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_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 VNET_DEFINE(int, ip_dosourceroute);
69 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute,
70 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_dosourceroute), 0,
71 "Enable forwarding source routed IP packets");
72 #define V_ip_dosourceroute VNET(ip_dosourceroute)
73
74 static VNET_DEFINE(int, ip_acceptsourceroute);
75 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute,
76 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_acceptsourceroute), 0,
77 "Enable accepting source routed IP packets");
78 #define V_ip_acceptsourceroute VNET(ip_acceptsourceroute)
79
80 VNET_DEFINE(int, ip_doopts) = 1; /* 0 = ignore, 1 = process, 2 = reject */
81 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_VNET | CTLFLAG_RW,
82 &VNET_NAME(ip_doopts), 0, "Enable IP options processing ([LS]SRR, RR, TS)");
83
84 static void save_rte(struct mbuf *m, u_char *, struct in_addr);
85
86 /*
87 * Do option processing on a datagram, possibly discarding it if bad options
88 * are encountered, or forwarding it if source-routed.
89 *
90 * The pass argument is used when operating in the IPSTEALTH mode to tell
91 * what options to process: [LS]SRR (pass 0) or the others (pass 1). The
92 * reason for as many as two passes is that when doing IPSTEALTH, non-routing
93 * options should be processed only if the packet is for us.
94 *
95 * Returns 1 if packet has been forwarded/freed, 0 if the packet should be
96 * processed further.
97 */
98 int
99 ip_dooptions(struct mbuf *m, int pass)
100 {
101 struct ip *ip = mtod(m, struct ip *);
102 u_char *cp;
103 struct in_ifaddr *ia;
104 int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
105 struct in_addr *sin, dst;
106 uint32_t ntime;
107 struct sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
108
109 /* Ignore or reject packets with IP options. */
110 if (V_ip_doopts == 0)
111 return 0;
112 else if (V_ip_doopts == 2) {
113 type = ICMP_UNREACH;
114 code = ICMP_UNREACH_FILTER_PROHIB;
115 goto bad;
116 }
117
118 dst = ip->ip_dst;
119 cp = (u_char *)(ip + 1);
120 cnt = (ip->ip_hl << 2) - sizeof (struct ip);
121 for (; cnt > 0; cnt -= optlen, cp += optlen) {
122 opt = cp[IPOPT_OPTVAL];
123 if (opt == IPOPT_EOL)
124 break;
125 if (opt == IPOPT_NOP)
126 optlen = 1;
127 else {
128 if (cnt < IPOPT_OLEN + sizeof(*cp)) {
129 code = &cp[IPOPT_OLEN] - (u_char *)ip;
130 goto bad;
131 }
132 optlen = cp[IPOPT_OLEN];
133 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
134 code = &cp[IPOPT_OLEN] - (u_char *)ip;
135 goto bad;
136 }
137 }
138 switch (opt) {
139
140 default:
141 break;
142
143 /*
144 * Source routing with record. Find interface with current
145 * destination address. If none on this machine then drop if
146 * strictly routed, or do nothing if loosely routed. Record
147 * interface address and bring up next address component. If
148 * strictly routed make sure next address is on directly
149 * accessible net.
150 */
151 case IPOPT_LSRR:
152 case IPOPT_SSRR:
153 #ifdef IPSTEALTH
154 if (V_ipstealth && pass > 0)
155 break;
156 #endif
157 if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
158 code = &cp[IPOPT_OLEN] - (u_char *)ip;
159 goto bad;
160 }
161 if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
162 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
163 goto bad;
164 }
165 ipaddr.sin_addr = ip->ip_dst;
166 if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr)
167 == 0) {
168 if (opt == IPOPT_SSRR) {
169 type = ICMP_UNREACH;
170 code = ICMP_UNREACH_SRCFAIL;
171 goto bad;
172 }
173 if (!V_ip_dosourceroute)
174 goto nosourcerouting;
175 /*
176 * Loose routing, and not at next destination
177 * yet; nothing to do except forward.
178 */
179 break;
180 }
181 off--; /* 0 origin */
182 if (off > optlen - (int)sizeof(struct in_addr)) {
183 /*
184 * End of source route. Should be for us.
185 */
186 if (!V_ip_acceptsourceroute)
187 goto nosourcerouting;
188 save_rte(m, cp, ip->ip_src);
189 break;
190 }
191 #ifdef IPSTEALTH
192 if (V_ipstealth)
193 goto dropit;
194 #endif
195 if (!V_ip_dosourceroute) {
196 if (V_ipforwarding) {
197 char buf[16]; /* aaa.bbb.ccc.ddd\0 */
198 /*
199 * Acting as a router, so generate
200 * ICMP
201 */
202 nosourcerouting:
203 strcpy(buf, inet_ntoa(ip->ip_dst));
204 log(LOG_WARNING,
205 "attempted source route from %s to %s\n",
206 inet_ntoa(ip->ip_src), buf);
207 type = ICMP_UNREACH;
208 code = ICMP_UNREACH_SRCFAIL;
209 goto bad;
210 } else {
211 /*
212 * Not acting as a router, so
213 * silently drop.
214 */
215 #ifdef IPSTEALTH
216 dropit:
217 #endif
218 IPSTAT_INC(ips_cantforward);
219 m_freem(m);
220 return (1);
221 }
222 }
223
224 /*
225 * locate outgoing interface
226 */
227 (void)memcpy(&ipaddr.sin_addr, cp + off,
228 sizeof(ipaddr.sin_addr));
229
230 if (opt == IPOPT_SSRR) {
231 #define INA struct in_ifaddr *
232 #define SA struct sockaddr *
233 if ((ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr)) == NULL)
234 ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0);
235 } else
236 /* XXX MRT 0 for routing */
237 ia = ip_rtaddr(ipaddr.sin_addr, M_GETFIB(m));
238 if (ia == NULL) {
239 type = ICMP_UNREACH;
240 code = ICMP_UNREACH_SRCFAIL;
241 goto bad;
242 }
243 ip->ip_dst = ipaddr.sin_addr;
244 (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
245 sizeof(struct in_addr));
246 ifa_free(&ia->ia_ifa);
247 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
248 /*
249 * Let ip_intr's mcast routing check handle mcast pkts
250 */
251 forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
252 break;
253
254 case IPOPT_RR:
255 #ifdef IPSTEALTH
256 if (V_ipstealth && pass == 0)
257 break;
258 #endif
259 if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
260 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
261 goto bad;
262 }
263 if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
264 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
265 goto bad;
266 }
267 /*
268 * If no space remains, ignore.
269 */
270 off--; /* 0 origin */
271 if (off > optlen - (int)sizeof(struct in_addr))
272 break;
273 (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
274 sizeof(ipaddr.sin_addr));
275 /*
276 * Locate outgoing interface; if we're the
277 * destination, use the incoming interface (should be
278 * same).
279 */
280 if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) == NULL &&
281 (ia = ip_rtaddr(ipaddr.sin_addr, M_GETFIB(m))) == NULL) {
282 type = ICMP_UNREACH;
283 code = ICMP_UNREACH_HOST;
284 goto bad;
285 }
286 (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
287 sizeof(struct in_addr));
288 ifa_free(&ia->ia_ifa);
289 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
290 break;
291
292 case IPOPT_TS:
293 #ifdef IPSTEALTH
294 if (V_ipstealth && pass == 0)
295 break;
296 #endif
297 code = cp - (u_char *)ip;
298 if (optlen < 4 || optlen > 40) {
299 code = &cp[IPOPT_OLEN] - (u_char *)ip;
300 goto bad;
301 }
302 if ((off = cp[IPOPT_OFFSET]) < 5) {
303 code = &cp[IPOPT_OLEN] - (u_char *)ip;
304 goto bad;
305 }
306 if (off > optlen - (int)sizeof(int32_t)) {
307 cp[IPOPT_OFFSET + 1] += (1 << 4);
308 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
309 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
310 goto bad;
311 }
312 break;
313 }
314 off--; /* 0 origin */
315 sin = (struct in_addr *)(cp + off);
316 switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
317
318 case IPOPT_TS_TSONLY:
319 break;
320
321 case IPOPT_TS_TSANDADDR:
322 if (off + sizeof(uint32_t) +
323 sizeof(struct in_addr) > optlen) {
324 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
325 goto bad;
326 }
327 ipaddr.sin_addr = dst;
328 ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
329 m->m_pkthdr.rcvif);
330 if (ia == NULL)
331 continue;
332 (void)memcpy(sin, &IA_SIN(ia)->sin_addr,
333 sizeof(struct in_addr));
334 ifa_free(&ia->ia_ifa);
335 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
336 off += sizeof(struct in_addr);
337 break;
338
339 case IPOPT_TS_PRESPEC:
340 if (off + sizeof(uint32_t) +
341 sizeof(struct in_addr) > optlen) {
342 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
343 goto bad;
344 }
345 (void)memcpy(&ipaddr.sin_addr, sin,
346 sizeof(struct in_addr));
347 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0)
348 continue;
349 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
350 off += sizeof(struct in_addr);
351 break;
352
353 default:
354 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
355 goto bad;
356 }
357 ntime = iptime();
358 (void)memcpy(cp + off, &ntime, sizeof(uint32_t));
359 cp[IPOPT_OFFSET] += sizeof(uint32_t);
360 }
361 }
362 if (forward && V_ipforwarding) {
363 ip_forward(m, 1);
364 return (1);
365 }
366 return (0);
367 bad:
368 icmp_error(m, type, code, 0, 0);
369 IPSTAT_INC(ips_badoptions);
370 return (1);
371 }
372
373 /*
374 * Save incoming source route for use in replies, to be picked up later by
375 * ip_srcroute if the receiver is interested.
376 */
377 static void
378 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
379 {
380 unsigned olen;
381 struct ipopt_tag *opts;
382
383 opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
384 sizeof(struct ipopt_tag), M_NOWAIT);
385 if (opts == NULL)
386 return;
387
388 olen = option[IPOPT_OLEN];
389 if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
390 m_tag_free((struct m_tag *)opts);
391 return;
392 }
393 bcopy(option, opts->ip_srcrt.srcopt, olen);
394 opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
395 opts->ip_srcrt.dst = dst;
396 m_tag_prepend(m, (struct m_tag *)opts);
397 }
398
399 /*
400 * Retrieve incoming source route for use in replies, in the same form used
401 * by setsockopt. The first hop is placed before the options, will be
402 * removed later.
403 */
404 struct mbuf *
405 ip_srcroute(struct mbuf *m0)
406 {
407 struct in_addr *p, *q;
408 struct mbuf *m;
409 struct ipopt_tag *opts;
410
411 opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
412 if (opts == NULL)
413 return (NULL);
414
415 if (opts->ip_nhops == 0)
416 return (NULL);
417 m = m_get(M_NOWAIT, MT_DATA);
418 if (m == NULL)
419 return (NULL);
420
421 #define OPTSIZ (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
422
423 /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
424 m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
425 sizeof(struct in_addr) + OPTSIZ;
426
427 /*
428 * First, save first hop for return route.
429 */
430 p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
431 *(mtod(m, struct in_addr *)) = *p--;
432
433 /*
434 * Copy option fields and padding (nop) to mbuf.
435 */
436 opts->ip_srcrt.nop = IPOPT_NOP;
437 opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
438 (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
439 &(opts->ip_srcrt.nop), OPTSIZ);
440 q = (struct in_addr *)(mtod(m, caddr_t) +
441 sizeof(struct in_addr) + OPTSIZ);
442 #undef OPTSIZ
443 /*
444 * Record return path as an IP source route, reversing the path
445 * (pointers are now aligned).
446 */
447 while (p >= opts->ip_srcrt.route) {
448 *q++ = *p--;
449 }
450 /*
451 * Last hop goes to final destination.
452 */
453 *q = opts->ip_srcrt.dst;
454 m_tag_delete(m0, (struct m_tag *)opts);
455 return (m);
456 }
457
458 /*
459 * Strip out IP options, at higher level protocol in the kernel.
460 */
461 void
462 ip_stripoptions(struct mbuf *m)
463 {
464 struct ip *ip = mtod(m, struct ip *);
465 int olen;
466
467 olen = (ip->ip_hl << 2) - sizeof(struct ip);
468 m->m_len -= olen;
469 if (m->m_flags & M_PKTHDR)
470 m->m_pkthdr.len -= olen;
471 ip->ip_len = htons(ntohs(ip->ip_len) - olen);
472 ip->ip_hl = sizeof(struct ip) >> 2;
473
474 bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1),
475 (size_t )(m->m_len - sizeof(struct ip)));
476 }
477
478 /*
479 * Insert IP options into preformed packet. Adjust IP destination as
480 * required for IP source routing, as indicated by a non-zero in_addr at the
481 * start of the options.
482 *
483 * XXX This routine assumes that the packet has no options in place.
484 */
485 struct mbuf *
486 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
487 {
488 struct ipoption *p = mtod(opt, struct ipoption *);
489 struct mbuf *n;
490 struct ip *ip = mtod(m, struct ip *);
491 unsigned optlen;
492
493 optlen = opt->m_len - sizeof(p->ipopt_dst);
494 if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) {
495 *phlen = 0;
496 return (m); /* XXX should fail */
497 }
498 if (p->ipopt_dst.s_addr)
499 ip->ip_dst = p->ipopt_dst;
500 if (m->m_flags & M_EXT || m->m_data - optlen < m->m_pktdat) {
501 n = m_gethdr(M_NOWAIT, MT_DATA);
502 if (n == NULL) {
503 *phlen = 0;
504 return (m);
505 }
506 m_move_pkthdr(n, m);
507 n->m_pkthdr.rcvif = NULL;
508 n->m_pkthdr.len += optlen;
509 m->m_len -= sizeof(struct ip);
510 m->m_data += sizeof(struct ip);
511 n->m_next = m;
512 m = n;
513 m->m_len = optlen + sizeof(struct ip);
514 m->m_data += max_linkhdr;
515 bcopy(ip, mtod(m, void *), sizeof(struct ip));
516 } else {
517 m->m_data -= optlen;
518 m->m_len += optlen;
519 m->m_pkthdr.len += optlen;
520 bcopy(ip, mtod(m, void *), sizeof(struct ip));
521 }
522 ip = mtod(m, struct ip *);
523 bcopy(p->ipopt_list, ip + 1, optlen);
524 *phlen = sizeof(struct ip) + optlen;
525 ip->ip_v = IPVERSION;
526 ip->ip_hl = *phlen >> 2;
527 ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
528 return (m);
529 }
530
531 /*
532 * Copy options from ip to jp, omitting those not copied during
533 * fragmentation.
534 */
535 int
536 ip_optcopy(struct ip *ip, struct ip *jp)
537 {
538 u_char *cp, *dp;
539 int opt, optlen, cnt;
540
541 cp = (u_char *)(ip + 1);
542 dp = (u_char *)(jp + 1);
543 cnt = (ip->ip_hl << 2) - sizeof (struct ip);
544 for (; cnt > 0; cnt -= optlen, cp += optlen) {
545 opt = cp[0];
546 if (opt == IPOPT_EOL)
547 break;
548 if (opt == IPOPT_NOP) {
549 /* Preserve for IP mcast tunnel's LSRR alignment. */
550 *dp++ = IPOPT_NOP;
551 optlen = 1;
552 continue;
553 }
554
555 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
556 ("ip_optcopy: malformed ipv4 option"));
557 optlen = cp[IPOPT_OLEN];
558 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
559 ("ip_optcopy: malformed ipv4 option"));
560
561 /* Bogus lengths should have been caught by ip_dooptions. */
562 if (optlen > cnt)
563 optlen = cnt;
564 if (IPOPT_COPIED(opt)) {
565 bcopy(cp, dp, optlen);
566 dp += optlen;
567 }
568 }
569 for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
570 *dp++ = IPOPT_EOL;
571 return (optlen);
572 }
573
574 /*
575 * Set up IP options in pcb for insertion in output packets. Store in mbuf
576 * with pointer in pcbopt, adding pseudo-option with destination address if
577 * source routed.
578 */
579 int
580 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
581 {
582 int cnt, optlen;
583 u_char *cp;
584 struct mbuf **pcbopt;
585 u_char opt;
586
587 INP_WLOCK_ASSERT(inp);
588
589 pcbopt = &inp->inp_options;
590
591 /* turn off any old options */
592 if (*pcbopt)
593 (void)m_free(*pcbopt);
594 *pcbopt = 0;
595 if (m == NULL || m->m_len == 0) {
596 /*
597 * Only turning off any previous options.
598 */
599 if (m != NULL)
600 (void)m_free(m);
601 return (0);
602 }
603
604 if (m->m_len % sizeof(int32_t))
605 goto bad;
606 /*
607 * IP first-hop destination address will be stored before actual
608 * options; move other options back and clear it when none present.
609 */
610 if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
611 goto bad;
612 cnt = m->m_len;
613 m->m_len += sizeof(struct in_addr);
614 cp = mtod(m, u_char *) + sizeof(struct in_addr);
615 bcopy(mtod(m, void *), cp, (unsigned)cnt);
616 bzero(mtod(m, void *), sizeof(struct in_addr));
617
618 for (; cnt > 0; cnt -= optlen, cp += optlen) {
619 opt = cp[IPOPT_OPTVAL];
620 if (opt == IPOPT_EOL)
621 break;
622 if (opt == IPOPT_NOP)
623 optlen = 1;
624 else {
625 if (cnt < IPOPT_OLEN + sizeof(*cp))
626 goto bad;
627 optlen = cp[IPOPT_OLEN];
628 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
629 goto bad;
630 }
631 switch (opt) {
632
633 default:
634 break;
635
636 case IPOPT_LSRR:
637 case IPOPT_SSRR:
638 /*
639 * User process specifies route as:
640 *
641 * ->A->B->C->D
642 *
643 * D must be our final destination (but we can't
644 * check that since we may not have connected yet).
645 * A is first hop destination, which doesn't appear
646 * in actual IP option, but is stored before the
647 * options.
648 */
649 /* XXX-BZ PRIV_NETINET_SETHDROPTS? */
650 if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
651 goto bad;
652 m->m_len -= sizeof(struct in_addr);
653 cnt -= sizeof(struct in_addr);
654 optlen -= sizeof(struct in_addr);
655 cp[IPOPT_OLEN] = optlen;
656 /*
657 * Move first hop before start of options.
658 */
659 bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
660 sizeof(struct in_addr));
661 /*
662 * Then copy rest of options back
663 * to close up the deleted entry.
664 */
665 bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
666 &cp[IPOPT_OFFSET+1],
667 (unsigned)cnt - (IPOPT_MINOFF - 1));
668 break;
669 }
670 }
671 if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
672 goto bad;
673 *pcbopt = m;
674 return (0);
675
676 bad:
677 (void)m_free(m);
678 return (EINVAL);
679 }
680
681 /*
682 * Check for the presence of the IP Router Alert option [RFC2113]
683 * in the header of an IPv4 datagram.
684 *
685 * This call is not intended for use from the forwarding path; it is here
686 * so that protocol domains may check for the presence of the option.
687 * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
688 * option does not have much relevance to the implementation, though this
689 * may change in future.
690 * Router alert options SHOULD be passed if running in IPSTEALTH mode and
691 * we are not the endpoint.
692 * Length checks on individual options should already have been peformed
693 * by ip_dooptions() therefore they are folded under INVARIANTS here.
694 *
695 * Return zero if not present or options are invalid, non-zero if present.
696 */
697 int
698 ip_checkrouteralert(struct mbuf *m)
699 {
700 struct ip *ip = mtod(m, struct ip *);
701 u_char *cp;
702 int opt, optlen, cnt, found_ra;
703
704 found_ra = 0;
705 cp = (u_char *)(ip + 1);
706 cnt = (ip->ip_hl << 2) - sizeof (struct ip);
707 for (; cnt > 0; cnt -= optlen, cp += optlen) {
708 opt = cp[IPOPT_OPTVAL];
709 if (opt == IPOPT_EOL)
710 break;
711 if (opt == IPOPT_NOP)
712 optlen = 1;
713 else {
714 #ifdef INVARIANTS
715 if (cnt < IPOPT_OLEN + sizeof(*cp))
716 break;
717 #endif
718 optlen = cp[IPOPT_OLEN];
719 #ifdef INVARIANTS
720 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
721 break;
722 #endif
723 }
724 switch (opt) {
725 case IPOPT_RA:
726 #ifdef INVARIANTS
727 if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
728 (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
729 break;
730 else
731 #endif
732 found_ra = 1;
733 break;
734 default:
735 break;
736 }
737 }
738
739 return (found_ra);
740 }
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