resolved: fully support DNS search domains

This adds support for searching single-label hostnames in a set of
configured search domains.

A new object DnsQueryCandidate is added that links queries to scopes.
It keeps track of the search domain last used for a query on a specific
link. Whenever a host name was unsuccessfuly resolved on a scope all its
transactions are flushed out and replaced by a new set, with the next
search domain appended.

This also adds a new flag SD_RESOLVED_NO_SEARCH to disable search domain
behaviour. The "systemd-resolve-host" tool is updated to make this
configurable via --search=.

Fixes #1697

1 files changed, 4 insertions, 4 deletions

diff --git a/src/resolve/resolved-dns-question.c b/src/resolve/resolved-dns-question.c
index b1aa0175e0..3249448d3b 100644
--- a/src/resolve/resolved-dns-question.c
+++ b/src/resolve/resolved-dns-question.c
@@ -89,7 +89,7 @@ int dns_question_add(DnsQuestion *q, DnsResourceKey *key) {
         return 0;
 }
 
-int dns_question_matches_rr(DnsQuestion *q, DnsResourceRecord *rr) {
+int dns_question_matches_rr(DnsQuestion *q, DnsResourceRecord *rr, const char *search_domain) {
         unsigned i;
         int r;
 
@@ -99,7 +99,7 @@ int dns_question_matches_rr(DnsQuestion *q, DnsResourceRecord *rr) {
                 return 0;
 
         for (i = 0; i < q->n_keys; i++) {
-                r = dns_resource_key_match_rr(q->keys[i], rr);
+                r = dns_resource_key_match_rr(q->keys[i], rr, search_domain);
                 if (r != 0)
                         return r;
         }
@@ -107,7 +107,7 @@ int dns_question_matches_rr(DnsQuestion *q, DnsResourceRecord *rr) {
         return 0;
 }
 
-int dns_question_matches_cname(DnsQuestion *q, DnsResourceRecord *rr) {
+int dns_question_matches_cname(DnsQuestion *q, DnsResourceRecord *rr, const char *search_domain) {
         unsigned i;
         int r;
 
@@ -117,7 +117,7 @@ int dns_question_matches_cname(DnsQuestion *q, DnsResourceRecord *rr) {
                 return 0;
 
         for (i = 0; i < q->n_keys; i++) {
-                r = dns_resource_key_match_cname(q->keys[i], rr);
+                r = dns_resource_key_match_cname(q->keys[i], rr, search_domain);
                 if (r != 0)
                         return r;
         }