Support TLS query.

etc/smartdns/smartdns.conf

@@ -18,8 +18,8 @@ bind [::]:53
 cache-size 512
 
 # prefetch domain
-# prefetch-domain [true|false]
+# prefetch-domain [yes|no]
-# prefetch-domain true
+# prefetch-domain yes
 
 # ttl for all resource record
 # rr-ttl: ttl for all record
@@ -46,6 +46,10 @@ log-level error
 # server-tcp [IP]:[PORT], default port is 53
 # server-tcp 8.8.8.8
 
+# remote tls dns server list
+# server-tls [IP]:[PORT], default port is 853
+# server-tls 1.1.1.1
+
 # specific address to domain
 # address /domain/ip
 # address /www.example.com/1.2.3.4

src/Makefile

@@ -7,7 +7,7 @@ CFLAGS +=-Iinclude
 CFLAGS += -DBASE_FILE_NAME=\"$(notdir $<)\"
 CXXFLAGS=-O2 -Wall -std=c++11 
 CXXFLAGS +=-Iinclude
-LDFLAGS += -lpthread 
+LDFLAGS += -lpthread -lssl -lcrypto
 
 .PHONY: all
 

src/conf.c

@@ -47,7 +47,7 @@ int config_server_name(char *value)
 	return 0;
 }
 
-int config_server(char *value, dns_server_type_t type)
+int config_server(char *value, dns_server_type_t type, int default_port)
 {
 	int index = dns_conf_server_num;
 	struct dns_servers *server;
@@ -66,7 +66,7 @@ int config_server(char *value, dns_server_type_t type)
 
 	/* if port is not defined, set port to default 53 */
 	if (port == PORT_NOT_DEFINED) {
-		port = DEFAULT_DNS_PORT;
+		port = default_port;
 	}
 
 	server->type = type;
@@ -187,17 +187,17 @@ errout:
 
 int config_server_udp(char *value)
 {
-	return config_server(value, DNS_SERVER_UDP);
+	return config_server(value, DNS_SERVER_UDP, DEFAULT_DNS_PORT);
 }
 
 int config_server_tcp(char *value)
 {
-	return config_server(value, DNS_SERVER_TCP);
+	return config_server(value, DNS_SERVER_TCP, DEFAULT_DNS_PORT);
 }
 
-int config_server_http(char *value)
+int config_server_tls(char *value)
 {
-	return config_server(value, DNS_SERVER_HTTP);
+	return config_server(value, DNS_SERVER_TLS, DEFAULT_DNS_TLS_PORT);
 }
 
 int config_cache_size(char *value)
@@ -470,7 +470,7 @@ struct config_item config_item[] = {
 	{"server", config_server_udp},
 	{"address", config_address},
 	{"server-tcp", config_server_tcp},
-	{"server-http", config_server_http},
+	{"server-tls", config_server_tls},
 	{"cache-size", config_cache_size},
 	{"prefetch-domain", config_cache_prefetch_domain},
 	{"log-level", config_log_level},

src/conf.h

@@ -12,6 +12,7 @@
 #define DNS_MAX_IPLEN 64
 #define DNS_MAX_PATH 1024
 #define DEFAULT_DNS_PORT 53
+#define DEFAULT_DNS_TLS_PORT 853
 #define DNS_MAX_CONF_CNAME_LEN 128
 
 struct dns_servers {

src/dns_client.c

@@ -42,6 +42,8 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
+#include <openssl/ssl.h> 
+#include <openssl/err.h> 
 
 #define DNS_MAX_HOSTNAME 256
 #define DNS_MAX_EVENTS 64
@@ -73,6 +75,14 @@ struct dns_server_buff {
 	unsigned short len;
 };
 
+typedef enum dns_server_status {
+	DNS_SERVER_STATUS_INIT = 0,
+	DNS_SERVER_STATUS_CONNECTING,
+	DNS_SERVER_STATUS_CONNECTIONLESS,
+	DNS_SERVER_STATUS_CONNECTED,
+	DNS_SERVER_STATUS_DISCONNECTED,
+} dns_server_status;
+
 /* dns server information */
 struct dns_server_info {
 	struct list_head list;
@@ -84,6 +94,9 @@ struct dns_server_info {
 
 	/* client socket */
 	int fd;
+	SSL *ssl;
+	SSL_CTX *ssl_ctx;
+	dns_server_status status;
 
 	struct dns_server_buff send_buff;
 	struct dns_server_buff recv_buff;
@@ -142,6 +155,7 @@ struct dns_query_struct {
 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)
 {
@@ -214,6 +228,7 @@ int _dns_client_server_add(char *server_ip, struct addrinfo *gai, dns_server_typ
 	server_info->ai_addrlen = gai->ai_addrlen;
 	server_info->type = server_type;
 	server_info->fd = 0;
+	server_info->status = DNS_SERVER_STATUS_INIT;
 
 	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->ai_family);
@@ -253,9 +268,22 @@ static void _dns_client_close_socket(struct dns_server_info *server_info)
 	if (server_info->fd <= 0) {
 		return;
 	}
+
+	if (server_info->ssl) {
+		SSL_shutdown(server_info->ssl);
+		SSL_free(server_info->ssl);
+		server_info->ssl = NULL;
+	}
+
+	if (server_info->ssl_ctx) {
+		SSL_CTX_free(server_info->ssl_ctx);
+		server_info->ssl_ctx = NULL;
+	}
+
 	epoll_ctl(client.epoll_fd, EPOLL_CTL_DEL, server_info->fd, NULL);
 	close(server_info->fd);
 	server_info->fd = -1;
+	server_info->status = DNS_SERVER_STATUS_DISCONNECTED;
 }
 
 /* remove all servers information */
@@ -320,10 +348,17 @@ int _dns_client_server_operate(char *server_ip, int port, dns_server_type_t serv
 		return -1;
 	}
 
-	if (server_type == DNS_SERVER_UDP) {
+	switch (server_type) {
+	case DNS_SERVER_UDP:
 		sock_type = SOCK_DGRAM;
-	} else {
+		break;
+	case DNS_SERVER_TLS:
+	case DNS_SERVER_TCP:
 		sock_type = SOCK_STREAM;
+		break;
+	default:
+		return -1;
+		break;
 	}
 
 	/* get addr info */
@@ -641,6 +676,7 @@ static int _dns_client_create_socket_udp(struct dns_server_info *server_info)
 	}
 
 	server_info->fd = fd;
+	server_info->status = DNS_SERVER_STATUS_CONNECTIONLESS;
 
 	return 0;
 errout:
@@ -683,6 +719,7 @@ static int _DNS_client_create_socket_tcp(struct dns_server_info *server_info)
 	}
 
 	server_info->fd = fd;
+	server_info->status = DNS_SERVER_STATUS_CONNECTING;
 
 	return 0;
 errout:
@@ -693,12 +730,91 @@ errout:
 	return -1;
 }
 
+static int _DNS_client_create_socket_tls(struct dns_server_info *server_info)
+{
+	int fd = 0;
+	struct epoll_event event;
+	SSL_CTX *ctx = NULL;
+	SSL *ssl = NULL;
+
+	ctx = SSL_CTX_new(SSLv23_client_method());
+	if (ctx == NULL) {
+		tlog(TLOG_ERROR, "create ssl ctx failed.");
+		goto errout;
+	}
+
+	ssl = SSL_new(ctx);
+	if (ssl == NULL) {
+		tlog(TLOG_ERROR, "new ssl failed.");
+		goto errout;
+	}
+
+	fd = socket(server_info->ai_family, SOCK_STREAM, 0);
+	if (fd < 0) {
+		tlog(TLOG_ERROR, "create socket failed.");
+		goto errout;
+	}
+
+	if (set_fd_nonblock(fd, 1) != 0) {
+		tlog(TLOG_ERROR, "set socket non block failed, %s", strerror(errno));
+		goto errout;
+	}
+
+	if (connect(fd, (struct sockaddr *)&server_info->addr, server_info->ai_addrlen) != 0) {
+		if (errno != EINPROGRESS) {
+			tlog(TLOG_ERROR, "connect failed.");
+			goto errout;
+		}
+	}
+
+	if(SSL_set_fd(ssl, fd) == 0) {
+		tlog(TLOG_ERROR, "ssl set fd failed.");
+		goto errout;
+	}
+
+	memset(&event, 0, sizeof(event));
+	event.events = EPOLLIN | EPOLLOUT;
+	event.data.ptr = server_info;
+	if (epoll_ctl(client.epoll_fd, EPOLL_CTL_ADD, fd, &event) != 0) {
+		tlog(TLOG_ERROR, "epoll ctl failed.");
+		goto errout;
+	}
+
+	server_info->fd = fd;
+	server_info->ssl = ssl;
+	server_info->ssl_ctx = ctx;
+	server_info->status = DNS_SERVER_STATUS_CONNECTING;
+
+	tlog(TLOG_DEBUG, "TLS server connecting.\n");
+
+	return 0;
+errout:
+	if (fd > 0) {
+		close(fd);
+	}
+
+	if (ssl) {
+		SSL_free(ssl);
+	}
+
+	if (ctx) {
+		SSL_CTX_free(ctx);
+	}
+
+	return -1;
+}
+
 static int _dns_client_create_socket(struct dns_server_info *server_info)
 {
+	time(&server_info->last_send);
+	time(&server_info->last_recv);
+
 	if (server_info->type == DNS_SERVER_UDP) {
 		return _dns_client_create_socket_udp(server_info);
 	} else if (server_info->type == DNS_SERVER_TCP) {
 		return _DNS_client_create_socket_tcp(server_info);
+	} else if (server_info->type == DNS_SERVER_TLS) {
+		return _DNS_client_create_socket_tls(server_info);
 	} else {
 		return -1;
 	}
@@ -741,6 +857,10 @@ static int _dns_client_process_tcp(struct dns_server_info *server_info, struct e
 	/* when connected */
 	if (event->events & EPOLLOUT) {
 		struct epoll_event event;
+
+		if (server_info->status != DNS_SERVER_STATUS_CONNECTED) {
+			server_info->status = DNS_SERVER_STATUS_DISCONNECTED;
+		}
 		pthread_mutex_lock(&client.server_list_lock);
 		if (server_info->send_buff.len > 0) {
 			/* send data in send_buffer */
@@ -861,6 +981,279 @@ errout:
 	return -1;
 }
 
+static int _dns_client_socket_send(SSL *ssl, const void *buf, int num)
+{
+	int ret = 0;
+	int ssl_ret = 0;
+	unsigned long ssl_err = 0;
+
+	if (ssl == NULL) {
+		return -1;
+	}
+
+	ret = SSL_write(ssl, buf, num);
+	if (ret > 0) {
+		return ret;
+	}
+
+	ssl_ret = SSL_get_error(ssl, ret);
+	switch (ssl_ret) {
+	case SSL_ERROR_NONE:
+		errno = EAGAIN;
+		return -1;
+		break;
+	case SSL_ERROR_ZERO_RETURN:
+		return 0;
+		break;
+	case SSL_ERROR_WANT_READ:
+		errno = EAGAIN;
+		ret = -1;
+		break;
+	case SSL_ERROR_WANT_WRITE:
+		errno = EAGAIN;
+		ret = -1;
+		break;
+	case SSL_ERROR_SSL:
+		ssl_err = ERR_get_error();
+		if (ERR_GET_REASON(ssl_err) == SSL_R_UNINITIALIZED) {
+			errno = EAGAIN;
+			return -1;
+		}
+
+		tlog(TLOG_ERROR, "SSL write fail error no:  %s(%ld)\n", ERR_reason_error_string(ssl_err), ssl_err);
+		errno = EFAULT;
+		ret = -1;
+		break;
+	case SSL_ERROR_SYSCALL:
+		tlog(TLOG_ERROR, "SSL syscall failed, %s", strerror(errno));
+		return ret;
+	default:
+		errno = EFAULT;
+		ret = -1;
+		break;
+	}
+
+	return ret;
+}
+
+static int _dns_client_socket_recv(SSL *ssl, void *buf, int num)
+{
+	int ret = 0;
+	int ssl_ret = 0;
+	unsigned long ssl_err = 0;
+
+	ret = SSL_read(ssl, buf, num);
+	if (ret > 0) {
+		return ret;
+	}
+
+	ssl_ret = SSL_get_error(ssl, ret);
+	switch (ssl_ret) {
+	case SSL_ERROR_NONE:
+		errno = EAGAIN;
+		return -1;
+		break;
+	case SSL_ERROR_ZERO_RETURN:
+		return 0;
+		break;
+	case SSL_ERROR_WANT_READ:
+		errno = EAGAIN;
+		ret = -1;
+		break;
+	case SSL_ERROR_WANT_WRITE:
+		errno = EAGAIN;
+		ret = -1;
+		break;
+	case SSL_ERROR_SSL:
+		ssl_err = ERR_get_error();
+		if (ERR_GET_REASON(ssl_err) == SSL_R_UNINITIALIZED) {
+			errno = EAGAIN;
+			return -1;
+		}
+
+		tlog(TLOG_ERROR, "SSL read fail error no: %s(%ld)\n", ERR_reason_error_string(ssl_err), ssl_err);
+		errno = EFAULT;
+		ret = -1;
+		break;
+	case SSL_ERROR_SYSCALL:
+		tlog(TLOG_ERROR, "SSL syscall failed, %s", strerror(errno));
+		return ret;
+	default:
+		errno = EFAULT;
+		ret = -1;
+		break;
+	}
+
+	return ret;
+}
+
+static int _dns_client_process_tls(struct dns_server_info *server_info, struct epoll_event *event, unsigned long now)
+{
+	int len;
+	int ret = -1;
+	unsigned char *inpacket_data = server_info->recv_buff.data;
+	char from_host[DNS_MAX_CNAME_LEN];
+	struct epoll_event fd_event;
+	int ssl_ret;
+
+	if (server_info->status == DNS_SERVER_STATUS_CONNECTING) {
+		ret = SSL_connect(server_info->ssl);
+		if (ret == 0) {
+			goto errout;
+		} else if (ret < 0) {
+			memset(&fd_event, 0, sizeof(fd_event));
+			ssl_ret = SSL_get_error(server_info->ssl, ret);
+			if (ssl_ret == SSL_ERROR_WANT_READ) {
+				fd_event.events = EPOLLIN;
+			} else if (ssl_ret == SSL_ERROR_WANT_WRITE) {
+				fd_event.events = EPOLLOUT;
+			} else {
+				goto errout;
+			}
+
+			fd_event.data.ptr = server_info;
+			if (epoll_ctl(client.epoll_fd, EPOLL_CTL_MOD, server_info->fd, &fd_event) != 0) {
+				tlog(TLOG_ERROR, "epoll ctl failed.");
+				goto errout;
+			}
+
+			return 0;
+		}
+
+		tlog(TLOG_DEBUG, "TLS server connected.\n");
+		server_info->status = DNS_SERVER_STATUS_CONNECTED;
+		memset(&fd_event, 0, sizeof(fd_event));
+		fd_event.events = EPOLLIN | EPOLLOUT;
+		fd_event.data.ptr = server_info;
+		if (epoll_ctl(client.epoll_fd, EPOLL_CTL_MOD, server_info->fd, &fd_event) != 0) {
+			tlog(TLOG_ERROR, "epoll ctl failed.");
+			goto errout;
+		}
+
+	}
+
+	/* when connected */
+	if (event->events & EPOLLOUT) {
+		pthread_mutex_lock(&client.server_list_lock);
+		if (server_info->send_buff.len > 0) {
+			/* send data in send_buffer */
+			len = _dns_client_socket_send(server_info->ssl, server_info->send_buff.data, server_info->send_buff.len);
+			if (len < 0) {
+				pthread_mutex_unlock(&client.server_list_lock);
+				goto errout;
+			}
+
+			server_info->send_buff.len -= len;
+			if (server_info->send_buff.len > 0) {
+				memmove(server_info->send_buff.data, server_info->send_buff.data + len, server_info->send_buff.len);
+			}
+		}
+		pthread_mutex_unlock(&client.server_list_lock);
+
+		/* still remain data, retry */
+		if (server_info->send_buff.len > 0) {
+			return 0;
+		}
+
+		/* clear epllout event */
+		memset(&fd_event, 0, sizeof(fd_event));
+		fd_event.events = EPOLLIN;
+		fd_event.data.ptr = server_info;
+		if (epoll_ctl(client.epoll_fd, EPOLL_CTL_MOD, server_info->fd, &fd_event) != 0) {
+			tlog(TLOG_ERROR, "epoll ctl failed.");
+			return -1;
+		}
+
+		return 0;
+	}
+
+	/* receive from tcp */
+	len = _dns_client_socket_recv(server_info->ssl, server_info->recv_buff.data + server_info->recv_buff.len, DNS_TCP_BUFFER - server_info->recv_buff.len);
+	if (len < 0) {
+		/* no data to recv, try again */
+		if (errno == EAGAIN) {
+			return 0;
+		}
+		
+		/* FOR GFW */
+		if (errno == ECONNRESET) {
+			goto errout;
+		}
+
+		tlog(TLOG_ERROR, "recv failed, %s, %d\n", strerror(errno), errno);
+		goto errout;
+	}
+
+	/* peer server close */
+	if (len == 0) {
+		pthread_mutex_lock(&client.server_list_lock);
+		_dns_client_close_socket(server_info);
+		server_info->recv_buff.len = 0;
+		if (server_info->send_buff.len > 0) {
+			/* still remain request data, reconnect and send*/
+			ret = _dns_client_create_socket(server_info);
+		} else {
+			ret = 0;
+		}
+		pthread_mutex_unlock(&client.server_list_lock);
+		tlog(TLOG_DEBUG, "peer close, left = %d", server_info->send_buff.len);
+		return ret;
+	}
+
+	time(&server_info->last_recv);
+
+	server_info->recv_buff.len += len;
+	if (server_info->recv_buff.len < 2) {
+		/* wait and recv */
+		return 0;
+	}
+
+	while (1) {
+		/* tcp result format 
+	 	 * | len (short) | dns query result | 
+	 	 */
+		inpacket_data = server_info->recv_buff.data;
+		len = ntohs(*((unsigned short *)(inpacket_data)));
+		if (len <= 0 || len >= DNS_IN_PACKSIZE) {
+			/* data len is invalid */
+			goto errout;
+		}
+
+		if (len > server_info->recv_buff.len - 2) {
+			/* len is not expceded, wait and recv */
+			break;
+		}
+
+		inpacket_data = server_info->recv_buff.data + 2;
+		tlog(TLOG_DEBUG, "recv tcp from %s, len = %d", gethost_by_addr(from_host, (struct sockaddr *)&server_info->addr, server_info->ai_addrlen), len);
+
+		/* process result */
+		if (_dns_client_recv(inpacket_data, len, &server_info->addr, server_info->ai_addrlen) != 0) {
+			goto errout;
+		}
+		len += 2;
+		server_info->recv_buff.len -= len;
+
+		/* move to next result */
+		if (server_info->recv_buff.len > 0) {
+			memmove(server_info->recv_buff.data, server_info->recv_buff.data + len, server_info->recv_buff.len);
+		} else {
+			break;
+		}
+	}
+
+	return 0;
+
+errout:
+	pthread_mutex_lock(&client.server_list_lock);
+	server_info->recv_buff.len = 0;
+	server_info->send_buff.len = 0;
+	_dns_client_close_socket(server_info);
+	pthread_mutex_unlock(&client.server_list_lock);
+
+	return -1;
+}
+
 static int _dns_client_process(struct dns_server_info *server_info, struct epoll_event *event, unsigned long now)
 {
 	if (server_info->type == DNS_SERVER_UDP) {
@@ -869,6 +1262,9 @@ static int _dns_client_process(struct dns_server_info *server_info, struct epoll
 	} else if (server_info->type == DNS_SERVER_TCP) {
 		/* receive from tcp */
 		return _dns_client_process_tcp(server_info, event, now);
+	} else if (server_info->type == DNS_SERVER_TLS) {
+		/* recive from tls */
+		return _dns_client_process_tls(server_info, event, now);
 	} else {
 		return -1;
 	}
@@ -981,6 +1377,34 @@ static int _dns_client_send_tcp(struct dns_server_info *server_info, void *packe
 	return 0;
 }
 
+static int _dns_client_send_tls(struct dns_server_info *server_info, void *packet, unsigned short len)
+{
+	int send_len = 0;
+	unsigned char inpacket_data[DNS_IN_PACKSIZE];
+	unsigned char *inpacket = inpacket_data;
+
+	/* TCP query format
+	 * | len (short) | dns query data | 
+	 */
+	*((unsigned short *)(inpacket)) = htons(len);
+	memcpy(inpacket + 2, packet, len);
+	len += 2;
+
+	send_len = _dns_client_socket_send(server_info->ssl, inpacket, len);
+	if (send_len < 0) {
+		if (errno == EAGAIN || server_info->ssl == NULL) {
+			/* save data to buffer, and retry when EPOLLOUT is available */
+			return _dns_client_send_data_to_buffer(server_info, inpacket, len);
+		}
+		return -1;
+	} else if (send_len < len) {
+		/* save remain data to buffer, and retry when EPOLLOUT is available */
+		return _dns_client_send_data_to_buffer(server_info, inpacket + send_len, len - send_len);
+	}
+
+	return 0;
+}
+
 static int _dns_client_send_packet(struct dns_query_struct *query, void *packet, int len)
 {
 	struct dns_server_info *server_info, *tmp;
@@ -1012,6 +1436,11 @@ static int _dns_client_send_packet(struct dns_query_struct *query, void *packet,
 			ret = _dns_client_send_tcp(server_info, packet, len);
 			send_err = errno;
 			break;
+		case DNS_SERVER_TLS:
+			/* tls query */
+			ret = _dns_client_send_tls(server_info, packet, len);
+			send_err = errno;
+			break;
 		default:
 			/* unsupport query type */
 			ret = -1;

src/dns_client.h

@@ -6,7 +6,7 @@
 typedef enum {
 	DNS_SERVER_UDP,
 	DNS_SERVER_TCP,
-	DNS_SERVER_HTTP,
+	DNS_SERVER_TLS,
 	DNS_SERVER_TYPE_END,
 } dns_server_type_t;
 

src/dns_server.c

@@ -1332,7 +1332,8 @@ int dns_server_socket(void)
 
 	fd = socket(gai->ai_family, gai->ai_socktype, gai->ai_protocol);
 	if (fd < 0) {
-		tlog(TLOG_ERROR, "create socket failed.\n");
+		tlog(TLOG_ERROR, "create socket failed, family = %d, type = %d, proto = %d, %s\n", 
+			gai->ai_family, gai->ai_socktype, gai->ai_protocol, strerror(errno));
 		goto errout;
 	}
 

src/smartdns.c

@@ -37,6 +37,8 @@
 #include <string.h>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <openssl/ssl.h>
+#include <openssl/err.h>
 
 #define RESOLVE_FILE "/etc/resolv.conf"
 #define MAX_LINE_LEN 1024
@@ -175,6 +177,23 @@ errout:
 	return -1;
 }
 
+int smartdns_init_ssl(void)
+{
+	SSL_load_error_strings();
+	SSL_library_init();
+	OpenSSL_add_all_algorithms();
+
+	return 0;
+}
+
+int smartdns_destroy_ssl(void)
+{
+	ERR_free_strings();
+	EVP_cleanup();
+
+	return 0;
+}
+
 int smartdns_init(void)
 {
 	int ret;
@@ -198,9 +217,14 @@ int smartdns_init(void)
 		goto errout;
 	}
 
-	/* tlog_setlogscreen(1); */ 
+	//tlog_setlogscreen(1); 
 	tlog_setlevel(dns_conf_log_level);
 
+	if (smartdns_init_ssl() != 0) {
+		tlog(TLOG_ERROR, "init ssl failed.");
+		goto errout;
+	}
+
 	if (dns_conf_server_num <= 0) {
 		if (smartdns_load_from_resolv() != 0) {
 			tlog(TLOG_ERROR, "load dns from resolv failed.");
@@ -247,6 +271,7 @@ void smartdns_exit(void)
 	dns_server_exit();
 	dns_client_exit();
 	fast_ping_exit();
+	smartdns_destroy_ssl();
 	tlog_exit();
 	load_exit();
 }

src/tlog.c

@@ -1,9 +1,11 @@
 /*
  * tinylog 
- * Copyright (C) 2018 Ruilin Peng (Nick) <pymumu@gmail.com> 
+ * Copyright (C) 2018 Nick Peng <pymumu@gmail.com> 
  * https://github.com/pymumu/tinylog
  */
+#ifndef _GNU_SOURCE
 #define _GNU_SOURCE 
+#endif
 #include "tlog.h"
 #include <dirent.h>
 #include <errno.h>