diff --git a/src/dns_client.c b/src/dns_client.c
index 2827468..376529b 100644
--- a/src/dns_client.c
+++ b/src/dns_client.c
@@ -447,7 +447,10 @@ int dns_server_num(void)
 
 void _dns_client_query_get(struct dns_query_struct *query)
 {
-	atomic_inc(&query->refcnt);
+	if (atomic_inc_return(&query->refcnt) <= 0) {
+		tlog(TLOG_ERROR, "BUG:query ref is invalid, domain: %s", query->domain);
+		abort();
+	}
 }
 
 void _dns_client_query_release(struct dns_query_struct *query)
diff --git a/src/dns_server.c b/src/dns_server.c
index 370b61d..4fc31ab 100644
--- a/src/dns_server.c
+++ b/src/dns_server.c
@@ -170,7 +170,7 @@ static tlog_log *dns_audit;
 
 static int _dns_server_forward_request(unsigned char *inpacket, int inpacket_len)
 {
-	tlog(TLOG_ERROR, "forward request.\n");
+	tlog(TLOG_DEBUG, "forward request.\n");
 	return -1;
 }
 
@@ -284,7 +284,7 @@ static void _dns_server_client_release(struct dns_server_conn *client)
 
 	if (refcnt) {
 		if (refcnt < 0) {
-			tlog(TLOG_ERROR, "BUG: refcnt is %d", refcnt);
+			tlog(TLOG_ERROR, "BUG: refcnt is %d, type = %d", refcnt, client->type);
 			abort();
 		}
 		return;
@@ -304,7 +304,11 @@ static void _dns_server_client_get(struct dns_server_conn *client)
 	if (client == NULL) {
 		return;
 	}
-	atomic_inc(&client->refcnt);
+	
+	if (atomic_inc_return(&client->refcnt) <= 0) {
+		tlog(TLOG_ERROR, "BUG: client ref is invalid.");
+		abort();
+	}
 }
 
 static int _dns_server_reply_tcp_to_buffer(struct dns_server_conn *client, void *packet, int len)
@@ -652,7 +656,10 @@ void _dns_server_request_release(struct dns_request *request)
 
 void _dns_server_request_get(struct dns_request *request)
 {
-	atomic_inc(&request->refcnt);
+	if (atomic_inc_return(&request->refcnt) <= 0) {
+		tlog(TLOG_ERROR, "BUG: request ref is invalid, %s", request->domain);
+		abort();
+	}
 }
 
 void _dns_server_ping_result(struct ping_host_struct *ping_host, const char *host, FAST_PING_RESULT result, struct sockaddr *addr, socklen_t addr_len,
@@ -964,12 +971,12 @@ static int _dns_server_process_answer(struct dns_request *request, char *domain,
 			case DNS_T_NS: {
 				char cname[128];
 				dns_get_CNAME(rrs, name, 128, &ttl, cname, 128);
-				tlog(TLOG_DEBUG, "NS: %s %d : %s\n", name, ttl, cname);
+				tlog(TLOG_DEBUG, "NS: %s ttl:%d cname: %s\n", name, ttl, cname);
 			} break;
 			case DNS_T_CNAME: {
 				char cname[128];
 				dns_get_CNAME(rrs, name, 128, &ttl, cname, 128);
-				tlog(TLOG_DEBUG, "%s %d : %s\n", name, ttl, cname);
+				tlog(TLOG_DEBUG, "name:%s ttl: %d cname: %s\n", name, ttl, cname);
 				strncpy(request->cname, cname, DNS_MAX_CNAME_LEN);
 				request->ttl_cname = ttl;
 				request->has_cname = 1;
@@ -1295,6 +1302,7 @@ static int _dns_server_recv(struct dns_server_conn *client, unsigned char *inpac
 	memset(request, 0, sizeof(*request));
 	pthread_mutex_init(&request->ip_map_lock, 0);
 	atomic_set(&request->adblock, 0);
+	atomic_set(&request->refcnt, 0);
 	request->ping_ttl_v4 = -1;
 	request->ping_ttl_v6 = -1;
 	request->prefetch = 0;
@@ -1367,12 +1375,20 @@ static int _dns_server_recv(struct dns_server_conn *client, unsigned char *inpac
 	_dns_server_request_get(request);
 	request->send_tick = get_tick_count();
 
-	request->request_wait++;
-	dns_client_query(request->domain, qtype, dns_server_resolve_callback, request);
 	if (qtype == DNS_T_AAAA && dns_conf_dualstack_ip_selection) {
 		_dns_server_request_get(request);
 		request->request_wait++;
-		dns_client_query(request->domain, DNS_T_A, dns_server_resolve_callback, request);
+		if (dns_client_query(request->domain, DNS_T_A, dns_server_resolve_callback, request) != 0) {
+			_dns_server_request_release(request);
+			request->request_wait--;
+		}
+	}
+
+	request->request_wait++;
+	if (dns_client_query(request->domain, qtype, dns_server_resolve_callback, request) != 0) {
+		_dns_server_request_release(request);
+		_dns_server_request_remove(request);
+		goto errout;
 	}
 
 	return 0;
@@ -1559,7 +1575,8 @@ int _dns_server_tcp_process_one_request(struct dns_server_conn *dnsserver)
 			break;
 		}
 
-		request_len = ntohs(*((unsigned short *)(dnsserver->recvbuff.buf + proceed_len)));
+		request_data = (unsigned char *)(dnsserver->recvbuff.buf + proceed_len);
+		request_len = ntohs(*((unsigned short *)(request_data)));
 
 		if (request_len >= sizeof(dnsserver->recvbuff.buf)) {
 			tlog(TLOG_ERROR, "request length is invalid.");
diff --git a/src/fast_ping.c b/src/fast_ping.c
index 636ad04..4de1853 100644
--- a/src/fast_ping.c
+++ b/src/fast_ping.c
@@ -44,6 +44,13 @@
 #define ICMP_PACKET_SIZE (1024 * 64)
 #define ICMP_INPACKET_SIZE 1024
 
+#ifndef ICMP_FILTER
+#define ICMP_FILTER	1
+struct icmp_filter {
+	uint32_t	data;
+};
+#endif
+
 struct ping_dns_head {
 	unsigned short id;
 	unsigned short flag;
@@ -172,7 +179,7 @@ void _fast_ping_install_filter_v6(int sock)
 	once = 1;
 
 	/* Patch bpflet for current identifier. */
-	insns[1] = (struct sock_filter)BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htons(getpid()), 0, 1);
+	insns[1] = (struct sock_filter)BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htons(ping.ident), 0, 1);
 
 	if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter))) {
 		perror("WARNING: failed to install socket filter\n");
@@ -201,7 +208,7 @@ void _fast_ping_install_filter_v4(int sock)
 	once = 1;
 
 	/* Patch bpflet for current identifier. */
-	insns[2] = (struct sock_filter)BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htons(getpid()), 0, 1);
+	insns[2] = (struct sock_filter)BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htons(ping.ident), 0, 1);
 
 	if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter))) {
 		perror("WARNING: failed to install socket filter\n");
@@ -259,7 +266,10 @@ errout:
 
 static void _fast_ping_host_get(struct ping_host_struct *ping_host)
 {
-	atomic_inc(&ping_host->ref);
+	if (atomic_inc_return(&ping_host->ref) <= 0) {
+		tlog(TLOG_ERROR, "BUG: ping host ref is invalid, host: %s", ping_host->host);
+		abort();
+	}
 }
 
 static void _fast_ping_close_host_sock(struct ping_host_struct *ping_host)
@@ -295,7 +305,7 @@ static void _fast_ping_host_put(struct ping_host_struct *ping_host)
 								 ping_host->userptr);
 	}
 
-	tlog(TLOG_DEBUG, "ping %p end", ping_host);
+	tlog(TLOG_DEBUG, "ping end, id %d", ping_host->sid);
 	// memset(ping_host, 0, sizeof(*ping_host));
 	ping_host->type = FAST_PING_END;
 	free(ping_host);
@@ -337,7 +347,7 @@ static int _fast_ping_sendping_v6(struct ping_host_struct *ping_host)
 	icmp6->icmp6_type = ICMP6_ECHO_REQUEST;
 	icmp6->icmp6_code = 0;
 	icmp6->icmp6_cksum = 0;
-	icmp6->icmp6_id = getpid();
+	icmp6->icmp6_id = ping.ident;
 	icmp6->icmp6_seq = htons(ping_host->seq);
 
 	gettimeofday(&packet->msg.tv, 0);
@@ -562,6 +572,10 @@ static int _fast_ping_create_icmp_sock(FAST_PING_TYPE type)
 		return -1;
 	}
 
+	struct icmp_filter filt;
+	filt.data = ~((1 << ICMP_SOURCE_QUENCH) | (1 << ICMP_DEST_UNREACH) | (1 << ICMP_TIME_EXCEEDED) | (1 << ICMP_PARAMETERPROB) | (1 << ICMP_REDIRECT) |
+				  (1 << ICMP_ECHOREPLY));
+	setsockopt(fd, SOL_RAW, ICMP_FILTER, &filt, sizeof filt);
 	setsockopt(fd, SOL_SOCKET, SO_SNDBUF, (const char *)&buffsize, optlen);
 	setsockopt(fd, SOL_SOCKET, SO_RCVBUF, (const char *)&buffsize, optlen);
 	setsockopt(fd, SOL_IP, IP_TTL, &val, sizeof(val));
@@ -1420,7 +1434,7 @@ int fast_ping_init(void)
 	pthread_mutex_init(&ping.lock, 0);
 	hash_init(ping.addrmap);
 	ping.epoll_fd = epollfd;
-	ping.ident = getpid();
+	ping.ident = (getpid() & 0XFFFF);
 	ping.run = 1;
 	ret = pthread_create(&ping.tid, &attr, _fast_ping_work, NULL);
 	if (ret != 0) {