Problems with interfaces going down

[bindusers at prograde.net]

Greetings,

I’ve been fighting a two-fold problem with named (bind 9.16.11) running on macOS.

1: If an ethernet interface being listened to drops link, named immediately stops listening to it:

12-Feb-2021 17:33:19.326 no longer listening on 192.168.88.220#53

and

2: when link returns I get 2 tries to reestablish listening:

12-Feb-2021 17:33:39.458 listening on IPv4 interface en1, 192.168.88.220#53
12-Feb-2021 17:33:39.463 creating IPv4 interface en1 failed; interface ignored
12-Feb-2021 17:33:41.946 listening on IPv4 interface en1, 192.168.88.220#53
12-Feb-2021 17:33:41.951 creating IPv4 interface en1 failed; interface ignored

which both fail because named is no longer running as root.

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Where I’m confused is that this ISC KB article:

https://kb.isc.org/docs/aa-00420

seems to imply that the "no longer listening" event is due to a periodic interface scan finding the interface "unavailable".

That doesn’t fit my observations since it happens as soon as link is lost. If some minutes-long periodic scan were needed to detect the interface being down it would take, on average, half of that period to happen. It does not.

Further, I tried what the KB article advised by adding the option:

	interface-interval 0;

That does seem to stop the periodic scan (since my log is no longer filled with errors) but the “no longer listening” event still occurs right when the interface drops.

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Is it not possible to have named drop to a non-root user (via -u) but still recover from (or ride through) a momentary ethernet link loss?

Having the server stop working due to a switch I have no control over burping is very suboptimal.

Thanks for any ideas.

-Mike