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 it under
13 * the terms of the GNU General Public License as published by the Free
14 * Software Foundation; either version 3 of the License, or (at your
15 * option) any later version.
17 * TrIPE is distributed in the hope that it will be useful, but WITHOUT
18 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
19 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
22 * You should have received a copy of the GNU General Public License
23 * along with TrIPE. If not, see <https://www.gnu.org/licenses/>.
26 /*----- Header files ------------------------------------------------------*/
32 /*----- Data structures ---------------------------------------------------*/
34 typedef struct slipif
{
35 struct slipif
*next
; /* Next one in the list */
36 int ifd
, ofd
; /* File descriptors to talk on */
37 char *name
; /* Interface name */
38 pid_t kid
; /* Child process id */
39 unsigned f
; /* Various flags */
40 # define F_INUSE 1u /* Interface is in use */
41 # define F_DYNAMIC 2u /* Interface found dynamically */
45 const tunnel_ops
*ops
; /* Pointer to operations */
46 slipif
*sl
; /* My interface record */
47 sel_file f
; /* Selector for SLIP tty */
48 struct peer
*p
; /* Pointer to my peer */
49 unsigned st
; /* Current parser state */
50 # define ST_ESC 1u /* Last saw an escape character */
51 # define ST_BAD 2u /* This packet is malformed */
52 # define ST_MASK 3u /* Mask for the above bits */
53 # define ST_EOF 4u /* File descriptor reported EOF */
54 # define ST_BROKEN 8u /* Sending side is broken */
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
);
126 } else if (q
== t
->buf
) {
127 T( trace(T_TUNNEL
, "tun-slip: empty packet"); )
129 IF_TRACING(T_TUNNEL
, {
130 trace(T_TUNNEL
, "tun-slip: packet arrived");
131 trace_block(T_PACKET
, "tun-slip: packet contents",
134 buf_init(&b
, t
->buf
, q
- t
->buf
);
141 if ((st
& ST_ESC
) && !(st
& ST_BAD
)) {
142 a_warn("TUN", "%s", p_ifname(t
->p
), "slip", "bad-escape", A_END
);
156 if ((st
& ST_ESC
) && !(st
& ST_BAD
)) {
157 a_warn("TUN", "%s", p_ifname(t
->p
), "slip", "bad-escape", A_END
);
161 if (!(st
& ST_BAD
)) {
165 a_warn("TUN", "%s", p_ifname(t
->p
), "slip", "overflow", A_END
);
178 /* --- @t_init@ --- *
182 * Returns: Zero on success, @-1@ on failure.
184 * Use: Initializes the tunneling system. Maybe this will require
185 * opening file descriptors or something.
188 static int t_init(void)
192 slipif
*sl
, **tail
= &slipifs
;
193 unsigned long uli
, ulo
;
196 if ((p
= getenv("TRIPE_SLIPIF")) == 0)
199 /* --- Build the list of available interfaces --- */
205 if (*p
== '/' || *p
== '.') {
207 T( trace(T_TUNNEL
, "tun-slip: declared slip command `%s'", slipcmd
); )
210 uli
= strtoul(p
, &q
, 0);
211 if (uli
> INT_MAX
|| q
== p
)
217 ulo
= strtoul(p
, &q
, 0);
218 if (ulo
> INT_MAX
|| q
== p
)
221 if (*q
!= '=' || (n
= strcspn(q
+ 1, ":")) == 0)
226 fdflags(sl
->ifd
, O_NONBLOCK
, O_NONBLOCK
, FD_CLOEXEC
, FD_CLOEXEC
);
227 fdflags(sl
->ofd
, O_NONBLOCK
, 0, FD_CLOEXEC
, FD_CLOEXEC
);
229 sl
->name
= xmalloc(n
+ 1);
232 memcpy(sl
->name
, q
+ 1, n
);
236 T( trace(T_TUNNEL
, "tun-slip: declared slipif %d,%d=%s",
237 sl
->ifd
, sl
->ofd
, sl
->name
); )
246 a_warn("TUN", "-", "slip", "bad-interface-list", A_END
);
250 /* --- @t_broken@ --- *
252 * Arguments: @tunnel *t@ = pointer to the tunnel
256 * Use: Marks the tunnel as broken and reports an error.
259 static void t_broken(tunnel
*t
)
261 if (errno
== EINTR
||
262 #if defined(EWOULDBLOCK) && EWOULDBLOCK != EAGAIN
263 errno
== EWOULDBLOCK
||
267 a_warn("TUN", "%s", p_ifname(t
->p
), "slip",
268 "write-error", "?ERRNO", A_END
);
269 T( trace(T_TUNNEL
, "tun-slip: marking tunnel broken"); )
273 /* --- @t_create@ --- *
275 * Arguments: @peer *p@ = pointer to peer block
276 * @int fd@ = file descriptor of tunnel device (unused)
277 * @char **ifn@ = where to put the interface name
279 * Returns: A tunnel block if it worked, or null on failure.
281 * Use: Initializes a new tunnel.
284 static tunnel
*t_create(peer
*p
, int fd
, char **ifn
)
287 int pin
[2] = { -1, -1 }, pout
[2] = { -1, -1 };
293 static const octet end
[] = { SL_END
, SL_END
};
295 /* --- Try to find a spare static interface --- */
297 for (sl
= slipifs
; sl
; sl
= sl
->next
) {
298 if (!(sl
->f
& F_INUSE
)) {
299 T( trace(T_TUNNEL
, "tun-slip: %s using static slipif %s",
300 p_name(p
), sl
->name
); )
305 /* --- If no dynamic interfaces are available, give up --- */
308 a_warn("TUN", "-", "slip", "no-slip-interfaces", A_END
);
312 /* --- Fork off a child process to create a dynamic SLIP interface --- */
314 if (pipe(pin
) || pipe(pout
)) {
315 a_warn("TUN", "-", "slip", "pipe-error", "?ERRNO", A_END
);
318 if ((kid
= fork()) < 0) {
319 a_warn("TUN", "-", "slip", "fork-error", "?ERRNO", A_END
);
323 close(pin
[1]); close(pout
[0]);
324 md
[0].cur
= pin
[0]; md
[0].want
= STDIN_FILENO
;
325 md
[1].cur
= pout
[1]; md
[1].want
= STDOUT_FILENO
;
327 execlp(slipcmd
, slipcmd
, p_name(p
), (char *)0);
331 /* --- Read the interface name --- */
334 close(pin
[0]); pin
[0] = -1;
335 close(pout
[1]); pout
[1] = -1;
338 if (read(pout
[0], &ch
, 1) != 1 || ch
== SL_END
) {
339 a_warn("TUN", "-", "slip", "read-ifname-failed", "?ERRNO", A_END
);
347 sl
->name
= xstrdup(d
.buf
);
353 T( trace(T_TUNNEL
, "tun-slip: %s using dynamic slipif %s",
354 p_name(p
), sl
->name
); )
355 fdflags(pout
[0], O_NONBLOCK
, O_NONBLOCK
, FD_CLOEXEC
, FD_CLOEXEC
);
356 fdflags(pin
[1], O_NONBLOCK
, 0, FD_CLOEXEC
, FD_CLOEXEC
);
358 /* --- Set up the new tunnel --- */
368 sel_initfile(&sel
, &t
->f
, sl
->ifd
, SEL_READ
, t_read
, t
);
370 if (write(sl
->ofd
, end
, sizeof(end
)) < 0)
372 *ifn
= xstrdup(sl
->name
);
376 /* --- Tidy up after a failure --- */
379 #define CLOSE(fd) do if (fd != -1) close(fd); while (0)
380 CLOSE(pin
[0]); CLOSE(pout
[0]);
381 CLOSE(pin
[1]); CLOSE(pout
[1]);
383 if (kid
!= -1) kill(kid
, SIGTERM
);
384 if (sl
&& (sl
->f
& F_DYNAMIC
)) DESTROY(sl
);
389 /* --- @t_setifname@ --- *
391 * Arguments: @tunnel *t@ = pointer to tunnel block
392 * @const char *ifn@ = new interface name
396 * Use: Updates the interface name of a slip interface.
399 static void t_setifname(tunnel
*t
, const char *ifn
)
400 { xfree(t
->sl
->name
); t
->sl
->name
= xstrdup(ifn
); }
402 /* --- @t_inject@ --- *
404 * Arguments: @tunnel *t@ = pointer to tunnel block
405 * @buf *b@ = buffer to send
409 * Use: Injects a packet into the local network stack.
412 static void t_inject(tunnel
*t
, buf
*b
)
414 octet buf
[PKBUFSZ
* 2 + 2];
418 IF_TRACING(T_TUNNEL
, {
419 trace(T_TUNNEL
, "tun-slip: inject decrypted packet");
420 trace_block(T_PACKET
, "tun-slip: packet contents", BBASE(b
), BLEN(b
));
423 if (t
-> st
& ST_BROKEN
) {
424 T( trace(T_TUNNEL
, "tun-slip: tunnel broken; discarding"); )
429 for (p
= BBASE(b
), l
= BCUR(b
); p
< l
; p
++) {
431 case SL_END
: *q
++ = SL_ESC
; *q
++ = SL_ESCEND
; break;
432 case SL_ESC
: *q
++ = SL_ESC
; *q
++ = SL_ESCESC
; break;
433 default: *q
++ = *p
; break;
437 IF_TRACING(T_TUNNEL
, {
438 trace_block(T_PACKET
, "tun-slip: SLIP-encapsulated contents",
441 if (write(t
->sl
->ofd
, buf
, q
- buf
) < 0)
445 /* --- @t_destroy@ --- *
447 * Arguments: @tunnel *t@ = pointer to tunnel block
451 * Use: Destroys a tunnel.
454 static void t_destroy(tunnel
*t
)
458 /* --- If it reported EOF, leave it out-of-action --- */
460 if (!(t
->st
& ST_EOF
)) {
464 if (sl
&& (sl
->f
& F_DYNAMIC
)) {
465 T( trace(T_TUNNEL
, "tun-slip: releasing dynamic slipif %s", sl
->name
); )
468 kill(sl
->kid
, SIGTERM
);
475 const tunnel_ops tun_slip
= {
485 /*----- That's all, folks -------------------------------------------------*/