DNS Resolver Domain Overrides stop working until restart of unbound

[bitrot]

I have DNS Resolver setup with a couple of domain overrides. Everything works fine, except the domain overrides will often randomly stop working and I have to restart unbound to resolve that. However, normal name resolution is completely unaffected.

I should maybe mention that both of the domain overrides I have set up target IP addresses on a remote network behind two different IPSEC site to site VPN tunnels. In order to traverse the IPSEC VPNs for the two domain overrides, unbound is configured to use the LAN interface as an outgoing network interface.

[bitrot]

Here's what I see in the system logs when domain override is not working. I've obfuscated the actual host name by replacing it with host.domain.local in the log below.

Jun 26 11:51:02	unbound	39647:1	debug: cache memory msg=2104630 rrset=3021363 infra=2591404 val=313689
Jun 26 11:51:02	unbound	39647:1	info: validation success host.domain.local. AAAA IN
Jun 26 11:51:02	unbound	39647:1	info: validate(nxdomain): sec_status_secure
Jun 26 11:51:02	unbound	39647:1	info: validator operate: query host.domain.local. AAAA IN
Jun 26 11:51:02	unbound	39647:1	debug: validator[module 0] operate: extstate:module_wait_module event:module_event_moddone
Jun 26 11:51:02	unbound	39647:1	info: finishing processing for host.domain.local. AAAA IN
Jun 26 11:51:02	unbound	39647:1	info: resolving host.domain.local. AAAA IN
Jun 26 11:51:02	unbound	39647:1	debug: iterator[module 1] operate: extstate:module_state_initial event:module_event_pass
Jun 26 11:51:02	unbound	39647:1	info: validator operate: query host.domain.local. AAAA IN
Jun 26 11:51:02	unbound	39647:1	debug: validator[module 0] operate: extstate:module_state_initial event:module_event_new
Jun 26 11:51:00	unbound	39647:0	debug: cache memory msg=2104630 rrset=3021363 infra=2591404 val=313689