares until a new enough package is available.

Technical notes: Builds using USE_HTTPSRR already require an even newer c-ares (1.28.0+), and this PR keeps that enforcement.

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[augmentcode]

Review completed. 2 suggestions posted.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

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