Add systemd script

2018-06-16 02:36:04 +08:00
parent 53df9f7063
commit 7b62739c13
34 changed files with 746 additions and 869 deletions
--- a/src/dns_client.c
+++ b/src/dns_client.c
@@ -0,0 +1,934 @@
+/*************************************************************************
+ *
+ * Copyright (C) 2018 Ruilin Peng (Nick) <pymumu@gmail.com>.
+ *
+ * smartdns is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * smartdns is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "dns_client.h"
+#include "atomic.h"
+#include "dns.h"
+#include "fast_ping.h"
+#include "hashtable.h"
+#include "list.h"
+#include "tlog.h"
+#include "util.h"
+#include <arpa/inet.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/filter.h>
+#include <netdb.h>
+#include <netinet/icmp6.h>
+#include <netinet/ip.h>
+#include <netinet/ip6.h>
+#include <netinet/ip_icmp.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/epoll.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#define DNS_MAX_HOSTNAME 256
+#define DNS_MAX_EVENTS 64
+#define DNS_HOSTNAME_LEN 128
+
+/* dns client */
+struct dns_client {
+	pthread_t tid;
+	int run;
+	int epoll_fd;
+
+	/* dns server list */
+	pthread_mutex_t server_list_lock;
+	struct list_head dns_server_list;
+
+	/* query list */
+	pthread_mutex_t dns_request_lock;
+	struct list_head dns_request_list;
+
+	/* query doman hash table, key: sid + domain */
+	pthread_mutex_t domain_map_lock;
+	DECLARE_HASHTABLE(domain_map, 6);
+
+	/* client socket */
+	int udp;
+};
+
+/* dns server information */
+struct dns_server_info {
+	struct list_head list;
+	/* server ping handle */
+	struct ping_host_struct *ping_host;
+
+	/* server type */
+	dns_server_type_t type;
+
+	/* server addr info */
+	unsigned short ss_family;
+	socklen_t addr_len;
+	union {
+		struct sockaddr_in in;
+		struct sockaddr_in6 in6;
+		struct sockaddr addr;
+	};
+};
+
+/* dns replied server info */
+struct dns_query_replied {
+	struct hlist_node node;
+	socklen_t addr_len;
+	union {
+		struct sockaddr_in in;
+		struct sockaddr_in6 in6;
+		struct sockaddr addr;
+	};
+};
+
+/* query struct */
+struct dns_query_struct {
+	atomic_t refcnt;
+	/* query id, hash key sid + domain*/
+	char domain[DNS_MAX_CNAME_LEN];
+	unsigned short sid;
+	struct hlist_node domain_node;
+
+	struct list_head dns_request_list;
+	struct list_head period_list;
+
+	/* dns query type */
+	int qtype;
+
+	/* dns query number */
+	atomic_t dns_request_sent;
+	unsigned long send_tick;
+
+	/* caller notification */
+	dns_client_callback callback;
+	void *user_ptr;
+
+	/* replied hash table */
+	DECLARE_HASHTABLE(replied_map, 4);
+};
+
+static struct dns_client client;
+static atomic_t dns_client_sid = ATOMIC_INIT(0);
+
+/* get addr info */
+static struct addrinfo *_dns_client_getaddr(const char *host, char *port, int type, int protocol)
+{
+	struct addrinfo hints;
+	struct addrinfo *result = NULL;
+	int ret = 0;
+
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = AF_UNSPEC;
+	hints.ai_socktype = type;
+	hints.ai_protocol = protocol;
+
+	ret = getaddrinfo(host, port, &hints, &result);
+	if (ret != 0) {
+		tlog(TLOG_ERROR, "get addr info failed. %s\n", gai_strerror(errno));
+		tlog(TLOG_ERROR, "host = %s, port = %s, type = %d, protocol = %d", host, port, type, protocol);
+		goto errout;
+	}
+
+	return result;
+errout:
+	if (result) {
+		freeaddrinfo(result);
+	}
+	return NULL;
+}
+
+/* check whether server exists */
+int _dns_client_server_exist(struct addrinfo *gai, dns_server_type_t server_type)
+{
+	struct dns_server_info *server_info, *tmp;
+	pthread_mutex_lock(&client.server_list_lock);
+	list_for_each_entry_safe(server_info, tmp, &client.dns_server_list, list)
+	{
+		if (server_info->addr_len != gai->ai_addrlen || server_info->ss_family != gai->ai_family) {
+			continue;
+		}
+
+		if (server_info->type != server_type) {
+			continue;
+		}
+
+		if (memcmp(&server_info->addr, gai->ai_addr, gai->ai_addrlen) != 0) {
+			continue;
+		}
+
+		pthread_mutex_lock(&client.server_list_lock);
+		return 0;
+	}
+
+	pthread_mutex_unlock(&client.server_list_lock);
+	return -1;
+}
+
+/* add dns server information */
+int _dns_client_server_add(char *server_ip, struct addrinfo *gai, dns_server_type_t server_type)
+{
+	struct dns_server_info *server_info = NULL;
+
+	if (_dns_client_server_exist(gai, server_type) == 0) {
+		goto errout;
+	}
+
+	server_info = malloc(sizeof(*server_info));
+	if (server_info == NULL) {
+		goto errout;
+	}
+	memset(server_info, 0, sizeof(*server_info));
+	server_info->ss_family = gai->ai_family;
+	server_info->addr_len = gai->ai_addrlen;
+	server_info->type = server_type;
+	if (gai->ai_addrlen > sizeof(server_info->in6)) {
+		tlog(TLOG_ERROR, "addr len invalid, %d, %zd, %d", gai->ai_addrlen, sizeof(server_info->addr), server_info->ss_family);
+		goto errout;
+	}
+	memcpy(&server_info->addr, gai->ai_addr, gai->ai_addrlen);
+
+	/* start ping task */
+	server_info->ping_host = fast_ping_start(server_ip, 0, 60000, 1000, NULL, server_info);
+	if (server_info->ping_host == NULL) {
+		goto errout;
+	}
+
+	/* add to list */
+	pthread_mutex_lock(&client.server_list_lock);
+	list_add(&server_info->list, &client.dns_server_list);
+	pthread_mutex_unlock(&client.server_list_lock);
+	return 0;
+errout:
+	if (server_info) {
+		if (server_info->ping_host) {
+			fast_ping_stop(server_info->ping_host);
+		}
+		free(server_info);
+	}
+
+	return -1;
+}
+
+/* remove all servers information */
+void _dns_client_server_remove_all(void)
+{
+	struct dns_server_info *server_info, *tmp;
+	pthread_mutex_lock(&client.server_list_lock);
+	list_for_each_entry_safe(server_info, tmp, &client.dns_server_list, list)
+	{
+		list_del(&server_info->list);
+		/* stop ping task */
+		if (fast_ping_stop(server_info->ping_host) != 0) {
+			tlog(TLOG_ERROR, "stop ping failed.\n");
+		}
+		free(server_info);
+	}
+	pthread_mutex_unlock(&client.server_list_lock);
+}
+
+/* remove single server */
+int _dns_client_server_remove(char *server_ip, struct addrinfo *gai, dns_server_type_t server_type)
+{
+	struct dns_server_info *server_info, *tmp;
+
+	/* find server and remove */
+	pthread_mutex_lock(&client.server_list_lock);
+	list_for_each_entry_safe(server_info, tmp, &client.dns_server_list, list)
+	{
+		if (server_info->addr_len != gai->ai_addrlen || server_info->ss_family != gai->ai_family) {
+			continue;
+		}
+
+		if (memcmp(&server_info->addr, gai->ai_addr, gai->ai_addrlen) != 0) {
+			continue;
+		}
+		list_del(&server_info->list);
+		pthread_mutex_unlock(&client.server_list_lock);
+		if (fast_ping_stop(server_info->ping_host) != 0) {
+			tlog(TLOG_ERROR, "stop ping failed.\n");
+		}
+		free(server_info);
+		return 0;
+	}
+	pthread_mutex_unlock(&client.server_list_lock);
+	return -1;
+}
+
+int _dns_client_server_operate(char *server_ip, int port, dns_server_type_t server_type, int operate)
+{
+	char port_s[8];
+	int sock_type;
+	int ret;
+	struct addrinfo *gai = NULL;
+
+	if (server_type >= DNS_SERVER_TYPE_END) {
+		return -1;
+	}
+
+	if (server_type == DNS_SERVER_UDP) {
+		sock_type = SOCK_DGRAM;
+	} else {
+		sock_type = SOCK_STREAM;
+	}
+
+	/* get addr info */
+	snprintf(port_s, 8, "%d", port);
+	gai = _dns_client_getaddr(server_ip, port_s, sock_type, 0);
+	if (gai == NULL) {
+		tlog(TLOG_ERROR, "get address failed, %s:%d", server_ip, port);
+		goto errout;
+	}
+
+	if (operate == 0) {
+		ret = _dns_client_server_add(server_ip, gai, server_type);
+		if (ret != 0) {
+			goto errout;
+		}
+	} else {
+		ret = _dns_client_server_remove(server_ip, gai, server_type);
+		if (ret != 0) {
+			goto errout;
+		}
+	}
+	freeaddrinfo(gai);
+	return 0;
+errout:
+	if (gai) {
+		freeaddrinfo(gai);
+	}
+	return -1;
+}
+
+int dns_add_server(char *server_ip, int port, dns_server_type_t server_type)
+{
+	return _dns_client_server_operate(server_ip, port, server_type, 0);
+}
+
+int dns_remove_server(char *server_ip, int port, dns_server_type_t server_type)
+{
+	return _dns_client_server_operate(server_ip, port, server_type, 1);
+}
+
+void _dns_client_query_release(struct dns_query_struct *query)
+{
+	int refcnt = atomic_dec_return(&query->refcnt);
+	int bucket = 0;
+	struct dns_query_replied *replied_map;
+	struct hlist_node *tmp;
+
+	if (refcnt) {
+		if (refcnt < 0) {
+			tlog(TLOG_ERROR, "BUG: refcnt is %d", refcnt);
+			abort();
+		}
+		return;
+	}
+
+	/* notify caller query end */
+	if (query->callback) {
+		query->callback(query->domain, DNS_QUERY_END, NULL, NULL, 0, query->user_ptr);
+	}
+
+	/* free resource */
+	pthread_mutex_lock(&client.domain_map_lock);
+	list_del_init(&query->dns_request_list);
+	hash_del(&query->domain_node);
+	pthread_mutex_unlock(&client.domain_map_lock);
+
+	hash_for_each_safe(query->replied_map, bucket, tmp, replied_map, node)
+	{
+		hash_del(&replied_map->node);
+		free(replied_map);
+	}
+	memset(query, 0, sizeof(*query));
+	free(query);
+}
+
+void _dns_client_query_remove(struct dns_query_struct *query)
+{
+	/* remove query from period check list, and release reference*/
+	pthread_mutex_lock(&client.domain_map_lock);
+	list_del_init(&query->dns_request_list);
+	hash_del(&query->domain_node);
+	pthread_mutex_unlock(&client.domain_map_lock);
+
+	_dns_client_query_release(query);
+}
+
+void _dns_client_query_remove_all(void)
+{
+	struct dns_query_struct *query, *tmp;
+	LIST_HEAD(check_list);
+
+	pthread_mutex_lock(&client.domain_map_lock);
+	list_for_each_entry_safe(query, tmp, &client.dns_request_list, dns_request_list)
+	{
+		list_add(&query->period_list, &check_list);
+	}
+	pthread_mutex_unlock(&client.domain_map_lock);
+
+	list_for_each_entry_safe(query, tmp, &check_list, period_list)
+	{
+		list_del_init(&query->period_list);
+		_dns_client_query_remove(query);
+	}
+
+	return;
+}
+
+void _dns_client_query_get(struct dns_query_struct *query)
+{
+	atomic_inc(&query->refcnt);
+}
+
+void _dns_client_period_run(void)
+{
+	struct dns_query_struct *query, *tmp;
+	LIST_HEAD(check_list);
+
+	unsigned long now = get_tick_count();
+
+	/* get query which timed out to check list */ 
+	pthread_mutex_lock(&client.domain_map_lock);
+	list_for_each_entry_safe(query, tmp, &client.dns_request_list, dns_request_list)
+	{
+		if (now - query->send_tick >= 1000) {
+			list_add(&query->period_list, &check_list);
+			_dns_client_query_get(query);
+		}
+	}
+	pthread_mutex_unlock(&client.domain_map_lock);
+
+	list_for_each_entry_safe(query, tmp, &check_list, period_list)
+	{
+		/* free timed out query, and notify caller */
+		list_del_init(&query->period_list);
+		_dns_client_query_remove(query);
+		_dns_client_query_release(query);
+	}
+	return;
+}
+
+static struct dns_query_struct *_dns_client_get_request(unsigned short sid, char *domain)
+{
+	struct dns_query_struct *query = NULL;
+	struct dns_query_struct *query_result = NULL;
+	struct hlist_node *tmp = NULL;
+	unsigned int key;
+
+	/* get query by hash key : id + domain */
+	key = hash_string(domain);
+	key = jhash(&sid, sizeof(sid), key);
+	pthread_mutex_lock(&client.domain_map_lock);
+	hash_for_each_possible_safe(client.domain_map, query, tmp, domain_node, key)
+	{
+		if (strncmp(query->domain, domain, DNS_MAX_CNAME_LEN) != 0) {
+			continue;
+		}
+
+		if (sid != query->sid) {
+			continue;
+		}
+		query_result = query;
+		break;
+	}
+	pthread_mutex_unlock(&client.domain_map_lock);
+
+	return query_result;
+}
+
+int _dns_replied_check_add(struct dns_query_struct *dns_query, struct sockaddr *addr, socklen_t addr_len)
+{
+	int key = 0;
+	struct dns_query_replied *replied_map = NULL;
+
+	if (addr_len > sizeof(struct sockaddr_in6)) {
+		tlog(TLOG_ERROR, "addr length is invalid.");
+		return -1;
+	}
+
+	/* avoid multiple replies from one server */
+	key = jhash(addr, addr_len, 0);
+	hash_for_each_possible(dns_query->replied_map, replied_map, node, key)
+	{
+		/* already replied, ignore this reply */
+		if (memcmp(&replied_map->addr, addr, addr_len) == 0) {
+			return -1;
+		}
+	}
+
+	replied_map = malloc(sizeof(*replied_map));
+	if (replied_map == NULL) {
+		tlog(TLOG_ERROR, "malloc failed");
+		return -1;
+	}
+
+	/* add address info to check hashtable */
+	memcpy(&replied_map->addr, addr, addr_len);
+	hash_add(dns_query->replied_map, &replied_map->node, key);
+	return 0;
+}
+
+static int _dns_client_recv(unsigned char *inpacket, int inpacket_len, struct sockaddr_storage *from, socklen_t from_len)
+{
+	int len;
+	int i;
+	int qtype;
+	int qclass;
+	char domain[DNS_MAX_CNAME_LEN];
+	int rr_count;
+	struct dns_rrs *rrs = NULL;
+	unsigned char packet_buff[DNS_PACKSIZE];
+	struct dns_packet *packet = (struct dns_packet *)packet_buff;
+	int ret = 0;
+	struct dns_query_struct *query;
+	int request_num = 0;
+
+	packet->head.tc = 0;
+
+	/* decode domain from udp packet */
+	len = dns_decode(packet, DNS_PACKSIZE, inpacket, inpacket_len);
+	if (len != 0) {
+		tlog(TLOG_ERROR, "decode failed, packet len = %d, tc=%d, %d\n", inpacket_len, packet->head.tc, packet->head.id);
+		return -1;
+	}
+
+	/* not answer, return error */
+	if (packet->head.qr != DNS_OP_IQUERY) {
+		tlog(TLOG_ERROR, "message type error.\n");
+		return -1;
+	}
+
+	tlog(TLOG_DEBUG, "qdcount = %d, ancount = %d, nscount = %d, nrcount = %d, len = %d, id = %d, tc = %d, rd = %d, ra = %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);
+
+	/* get question */
+	rrs = dns_get_rrs_start(packet, DNS_RRS_QD, &rr_count);
+	for (i = 0; i < rr_count && rrs; i++, rrs = dns_get_rrs_next(packet, rrs)) {
+		dns_get_domain(rrs, domain, DNS_MAX_CNAME_LEN, &qtype, &qclass);
+		tlog(TLOG_DEBUG, "domain: %s qtype: %d  qclass: %d\n", domain, qtype, qclass);
+	}
+
+	/* get query reference */
+	query = _dns_client_get_request(packet->head.id, domain);
+	if (query == NULL) {
+		return 0;
+	}
+
+	/* avoid multiple replies */
+	if (_dns_replied_check_add(query, (struct sockaddr *)from, from_len) != 0) {
+		return 0;
+	}
+
+	request_num = atomic_dec_return(&query->dns_request_sent);
+	if (request_num < 0) {
+		tlog(TLOG_ERROR, "send count is invalid, %d", request_num);
+		return -1;
+	}
+
+	/* notify caller dns query result */
+	if (query->callback) {
+		ret = query->callback(query->domain, DNS_QUERY_RESULT, packet, inpacket, inpacket_len, query->user_ptr);
+	}
+
+	if (request_num == 0 || ret) {
+		/* if all server replied, or done, stop query, release resource */
+		_dns_client_query_remove(query);
+	} 
+
+	return ret;
+}
+
+static int _dns_client_process(struct dns_query_struct *dns_query, unsigned long now)
+{
+	int len;
+	unsigned char inpacket[DNS_IN_PACKSIZE];
+	struct sockaddr_storage from;
+	socklen_t from_len = sizeof(from);
+	char from_host[DNS_MAX_CNAME_LEN];
+
+	/* receive from udp */
+	len = recvfrom(client.udp, inpacket, sizeof(inpacket), 0, (struct sockaddr *)&from, (socklen_t *)&from_len);
+	if (len < 0) {
+		tlog(TLOG_ERROR, "recvfrom failed, %s\n", strerror(errno));
+		return -1;
+	}
+
+	tlog(TLOG_DEBUG, "recv from %s", gethost_by_addr(from_host, (struct sockaddr *)&from, from_len));
+
+	if (_dns_client_recv(inpacket, len, &from, from_len) != 0) {
+		return -1;
+	}
+
+	return 0;
+}
+
+static void *_dns_client_work(void *arg)
+{
+	struct epoll_event events[DNS_MAX_EVENTS + 1];
+	int num;
+	int i;
+	unsigned long now = {0};
+	unsigned int sleep = 100;
+	int sleep_time;
+	unsigned int expect_time = 0;
+
+	sleep_time = sleep;
+	now = get_tick_count() - sleep;
+	expect_time = now + sleep;
+	while (client.run) {
+		now = get_tick_count();
+		if (now >= expect_time) {
+			_dns_client_period_run();
+			sleep_time = sleep - (now - expect_time);
+			if (sleep_time < 0) {
+				sleep_time = 0;
+				expect_time = now;
+			}
+			expect_time += sleep;
+		}
+
+		num = epoll_wait(client.epoll_fd, events, DNS_MAX_EVENTS, sleep_time);
+		if (num < 0) {
+			usleep(100000);
+			continue;
+		}
+
+		for (i = 0; i < num; i++) {
+			struct epoll_event *event = &events[i];
+			struct dns_query_struct *dns_query = (struct dns_query_struct *)event->data.ptr;
+			_dns_client_process(dns_query, now);
+		}
+	}
+
+	close(client.epoll_fd);
+	client.epoll_fd = -1;
+
+	return NULL;
+}
+
+static int _dns_client_send_udp(struct dns_server_info *server_info, void *packet, int len)
+{
+	int send_len = 0;
+	send_len = sendto(client.udp, packet, len, 0, (struct sockaddr *)&server_info->addr, server_info->addr_len);
+	if (send_len != len) {
+		return -1;
+	}
+
+	return 0;
+}
+
+static int _dns_client_send_tcp(struct dns_server_info *server_info, void *packet, int len)
+{
+	return -1;
+}
+
+
+static int _dns_client_send_packet(struct dns_query_struct *query, void *packet, int len)
+{
+	struct dns_server_info *server_info, *tmp;
+	int ret = 0;
+
+	query->send_tick = get_tick_count();
+
+	/* send query to all dns servers */
+	pthread_mutex_lock(&client.server_list_lock);
+	list_for_each_entry_safe(server_info, tmp, &client.dns_server_list, list)
+	{
+		atomic_inc(&query->dns_request_sent);
+		switch (server_info->type) {
+		case DNS_SERVER_UDP:
+			/* udp query */
+			ret = _dns_client_send_udp(server_info, packet, len);
+			break;
+		case DNS_SERVER_TCP:
+			/* tcp query */
+			ret = _dns_client_send_tcp(server_info, packet, len);
+			break;
+		default:
+			/* unsupport query type */
+			ret = -1;
+			break;
+		}
+
+		if (ret != 0) {
+			char server_addr[128];
+			tlog(TLOG_ERROR, "send query to %s failed, %s", gethost_by_addr(server_addr, &server_info->addr, server_info->addr_len), strerror(errno));
+			atomic_dec(&query->dns_request_sent);
+			continue;
+		}
+	}
+	pthread_mutex_unlock(&client.server_list_lock);
+	return 0;
+}
+
+static int _dns_client_send_query(struct dns_query_struct *query, char *doamin)
+{
+	unsigned char packet_buff[DNS_PACKSIZE];
+	unsigned char inpacket[DNS_IN_PACKSIZE];
+	struct dns_packet *packet = (struct dns_packet *)packet_buff;
+	int encode_len;
+
+	/* init dns packet head */
+	struct dns_head head;
+	memset(&head, 0, sizeof(head));
+	head.id = query->sid;
+	head.qr = DNS_QR_QUERY;
+	head.opcode = DNS_OP_QUERY;
+	head.aa = 0;
+	head.rd = 1;
+	head.ra = 0;
+	head.rcode = 0;
+
+	dns_packet_init(packet, DNS_PACKSIZE, &head);
+
+	/* add question */
+	dns_add_domain(packet, doamin, query->qtype, DNS_C_IN);
+
+	/* encode packet */
+	encode_len = dns_encode(inpacket, DNS_IN_PACKSIZE, packet);
+	if (encode_len <= 0) {
+		tlog(TLOG_ERROR, "encode query failed.");
+		return -1;
+	}
+
+	/* send query packet */
+	return _dns_client_send_packet(query, inpacket, encode_len);
+}
+
+int dns_client_query(char *domain, int qtype, dns_client_callback callback, void *user_ptr)
+{
+	struct dns_query_struct *query = NULL;
+	int ret = 0;
+	unsigned int key = 0;
+
+	query = malloc(sizeof(*query));
+	if (query == NULL) {
+		goto errout;
+	}
+	memset(query, 0, sizeof(*query));
+
+	INIT_HLIST_NODE(&query->domain_node);
+	INIT_LIST_HEAD(&query->dns_request_list);
+	atomic_set(&query->refcnt, 0);
+	atomic_set(&query->dns_request_sent, 0);
+	hash_init(query->replied_map);
+	strncpy(query->domain, domain, DNS_MAX_CNAME_LEN);
+	query->user_ptr = user_ptr;
+	query->callback = callback;
+	query->qtype = qtype;
+	query->send_tick = 0;
+	query->sid = atomic_inc_return(&dns_client_sid);
+
+	_dns_client_query_get(query);
+	/* add query to hashtable */
+	key = hash_string(domain);
+	key = jhash(&query->sid, sizeof(query->sid), key);
+	pthread_mutex_lock(&client.domain_map_lock);
+	list_add_tail(&query->dns_request_list, &client.dns_request_list);
+	hash_add(client.domain_map, &query->domain_node, key);
+	pthread_mutex_unlock(&client.domain_map_lock);
+
+	/* send query */
+	ret = _dns_client_send_query(query, domain);
+	if (ret != 0) {
+		goto errout_del_list;
+	}
+
+	tlog(TLOG_INFO, "send request %s, id %d\n", domain, query->sid);
+
+	return 0;
+errout_del_list:
+	atomic_dec(&query->refcnt);
+	pthread_mutex_lock(&client.domain_map_lock);
+	list_del_init(&query->dns_request_list);
+	hash_del(&query->domain_node);
+	pthread_mutex_unlock(&client.domain_map_lock);
+errout:
+	if (query) {
+		tlog(TLOG_ERROR, "release %p", query);
+		free(query);
+	}
+	return -1;
+}
+
+static struct addrinfo *_dns_server_getaddr(const char *host, const char *port, int type, int protocol)
+{
+	struct addrinfo hints;
+	struct addrinfo *result = NULL;
+
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = AF_UNSPEC;
+	hints.ai_socktype = type;
+	hints.ai_protocol = protocol;
+	hints.ai_flags = AI_PASSIVE;
+	if (getaddrinfo(host, port, &hints, &result) != 0) {
+		tlog(TLOG_ERROR, "get addr info failed. %s\n", strerror(errno));
+		goto errout;
+	}
+
+	return result;
+errout:
+	if (result) {
+		freeaddrinfo(result);
+	}
+	return NULL;
+}
+
+int dns_client_start(void)
+{
+	struct epoll_event event;
+	memset(&event, 0, sizeof(event));
+	event.events = EPOLLIN;
+	event.data.fd = client.udp;
+	if (epoll_ctl(client.epoll_fd, EPOLL_CTL_ADD, client.udp, &event) != 0) {
+		tlog(TLOG_ERROR, "epoll ctl failed.");
+		return -1;
+	}
+
+	return 0;
+}
+
+int dns_client_socket(void)
+{
+	int fd = -1;
+	struct addrinfo *gai = NULL;
+
+	/* create udp socket */
+	gai = _dns_server_getaddr(NULL, "53", SOCK_DGRAM, 0);
+	if (gai == NULL) {
+		tlog(TLOG_ERROR, "get address failed.\n");
+		goto errout;
+	}
+
+	fd = socket(gai->ai_family, gai->ai_socktype, gai->ai_protocol);
+	if (fd < 0) {
+		tlog(TLOG_ERROR, "create socket failed.\n");
+		goto errout;
+	}
+
+	client.udp = fd;
+	freeaddrinfo(gai);
+
+	return fd;
+errout:
+	if (fd > 0) {
+		close(fd);
+	}
+
+	if (gai) {
+		freeaddrinfo(gai);
+	}
+	return -1;
+}
+
+int dns_client_init()
+{
+	pthread_attr_t attr;
+	int epollfd = -1;
+	int ret;
+	int fd = -1;
+
+	if (client.epoll_fd > 0) {
+		return -1;
+	}
+
+	memset(&client, 0, sizeof(client));
+	pthread_attr_init(&attr);
+
+	epollfd = epoll_create1(EPOLL_CLOEXEC);
+	if (epollfd < 0) {
+		tlog(TLOG_ERROR, "create epoll failed, %s\n", strerror(errno));
+		goto errout;
+	}
+
+	fd = dns_client_socket();
+	if (fd < 0) {
+		tlog(TLOG_ERROR, "create client socket failed.\n");
+		goto errout;
+	}
+
+	pthread_mutex_init(&client.server_list_lock, 0);
+	INIT_LIST_HEAD(&client.dns_server_list);
+
+	pthread_mutex_init(&client.domain_map_lock, 0);
+	hash_init(client.domain_map);
+	INIT_LIST_HEAD(&client.dns_request_list);
+
+	client.epoll_fd = epollfd;
+	client.run = 1;
+	client.udp = fd;
+
+	/* start work task */
+	ret = pthread_create(&client.tid, &attr, _dns_client_work, NULL);
+	if (ret != 0) {
+		tlog(TLOG_ERROR, "create client work thread failed, %s\n", strerror(errno));
+		goto errout;
+	}
+
+	if (dns_client_start()) {
+		tlog(TLOG_ERROR, "start client failed.\n");
+		goto errout;
+	}
+
+	return 0;
+errout:
+	if (client.tid > 0) {
+		void *retval = NULL;
+		client.run = 0;
+		pthread_join(client.tid, &retval);
+	}
+
+	if (client.udp > 0) {
+		close(client.udp);
+		client.udp = -1;
+	}
+
+	if (epollfd) {
+		close(epollfd);
+	}
+
+	pthread_mutex_destroy(&client.server_list_lock);
+	pthread_mutex_destroy(&client.domain_map_lock);
+
+	return -1;
+}
+
+void dns_client_exit()
+{
+	if (client.tid > 0) {
+		void *ret = NULL;
+		client.run = 0;
+		pthread_join(client.tid, &ret);
+	}
+
+	if (client.udp > 0) {
+		close(client.udp);
+	}
+
+	/* free all resouces */
+	_dns_client_server_remove_all();
+	_dns_client_query_remove_all();
+
+	pthread_mutex_destroy(&client.server_list_lock);
+	pthread_mutex_destroy(&client.domain_map_lock);
+}