xref: /freebsd/lib/libc/net/ip6opt.c (revision 031beb4e239bfce798af17f5fe8dba8bcaf13d99)
1 /*	$KAME: ip6opt.c,v 1.13 2003/06/06 10:08:20 suz Exp $	*/
2 
3 /*-
4  * SPDX-License-Identifier: BSD-3-Clause
5  *
6  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
7  * All rights reserved.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  * 3. Neither the name of the project nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  */
33 
34 #include <sys/cdefs.h>
35 #include <sys/param.h>
36 #include <sys/socket.h>
37 
38 #include <netinet/in.h>
39 #include <netinet/ip6.h>
40 
41 #include <string.h>
42 #include <stdio.h>
43 
44 static int ip6optlen(u_int8_t *opt, u_int8_t *lim);
45 static void inet6_insert_padopt(u_char *p, int len);
46 
47 #ifndef IPV6_2292HOPOPTS
48 #define	IPV6_2292HOPOPTS	22
49 #endif
50 #ifndef IPV6_2292DSTOPTS
51 #define	IPV6_2292DSTOPTS	23
52 #endif
53 
54 #define	is_ipv6_hopopts(x)	\
55 	((x) == IPV6_HOPOPTS || (x) == IPV6_2292HOPOPTS)
56 #define	is_ipv6_dstopts(x)	\
57 	((x) == IPV6_DSTOPTS || (x) == IPV6_2292DSTOPTS)
58 
59 /*
60  * This function returns the number of bytes required to hold an option
61  * when it is stored as ancillary data, including the cmsghdr structure
62  * at the beginning, and any padding at the end (to make its size a
63  * multiple of 8 bytes).  The argument is the size of the structure
64  * defining the option, which must include any pad bytes at the
65  * beginning (the value y in the alignment term "xn + y"), the type
66  * byte, the length byte, and the option data.
67  */
68 int
69 inet6_option_space(int nbytes)
70 {
71 	nbytes += 2;	/* we need space for nxt-hdr and length fields */
72 	return(CMSG_SPACE((nbytes + 7) & ~7));
73 }
74 
75 /*
76  * This function is called once per ancillary data object that will
77  * contain either Hop-by-Hop or Destination options.  It returns 0 on
78  * success or -1 on an error.
79  */
80 int
81 inet6_option_init(void *bp, struct cmsghdr **cmsgp, int type)
82 {
83 	struct cmsghdr *ch = (struct cmsghdr *)bp;
84 
85 	/* argument validation */
86 	if (!is_ipv6_hopopts(type) && !is_ipv6_dstopts(type))
87 		return(-1);
88 
89 	ch->cmsg_level = IPPROTO_IPV6;
90 	ch->cmsg_type = type;
91 	ch->cmsg_len = CMSG_LEN(0);
92 
93 	*cmsgp = ch;
94 	return(0);
95 }
96 
97 /*
98  * This function appends a Hop-by-Hop option or a Destination option
99  * into an ancillary data object that has been initialized by
100  * inet6_option_init().  This function returns 0 if it succeeds or -1 on
101  * an error.
102  * multx is the value x in the alignment term "xn + y" described
103  * earlier.  It must have a value of 1, 2, 4, or 8.
104  * plusy is the value y in the alignment term "xn + y" described
105  * earlier.  It must have a value between 0 and 7, inclusive.
106  */
107 int
108 inet6_option_append(struct cmsghdr *cmsg, const u_int8_t *typep, int multx,
109     int plusy)
110 {
111 	int padlen, optlen, off;
112 	u_char *bp = (u_char *)cmsg + cmsg->cmsg_len;
113 	struct ip6_ext *eh = (struct ip6_ext *)CMSG_DATA(cmsg);
114 
115 	/* argument validation */
116 	if (multx != 1 && multx != 2 && multx != 4 && multx != 8)
117 		return(-1);
118 	if (plusy < 0 || plusy > 7)
119 		return(-1);
120 
121 	/*
122 	 * If this is the first option, allocate space for the
123 	 * first 2 bytes(for next header and length fields) of
124 	 * the option header.
125 	 */
126 	if (bp == (u_char *)eh) {
127 		bp += 2;
128 		cmsg->cmsg_len += 2;
129 	}
130 
131 	/* calculate pad length before the option. */
132 	off = bp - (u_char *)eh;
133 	padlen = roundup2(off % multx, multx) - (off % multx);
134 	padlen += plusy;
135 	padlen %= multx;	/* keep the pad as short as possible */
136 	/* insert padding */
137 	inet6_insert_padopt(bp, padlen);
138 	cmsg->cmsg_len += padlen;
139 	bp += padlen;
140 
141 	/* copy the option */
142 	if (typep[0] == IP6OPT_PAD1)
143 		optlen = 1;
144 	else
145 		optlen = typep[1] + 2;
146 	memcpy(bp, typep, optlen);
147 	bp += optlen;
148 	cmsg->cmsg_len += optlen;
149 
150 	/* calculate pad length after the option and insert the padding */
151 	off = bp - (u_char *)eh;
152 	padlen = ((off + 7) & ~7) - off;
153 	inet6_insert_padopt(bp, padlen);
154 	bp += padlen;
155 	cmsg->cmsg_len += padlen;
156 
157 	/* update the length field of the ip6 option header */
158 	eh->ip6e_len = ((bp - (u_char *)eh) >> 3) - 1;
159 
160 	return(0);
161 }
162 
163 /*
164  * This function appends a Hop-by-Hop option or a Destination option
165  * into an ancillary data object that has been initialized by
166  * inet6_option_init().  This function returns a pointer to the 8-bit
167  * option type field that starts the option on success, or NULL on an
168  * error.
169  * The difference between this function and inet6_option_append() is
170  * that the latter copies the contents of a previously built option into
171  * the ancillary data object while the current function returns a
172  * pointer to the space in the data object where the option's TLV must
173  * then be built by the caller.
174  *
175  */
176 u_int8_t *
177 inet6_option_alloc(struct cmsghdr *cmsg, int datalen, int multx, int plusy)
178 {
179 	int padlen, off;
180 	u_int8_t *bp = (u_char *)cmsg + cmsg->cmsg_len;
181 	u_int8_t *retval;
182 	struct ip6_ext *eh = (struct ip6_ext *)CMSG_DATA(cmsg);
183 
184 	/* argument validation */
185 	if (multx != 1 && multx != 2 && multx != 4 && multx != 8)
186 		return(NULL);
187 	if (plusy < 0 || plusy > 7)
188 		return(NULL);
189 
190 	/*
191 	 * If this is the first option, allocate space for the
192 	 * first 2 bytes(for next header and length fields) of
193 	 * the option header.
194 	 */
195 	if (bp == (u_char *)eh) {
196 		bp += 2;
197 		cmsg->cmsg_len += 2;
198 	}
199 
200 	/* calculate pad length before the option. */
201 	off = bp - (u_char *)eh;
202 	padlen = roundup2(off % multx, multx) - (off % multx);
203 	padlen += plusy;
204 	padlen %= multx;	/* keep the pad as short as possible */
205 	/* insert padding */
206 	inet6_insert_padopt(bp, padlen);
207 	cmsg->cmsg_len += padlen;
208 	bp += padlen;
209 
210 	/* keep space to store specified length of data */
211 	retval = bp;
212 	bp += datalen;
213 	cmsg->cmsg_len += datalen;
214 
215 	/* calculate pad length after the option and insert the padding */
216 	off = bp - (u_char *)eh;
217 	padlen = ((off + 7) & ~7) - off;
218 	inet6_insert_padopt(bp, padlen);
219 	bp += padlen;
220 	cmsg->cmsg_len += padlen;
221 
222 	/* update the length field of the ip6 option header */
223 	eh->ip6e_len = ((bp - (u_char *)eh) >> 3) - 1;
224 
225 	return(retval);
226 }
227 
228 /*
229  * This function processes the next Hop-by-Hop option or Destination
230  * option in an ancillary data object.  If another option remains to be
231  * processed, the return value of the function is 0 and *tptrp points to
232  * the 8-bit option type field (which is followed by the 8-bit option
233  * data length, followed by the option data).  If no more options remain
234  * to be processed, the return value is -1 and *tptrp is NULL.  If an
235  * error occurs, the return value is -1 and *tptrp is not NULL.
236  * (RFC 2292, 6.3.5)
237  */
238 int
239 inet6_option_next(const struct cmsghdr *cmsg, u_int8_t **tptrp)
240 {
241 	struct ip6_ext *ip6e;
242 	int hdrlen, optlen;
243 	u_int8_t *lim;
244 
245 	if (cmsg->cmsg_level != IPPROTO_IPV6 ||
246 	    (!is_ipv6_hopopts(cmsg->cmsg_type) &&
247 	     !is_ipv6_dstopts(cmsg->cmsg_type)))
248 		return(-1);
249 
250 	/* message length validation */
251 	if (cmsg->cmsg_len < CMSG_SPACE(sizeof(struct ip6_ext)))
252 		return(-1);
253 	ip6e = (struct ip6_ext *)CMSG_DATA(cmsg);
254 	hdrlen = (ip6e->ip6e_len + 1) << 3;
255 	if (cmsg->cmsg_len < CMSG_SPACE(hdrlen))
256 		return(-1);
257 
258 	/*
259 	 * If the caller does not specify the starting point,
260 	 * simply return the 1st option.
261 	 * Otherwise, search the option list for the next option.
262 	 */
263 	lim = (u_int8_t *)ip6e + hdrlen;
264 	if (*tptrp == NULL)
265 		*tptrp = (u_int8_t *)(ip6e + 1);
266 	else {
267 		if ((optlen = ip6optlen(*tptrp, lim)) == 0)
268 			return(-1);
269 
270 		*tptrp = *tptrp + optlen;
271 	}
272 	if (*tptrp >= lim) {	/* there is no option */
273 		*tptrp = NULL;
274 		return(-1);
275 	}
276 	/*
277 	 * Finally, checks if the next option is safely stored in the
278 	 * cmsg data.
279 	 */
280 	if (ip6optlen(*tptrp, lim) == 0)
281 		return(-1);
282 	else
283 		return(0);
284 }
285 
286 /*
287  * This function is similar to the inet6_option_next() function,
288  * except this function lets the caller specify the option type to be
289  * searched for, instead of always returning the next option in the
290  * ancillary data object.
291  * Note: RFC 2292 says the type of tptrp is u_int8_t *, but we think
292  *       it's a typo. The variable should be type of u_int8_t **.
293  */
294 int
295 inet6_option_find(const struct cmsghdr *cmsg, u_int8_t **tptrp, int type)
296 {
297 	struct ip6_ext *ip6e;
298 	int hdrlen, optlen;
299 	u_int8_t *optp, *lim;
300 
301 	if (cmsg->cmsg_level != IPPROTO_IPV6 ||
302 	    (!is_ipv6_hopopts(cmsg->cmsg_type) &&
303 	     !is_ipv6_dstopts(cmsg->cmsg_type)))
304 		return(-1);
305 
306 	/* message length validation */
307 	if (cmsg->cmsg_len < CMSG_SPACE(sizeof(struct ip6_ext)))
308 		return(-1);
309 	ip6e = (struct ip6_ext *)CMSG_DATA(cmsg);
310 	hdrlen = (ip6e->ip6e_len + 1) << 3;
311 	if (cmsg->cmsg_len < CMSG_SPACE(hdrlen))
312 		return(-1);
313 
314 	/*
315 	 * If the caller does not specify the starting point,
316 	 * search from the beginning of the option list.
317 	 * Otherwise, search from *the next option* of the specified point.
318 	 */
319 	lim = (u_int8_t *)ip6e + hdrlen;
320 	if (*tptrp == NULL)
321 		*tptrp = (u_int8_t *)(ip6e + 1);
322 	else {
323 		if ((optlen = ip6optlen(*tptrp, lim)) == 0)
324 			return(-1);
325 
326 		*tptrp = *tptrp + optlen;
327 	}
328 	for (optp = *tptrp; optp < lim; optp += optlen) {
329 		if (*optp == type) {
330 			*tptrp = optp;
331 			return(0);
332 		}
333 		if ((optlen = ip6optlen(optp, lim)) == 0)
334 			return(-1);
335 	}
336 
337 	/* search failed */
338 	*tptrp = NULL;
339 	return(-1);
340 }
341 
342 /*
343  * Calculate the length of a given IPv6 option. Also checks
344  * if the option is safely stored in user's buffer according to the
345  * calculated length and the limitation of the buffer.
346  */
347 static int
348 ip6optlen(u_int8_t *opt, u_int8_t *lim)
349 {
350 	int optlen;
351 
352 	if (*opt == IP6OPT_PAD1)
353 		optlen = 1;
354 	else {
355 		/* is there enough space to store type and len? */
356 		if (opt + 2 > lim)
357 			return(0);
358 		optlen = *(opt + 1) + 2;
359 	}
360 	if (opt + optlen <= lim)
361 		return(optlen);
362 
363 	return(0);
364 }
365 
366 static void
367 inet6_insert_padopt(u_char *p, int len)
368 {
369 	switch(len) {
370 	 case 0:
371 		 return;
372 	 case 1:
373 		 p[0] = IP6OPT_PAD1;
374 		 return;
375 	 default:
376 		 p[0] = IP6OPT_PADN;
377 		 p[1] = len - 2;
378 		 memset(&p[2], 0, len - 2);
379 		 return;
380 	}
381 }
382 
383 /*
384  * The following functions are defined in RFC3542, which is a successor
385  * of RFC2292.
386  */
387 
388 int
389 inet6_opt_init(void *extbuf, socklen_t extlen)
390 {
391 	struct ip6_ext *ext = (struct ip6_ext *)extbuf;
392 
393 	if (ext) {
394 		if (extlen <= 0 || (extlen % 8))
395 			return(-1);
396 		ext->ip6e_len = (extlen >> 3) - 1;
397 	}
398 
399 	return(2);		/* sizeof the next and the length fields */
400 }
401 
402 int
403 inet6_opt_append(void *extbuf, socklen_t extlen, int offset, u_int8_t type,
404 		 socklen_t len, u_int8_t align, void **databufp)
405 {
406 	int currentlen = offset, padlen = 0;
407 
408 	/*
409 	 * The option type must have a value from 2 to 255, inclusive.
410 	 * (0 and 1 are reserved for the Pad1 and PadN options, respectively.)
411 	 */
412 	if (type < 2)
413 		return(-1);
414 
415 	/*
416 	 * The option data length must have a value between 0 and 255,
417 	 * inclusive, and is the length of the option data that follows.
418 	 */
419 	if (len > 255 || len < 0 )
420 		return(-1);
421 
422 	/*
423 	 * The align parameter must have a value of 1, 2, 4, or 8.
424 	 * The align value can not exceed the value of len.
425 	 */
426 	if (align != 1 && align != 2 && align != 4 && align != 8)
427 		return(-1);
428 	if (align > len)
429 		return(-1);
430 
431 	/* Calculate the padding length. */
432 	currentlen += 2 + len;	/* 2 means "type + len" */
433 	if (currentlen % align)
434 		padlen = align - (currentlen % align);
435 
436 	/* The option must fit in the extension header buffer. */
437 	currentlen += padlen;
438 	if (extlen &&		/* XXX: right? */
439 	    currentlen > extlen)
440 		return(-1);
441 
442 	if (extbuf) {
443 		u_int8_t *optp = (u_int8_t *)extbuf + offset;
444 
445 		if (padlen == 1) {
446 			/* insert a Pad1 option */
447 			*optp = IP6OPT_PAD1;
448 			optp++;
449 		}
450 		else if (padlen > 0) {
451 			/* insert a PadN option for alignment */
452 			*optp++ = IP6OPT_PADN;
453 			*optp++ = padlen - 2;
454 			memset(optp, 0, padlen - 2);
455 			optp += (padlen - 2);
456 		}
457 
458 		*optp++ = type;
459 		*optp++ = len;
460 
461 		*databufp = optp;
462 	}
463 
464 	return(currentlen);
465 }
466 
467 int
468 inet6_opt_finish(void *extbuf, socklen_t extlen, int offset)
469 {
470 	int updatelen = offset > 0 ? (1 + ((offset - 1) | 7)) : 0;
471 
472 	if (extbuf) {
473 		u_int8_t *padp;
474 		int padlen = updatelen - offset;
475 
476 		if (updatelen > extlen)
477 			return(-1);
478 
479 		padp = (u_int8_t *)extbuf + offset;
480 		if (padlen == 1)
481 			*padp = IP6OPT_PAD1;
482 		else if (padlen > 0) {
483 			*padp++ = IP6OPT_PADN;
484 			*padp++ = (padlen - 2);
485 			memset(padp, 0, padlen - 2);
486 		}
487 	}
488 
489 	return(updatelen);
490 }
491 
492 int
493 inet6_opt_set_val(void *databuf, int offset, void *val, socklen_t vallen)
494 {
495 
496 	memcpy((u_int8_t *)databuf + offset, val, vallen);
497 	return(offset + vallen);
498 }
499 
500 int
501 inet6_opt_next(void *extbuf, socklen_t extlen, int offset, u_int8_t *typep,
502 	       socklen_t *lenp, void **databufp)
503 {
504 	u_int8_t *optp, *lim;
505 	int optlen;
506 
507 	/* Validate extlen. XXX: is the variable really necessary?? */
508 	if (extlen == 0 || (extlen % 8))
509 		return(-1);
510 	lim = (u_int8_t *)extbuf + extlen;
511 
512 	/*
513 	 * If this is the first time this function called for this options
514 	 * header, simply return the 1st option.
515 	 * Otherwise, search the option list for the next option.
516 	 */
517 	if (offset == 0) {
518 		optp = (u_int8_t *)((struct ip6_hbh *)extbuf + 1);
519 	}
520 	else
521 		optp = (u_int8_t *)extbuf + offset;
522 
523 	/* Find the next option skipping any padding options. */
524 	while(optp < lim) {
525 		switch(*optp) {
526 		case IP6OPT_PAD1:
527 			optp++;
528 			break;
529 		case IP6OPT_PADN:
530 			if ((optlen = ip6optlen(optp, lim)) == 0)
531 				goto optend;
532 			optp += optlen;
533 			break;
534 		default:	/* found */
535 			if ((optlen = ip6optlen(optp, lim)) == 0)
536 				goto optend;
537 			*typep = *optp;
538 			*lenp = optlen - 2;
539 			*databufp = optp + 2;
540 			return(optp + optlen - (u_int8_t *)extbuf);
541 		}
542 	}
543 
544   optend:
545 	*databufp = NULL; /* for safety */
546 	return(-1);
547 }
548 
549 int
550 inet6_opt_find(void *extbuf, socklen_t extlen, int offset, u_int8_t type,
551 	       socklen_t *lenp, void **databufp)
552 {
553 	u_int8_t *optp, *lim;
554 	int optlen;
555 
556 	/* Validate extlen. XXX: is the variable really necessary?? */
557 	if (extlen == 0 || (extlen % 8))
558 		return(-1);
559 	lim = (u_int8_t *)extbuf + extlen;
560 
561 	/*
562 	 * If this is the first time this function called for this options
563 	 * header, simply return the 1st option.
564 	 * Otherwise, search the option list for the next option.
565 	 */
566 	if (offset == 0) {
567 		optp = (u_int8_t *)((struct ip6_hbh *)extbuf + 1);
568 	}
569 	else
570 		optp = (u_int8_t *)extbuf + offset;
571 
572 	/* Find the specified option */
573 	while(optp < lim) {
574 		if ((optlen = ip6optlen(optp, lim)) == 0)
575 			goto optend;
576 
577 		if (*optp == type) { /* found */
578 			*lenp = optlen - 2;
579 			*databufp = optp + 2;
580 			return(optp + optlen - (u_int8_t *)extbuf);
581 		}
582 
583 		optp += optlen;
584 	}
585 
586   optend:
587 	*databufp = NULL; /* for safety */
588 	return(-1);
589 }
590 
591 int
592 inet6_opt_get_val(void *databuf, int offset, void *val, socklen_t vallen)
593 {
594 
595 	/* we can't assume alignment here */
596 	memcpy(val, (u_int8_t *)databuf + offset, vallen);
597 
598 	return(offset + vallen);
599 }
600