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 #define SL_ESCEND 0xdc
68 #define SL_ESCESC 0xdd
72 * Arguments: @int fd@ = file descriptor to read
73 * @unsigned mode@ = what's happened
74 * @void *v@ = pointer to tunnel block
78 * Use: Reads data from the tunnel.
81 static void t_read(int fd, unsigned mode, void *v)
85 const octet *p, *l, *ll;
91 /* --- Read the input data --- */
93 n = read(fd, buf_t, sizeof(buf_t));
96 #if defined(EWOULDBLOCK) && EWOULDBLOCK != EAGAIN
97 errno == EWOULDBLOCK ||
101 a_warn("TUN", "%s", p_ifname(t->p), "read-error", "?ERRNO", A_END);
105 a_warn("TUN", "%s", p_ifname(t->p), "slip", "eof", A_END);
110 IF_TRACING(T_TUNNEL, {
111 trace_block(T_PACKET, "tun-slip: SLIP-encapsulated data",
115 /* --- Decapsulate the packet --- */
117 for (p = buf_t, l = p + n, st = t->st,
118 q = t->buf + t->n, ll = t->buf + sizeof(t->buf);
126 else if (st & ST_ESC)
127 a_warn("TUN", "%s", p_ifname(t->p), "slip", "escape-end", A_END);
128 else if (q == t->buf) {
129 T( trace(T_TUNNEL, "tun-slip: empty packet"); )
131 IF_TRACING(T_TUNNEL, {
132 trace(T_TUNNEL, "tun-slip: packet arrived");
133 trace_block(T_PACKET, "tun-slip: packet contents",
136 buf_init(&b, t->buf, q - t->buf);
140 st &= ~(ST_ESC | ST_BAD);
143 if ((st & ST_ESC) && !(st & ST_BAD)) {
144 a_warn("TUN", "%s", p_ifname(t->p), "slip", "bad-escape", A_END);
158 if ((st & ST_ESC) && !(st & ST_BAD)) {
159 a_warn("TUN", "%s", p_ifname(t->p), "slip", "bad-escape", A_END);
163 if (!(st & ST_BAD)) {
167 a_warn("TUN", "%s", p_ifname(t->p), "slip", "overflow", A_END);
180 /* --- @t_init@ --- *
186 * Use: Initializes the tunneling system. Maybe this will require
187 * opening file descriptors or something.
190 static void t_init(void)
194 slipif *sl, **tail = &slipifs;
195 unsigned long uli, ulo;
198 if ((p = getenv("TRIPE_SLIPIF")) == 0)
201 /* --- Build the list of available interfaces --- */
207 if (*p == '/' || *p == '.') {
209 T( trace(T_TUNNEL, "tun-slip: declared slip command `%s'", slipcmd); )
212 uli = strtoul(p, &q, 0);
213 if (uli > INT_MAX || q == p)
219 ulo = strtoul(p, &q, 0);
220 if (ulo > INT_MAX || q == p)
223 if (*q != '=' || (n = strcspn(q + 1, ":")) == 0)
228 fdflags(sl->ifd, O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC);
229 fdflags(sl->ofd, O_NONBLOCK, 0, FD_CLOEXEC, FD_CLOEXEC);
231 sl->name = xmalloc(n + 1);
234 memcpy(sl->name, q + 1, n);
238 T( trace(T_TUNNEL, "tun-slip: declared slipif %d,%d=%s",
239 sl->ifd, sl->ofd, sl->name); )
248 moan("bad slip interface list");
251 /* --- @t_create@ --- *
253 * Arguments: @peer *p@ = pointer to peer block
254 * @char **ifn@ = where to put the interface name
256 * Returns: A tunnel block if it worked, or null on failure.
258 * Use: Initializes a new tunnel.
261 static tunnel *t_create(peer *p, char **ifn)
264 int pin[2] = { -1, -1 }, pout[2] = { -1, -1 };
269 static const char end[] = { SL_END, SL_END };
271 /* --- Try to find a spare static interface --- */
273 for (sl = slipifs; sl; sl = sl->next) {
274 if (!(sl->f & F_INUSE)) {
275 T( trace(T_TUNNEL, "tun-slip: %s using static slipif %s",
276 p_name(p), sl->name); )
281 /* --- If no dynamic interfaces are available, give up --- */
284 a_warn("TUN", "-", "slip", "no-slip-interfaces", A_END);
288 /* --- Fork off a child process to create a dynamic SLIP interface --- */
290 if (pipe(pin) || pipe(pout)) {
291 a_warn("TUN", "-", "slip", "pipe-error", "?ERRNO", A_END);
294 if ((kid = fork()) < 0) {
295 a_warn("TUN", "-", "slip", "fork-error", "?ERRNO", A_END);
301 dup2(pin[0], STDIN_FILENO);
302 dup2(pout[1], STDOUT_FILENO);
303 execlp(slipcmd, slipcmd, p_name(p), (char *)0);
307 /* --- Read the interface name --- */
310 close(pin[0]); pin[0] = -1;
311 close(pout[1]); pout[1] = -1;
314 if (read(pout[0], &ch, 1) != 1 || ch == SL_END) {
315 a_warn("TUN", "-", "slip", "read-ifname-failed", "?ERRNO", A_END);
323 sl->name = xstrdup(d.buf);
329 T( trace(T_TUNNEL, "tun-slip: %s using dynamic slipif %s",
330 p_name(p), sl->name); )
331 fdflags(pout[0], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC);
332 fdflags(pin[1], O_NONBLOCK, 0, FD_CLOEXEC, FD_CLOEXEC);
334 /* --- Set up the new tunnel --- */
344 sel_initfile(&sel, &t->f, sl->ifd, SEL_READ, t_read, t);
346 write(sl->ofd, end, sizeof(end));
347 *ifn = xstrdup(sl->name);
351 /* --- Tidy up after a failure --- */
354 #define CLOSE(fd) do if (fd != -1) close(fd); while (0)
355 CLOSE(pin[0]); CLOSE(pout[0]);
356 CLOSE(pin[1]); CLOSE(pout[1]);
358 if (kid != -1) kill(kid, SIGTERM);
359 if (sl && (sl->f & F_DYNAMIC)) DESTROY(sl);
364 /* --- @t_setifname@ --- *
366 * Arguments: @tunnel *t@ = pointer to tunnel block
367 * @const char *ifn@ = new interface name
371 * Use: Updates the interface name of a slip interface.
374 static void t_setifname(tunnel *t, const char *ifn)
375 { xfree(t->sl->name); t->sl->name = xstrdup(ifn); }
377 /* --- @t_inject@ --- *
379 * Arguments: @tunnel *t@ = pointer to tunnel block
380 * @buf *b@ = buffer to send
384 * Use: Injects a packet into the local network stack.
387 static void t_inject(tunnel *t, buf *b)
389 octet buf[PKBUFSZ * 2 + 2];
393 IF_TRACING(T_TUNNEL, {
394 trace(T_TUNNEL, "tun-slip: inject decrypted packet");
395 trace_block(T_PACKET, "tun-slip: packet contents", BBASE(b), BLEN(b));
400 for (p = BBASE(b), l = BCUR(b); p < l; p++) {
402 case SL_END: *q++ = SL_ESC; *q++ = SL_ESCEND; break;
403 case SL_ESC: *q++ = SL_ESC; *q++ = SL_ESCESC; break;
404 default: *q++ = *p; break;
408 IF_TRACING(T_TUNNEL, {
409 trace_block(T_PACKET, "tun-slip: SLIP-encapsulated contents",
412 write(t->sl->ofd, buf, q - buf);
415 /* --- @t_destroy@ --- *
417 * Arguments: @tunnel *t@ = pointer to tunnel block
421 * Use: Destroys a tunnel.
424 static void t_destroy(tunnel *t)
428 /* --- If it reported EOF, leave it out-of-action --- */
430 if (!(t->st & ST_EOF)) {
434 if (sl && (sl->f & F_DYNAMIC)) {
435 T( trace(T_TUNNEL, "tun-slip: releasing dynamic slipif %s", sl->name); )
438 kill(sl->kid, SIGTERM);
445 const tunnel_ops tun_slip = {
454 /*----- That's all, folks -------------------------------------------------*/