├── AUTHORS ├── Changelog ├── LICENSE ├── Makefile ├── README └── simpletun.c /AUTHORS: -------------------------------------------------------------------------------- 1 | Send suggestions, bug reports, criticisms to Davide Brini 2 | -------------------------------------------------------------------------------- /Changelog: -------------------------------------------------------------------------------- 1 | 0.01 2 | ---- 3 | 4 | 01/09/2009 Changed the way packets are sent over TCP, now all kinds of frames/packets/protocols are supported. 5 | 27/03/2010 Some clean up and reformatting. 6 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /Makefile: -------------------------------------------------------------------------------- 1 | PREFIX=/usr 2 | BINDIR=$(PREFIX)/bin 3 | 4 | CC=gcc 5 | INSTALL=ginstall 6 | 7 | all: simpletun 8 | distclean: clean 9 | 10 | clean: 11 | rm simpletun 12 | 13 | 14 | install: all 15 | $(INSTALL) -D simpletun $(DESTDIR)$(BINDIR)/simpletun 16 | 17 | macmask: 18 | $(CC) simpletun.c -o simpletun 19 | -------------------------------------------------------------------------------- /README: -------------------------------------------------------------------------------- 1 | simpletun, a (too) simple tunnelling program. 2 | 3 | ------- 4 | 5 | To compile the program, just do 6 | 7 | $ gcc simpletun.c -o simpletun 8 | 9 | If you have GNU make, you can also exploit implicit targets and do 10 | 11 | $ make simpletun 12 | 13 | ------- 14 | 15 | Usage: 16 | simpletun -i [-s|-c ] [-p ] [-u|-a] [-d] 17 | simpletun -h 18 | 19 | -i : Name of interface to use (mandatory) 20 | -s|-c : run in server mode (-s), or specify server address (-c ) (mandatory) 21 | -p : port to listen on (if run in server mode) or to connect to (in client mode), default 55555 22 | -u|-a: use TUN (-u, default) or TAP (-a) 23 | -d: outputs debug information while running 24 | -h: prints this help text 25 | 26 | ------- 27 | 28 | Refer to http://backreference.org/2010/03/27/tuntap-interface-tutorial/ for 29 | more information on tun/tap interfaces in Linux in general, and on this 30 | program in particular. 31 | The program must be run at one end as a server, and as client at the other 32 | end. The tun/tap interface must already exist, be up and configured with an IP 33 | address, and owned by the user who runs simpletun. That user must also have 34 | read/write permission on /dev/net/tun. (Alternatively, you can run the 35 | program as root, and configure the transient interfaces manually before 36 | starting to exchange packets. This is not recommended) 37 | 38 | Use is straightforward. On one end just run 39 | 40 | [server]$ ./simpletun -i tun13 -s 41 | 42 | at the other end run 43 | 44 | [client]$ ./simpletun -i tun0 -c 10.2.3.4 45 | 46 | where 10.2.3.4 is the remote server's IP address, and tun13 and tun0 must be 47 | replaced with the names of the actual tun interfaces used on the computers. 48 | By default it assumes a tun device is being used (use -u to be explicit), and 49 | -a can be used to tell the program that the interface is tap. 50 | By default it uses TCP port 55555, but you can change that by using -p (the 51 | value you use must match on the client and the server, of course). Use -d to 52 | add some debug information. Press ctrl-c on either side to exit (the other end 53 | will exit too). 54 | 55 | The program is very limited, so expect to be disappointed. 56 | -------------------------------------------------------------------------------- /simpletun.c: -------------------------------------------------------------------------------- 1 | /************************************************************************** 2 | * simpletun.c * 3 | * * 4 | * A simplistic, simple-minded, naive tunnelling program using tun/tap * 5 | * interfaces and TCP. DO NOT USE THIS PROGRAM FOR SERIOUS PURPOSES. * 6 | * * 7 | * You have been warned. * 8 | * * 9 | * (C) 2010 Davide Brini. * 10 | * * 11 | * DISCLAIMER AND WARNING: this is all work in progress. The code is * 12 | * ugly, the algorithms are naive, error checking and input validation * 13 | * are very basic, and of course there can be bugs. If that's not enough, * 14 | * the program has not been thoroughly tested, so it might even fail at * 15 | * the few simple things it should be supposed to do right. * 16 | * Needless to say, I take no responsibility whatsoever for what the * 17 | * program might do. The program has been written mostly for learning * 18 | * purposes, and can be used in the hope that is useful, but everything * 19 | * is to be taken "as is" and without any kind of warranty, implicit or * 20 | * explicit. See the file LICENSE for further details. * 21 | *************************************************************************/ 22 | 23 | #include 24 | #include 25 | #include 26 | #include 27 | #include 28 | #include 29 | #include 30 | #include 31 | #include 32 | #include 33 | #include 34 | #include 35 | #include 36 | #include 37 | #include 38 | #include 39 | 40 | /* buffer for reading from tun/tap interface, must be >= 1500 */ 41 | #define BUFSIZE 2000 42 | #define CLIENT 0 43 | #define SERVER 1 44 | #define PORT 55555 45 | 46 | int debug; 47 | char *progname; 48 | 49 | /************************************************************************** 50 | * tun_alloc: allocates or reconnects to a tun/tap device. The caller * 51 | * must reserve enough space in *dev. * 52 | **************************************************************************/ 53 | int tun_alloc(char *dev, int flags) { 54 | 55 | struct ifreq ifr; 56 | int fd, err; 57 | char *clonedev = "/dev/net/tun"; 58 | 59 | if( (fd = open(clonedev , O_RDWR)) < 0 ) { 60 | perror("Opening /dev/net/tun"); 61 | return fd; 62 | } 63 | 64 | memset(&ifr, 0, sizeof(ifr)); 65 | 66 | ifr.ifr_flags = flags; 67 | 68 | if (*dev) { 69 | strncpy(ifr.ifr_name, dev, IFNAMSIZ); 70 | } 71 | 72 | if( (err = ioctl(fd, TUNSETIFF, (void *)&ifr)) < 0 ) { 73 | perror("ioctl(TUNSETIFF)"); 74 | close(fd); 75 | return err; 76 | } 77 | 78 | strcpy(dev, ifr.ifr_name); 79 | 80 | return fd; 81 | } 82 | 83 | /************************************************************************** 84 | * cread: read routine that checks for errors and exits if an error is * 85 | * returned. * 86 | **************************************************************************/ 87 | int cread(int fd, char *buf, int n){ 88 | 89 | int nread; 90 | 91 | if((nread=read(fd, buf, n)) < 0){ 92 | perror("Reading data"); 93 | exit(1); 94 | } 95 | return nread; 96 | } 97 | 98 | /************************************************************************** 99 | * cwrite: write routine that checks for errors and exits if an error is * 100 | * returned. * 101 | **************************************************************************/ 102 | int cwrite(int fd, char *buf, int n){ 103 | 104 | int nwrite; 105 | 106 | if((nwrite=write(fd, buf, n)) < 0){ 107 | perror("Writing data"); 108 | exit(1); 109 | } 110 | return nwrite; 111 | } 112 | 113 | /************************************************************************** 114 | * read_n: ensures we read exactly n bytes, and puts them into "buf". * 115 | * (unless EOF, of course) * 116 | **************************************************************************/ 117 | int read_n(int fd, char *buf, int n) { 118 | 119 | int nread, left = n; 120 | 121 | while(left > 0) { 122 | if ((nread = cread(fd, buf, left)) == 0){ 123 | return 0 ; 124 | }else { 125 | left -= nread; 126 | buf += nread; 127 | } 128 | } 129 | return n; 130 | } 131 | 132 | /************************************************************************** 133 | * do_debug: prints debugging stuff (doh!) * 134 | **************************************************************************/ 135 | void do_debug(char *msg, ...){ 136 | 137 | va_list argp; 138 | 139 | if(debug) { 140 | va_start(argp, msg); 141 | vfprintf(stderr, msg, argp); 142 | va_end(argp); 143 | } 144 | } 145 | 146 | /************************************************************************** 147 | * my_err: prints custom error messages on stderr. * 148 | **************************************************************************/ 149 | void my_err(char *msg, ...) { 150 | 151 | va_list argp; 152 | 153 | va_start(argp, msg); 154 | vfprintf(stderr, msg, argp); 155 | va_end(argp); 156 | } 157 | 158 | /************************************************************************** 159 | * usage: prints usage and exits. * 160 | **************************************************************************/ 161 | void usage(void) { 162 | fprintf(stderr, "Usage:\n"); 163 | fprintf(stderr, "%s -i [-s|-c ] [-p ] [-u|-a] [-d]\n", progname); 164 | fprintf(stderr, "%s -h\n", progname); 165 | fprintf(stderr, "\n"); 166 | fprintf(stderr, "-i : Name of interface to use (mandatory)\n"); 167 | fprintf(stderr, "-s|-c : run in server mode (-s), or specify server address (-c ) (mandatory)\n"); 168 | fprintf(stderr, "-p : port to listen on (if run in server mode) or to connect to (in client mode), default 55555\n"); 169 | fprintf(stderr, "-u|-a: use TUN (-u, default) or TAP (-a)\n"); 170 | fprintf(stderr, "-d: outputs debug information while running\n"); 171 | fprintf(stderr, "-h: prints this help text\n"); 172 | exit(1); 173 | } 174 | 175 | int main(int argc, char *argv[]) { 176 | 177 | int tap_fd, option; 178 | int flags = IFF_TUN; 179 | char if_name[IFNAMSIZ] = ""; 180 | int maxfd; 181 | uint16_t nread, nwrite, plength; 182 | char buffer[BUFSIZE]; 183 | struct sockaddr_in local, remote; 184 | char remote_ip[16] = ""; /* dotted quad IP string */ 185 | unsigned short int port = PORT; 186 | int sock_fd, net_fd, optval = 1; 187 | socklen_t remotelen; 188 | int cliserv = -1; /* must be specified on cmd line */ 189 | unsigned long int tap2net = 0, net2tap = 0; 190 | 191 | progname = argv[0]; 192 | 193 | /* Check command line options */ 194 | while((option = getopt(argc, argv, "i:sc:p:uahd")) > 0) { 195 | switch(option) { 196 | case 'd': 197 | debug = 1; 198 | break; 199 | case 'h': 200 | usage(); 201 | break; 202 | case 'i': 203 | strncpy(if_name,optarg, IFNAMSIZ-1); 204 | break; 205 | case 's': 206 | cliserv = SERVER; 207 | break; 208 | case 'c': 209 | cliserv = CLIENT; 210 | strncpy(remote_ip,optarg,15); 211 | break; 212 | case 'p': 213 | port = atoi(optarg); 214 | break; 215 | case 'u': 216 | flags = IFF_TUN; 217 | break; 218 | case 'a': 219 | flags = IFF_TAP; 220 | break; 221 | default: 222 | my_err("Unknown option %c\n", option); 223 | usage(); 224 | } 225 | } 226 | 227 | argv += optind; 228 | argc -= optind; 229 | 230 | if(argc > 0) { 231 | my_err("Too many options!\n"); 232 | usage(); 233 | } 234 | 235 | if(*if_name == '\0') { 236 | my_err("Must specify interface name!\n"); 237 | usage(); 238 | } else if(cliserv < 0) { 239 | my_err("Must specify client or server mode!\n"); 240 | usage(); 241 | } else if((cliserv == CLIENT)&&(*remote_ip == '\0')) { 242 | my_err("Must specify server address!\n"); 243 | usage(); 244 | } 245 | 246 | /* initialize tun/tap interface */ 247 | if ( (tap_fd = tun_alloc(if_name, flags | IFF_NO_PI)) < 0 ) { 248 | my_err("Error connecting to tun/tap interface %s!\n", if_name); 249 | exit(1); 250 | } 251 | 252 | do_debug("Successfully connected to interface %s\n", if_name); 253 | 254 | if ( (sock_fd = socket(AF_INET, SOCK_STREAM, 0)) < 0) { 255 | perror("socket()"); 256 | exit(1); 257 | } 258 | 259 | if(cliserv == CLIENT) { 260 | /* Client, try to connect to server */ 261 | 262 | /* assign the destination address */ 263 | memset(&remote, 0, sizeof(remote)); 264 | remote.sin_family = AF_INET; 265 | remote.sin_addr.s_addr = inet_addr(remote_ip); 266 | remote.sin_port = htons(port); 267 | 268 | /* connection request */ 269 | if (connect(sock_fd, (struct sockaddr*) &remote, sizeof(remote)) < 0) { 270 | perror("connect()"); 271 | exit(1); 272 | } 273 | 274 | net_fd = sock_fd; 275 | do_debug("CLIENT: Connected to server %s\n", inet_ntoa(remote.sin_addr)); 276 | 277 | } else { 278 | /* Server, wait for connections */ 279 | 280 | /* avoid EADDRINUSE error on bind() */ 281 | if(setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, (char *)&optval, sizeof(optval)) < 0) { 282 | perror("setsockopt()"); 283 | exit(1); 284 | } 285 | 286 | memset(&local, 0, sizeof(local)); 287 | local.sin_family = AF_INET; 288 | local.sin_addr.s_addr = htonl(INADDR_ANY); 289 | local.sin_port = htons(port); 290 | if (bind(sock_fd, (struct sockaddr*) &local, sizeof(local)) < 0) { 291 | perror("bind()"); 292 | exit(1); 293 | } 294 | 295 | if (listen(sock_fd, 5) < 0) { 296 | perror("listen()"); 297 | exit(1); 298 | } 299 | 300 | /* wait for connection request */ 301 | remotelen = sizeof(remote); 302 | memset(&remote, 0, remotelen); 303 | if ((net_fd = accept(sock_fd, (struct sockaddr*)&remote, &remotelen)) < 0) { 304 | perror("accept()"); 305 | exit(1); 306 | } 307 | 308 | do_debug("SERVER: Client connected from %s\n", inet_ntoa(remote.sin_addr)); 309 | } 310 | 311 | /* use select() to handle two descriptors at once */ 312 | maxfd = (tap_fd > net_fd)?tap_fd:net_fd; 313 | 314 | while(1) { 315 | int ret; 316 | fd_set rd_set; 317 | 318 | FD_ZERO(&rd_set); 319 | FD_SET(tap_fd, &rd_set); FD_SET(net_fd, &rd_set); 320 | 321 | ret = select(maxfd + 1, &rd_set, NULL, NULL, NULL); 322 | 323 | if (ret < 0 && errno == EINTR){ 324 | continue; 325 | } 326 | 327 | if (ret < 0) { 328 | perror("select()"); 329 | exit(1); 330 | } 331 | 332 | if(FD_ISSET(tap_fd, &rd_set)) { 333 | /* data from tun/tap: just read it and write it to the network */ 334 | 335 | nread = cread(tap_fd, buffer, BUFSIZE); 336 | 337 | tap2net++; 338 | do_debug("TAP2NET %lu: Read %d bytes from the tap interface\n", tap2net, nread); 339 | 340 | /* write length + packet */ 341 | plength = htons(nread); 342 | nwrite = cwrite(net_fd, (char *)&plength, sizeof(plength)); 343 | nwrite = cwrite(net_fd, buffer, nread); 344 | 345 | do_debug("TAP2NET %lu: Written %d bytes to the network\n", tap2net, nwrite); 346 | } 347 | 348 | if(FD_ISSET(net_fd, &rd_set)) { 349 | /* data from the network: read it, and write it to the tun/tap interface. 350 | * We need to read the length first, and then the packet */ 351 | 352 | /* Read length */ 353 | nread = read_n(net_fd, (char *)&plength, sizeof(plength)); 354 | if(nread == 0) { 355 | /* ctrl-c at the other end */ 356 | break; 357 | } 358 | 359 | net2tap++; 360 | 361 | /* read packet */ 362 | nread = read_n(net_fd, buffer, ntohs(plength)); 363 | do_debug("NET2TAP %lu: Read %d bytes from the network\n", net2tap, nread); 364 | 365 | /* now buffer[] contains a full packet or frame, write it into the tun/tap interface */ 366 | nwrite = cwrite(tap_fd, buffer, nread); 367 | do_debug("NET2TAP %lu: Written %d bytes to the tap interface\n", net2tap, nwrite); 368 | } 369 | } 370 | 371 | return(0); 372 | } 373 | --------------------------------------------------------------------------------