1 /*
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1982, 1986, 1988, 1993
5 * The Regents of the University of California.
6 * Copyright (c) 2005 Andre Oppermann, Internet Business Solutions AG.
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34 #include <sys/cdefs.h>
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/route/nhop.h>
54 #include <net/netisr.h>
55 #include <net/vnet.h>
56
57 #include <netinet/in.h>
58 #include <netinet/in_fib.h>
59 #include <netinet/in_systm.h>
60 #include <netinet/in_var.h>
61 #include <netinet/ip.h>
62 #include <netinet/in_pcb.h>
63 #include <netinet/ip_var.h>
64 #include <netinet/ip_options.h>
65 #include <netinet/ip_icmp.h>
66 #include <machine/in_cksum.h>
67
68 #include <sys/socketvar.h>
69
70 VNET_DEFINE_STATIC(int, ip_dosourceroute);
71 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute,
72 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_dosourceroute), 0,
73 "Enable forwarding source routed IP packets");
74 #define V_ip_dosourceroute VNET(ip_dosourceroute)
75
76 VNET_DEFINE_STATIC(int, ip_acceptsourceroute);
77 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute,
78 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_acceptsourceroute), 0,
79 "Enable accepting source routed IP packets");
80 #define V_ip_acceptsourceroute VNET(ip_acceptsourceroute)
81
82 VNET_DEFINE(int, ip_doopts) = 1; /* 0 = ignore, 1 = process, 2 = reject */
83 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_VNET | CTLFLAG_RW,
84 &VNET_NAME(ip_doopts), 0, "Enable IP options processing ([LS]SRR, RR, TS)");
85
86 static void save_rte(struct mbuf *m, u_char *, struct in_addr);
87
88 /*
89 * Do option processing on a datagram, possibly discarding it if bad options
90 * are encountered, or forwarding it if source-routed.
91 *
92 * The pass argument is used when operating in the IPSTEALTH mode to tell
93 * what options to process: [LS]SRR (pass 0) or the others (pass 1). The
94 * reason for as many as two passes is that when doing IPSTEALTH, non-routing
95 * options should be processed only if the packet is for us.
96 *
97 * Returns 1 if packet has been forwarded/freed, 0 if the packet should be
98 * processed further.
99 */
100 int
ip_dooptions(struct mbuf * m,int pass)101 ip_dooptions(struct mbuf *m, int pass)
102 {
103 struct ip *ip = mtod(m, struct ip *);
104 u_char *cp;
105 struct in_ifaddr *ia;
106 int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
107 struct in_addr *sin, dst;
108 uint32_t ntime;
109 struct nhop_object *nh;
110 struct sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
111
112 NET_EPOCH_ASSERT();
113
114 /* Ignore or reject packets with IP options. */
115 if (V_ip_doopts == 0)
116 return 0;
117 else if (V_ip_doopts == 2) {
118 type = ICMP_UNREACH;
119 code = ICMP_UNREACH_FILTER_PROHIB;
120 goto bad;
121 }
122
123 dst = ip->ip_dst;
124 cp = (u_char *)(ip + 1);
125 cnt = (ip->ip_hl << 2) - sizeof (struct ip);
126 for (; cnt > 0; cnt -= optlen, cp += optlen) {
127 opt = cp[IPOPT_OPTVAL];
128 if (opt == IPOPT_EOL)
129 break;
130 if (opt == IPOPT_NOP)
131 optlen = 1;
132 else {
133 if (cnt < IPOPT_OLEN + sizeof(*cp)) {
134 code = &cp[IPOPT_OLEN] - (u_char *)ip;
135 goto bad;
136 }
137 optlen = cp[IPOPT_OLEN];
138 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
139 code = &cp[IPOPT_OLEN] - (u_char *)ip;
140 goto bad;
141 }
142 }
143 switch (opt) {
144 default:
145 break;
146
147 /*
148 * Source routing with record. Find interface with current
149 * destination address. If none on this machine then drop if
150 * strictly routed, or do nothing if loosely routed. Record
151 * interface address and bring up next address component. If
152 * strictly routed make sure next address is on directly
153 * accessible net.
154 */
155 case IPOPT_LSRR:
156 case IPOPT_SSRR:
157 #ifdef IPSTEALTH
158 if (V_ipstealth && pass > 0)
159 break;
160 #endif
161 if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
162 code = &cp[IPOPT_OLEN] - (u_char *)ip;
163 goto bad;
164 }
165 if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
166 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
167 goto bad;
168 }
169 ipaddr.sin_addr = ip->ip_dst;
170 if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr)
171 == 0) {
172 if (opt == IPOPT_SSRR) {
173 type = ICMP_UNREACH;
174 code = ICMP_UNREACH_SRCFAIL;
175 goto bad;
176 }
177 if (!V_ip_dosourceroute)
178 goto nosourcerouting;
179 /*
180 * Loose routing, and not at next destination
181 * yet; nothing to do except forward.
182 */
183 break;
184 }
185 off--; /* 0 origin */
186 if (off > optlen - (int)sizeof(struct in_addr)) {
187 /*
188 * End of source route. Should be for us.
189 */
190 if (!V_ip_acceptsourceroute)
191 goto nosourcerouting;
192 save_rte(m, cp, ip->ip_src);
193 break;
194 }
195 #ifdef IPSTEALTH
196 if (V_ipstealth)
197 goto dropit;
198 #endif
199 if (!V_ip_dosourceroute) {
200 if (V_ipforwarding) {
201 char srcbuf[INET_ADDRSTRLEN];
202 char dstbuf[INET_ADDRSTRLEN];
203
204 /*
205 * Acting as a router, so generate
206 * ICMP
207 */
208 nosourcerouting:
209 log(LOG_WARNING,
210 "attempted source route from %s "
211 "to %s\n",
212 inet_ntoa_r(ip->ip_src, srcbuf),
213 inet_ntoa_r(ip->ip_dst, dstbuf));
214 type = ICMP_UNREACH;
215 code = ICMP_UNREACH_SRCFAIL;
216 goto bad;
217 } else {
218 /*
219 * Not acting as a router, so
220 * silently drop.
221 */
222 #ifdef IPSTEALTH
223 dropit:
224 #endif
225 IPSTAT_INC(ips_cantforward);
226 m_freem(m);
227 return (1);
228 }
229 }
230
231 /*
232 * locate outgoing interface
233 */
234 (void)memcpy(&ipaddr.sin_addr, cp + off,
235 sizeof(ipaddr.sin_addr));
236
237 type = ICMP_UNREACH;
238 code = ICMP_UNREACH_SRCFAIL;
239
240 if (opt == IPOPT_SSRR) {
241 #define INA struct in_ifaddr *
242 #define SA struct sockaddr *
243 ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr,
244 RT_ALL_FIBS);
245 if (ia == NULL)
246 ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0,
247 RT_ALL_FIBS);
248 if (ia == NULL)
249 goto bad;
250
251 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
252 sizeof(struct in_addr));
253 } else {
254 /* XXX MRT 0 for routing */
255 nh = fib4_lookup(M_GETFIB(m), ipaddr.sin_addr,
256 0, NHR_NONE, 0);
257 if (nh == NULL)
258 goto bad;
259
260 memcpy(cp + off, &(IA_SIN(nh->nh_ifa)->sin_addr),
261 sizeof(struct in_addr));
262 }
263
264 ip->ip_dst = ipaddr.sin_addr;
265 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
266 /*
267 * Let ip_intr's mcast routing check handle mcast pkts
268 */
269 forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
270 break;
271
272 case IPOPT_RR:
273 #ifdef IPSTEALTH
274 if (V_ipstealth && pass == 0)
275 break;
276 #endif
277 if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
278 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
279 goto bad;
280 }
281 if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
282 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
283 goto bad;
284 }
285 /*
286 * If no space remains, ignore.
287 */
288 off--; /* 0 origin */
289 if (off > optlen - (int)sizeof(struct in_addr))
290 break;
291 (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
292 sizeof(ipaddr.sin_addr));
293 /*
294 * Locate outgoing interface; if we're the
295 * destination, use the incoming interface (should be
296 * same).
297 */
298 if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) != NULL) {
299 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
300 sizeof(struct in_addr));
301 } else if ((nh = fib4_lookup(M_GETFIB(m),
302 ipaddr.sin_addr, 0, NHR_NONE, 0)) != NULL) {
303 memcpy(cp + off, &(IA_SIN(nh->nh_ifa)->sin_addr),
304 sizeof(struct in_addr));
305 } else {
306 type = ICMP_UNREACH;
307 code = ICMP_UNREACH_HOST;
308 goto bad;
309 }
310 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
311 break;
312
313 case IPOPT_TS:
314 #ifdef IPSTEALTH
315 if (V_ipstealth && pass == 0)
316 break;
317 #endif
318 code = cp - (u_char *)ip;
319 if (optlen < 4 || optlen > 40) {
320 code = &cp[IPOPT_OLEN] - (u_char *)ip;
321 goto bad;
322 }
323 if ((off = cp[IPOPT_OFFSET]) < 5) {
324 code = &cp[IPOPT_OLEN] - (u_char *)ip;
325 goto bad;
326 }
327 if (off > optlen - (int)sizeof(int32_t)) {
328 cp[IPOPT_OFFSET + 1] += (1 << 4);
329 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
330 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
331 goto bad;
332 }
333 break;
334 }
335 off--; /* 0 origin */
336 sin = (struct in_addr *)(cp + off);
337 switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
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 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
355 off += sizeof(struct in_addr);
356 break;
357
358 case IPOPT_TS_PRESPEC:
359 if (off + sizeof(uint32_t) +
360 sizeof(struct in_addr) > optlen) {
361 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
362 goto bad;
363 }
364 (void)memcpy(&ipaddr.sin_addr, sin,
365 sizeof(struct in_addr));
366 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0)
367 continue;
368 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
369 off += sizeof(struct in_addr);
370 break;
371
372 default:
373 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
374 goto bad;
375 }
376 ntime = iptime();
377 (void)memcpy(cp + off, &ntime, sizeof(uint32_t));
378 cp[IPOPT_OFFSET] += sizeof(uint32_t);
379 }
380 }
381 if (forward && V_ipforwarding) {
382 ip_forward(m, 1);
383 return (1);
384 }
385 return (0);
386 bad:
387 icmp_error(m, type, code, 0, 0);
388 IPSTAT_INC(ips_badoptions);
389 return (1);
390 }
391
392 /*
393 * Save incoming source route for use in replies, to be picked up later by
394 * ip_srcroute if the receiver is interested.
395 */
396 static void
save_rte(struct mbuf * m,u_char * option,struct in_addr dst)397 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
398 {
399 unsigned olen;
400 struct ipopt_tag *opts;
401
402 opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
403 sizeof(struct ipopt_tag), M_NOWAIT);
404 if (opts == NULL)
405 return;
406
407 olen = option[IPOPT_OLEN];
408 if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
409 m_tag_free((struct m_tag *)opts);
410 return;
411 }
412 bcopy(option, opts->ip_srcrt.srcopt, olen);
413 opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
414 opts->ip_srcrt.dst = dst;
415 m_tag_prepend(m, (struct m_tag *)opts);
416 }
417
418 /*
419 * Retrieve incoming source route for use in replies, in the same form used
420 * by setsockopt. The first hop is placed before the options, will be
421 * removed later.
422 */
423 struct mbuf *
ip_srcroute(struct mbuf * m0)424 ip_srcroute(struct mbuf *m0)
425 {
426 struct in_addr *p, *q;
427 struct mbuf *m;
428 struct ipopt_tag *opts;
429
430 opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
431 if (opts == NULL)
432 return (NULL);
433
434 if (opts->ip_nhops == 0)
435 return (NULL);
436 m = m_get(M_NOWAIT, MT_DATA);
437 if (m == NULL)
438 return (NULL);
439
440 #define OPTSIZ (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
441
442 /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
443 m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
444 sizeof(struct in_addr) + OPTSIZ;
445
446 /*
447 * First, save first hop for return route.
448 */
449 p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
450 *(mtod(m, struct in_addr *)) = *p--;
451
452 /*
453 * Copy option fields and padding (nop) to mbuf.
454 */
455 opts->ip_srcrt.nop = IPOPT_NOP;
456 opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
457 (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
458 &(opts->ip_srcrt.nop), OPTSIZ);
459 q = (struct in_addr *)(mtod(m, caddr_t) +
460 sizeof(struct in_addr) + OPTSIZ);
461 #undef OPTSIZ
462 /*
463 * Record return path as an IP source route, reversing the path
464 * (pointers are now aligned).
465 */
466 while (p >= opts->ip_srcrt.route) {
467 *q++ = *p--;
468 }
469 /*
470 * Last hop goes to final destination.
471 */
472 *q = opts->ip_srcrt.dst;
473 m_tag_delete(m0, (struct m_tag *)opts);
474 return (m);
475 }
476
477 /*
478 * Strip out IP options, at higher level protocol in the kernel.
479 */
480 void
ip_stripoptions(struct mbuf * m)481 ip_stripoptions(struct mbuf *m)
482 {
483 struct ip *ip = mtod(m, struct ip *);
484 int olen;
485
486 olen = (ip->ip_hl << 2) - sizeof(struct ip);
487 m->m_len -= olen;
488 if (m->m_flags & M_PKTHDR)
489 m->m_pkthdr.len -= olen;
490 ip->ip_len = htons(ntohs(ip->ip_len) - olen);
491 ip->ip_hl = sizeof(struct ip) >> 2;
492
493 bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1),
494 (size_t )(m->m_len - sizeof(struct ip)));
495 }
496
497 /*
498 * Insert IP options into preformed packet. Adjust IP destination as
499 * required for IP source routing, as indicated by a non-zero in_addr at the
500 * start of the options.
501 *
502 * XXX This routine assumes that the packet has no options in place.
503 */
504 struct mbuf *
ip_insertoptions(struct mbuf * m,struct mbuf * opt,int * phlen)505 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
506 {
507 struct ipoption *p = mtod(opt, struct ipoption *);
508 struct mbuf *n;
509 struct ip *ip = mtod(m, struct ip *);
510 unsigned optlen;
511
512 optlen = opt->m_len - sizeof(p->ipopt_dst);
513 if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) {
514 *phlen = 0;
515 return (m); /* XXX should fail */
516 }
517 KASSERT((m->m_flags & M_EXTPG) == 0, ("%s: mbuf %p is unmapped",
518 __func__, m));
519 if (p->ipopt_dst.s_addr)
520 ip->ip_dst = p->ipopt_dst;
521 if (!M_WRITABLE(m) || M_LEADINGSPACE(m) < optlen) {
522 n = m_gethdr(M_NOWAIT, MT_DATA);
523 if (n == NULL) {
524 *phlen = 0;
525 return (m);
526 }
527 m_move_pkthdr(n, m);
528 n->m_pkthdr.rcvif = NULL;
529 n->m_pkthdr.len += optlen;
530 m->m_len -= sizeof(struct ip);
531 m->m_data += sizeof(struct ip);
532 n->m_next = m;
533 m = n;
534 m->m_len = optlen + sizeof(struct ip);
535 m->m_data += max_linkhdr;
536 bcopy(ip, mtod(m, void *), sizeof(struct ip));
537 } else {
538 m->m_data -= optlen;
539 m->m_len += optlen;
540 m->m_pkthdr.len += optlen;
541 bcopy(ip, mtod(m, void *), sizeof(struct ip));
542 }
543 ip = mtod(m, struct ip *);
544 bcopy(p->ipopt_list, ip + 1, optlen);
545 *phlen = sizeof(struct ip) + optlen;
546 ip->ip_v = IPVERSION;
547 ip->ip_hl = *phlen >> 2;
548 ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
549 return (m);
550 }
551
552 /*
553 * Copy options from ip to jp, omitting those not copied during
554 * fragmentation.
555 */
556 int
ip_optcopy(struct ip * ip,struct ip * jp)557 ip_optcopy(struct ip *ip, struct ip *jp)
558 {
559 u_char *cp, *dp;
560 int opt, optlen, cnt;
561
562 cp = (u_char *)(ip + 1);
563 dp = (u_char *)(jp + 1);
564 cnt = (ip->ip_hl << 2) - sizeof (struct ip);
565 for (; cnt > 0; cnt -= optlen, cp += optlen) {
566 opt = cp[0];
567 if (opt == IPOPT_EOL)
568 break;
569 if (opt == IPOPT_NOP) {
570 /* Preserve for IP mcast tunnel's LSRR alignment. */
571 *dp++ = IPOPT_NOP;
572 optlen = 1;
573 continue;
574 }
575
576 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
577 ("ip_optcopy: malformed ipv4 option"));
578 optlen = cp[IPOPT_OLEN];
579 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
580 ("ip_optcopy: malformed ipv4 option"));
581
582 /* Bogus lengths should have been caught by ip_dooptions. */
583 if (optlen > cnt)
584 optlen = cnt;
585 if (IPOPT_COPIED(opt)) {
586 bcopy(cp, dp, optlen);
587 dp += optlen;
588 }
589 }
590 for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
591 *dp++ = IPOPT_EOL;
592 return (optlen);
593 }
594
595 /*
596 * Set up IP options in pcb for insertion in output packets. Store in mbuf
597 * with pointer in pcbopt, adding pseudo-option with destination address if
598 * source routed.
599 */
600 int
ip_pcbopts(struct inpcb * inp,int optname,struct mbuf * m)601 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
602 {
603 int cnt, optlen;
604 u_char *cp;
605 struct mbuf **pcbopt;
606 u_char opt;
607
608 INP_WLOCK_ASSERT(inp);
609
610 pcbopt = &inp->inp_options;
611
612 /* turn off any old options */
613 if (*pcbopt)
614 (void)m_free(*pcbopt);
615 *pcbopt = NULL;
616 if (m == NULL || m->m_len == 0) {
617 /*
618 * Only turning off any previous options.
619 */
620 if (m != NULL)
621 (void)m_free(m);
622 return (0);
623 }
624
625 if (m->m_len % sizeof(int32_t))
626 goto bad;
627 /*
628 * IP first-hop destination address will be stored before actual
629 * options; move other options back and clear it when none present.
630 */
631 if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
632 goto bad;
633 cnt = m->m_len;
634 m->m_len += sizeof(struct in_addr);
635 cp = mtod(m, u_char *) + sizeof(struct in_addr);
636 bcopy(mtod(m, void *), cp, (unsigned)cnt);
637 bzero(mtod(m, void *), sizeof(struct in_addr));
638
639 for (; cnt > 0; cnt -= optlen, cp += optlen) {
640 opt = cp[IPOPT_OPTVAL];
641 if (opt == IPOPT_EOL)
642 break;
643 if (opt == IPOPT_NOP)
644 optlen = 1;
645 else {
646 if (cnt < IPOPT_OLEN + sizeof(*cp))
647 goto bad;
648 optlen = cp[IPOPT_OLEN];
649 if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
650 goto bad;
651 }
652 switch (opt) {
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
ip_checkrouteralert(struct mbuf * m)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 }
761