dns_client: retry when upstream result is empty.

src/Makefile

@@ -50,9 +50,9 @@ override CXXFLAGS +=-Iinclude
 
 # ldflags
 ifeq ($(STATIC), yes)
- override LDFLAGS += -lssl -lcrypto -Wl,--whole-archive -lpthread -Wl,--no-whole-archive -ldl -static
+ override LDFLAGS += -lssl -lcrypto -Wl,--whole-archive -lpthread -Wl,--no-whole-archive -ldl -lm -static
 else
- override LDFLAGS += -lssl -lcrypto -lpthread -ldl
+ override LDFLAGS += -lssl -lcrypto -lpthread -ldl -lm
 endif
 
 .PHONY: all clean

src/dns_client.c

@@ -1674,6 +1674,26 @@ static int _dns_replied_check_add(struct dns_query_struct *dns_query, struct soc
 	return 0;
 }
 
+static void _dns_replied_check_remove(struct dns_query_struct *dns_query, struct sockaddr *addr, socklen_t addr_len)
+{
+	uint32_t key = 0;
+	struct dns_query_replied *replied_map = NULL;
+
+	if (addr_len > sizeof(struct sockaddr_in6)) {
+		return;
+	}
+
+	key = jhash(addr, addr_len, 0);
+	hash_for_each_possible(dns_query->replied_map, replied_map, node, key)
+	{
+		if (memcmp(&replied_map->addr, addr, addr_len) == 0) {
+			hash_del(&replied_map->node);
+			free(replied_map);
+			return;
+		}
+	}
+}
+
 static int _dns_client_recv(struct dns_server_info *server_info, unsigned char *inpacket, int inpacket_len,
 							struct sockaddr *from, socklen_t from_len)
 {
@@ -1761,13 +1781,17 @@ static int _dns_client_recv(struct dns_server_info *server_info, unsigned char *
 	if (query->callback) {
 		ret = query->callback(query->domain, DNS_QUERY_RESULT, server_info, packet, inpacket, inpacket_len,
 							  query->user_ptr);
-		if (request_num == 0 || ret) {
+		if (request_num == 0 && ret == 0) {
 			/* if all server replied, or done, stop query, release resource */
 			_dns_client_query_remove(query);
 		}
 
 		if (ret == 0) {
 			query->has_result = 1;
+		} else {
+			/* remove this result */
+			_dns_replied_check_remove(query, from, from_len);
+			atomic_inc(&query->dns_request_sent);
 		}
 	}
 

src/dns_server.c

@@ -3288,6 +3288,7 @@ static int _dns_server_process_answer(struct dns_request *request, const char *d
 	struct dns_rrs *rrs = NULL;
 	int ret = 0;
 	int is_skip = 0;
+	int has_result = 0;
 
 	if (packet->head.rcode != DNS_RC_NOERROR && packet->head.rcode != DNS_RC_NXDOMAIN) {
 		if (request->rcode == DNS_RC_SERVFAIL) {
@@ -3302,6 +3303,7 @@ static int _dns_server_process_answer(struct dns_request *request, const char *d
 	for (j = 1; j < DNS_RRS_OPT; j++) {
 		rrs = dns_get_rrs_start(packet, j, &rr_count);
 		for (i = 0; i < rr_count && rrs; i++, rrs = dns_get_rrs_next(packet, rrs)) {
+			has_result = 1;
 			switch (rrs->type) {
 			case DNS_T_A: {
 				ret = _dns_server_process_answer_A(rrs, request, domain, cname, result_flag);
@@ -3380,6 +3382,12 @@ static int _dns_server_process_answer(struct dns_request *request, const char *d
 		request->rcode = packet->head.rcode;
 	}
 
+	if (has_result == 0 && request->rcode == DNS_RC_NOERROR) {
+		tlog(TLOG_DEBUG, "no result, %s qtype: %d, rcode: %d, id: %d, retry", domain, request->qtype,
+			 packet->head.rcode, packet->head.id);
+		return -1;
+	}
+
 	return 0;
 }
 
@@ -3788,9 +3796,9 @@ static int dns_server_resolve_callback(const char *domain, dns_result_type rtype
 	}
 
 	if (rtype == DNS_QUERY_RESULT) {
-		tlog(TLOG_DEBUG, "query result from server %s:%d, type: %d, rcode: %d, id: %d",
+		tlog(TLOG_DEBUG, "query result from server %s:%d, type: %d, domain: %s qtype: %d rcode: %d, id: %d",
 			 dns_client_get_server_ip(server_info), dns_client_get_server_port(server_info),
-			 dns_client_get_server_type(server_info), packet->head.rcode, request->id);
+			 dns_client_get_server_type(server_info), domain, request->qtype, packet->head.rcode, request->id);
 
 		if (request->passthrough == 1 && atomic_read(&request->notified) == 0) {
 			struct dns_server_post_context context;
@@ -3837,9 +3845,9 @@ static int dns_server_resolve_callback(const char *domain, dns_result_type rtype
 			}
 		}
 
-		_dns_server_process_answer(request, domain, packet, result_flag);
+		ret = _dns_server_process_answer(request, domain, packet, result_flag);
 		_dns_server_passthrough_may_complete(request);
-		return 0;
+		return ret;
 	} else if (rtype == DNS_QUERY_ERR) {
 		tlog(TLOG_ERROR, "request failed, %s", domain);
 		return -1;