Tweak NTP error reporting

[DL6ER]

What does this implement/fix?

This PR has three changes regarding the NTP implementation:

1. If there was a timeout, we log the used IP address in addition to the host name. This may be useful to determine if only specific servers cause timeouts (as suggested by @deHakkelaar)

2. Do not issue double warnings when receiving NTP replies fails, e.g. skip the first of these two:

   2024-11-28 05:28:35.590 CET [25437/T25447] WARNING: Could not recv() in reply() (/app/src/ntp/client.c:223): Resource temporarily unavailable
   2024-11-28 05:28:35.590 CET [25437/T25447] ERROR: Failed to receive data from NTP server europe.pool.ntp.org: Timeout
   

3. In case the upstream server sends a "kiss code", we interpret and show it (e.g. "access denied" when authentication is required or "rate exceeded" when querying too often). Before, we simply logged

   Received NTP reply has invalid version, ignoring
   

   in such a case.

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Related issue or feature (if applicable): N/A

Pull request in docs with documentation (if applicable): N/A

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By submitting this pull request, I confirm the following:

1. I have read and understood the contributors guide, as well as this entire template. I understand which branch to base my commits and Pull Requests against.
2. I have commented my proposed changes within the code.
3. I am willing to help maintain this change if there are issues with it later.
4. It is compatible with the EUPL 1.2 license
5. I have squashed any insignificant commits. (git rebase)

Checklist:

• The code change is tested and works locally.
• I based my code and PRs against the repositories developmental branch.
• I signed off all commits. Pi-hole enforces the DCO for all contributions
• I signed all my commits. Pi-hole requires signatures to verify authorship
• I have read the above and my PR is ready for review.

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/no-valid-ntp-replies-received-check-server-and-network-connectivity/74237/12

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/no-valid-ntp-replies-received-check-server-and-network-connectivity/74237/28

[sawsanders]

Working well for me. No issues in two days of testing!

EDIT: See below, spoke too soon.

[yubiuser]

There is an reported crash on with this branch
https://discourse.pi-hole.net/t/pi-hole-crashed-shortly-after-upgrade/74553

[DL6ER]

This crash happened somewhere in the DNS resolver thread, not code that is even remotely touched by this PR. So this may be 100% coincidence.

[DL6ER]

Nonetheless, I went through the resolver code line-by-line and added quite a few extra checks wherever possible. I don't think there was an issue but now everything should be even better because we are not believing in large enough buffers but actually check that before working on them.

[sawsanders]

This branch has been working very well for me. I haven't seen any issues since the last commits.