This change improves compatibility with newer UniFi OS versions while
maintaining backward compatibility with UniFi OS 4.2 and earlier.
The refactoring also reduces code duplication and improves maintainability
by centralizing dnsmasq configuration path logic.
On some routers, dnsmasq config may change cache-size dynamically after
ctrld starts, causing dnsmasq crashes.
Fixing this by using max-cache-ttl, which have the same effect with
setting cache-size=0 but won't conflict with existing routers config.
The dnsmasq cache-size setting on EdgeOS could be re-generated anytime
by vyatta router/dhcp components. This conflicts with setting generated
by ctrld, causing dnsmasq fails to start.
It's better to keep dnsmasq cache enabled on EdgeOS, we can turn it off
again once we find a reliable way to control cache-size setting.
The only reason that forces ctrld to depend on vyatta-dhcpd service on
EdgeOS is allowing ctrld to watch lease files properly, because those
files may not be created at the time client info table initialized.
However, on some EdgeOS version, vyatta-dhcpd could not start with an
empty config file, causing restart loop itself, flooding systemd log,
making the router run out of memory.
To fix this, instead of depending on vyatta-dhcpd, we should just watch
for lease files creation, then adding them to watch list.
While at it, also making ctrld starts after nss-lookup, ensuring we have
a working DNS before starting ctrld.
Config fetching/generating in cd mode is currently weird, error prone,
and easy for user to break ctrld when using custom config.
This commit reworks the flow:
- Fetching config from Control D API.
- No custom config, use the current default config.
- If custom config presents, but there's no listener, use 0.0.0.0:53.
- Try listening on current ip+port config, if ok, ctrld could be a
direct listener with current setup, moving on.
- If failed, trying 127.0.0.1:53.
- If failed, trying current ip + port 5354
- If still failed, pick a random ip:port pair, retry until listening ok.
With this flow, thing is more predictable/stable, and help removing the
Config interface for router.
