+static int dns_query_add_transaction(DnsQuery *q, DnsScope *s, DnsResourceKey *key) {
+ _cleanup_(dns_question_unrefp) DnsQuestion *question = NULL;
+ DnsQueryTransaction *t;
+ int r;
+
+ assert(q);
+
+ r = set_ensure_allocated(&q->transactions, NULL, NULL);
+ if (r < 0)
+ return r;
+
+ if (key) {
+ question = dns_question_new(1);
+ if (!question)
+ return -ENOMEM;
+
+ r = dns_question_add(question, key);
+ if (r < 0)
+ return r;
+ } else
+ question = dns_question_ref(q->question);
+
+ LIST_FOREACH(transactions_by_scope, t, s->transactions)
+ if (dns_question_is_superset(t->question, question))
+ break;
+
+ if (!t) {
+ r = dns_query_transaction_new(&t, s, question);
+ if (r < 0)
+ return r;
+ }
+
+ r = set_ensure_allocated(&t->queries, NULL, NULL);
+ if (r < 0)
+ goto fail;
+
+ r = set_put(t->queries, q);
+ if (r < 0)
+ goto fail;
+
+ r = set_put(q->transactions, t);
+ if (r < 0) {
+ set_remove(t->queries, q);
+ goto fail;
+ }
+
+ return 0;
+
+fail:
+ dns_query_transaction_gc(t);
+ return r;
+}
+
+static int dns_query_add_transaction_split(DnsQuery *q, DnsScope *s) {
+ int r;
+
+ assert(q);
+ assert(s);
+
+ if (s->protocol == DNS_PROTOCOL_MDNS) {
+ r = dns_query_add_transaction(q, s, NULL);
+ if (r < 0)
+ return r;
+ } else {
+ unsigned i;
+
+ /* On DNS and LLMNR we can only send a single
+ * question per datagram, hence issue multiple
+ * transactions. */
+
+ for (i = 0; i < q->question->n_keys; i++) {
+ r = dns_query_add_transaction(q, s, q->question->keys[i]);
+ if (r < 0)
+ return r;
+ }
+ }
+
+ return 0;
+}
+