3 * Tunnel packets via SLIP
5 * (c) 2005 Straylight/Edgeware
8 /*----- Licensing notice --------------------------------------------------*
10 * This file is part of Trivial IP Encryption (TrIPE).
12 * TrIPE is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; either version 2 of the License, or
15 * (at your option) any later version.
17 * TrIPE is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU General Public License for more details.
22 * You should have received a copy of the GNU General Public License
23 * along with TrIPE; if not, write to the Free Software Foundation,
24 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
27 /*----- Header files ------------------------------------------------------*/
33 /*----- Data structures ---------------------------------------------------*/
35 typedef struct slipif {
36 struct slipif *next; /* Next one in the list */
37 int ifd, ofd; /* File descriptors to talk on */
38 char *name; /* Interface name */
39 pid_t kid; /* Child process id */
40 unsigned f; /* Various flags */
41 # define F_INUSE 1u /* Interface is in use */
42 # define F_DYNAMIC 2u /* Interface found dynamically */
46 const tunnel_ops *ops; /* Pointer to operations */
47 slipif *sl; /* My interface record */
48 sel_file f; /* Selector for SLIP tty */
49 struct peer *p; /* Pointer to my peer */
50 unsigned st; /* Current parser state */
51 # define ST_ESC 1u /* Last saw an escape character */
52 # define ST_BAD 2u /* This packet is malformed */
53 # define ST_EOF 4u /* File descriptor reported EOF */
54 size_t n; /* Number of bytes used in buffer */
55 octet buf[PKBUFSZ]; /* Buffer for incoming data */
58 /*----- Static variables --------------------------------------------------*/
60 static slipif *slipifs; /* List of available interfaces */
61 static const char *slipcmd; /* Script to make new interfaces */
63 /*----- Main code ---------------------------------------------------------*/
67 * Arguments: @int fd@ = file descriptor to read
68 * @unsigned mode@ = what's happened
69 * @void *v@ = pointer to tunnel block
73 * Use: Reads data from the tunnel.
76 static void t_read(int fd, unsigned mode, void *v)
80 const octet *p, *l, *ll;
86 /* --- Read the input data --- */
88 n = read(fd, buf_t, sizeof(buf_t));
91 #if defined(EWOULDBLOCK) && EWOULDBLOCK != EAGAIN
92 errno == EWOULDBLOCK ||
96 a_warn("TUN", "%s", p_ifname(t->p), "read-error", "?ERRNO", A_END);
100 a_warn("TUN", "%s", p_ifname(t->p), "slip", "eof", A_END);
105 IF_TRACING(T_TUNNEL, {
106 trace_block(T_PACKET, "tun-slip: SLIP-encapsulated data",
110 /* --- Decapsulate the packet --- */
112 for (p = buf_t, l = p + n, st = t->st,
113 q = t->buf + t->n, ll = t->buf + sizeof(t->buf);
121 else if (st & ST_ESC)
122 a_warn("TUN", "%s", p_ifname(t->p), "slip", "escape-end", A_END);
123 else if (q == t->buf) {
124 T( trace(T_TUNNEL, "tun-slip: empty packet"); )
126 IF_TRACING(T_TUNNEL, {
127 trace(T_TUNNEL, "tun-slip: packet arrived");
128 trace_block(T_PACKET, "tun-slip: packet contents",
131 buf_init(&b, t->buf, q - t->buf);
135 st &= ~(ST_ESC | ST_BAD);
138 if ((st & ST_ESC) && !(st & ST_BAD)) {
139 a_warn("TUN", "%s", p_ifname(t->p), "slip", "bad-escape", A_END);
153 if ((st & ST_ESC) && !(st & ST_BAD)) {
154 a_warn("TUN", "%s", p_ifname(t->p), "slip", "bad-escape", A_END);
158 if (!(st & ST_BAD)) {
162 a_warn("TUN", "%s", p_ifname(t->p), "slip", "overflow", A_END);
175 /* --- @t_init@ --- *
181 * Use: Initializes the tunneling system. Maybe this will require
182 * opening file descriptors or something.
185 static void t_init(void)
189 slipif *sl, **tail = &slipifs;
190 unsigned long uli, ulo;
193 if ((p = getenv("TRIPE_SLIPIF")) == 0)
196 /* --- Build the list of available interfaces --- */
202 if (*p == '/' || *p == '.') {
204 T( trace(T_TUNNEL, "tun-slip: declared slip command `%s'", slipcmd); )
207 uli = strtoul(p, &q, 0);
208 if (uli > INT_MAX || q == p)
214 ulo = strtoul(p, &q, 0);
215 if (ulo > INT_MAX || q == p)
218 if (*q != '=' || (n = strcspn(q + 1, ":")) == 0)
223 fdflags(sl->ifd, O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC);
224 fdflags(sl->ofd, O_NONBLOCK, 0, FD_CLOEXEC, FD_CLOEXEC);
226 sl->name = xmalloc(n + 1);
229 memcpy(sl->name, q + 1, n);
233 T( trace(T_TUNNEL, "tun-slip: declared slipif %d,%d=%s",
234 sl->ifd, sl->ofd, sl->name); )
243 moan("bad slip interface list");
246 /* --- @t_create@ --- *
248 * Arguments: @peer *p@ = pointer to peer block
249 * @int fd@ = file descriptor of tunnel device (unused)
250 * @char **ifn@ = where to put the interface name
252 * Returns: A tunnel block if it worked, or null on failure.
254 * Use: Initializes a new tunnel.
257 static tunnel *t_create(peer *p, int fd, char **ifn)
260 int pin[2] = { -1, -1 }, pout[2] = { -1, -1 };
266 static const char end[] = { SL_END, SL_END };
268 /* --- Try to find a spare static interface --- */
270 for (sl = slipifs; sl; sl = sl->next) {
271 if (!(sl->f & F_INUSE)) {
272 T( trace(T_TUNNEL, "tun-slip: %s using static slipif %s",
273 p_name(p), sl->name); )
278 /* --- If no dynamic interfaces are available, give up --- */
281 a_warn("TUN", "-", "slip", "no-slip-interfaces", A_END);
285 /* --- Fork off a child process to create a dynamic SLIP interface --- */
287 if (pipe(pin) || pipe(pout)) {
288 a_warn("TUN", "-", "slip", "pipe-error", "?ERRNO", A_END);
291 if ((kid = fork()) < 0) {
292 a_warn("TUN", "-", "slip", "fork-error", "?ERRNO", A_END);
296 close(pin[1]); close(pout[0]);
297 md[0].cur = pin[0]; md[0].want = STDIN_FILENO;
298 md[1].cur = pout[0]; md[1].want = STDOUT_FILENO;
300 execlp(slipcmd, slipcmd, p_name(p), (char *)0);
304 /* --- Read the interface name --- */
307 close(pin[0]); pin[0] = -1;
308 close(pout[1]); pout[1] = -1;
311 if (read(pout[0], &ch, 1) != 1 || ch == SL_END) {
312 a_warn("TUN", "-", "slip", "read-ifname-failed", "?ERRNO", A_END);
320 sl->name = xstrdup(d.buf);
326 T( trace(T_TUNNEL, "tun-slip: %s using dynamic slipif %s",
327 p_name(p), sl->name); )
328 fdflags(pout[0], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC);
329 fdflags(pin[1], O_NONBLOCK, 0, FD_CLOEXEC, FD_CLOEXEC);
331 /* --- Set up the new tunnel --- */
341 sel_initfile(&sel, &t->f, sl->ifd, SEL_READ, t_read, t);
343 write(sl->ofd, end, sizeof(end));
344 *ifn = xstrdup(sl->name);
348 /* --- Tidy up after a failure --- */
351 #define CLOSE(fd) do if (fd != -1) close(fd); while (0)
352 CLOSE(pin[0]); CLOSE(pout[0]);
353 CLOSE(pin[1]); CLOSE(pout[1]);
355 if (kid != -1) kill(kid, SIGTERM);
356 if (sl && (sl->f & F_DYNAMIC)) DESTROY(sl);
361 /* --- @t_setifname@ --- *
363 * Arguments: @tunnel *t@ = pointer to tunnel block
364 * @const char *ifn@ = new interface name
368 * Use: Updates the interface name of a slip interface.
371 static void t_setifname(tunnel *t, const char *ifn)
372 { xfree(t->sl->name); t->sl->name = xstrdup(ifn); }
374 /* --- @t_inject@ --- *
376 * Arguments: @tunnel *t@ = pointer to tunnel block
377 * @buf *b@ = buffer to send
381 * Use: Injects a packet into the local network stack.
384 static void t_inject(tunnel *t, buf *b)
386 octet buf[PKBUFSZ * 2 + 2];
390 IF_TRACING(T_TUNNEL, {
391 trace(T_TUNNEL, "tun-slip: inject decrypted packet");
392 trace_block(T_PACKET, "tun-slip: packet contents", BBASE(b), BLEN(b));
397 for (p = BBASE(b), l = BCUR(b); p < l; p++) {
399 case SL_END: *q++ = SL_ESC; *q++ = SL_ESCEND; break;
400 case SL_ESC: *q++ = SL_ESC; *q++ = SL_ESCESC; break;
401 default: *q++ = *p; break;
405 IF_TRACING(T_TUNNEL, {
406 trace_block(T_PACKET, "tun-slip: SLIP-encapsulated contents",
409 write(t->sl->ofd, buf, q - buf);
412 /* --- @t_destroy@ --- *
414 * Arguments: @tunnel *t@ = pointer to tunnel block
418 * Use: Destroys a tunnel.
421 static void t_destroy(tunnel *t)
425 /* --- If it reported EOF, leave it out-of-action --- */
427 if (!(t->st & ST_EOF)) {
431 if (sl && (sl->f & F_DYNAMIC)) {
432 T( trace(T_TUNNEL, "tun-slip: releasing dynamic slipif %s", sl->name); )
435 kill(sl->kid, SIGTERM);
442 const tunnel_ops tun_slip = {
452 /*----- That's all, folks -------------------------------------------------*/