[Bug 1766106] [NEW] ntp.ubuntu.com not reliable, but used in standard configuration

[Sebastian Stark]

Public bug reported:

In systemd-timesyncd ntp.ubuntu.com is used as fall back ntp server.
However, one of the addresses it resolves to is not available for quite
some while:

[...]
Apr 14 07:37:42 singold systemd-timesyncd[773]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
Apr 14 08:10:45 singold systemd-timesyncd[773]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
Apr 15 08:20:48 singold systemd-timesyncd[802]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
Apr 15 12:47:56 singold systemd-timesyncd[842]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
Apr 16 07:39:05 singold systemd-timesyncd[842]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
Apr 18 18:11:05 singold systemd-timesyncd[842]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
Apr 19 23:45:04 singold systemd-timesyncd[758]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
Apr 20 14:20:46 singold systemd-timesyncd[758]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
Apr 21 09:42:45 singold systemd-timesyncd[758]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
Apr 22 09:41:52 singold systemd-timesyncd[672]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
Apr 22 09:47:03 singold systemd-timesyncd[672]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
[...]

It turns out that from all the A and AAAA records ntp.ubuntu.com
resolves the, 2001:67c:1560:8003::c8 seems to be constantly down.

This leads to time synchronisation problems for people using IPv6, as it
seems timesyncd keeps returning to the same server over and over again,
instead of trying the other ones DNS returns.

A practical solution to this would be to simply remove
2001:67c:1560:8003::c8 from the DNS entry for ntp.ubuntu.com.

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1766106

Title:
  ntp.ubuntu.com not reliable, but used in standard configuration

Status in systemd package in Ubuntu:
  New

Bug description:
  In systemd-timesyncd ntp.ubuntu.com is used as fall back ntp server.
  However, one of the addresses it resolves to is not available for
  quite some while:

  [...]
  Apr 14 07:37:42 singold systemd-timesyncd[773]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
  Apr 14 08:10:45 singold systemd-timesyncd[773]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
  Apr 15 08:20:48 singold systemd-timesyncd[802]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
  Apr 15 12:47:56 singold systemd-timesyncd[842]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
  Apr 16 07:39:05 singold systemd-timesyncd[842]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
  Apr 18 18:11:05 singold systemd-timesyncd[842]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
  Apr 19 23:45:04 singold systemd-timesyncd[758]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
  Apr 20 14:20:46 singold systemd-timesyncd[758]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
  Apr 21 09:42:45 singold systemd-timesyncd[758]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
  Apr 22 09:41:52 singold systemd-timesyncd[672]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
  Apr 22 09:47:03 singold systemd-timesyncd[672]: Timed out waiting for reply from [2001:67c:1560:8003::c8]:123 (ntp.ubuntu.com).
  [...]

  It turns out that from all the A and AAAA records ntp.ubuntu.com
  resolves the, 2001:67c:1560:8003::c8 seems to be constantly down.

  This leads to time synchronisation problems for people using IPv6, as
  it seems timesyncd keeps returning to the same server over and over
  again, instead of trying the other ones DNS returns.

  A practical solution to this would be to simply remove
  2001:67c:1560:8003::c8 from the DNS entry for ntp.ubuntu.com.

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