Add warning to the multiple DNS advertisement

[wsw70]

Quick workaround for pi-hole/pi-hole#6360 for details.

Signed-off-by: wsw70 wsw70wsw70@gmail.com

What does this PR aim to accomplish?:

Update the UI Advertise DNS server multiple times description to account for pi-hole/pi-hole#6360

How does this PR accomplish the above?:

By adding to the description

(...) This is not compatible with adding dhcp-option=6,... in dnsmasq_lines in /etc/pihole/config.toml or /etc/dnsmasq.d/

---

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 and I have tested my changes.
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)
6. I have checked that another pull request for this purpose does not exist.
7. I have considered, and confirmed that this submission will be valuable to others.
8. I accept that this submission may not be used, and the pull request closed at the will of the maintainer.
9. I give this submission freely, and claim no ownership to its content.

---

• I have read the above and my PR is ready for review. Check this box to confirm

[rdwebdesign]

A few format suggestions:

Suggested change

<p class="help-block">Advertise DNS server multiple times to clients. Some devices will add their own proprietary DNS servers to the list of DNS servers, which can cause issues with Pi-hole. This option will advertise the Pi-hole DNS server multiple times to clients, which should prevent this from happening. This is not compatible with adding dhcp-option=6,... in dnsmasq_lines in /etc/pihole/config.toml or /etc/dnsmasq.d/</p>

<p class="help-block">Advertise DNS server multiple times to clients. Some devices will add their own proprietary DNS servers to the list of DNS servers, which can cause issues with Pi-hole. This option will advertise the Pi-hole DNS server multiple times to clients, which should prevent this from happening.<br>This is not compatible with adding <code>dhcp-option=6,...</code> in <code>dnsmasq_lines</code> in <em>/etc/pihole/config.toml</em> or <em>/etc/dnsmasq.d/</em></p>

[rrobgill]

Isn't this really kind of covered by the present warning ?

Warning: This is an advanced setting and should only be used with care. 
Incorrectly formatted or duplicated lines as well as lines conflicting with
the automatic configuration of Pi-hole can break the embedded dnsmasq
and will stop DNS resolution from working.

There are other options that can be changed in the UI (or directly editing pihole.toml) that are incompatible with adding the same option again in misc.dnsmasq_lines (or indeed by enabling misc.etc_dnsmasq_d and duplicating them in there).

A quick look at pihole.toml suggests port, cache-size, use-stale-cache, local-service, log-facility. And considering other options that are not enabled by default, probably most of the options under [dhcp].

If they all had additional warnings listed at the level of their option, the UI would get awfully cluttered. (As would all of the additional text in misc.dnsmasq_lines).

[yubiuser]

I agree with @rrobgill. We can't warn about each possible incompatible option with whatever users might set in dnsmasq_lines. If they are so advanced that they need to set specific dnsmasq options, they should be able to check the logs and figure out what is conflicting here.

[wsw70]

I understand that everything cannot be warned against. In that case however the warning in the ligs points to a problem nowhere to be find in the config file - one needs to check dnsmasq.conf (a generated file) to realize where the warning comes from.

Adding extra DNS servers is also something not that exotic (though less likely with Pi-hole).

I am fine with closing the PR since there are now 2:0 comments stating this is not a good idea.

[DL6ER]

Plus, ideally, you should not even be able to configure your Pi-hole in a way that breaks the dnsmasq at least not from the UI/API/CLI as there is a config test involved in the process.

Example: Trying to set port=1234 in misc.dnsmasq_lines causes

and the new settings are not actually getting saved.

Only when directly working with pihole.toml there is nothing that could be done.