chiark / gitweb /
General overhaul of tunnelling: allow multiple tunnel drivers in one daemon,
[tripe] / tun-slip.c
CommitLineData
b9066fbb 1/* -*-c-*-
2 *
3 * $Id$
4 *
5 * Tunnel packets via SLIP
6 *
7 * (c) 2005 Straylight/Edgeware
8 */
9
10/*----- Licensing notice --------------------------------------------------*
11 *
12 * This file is part of Trivial IP Encryption (TrIPE).
13 *
14 * TrIPE is free software; you can redistribute it and/or modify
15 * it under the terms of the GNU General Public License as published by
16 * the Free Software Foundation; either version 2 of the License, or
17 * (at your option) any later version.
18 *
19 * TrIPE is distributed in the hope that it will be useful,
20 * but WITHOUT ANY WARRANTY; without even the implied warranty of
21 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
22 * GNU General Public License for more details.
23 *
24 * You should have received a copy of the GNU General Public License
25 * along with TrIPE; if not, write to the Free Software Foundation,
26 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
27 */
28
29/*----- Header files ------------------------------------------------------*/
30
42da2a58 31#define TUN_INTERNALS
32
b9066fbb 33#include "tripe.h"
34
42da2a58 35/*----- Data structures ---------------------------------------------------*/
36
37typedef struct slipif {
38 struct slipif *next; /* Next one in the list */
39 int ifd, ofd; /* File descriptors to talk on */
40 char *name; /* Interface name */
41 pid_t kid; /* Child process id */
42 unsigned f; /* Various flags */
43# define F_INUSE 1u /* Interface is in use */
44# define F_DYNAMIC 2u /* Interface found dynamically */
45} slipif;
46
47struct tunnel {
48 const tunnel_ops *ops; /* Pointer to operations */
49 slipif *sl; /* My interface record */
50 sel_file f; /* Selector for SLIP tty */
51 struct peer *p; /* Pointer to my peer */
52 unsigned st; /* Current parser state */
53# define ST_ESC 1u /* Last saw an escape character */
54# define ST_BAD 2u /* This packet is malformed */
55# define ST_EOF 4u /* File descriptor reported EOF */
56 size_t n; /* Number of bytes used in buffer */
57 octet buf[PKBUFSZ]; /* Buffer for incoming data */
58};
59
b9066fbb 60/*----- Static variables --------------------------------------------------*/
61
62static slipif *slipifs; /* List of available interfaces */
98fdb08d 63static const char *slipcmd; /* Script to make new interfaces */
b9066fbb 64
65/*----- Main code ---------------------------------------------------------*/
66
b9066fbb 67#define SL_END 0xc0
68#define SL_ESC 0xdb
69#define SL_ESCEND 0xdc
70#define SL_ESCESC 0xdd
71
72/* --- @t_read@ --- *
73 *
74 * Arguments: @int fd@ = file descriptor to read
75 * @unsigned mode@ = what's happened
76 * @void *v@ = pointer to tunnel block
77 *
78 * Returns: ---
79 *
80 * Use: Reads data from the tunnel.
81 */
82
83static void t_read(int fd, unsigned mode, void *v)
84{
85 tunnel *t = v;
86 ssize_t n;
87 const octet *p, *l, *ll;
88 octet *q;
89 unsigned st;
90 octet o;
91 buf b;
92
93 /* --- Read the input data --- */
94
95 n = read(fd, buf_t, sizeof(buf_t));
96 if (n < 0) {
97 if (errno == EINTR ||
98fdb08d 98#if defined(EWOULDBLOCK) && EWOULDBLOCK != EAGAIN
b9066fbb 99 errno == EWOULDBLOCK ||
100#endif
101 errno == EAGAIN)
102 return;
103 a_warn("TUN %s read-error -- %s", t->sl->name, strerror(errno));
104 return;
105 }
106 if (!n) {
107 a_warn("TUN %s slip eof", t->sl->name);
42da2a58 108 t->st = ST_EOF;
b9066fbb 109 sel_rmfile(&t->f);
110 return;
111 }
112 IF_TRACING(T_TUNNEL, {
113 trace_block(T_PACKET, "tunnel: SLIP-encapsulated data",
114 buf_t, n);
115 })
116
117 /* --- Decapsulate the packet --- */
118
119 for (p = buf_t, l = p + n, st = t->st,
120 q = t->buf + t->n, ll = t->buf + sizeof(t->buf);
121 p < l;
122 p++) {
123 o = *p;
124 switch (o) {
125 case SL_END:
42da2a58 126 if (st & ST_BAD)
b9066fbb 127 ;
42da2a58 128 else if (st & ST_ESC)
b9066fbb 129 a_warn("TUN %s slip escape-end", t->sl->name);
130 else if (q == t->buf) {
131 T( trace(T_TUNNEL, "tunnel: empty packet"); )
132 } else {
133 IF_TRACING(T_TUNNEL, {
134 trace(T_TUNNEL, "tunnel: packet arrived");
135 trace_block(T_PACKET, "tunnel: packet contents",
136 t->buf, q - t->buf);
137 })
138 buf_init(&b, t->buf, q - t->buf);
139 p_tun(t->p, &b);
140 }
141 q = t->buf;
42da2a58 142 st &= ~(ST_ESC | ST_BAD);
b9066fbb 143 break;
144 case SL_ESC:
42da2a58 145 if ((st & ST_ESC) && !(st & ST_BAD)) {
b9066fbb 146 a_warn("TUN %s slip bad-escape", t->sl->name);
42da2a58 147 st |= ST_BAD;
b9066fbb 148 } else
42da2a58 149 st |= ST_ESC;
b9066fbb 150 break;
151 case SL_ESCEND:
42da2a58 152 if (st & ST_ESC)
b9066fbb 153 o = SL_END;
154 goto emit;
155 case SL_ESCESC:
42da2a58 156 if (st & ST_ESC)
b9066fbb 157 o = SL_ESC;
158 goto emit;
159 default:
42da2a58 160 if ((st & ST_ESC) && !(st & ST_BAD)) {
b9066fbb 161 a_warn("TUN %s slip bad-escape", t->sl->name);
42da2a58 162 st |= ST_BAD;
b9066fbb 163 }
164 emit:
42da2a58 165 if (!(st & ST_BAD)) {
b9066fbb 166 if (q < ll)
167 *q++ = o;
168 else {
169 a_warn("TUN %s slip overflow", t->sl->name);
42da2a58 170 st |= ST_BAD;
b9066fbb 171 }
172 }
42da2a58 173 st &= ~ST_ESC;
b9066fbb 174 break;
175 }
176 }
177
178 t->n = q - t->buf;
179 t->st = st;
180}
181
42da2a58 182/* --- @t_init@ --- *
b9066fbb 183 *
184 * Arguments: ---
185 *
186 * Returns: ---
187 *
188 * Use: Initializes the tunneling system. Maybe this will require
189 * opening file descriptors or something.
190 */
191
42da2a58 192static void t_init(void)
b9066fbb 193{
194 char *p, *q;
195 dstr d = DSTR_INIT;
196 slipif *sl, **tail = &slipifs;
197 unsigned long uli, ulo;
198 size_t n;
199
b9066fbb 200 if ((p = getenv("TRIPE_SLIPIF")) == 0)
42da2a58 201 return;
98fdb08d 202
203 /* --- Build the list of available interfaces --- */
204
b9066fbb 205 dstr_puts(&d, p);
206
207 p = d.buf;
208 for (;;) {
98fdb08d 209 if (*p == '/' || *p == '.') {
210 slipcmd = p;
211 T( trace(T_TUNNEL, "tunnel: declared slip command `%s'", slipcmd); )
212 break;
213 }
b9066fbb 214 uli = strtoul(p, &q, 0);
215 if (uli > INT_MAX || q == p)
216 goto whine;
217 if (*q != ',')
218 ulo = uli;
219 else {
220 p = q + 1;
221 ulo = strtoul(p, &q, 0);
222 if (ulo > INT_MAX || q == p)
223 goto whine;
224 }
225 if (*q != '=' || (n = strcspn(q + 1, ":")) == 0)
226 goto whine;
227 sl = CREATE(slipif);
228 sl->next = 0;
229 sl->ifd = uli;
98fdb08d 230 fdflags(sl->ifd, O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC);
231 fdflags(sl->ofd, O_NONBLOCK, 0, FD_CLOEXEC, FD_CLOEXEC);
b9066fbb 232 sl->ofd = ulo;
233 sl->name = xmalloc(n + 1);
98fdb08d 234 sl->kid = -1;
b9066fbb 235 sl->f = 0;
236 memcpy(sl->name, q + 1, n);
237 sl->name[n] = 0;
238 *tail = sl;
239 tail = &sl->next;
240 T( trace(T_TUNNEL, "tunnel: declared slipif %d,%d=%s",
241 sl->ifd, sl->ofd, sl->name); )
242 p = q + n + 1;
243 if (!*p)
244 break;
245 p++;
246 }
247 return;
248
249whine:
42da2a58 250 moan("bad slip interface list");
b9066fbb 251}
252
42da2a58 253/* --- @t_create@ --- *
b9066fbb 254 *
42da2a58 255 * Arguments: @peer *p@ = pointer to peer block
b9066fbb 256 *
42da2a58 257 * Returns: A tunnel block if it worked, or null on failure.
b9066fbb 258 *
259 * Use: Initializes a new tunnel.
260 */
261
42da2a58 262static tunnel *t_create(peer *p)
b9066fbb 263{
98fdb08d 264 slipif *sl = 0;
265 int pin[2] = { -1, -1 }, pout[2] = { -1, -1 };
266 pid_t kid = -1;
267 dstr d = DSTR_INIT;
268 unsigned char ch;
42da2a58 269 tunnel *t;
b9066fbb 270 static const char end[] = { SL_END, SL_END };
271
98fdb08d 272 /* --- Try to find a spare static interface --- */
273
b9066fbb 274 for (sl = slipifs; sl; sl = sl->next) {
42da2a58 275 if (!(sl->f & F_INUSE)) {
98fdb08d 276 T( trace(T_TUNNEL, "tunnel: %s using static slipif %s",
277 p_name(p), sl->name); )
b9066fbb 278 goto found;
98fdb08d 279 }
b9066fbb 280 }
98fdb08d 281
282 /* --- If no dynamic interfaces are available, give up --- */
283
284 if (!slipcmd) {
42da2a58 285 a_warn("TUN - slip no-slip-interfaces");
98fdb08d 286 goto fail;
287 }
288
289 /* --- Fork off a child process to create a dynamic SLIP interface --- */
290
291 if (pipe(pin) || pipe(pout)) {
42da2a58 292 a_warn("TUN - slip pipe-error -- %s", strerror(errno));
98fdb08d 293 goto fail;
294 }
295 if ((kid = fork()) < 0) {
42da2a58 296 a_warn("TUN - slip fork-error -- %s", strerror(errno));
98fdb08d 297 goto fail;
298 }
299 if (!kid) {
300 close(pin[1]);
301 close(pout[0]);
302 dup2(pin[0], STDIN_FILENO);
303 dup2(pout[1], STDOUT_FILENO);
304 execlp(slipcmd, slipcmd, p_name(p), (char *)0);
305 _exit(127);
306 }
307
308 /* --- Read the interface name --- */
309
310 sl = CREATE(slipif);
311 close(pin[0]); pin[0] = -1;
312 close(pout[1]); pout[1] = -1;
313 for (;;) {
314 errno = EIO;
315 if (read(pout[0], &ch, 1) != 1 || ch == SL_END) {
42da2a58 316 a_warn("TUN - slip read-ifname-failed -- %s", strerror(errno));
98fdb08d 317 goto fail;
318 }
319 if (ch == '\n')
320 break;
321 DPUTC(&d, (char)ch);
322 }
323 DPUTZ(&d);
324 sl->name = xstrdup(d.buf);
325 sl->ifd = pout[0];
326 sl->ofd = pin[1];
327 sl->kid = kid;
328 sl->next = 0;
42da2a58 329 sl->f = F_DYNAMIC;
98fdb08d 330 T( trace(T_TUNNEL, "tunnel: %s using dynamic slipif %s",
331 p_name(p), sl->name); )
332 fdflags(pout[0], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC);
333 fdflags(pin[1], O_NONBLOCK, 0, FD_CLOEXEC, FD_CLOEXEC);
334
335 /* --- Set up the new tunnel --- */
b9066fbb 336
337found:
42da2a58 338 t = CREATE(tunnel);
339 t->ops = &tun_slip;
b9066fbb 340 t->p = p;
341 t->sl = sl;
342 t->st = 0;
343 t->n = 0;
42da2a58 344 sl->f |= F_INUSE;
b9066fbb 345 sel_initfile(&sel, &t->f, sl->ifd, SEL_READ, t_read, t);
346 sel_addfile(&t->f);
347 write(sl->ofd, end, sizeof(end));
98fdb08d 348 dstr_destroy(&d);
42da2a58 349 return (t);
98fdb08d 350
351 /* --- Tidy up after a failure --- */
352
353fail:
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]);
357#undef CLOSE
358 if (kid != -1) kill(kid, SIGTERM);
42da2a58 359 if (sl && (sl->f & F_DYNAMIC)) DESTROY(sl);
98fdb08d 360 dstr_destroy(&d);
42da2a58 361 return (0);
b9066fbb 362}
363
42da2a58 364/* --- @t_ifname@ --- *
b9066fbb 365 *
366 * Arguments: @tunnel *t@ = pointer to tunnel block
367 *
368 * Returns: A pointer to the tunnel's interface name.
369 */
370
42da2a58 371static const char *t_ifname(tunnel *t) { return (t->sl->name); }
b9066fbb 372
42da2a58 373/* --- @t_inject@ --- *
b9066fbb 374 *
375 * Arguments: @tunnel *t@ = pointer to tunnel block
376 * @buf *b@ = buffer to send
377 *
378 * Returns: ---
379 *
380 * Use: Injects a packet into the local network stack.
381 */
382
42da2a58 383static void t_inject(tunnel *t, buf *b)
b9066fbb 384{
385 octet buf[PKBUFSZ * 2 + 2];
386 const octet *p, *l;
387 octet *q;
388
389 IF_TRACING(T_TUNNEL, {
390 trace(T_TUNNEL, "tunnel: inject decrypted packet");
391 trace_block(T_PACKET, "tunnel: packet contents", BBASE(b), BLEN(b));
392 })
393
394 q = buf;
395 *q++ = SL_END;
396 for (p = BBASE(b), l = BCUR(b); p < l; p++) {
397 switch (*p) {
398 case SL_END: *q++ = SL_ESC; *q++ = SL_ESCEND; break;
399 case SL_ESC: *q++ = SL_ESC; *q++ = SL_ESCESC; break;
400 default: *q++ = *p; break;
401 }
402 }
403 *q++ = SL_END;
404 IF_TRACING(T_TUNNEL, {
405 trace_block(T_PACKET, "tunnel: SLIP-encapsulated contents",
406 buf, q - buf);
407 })
408 write(t->sl->ofd, buf, q - buf);
409}
410
42da2a58 411/* --- @t_destroy@ --- *
b9066fbb 412 *
413 * Arguments: @tunnel *t@ = pointer to tunnel block
414 *
415 * Returns: ---
416 *
417 * Use: Destroys a tunnel.
418 */
419
42da2a58 420static void t_destroy(tunnel *t)
b9066fbb 421{
98fdb08d 422 slipif *sl = t->sl;
423
b9066fbb 424 /* --- If it reported EOF, leave it out-of-action --- */
425
42da2a58 426 if (!(t->st & ST_EOF)) {
b9066fbb 427 sel_rmfile(&t->f);
42da2a58 428 sl->f &= ~F_INUSE;
98fdb08d 429 }
42da2a58 430 if (sl && (sl->f & F_DYNAMIC)) {
98fdb08d 431 T( trace(T_TUNNEL, "tunnel: releasing dynamic slipif %s", sl->name); )
432 close(sl->ofd);
433 close(sl->ifd);
434 kill(sl->kid, SIGTERM);
435 xfree(sl->name);
436 DESTROY(sl);
b9066fbb 437 }
42da2a58 438 DESTROY(t);
b9066fbb 439}
440
42da2a58 441const tunnel_ops tun_slip = {
442 "slip",
443 t_init,
444 t_create,
445 t_ifname,
446 t_inject,
447 t_destroy
448};
449
b9066fbb 450/*----- That's all, folks -------------------------------------------------*/