resolved: add test for route-only domain filtering (#3609)

With commit 6f7da49d00 route-only domains do not get put into resolv.conf's
"search" list any more. Add a comment about the tri-state, to clarify its
semantics and why we are passing a bool parameter into an int type. Also add a
test case for it.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/resolve/resolved-manager.c b/src/resolve/resolved-manager.c
index add463b6a9..92ade820ac 100644
--- a/src/resolve/resolved-manager.c
+++ b/src/resolve/resolved-manager.c
@@ -1200,6 +1200,11 @@ int manager_compile_dns_servers(Manager *m, OrderedSet **dns) {
         return 0;
 }
 
+/* filter_route is a tri-state:
+ *   < 0: no filtering
+ *   = 0 or false: return only domains which should be used for searching
+ *   > 0 or true: return only domains which are for routing only
+ */
 int manager_compile_search_domains(Manager *m, OrderedSet **domains, int filter_route) {
         DnsSearchDomain *d;
         Iterator i;