19061 FIX DNS cache: Prevent superfluous queries

While updating the DNS cache, Checkmk performed DNS queries also for hosts with statically configured IP addresses.
This was caused by an erroneous swap of dictionaries containing the configured IPv4 and IPv6 addresses in the call stack.

This werk removes the swap such that no DNS query is executed for  hosts with a configured IP address.

To benefit from this fix, no manual interaction is required.

SUP-26752

Change-Id: Ieb0a9d3a83165d91dda5545d8349daa7ccb23963

Author: crazyscientist

.werks/19061.md

@@ -0,0 +1,20 @@
+[//]: # (werk v2)
+# DNS cache: Prevent superfluous queries
+
+key        | value
+---------- | ---
+date       | 2026-01-02T12:13:07+00:00
+version    | 2.3.0p42
+class      | fix
+edition    | cre
+component  | core
+level      | 2
+compatible | yes
+
+While updating the DNS cache, Checkmk performed DNS queries also for hosts with statically configured IP addresses.
+This was caused by an erroneous swap of dictionaries containing the configured IPv4 and IPv6 addresses in the call stack.
+
+This werk removes the swap such that no DNS query is executed for  hosts with a configured IP address.
+
+To benefit from this fix, no manual interaction is required.
+

cmk/base/modes/check_mk.py

@@ -785,8 +785,8 @@ def mode_update_dns_cache() -> None:
             for hn in set(hosts_config.hosts).union(hosts_config.clusters)
             if config_cache.is_active(hn) and config_cache.is_online(hn)
         ),
-        configured_ipv6_addresses=config.ipaddresses,
-        configured_ipv4_addresses=config.ipv6addresses,
+        configured_ipv6_addresses=config.ipv6addresses,
+        configured_ipv4_addresses=config.ipaddresses,
         simulation_mode=config.simulation_mode,
         override_dns=HostAddress(config.fake_dns) if config.fake_dns is not None else None,
     )