ip6opt.c revision 92889 
1/*
2 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of the project nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * $FreeBSD: head/lib/libc/net/ip6opt.c 92889 2002-03-21 18:49:23Z obrien $
30 */
31
32#include <sys/param.h>
33#include <sys/types.h>
34#include <sys/socket.h>
35
36#include <netinet/in.h>
37#include <netinet/ip6.h>
38
39#include <string.h>
40#include <stdio.h>
41
42static int ip6optlen(u_int8_t *opt, u_int8_t *lim);
43static void inet6_insert_padopt(u_char *p, int len);
44
45/*
46 * This function returns the number of bytes required to hold an option
47 * when it is stored as ancillary data, including the cmsghdr structure
48 * at the beginning, and any padding at the end (to make its size a
49 * multiple of 8 bytes).  The argument is the size of the structure
50 * defining the option, which must include any pad bytes at the
51 * beginning (the value y in the alignment term "xn + y"), the type
52 * byte, the length byte, and the option data.
53 */
54int
55inet6_option_space(nbytes)
56	int nbytes;
57{
58	nbytes += 2;	/* we need space for nxt-hdr and length fields */
59	return(CMSG_SPACE((nbytes + 7) & ~7));
60}
61
62/*
63 * This function is called once per ancillary data object that will
64 * contain either Hop-by-Hop or Destination options.  It returns 0 on
65 * success or -1 on an error.
66 */
67int
68inet6_option_init(bp, cmsgp, type)
69	void *bp;
70	struct cmsghdr **cmsgp;
71	int type;
72{
73	struct cmsghdr *ch = (struct cmsghdr *)bp;
74
75	/* argument validation */
76	if (type != IPV6_HOPOPTS && type != IPV6_DSTOPTS)
77		return(-1);
78
79	ch->cmsg_level = IPPROTO_IPV6;
80	ch->cmsg_type = type;
81	ch->cmsg_len = CMSG_LEN(0);
82
83	*cmsgp = ch;
84	return(0);
85}
86
87/*
88 * This function appends a Hop-by-Hop option or a Destination option
89 * into an ancillary data object that has been initialized by
90 * inet6_option_init().  This function returns 0 if it succeeds or -1 on
91 * an error.
92 * multx is the value x in the alignment term "xn + y" described
93 * earlier.  It must have a value of 1, 2, 4, or 8.
94 * plusy is the value y in the alignment term "xn + y" described
95 * earlier.  It must have a value between 0 and 7, inclusive.
96 */
97int
98inet6_option_append(cmsg, typep, multx, plusy)
99	struct cmsghdr *cmsg;
100	const u_int8_t *typep;
101	int multx;
102	int plusy;
103{
104	int padlen, optlen, off;
105	u_char *bp = (u_char *)cmsg + cmsg->cmsg_len;
106	struct ip6_ext *eh = (struct ip6_ext *)CMSG_DATA(cmsg);
107
108	/* argument validation */
109	if (multx != 1 && multx != 2 && multx != 4 && multx != 8)
110		return(-1);
111	if (plusy < 0 || plusy > 7)
112		return(-1);
113	if (typep[0] > 255)
114		return(-1);
115
116	/*
117	 * If this is the first option, allocate space for the
118	 * first 2 bytes(for next header and length fields) of
119	 * the option header.
120	 */
121	if (bp == (u_char *)eh) {
122		bp += 2;
123		cmsg->cmsg_len += 2;
124	}
125
126	/* calculate pad length before the option. */
127	off = bp - (u_char *)eh;
128	padlen = (((off % multx) + (multx - 1)) & ~(multx - 1)) -
129		(off % multx);
130	padlen += plusy;
131	/* insert padding */
132	inet6_insert_padopt(bp, padlen);
133	cmsg->cmsg_len += padlen;
134	bp += padlen;
135
136	/* copy the option */
137	if (typep[0] == IP6OPT_PAD1)
138		optlen = 1;
139	else
140		optlen = typep[1] + 2;
141	memcpy(bp, typep, optlen);
142	bp += optlen;
143	cmsg->cmsg_len += optlen;
144
145	/* calculate pad length after the option and insert the padding */
146	off = bp - (u_char *)eh;
147	padlen = ((off + 7) & ~7) - off;
148	inet6_insert_padopt(bp, padlen);
149	bp += padlen;
150	cmsg->cmsg_len += padlen;
151
152	/* update the length field of the ip6 option header */
153	eh->ip6e_len = ((bp - (u_char *)eh) >> 3) - 1;
154
155	return(0);
156}
157
158/*
159 * This function appends a Hop-by-Hop option or a Destination option
160 * into an ancillary data object that has been initialized by
161 * inet6_option_init().  This function returns a pointer to the 8-bit
162 * option type field that starts the option on success, or NULL on an
163 * error.
164 * The difference between this function and inet6_option_append() is
165 * that the latter copies the contents of a previously built option into
166 * the ancillary data object while the current function returns a
167 * pointer to the space in the data object where the option's TLV must
168 * then be built by the caller.
169 *
170 */
171u_int8_t *
172inet6_option_alloc(cmsg, datalen, multx, plusy)
173	struct cmsghdr *cmsg;
174	int datalen;
175	int multx;
176	int plusy;
177{
178	int padlen, off;
179	u_int8_t *bp = (u_char *)cmsg + cmsg->cmsg_len;
180	u_int8_t *retval;
181	struct ip6_ext *eh = (struct ip6_ext *)CMSG_DATA(cmsg);
182
183	/* argument validation */
184	if (multx != 1 && multx != 2 && multx != 4 && multx != 8)
185		return(NULL);
186	if (plusy < 0 || plusy > 7)
187		return(NULL);
188
189	/*
190	 * If this is the first option, allocate space for the
191	 * first 2 bytes(for next header and length fields) of
192	 * the option header.
193	 */
194	if (bp == (u_char *)eh) {
195		bp += 2;
196		cmsg->cmsg_len += 2;
197	}
198
199	/* calculate pad length before the option. */
200	off = bp - (u_char *)eh;
201	padlen = (((off % multx) + (multx - 1)) & ~(multx - 1)) -
202		(off % multx);
203	padlen += plusy;
204	/* insert padding */
205	inet6_insert_padopt(bp, padlen);
206	cmsg->cmsg_len += padlen;
207	bp += padlen;
208
209	/* keep space to store specified length of data */
210	retval = bp;
211	bp += datalen;
212	cmsg->cmsg_len += datalen;
213
214	/* calculate pad length after the option and insert the padding */
215	off = bp - (u_char *)eh;
216	padlen = ((off + 7) & ~7) - off;
217	inet6_insert_padopt(bp, padlen);
218	bp += padlen;
219	cmsg->cmsg_len += padlen;
220
221	/* update the length field of the ip6 option header */
222	eh->ip6e_len = ((bp - (u_char *)eh) >> 3) - 1;
223
224	return(retval);
225}
226
227/*
228 * This function processes the next Hop-by-Hop option or Destination
229 * option in an ancillary data object.  If another option remains to be
230 * processed, the return value of the function is 0 and *tptrp points to
231 * the 8-bit option type field (which is followed by the 8-bit option
232 * data length, followed by the option data).  If no more options remain
233 * to be processed, the return value is -1 and *tptrp is NULL.  If an
234 * error occurs, the return value is -1 and *tptrp is not NULL.
235 * (RFC 2292, 6.3.5)
236 */
237int
238inet6_option_next(cmsg, tptrp)
239	const struct cmsghdr *cmsg;
240	u_int8_t **tptrp;
241{
242	struct ip6_ext *ip6e;
243	int hdrlen, optlen;
244	u_int8_t *lim;
245
246	if (cmsg->cmsg_level != IPPROTO_IPV6 ||
247	    (cmsg->cmsg_type != IPV6_HOPOPTS &&
248	     cmsg->cmsg_type != IPV6_DSTOPTS))
249		return(-1);
250
251	/* message length validation */
252	if (cmsg->cmsg_len < CMSG_SPACE(sizeof(struct ip6_ext)))
253		return(-1);
254	ip6e = (struct ip6_ext *)CMSG_DATA(cmsg);
255	hdrlen = (ip6e->ip6e_len + 1) << 3;
256	if (cmsg->cmsg_len < CMSG_SPACE(hdrlen))
257		return(-1);
258
259	/*
260	 * If the caller does not specify the starting point,
261	 * simply return the 1st option.
262	 * Otherwise, search the option list for the next option.
263	 */
264	lim = (u_int8_t *)ip6e + hdrlen;
265	if (*tptrp == NULL)
266		*tptrp = (u_int8_t *)(ip6e + 1);
267	else {
268		if ((optlen = ip6optlen(*tptrp, lim)) == 0)
269			return(-1);
270
271		*tptrp = *tptrp + optlen;
272	}
273	if (*tptrp >= lim) {	/* there is no option */
274		*tptrp = NULL;
275		return(-1);
276	}
277	/*
278	 * Finally, checks if the next option is safely stored in the
279	 * cmsg data.
280	 */
281	if (ip6optlen(*tptrp, lim) == 0)
282		return(-1);
283	else
284		return(0);
285}
286
287/*
288 * This function is similar to the inet6_option_next() function,
289 * except this function lets the caller specify the option type to be
290 * searched for, instead of always returning the next option in the
291 * ancillary data object.
292 * Note: RFC 2292 says the type of tptrp is u_int8_t *, but we think
293 *       it's a typo. The variable should be type of u_int8_t **.
294 */
295int
296inet6_option_find(cmsg, tptrp, type)
297	const struct cmsghdr *cmsg;
298	u_int8_t **tptrp;
299	int type;
300{
301	struct ip6_ext *ip6e;
302	int hdrlen, optlen;
303	u_int8_t *optp, *lim;
304
305	if (cmsg->cmsg_level != IPPROTO_IPV6 ||
306	    (cmsg->cmsg_type != IPV6_HOPOPTS &&
307	     cmsg->cmsg_type != IPV6_DSTOPTS))
308		return(-1);
309
310	/* message length validation */
311	if (cmsg->cmsg_len < CMSG_SPACE(sizeof(struct ip6_ext)))
312		return(-1);
313	ip6e = (struct ip6_ext *)CMSG_DATA(cmsg);
314	hdrlen = (ip6e->ip6e_len + 1) << 3;
315	if (cmsg->cmsg_len < CMSG_SPACE(hdrlen))
316		return(-1);
317
318	/*
319	 * If the caller does not specify the starting point,
320	 * search from the beginning of the option list.
321	 * Otherwise, search from *the next option* of the specified point.
322	 */
323	lim = (u_int8_t *)ip6e + hdrlen;
324	if (*tptrp == NULL)
325		*tptrp = (u_int8_t *)(ip6e + 1);
326	else {
327		if ((optlen = ip6optlen(*tptrp, lim)) == 0)
328			return(-1);
329
330		*tptrp = *tptrp + optlen;
331	}
332	for (optp = *tptrp; optp < lim; optp += optlen) {
333		if (*optp == type) {
334			*tptrp = optp;
335			return(0);
336		}
337		if ((optlen = ip6optlen(optp, lim)) == 0)
338			return(-1);
339	}
340
341	/* search failed */
342	*tptrp = NULL;
343	return(-1);
344}
345
346/*
347 * Calculate the length of a given IPv6 option. Also checks
348 * if the option is safely stored in user's buffer according to the
349 * calculated length and the limitation of the buffer.
350 */
351static int
352ip6optlen(opt, lim)
353	u_int8_t *opt, *lim;
354{
355	int optlen;
356
357	if (*opt == IP6OPT_PAD1)
358		optlen = 1;
359	else {
360		/* is there enough space to store type and len? */
361		if (opt + 2 > lim)
362			return(0);
363		optlen = *(opt + 1) + 2;
364	}
365	if (opt + optlen <= lim)
366		return(optlen);
367
368	return(0);
369}
370
371static void
372inet6_insert_padopt(u_char *p, int len)
373{
374	switch(len) {
375	 case 0:
376		 return;
377	 case 1:
378		 p[0] = IP6OPT_PAD1;
379		 return;
380	 default:
381		 p[0] = IP6OPT_PADN;
382		 p[1] = len - 2;
383		 memset(&p[2], 0, len - 2);
384		 return;
385	}
386}
387