dns_server: try refresh NDP by sending ICMP ping.

src/dns_server.c

@@ -79,7 +79,7 @@
 #define CACHE_AUTO_ENABLE_SIZE (1024 * 1024 * 128)
 #define EXPIRED_DOMAIN_PREFETCH_TIME (3600 * 8)
 #define DNS_MAX_DOMAIN_REFETCH_NUM 64
-#define DNS_SERVER_NEIGHBOR_CACHE_MAX_NUM 8192
+#define DNS_SERVER_NEIGHBOR_CACHE_MAX_NUM (1024 * 8)
 #define DNS_SERVER_NEIGHBOR_CACHE_TIMEOUT (3600 * 1)
 #define DNS_SERVER_NEIGHBOR_CACHE_NOMAC_TIMEOUT 60
 
@@ -3619,13 +3619,36 @@ static struct dns_client_rules *_dns_server_get_client_rules_by_mac(uint8_t *net
 	args.netaddr = netaddr;
 	args.netaddr_len = netaddr_len;
 
-	ret = netlink_get_neighbors(family, _dns_server_neighbors_callback, &args);
-	if (ret < 0) {
-		goto add_cache;
-	}
+	for (int i = 0; i < 2; i++) {
+		ret = netlink_get_neighbors(family, _dns_server_neighbors_callback, &args);
+		if (ret < 0) {
+			goto add_cache;
+		}
+
+		if (ret != 1) {
+			/* FIXME: ugly force refresh NDP table by sending ICMP message.*/
+			if (i == 0) {
+				char host[DNS_MAX_CNAME_LEN] = {0};
+				if (family == AF_INET) {
+					snprintf(host, sizeof(host), "%d.%d.%d.%d", netaddr[0], netaddr[1], netaddr[2], netaddr[3]);
+				} else if (family == AF_INET6) {
+					snprintf(host, sizeof(host),
+							 "%.2x%.2x:%.2x%.2x:%.2x%.2x:%.2x%.2x:%.2x%.2x:%.2x%.2x:%.2x%.2x:%.2x%.2x", netaddr[0],
+							 netaddr[1], netaddr[2], netaddr[3], netaddr[4], netaddr[5], netaddr[6], netaddr[7],
+							 netaddr[8], netaddr[9], netaddr[10], netaddr[11], netaddr[12], netaddr[13], netaddr[14],
+							 netaddr[15]);
+				}
+				struct ping_host_struct *ping_host = fast_ping_start(PING_TYPE_ICMP, host, 0, 10, 1000, NULL, NULL);
+				if (ping_host) {
+					/* wait for NDP*/
+					usleep(100);
+					fast_ping_stop(ping_host);
+					continue;
+				}
+			}
 
-	if (ret != 1) {
-		goto add_cache;
+			goto add_cache;
+		}
 	}
 
 	if (args.group_mac == NULL) {
@@ -7384,7 +7407,6 @@ static int _dns_server_recv(struct dns_server_conn_head *conn, unsigned char *in
 		 "%d, rcode = %d\n",
 		 packet->head.qdcount, packet->head.ancount, packet->head.nscount, packet->head.nrcount, inpacket_len,
 		 packet->head.id, packet->head.tc, packet->head.rd, packet->head.ra, packet->head.rcode);
-
 	client_rules = _dns_server_get_client_rules(from, from_len);
 	request = _dns_server_new_request();
 	if (request == NULL) {