20-firewall: Execute has_zone and and fw4 in background to avoid slow execution of hotplug.d/iface scripts

[rdevshp]

This pull request fixes openwrt/openwrt#20723

[brada4]

Something similar by @ptpt52 (pre-dating my impromptu re-invention) ? https://github.com/x-wrt/x-wrt/blob/master/package/network/config/firewall4/patches/200-fw4-hotplug-fork.patch

[brada4]

You have to limit forking of new copies of reload attempts , rapid flipping of link externally would unnecesarily accumulate waiting background tasks.

[rdevshp]

What do you think would be the ideal approach here to avoid excessive reload attempts & unnecessarily accumulate background tasks?
I am planning to create a new service that actually executes fw4 -q reload, and the 20-firewall script would merely send a fw4 reload notification to the new service without actually doing the reload itself. Do you think this is a good idea?

[brada4]

It is not about clicks in the interface that go in sync with 🤣 background 🤣 activity, it is about rapidly (I tried 10hz) flipping connected ethernet with zone like wan and building up said activities.
(but totally agree massive cpu time hogs should be out of hotplug)