Reliably detecting the absence of IPv6

[Oldřich Jedlička]

čt 11. 12. 2025 v 4:45 odesílatel Philip Prindeville via openwrt-devel
<openwrt-devel at lists.openwrt.org> napsal:
> I previously tested with -z “$(ip -6 -o route show default)” but as someone pointed out, if at the time that Bind starts up, someone later brings up an IPv6 default route (say via DHCP or a tunnel), then this caused a denial of service.

If you have issues with network connectivity changes during startup,
there is a way for the service to react. This is how I tried to solve
similar startup issue (network not up or changed) for fwknopd:

https://github.com/openwrt/packages/blob/master/net/fwknop/files/fwknopd.init#L16-L45

The procd options for service startup are described here, although I
had to check the source code to really verify what is expected as input
(network name or linux interface name):

https://openwrt.org/docs/guide-developer/procd-init-scripts

So when you correctly define your network dependencies, you should get
restarted by procd automatically.

Cheers,
Oldrich.