NTP server doesn't properly handle IPv6 interface being disabled

[coder0107git]

Versions

• Pi-hole: v6.0.5
• AdminLTE: v6.0.2
• FTL: v6.0.4

Platform

• OS and version: Raspbian 11 (bullseye)

• Platform: Raspberry Pi 3b+

Expected behavior

The NTP server to not attempt to access an IPv6 time server when IPv6 has been disabled.

Actual behavior / bug

My Pi has IPv6 disabled. Since I've updated to PiHole v6 with it's new integrated NTP client, I've started getting the following error.

Error in NTP server: Cannot create NTP socket (Address family not supported by protocol), IPv6 NTP server not available

Steps to reproduce

Steps to reproduce the behavior:

1. Disable IPv6 (I appended ipv6.disable=1 to the only line in the /boot/cmdline.txt file).
2. Reboot to apply.
3. Wait for it to attempt to synchronize the time.
4. See error.

Debug Token

• URL: https://tricorder.pi-hole.net/ouXgXFeV/

Screenshots

Additional context

None

[mwoolweaver]

go to https://pi.hole/admin/settings/all

and disable the NTP ipv6 option as seen in the screenshot below

[DL6ER]

I agree that @mwoolweaver's suggestion is the right thing to do here. Pi-hole handles IPv6 being disabled gracefully in still working, just warning you that the (by default on) IPv6 component could not be started. The error will go away once you disable it. I do think this is how we should behave, otherwise, users may not get what they expect if there is no warning (could be that IPv6 is disabled on a particular machine and they are not aware of it). I will, hence, close this. Feel free to re-open in case you think this needs further discussion.

[coder0107git]

Thanks! I don't know how I missed that.

I think the current message is fine as is but it would be nicer if it failed early with something like "the IPv6 interface is unavailable". When it fails late like this, it feels like something unexpectedly broke instead of an expected/accounted-for failure that can easily be remedied.

[DL6ER]

We are not explicitly checking for IPv6 availability as this would be quite some work due to the various ways IPv6 can be disabled (during boot, during runtime, manually stripping all IPv6 addresses from all interfaces ...). Hence, we simply try to create the docket and the error message in the parenthesis is what the system tells us. This message has not been invented by us and cannot be changed (unless we add an extra case to exactly catch and replace this text - unfeasible as the error message may be in a different language if the system is).

[coder0107git]

Hm, okay. That makes sense. At first I thought that it might be possible to match on errno, but then I couldn't tell if that's platform specific.

FTL/src/ntp/server.c

Lines 295 to 297 in b7eb53b

	snprintf(errbuf, sizeof(errbuf),
	"Cannot create NTP socket (%s), IPv%i NTP server not available",
	strerror(errno), protocol == AF_INET ? 4 : 6);