Implemented TCP forward function (can be used with SSH proxycommand)

src/client.c

@@ -29,6 +29,7 @@
 #include <zlib.h>
 #include <sys/time.h>
 #include <time.h>
+#include <errno.h>
 
 #ifdef WINDOWS32
 #include "windows.h"
@@ -201,7 +202,7 @@ update_server_timeout(int handshake)
 
 	if (handshake) {
 		/* Send ping handshake to set server timeout */
-		return send_ping(1, -1, 1);
+		return send_ping(1, -1, 1, 0);
 	}
 	return -1;
 }
@@ -447,7 +448,7 @@ send_packet(char cmd, const uint8_t *data, const size_t datalen)
 }
 
 int
-send_ping(int ping_response, int ack, int set_timeout)
+send_ping(int ping_response, int ack, int set_timeout, int disconnect)
 {
 	this.num_pings++;
 	if (this.conn == CONN_DNS_NULL) {
@@ -468,14 +469,16 @@ send_ping(int ping_response, int ack, int set_timeout)
 		*(uint16_t *) (data + 7) = htons(this.downstream_timeout_ms);
 
 		/* update server frag/lazy timeout, ack flag, respond with ping flag */
-		data[9] = ((set_timeout & 1) << 4) | ((set_timeout & 1) << 3) | ((ack < 0 ? 0 : 1) << 2) | (ping_response & 1);
+		data[9] = ((disconnect & 1) << 5) | ((set_timeout & 1) << 4) |
+			((set_timeout & 1) << 3) | ((ack < 0 ? 0 : 1) << 2) | (ping_response & 1);
 		data[10] = (this.rand_seed >> 8) & 0xff;
 		data[11] = (this.rand_seed >> 0) & 0xff;
 		this.rand_seed += 1;
 
-		DEBUG(3, " SEND PING: respond %d, ack %d, %s(server %ld ms, downfrag %ld ms), flags %02X",
-				ping_response, ack, set_timeout ? "SET " : "", this.server_timeout_ms,
-				this.downstream_timeout_ms, data[8]);
+		DEBUG(3, " SEND PING: %srespond %d, ack %d, %s(server %ld ms, downfrag %ld ms), flags %02X, wup %u, wdn %u",
+				disconnect ? "DISCONNECT! " : "", ping_response, ack, set_timeout ? "SET " : "",
+				this.server_timeout_ms, this.downstream_timeout_ms,
+				data[8], this.outbuf->windowsize, this.inbuf->windowsize);
 
 		id = send_packet('p', data, sizeof(data));
 
@@ -505,7 +508,7 @@ send_next_frag()
 		if (this.outbuf->numitems > 0) {
 			/* There is stuff to send but we're out of sync, so send a ping
 			 * to get things back in order and keep the packets flowing */
-			send_ping(1, this.next_downstream_ack, 1);
+			send_ping(1, this.next_downstream_ack, 1, 0);
 			this.next_downstream_ack = -1;
 			window_tick(this.outbuf);
 		}
@@ -889,11 +892,11 @@ handshake_waitdns(char *buf, size_t buflen, char cmd, int timeout)
 }
 
 int
-parse_data(uint8_t *data, size_t len, fragment *f, int *immediate)
+parse_data(uint8_t *data, size_t len, fragment *f, int *immediate, int *ping)
 {
 	size_t headerlen = DOWNSTREAM_HDR;
-	int ping;
 	memset(f, 0, sizeof(fragment));
+	int error;
 
 	f->seqID = data[0];
 
@@ -902,12 +905,13 @@ parse_data(uint8_t *data, size_t len, fragment *f, int *immediate)
 	f->start = (data[2] >> 1) & 1;
 	f->compressed = (data[2] >> 2) & 1;
 	f->ack_other = (data[2] >> 3) & 1 ? data[1] : -1;
-	ping = (data[2] >> 4) & 1;
+	if (ping) *ping = (data[2] >> 4) & 1;
+	error = (data[2] >> 6) & 1;
 
 	if (immediate)
 		*immediate = (data[2] >> 5) & 1;
 
-	if (ping) { /* Handle ping stuff */
+	if (ping && *ping) { /* Handle ping stuff */
 		static unsigned dn_start_seq, up_start_seq, dn_wsize, up_wsize;
 
 		headerlen = DOWNSTREAM_PING_HDR;
@@ -924,7 +928,52 @@ parse_data(uint8_t *data, size_t len, fragment *f, int *immediate)
 	f->len = len - headerlen;
 	if (f->len > 0)
 		memcpy(f->data, data + headerlen, MIN(f->len, sizeof(f->data)));
-	return ping; /* return ping flag (if corresponding query was a ping) */
+	return error; /* return ping flag (if corresponding query was a ping) */
+}
+
+static ssize_t
+tunnel_stdin()
+{
+	size_t datalen;
+	uint8_t out[64*1024];
+	uint8_t in[64*1024];
+	uint8_t *data;
+	ssize_t readlen;
+
+	readlen = read(STDIN_FILENO, in, sizeof(in));
+	DEBUG(4, "  IN: %" L "d bytes on stdin, to be compressed: %d", readlen, this.compression_up);
+	if (readlen == 0) {
+		DEBUG(2, "EOF on stdin!");
+		return -1;
+	} else if (readlen < 0) {
+		warnx("Error %d reading from stdin: %s", errno, strerror(errno));
+		return -1;
+	}
+
+	if (this.conn != CONN_DNS_NULL || this.compression_up) {
+		datalen = sizeof(out);
+		compress2(out, &datalen, in, readlen, 9);
+		data = out;
+	} else {
+		datalen = readlen;
+		data = in;
+	}
+
+	if (this.conn == CONN_DNS_NULL) {
+		/* Check if outgoing buffer can hold data */
+		if (window_buffer_available(this.outbuf) < (datalen / MAX_FRAGSIZE) + 1) {
+			DEBUG(1, "  Outgoing buffer full (%" L "u/%" L "u), not adding data!",
+						this.outbuf->numitems, this.outbuf->length);
+			return -1;
+		}
+
+		window_add_outgoing_data(this.outbuf, data, datalen, this.compression_up);
+		/* Don't send anything here to respect min. send interval */
+	} else {
+		send_raw_data(data, datalen);
+	}
+
+	return datalen;
 }
 
 static int
@@ -974,7 +1023,7 @@ tunnel_dns()
 	size_t datalen, buflen;
 	uint8_t buf[64*1024], cbuf[64*1024], *data;
 	fragment f;
-	int read, compressed, res, immediate;
+	int read, compressed, ping, immediate, error;
 
 	memset(&q, 0, sizeof(q));
 	memset(buf, 0, sizeof(buf));
@@ -1060,27 +1109,35 @@ tunnel_dns()
 
 	this.num_recv++;
 
-	/* Decode the downstream data header and fragment-ify ready for processing */
-	res = parse_data(cbuf, read, &f, &immediate);
-
 	/* Mark query as received */
 	got_response(q.id, immediate, 0);
 
-	if ((this.debug >= 3 && res) || (this.debug >= 2 && !res))
+	/* Decode the downstream data header and fragment-ify ready for processing */
+	error = parse_data(cbuf, read, &f, &immediate, &ping);
+
+	if ((this.debug >= 3 && ping) || (this.debug >= 2 && !ping))
 		fprintf(stderr, " RX %s; frag ID %3u, ACK %3d, compression %d, datalen %" L "u, s%d e%d\n",
-				res ? "PING" : "DATA", f.seqID, f.ack_other, f.compressed, f.len, f.start, f.end);
+				ping ? "PING" : "DATA", f.seqID, f.ack_other, f.compressed, f.len, f.start, f.end);
 
 
 	window_ack(this.outbuf, f.ack_other);
 	window_tick(this.outbuf);
 
+	/* respond to TCP forwarding errors by shutting down */
+	if (error && this.use_remote_forward) {
+		f.data[f.len] = 0;
+		warnx("server: TCP forwarding error: %s", f.data);
+		this.running = 0;
+		return -1;
+	}
+
 	/* In lazy mode, we shouldn't get immediate replies to our most-recent
 	 query, only during heavy data transfer. Since this means the server
 	 doesn't have any packets to send, send one relatively fast (but not
 	 too fast, to avoid runaway ping-pong loops..) */
 	/* Don't send anything too soon; no data waiting from server */
 	if (f.len == 0) {
-		if (!res)
+		if (!ping)
 			DEBUG(1, "[WARNING] Received downstream data fragment with 0 length and NOT a ping!");
 		if (!this.lazymode)
 			this.send_ping_soon = 100;
@@ -1107,8 +1164,8 @@ tunnel_dns()
 	if (datalen > 0) {
 		if (compressed) {
 			buflen = sizeof(buf);
-			if ((res = uncompress(buf, &buflen, cbuf, datalen)) != Z_OK) {
-				DEBUG(1, "Uncompress failed (%d) for data len %" L "u: reassembled data corrupted or incomplete!", res, datalen);
+			if ((ping = uncompress(buf, &buflen, cbuf, datalen)) != Z_OK) {
+				DEBUG(1, "Uncompress failed (%d) for data len %" L "u: reassembled data corrupted or incomplete!", ping, datalen);
 				datalen = 0;
 			} else {
 				datalen = buflen;
@@ -1118,8 +1175,12 @@ tunnel_dns()
 			data = cbuf;
 		}
 
-		if (datalen)
-			write_tun(this.tun_fd, data, datalen);
+		if (datalen) {
+			if (this.use_remote_forward)
+				write(STDOUT_FILENO, data, datalen);
+			else
+				write_tun(this.tun_fd, data, datalen);
+		}
 	}
 
 	/* Move window along after doing all data processing */
@@ -1135,7 +1196,7 @@ client_tunnel()
 	fd_set fds;
 	int rv;
 	int i, use_min_send;
-	int sending, total;
+	int sending, total, maxfd;
 	time_t last_stats;
 	size_t sent_since_report, recv_since_report;
 
@@ -1191,7 +1252,7 @@ client_tunnel()
 					send_next_frag();
 				} else {
 					/* Send ping if we didn't send anything yet */
-					send_ping(0, this.next_downstream_ack, (this.num_pings > 20 && this.num_pings % 50 == 0));
+					send_ping(0, this.next_downstream_ack, (this.num_pings > 20 && this.num_pings % 50 == 0), 0);
 					this.next_downstream_ack = -1;
 				}
 
@@ -1260,12 +1321,20 @@ client_tunnel()
 		}
 
 		FD_ZERO(&fds);
-		if (this.conn != CONN_DNS_NULL || window_buffer_available(this.outbuf) > 16) {
+		maxfd = 0;
+		if (this.conn != CONN_DNS_NULL || window_buffer_available(this.outbuf) > 1) {
 			/* Fill up outgoing buffer with available data if it has enough space
 			 * The windowing protocol manages data retransmits, timeouts etc. */
-			FD_SET(this.tun_fd, &fds);
+			if (this.use_remote_forward) {
+				FD_SET(STDIN_FILENO, &fds);
+				maxfd = MAX(STDIN_FILENO, maxfd);
+			} else {
+				FD_SET(this.tun_fd, &fds);
+				maxfd = MAX(this.tun_fd, maxfd);
+			}
 		}
 		FD_SET(this.dns_fd, &fds);
+		maxfd = MAX(this.dns_fd, maxfd);
 
 		DEBUG(4, "Waiting %ld ms before sending more... (min_send %d)", timeval_to_ms(&tv), use_min_send);
 
@@ -1273,7 +1342,7 @@ client_tunnel()
 			gettimeofday(&now, NULL);
 		}
 
-		i = select(MAX(this.tun_fd, this.dns_fd) + 1, &fds, NULL, NULL, &tv);
+		i = select(maxfd + 1, &fds, NULL, NULL, &tv);
 
 		if (use_min_send && i > 0) {
 			/* enforce min_send_interval if we get interrupted by new tun data */
@@ -1299,7 +1368,7 @@ client_tunnel()
 		if (i == 0) {
 			/* timed out - no new packets recv'd */
 		} else {
-			if (FD_ISSET(this.tun_fd, &fds)) {
+			if (!this.use_remote_forward && FD_ISSET(this.tun_fd, &fds)) {
 				if (tunnel_tun() <= 0)
 					continue;
 				/* Returns -1 on error OR when quickly
@@ -1307,11 +1376,22 @@ client_tunnel()
 				   we need to _not_ do tunnel_dns() then.
 				   If chunk sent, sets this.send_ping_soon=0. */
 			}
+			if (this.use_remote_forward && FD_ISSET(STDIN_FILENO, &fds)) {
+				if (tunnel_stdin() <= 0) {
+					fprintf(stderr, "server: closing remote TCP forward connection\n");
+					/* send ping to disconnect, don't care if it comes back */
+					send_ping(0, 0, 0, 1);
+					this.running = 0;
+					break;
+				}
+			}
 
 			if (FD_ISSET(this.dns_fd, &fds)) {
 				tunnel_dns();
 			}
 		}
+		if (this.running == 0)
+			break;
 	}
 
 	return rv;
@@ -1369,6 +1449,7 @@ send_version(uint32_t version)
 
 static void
 send_login(char *login, int len)
+/* Send DNS login packet. See doc/proto_xxxxxxxx.txt for details */
 {
 	uint8_t flags = 0, data[100];
 	int length = 17, addrlen = 0;
@@ -1379,7 +1460,9 @@ send_login(char *login, int len)
 
 	memcpy(data + 1, login, 16);
 
-	if (this.remote_forward_addr.ss_family != AF_UNSPEC) {
+	/* if remote forward address is specified and not currently connecting */
+	if (this.remote_forward_connected != 2 &&
+		this.remote_forward_addr.ss_family != AF_UNSPEC) {
 		struct sockaddr_in6 *s6 = (struct sockaddr_in6 *) &this.remote_forward_addr;
 		struct sockaddr_in *s = (struct sockaddr_in *) &this.remote_forward_addr;
 
@@ -1405,6 +1488,10 @@ send_login(char *login, int len)
 		}
 		DEBUG(2, "Sending TCP forward login request: port %hu, length %d, addrlen %d",
 			  port, length, addrlen);
+	} else if (this.remote_forward_connected == 2) {
+		/* remote TCP forward connection in progress */
+		DEBUG(2, "Sending TCP forward login/poll request to check connection status.");
+		flags |= (1 << 4);
 	}
 
 	data[0] = flags;
@@ -1538,7 +1625,7 @@ static int
 handshake_login(int seed)
 {
 	char in[4096], login[16], server[65], client[65], flag;
-	int mtu, read;
+	int mtu, netmask, read, numwaiting = 0;
 
 	login_calculate(login, 16, this.password, seed);
 
@@ -1550,31 +1637,84 @@ handshake_login(int seed)
 		in[MIN(read, sizeof(in))] = 0; /* Null terminate */
 
 		if (read > 0) {
-			int netmask;
 			if (strncmp("LNAK", in, 4) == 0) {
 				fprintf(stderr, "Bad password\n");
 				return 1;
-			} else if (sscanf(in, "%c-%64[^-]-%64[^-]-%d-%d",
-				&flag, server, client, &mtu, &netmask) == 4) {
-
-				server[64] = 0;
-				client[64] = 0;
-				if (tun_setip(client, server, netmask) == 0 &&
-					tun_setmtu(mtu) == 0) {
-
-					fprintf(stderr, "Server tunnel IP is %s\n", server);
-					return 0;
-				} else {
-					errx(4, "Failed to set IP and MTU");
-				}
-			} else {
-				fprintf(stderr, "Received bad handshake: %.*s\n", read, in);
+				/* not reached */
 			}
+			flag = toupper(in[0]);
+
+			switch (flag) {
+				case 'I':
+					if (sscanf(in, "%c-%64[^-]-%64[^-]-%d-%d",
+								&flag, server, client, &mtu, &netmask) == 5) {
+
+						server[64] = 0;
+						client[64] = 0;
+						if (tun_setip(client, server, netmask) == 0 &&
+							tun_setmtu(mtu) == 0) {
+
+							fprintf(stderr, "Server tunnel IP is %s\n", server);
+							return 0;
+						} else {
+							errx(4, "Failed to set IP and MTU");
+						}
+					} else {
+						goto bad_handshake;
+					}
+					break;
+				case 'C':
+					if (!this.use_remote_forward) {
+						goto bad_handshake;
+					}
+
+					this.remote_forward_connected = 1;
+					fprintf(stderr, " done.");
+					return 0;
+				case 'W':
+					if (!this.use_remote_forward || this.remote_forward_connected == 1) {
+						goto bad_handshake;
+					}
+
+					this.remote_forward_connected = 2;
+
+					if (numwaiting == 0)
+						fprintf(stderr, "server: Opening Remote TCP forward.\n");
+					else
+						fprintf(stderr, "%.*s", numwaiting, "...............");
+
+					numwaiting ++;
+
+					/* wait a while before re-polling server, max 5 tries (14 seconds) */
+					if (numwaiting > 1)
+						sleep(numwaiting);
+
+					continue;
+				case 'E':
+					if (!this.use_remote_forward)
+						goto bad_handshake;
+
+					char errormsg[100];
+					strncpy(errormsg, in + 1, MIN(read, sizeof(errormsg)));
+					errormsg[99] = 0;
+					fprintf(stderr, "server: Remote TCP forward connection failed: %s\n", errormsg);
+					return 1;
+				default:
+					/* undefined flag */
+					bad_handshake:
+					fprintf(stderr, "Received bad handshake: %.*s\n", read, in);
+					break;
+			}
+
 		}
 
 		fprintf(stderr, "Retrying login...\n");
 	}
-	warnx("couldn't login to server");
+	if (numwaiting != 0)
+		warnx("Remote TCP forward connection timed out after 5 tries.");
+	else
+		warnx("couldn't login to server");
+
 	return 1;
 }
 
@@ -2424,7 +2564,7 @@ handshake_set_timeout()
 	for (int i = 0; this.running && i < 5; i++) {
 
 		id = this.autodetect_server_timeout ?
-			update_server_timeout(1) : send_ping(1, -1, 1);
+			update_server_timeout(1) : send_ping(1, -1, 1, 0);
 
 		read = handshake_waitdns(in, sizeof(in), 'P', i + 1);
 		got_response(id, 1, 0);
@@ -2464,13 +2604,11 @@ client_handshake()
 
 	fprintf(stderr, "Using DNS type %s queries\n", client_get_qtype());
 
-	r = handshake_version(&seed);
-	if (r) {
+	if ((r = handshake_version(&seed))) {
 		return r;
 	}
 
-	r = handshake_login(seed);
-	if (r) {
+	if ((r = handshake_login(seed))) {
 		return r;
 	}
 
@@ -2479,6 +2617,9 @@ client_handshake()
 		this.max_timeout_ms = 10000;
 		this.compression_down = 1;
 		this.compression_up = 1;
+		if (this.use_remote_forward)
+			fprintf(stderr, "Warning: Remote TCP forwards over Raw (UDP) mode may be unreliable.\n"
+				"         If forwarded connections are unstable, try using '-r' to force DNS tunnelling mode.\n");
 	} else {
 		if (this.raw_mode == 0) {
 			fprintf(stderr, "Skipping raw mode\n");

src/client.h

@@ -47,6 +47,7 @@ struct client_instance {
 	/* Remote TCP forwarding stuff (for -R) */
 	struct sockaddr_storage remote_forward_addr;
 	int use_remote_forward; /* 0 if no forwarding used */
+	int remote_forward_connected;
 
 	int tun_fd;
 	int dns_fd;
@@ -160,9 +161,9 @@ void client_set_hostname_maxlen(size_t i);
 int client_handshake();
 int client_tunnel();
 
-int parse_data(uint8_t *data, size_t len, fragment *f, int *immediate);
+int parse_data(uint8_t *data, size_t len, fragment *f, int *immediate, int*);
 int handshake_waitdns(char *buf, size_t buflen, char cmd, int timeout);
 void handshake_switch_options(int lazy, int compression, char denc);
-int send_ping(int ping_response, int ack, int timeout);
+int send_ping(int ping_response, int ack, int timeout, int);
 
 #endif

src/common.c

@@ -228,9 +228,15 @@ open_dns_from_host(char *host, int port, int addr_family, int flags)
 }
 
 void
-close_dns(int fd)
+close_socket(int fd)
 {
+	if (fd <= 0)
+		return;
+#ifdef WINDOWS32
+	closesocket(fd);
+#else
 	close(fd);
+#endif
 }
 
 void
@@ -411,7 +417,7 @@ socket_set_blocking(int fd, int blocking)
 	    return flags;
 	}
 
-	if (fcntl(fd, F_SETFL, blocking ? (flags | O_NONBLOCK) : (flags & (~O_NONBLOCK))) == -1)
+	if (fcntl(fd, F_SETFL, !blocking ? (flags | O_NONBLOCK) : (flags & (~O_NONBLOCK))) == -1)
 		return errno;
 
 #endif
@@ -442,11 +448,14 @@ open_tcp_nonblocking(struct sockaddr_storage *addr, char **errormsg)
 		return -1;
 	}
 
+	if (errormsg)
+		*errormsg = strerror(errno);
+
 	return fd;
 }
 
 int
-check_tcp_status(int fd, char **error)
+check_tcp_error(int fd, char **error)
 /* checks connected status of given socket.
  * returns error code. 0 if connected or EINPROGRESS if connecting */
 {

src/common.h

@@ -159,10 +159,10 @@ int get_addr(char *, int, int, int, struct sockaddr_storage *);
 int open_dns(struct sockaddr_storage *, size_t);
 int open_dns_opt(struct sockaddr_storage *sockaddr, size_t sockaddr_len, int v6only);
 int open_dns_from_host(char *host, int port, int addr_family, int flags);
-void close_dns(int);
+void close_socket(int);
 
 int open_tcp_nonblocking(struct sockaddr_storage *addr, char **error);
-int check_tcp_status(int fd, char **error);
+int check_tcp_error(int fd, char **error);
 
 void do_chroot(char *);
 void do_setcon(char *);

src/iodine.c

@@ -304,23 +304,23 @@ version()
 }
 
 static int
-parse_tcp_forward_option()
+parse_tcp_forward_option(char *optstr)
 {
 	char *remote_port_str, *remote_host_str;
 	int retval;
 
-	if (strrchr(optarg, ':')) {
-		remote_port_str = strrchr(optarg, ':') + 1;
-		if (optarg[0] == '[') {
+	if (strrchr(optstr, ':')) {
+		remote_port_str = strrchr(optstr, ':') + 1;
+		if (optstr[0] == '[') {
 			/* IPv6 address enclosed in square brackets */
-			remote_host_str = optarg + 1;
+			remote_host_str = optstr + 1;
 			/* replace closing bracket with null terminator */
 			*strchr(remote_host_str, ']') = 0;
 			this.remote_forward_addr.ss_family = AF_INET6;
 			retval = inet_pton(AF_INET6, remote_host_str,
 							   &((struct sockaddr_in6 *) &this.remote_forward_addr)->sin6_addr);
 		} else {
-			remote_host_str = optarg;
+			remote_host_str = optstr;
 			/* replace separator with null terminator */
 			*strchr(remote_host_str, ':') = 0;
 			this.remote_forward_addr.ss_family = AF_INET;
@@ -328,14 +328,15 @@ parse_tcp_forward_option()
 							   &((struct sockaddr_in *) &this.remote_forward_addr)->sin_addr);
 		}
 	} else {
-		/* no address specified (use server localhost IPv4), optarg is port */
-		remote_port_str = optarg;
+		/* no address specified (use server localhost IPv4), optstr is port */
+		remote_port_str = optstr;
 		this.remote_forward_addr.ss_family = AF_INET;
-		((struct sockaddr_in *) &this.remote_forward_addr)->sin_addr.s_addr = INADDR_LOOPBACK;
+		((struct sockaddr_in *) &this.remote_forward_addr)->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+		retval = 1;
 	}
 
-	if (retval <= 0) {
-		errx(12, "Invalid remote forward address (-R)! Must be [host:]port,\n"
+	if (!retval) {
+		warnx("Invalid remote forward address (-R)! Must be [host:]port,\n"
 			"where IPv6 addresses are enclosed in literal square brackets [].");
 		usage();
 		/* not reached */
@@ -351,10 +352,10 @@ parse_tcp_forward_option()
 
 	if (this.remote_forward_addr.ss_family == AF_INET) {
 		/* set port as sockaddr_in (IPv4) */
-		((struct sockaddr_in *) &this.remote_forward_addr)->sin_port = port;
+		((struct sockaddr_in *) &this.remote_forward_addr)->sin_port = htons(port);
 	} else {
 		/* set port in IPv6 sockaddr */
-		((struct sockaddr_in6 *) &this.remote_forward_addr)->sin6_port = port;
+		((struct sockaddr_in6 *) &this.remote_forward_addr)->sin6_port = htons(port);
 	}
 	return port;
 }
@@ -510,7 +511,7 @@ main(int argc, char **argv)
 			/* Argument format: [host:]port */
 			if (!optarg) break;
 			this.use_remote_forward = 1;
-			remote_forward_port = parse_tcp_forward_option();
+			remote_forward_port = parse_tcp_forward_option(optarg);
 			break;
 		case OPT_NODROP:
 			// TODO implement TCP-over-tun optimisations
@@ -711,13 +712,16 @@ main(int argc, char **argv)
 			read_password(this.password, sizeof(this.password));
 	}
 
-	if ((this.tun_fd = open_tun(device)) == -1) {
-		retval = 1;
-		goto cleanup1;
+	if (!this.use_remote_forward) {
+		if ((this.tun_fd = open_tun(device)) == -1) {
+			retval = 1;
+			goto cleanup;
+		}
 	}
+
 	if ((this.dns_fd = open_dns_from_host(NULL, 0, nameservaddr.ss_family, AI_PASSIVE)) < 0) {
 		retval = 1;
-		goto cleanup2;
+		goto cleanup;
 	}
 #ifdef OPENBSD
 	if (rtable > 0)
@@ -739,7 +743,7 @@ main(int argc, char **argv)
 
 	if (client_handshake()) {
 		retval = 1;
-		goto cleanup2;
+		goto cleanup;
 	}
 
 	if (this.conn == CONN_RAW_UDP) {
@@ -774,10 +778,14 @@ main(int argc, char **argv)
 
 	client_tunnel();
 
-cleanup2:
-	close_dns(this.dns_fd);
-	close_tun(this.tun_fd);
-cleanup1:
+cleanup:
+	if (this.use_remote_forward)
+		close(STDOUT_FILENO);
+	close_socket(this.dns_fd);
+	close_socket(this.tun_fd);
+#ifdef WINDOWS32
+	WSACleanup();
+#endif
 
 	return retval;
 }

src/iodined.c

@@ -636,13 +636,15 @@ main(int argc, char **argv)
 	server_tunnel();
 
 	syslog(LOG_INFO, "stopping");
-	close_dns(server.bind_fd);
+	close_socket(server.bind_fd);
 cleanup:
-	if (server.dns_fds.v6fd >= 0)
-		close_dns(server.dns_fds.v6fd);
-	if (server.dns_fds.v4fd >= 0)
-		close_dns(server.dns_fds.v4fd);
-	close_tun(server.tun_fd);
+	close_socket(server.dns_fds.v6fd);
+	close_socket(server.dns_fds.v4fd);
+	close_socket(server.tun_fd);
+#ifdef WINDOWS32
+	WSACleanup();
+#endif
+	/* TODO close user TCP forward sockets */
 
 	return retval;
 }

src/server.c

@@ -318,7 +318,7 @@ qmem_max_wait(int *touser, struct query **sendq)
 				QMEM_DEBUG(4, userid, "ANSWER q id %d, ACK %d; sent %" L "u of %" L "u + sending another %" L "u",
 						q->id, u->next_upstream_ack, sent, total, sending);
 
-				send_data_or_ping(userid, q, 0, immediate);
+				send_data_or_ping(userid, q, 0, immediate, NULL);
 
 				if (sending > 0)
 					sending--;
@@ -428,14 +428,15 @@ send_version_response(int fd, version_ack_t ack, uint32_t payload, int userid, s
 }
 
 void
-send_data_or_ping(int userid, struct query *q, int ping, int immediate)
+send_data_or_ping(int userid, struct query *q, int ping, int immediate, char *tcperror)
 /* Sends current fragment to user, or a ping if no data available.
    ping: 1=force send ping (even if data available), 0=only send if no data.
-   immediate: 1=not from qmem (ie. fresh query), 0=query is from qmem */
+   immediate: 1=not from qmem (ie. fresh query), 0=query is from qmem
+   disconnect: whether to tell user that TCP socket is closed (NULL if OK or pointer to error message) */
 {
 	uint8_t pkt[MAX_FRAGSIZE + DOWNSTREAM_PING_HDR];
 	size_t datalen, headerlen;
-	fragment *f;
+	fragment *f = NULL;
 	struct frag_buffer *out, *in;
 
 	in = users[userid].incoming;
@@ -443,7 +444,21 @@ send_data_or_ping(int userid, struct query *q, int ping, int immediate)
 
 	window_tick(out);
 
-	f = window_get_next_sending_fragment(out, &users[userid].next_upstream_ack);
+	if (!tcperror) {
+		f = window_get_next_sending_fragment(out, &users[userid].next_upstream_ack);
+	} else {
+		/* construct fake fragment containing error message. */
+		fragment fr;
+		f = &fr;
+		memset(f, 0, sizeof(fragment));
+		f->ack_other = -1;
+		f->len = strlen(tcperror);
+		memcpy(f->data, tcperror, f->len);
+		f->data[f->len] = 0;
+		f->start = 1;
+		f->end = 1;
+		DEBUG(2, "Sending ping with TCP forward disconnect; error: %s", f->data);
+	}
 
 	/* Build downstream data/ping header (see doc/proto_xxxxxxxx.txt) for details */
 	if (!f) {
@@ -464,6 +479,8 @@ send_data_or_ping(int userid, struct query *q, int ping, int immediate)
 
 	/* If this is being responded to immediately (ie. not from qmem) */
 	pkt[2] |= (immediate & 1) << 5;
+	if (tcperror)
+		pkt[2] |= (1 << 6);
 
 	if (ping) {
 		/* set ping flag and build extra header */
@@ -556,6 +573,23 @@ user_send_data(int userid, uint8_t *indata, size_t len, int compressed)
 	return ret;
 }
 
+static int
+user_send_tcp_disconnect(int userid, struct query *q, char *errormsg)
+/* tell user that TCP socket has been disconnected */
+{
+	users[userid].remote_forward_connected = -1;
+	close_socket(users[userid].remote_tcp_fd);
+	if (q == NULL)
+		q = qmem_get_next_response(userid);
+	if (q != NULL) {
+		send_data_or_ping(userid, q, 1, 0, errormsg);
+		users[userid].active = 0;
+		return 1;
+	}
+	users[userid].active = 0;
+	return 0;
+}
+
 static int
 tunnel_bind()
 {
@@ -597,6 +631,37 @@ tunnel_bind()
 	return 0;
 }
 
+static ssize_t
+tunnel_tcp(int userid)
+{
+	ssize_t len;
+	uint8_t buf[64*1024];
+	char *errormsg = NULL;
+
+	if (users[userid].remote_forward_connected != 1) {
+		DEBUG(2, "tunnel_tcp: user %d TCP socket not connected!", userid);
+		return 0;
+	}
+
+	len = read(users[userid].remote_tcp_fd, buf, sizeof(buf));
+
+	DEBUG(5, "read %ld bytes on TCP", len);
+	if (len == 0) {
+		DEBUG(1, "EOF on TCP forward for user %d; closing connection.", userid);
+		errormsg = "Connection closed by remote host.";
+		user_send_tcp_disconnect(userid, NULL, errormsg);
+		return -1;
+	} else if (len < 0) {
+		errormsg = strerror(errno);
+		DEBUG(1, "Error %d on TCP forward for user %d: %s", errno, userid, errormsg);
+		user_send_tcp_disconnect(userid, NULL, errormsg);
+		return -1;
+	}
+
+	user_send_data(userid, buf, (size_t) len, 0);
+	return len;
+}
+
 static int
 tunnel_tun()
 {
@@ -696,7 +761,7 @@ int
 server_tunnel()
 {
 	struct timeval tv;
-	fd_set fds;
+	fd_set read_fds, write_fds;
 	int i;
 	int userid;
 	struct query *answer_now = NULL;
@@ -710,31 +775,38 @@ server_tunnel()
 		/* max wait time based on pending queries */
 		tv = qmem_max_wait(&userid, &answer_now);
 
-		FD_ZERO(&fds);
+		FD_ZERO(&read_fds);
+		FD_ZERO(&write_fds);
 		maxfd = 0;
 
 		if (server.dns_fds.v4fd >= 0) {
-			FD_SET(server.dns_fds.v4fd, &fds);
+			FD_SET(server.dns_fds.v4fd, &read_fds);
 			maxfd = MAX(server.dns_fds.v4fd, maxfd);
 		}
 		if (server.dns_fds.v6fd >= 0) {
-			FD_SET(server.dns_fds.v6fd, &fds);
+			FD_SET(server.dns_fds.v6fd, &read_fds);
 			maxfd = MAX(server.dns_fds.v6fd, maxfd);
 		}
 
 		if (server.bind_fd) {
 			/* wait for replies from real DNS */
-			FD_SET(server.bind_fd, &fds);
+			FD_SET(server.bind_fd, &read_fds);
 			maxfd = MAX(server.bind_fd, maxfd);
 		}
 
 		/* Don't read from tun if all users have filled outpacket queues */
 		if(!all_users_waiting_to_send()) {
-			FD_SET(server.tun_fd, &fds);
+			FD_SET(server.tun_fd, &read_fds);
 			maxfd = MAX(server.tun_fd, maxfd);
 		}
 
-		i = select(maxfd + 1, &fds, NULL, NULL, &tv);
+		/* add connected user TCP forward FDs to read set */
+		maxfd = MAX(set_user_tcp_fds(&read_fds, 1), maxfd);
+
+		/* add connectING user TCP FDs to write set */
+		maxfd = MAX(set_user_tcp_fds(&write_fds, 2), maxfd);
+
+		i = select(maxfd + 1, &read_fds, &write_fds, NULL, &tv);
 
 		if(i < 0) {
 			if (server.running)
@@ -757,16 +829,29 @@ server_tunnel()
 				}
 			}
 		} else {
-			if (FD_ISSET(server.tun_fd, &fds)) {
+			if (FD_ISSET(server.tun_fd, &read_fds)) {
 				tunnel_tun();
 			}
-			if (FD_ISSET(server.dns_fds.v4fd, &fds)) {
+
+			for (userid = 0; userid < created_users; userid++) {
+				if (FD_ISSET(users[userid].remote_tcp_fd, &read_fds) && users[userid].remoteforward_addr_len > 0) {
+					DEBUG(4, "tunnel_tcp called for user %d", userid);
+					tunnel_tcp(userid);
+				} else if (users[userid].remote_forward_connected == 2 &&
+					FD_ISSET(users[userid].remote_tcp_fd, &write_fds)) {
+					DEBUG(2, "User %d TCP socket now writable (connection established)", userid);
+					users[userid].remote_forward_connected = 1;
+				}
+			}
+
+			if (FD_ISSET(server.dns_fds.v4fd, &read_fds)) {
 				tunnel_dns(server.dns_fds.v4fd);
 			}
-			if (FD_ISSET(server.dns_fds.v6fd, &fds)) {
+			if (FD_ISSET(server.dns_fds.v6fd, &read_fds)) {
 				tunnel_dns(server.dns_fds.v6fd);
 			}
-			if (FD_ISSET(server.bind_fd, &fds)) {
+
+			if (FD_ISSET(server.bind_fd, &read_fds)) {
 				tunnel_bind();
 			}
 		}
@@ -781,7 +866,7 @@ handle_full_packet(int userid, uint8_t *data, size_t len, int compressed)
 	size_t rawlen;
 	uint8_t out[64*1024], *rawdata;
 	struct ip *hdr;
-	int touser;
+	int touser = -1;
 	int ret;
 
 	/* Check if data needs to be uncompressed */
@@ -796,20 +881,28 @@ handle_full_packet(int userid, uint8_t *data, size_t len, int compressed)
 	}
 
 	if (ret == Z_OK) {
-		hdr = (struct ip*) (out + 4);
-		touser = find_user_by_ip(hdr->ip_dst.s_addr);
-		DEBUG(2, "FULL PKT: %" L "u bytes from user %d (touser %d)", len, userid, touser);
-		if (touser == -1) {
-			/* send the uncompressed packet to tun device */
-			write_tun(server.tun_fd, rawdata, rawlen);
-		} else {
-			/* don't re-compress if possible */
-			if (users[touser].down_compression && compressed) {
-				user_send_data(touser, data, len, 1);
+		if (users[userid].remoteforward_addr_len == 0) {
+			hdr = (struct ip*) (out + 4);
+			touser = find_user_by_ip(hdr->ip_dst.s_addr);
+			DEBUG(2, "FULL PKT: %" L "u bytes from user %d (touser %d)", len, userid, touser);
+			if (touser == -1) {
+				/* send the uncompressed packet to tun device */
+				write_tun(server.tun_fd, rawdata, rawlen);
 			} else {
-				user_send_data(touser, rawdata, rawlen, 0);
+				/* don't re-compress if possible */
+				if (users[touser].down_compression && compressed) {
+					user_send_data(touser, data, len, 1);
+				} else {
+					user_send_data(touser, rawdata, rawlen, 0);
+				}
+			}
+		} else {
+			/* Write full pkt to user's remote forward TCP stream */
+			if ((ret = write(users[userid].remote_tcp_fd, rawdata, rawlen)) != rawlen) {
+				DEBUG(2, "Write error %d on TCP socket for user %d: %s", errno, userid, strerror(errno));
 			}
 		}
+
 	} else {
 		DEBUG(2, "Discarded upstream data from user %d, uncompress() result: %d", userid, ret);
 	}
@@ -1170,6 +1263,7 @@ handle_dns_version(int dns_fd, struct query *q, uint8_t *domain, int domain_len)
 	u->hostlen = q->fromlen;
 	u->remote_forward_connected = 0;
 	u->remoteforward_addr_len = 0;
+	u->remote_tcp_fd = 0;
 	u->remoteforward_addr.ss_family = AF_UNSPEC;
 	u->fragsize = 100; /* very safe */
 	u->conn = CONN_DNS_NULL;
@@ -1250,7 +1344,7 @@ handle_dns_login(int dns_fd, struct query *q, uint8_t *domain, int domain_len, i
 {
 	uint8_t unpacked[512], flags;
 	char logindata[16], *tmp[2], out[512], *reason = NULL;
-	char *errormsg = NULL;
+	char *errormsg = NULL, fromaddr[100];
 	struct in_addr tempip;
 	char remote_tcp, remote_isnt_localhost, use_ipv6, poll_status; //, drop_packets;
 	int length = 17, read, addrlen, login_ok = 1;
@@ -1279,8 +1373,10 @@ handle_dns_login(int dns_fd, struct query *q, uint8_t *domain, int domain_len, i
 
 	CHECK_LEN(read, length);
 
+	strncpy(fromaddr, format_addr(&q->from, q->fromlen), 100);
+
 	DEBUG(2, "Received login request for user %d from %s",
-				userid, format_addr(&q->from, q->fromlen));
+				userid, fromaddr);
 
 	DEBUG(6, "Login: length=%d, flags=0x%02x, seed=0x%08x, hash=0x%016llx%016llx",
 			  length, flags, u->seed, *(unsigned long long *) (unpacked + 1),
@@ -1289,7 +1385,7 @@ handle_dns_login(int dns_fd, struct query *q, uint8_t *domain, int domain_len, i
 	if (check_user_and_ip(userid, q, server.check_ip) != 0) {
 		write_dns(dns_fd, q, "BADIP", 5, 'T');
 		syslog(LOG_WARNING, "rejected login request from user #%d from %s; expected source %s",
-			userid, format_addr(&q->from, q->fromlen), format_addr(&u->host, u->hostlen));
+			userid, fromaddr, format_addr(&u->host, u->hostlen));
 		DEBUG(1, "Rejected login request from user %d: BADIP", userid);
 		return;
 	}
@@ -1314,12 +1410,12 @@ handle_dns_login(int dns_fd, struct query *q, uint8_t *domain, int domain_len, i
 		if (addrlen > 0) {
 			if (use_ipv6) {
 				addr6->sin6_family = AF_INET6;
-				addr6->sin6_port = port;
+				addr6->sin6_port = htons(port);
 				u->remoteforward_addr_len = sizeof(*addr6);
 				memcpy(&addr6->sin6_addr, unpacked + 19, MIN(sizeof(*addr6), addrlen));
 			} else {
 				addr->sin_family = AF_INET;
-				addr->sin_port = port;
+				addr->sin_port = htons(port);
 				u->remoteforward_addr_len = sizeof(*addr);
 				memcpy(&addr->sin_addr, unpacked + 19, MIN(sizeof(*addr), addrlen));
 			}
@@ -1329,8 +1425,8 @@ handle_dns_login(int dns_fd, struct query *q, uint8_t *domain, int domain_len, i
 				  port, login_ok ? "allowed" : "rejected");
 		} else {
 			addr->sin_family = AF_INET;
-			addr->sin_port = port;
-			addr->sin_addr.s_addr = INADDR_LOOPBACK;
+			addr->sin_port = htons(port);
+			addr->sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 			DEBUG(1, "User %d requested TCP connection to localhost:%hu, %s.", userid,
 				  port, login_ok ? "allowed" : "rejected");
 		}
@@ -1347,12 +1443,11 @@ handle_dns_login(int dns_fd, struct query *q, uint8_t *domain, int domain_len, i
 		write_dns(dns_fd, q, "LNAK", 4, 'T');
 		if (--u->authenticated >= 0)
 			u->authenticated = -1;
-		char *src_ip = format_addr(&q->from, q->fromlen);
 		int tries = abs(u->authenticated);
 		DEBUG(1, "rejected login from user %d (%s), tries: %d, reason: %s",
-			  userid, src_ip, tries, reason);
+			  userid, fromaddr, tries, reason);
 		syslog(LOG_WARNING, "rejected login request from user #%d from %s, %s; incorrect attempts: %d",
-			userid, src_ip, reason, tries);
+			userid, fromaddr, reason, tries);
 		return;
 	}
 
@@ -1360,13 +1455,13 @@ handle_dns_login(int dns_fd, struct query *q, uint8_t *domain, int domain_len, i
 	u->authenticated++;
 	if (u->authenticated > 1 && !poll_status)
 		syslog(LOG_WARNING, "duplicate login request from user #%d from %s",
-			   userid, format_addr(&u->host, u->hostlen));
+			   userid, fromaddr);
 
 	if (remote_tcp) {
 		int tcp_fd;
 
 		DEBUG(1, "User %d connected from %s, starting TCP connection to %s.", userid,
-			  format_addr(&q->from, q->fromlen), format_addr(&u->remoteforward_addr, sizeof(struct sockaddr_storage)));
+			  fromaddr, format_addr(&u->remoteforward_addr, sizeof(struct sockaddr_storage)));
 		syslog(LOG_NOTICE, "accepted password from user #%d, connecting TCP forward", userid);
 
 		/* Open socket and connect to TCP forward host:port */
@@ -1377,28 +1472,38 @@ handle_dns_login(int dns_fd, struct query *q, uint8_t *domain, int domain_len, i
 			goto tcp_forward_error;
 		}
 
+		/* connection in progress */
 		out[0] = 'W';
 		read = 1;
 		write_dns(dns_fd, q, out, read + 1, u->downenc);
-		u->tcp_fd = tcp_fd;
+		u->remote_tcp_fd = tcp_fd;
+		u->remote_forward_connected = 2; /* connecting */
 		return;
 	} else if (poll_status) {
+		/* Check TCP forward connection status and update user data */
 		int retval;
 
-		if ((retval = check_tcp_status(u->tcp_fd, &errormsg)) == -1) {
-			goto tcp_forward_error;
+		/* Check for connection errors */
+		if ((retval = check_tcp_error(u->remote_tcp_fd, &errormsg)) != 0) {
+			/* if unacceptable error, tell user */
+			if (retval != EINPROGRESS)
+				goto tcp_forward_error;
 		}
 
+		if (retval == EINPROGRESS)
+			u->remote_forward_connected = 2;
+
 		read = 1;
 		out[1] = 0;
 
-		if (retval == 0) {
+		/* check user TCP forward status flag, which is updated in server_tunnel
+		 * when the file descriptor becomes writable (ie, connection established */
+		if (u->remote_forward_connected == 1) {
 			out[0] = 'C';
-			u->remote_forward_connected = 1;
-		} else if (retval == EINPROGRESS) {
+			DEBUG(2, "User %d TCP forward connection established: %s", userid, errormsg);
+		} else if (u->remote_forward_connected == 2) {
 			out[0] = 'W';
-		} else {
-			goto tcp_forward_error;
+			DEBUG(3, "User %d TCP connection in progress: %s", userid, errormsg);
 		}
 
 		write_dns(dns_fd, q, out, read + 1, u->downenc);
@@ -1412,11 +1517,11 @@ handle_dns_login(int dns_fd, struct query *q, uint8_t *domain, int domain_len, i
 		tempip.s_addr = u->tun_ip;
 		tmp[1] = strdup(inet_ntoa(tempip));
 
-		read = snprintf(out, sizeof(out) - 1, "-%s-%s-%d-%d",
+		read = snprintf(out + 1, sizeof(out) - 1, "-%s-%s-%d-%d",
 						tmp[0], tmp[1], server.mtu, server.netmask);
 
 		DEBUG(1, "User %d connected from %s, tun_ip %s.", userid,
-			  format_addr(&q->from, q->fromlen), tmp[1]);
+			  fromaddr, tmp[1]);
 		syslog(LOG_NOTICE, "accepted password from user #%d, given IP %s", userid, tmp[1]);
 
 		free(tmp[1]);
@@ -1618,7 +1723,7 @@ handle_dns_ping(int dns_fd, struct query *q, int userid,
 				uint8_t *unpacked, size_t read)
 {
 	int dn_seq, up_seq, dn_winsize, up_winsize, dn_ack;
-	int respond, set_qtimeout, set_wtimeout;
+	int respond, set_qtimeout, set_wtimeout, tcp_disconnect;
 	unsigned qtimeout_ms, wtimeout_ms;
 
 	CHECK_LEN(read, UPSTREAM_PING);
@@ -1628,23 +1733,36 @@ handle_dns_ping(int dns_fd, struct query *q, int userid,
 		return;
 
 	/* Unpack flags/options from ping header */
-	dn_ack = ((unpacked[10] >> 2) & 1) ? unpacked[1] : -1;
-	up_winsize = unpacked[2];
-	dn_winsize = unpacked[3];
-	up_seq = unpacked[4];
-	dn_seq = unpacked[5];
+	dn_ack = ((unpacked[9] >> 2) & 1) ? unpacked[0] : -1;
+	up_winsize = unpacked[1];
+	dn_winsize = unpacked[2];
+	up_seq = unpacked[3];
+	dn_seq = unpacked[4];
 
 	/* Query timeout and window frag timeout */
-	qtimeout_ms = ntohs(*(uint16_t *) (unpacked + 6));
-	wtimeout_ms = ntohs(*(uint16_t *) (unpacked + 8));
-	respond = unpacked[10] & 1;
-	set_qtimeout = (unpacked[10] >> 3) & 1;
-	set_wtimeout = (unpacked[10] >> 4) & 1;
+	qtimeout_ms = ntohs(*(uint16_t *) (unpacked + 5));
+	wtimeout_ms = ntohs(*(uint16_t *) (unpacked + 7));
+	respond = unpacked[9] & 1;
+	set_qtimeout = (unpacked[9] >> 3) & 1;
+	set_wtimeout = (unpacked[9] >> 4) & 1;
+	tcp_disconnect = (unpacked[9] >> 5) & 1;
 
-	DEBUG(3, "PING pkt user %d, down %d/%d, up %d/%d, ACK %d, %sqtime %u ms, %swtime %u ms, respond %d (flags %02X)",
+	DEBUG(3, "PING pkt user %d, down %d/%d, up %d/%d, ACK %d, %sqtime %u ms, "
+		  "%swtime %u ms, respond %d, tcp_close %d (flags %02X)",
 				userid, dn_seq, dn_winsize, up_seq, up_winsize, dn_ack,
 				set_qtimeout ? "SET " : "", qtimeout_ms, set_wtimeout ? "SET " : "",
-				wtimeout_ms, respond, unpacked[10]);
+				wtimeout_ms, respond, tcp_disconnect, unpacked[9]);
+
+	if (tcp_disconnect) {
+		/* close user's TCP forward connection and mark user as inactive */
+		if (users[userid].remoteforward_addr_len == 0) {
+			DEBUG(1, "User %d attempted TCP disconnect but didn't request TCP forwarding!", userid);
+		} else {
+			DEBUG(1, "User %d closed remote TCP forward", userid);
+			close_socket(users[userid].remote_tcp_fd);
+			users[userid].active = 0;
+		}
+	}
 
 	if (set_qtimeout) {
 		/* update user's query timeout if timeout flag set */
@@ -1671,7 +1789,7 @@ handle_dns_ping(int dns_fd, struct query *q, int userid,
 			  users[userid].outgoing->windowsize, dn_winsize, users[userid].incoming->windowsize, up_winsize);
 		users[userid].outgoing->windowsize = dn_winsize;
 		users[userid].incoming->windowsize = up_winsize;
-		send_data_or_ping(userid, q, 1, 1);
+		send_data_or_ping(userid, q, 1, 1, NULL);
 		return;
 	}
 
@@ -1682,7 +1800,7 @@ handle_dns_ping(int dns_fd, struct query *q, int userid,
 void
 handle_dns_data(int dns_fd, struct query *q, uint8_t *domain, int domain_len, int userid)
 {
-	uint8_t unpacked[512];
+	uint8_t unpacked[20];
 	static fragment f;
 	size_t len;
 

src/server.h

@@ -158,6 +158,6 @@ void handle_null_request(int dns_fd, struct query *q, int domain_len);
 void handle_ns_request(int dns_fd, struct query *q);
 void handle_a_request(int dns_fd, struct query *q, int fakeip);
 
-void send_data_or_ping(int, struct query *, int, int);
+void send_data_or_ping(int, struct query *, int, int, char*);
 
 #endif /* __SERVER_H__ */

src/tun.c

@@ -457,13 +457,6 @@ open_tun(const char *tun_device)
 
 #endif
 
-void
-close_tun(int tun_fd)
-{
-	if (tun_fd >= 0)
-		close(tun_fd);
-}
-
 #ifdef WINDOWS32
 int
 write_tun(int tun_fd, uint8_t *data, size_t len)

src/user.c

@@ -236,3 +236,19 @@ check_authenticated_user_and_ip(int userid, struct query *q, int check_ip)
 
 	return 0;
 }
+
+int
+set_user_tcp_fds(fd_set *fds, int conn_status)
+/* Add TCP forward FDs to fd_set for users with given connection status; returns largest FD added */
+{
+	int max_fd = 0;
+	for (int userid = 0; userid < created_users; userid ++) {
+		if (user_active(userid) && users[userid].remoteforward_addr_len > 0
+			&& users[userid].remote_forward_connected == conn_status) {
+			FD_SET(users[userid].remote_tcp_fd, fds);
+			max_fd = MAX(max_fd, users[userid].remote_tcp_fd);
+		}
+	}
+	return max_fd;
+}
+

src/user.h

@@ -37,8 +37,8 @@ struct tun_user {
 	socklen_t hostlen;
 	struct sockaddr_storage remoteforward_addr;
 	socklen_t remoteforward_addr_len; /* 0 if no remote forwarding enabled */
-	int tcp_fd;
-	int remote_forward_connected;
+	int remote_tcp_fd;
+	int remote_forward_connected; /* 0 if not connected, -1 if error or 1 if OK */
 	struct frag_buffer *incoming;
 	struct frag_buffer *outgoing;
 	int next_upstream_ack;
@@ -67,5 +67,6 @@ int find_user_by_ip(uint32_t);
 int find_available_user();
 void user_switch_codec(int userid, struct encoder *enc);
 void user_set_conn_type(int userid, enum connection c);
+int set_user_tcp_fds(fd_set *fds, int);
 
 #endif