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;

test/cases/test-cache.cc

@@ -455,4 +455,52 @@ cache-persist yes
 		server.Stop();
 		usleep(200 * 1000);
 	}
+}
+
+TEST_F(Cache, cname)
+{
+	smartdns::MockServer server_upstream;
+	smartdns::Server server;
+
+	server_upstream.Start("udp://0.0.0.0:61053", [](struct smartdns::ServerRequestContext *request) {
+		std::string domain = request->domain;
+		std::string cname = "cname." + domain;
+		if (request->qtype != DNS_T_A) {
+			return smartdns::SERVER_REQUEST_SOA;
+		}
+
+		unsigned char addr[4] = {1, 2, 3, 4};
+		dns_add_domain(request->response_packet, domain.c_str(), DNS_T_A, DNS_C_IN);
+		dns_add_CNAME(request->response_packet, DNS_RRS_AN, domain.c_str(), 300, cname.c_str());
+		dns_add_A(request->response_packet, DNS_RRS_AN, cname.c_str(), 300, addr);
+		request->response_packet->head.rcode = DNS_RC_NOERROR;
+		return smartdns::SERVER_REQUEST_OK;
+	});
+
+	server.Start(R"""(bind [::]:60053
+server 127.0.0.1:61053
+log-num 0
+cache-size 100
+log-console yes
+log-level debug
+cache-persist no)""");
+	smartdns::Client client;
+	ASSERT_TRUE(client.Query("a.com A", 60053));
+	std::cout << client.GetResult() << std::endl;
+	ASSERT_EQ(client.GetAnswerNum(), 2);
+	EXPECT_EQ(client.GetStatus(), "NOERROR");
+	EXPECT_EQ(client.GetAnswer()[0].GetName(), "a.com");
+	EXPECT_GE(client.GetAnswer()[0].GetTTL(), 3);
+	EXPECT_EQ(client.GetAnswer()[0].GetData(), "cname.a.com.");
+	EXPECT_EQ(client.GetAnswer()[1].GetName(), "cname.a.com");
+	EXPECT_GE(client.GetAnswer()[1].GetTTL(), 3);
+	EXPECT_EQ(client.GetAnswer()[1].GetData(), "1.2.3.4");
+
+	ASSERT_TRUE(client.Query("cname.a.com A", 60053));
+	std::cout << client.GetResult() << std::endl;
+	ASSERT_EQ(client.GetAnswerNum(), 1);
+	EXPECT_EQ(client.GetStatus(), "NOERROR");
+	EXPECT_EQ(client.GetAnswer()[0].GetName(), "cname.a.com");
+	EXPECT_GE(client.GetAnswer()[0].GetTTL(), 3);
+	EXPECT_EQ(client.GetAnswer()[0].GetData(), "1.2.3.4");
 }

test/cases/test-dualstack.cc

@@ -134,7 +134,7 @@ cache-persist no)""");
 	EXPECT_EQ(client.GetAnswer()[1].GetData(), "2001:db8::2");
 }
 
-TEST_F(DualStack, ipv6_prefer_must_exist_ipv4)
+TEST_F(DualStack, ipv6_prefer_without_ipv4)
 {
 	smartdns::MockServer server_upstream;
 	smartdns::Server server;
@@ -232,4 +232,55 @@ cache-persist no)""");
 	EXPECT_EQ(client.GetAuthority()[0].GetName(), "a.com");
 	EXPECT_GT(client.GetAuthority()[0].GetTTL(), 597);
 	EXPECT_EQ(client.GetAuthority()[0].GetType(), "SOA");
-}
+}
+
+TEST_F(DualStack, ipv4_no_response)
+{
+	smartdns::MockServer server_upstream;
+	smartdns::Server server;
+
+	server_upstream.Start("udp://0.0.0.0:61053", [&](struct smartdns::ServerRequestContext *request) {
+		if (request->qtype == DNS_T_A) {
+			smartdns::MockServer::AddIP(request, request->domain.c_str(), "1.2.3.4");
+			smartdns::MockServer::AddIP(request, request->domain.c_str(), "5.6.7.8");
+			return smartdns::SERVER_REQUEST_NO_RESPONSE;
+		} else if (request->qtype == DNS_T_AAAA) {
+			smartdns::MockServer::AddIP(request, request->domain.c_str(), "2001:db8::1");
+			smartdns::MockServer::AddIP(request, request->domain.c_str(), "2001:db8::2");
+			return smartdns::SERVER_REQUEST_OK;
+		}
+		return smartdns::SERVER_REQUEST_SOA;
+	});
+
+	server.MockPing(PING_TYPE_ICMP, "1.2.3.4", 60, 10000);
+	server.MockPing(PING_TYPE_ICMP, "5.6.7.8", 60, 10000);
+	server.MockPing(PING_TYPE_ICMP, "2001:db8::1", 60, 100);
+	server.MockPing(PING_TYPE_ICMP, "2001:db8::2", 60, 110);
+
+	server.Start(R"""(bind [::]:60053
+server 127.0.0.1:61053
+log-num 0
+log-console yes
+dualstack-ip-selection yes
+speed-check-mode ping
+log-level debug
+cache-persist no)""");
+	smartdns::Client client;
+	ASSERT_TRUE(client.Query("a.com A", 60053));
+	std::cout << client.GetResult() << std::endl;
+	ASSERT_EQ(client.GetAnswerNum(), 0);
+	EXPECT_EQ(client.GetStatus(), "SERVFAIL");
+
+	usleep(220 * 1000);
+	ASSERT_TRUE(client.Query("a.com AAAA", 60053));
+	std::cout << client.GetResult() << std::endl;
+	ASSERT_EQ(client.GetAnswerNum(), 2);
+	EXPECT_EQ(client.GetStatus(), "NOERROR");
+	EXPECT_LT(client.GetQueryTime(), 20);
+	EXPECT_EQ(client.GetAnswer()[0].GetName(), "a.com");
+	EXPECT_GT(client.GetAnswer()[0].GetTTL(), 590);
+	EXPECT_EQ(client.GetAnswer()[0].GetData(), "2001:db8::1");
+	EXPECT_EQ(client.GetAnswer()[1].GetName(), "a.com");
+	EXPECT_GT(client.GetAnswer()[1].GetTTL(), 590);
+	EXPECT_EQ(client.GetAnswer()[1].GetData(), "2001:db8::2");
+}

test/cases/test-server.cc

@@ -104,3 +104,69 @@ cache-persist no)""");
 	EXPECT_EQ(client.GetAnswer()[0].GetName(), "a.com");
 	EXPECT_EQ(client.GetAnswer()[0].GetData(), "1.2.3.4");
 }
+
+TEST_F(Server, retry_no_result_with_NOERROR)
+{
+	smartdns::MockServer server_upstream;
+	smartdns::MockServer server_upstream1;
+	smartdns::Server server;
+	int count = 0;
+
+	server_upstream.Start("udp://0.0.0.0:61053", [&](struct smartdns::ServerRequestContext *request) {
+		if (request->qtype != DNS_T_A) {
+			return smartdns::SERVER_REQUEST_SOA;
+		}
+
+		if (count++ < 2) {
+			dns_add_domain(request->response_packet, request->domain.c_str(), request->qtype, request->qclass);
+			return smartdns::SERVER_REQUEST_OK;
+		}
+
+		smartdns::MockServer::AddIP(request, request->domain.c_str(), "1.2.3.4", 611);
+		return smartdns::SERVER_REQUEST_OK;
+	});
+
+	server.Start(R"""(bind [::]:60053
+bind-tcp [::]:60053
+server 127.0.0.1:61053
+log-num 0
+log-console yes
+dualstack-ip-selection no
+log-level debug
+cache-persist no)""");
+	smartdns::Client client;
+	ASSERT_TRUE(client.Query("a.com", 60053));
+	std::cout << client.GetResult() << std::endl;
+	ASSERT_EQ(client.GetAnswerNum(), 1);
+	EXPECT_EQ(client.GetStatus(), "NOERROR");
+	EXPECT_EQ(client.GetAnswer()[0].GetName(), "a.com");
+	EXPECT_EQ(client.GetAnswer()[0].GetData(), "1.2.3.4");
+}
+
+TEST_F(Server, retry_no_response)
+{
+	smartdns::MockServer server_upstream;
+	smartdns::MockServer server_upstream1;
+	smartdns::Server server;
+	int count = 0;
+
+	server_upstream.Start("udp://0.0.0.0:61053", [&](struct smartdns::ServerRequestContext *request) {
+		count++;
+		return smartdns::SERVER_REQUEST_NO_RESPONSE;
+	});
+
+	server.Start(R"""(bind [::]:60053
+bind-tcp [::]:60053
+server 127.0.0.1:61053
+log-num 0
+log-console yes
+log-level debug
+cache-persist no)""");
+	smartdns::Client client;
+	ASSERT_TRUE(client.Query("a.com", 60053));
+	std::cout << client.GetResult() << std::endl;
+	ASSERT_EQ(client.GetAnswerNum(), 0);
+	EXPECT_EQ(client.GetStatus(), "SERVFAIL");
+	EXPECT_GE(client.GetQueryTime(), 1500);
+	EXPECT_GE(count, 8);
+}

test/server.cc

@@ -153,6 +153,8 @@ void MockServer::Run()
 				dns_add_domain(request.response_packet, request.domain.c_str(), request.qtype, request.qclass);
 				request.response_data_len =
 					dns_encode(request.response_data, request.response_data_max_len, request.response_packet);
+			} else if (callback_ret == SERVER_REQUEST_NO_RESPONSE) {
+				continue;
 			} else if (request.response_data_len == 0) {
 				if (callback_ret == SERVER_REQUEST_OK) {
 					request.response_data_len =

test/server.h

@@ -87,6 +87,7 @@ struct ServerRequestContext {
 typedef enum {
 	SERVER_REQUEST_OK = 0,
 	SERVER_REQUEST_ERROR,
+	SERVER_REQUEST_NO_RESPONSE,
 	SERVER_REQUEST_SOA,
 } ServerRequestResult;