3 files changed, 30 insertions, 23 deletions

diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c
index 57a2c7d6c1..336269ca8a 100644
--- a/src/resolve/resolved-dns-scope.c
+++ b/src/resolve/resolved-dns-scope.c
@@ -78,8 +78,7 @@ DnsScope* dns_scope_free(DnsScope *s) {
 
         dns_scope_llmnr_membership(s, false);
 
-        while ((t = s->transactions)) {
-
+        while ((t = hashmap_steal_first(s->transactions))) {
                 /* Abort the transaction, but make sure it is not
                  * freed while we still look at it */
 
@@ -90,6 +89,8 @@ DnsScope* dns_scope_free(DnsScope *s) {
                 dns_transaction_free(t);
         }
 
+        hashmap_free(s->transactions);
+
         while ((rr = ordered_hashmap_steal_first(s->conflict_queue)))
                 dns_resource_record_unref(rr);
 
@@ -623,24 +624,20 @@ DnsTransaction *dns_scope_find_transaction(DnsScope *scope, DnsResourceKey *key,
         assert(scope);
         assert(key);
 
-        /* Try to find an ongoing transaction that is a equal or a
-         * superset of the specified question */
-
-        LIST_FOREACH(transactions_by_scope, t, scope->transactions) {
-
-                /* Refuse reusing transactions that completed based on
-                 * cached data instead of a real packet, if that's
-                 * requested. */
-                if (!cache_ok &&
-                    IN_SET(t->state, DNS_TRANSACTION_SUCCESS, DNS_TRANSACTION_FAILURE) &&
-                    !t->received)
-                        continue;
+        /* Try to find an ongoing transaction that is a equal to the
+         * specified question */
+        t = hashmap_get(scope->transactions, key);
+        if (!t)
+                return NULL;
 
-                if (dns_resource_key_equal(t->key, key) > 0)
-                        return t;
-        }
+        /* Refuse reusing transactions that completed based on cached
+         * data instead of a real packet, if that's requested. */
+        if (!cache_ok &&
+            IN_SET(t->state, DNS_TRANSACTION_SUCCESS, DNS_TRANSACTION_FAILURE) &&
+            !t->received)
+                return NULL;
 
-        return NULL;
+        return t;
 }
 
 static int dns_scope_make_conflict_packet(
diff --git a/src/resolve/resolved-dns-scope.h b/src/resolve/resolved-dns-scope.h
index 47f285db47..88fb8224e2 100644
--- a/src/resolve/resolved-dns-scope.h
+++ b/src/resolve/resolved-dns-scope.h
@@ -60,7 +60,7 @@ struct DnsScope {
         usec_t resend_timeout;
         usec_t max_rtt;
 
-        LIST_HEAD(DnsTransaction, transactions);
+        Hashmap *transactions;
 
         LIST_FIELDS(DnsScope, scopes);
 };
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 81156dfa45..608decd3ac 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -35,7 +35,6 @@ DnsTransaction* dns_transaction_free(DnsTransaction *t) {
 
         sd_event_source_unref(t->timeout_event_source);
 
-        dns_resource_key_unref(t->key);
         dns_packet_unref(t->sent);
         dns_packet_unref(t->received);
         dns_answer_unref(t->cached);
@@ -47,12 +46,14 @@ DnsTransaction* dns_transaction_free(DnsTransaction *t) {
         dns_stream_free(t->stream);
 
         if (t->scope) {
-                LIST_REMOVE(transactions_by_scope, t->scope->transactions, t);
+                hashmap_remove(t->scope->transactions, t->key);
 
                 if (t->id != 0)
                         hashmap_remove(t->scope->manager->dns_transactions, UINT_TO_PTR(t->id));
         }
 
+        dns_resource_key_unref(t->key);
+
         while ((q = set_steal_first(t->queries)))
                 set_remove(q->transactions, t);
         set_free(t->queries);
@@ -89,14 +90,18 @@ int dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsResourceKey *key)
         if (r < 0)
                 return r;
 
+        r = hashmap_ensure_allocated(&s->transactions, &dns_resource_key_hash_ops);
+        if (r < 0)
+                return r;
+
         t = new0(DnsTransaction, 1);
         if (!t)
                 return -ENOMEM;
 
         t->dns_fd = -1;
-
         t->key = dns_resource_key_ref(key);
 
+        /* Find a fresh, unused transaction id */
         do
                 random_bytes(&t->id, sizeof(t->id));
         while (t->id == 0 ||
@@ -108,7 +113,12 @@ int dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsResourceKey *key)
                 return r;
         }
 
-        LIST_PREPEND(transactions_by_scope, s->transactions, t);
+        r = hashmap_put(s->transactions, t->key, t);
+        if (r < 0) {
+                hashmap_remove(s->manager->dns_transactions, UINT_TO_PTR(t->id));
+                return r;
+        }
+
         t->scope = s;
 
         if (ret)