dnsc: Fallback to getaddrinfo without any DNS servers (baresip#1195)

Co-authored-by: Wei Li Jiang <[email protected]>

include/re_dns.h

@@ -224,6 +224,7 @@ void dnsc_cache_flush(struct dnsc *dnsc);
 void dnsc_cache_max(struct dnsc *dnsc, uint32_t max);
 void dnsc_getaddrinfo(struct dnsc *dnsc, bool active);
 bool dnsc_getaddrinfo_enabled(struct dnsc *dnsc);
+bool dnsc_getaddrinfo_only(const struct dnsc *dnsc);
 
 
 /* DNS System functions */

src/dns/client.c

@@ -974,8 +974,16 @@ static int query(struct dns_query **qp, struct dnsc *dnsc, uint8_t opcode,
 	struct dns_query *q = NULL;
 	struct dnshdr hdr;
 	int err = 0;
+	bool use_getaddrinfo = false;
+	bool srv_available = srvv && srvc && *srvc != 0;
 
-	if (!dnsc || !name || !srvv || !srvc || !(*srvc))
+	if (!dnsc || !name)
+		return EINVAL;
+
+	use_getaddrinfo = dnsc->conf.getaddrinfo &&
+		(type == DNS_TYPE_A || type == DNS_TYPE_AAAA);
+
+	if (!srv_available && !use_getaddrinfo)
 		return EINVAL;
 
 	if (DNS_QTYPE_AXFR == type)
@@ -1029,8 +1037,7 @@ static int query(struct dns_query **qp, struct dnsc *dnsc, uint8_t opcode,
 		list_init(q->rrlv[i]);
 	}
 
-	if (dnsc->conf.getaddrinfo &&
-	    (q->type == DNS_TYPE_A || q->type == DNS_TYPE_AAAA)) {
+	if (use_getaddrinfo) {
 		err = query_getaddrinfo(q);
 		if (err)
 			goto error;
@@ -1401,3 +1408,20 @@ bool dnsc_getaddrinfo_enabled(struct dnsc *dnsc)
 
 	return dnsc->conf.getaddrinfo;
 }
+
+
+/**
+ * Return if getaddrinfo usage is enabled and exclusive,
+ * i.e. there are no DNS servers known explicitly
+ *
+ * @param dnsc  DNS Client
+ *
+ * @return true if DNS servers are available, false otherwise
+ */
+bool dnsc_getaddrinfo_only(const struct dnsc *dnsc)
+{
+	if (!dnsc)
+		return false;
+
+	return dnsc->conf.getaddrinfo && dnsc->srvc == 0;
+}

src/sip/request.c

@@ -727,6 +727,8 @@ static int sip_request_send(struct sip_request *req, struct sip *sip,
 {
 	struct sa dst;
 	int err;
+	bool addr_only = req->tp_selected &&
+		dnsc_getaddrinfo_only(req->sip->dnsc);
 
 	if (!sa_set_str(&dst, req->host,
 			sip_transp_port(req->tp, route->port))) {
@@ -737,7 +739,7 @@ static int sip_request_send(struct sip_request *req, struct sip *sip,
 			return err;
 		}
 	}
-	else if (route->port) {
+	else if (route->port || addr_only){
 
 		req->port = sip_transp_port(req->tp, route->port);
 		err = addr_lookup(req, req->host);