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_MASK 3u /* Mask for the above bits */
54 # define ST_EOF 4u /* File descriptor reported EOF */
55 size_t n; /* Number of bytes used in buffer */
56 octet buf[PKBUFSZ]; /* Buffer for incoming data */
59 /*----- Static variables --------------------------------------------------*/
61 static slipif *slipifs; /* List of available interfaces */
62 static const char *slipcmd; /* Script to make new interfaces */
64 /*----- Main code ---------------------------------------------------------*/
68 * Arguments: @int fd@ = file descriptor to read
69 * @unsigned mode@ = what's happened
70 * @void *v@ = pointer to tunnel block
74 * Use: Reads data from the tunnel.
77 static void t_read(int fd, unsigned mode, void *v)
81 const octet *p, *l, *ll;
87 /* --- Read the input data --- */
89 n = read(fd, buf_t, sizeof(buf_t));
92 #if defined(EWOULDBLOCK) && EWOULDBLOCK != EAGAIN
93 errno == EWOULDBLOCK ||
97 a_warn("TUN", "%s", p_ifname(t->p), "slip",
98 "read-error", "?ERRNO", A_END);
102 a_warn("TUN", "%s", p_ifname(t->p), "slip", "eof", A_END);
103 t->st = (t->st & ~ST_MASK) | ST_EOF;
107 IF_TRACING(T_TUNNEL, {
108 trace_block(T_PACKET, "tun-slip: SLIP-encapsulated data",
112 /* --- Decapsulate the packet --- */
114 for (p = buf_t, l = p + n, st = t->st,
115 q = t->buf + t->n, ll = t->buf + sizeof(t->buf);
123 else if (st & ST_ESC)
124 a_warn("TUN", "%s", p_ifname(t->p), "slip", "escape-end", A_END);
125 else if (q == t->buf) {
126 T( trace(T_TUNNEL, "tun-slip: empty packet"); )
128 IF_TRACING(T_TUNNEL, {
129 trace(T_TUNNEL, "tun-slip: packet arrived");
130 trace_block(T_PACKET, "tun-slip: packet contents",
133 buf_init(&b, t->buf, q - t->buf);
140 if ((st & ST_ESC) && !(st & ST_BAD)) {
141 a_warn("TUN", "%s", p_ifname(t->p), "slip", "bad-escape", A_END);
155 if ((st & ST_ESC) && !(st & ST_BAD)) {
156 a_warn("TUN", "%s", p_ifname(t->p), "slip", "bad-escape", A_END);
160 if (!(st & ST_BAD)) {
164 a_warn("TUN", "%s", p_ifname(t->p), "slip", "overflow", A_END);
177 /* --- @t_init@ --- *
183 * Use: Initializes the tunneling system. Maybe this will require
184 * opening file descriptors or something.
187 static void t_init(void)
191 slipif *sl, **tail = &slipifs;
192 unsigned long uli, ulo;
195 if ((p = getenv("TRIPE_SLIPIF")) == 0)
198 /* --- Build the list of available interfaces --- */
204 if (*p == '/' || *p == '.') {
206 T( trace(T_TUNNEL, "tun-slip: declared slip command `%s'", slipcmd); )
209 uli = strtoul(p, &q, 0);
210 if (uli > INT_MAX || q == p)
216 ulo = strtoul(p, &q, 0);
217 if (ulo > INT_MAX || q == p)
220 if (*q != '=' || (n = strcspn(q + 1, ":")) == 0)
225 fdflags(sl->ifd, O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC);
226 fdflags(sl->ofd, O_NONBLOCK, 0, FD_CLOEXEC, FD_CLOEXEC);
228 sl->name = xmalloc(n + 1);
231 memcpy(sl->name, q + 1, n);
235 T( trace(T_TUNNEL, "tun-slip: declared slipif %d,%d=%s",
236 sl->ifd, sl->ofd, sl->name); )
245 moan("bad slip interface list");
248 /* --- @t_create@ --- *
250 * Arguments: @peer *p@ = pointer to peer block
251 * @int fd@ = file descriptor of tunnel device (unused)
252 * @char **ifn@ = where to put the interface name
254 * Returns: A tunnel block if it worked, or null on failure.
256 * Use: Initializes a new tunnel.
259 static tunnel *t_create(peer *p, int fd, char **ifn)
262 int pin[2] = { -1, -1 }, pout[2] = { -1, -1 };
268 static const char end[] = { SL_END, SL_END };
270 /* --- Try to find a spare static interface --- */
272 for (sl = slipifs; sl; sl = sl->next) {
273 if (!(sl->f & F_INUSE)) {
274 T( trace(T_TUNNEL, "tun-slip: %s using static slipif %s",
275 p_name(p), sl->name); )
280 /* --- If no dynamic interfaces are available, give up --- */
283 a_warn("TUN", "-", "slip", "no-slip-interfaces", A_END);
287 /* --- Fork off a child process to create a dynamic SLIP interface --- */
289 if (pipe(pin) || pipe(pout)) {
290 a_warn("TUN", "-", "slip", "pipe-error", "?ERRNO", A_END);
293 if ((kid = fork()) < 0) {
294 a_warn("TUN", "-", "slip", "fork-error", "?ERRNO", A_END);
298 close(pin[1]); close(pout[0]);
299 md[0].cur = pin[0]; md[0].want = STDIN_FILENO;
300 md[1].cur = pout[1]; md[1].want = STDOUT_FILENO;
302 execlp(slipcmd, slipcmd, p_name(p), (char *)0);
306 /* --- Read the interface name --- */
309 close(pin[0]); pin[0] = -1;
310 close(pout[1]); pout[1] = -1;
313 if (read(pout[0], &ch, 1) != 1 || ch == SL_END) {
314 a_warn("TUN", "-", "slip", "read-ifname-failed", "?ERRNO", A_END);
322 sl->name = xstrdup(d.buf);
328 T( trace(T_TUNNEL, "tun-slip: %s using dynamic slipif %s",
329 p_name(p), sl->name); )
330 fdflags(pout[0], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC);
331 fdflags(pin[1], O_NONBLOCK, 0, FD_CLOEXEC, FD_CLOEXEC);
333 /* --- Set up the new tunnel --- */
343 sel_initfile(&sel, &t->f, sl->ifd, SEL_READ, t_read, t);
345 write(sl->ofd, end, sizeof(end));
346 *ifn = xstrdup(sl->name);
350 /* --- Tidy up after a failure --- */
353 #define CLOSE(fd) do if (fd != -1) close(fd); while (0)
354 CLOSE(pin[0]); CLOSE(pout[0]);
355 CLOSE(pin[1]); CLOSE(pout[1]);
357 if (kid != -1) kill(kid, SIGTERM);
358 if (sl && (sl->f & F_DYNAMIC)) DESTROY(sl);
363 /* --- @t_setifname@ --- *
365 * Arguments: @tunnel *t@ = pointer to tunnel block
366 * @const char *ifn@ = new interface name
370 * Use: Updates the interface name of a slip interface.
373 static void t_setifname(tunnel *t, const char *ifn)
374 { xfree(t->sl->name); t->sl->name = xstrdup(ifn); }
376 /* --- @t_inject@ --- *
378 * Arguments: @tunnel *t@ = pointer to tunnel block
379 * @buf *b@ = buffer to send
383 * Use: Injects a packet into the local network stack.
386 static void t_inject(tunnel *t, buf *b)
388 octet buf[PKBUFSZ * 2 + 2];
392 IF_TRACING(T_TUNNEL, {
393 trace(T_TUNNEL, "tun-slip: inject decrypted packet");
394 trace_block(T_PACKET, "tun-slip: packet contents", BBASE(b), BLEN(b));
399 for (p = BBASE(b), l = BCUR(b); p < l; p++) {
401 case SL_END: *q++ = SL_ESC; *q++ = SL_ESCEND; break;
402 case SL_ESC: *q++ = SL_ESC; *q++ = SL_ESCESC; break;
403 default: *q++ = *p; break;
407 IF_TRACING(T_TUNNEL, {
408 trace_block(T_PACKET, "tun-slip: SLIP-encapsulated contents",
411 write(t->sl->ofd, buf, q - buf);
414 /* --- @t_destroy@ --- *
416 * Arguments: @tunnel *t@ = pointer to tunnel block
420 * Use: Destroys a tunnel.
423 static void t_destroy(tunnel *t)
427 /* --- If it reported EOF, leave it out-of-action --- */
429 if (!(t->st & ST_EOF)) {
433 if (sl && (sl->f & F_DYNAMIC)) {
434 T( trace(T_TUNNEL, "tun-slip: releasing dynamic slipif %s", sl->name); )
437 kill(sl->kid, SIGTERM);
444 const tunnel_ops tun_slip = {
454 /*----- That's all, folks -------------------------------------------------*/