After more investigation, it seems like the 2 extra port-bindings port assignation decision is made by "libdns" itself.
https://github.com/wklaebe/bind9/blob/ac1dcdd124a5abdec4969e2c33836d863bf73aa7/lib/dns/dispatch.c#L1921
After more investigation, it seems like the 2 extra port-bindings port assignation decision is made by "libdns" itself.
https:/ /github. com/wklaebe/ bind9/blob/ ac1dcdd124a5abd ec4969e2c33836d 863bf73aa7/ lib/dns/ dispatch. c#L1921