pfSense

Tested on 22.05.a.20220417.0600.

Tested with the feature from:
https://redmine.pfsense.org/issues/13057

The interval is added correctly:

root 62793 0.0 0.3 12140 2784 - Is 18:44 0:00.01 |-- /usr/local/sbin/filterdns -p /var/run/filterdns-ipsec.pid -i 10 -c /var/etc/ipsec/filterdns-ipsec.hosts -d 1

However, the actual resolve interval seems to be done at twice the value in the config (tested with 10 and 15 second intervals - reboot after each change):

DNS Resolver logs with verbosity 3:

Apr 17 18:47:14     unbound     62371     [62371:0] debug: iterator[module 0] operate: extstate:module_state_initial event:module_event_new
Apr 17 18:47:14     unbound     62371     [62371:0] info: resolving siteb.dyndns.lab.arpa. A IN
Apr 17 18:47:14     unbound     62371     [62371:0] info: processQueryTargets: siteb.dyndns.lab.arpa. A IN
Apr 17 18:47:14     unbound     62371     [62371:0] info: sending query: siteb.dyndns.lab.arpa. A IN
Apr 17 18:47:14     unbound     62371     [62371:0] debug: sending to target: <lab.arpa.> 10.0.5.200#53
Apr 17 18:47:14     unbound     62371     [62371:0] debug: cache memory msg=66072 rrset=66072 infra=7808 val=0
Apr 17 18:47:14     unbound     62371     [62371:0] debug: iterator[module 0] operate: extstate:module_wait_reply event:module_event_reply
Apr 17 18:47:14     unbound     62371     [62371:0] info: iterator operate: query siteb.dyndns.lab.arpa. A IN
Apr 17 18:47:14     unbound     62371     [62371:0] info: response for siteb.dyndns.lab.arpa. A IN
Apr 17 18:47:14     unbound     62371     [62371:0] info: reply from <lab.arpa.> 10.0.5.200#53
Apr 17 18:47:14     unbound     62371     [62371:0] info: query response was ANSWER
Apr 17 18:47:14     unbound     62371     [62371:0] info: finishing processing for siteb.dyndns.lab.arpa. A IN
Apr 17 18:47:14     unbound     62371     [62371:0] debug: cache memory msg=66287 rrset=66277 infra=8066 val=0
Apr 17 18:47:14     unbound     62371     [62371:0] debug: iterator[module 0] operate: extstate:module_state_initial event:module_event_new
Apr 17 18:47:14     unbound     62371     [62371:0] info: resolving siteb.dyndns.lab.arpa. AAAA IN
Apr 17 18:47:14     unbound     62371     [62371:0] info: processQueryTargets: siteb.dyndns.lab.arpa. AAAA IN
Apr 17 18:47:14     unbound     62371     [62371:0] info: sending query: siteb.dyndns.lab.arpa. AAAA IN
Apr 17 18:47:14     unbound     62371     [62371:0] debug: sending to target: <lab.arpa.> 10.0.5.200#53
Apr 17 18:47:14     unbound     62371     [62371:0] debug: cache memory msg=66287 rrset=66277 infra=8066 val=0
Apr 17 18:47:14     unbound     62371     [62371:0] debug: iterator[module 0] operate: extstate:module_wait_reply event:module_event_reply
Apr 17 18:47:14     unbound     62371     [62371:0] info: iterator operate: query siteb.dyndns.lab.arpa. AAAA IN
Apr 17 18:47:14     unbound     62371     [62371:0] info: response for siteb.dyndns.lab.arpa. AAAA IN
Apr 17 18:47:14     unbound     62371     [62371:0] info: reply from <lab.arpa.> 10.0.5.200#53
Apr 17 18:47:14     unbound     62371     [62371:0] info: query response was nodata ANSWER
Apr 17 18:47:14     unbound     62371     [62371:0] info: finishing processing for siteb.dyndns.lab.arpa. AAAA IN
Apr 17 18:47:14     unbound     62371     [62371:0] debug: cache memory msg=66502 rrset=66526 infra=8066 val=0
Apr 17 18:47:44     unbound     62371     [62371:0] debug: iterator[module 0] operate: extstate:module_state_initial event:module_event_new
Apr 17 18:47:44     unbound     62371     [62371:0] info: resolving siteb.dyndns.lab.arpa. A IN
Apr 17 18:47:44     unbound     62371     [62371:0] info: processQueryTargets: siteb.dyndns.lab.arpa. A IN
Apr 17 18:47:44     unbound     62371     [62371:0] info: sending query: siteb.dyndns.lab.arpa. A IN
Apr 17 18:47:44     unbound     62371     [62371:0] debug: sending to target: <lab.arpa.> 10.0.5.200#53
Apr 17 18:47:44     unbound     62371     [62371:0] debug: iterator[module 0] operate: extstate:module_wait_reply event:module_event_reply
Apr 17 18:47:44     unbound     62371     [62371:0] info: iterator operate: query siteb.dyndns.lab.arpa. A IN
Apr 17 18:47:44     unbound     62371     [62371:0] info: response for siteb.dyndns.lab.arpa. A IN
Apr 17 18:47:44     unbound     62371     [62371:0] info: reply from <lab.arpa.> 10.0.5.200#53
Apr 17 18:47:44     unbound     62371     [62371:0] info: query response was ANSWER
Apr 17 18:47:44     unbound     62371     [62371:0] info: finishing processing for siteb.dyndns.lab.arpa. A IN
Apr 17 18:47:44     unbound     62371     [62371:0] debug: cache memory msg=66502 rrset=66526 infra=8066 val=0
Apr 17 18:48:14     unbound     62371     [62371:0] debug: iterator[module 0] operate: extstate:module_state_initial event:module_event_new
Apr 17 18:48:14     unbound     62371     [62371:0] info: resolving siteb.dyndns.lab.arpa. A IN
Apr 17 18:48:14     unbound     62371     [62371:0] info: processQueryTargets: siteb.dyndns.lab.arpa. A IN
Apr 17 18:48:14     unbound     62371     [62371:0] info: sending query: siteb.dyndns.lab.arpa. A IN
Apr 17 18:48:14     unbound     62371     [62371:0] debug: sending to target: <lab.arpa.> 10.0.5.200#53
Apr 17 18:48:14     unbound     62371     [62371:0] debug: iterator[module 0] operate: extstate:module_wait_reply event:module_event_reply
Apr 17 18:48:14     unbound     62371     [62371:0] info: iterator operate: query siteb.dyndns.lab.arpa. A IN
Apr 17 18:48:14     unbound     62371     [62371:0] info: response for siteb.dyndns.lab.arpa. A IN
Apr 17 18:48:14     unbound     62371     [62371:0] info: reply from <lab.arpa.> 10.0.5.200#53
Apr 17 18:48:14     unbound     62371     [62371:0] info: query response was ANSWER
Apr 17 18:48:14     unbound     62371     [62371:0] info: finishing processing for siteb.dyndns.lab.arpa. A IN
Apr 17 18:48:14     unbound     62371     [62371:0] debug: cache memory msg=66502 rrset=66526 infra=8066 val=0 

DNS Resolver logs with filderdns verbosity 99:

Apr 17 19:06:43     filterdns     94859     Awaking from the sleep for hostname siteb.dyndns.lab.arpa (1)
Apr 17 19:06:43     filterdns     94859     found address 198.51.100.2 for host siteb.dyndns.lab.arpa
Apr 17 19:07:02     filterdns     94859     Awaking from the sleep for hostname siteb.dyndns.lab.arpa (1)
Apr 17 19:07:02     filterdns     94859     found address 198.51.100.2 for host siteb.dyndns.lab.arpa
Apr 17 19:07:22     filterdns     94859     Awaking from the sleep for hostname siteb.dyndns.lab.arpa (1)
Apr 17 19:07:22     filterdns     94859     found address 198.51.100.2 for host siteb.dyndns.lab.arpa
Apr 17 19:07:42     filterdns     94859     Awaking from the sleep for hostname siteb.dyndns.lab.arpa (1)
Apr 17 19:07:42     filterdns     94859     found address 198.51.100.2 for host siteb.dyndns.lab.arpa
Apr 17 19:08:02     filterdns     94859     Awaking from the sleep for hostname siteb.dyndns.lab.arpa (1)
Apr 17 19:08:02     filterdns     94859     found address 198.51.100.2 for host siteb.dyndns.lab.arpa
Apr 17 19:08:22     filterdns     94859     Awaking from the sleep for hostname siteb.dyndns.lab.arpa (1)
Apr 17 19:08:22     filterdns     94859     found address 198.51.100.2 for host siteb.dyndns.lab.arpa
Apr 17 19:08:42     filterdns     94859     Awaking from the sleep for hostname siteb.dyndns.lab.arpa (1)
Apr 17 19:08:42     filterdns     94859     found address 198.51.100.2 for host siteb.dyndns.lab.arpa
Apr 17 19:09:02     filterdns     94859     Awaking from the sleep for hostname siteb.dyndns.lab.arpa (1)
Apr 17 19:09:02     filterdns     94859     found address 198.51.100.2 for host siteb.dyndns.lab.arpa
Apr 17 19:09:22     filterdns     94859     Awaking from the sleep for hostname siteb.dyndns.lab.arpa (1)
Apr 17 19:09:22     filterdns     94859     found address 198.51.100.2 for host siteb.dyndns.lab.arpa
Apr 17 19:09:42     filterdns     94859     Awaking from the sleep for hostname siteb.dyndns.lab.arpa (1)
Apr 17 19:09:42     filterdns     94859     found address 198.51.100.2 for host siteb.dyndns.lab.arpa
Apr 17 19:10:02     filterdns     94859     Awaking from the sleep for hostname siteb.dyndns.lab.arpa (1)
Apr 17 19:10:02     filterdns     94859     found address 198.51.100.2 for host siteb.dyndns.lab.arpa