ip6opt.c revision 1.7 1 /* $NetBSD: ip6opt.c,v 1.7 2000/04/24 10:40:25 itojun Exp $ */
2
3 /*
4 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. Neither the name of the project nor the names of its contributors
16 * may be used to endorse or promote products derived from this software
17 * without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31
32 #include <sys/cdefs.h>
33 #if defined(LIBC_SCCS) && !defined(lint)
34 __RCSID("$NetBSD: ip6opt.c,v 1.7 2000/04/24 10:40:25 itojun Exp $");
35 #endif /* LIBC_SCCS and not lint */
36
37 #include "namespace.h"
38 #include <sys/param.h>
39 #include <sys/types.h>
40 #include <sys/socket.h>
41
42 #include <netinet/in.h>
43 #include <netinet/ip6.h>
44
45 #include <assert.h>
46 #include <string.h>
47 #include <stdio.h>
48
49 #ifdef __weak_alias
50 __weak_alias(inet6_option_alloc,_inet6_option_alloc)
51 __weak_alias(inet6_option_append,_inet6_option_append)
52 __weak_alias(inet6_option_find,_inet6_option_find)
53 __weak_alias(inet6_option_init,_inet6_option_init)
54 __weak_alias(inet6_option_next,_inet6_option_next)
55 __weak_alias(inet6_option_space,_inet6_option_space)
56 #endif
57
58 static int ip6optlen(u_int8_t *opt, u_int8_t *lim);
59 static void inet6_insert_padopt(u_char *p, size_t len);
60
61 /*
62 * This function returns the number of bytes required to hold an option
63 * when it is stored as ancillary data, including the cmsghdr structure
64 * at the beginning, and any padding at the end (to make its size a
65 * multiple of 8 bytes). The argument is the size of the structure
66 * defining the option, which must include any pad bytes at the
67 * beginning (the value y in the alignment term "xn + y"), the type
68 * byte, the length byte, and the option data.
69 */
70 int
71 inet6_option_space(nbytes)
72 int nbytes;
73 {
74 nbytes += 2; /* we need space for nxt-hdr and length fields */
75 return(CMSG_SPACE((nbytes + 7) & ~7));
76 }
77
78 /*
79 * This function is called once per ancillary data object that will
80 * contain either Hop-by-Hop or Destination options. It returns 0 on
81 * success or -1 on an error.
82 */
83 int
84 inet6_option_init(bp, cmsgp, type)
85 void *bp;
86 struct cmsghdr **cmsgp;
87 int type;
88 {
89 register struct cmsghdr *ch;
90
91 _DIAGASSERT(bp != NULL);
92 _DIAGASSERT(cmsgp != NULL);
93
94 ch = (struct cmsghdr *)bp;
95
96 /* argument validation */
97 if (type != IPV6_HOPOPTS && type != IPV6_DSTOPTS)
98 return(-1);
99
100 ch->cmsg_level = IPPROTO_IPV6;
101 ch->cmsg_type = type;
102 ch->cmsg_len = CMSG_LEN(0);
103
104 *cmsgp = ch;
105 return(0);
106 }
107
108 /*
109 * This function appends a Hop-by-Hop option or a Destination option
110 * into an ancillary data object that has been initialized by
111 * inet6_option_init(). This function returns 0 if it succeeds or -1 on
112 * an error.
113 * multx is the value x in the alignment term "xn + y" described
114 * earlier. It must have a value of 1, 2, 4, or 8.
115 * plusy is the value y in the alignment term "xn + y" described
116 * earlier. It must have a value between 0 and 7, inclusive.
117 */
118 int
119 inet6_option_append(cmsg, typep, multx, plusy)
120 struct cmsghdr *cmsg;
121 const u_int8_t *typep;
122 int multx;
123 int plusy;
124 {
125 size_t padlen, optlen, off;
126 register u_char *bp;
127 struct ip6_ext *eh;
128
129 _DIAGASSERT(cmsg != NULL);
130 _DIAGASSERT(typep != NULL);
131
132 bp = (u_char *)cmsg + cmsg->cmsg_len;
133 eh = (struct ip6_ext *)CMSG_DATA(cmsg);
134
135 /* argument validation */
136 if (multx != 1 && multx != 2 && multx != 4 && multx != 8)
137 return(-1);
138 if (plusy < 0 || plusy > 7)
139 return(-1);
140 if (typep[0] > 255)
141 return(-1);
142
143 /*
144 * If this is the first option, allocate space for the
145 * first 2 bytes(for next header and length fields) of
146 * the option header.
147 */
148 if (bp == (u_char *)eh) {
149 bp += 2;
150 cmsg->cmsg_len += 2;
151 }
152
153 /* calculate pad length before the option. */
154 off = bp - (u_char *)eh;
155 padlen = (((off % multx) + (multx - 1)) & ~(multx - 1)) -
156 (off % multx);
157 padlen += plusy;
158 /* insert padding */
159 inet6_insert_padopt(bp, padlen);
160 cmsg->cmsg_len += padlen;
161 bp += padlen;
162
163 /* copy the option */
164 if (typep[0] == IP6OPT_PAD1)
165 optlen = 1;
166 else
167 optlen = typep[1] + 2;
168 memcpy(bp, typep, (size_t)optlen);
169 bp += optlen;
170 cmsg->cmsg_len += optlen;
171
172 /* calculate pad length after the option and insert the padding */
173 off = bp - (u_char *)eh;
174 padlen = ((off + 7) & ~7) - off;
175 inet6_insert_padopt(bp, padlen);
176 bp += padlen;
177 cmsg->cmsg_len += padlen;
178
179 /* update the length field of the ip6 option header */
180 off = bp - (u_char *)eh;
181 eh->ip6e_len = (off >> 3) - 1;
182
183 return(0);
184 }
185
186 /*
187 * This function appends a Hop-by-Hop option or a Destination option
188 * into an ancillary data object that has been initialized by
189 * inet6_option_init(). This function returns a pointer to the 8-bit
190 * option type field that starts the option on success, or NULL on an
191 * error.
192 * The difference between this function and inet6_option_append() is
193 * that the latter copies the contents of a previously built option into
194 * the ancillary data object while the current function returns a
195 * pointer to the space in the data object where the option's TLV must
196 * then be built by the caller.
197 *
198 */
199 u_int8_t *
200 inet6_option_alloc(cmsg, datalen, multx, plusy)
201 struct cmsghdr *cmsg;
202 int datalen;
203 int multx;
204 int plusy;
205 {
206 size_t padlen, off;
207 register u_int8_t *bp;
208 u_int8_t *retval;
209 struct ip6_ext *eh;
210
211 _DIAGASSERT(cmsg != NULL);
212
213 bp = (u_char *)cmsg + cmsg->cmsg_len;
214 eh = (struct ip6_ext *)CMSG_DATA(cmsg);
215
216 /* argument validation */
217 if (multx != 1 && multx != 2 && multx != 4 && multx != 8)
218 return(NULL);
219 if (plusy < 0 || plusy > 7)
220 return(NULL);
221
222 /*
223 * If this is the first option, allocate space for the
224 * first 2 bytes(for next header and length fields) of
225 * the option header.
226 */
227 if (bp == (u_char *)eh) {
228 bp += 2;
229 cmsg->cmsg_len += 2;
230 }
231
232 /* calculate pad length before the option. */
233 off = bp - (u_char *)eh;
234 padlen = (((off % multx) + (multx - 1)) & ~(multx - 1)) -
235 (off % multx);
236 padlen += plusy;
237 /* insert padding */
238 inet6_insert_padopt(bp, padlen);
239 cmsg->cmsg_len += padlen;
240 bp += padlen;
241
242 /* keep space to store specified length of data */
243 retval = bp;
244 bp += datalen;
245 cmsg->cmsg_len += datalen;
246
247 /* calculate pad length after the option and insert the padding */
248 off = bp - (u_char *)eh;
249 padlen = ((off + 7) & ~7) - off;
250 inet6_insert_padopt(bp, padlen);
251 bp += padlen;
252 cmsg->cmsg_len += padlen;
253
254 /* update the length field of the ip6 option header */
255 off = bp - (u_char *)eh;
256 eh->ip6e_len = (off >> 3) - 1;
257
258 return(retval);
259 }
260
261 /*
262 * This function processes the next Hop-by-Hop option or Destination
263 * option in an ancillary data object. If another option remains to be
264 * processed, the return value of the function is 0 and *tptrp points to
265 * the 8-bit option type field (which is followed by the 8-bit option
266 * data length, followed by the option data). If no more options remain
267 * to be processed, the return value is -1 and *tptrp is NULL. If an
268 * error occurs, the return value is -1 and *tptrp is not NULL.
269 * (RFC 2292, 6.3.5)
270 */
271 int
272 inet6_option_next(cmsg, tptrp)
273 const struct cmsghdr *cmsg;
274 u_int8_t **tptrp;
275 {
276 struct ip6_ext *ip6e;
277 int hdrlen, optlen;
278 u_int8_t *lim;
279
280 _DIAGASSERT(cmsg != NULL);
281 _DIAGASSERT(tptrp != NULL);
282
283 if (cmsg->cmsg_level != IPPROTO_IPV6 ||
284 (cmsg->cmsg_type != IPV6_HOPOPTS &&
285 cmsg->cmsg_type != IPV6_DSTOPTS))
286 return(-1);
287
288 /* message length validation */
289 if (cmsg->cmsg_len < CMSG_SPACE(sizeof(struct ip6_ext)))
290 return(-1);
291 ip6e = (struct ip6_ext *)CMSG_DATA(cmsg);
292 hdrlen = (ip6e->ip6e_len + 1) << 3;
293 if (cmsg->cmsg_len < CMSG_SPACE(hdrlen))
294 return(-1);
295
296 /*
297 * If the caller does not specify the starting point,
298 * simply return the 1st option.
299 * Otherwise, search the option list for the next option.
300 */
301 lim = (u_int8_t *)ip6e + hdrlen;
302 if (*tptrp == NULL)
303 *tptrp = (u_int8_t *)(ip6e + 1);
304 else {
305 if ((optlen = ip6optlen(*tptrp, lim)) == 0)
306 return(-1);
307
308 *tptrp = *tptrp + optlen;
309 }
310 if (*tptrp >= lim) { /* there is no option */
311 *tptrp = NULL;
312 return(-1);
313 }
314 /*
315 * Finally, checks if the next option is safely stored in the
316 * cmsg data.
317 */
318 if (ip6optlen(*tptrp, lim) == 0)
319 return(-1);
320 else
321 return(0);
322 }
323
324 /*
325 * This function is similar to the inet6_option_next() function,
326 * except this function lets the caller specify the option type to be
327 * searched for, instead of always returning the next option in the
328 * ancillary data object.
329 * Note: RFC 2292 says the type of tptrp is u_int8_t *, but we think
330 * it's a typo. The variable should be type of u_int8_t **.
331 */
332 int
333 inet6_option_find(cmsg, tptrp, type)
334 const struct cmsghdr *cmsg;
335 u_int8_t **tptrp;
336 int type;
337 {
338 struct ip6_ext *ip6e;
339 int hdrlen, optlen;
340 u_int8_t *optp, *lim;
341
342 _DIAGASSERT(cmsg != NULL);
343 _DIAGASSERT(tptrp != NULL);
344
345 if (cmsg->cmsg_level != IPPROTO_IPV6 ||
346 (cmsg->cmsg_type != IPV6_HOPOPTS &&
347 cmsg->cmsg_type != IPV6_DSTOPTS))
348 return(-1);
349
350 /* message length validation */
351 if (cmsg->cmsg_len < CMSG_SPACE(sizeof(struct ip6_ext)))
352 return(-1);
353 ip6e = (struct ip6_ext *)CMSG_DATA(cmsg);
354 hdrlen = (ip6e->ip6e_len + 1) << 3;
355 if (cmsg->cmsg_len < CMSG_SPACE(hdrlen))
356 return(-1);
357
358 /*
359 * If the caller does not specify the starting point,
360 * search from the beginning of the option list.
361 * Otherwise, search from *the next option* of the specified point.
362 */
363 lim = (u_int8_t *)ip6e + hdrlen;
364 if (*tptrp == NULL)
365 *tptrp = (u_int8_t *)(ip6e + 1);
366 else {
367 if ((optlen = ip6optlen(*tptrp, lim)) == 0)
368 return(-1);
369
370 *tptrp = *tptrp + optlen;
371 }
372 for (optp = *tptrp; optp < lim; optp += optlen) {
373 if (*optp == type) {
374 *tptrp = optp;
375 return(0);
376 }
377 if ((optlen = ip6optlen(optp, lim)) == 0)
378 return(-1);
379 }
380
381 /* search failed */
382 *tptrp = NULL;
383 return(-1);
384 }
385
386 /*
387 * Calculate the length of a given IPv6 option. Also checks
388 * if the option is safely stored in user's buffer according to the
389 * calculated length and the limitation of the buffer.
390 */
391 static int
392 ip6optlen(opt, lim)
393 u_int8_t *opt, *lim;
394 {
395 int optlen;
396
397 _DIAGASSERT(opt != NULL);
398 _DIAGASSERT(lim != NULL);
399
400 if (*opt == IP6OPT_PAD1)
401 optlen = 1;
402 else {
403 /* is there enough space to store type and len? */
404 if (opt + 2 > lim)
405 return(0);
406 optlen = *(opt + 1) + 2;
407 }
408 if (opt + optlen <= lim)
409 return(optlen);
410
411 return(0);
412 }
413
414 static void
415 inet6_insert_padopt(u_char *p, size_t len)
416 {
417
418 _DIAGASSERT(p != NULL);
419
420 switch(len) {
421 case 0:
422 return;
423 case 1:
424 p[0] = IP6OPT_PAD1;
425 return;
426 default:
427 p[0] = IP6OPT_PADN;
428 p[1] = len - 2;
429 memset(&p[2], 0, len - 2);
430 return;
431 }
432 }
433