+ 5. Logging control for DKIM verification. The existing DKIM log line is
+ controlled by a "dkim_verbose" selector which is _not_ enabled by default.
+ A new tag "DKIM=<domain>" is added to <= lines by default, controlled by
+ a "dkim" log_selector.
+
+ 6. Receive duration on <= lines, under a new log_selector "receive_time".
+
+ 7. Options "ipv4_only" and "ipv4_prefer" on the dnslookup router and on
+ routing rules in the manualroute router.
+