Add force AAAA SOA feature

ReadMe.md

@@ -382,6 +382,7 @@ Note: Merlin firmware is derived from ASUS firmware and can theoretically be use
 |server-tcp|Upstream TCP DNS server|None|[IP][:port], Repeatable| server-tcp 8.8.8.8:53
 |address|Domain IP address|None|address /domain/ip| address /www.example.com/1.2.3.4
 |bogus-nxdomain|bogus IP address|None|[IP]，Repeatable| bogus-nxdomain 1.2.3.4
+|force-AAAA-SOA|force AAAA query return SOA|no|[yes\|no]|force-AAAA-SOA yes
 
 ## [Donate](#Donate)  
 

ReadMe_zh-CN.md

@@ -382,6 +382,7 @@ rtt min/avg/max/mdev = 5.954/6.133/6.313/0.195 ms
 |server-tcp|上游TCP DNS|无|[IP][:port]，可重复| server-tcp 8.8.8.8:53
 |address|指定域名IP地址|无|address /domain/ip| address /www.example.com/1.2.3.4
 |bogus-nxdomain|假冒IP地址过滤|无|[ip]，可重复| bogus-nxdomain 1.2.3.4
+|force-AAAA-SOA|强制AAAA地址返回SOA|no|[yes\|no]|force-AAAA-SOA yes
 
 ## [Donate](#Donate)  
 

src/conf.c

@@ -29,6 +29,7 @@ art_tree dns_conf_address;
 int dns_conf_rr_ttl;
 int dns_conf_rr_ttl_min;
 int dns_conf_rr_ttl_max;
+int dns_conf_force_AAAA_SOA;
 
 int load_conf_file(const char *file);
 
@@ -224,6 +225,18 @@ int config_cache_prefetch_domain(char *value)
 	return 0;
 }
 
+int config_force_AAAA_SOA(char *value)
+{
+	/* read dns cache size */
+	if (strncmp("yes", value, sizeof("yes")) == 0 || strncmp("YES", value, sizeof("YES")) == 0) {
+		dns_conf_force_AAAA_SOA = 1;
+	} else if (strncmp("no", value, sizeof("no")) == 0 || strncmp("NO", value, sizeof("NO")) == 0) {
+		dns_conf_force_AAAA_SOA = 0;
+	}
+
+	return 0;
+}
+
 int config_log_level(char *value)
 {
 	/* read log level and set */
@@ -467,6 +480,7 @@ struct config_item config_item[] = {
 	{"rr-ttl", config_rr_ttl},
 	{"rr-ttl-min", config_rr_ttl_min},
 	{"rr-ttl-max", config_rr_ttl_max},
+	{"force-AAAA-SOA", config_force_AAAA_SOA},
 	{"bogus-nxdomain", conf_bogus_nxdomain},
 	{"conf-file", config_addtional_file},
 };

src/conf.h

@@ -63,6 +63,7 @@ extern art_tree dns_conf_address;
 extern int dns_conf_rr_ttl;
 extern int dns_conf_rr_ttl_min;
 extern int dns_conf_rr_ttl_max;
+extern int dns_conf_force_AAAA_SOA;
 
 int dns_bogus_nxdomain_exists(unsigned char *ip, dns_type_t addr_type);
 

src/dns_server.c

@@ -541,10 +541,11 @@ static int _dns_server_process_answer(struct dns_request *request, char *domain,
 	int j = 0;
 	struct dns_rrs *rrs = NULL;
 
-	if (packet->head.rcode != DNS_RC_NOERROR) {
+	if (packet->head.rcode != DNS_RC_NOERROR && packet->head.rcode != DNS_RC_NXDOMAIN) {
 		if (request->rcode == DNS_RC_SERVFAIL) {
 			request->rcode = packet->head.rcode;
 		}
+
 		tlog(TLOG_DEBUG, "inquery failed, %s, rcode = %d, id = %d\n", domain, packet->head.rcode, packet->head.id);
 		return -1;
 	}
@@ -793,6 +794,27 @@ errout:
 	return -1;
 }
 
+static int _dns_server_reply_SOA(int rcode, struct dns_request *request, struct dns_packet *packet)
+{
+	struct dns_soa *soa;
+	
+	request->rcode = rcode;
+	request->has_soa = 1;
+	
+	soa = &request->soa;
+
+	strcpy(soa->mname, "a.gtld-servers.net");
+	strcpy(soa->rname, "nstld.verisign-grs.com");
+	soa->serial = 1800;
+	soa->refresh = 1800;
+	soa->retry = 900;
+	soa->expire = 604800;
+	soa->minimum = 86400;
+	_dns_reply(request);
+
+	return 0;
+}
+
 static void _dns_server_log_rule(char *domain, unsigned char *rule_key, int rule_key_len)
 {
 	char rule_name[DNS_MAX_CNAME_LEN];
@@ -997,6 +1019,11 @@ static int _dns_server_recv(unsigned char *inpacket, int inpacket_len, struct so
 	case DNS_T_A:
 		break;
 	case DNS_T_AAAA:
+		if (dns_conf_force_AAAA_SOA == 1) {
+			_dns_server_reply_SOA(DNS_RC_NOERROR, request, packet);
+			free(request);
+			return 0;
+		}
 		break;
 	default:
 		tlog(TLOG_DEBUG, "unsupport qtype: %d, domain: %s", qtype, request->domain);