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("$FreeBSD$");
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_fib.h>
58 #include <netinet/in_systm.h>
59 #include <netinet/in_var.h>
60 #include <netinet/ip.h>
61 #include <netinet/in_pcb.h>
62 #include <netinet/ip_var.h>
63 #include <netinet/ip_options.h>
64 #include <netinet/ip_icmp.h>
65 #include <machine/in_cksum.h>
66
67 #include <sys/socketvar.h>
68
69 static VNET_DEFINE(int, ip_dosourceroute);
70 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute,
71 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_dosourceroute), 0,
72 "Enable forwarding source routed IP packets");
73 #define V_ip_dosourceroute VNET(ip_dosourceroute)
74
75 static VNET_DEFINE(int, ip_acceptsourceroute);
76 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute,
77 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_acceptsourceroute), 0,
78 "Enable accepting source routed IP packets");
79 #define V_ip_acceptsourceroute VNET(ip_acceptsourceroute)
80
81 VNET_DEFINE(int, ip_doopts) = 1; /* 0 = ignore, 1 = process, 2 = reject */
82 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_VNET | CTLFLAG_RW,
83 &VNET_NAME(ip_doopts), 0, "Enable IP options processing ([LS]SRR, RR, TS)");
84
85 static void save_rte(struct mbuf *m, u_char *, struct in_addr);
86
87 /*
88 * Do option processing on a datagram, possibly discarding it if bad options
89 * are encountered, or forwarding it if source-routed.
90 *
91 * The pass argument is used when operating in the IPSTEALTH mode to tell
92 * what options to process: [LS]SRR (pass 0) or the others (pass 1). The
93 * reason for as many as two passes is that when doing IPSTEALTH, non-routing
94 * options should be processed only if the packet is for us.
95 *
96 * Returns 1 if packet has been forwarded/freed, 0 if the packet should be
97 * processed further.
98 */
99 int
100 ip_dooptions(struct mbuf *m, int pass)
101 {
102 struct ip *ip = mtod(m, struct ip *);
103 u_char *cp;
104 struct in_ifaddr *ia;
105 int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
106 struct in_addr *sin, dst;
107 uint32_t ntime;
108 struct nhop4_extended nh_ext;
109 struct sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
110
111 /* Ignore or reject packets with IP options. */
112 if (V_ip_doopts == 0)
113 return 0;
114 else if (V_ip_doopts == 2) {
115 type = ICMP_UNREACH;
116 code = ICMP_UNREACH_FILTER_PROHIB;
117 goto bad;
118 }
119
120 dst = ip->ip_dst;
121 cp = (u_char *)(ip + 1);
122 cnt = (ip->ip_hl << 2) - sizeof (struct ip);
123 for (; cnt > 0; cnt -= optlen, cp += optlen) {
124 opt = cp[IPOPT_OPTVAL];
125 if (opt == IPOPT_EOL)
126 break;
127 if (opt == IPOPT_NOP)
128 optlen = 1;
129 else {
130 if (cnt < IPOPT_OLEN + sizeof(*cp)) {
131 code = &cp[IPOPT_OLEN] - (u_char *)ip;
132 goto bad;
133 }
134 optlen = cp[IPOPT_OLEN];
135 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
136 code = &cp[IPOPT_OLEN] - (u_char *)ip;
137 goto bad;
138 }
139 }
140 switch (opt) {
141
142 default:
143 break;
144
145 /*
146 * Source routing with record. Find interface with current
147 * destination address. If none on this machine then drop if
148 * strictly routed, or do nothing if loosely routed. Record
149 * interface address and bring up next address component. If
150 * strictly routed make sure next address is on directly
151 * accessible net.
152 */
153 case IPOPT_LSRR:
154 case IPOPT_SSRR:
155 #ifdef IPSTEALTH
156 if (V_ipstealth && pass > 0)
157 break;
158 #endif
159 if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
160 code = &cp[IPOPT_OLEN] - (u_char *)ip;
161 goto bad;
162 }
163 if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
164 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
165 goto bad;
166 }
167 ipaddr.sin_addr = ip->ip_dst;
168 if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr)
169 == 0) {
170 if (opt == IPOPT_SSRR) {
171 type = ICMP_UNREACH;
172 code = ICMP_UNREACH_SRCFAIL;
173 goto bad;
174 }
175 if (!V_ip_dosourceroute)
176 goto nosourcerouting;
177 /*
178 * Loose routing, and not at next destination
179 * yet; nothing to do except forward.
180 */
181 break;
182 }
183 off--; /* 0 origin */
184 if (off > optlen - (int)sizeof(struct in_addr)) {
185 /*
186 * End of source route. Should be for us.
187 */
188 if (!V_ip_acceptsourceroute)
189 goto nosourcerouting;
190 save_rte(m, cp, ip->ip_src);
191 break;
192 }
193 #ifdef IPSTEALTH
194 if (V_ipstealth)
195 goto dropit;
196 #endif
197 if (!V_ip_dosourceroute) {
198 if (V_ipforwarding) {
199 char srcbuf[INET_ADDRSTRLEN];
200 char dstbuf[INET_ADDRSTRLEN];
201
202 /*
203 * Acting as a router, so generate
204 * ICMP
205 */
206 nosourcerouting:
207 log(LOG_WARNING,
208 "attempted source route from %s "
209 "to %s\n",
210 inet_ntoa_r(ip->ip_src, srcbuf),
211 inet_ntoa_r(ip->ip_dst, dstbuf));
212 type = ICMP_UNREACH;
213 code = ICMP_UNREACH_SRCFAIL;
214 goto bad;
215 } else {
216 /*
217 * Not acting as a router, so
218 * silently drop.
219 */
220 #ifdef IPSTEALTH
221 dropit:
222 #endif
223 IPSTAT_INC(ips_cantforward);
224 m_freem(m);
225 return (1);
226 }
227 }
228
229 /*
230 * locate outgoing interface
231 */
232 (void)memcpy(&ipaddr.sin_addr, cp + off,
233 sizeof(ipaddr.sin_addr));
234
235 type = ICMP_UNREACH;
236 code = ICMP_UNREACH_SRCFAIL;
237
238 if (opt == IPOPT_SSRR) {
239 #define INA struct in_ifaddr *
240 #define SA struct sockaddr *
241 ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr,
242 RT_ALL_FIBS);
243 if (ia == NULL)
244 ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0,
245 RT_ALL_FIBS);
246 if (ia == NULL)
247 goto bad;
248
249 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
250 sizeof(struct in_addr));
251 ifa_free(&ia->ia_ifa);
252 } else {
253 /* XXX MRT 0 for routing */
254 if (fib4_lookup_nh_ext(M_GETFIB(m),
255 ipaddr.sin_addr, 0, 0, &nh_ext) != 0)
256 goto bad;
257
258 memcpy(cp + off, &nh_ext.nh_src,
259 sizeof(struct in_addr));
260 }
261
262 ip->ip_dst = ipaddr.sin_addr;
263 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
264 /*
265 * Let ip_intr's mcast routing check handle mcast pkts
266 */
267 forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
268 break;
269
270 case IPOPT_RR:
271 #ifdef IPSTEALTH
272 if (V_ipstealth && pass == 0)
273 break;
274 #endif
275 if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
276 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
277 goto bad;
278 }
279 if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
280 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
281 goto bad;
282 }
283 /*
284 * If no space remains, ignore.
285 */
286 off--; /* 0 origin */
287 if (off > optlen - (int)sizeof(struct in_addr))
288 break;
289 (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
290 sizeof(ipaddr.sin_addr));
291 /*
292 * Locate outgoing interface; if we're the
293 * destination, use the incoming interface (should be
294 * same).
295 */
296 if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) != NULL) {
297 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
298 sizeof(struct in_addr));
299 ifa_free(&ia->ia_ifa);
300 } else if (fib4_lookup_nh_ext(M_GETFIB(m),
301 ipaddr.sin_addr, 0, 0, &nh_ext) == 0) {
302 memcpy(cp + off, &nh_ext.nh_src,
303 sizeof(struct in_addr));
304 } else {
305 type = ICMP_UNREACH;
306 code = ICMP_UNREACH_HOST;
307 goto bad;
308 }
309 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
310 break;
311
312 case IPOPT_TS:
313 #ifdef IPSTEALTH
314 if (V_ipstealth && pass == 0)
315 break;
316 #endif
317 code = cp - (u_char *)ip;
318 if (optlen < 4 || optlen > 40) {
319 code = &cp[IPOPT_OLEN] - (u_char *)ip;
320 goto bad;
321 }
322 if ((off = cp[IPOPT_OFFSET]) < 5) {
323 code = &cp[IPOPT_OLEN] - (u_char *)ip;
324 goto bad;
325 }
326 if (off > optlen - (int)sizeof(int32_t)) {
327 cp[IPOPT_OFFSET + 1] += (1 << 4);
328 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
329 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
330 goto bad;
331 }
332 break;
333 }
334 off--; /* 0 origin */
335 sin = (struct in_addr *)(cp + off);
336 switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
337
338 case IPOPT_TS_TSONLY:
339 break;
340
341 case IPOPT_TS_TSANDADDR:
342 if (off + sizeof(uint32_t) +
343 sizeof(struct in_addr) > optlen) {
344 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
345 goto bad;
346 }
347 ipaddr.sin_addr = dst;
348 ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
349 m->m_pkthdr.rcvif);
350 if (ia == NULL)
351 continue;
352 (void)memcpy(sin, &IA_SIN(ia)->sin_addr,
353 sizeof(struct in_addr));
354 ifa_free(&ia->ia_ifa);
355 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
356 off += sizeof(struct in_addr);
357 break;
358
359 case IPOPT_TS_PRESPEC:
360 if (off + sizeof(uint32_t) +
361 sizeof(struct in_addr) > optlen) {
362 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
363 goto bad;
364 }
365 (void)memcpy(&ipaddr.sin_addr, sin,
366 sizeof(struct in_addr));
367 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0)
368 continue;
369 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
370 off += sizeof(struct in_addr);
371 break;
372
373 default:
374 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
375 goto bad;
376 }
377 ntime = iptime();
378 (void)memcpy(cp + off, &ntime, sizeof(uint32_t));
379 cp[IPOPT_OFFSET] += sizeof(uint32_t);
380 }
381 }
382 if (forward && V_ipforwarding) {
383 ip_forward(m, 1);
384 return (1);
385 }
386 return (0);
387 bad:
388 icmp_error(m, type, code, 0, 0);
389 IPSTAT_INC(ips_badoptions);
390 return (1);
391 }
392
393 /*
394 * Save incoming source route for use in replies, to be picked up later by
395 * ip_srcroute if the receiver is interested.
396 */
397 static void
398 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
399 {
400 unsigned olen;
401 struct ipopt_tag *opts;
402
403 opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
404 sizeof(struct ipopt_tag), M_NOWAIT);
405 if (opts == NULL)
406 return;
407
408 olen = option[IPOPT_OLEN];
409 if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
410 m_tag_free((struct m_tag *)opts);
411 return;
412 }
413 bcopy(option, opts->ip_srcrt.srcopt, olen);
414 opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
415 opts->ip_srcrt.dst = dst;
416 m_tag_prepend(m, (struct m_tag *)opts);
417 }
418
419 /*
420 * Retrieve incoming source route for use in replies, in the same form used
421 * by setsockopt. The first hop is placed before the options, will be
422 * removed later.
423 */
424 struct mbuf *
425 ip_srcroute(struct mbuf *m0)
426 {
427 struct in_addr *p, *q;
428 struct mbuf *m;
429 struct ipopt_tag *opts;
430
431 opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
432 if (opts == NULL)
433 return (NULL);
434
435 if (opts->ip_nhops == 0)
436 return (NULL);
437 m = m_get(M_NOWAIT, MT_DATA);
438 if (m == NULL)
439 return (NULL);
440
441 #define OPTSIZ (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
442
443 /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
444 m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
445 sizeof(struct in_addr) + OPTSIZ;
446
447 /*
448 * First, save first hop for return route.
449 */
450 p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
451 *(mtod(m, struct in_addr *)) = *p--;
452
453 /*
454 * Copy option fields and padding (nop) to mbuf.
455 */
456 opts->ip_srcrt.nop = IPOPT_NOP;
457 opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
458 (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
459 &(opts->ip_srcrt.nop), OPTSIZ);
460 q = (struct in_addr *)(mtod(m, caddr_t) +
461 sizeof(struct in_addr) + OPTSIZ);
462 #undef OPTSIZ
463 /*
464 * Record return path as an IP source route, reversing the path
465 * (pointers are now aligned).
466 */
467 while (p >= opts->ip_srcrt.route) {
468 *q++ = *p--;
469 }
470 /*
471 * Last hop goes to final destination.
472 */
473 *q = opts->ip_srcrt.dst;
474 m_tag_delete(m0, (struct m_tag *)opts);
475 return (m);
476 }
477
478 /*
479 * Strip out IP options, at higher level protocol in the kernel.
480 */
481 void
482 ip_stripoptions(struct mbuf *m)
483 {
484 struct ip *ip = mtod(m, struct ip *);
485 int olen;
486
487 olen = (ip->ip_hl << 2) - sizeof(struct ip);
488 m->m_len -= olen;
489 if (m->m_flags & M_PKTHDR)
490 m->m_pkthdr.len -= olen;
491 ip->ip_len = htons(ntohs(ip->ip_len) - olen);
492 ip->ip_hl = sizeof(struct ip) >> 2;
493
494 bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1),
495 (size_t )(m->m_len - sizeof(struct ip)));
496 }
497
498 /*
499 * Insert IP options into preformed packet. Adjust IP destination as
500 * required for IP source routing, as indicated by a non-zero in_addr at the
501 * start of the options.
502 *
503 * XXX This routine assumes that the packet has no options in place.
504 */
505 struct mbuf *
506 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
507 {
508 struct ipoption *p = mtod(opt, struct ipoption *);
509 struct mbuf *n;
510 struct ip *ip = mtod(m, struct ip *);
511 unsigned optlen;
512
513 optlen = opt->m_len - sizeof(p->ipopt_dst);
514 if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) {
515 *phlen = 0;
516 return (m); /* XXX should fail */
517 }
518 if (p->ipopt_dst.s_addr)
519 ip->ip_dst = p->ipopt_dst;
520 if (!M_WRITABLE(m) || M_LEADINGSPACE(m) < optlen) {
521 n = m_gethdr(M_NOWAIT, MT_DATA);
522 if (n == NULL) {
523 *phlen = 0;
524 return (m);
525 }
526 m_move_pkthdr(n, m);
527 n->m_pkthdr.rcvif = NULL;
528 n->m_pkthdr.len += optlen;
529 m->m_len -= sizeof(struct ip);
530 m->m_data += sizeof(struct ip);
531 n->m_next = m;
532 m = n;
533 m->m_len = optlen + sizeof(struct ip);
534 m->m_data += max_linkhdr;
535 bcopy(ip, mtod(m, void *), sizeof(struct ip));
536 } else {
537 m->m_data -= optlen;
538 m->m_len += optlen;
539 m->m_pkthdr.len += optlen;
540 bcopy(ip, mtod(m, void *), sizeof(struct ip));
541 }
542 ip = mtod(m, struct ip *);
543 bcopy(p->ipopt_list, ip + 1, optlen);
544 *phlen = sizeof(struct ip) + optlen;
545 ip->ip_v = IPVERSION;
546 ip->ip_hl = *phlen >> 2;
547 ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
548 return (m);
549 }
550
551 /*
552 * Copy options from ip to jp, omitting those not copied during
553 * fragmentation.
554 */
555 int
556 ip_optcopy(struct ip *ip, struct ip *jp)
557 {
558 u_char *cp, *dp;
559 int opt, optlen, cnt;
560
561 cp = (u_char *)(ip + 1);
562 dp = (u_char *)(jp + 1);
563 cnt = (ip->ip_hl << 2) - sizeof (struct ip);
564 for (; cnt > 0; cnt -= optlen, cp += optlen) {
565 opt = cp[0];
566 if (opt == IPOPT_EOL)
567 break;
568 if (opt == IPOPT_NOP) {
569 /* Preserve for IP mcast tunnel's LSRR alignment. */
570 *dp++ = IPOPT_NOP;
571 optlen = 1;
572 continue;
573 }
574
575 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
576 ("ip_optcopy: malformed ipv4 option"));
577 optlen = cp[IPOPT_OLEN];
578 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
579 ("ip_optcopy: malformed ipv4 option"));
580
581 /* Bogus lengths should have been caught by ip_dooptions. */
582 if (optlen > cnt)
583 optlen = cnt;
584 if (IPOPT_COPIED(opt)) {
585 bcopy(cp, dp, optlen);
586 dp += optlen;
587 }
588 }
589 for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
590 *dp++ = IPOPT_EOL;
591 return (optlen);
592 }
593
594 /*
595 * Set up IP options in pcb for insertion in output packets. Store in mbuf
596 * with pointer in pcbopt, adding pseudo-option with destination address if
597 * source routed.
598 */
599 int
600 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
601 {
602 int cnt, optlen;
603 u_char *cp;
604 struct mbuf **pcbopt;
605 u_char opt;
606
607 INP_WLOCK_ASSERT(inp);
608
609 pcbopt = &inp->inp_options;
610
611 /* turn off any old options */
612 if (*pcbopt)
613 (void)m_free(*pcbopt);
614 *pcbopt = NULL;
615 if (m == NULL || m->m_len == 0) {
616 /*
617 * Only turning off any previous options.
618 */
619 if (m != NULL)
620 (void)m_free(m);
621 return (0);
622 }
623
624 if (m->m_len % sizeof(int32_t))
625 goto bad;
626 /*
627 * IP first-hop destination address will be stored before actual
628 * options; move other options back and clear it when none present.
629 */
630 if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
631 goto bad;
632 cnt = m->m_len;
633 m->m_len += sizeof(struct in_addr);
634 cp = mtod(m, u_char *) + sizeof(struct in_addr);
635 bcopy(mtod(m, void *), cp, (unsigned)cnt);
636 bzero(mtod(m, void *), sizeof(struct in_addr));
637
638 for (; cnt > 0; cnt -= optlen, cp += optlen) {
639 opt = cp[IPOPT_OPTVAL];
640 if (opt == IPOPT_EOL)
641 break;
642 if (opt == IPOPT_NOP)
643 optlen = 1;
644 else {
645 if (cnt < IPOPT_OLEN + sizeof(*cp))
646 goto bad;
647 optlen = cp[IPOPT_OLEN];
648 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
649 goto bad;
650 }
651 switch (opt) {
652
653 default:
654 break;
655
656 case IPOPT_LSRR:
657 case IPOPT_SSRR:
658 /*
659 * User process specifies route as:
660 *
661 * ->A->B->C->D
662 *
663 * D must be our final destination (but we can't
664 * check that since we may not have connected yet).
665 * A is first hop destination, which doesn't appear
666 * in actual IP option, but is stored before the
667 * options.
668 */
669 /* XXX-BZ PRIV_NETINET_SETHDROPTS? */
670 if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
671 goto bad;
672 m->m_len -= sizeof(struct in_addr);
673 cnt -= sizeof(struct in_addr);
674 optlen -= sizeof(struct in_addr);
675 cp[IPOPT_OLEN] = optlen;
676 /*
677 * Move first hop before start of options.
678 */
679 bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
680 sizeof(struct in_addr));
681 /*
682 * Then copy rest of options back
683 * to close up the deleted entry.
684 */
685 bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
686 &cp[IPOPT_OFFSET+1],
687 (unsigned)cnt - (IPOPT_MINOFF - 1));
688 break;
689 }
690 }
691 if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
692 goto bad;
693 *pcbopt = m;
694 return (0);
695
696 bad:
697 (void)m_free(m);
698 return (EINVAL);
699 }
700
701 /*
702 * Check for the presence of the IP Router Alert option [RFC2113]
703 * in the header of an IPv4 datagram.
704 *
705 * This call is not intended for use from the forwarding path; it is here
706 * so that protocol domains may check for the presence of the option.
707 * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
708 * option does not have much relevance to the implementation, though this
709 * may change in future.
710 * Router alert options SHOULD be passed if running in IPSTEALTH mode and
711 * we are not the endpoint.
712 * Length checks on individual options should already have been performed
713 * by ip_dooptions() therefore they are folded under INVARIANTS here.
714 *
715 * Return zero if not present or options are invalid, non-zero if present.
716 */
717 int
718 ip_checkrouteralert(struct mbuf *m)
719 {
720 struct ip *ip = mtod(m, struct ip *);
721 u_char *cp;
722 int opt, optlen, cnt, found_ra;
723
724 found_ra = 0;
725 cp = (u_char *)(ip + 1);
726 cnt = (ip->ip_hl << 2) - sizeof (struct ip);
727 for (; cnt > 0; cnt -= optlen, cp += optlen) {
728 opt = cp[IPOPT_OPTVAL];
729 if (opt == IPOPT_EOL)
730 break;
731 if (opt == IPOPT_NOP)
732 optlen = 1;
733 else {
734 #ifdef INVARIANTS
735 if (cnt < IPOPT_OLEN + sizeof(*cp))
736 break;
737 #endif
738 optlen = cp[IPOPT_OLEN];
739 #ifdef INVARIANTS
740 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
741 break;
742 #endif
743 }
744 switch (opt) {
745 case IPOPT_RA:
746 #ifdef INVARIANTS
747 if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
748 (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
749 break;
750 else
751 #endif
752 found_ra = 1;
753 break;
754 default:
755 break;
756 }
757 }
758
759 return (found_ra);
760 }
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