1 /*
2 * Copyright (c) 1982, 1986, 1988, 1993
3 * The Regents of the University of California.
4 * Copyright (c) 2005 Andre Oppermann, Internet Business Solutions AG.
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 * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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 __FBSDID("$FreeBSD: releng/10.0/sys/netinet/ip_options.c 248373 2013-03-16 08:58:28Z glebius $");
34
35 #include "opt_ipstealth.h"
36
37 #include <sys/param.h>
38 #include <sys/systm.h>
39 #include <sys/mbuf.h>
40 #include <sys/domain.h>
41 #include <sys/protosw.h>
42 #include <sys/socket.h>
43 #include <sys/time.h>
44 #include <sys/kernel.h>
45 #include <sys/syslog.h>
46 #include <sys/sysctl.h>
47
48 #include <net/if.h>
49 #include <net/if_types.h>
50 #include <net/if_var.h>
51 #include <net/if_dl.h>
52 #include <net/route.h>
53 #include <net/netisr.h>
54 #include <net/vnet.h>
55
56 #include <netinet/in.h>
57 #include <netinet/in_systm.h>
58 #include <netinet/in_var.h>
59 #include <netinet/ip.h>
60 #include <netinet/in_pcb.h>
61 #include <netinet/ip_var.h>
62 #include <netinet/ip_options.h>
63 #include <netinet/ip_icmp.h>
64 #include <machine/in_cksum.h>
65
66 #include <sys/socketvar.h>
67
68 static int ip_dosourceroute = 0;
69 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute, CTLFLAG_RW,
70 &ip_dosourceroute, 0, "Enable forwarding source routed IP packets");
71
72 static int ip_acceptsourceroute = 0;
73 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute,
74 CTLFLAG_RW, &ip_acceptsourceroute, 0,
75 "Enable accepting source routed IP packets");
76
77 int ip_doopts = 1; /* 0 = ignore, 1 = process, 2 = reject */
78 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_RW,
79 &ip_doopts, 0, "Enable IP options processing ([LS]SRR, RR, TS)");
80
81 static void save_rte(struct mbuf *m, u_char *, struct in_addr);
82
83 /*
84 * Do option processing on a datagram, possibly discarding it if bad options
85 * are encountered, or forwarding it if source-routed.
86 *
87 * The pass argument is used when operating in the IPSTEALTH mode to tell
88 * what options to process: [LS]SRR (pass 0) or the others (pass 1). The
89 * reason for as many as two passes is that when doing IPSTEALTH, non-routing
90 * options should be processed only if the packet is for us.
91 *
92 * Returns 1 if packet has been forwarded/freed, 0 if the packet should be
93 * processed further.
94 */
95 int
96 ip_dooptions(struct mbuf *m, int pass)
97 {
98 struct ip *ip = mtod(m, struct ip *);
99 u_char *cp;
100 struct in_ifaddr *ia;
101 int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
102 struct in_addr *sin, dst;
103 uint32_t ntime;
104 struct sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
105
106 /* Ignore or reject packets with IP options. */
107 if (ip_doopts == 0)
108 return 0;
109 else if (ip_doopts == 2) {
110 type = ICMP_UNREACH;
111 code = ICMP_UNREACH_FILTER_PROHIB;
112 goto bad;
113 }
114
115 dst = ip->ip_dst;
116 cp = (u_char *)(ip + 1);
117 cnt = (ip->ip_hl << 2) - sizeof (struct ip);
118 for (; cnt > 0; cnt -= optlen, cp += optlen) {
119 opt = cp[IPOPT_OPTVAL];
120 if (opt == IPOPT_EOL)
121 break;
122 if (opt == IPOPT_NOP)
123 optlen = 1;
124 else {
125 if (cnt < IPOPT_OLEN + sizeof(*cp)) {
126 code = &cp[IPOPT_OLEN] - (u_char *)ip;
127 goto bad;
128 }
129 optlen = cp[IPOPT_OLEN];
130 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
131 code = &cp[IPOPT_OLEN] - (u_char *)ip;
132 goto bad;
133 }
134 }
135 switch (opt) {
136
137 default:
138 break;
139
140 /*
141 * Source routing with record. Find interface with current
142 * destination address. If none on this machine then drop if
143 * strictly routed, or do nothing if loosely routed. Record
144 * interface address and bring up next address component. If
145 * strictly routed make sure next address is on directly
146 * accessible net.
147 */
148 case IPOPT_LSRR:
149 case IPOPT_SSRR:
150 #ifdef IPSTEALTH
151 if (V_ipstealth && pass > 0)
152 break;
153 #endif
154 if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
155 code = &cp[IPOPT_OLEN] - (u_char *)ip;
156 goto bad;
157 }
158 if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
159 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
160 goto bad;
161 }
162 ipaddr.sin_addr = ip->ip_dst;
163 if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr)
164 == 0) {
165 if (opt == IPOPT_SSRR) {
166 type = ICMP_UNREACH;
167 code = ICMP_UNREACH_SRCFAIL;
168 goto bad;
169 }
170 if (!ip_dosourceroute)
171 goto nosourcerouting;
172 /*
173 * Loose routing, and not at next destination
174 * yet; nothing to do except forward.
175 */
176 break;
177 }
178 off--; /* 0 origin */
179 if (off > optlen - (int)sizeof(struct in_addr)) {
180 /*
181 * End of source route. Should be for us.
182 */
183 if (!ip_acceptsourceroute)
184 goto nosourcerouting;
185 save_rte(m, cp, ip->ip_src);
186 break;
187 }
188 #ifdef IPSTEALTH
189 if (V_ipstealth)
190 goto dropit;
191 #endif
192 if (!ip_dosourceroute) {
193 if (V_ipforwarding) {
194 char buf[16]; /* aaa.bbb.ccc.ddd\0 */
195 /*
196 * Acting as a router, so generate
197 * ICMP
198 */
199 nosourcerouting:
200 strcpy(buf, inet_ntoa(ip->ip_dst));
201 log(LOG_WARNING,
202 "attempted source route from %s to %s\n",
203 inet_ntoa(ip->ip_src), buf);
204 type = ICMP_UNREACH;
205 code = ICMP_UNREACH_SRCFAIL;
206 goto bad;
207 } else {
208 /*
209 * Not acting as a router, so
210 * silently drop.
211 */
212 #ifdef IPSTEALTH
213 dropit:
214 #endif
215 IPSTAT_INC(ips_cantforward);
216 m_freem(m);
217 return (1);
218 }
219 }
220
221 /*
222 * locate outgoing interface
223 */
224 (void)memcpy(&ipaddr.sin_addr, cp + off,
225 sizeof(ipaddr.sin_addr));
226
227 if (opt == IPOPT_SSRR) {
228 #define INA struct in_ifaddr *
229 #define SA struct sockaddr *
230 if ((ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr)) == NULL)
231 ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0);
232 } else
233 /* XXX MRT 0 for routing */
234 ia = ip_rtaddr(ipaddr.sin_addr, M_GETFIB(m));
235 if (ia == NULL) {
236 type = ICMP_UNREACH;
237 code = ICMP_UNREACH_SRCFAIL;
238 goto bad;
239 }
240 ip->ip_dst = ipaddr.sin_addr;
241 (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
242 sizeof(struct in_addr));
243 ifa_free(&ia->ia_ifa);
244 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
245 /*
246 * Let ip_intr's mcast routing check handle mcast pkts
247 */
248 forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
249 break;
250
251 case IPOPT_RR:
252 #ifdef IPSTEALTH
253 if (V_ipstealth && pass == 0)
254 break;
255 #endif
256 if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
257 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
258 goto bad;
259 }
260 if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
261 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
262 goto bad;
263 }
264 /*
265 * If no space remains, ignore.
266 */
267 off--; /* 0 origin */
268 if (off > optlen - (int)sizeof(struct in_addr))
269 break;
270 (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
271 sizeof(ipaddr.sin_addr));
272 /*
273 * Locate outgoing interface; if we're the
274 * destination, use the incoming interface (should be
275 * same).
276 */
277 if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) == NULL &&
278 (ia = ip_rtaddr(ipaddr.sin_addr, M_GETFIB(m))) == NULL) {
279 type = ICMP_UNREACH;
280 code = ICMP_UNREACH_HOST;
281 goto bad;
282 }
283 (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
284 sizeof(struct in_addr));
285 ifa_free(&ia->ia_ifa);
286 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
287 break;
288
289 case IPOPT_TS:
290 #ifdef IPSTEALTH
291 if (V_ipstealth && pass == 0)
292 break;
293 #endif
294 code = cp - (u_char *)ip;
295 if (optlen < 4 || optlen > 40) {
296 code = &cp[IPOPT_OLEN] - (u_char *)ip;
297 goto bad;
298 }
299 if ((off = cp[IPOPT_OFFSET]) < 5) {
300 code = &cp[IPOPT_OLEN] - (u_char *)ip;
301 goto bad;
302 }
303 if (off > optlen - (int)sizeof(int32_t)) {
304 cp[IPOPT_OFFSET + 1] += (1 << 4);
305 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
306 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
307 goto bad;
308 }
309 break;
310 }
311 off--; /* 0 origin */
312 sin = (struct in_addr *)(cp + off);
313 switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
314
315 case IPOPT_TS_TSONLY:
316 break;
317
318 case IPOPT_TS_TSANDADDR:
319 if (off + sizeof(uint32_t) +
320 sizeof(struct in_addr) > optlen) {
321 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
322 goto bad;
323 }
324 ipaddr.sin_addr = dst;
325 ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
326 m->m_pkthdr.rcvif);
327 if (ia == NULL)
328 continue;
329 (void)memcpy(sin, &IA_SIN(ia)->sin_addr,
330 sizeof(struct in_addr));
331 ifa_free(&ia->ia_ifa);
332 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
333 off += sizeof(struct in_addr);
334 break;
335
336 case IPOPT_TS_PRESPEC:
337 if (off + sizeof(uint32_t) +
338 sizeof(struct in_addr) > optlen) {
339 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
340 goto bad;
341 }
342 (void)memcpy(&ipaddr.sin_addr, sin,
343 sizeof(struct in_addr));
344 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0)
345 continue;
346 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
347 off += sizeof(struct in_addr);
348 break;
349
350 default:
351 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
352 goto bad;
353 }
354 ntime = iptime();
355 (void)memcpy(cp + off, &ntime, sizeof(uint32_t));
356 cp[IPOPT_OFFSET] += sizeof(uint32_t);
357 }
358 }
359 if (forward && V_ipforwarding) {
360 ip_forward(m, 1);
361 return (1);
362 }
363 return (0);
364 bad:
365 icmp_error(m, type, code, 0, 0);
366 IPSTAT_INC(ips_badoptions);
367 return (1);
368 }
369
370 /*
371 * Save incoming source route for use in replies, to be picked up later by
372 * ip_srcroute if the receiver is interested.
373 */
374 static void
375 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
376 {
377 unsigned olen;
378 struct ipopt_tag *opts;
379
380 opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
381 sizeof(struct ipopt_tag), M_NOWAIT);
382 if (opts == NULL)
383 return;
384
385 olen = option[IPOPT_OLEN];
386 if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
387 m_tag_free((struct m_tag *)opts);
388 return;
389 }
390 bcopy(option, opts->ip_srcrt.srcopt, olen);
391 opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
392 opts->ip_srcrt.dst = dst;
393 m_tag_prepend(m, (struct m_tag *)opts);
394 }
395
396 /*
397 * Retrieve incoming source route for use in replies, in the same form used
398 * by setsockopt. The first hop is placed before the options, will be
399 * removed later.
400 */
401 struct mbuf *
402 ip_srcroute(struct mbuf *m0)
403 {
404 struct in_addr *p, *q;
405 struct mbuf *m;
406 struct ipopt_tag *opts;
407
408 opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
409 if (opts == NULL)
410 return (NULL);
411
412 if (opts->ip_nhops == 0)
413 return (NULL);
414 m = m_get(M_NOWAIT, MT_DATA);
415 if (m == NULL)
416 return (NULL);
417
418 #define OPTSIZ (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
419
420 /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
421 m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
422 sizeof(struct in_addr) + OPTSIZ;
423
424 /*
425 * First, save first hop for return route.
426 */
427 p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
428 *(mtod(m, struct in_addr *)) = *p--;
429
430 /*
431 * Copy option fields and padding (nop) to mbuf.
432 */
433 opts->ip_srcrt.nop = IPOPT_NOP;
434 opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
435 (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
436 &(opts->ip_srcrt.nop), OPTSIZ);
437 q = (struct in_addr *)(mtod(m, caddr_t) +
438 sizeof(struct in_addr) + OPTSIZ);
439 #undef OPTSIZ
440 /*
441 * Record return path as an IP source route, reversing the path
442 * (pointers are now aligned).
443 */
444 while (p >= opts->ip_srcrt.route) {
445 *q++ = *p--;
446 }
447 /*
448 * Last hop goes to final destination.
449 */
450 *q = opts->ip_srcrt.dst;
451 m_tag_delete(m0, (struct m_tag *)opts);
452 return (m);
453 }
454
455 /*
456 * Strip out IP options, at higher level protocol in the kernel.
457 */
458 void
459 ip_stripoptions(struct mbuf *m)
460 {
461 struct ip *ip = mtod(m, struct ip *);
462 int olen;
463
464 olen = (ip->ip_hl << 2) - sizeof(struct ip);
465 m->m_len -= olen;
466 if (m->m_flags & M_PKTHDR)
467 m->m_pkthdr.len -= olen;
468 ip->ip_len = htons(ntohs(ip->ip_len) - olen);
469 ip->ip_hl = sizeof(struct ip) >> 2;
470
471 bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1),
472 (size_t )(m->m_len - sizeof(struct ip)));
473 }
474
475 /*
476 * Insert IP options into preformed packet. Adjust IP destination as
477 * required for IP source routing, as indicated by a non-zero in_addr at the
478 * start of the options.
479 *
480 * XXX This routine assumes that the packet has no options in place.
481 */
482 struct mbuf *
483 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
484 {
485 struct ipoption *p = mtod(opt, struct ipoption *);
486 struct mbuf *n;
487 struct ip *ip = mtod(m, struct ip *);
488 unsigned optlen;
489
490 optlen = opt->m_len - sizeof(p->ipopt_dst);
491 if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) {
492 *phlen = 0;
493 return (m); /* XXX should fail */
494 }
495 if (p->ipopt_dst.s_addr)
496 ip->ip_dst = p->ipopt_dst;
497 if (m->m_flags & M_EXT || m->m_data - optlen < m->m_pktdat) {
498 n = m_gethdr(M_NOWAIT, MT_DATA);
499 if (n == NULL) {
500 *phlen = 0;
501 return (m);
502 }
503 m_move_pkthdr(n, m);
504 n->m_pkthdr.rcvif = NULL;
505 n->m_pkthdr.len += optlen;
506 m->m_len -= sizeof(struct ip);
507 m->m_data += sizeof(struct ip);
508 n->m_next = m;
509 m = n;
510 m->m_len = optlen + sizeof(struct ip);
511 m->m_data += max_linkhdr;
512 bcopy(ip, mtod(m, void *), sizeof(struct ip));
513 } else {
514 m->m_data -= optlen;
515 m->m_len += optlen;
516 m->m_pkthdr.len += optlen;
517 bcopy(ip, mtod(m, void *), sizeof(struct ip));
518 }
519 ip = mtod(m, struct ip *);
520 bcopy(p->ipopt_list, ip + 1, optlen);
521 *phlen = sizeof(struct ip) + optlen;
522 ip->ip_v = IPVERSION;
523 ip->ip_hl = *phlen >> 2;
524 ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
525 return (m);
526 }
527
528 /*
529 * Copy options from ip to jp, omitting those not copied during
530 * fragmentation.
531 */
532 int
533 ip_optcopy(struct ip *ip, struct ip *jp)
534 {
535 u_char *cp, *dp;
536 int opt, optlen, cnt;
537
538 cp = (u_char *)(ip + 1);
539 dp = (u_char *)(jp + 1);
540 cnt = (ip->ip_hl << 2) - sizeof (struct ip);
541 for (; cnt > 0; cnt -= optlen, cp += optlen) {
542 opt = cp[0];
543 if (opt == IPOPT_EOL)
544 break;
545 if (opt == IPOPT_NOP) {
546 /* Preserve for IP mcast tunnel's LSRR alignment. */
547 *dp++ = IPOPT_NOP;
548 optlen = 1;
549 continue;
550 }
551
552 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
553 ("ip_optcopy: malformed ipv4 option"));
554 optlen = cp[IPOPT_OLEN];
555 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
556 ("ip_optcopy: malformed ipv4 option"));
557
558 /* Bogus lengths should have been caught by ip_dooptions. */
559 if (optlen > cnt)
560 optlen = cnt;
561 if (IPOPT_COPIED(opt)) {
562 bcopy(cp, dp, optlen);
563 dp += optlen;
564 }
565 }
566 for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
567 *dp++ = IPOPT_EOL;
568 return (optlen);
569 }
570
571 /*
572 * Set up IP options in pcb for insertion in output packets. Store in mbuf
573 * with pointer in pcbopt, adding pseudo-option with destination address if
574 * source routed.
575 */
576 int
577 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
578 {
579 int cnt, optlen;
580 u_char *cp;
581 struct mbuf **pcbopt;
582 u_char opt;
583
584 INP_WLOCK_ASSERT(inp);
585
586 pcbopt = &inp->inp_options;
587
588 /* turn off any old options */
589 if (*pcbopt)
590 (void)m_free(*pcbopt);
591 *pcbopt = 0;
592 if (m == NULL || m->m_len == 0) {
593 /*
594 * Only turning off any previous options.
595 */
596 if (m != NULL)
597 (void)m_free(m);
598 return (0);
599 }
600
601 if (m->m_len % sizeof(int32_t))
602 goto bad;
603 /*
604 * IP first-hop destination address will be stored before actual
605 * options; move other options back and clear it when none present.
606 */
607 if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
608 goto bad;
609 cnt = m->m_len;
610 m->m_len += sizeof(struct in_addr);
611 cp = mtod(m, u_char *) + sizeof(struct in_addr);
612 bcopy(mtod(m, void *), cp, (unsigned)cnt);
613 bzero(mtod(m, void *), sizeof(struct in_addr));
614
615 for (; cnt > 0; cnt -= optlen, cp += optlen) {
616 opt = cp[IPOPT_OPTVAL];
617 if (opt == IPOPT_EOL)
618 break;
619 if (opt == IPOPT_NOP)
620 optlen = 1;
621 else {
622 if (cnt < IPOPT_OLEN + sizeof(*cp))
623 goto bad;
624 optlen = cp[IPOPT_OLEN];
625 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
626 goto bad;
627 }
628 switch (opt) {
629
630 default:
631 break;
632
633 case IPOPT_LSRR:
634 case IPOPT_SSRR:
635 /*
636 * User process specifies route as:
637 *
638 * ->A->B->C->D
639 *
640 * D must be our final destination (but we can't
641 * check that since we may not have connected yet).
642 * A is first hop destination, which doesn't appear
643 * in actual IP option, but is stored before the
644 * options.
645 */
646 /* XXX-BZ PRIV_NETINET_SETHDROPTS? */
647 if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
648 goto bad;
649 m->m_len -= sizeof(struct in_addr);
650 cnt -= sizeof(struct in_addr);
651 optlen -= sizeof(struct in_addr);
652 cp[IPOPT_OLEN] = optlen;
653 /*
654 * Move first hop before start of options.
655 */
656 bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
657 sizeof(struct in_addr));
658 /*
659 * Then copy rest of options back
660 * to close up the deleted entry.
661 */
662 bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
663 &cp[IPOPT_OFFSET+1],
664 (unsigned)cnt - (IPOPT_MINOFF - 1));
665 break;
666 }
667 }
668 if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
669 goto bad;
670 *pcbopt = m;
671 return (0);
672
673 bad:
674 (void)m_free(m);
675 return (EINVAL);
676 }
677
678 /*
679 * Check for the presence of the IP Router Alert option [RFC2113]
680 * in the header of an IPv4 datagram.
681 *
682 * This call is not intended for use from the forwarding path; it is here
683 * so that protocol domains may check for the presence of the option.
684 * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
685 * option does not have much relevance to the implementation, though this
686 * may change in future.
687 * Router alert options SHOULD be passed if running in IPSTEALTH mode and
688 * we are not the endpoint.
689 * Length checks on individual options should already have been peformed
690 * by ip_dooptions() therefore they are folded under INVARIANTS here.
691 *
692 * Return zero if not present or options are invalid, non-zero if present.
693 */
694 int
695 ip_checkrouteralert(struct mbuf *m)
696 {
697 struct ip *ip = mtod(m, struct ip *);
698 u_char *cp;
699 int opt, optlen, cnt, found_ra;
700
701 found_ra = 0;
702 cp = (u_char *)(ip + 1);
703 cnt = (ip->ip_hl << 2) - sizeof (struct ip);
704 for (; cnt > 0; cnt -= optlen, cp += optlen) {
705 opt = cp[IPOPT_OPTVAL];
706 if (opt == IPOPT_EOL)
707 break;
708 if (opt == IPOPT_NOP)
709 optlen = 1;
710 else {
711 #ifdef INVARIANTS
712 if (cnt < IPOPT_OLEN + sizeof(*cp))
713 break;
714 #endif
715 optlen = cp[IPOPT_OLEN];
716 #ifdef INVARIANTS
717 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
718 break;
719 #endif
720 }
721 switch (opt) {
722 case IPOPT_RA:
723 #ifdef INVARIANTS
724 if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
725 (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
726 break;
727 else
728 #endif
729 found_ra = 1;
730 break;
731 default:
732 break;
733 }
734 }
735
736 return (found_ra);
737 }
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