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__FBSDID("$FreeBSD$");
36
37#include "opt_ipstealth.h"
38
39#include <sys/param.h>
40#include <sys/systm.h>
41#include <sys/mbuf.h>
42#include <sys/domain.h>
43#include <sys/protosw.h>
44#include <sys/socket.h>
45#include <sys/time.h>
46#include <sys/kernel.h>
47#include <sys/syslog.h>
48#include <sys/sysctl.h>
49
50#include <net/if.h>
51#include <net/if_types.h>
52#include <net/if_var.h>
53#include <net/if_dl.h>
54#include <net/route.h>
55#include <net/netisr.h>
56#include <net/vnet.h>
57
58#include <netinet/in.h>
59#include <netinet/in_fib.h>
60#include <netinet/in_systm.h>
61#include <netinet/in_var.h>
62#include <netinet/ip.h>
63#include <netinet/in_pcb.h>
64#include <netinet/ip_var.h>
65#include <netinet/ip_options.h>
66#include <netinet/ip_icmp.h>
67#include <machine/in_cksum.h>
68
69#include <sys/socketvar.h>
70
71VNET_DEFINE_STATIC(int, ip_dosourceroute);
72SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute,
73    CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_dosourceroute), 0,
74    "Enable forwarding source routed IP packets");
75#define	V_ip_dosourceroute	VNET(ip_dosourceroute)
76
77VNET_DEFINE_STATIC(int,	ip_acceptsourceroute);
78SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute,
79    CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_acceptsourceroute), 0,
80    "Enable accepting source routed IP packets");
81#define	V_ip_acceptsourceroute	VNET(ip_acceptsourceroute)
82
83VNET_DEFINE(int, ip_doopts) = 1; /* 0 = ignore, 1 = process, 2 = reject */
84SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_VNET | CTLFLAG_RW,
85    &VNET_NAME(ip_doopts), 0, "Enable IP options processing ([LS]SRR, RR, TS)");
86
87static void	save_rte(struct mbuf *m, u_char *, struct in_addr);
88
89/*
90 * Do option processing on a datagram, possibly discarding it if bad options
91 * are encountered, or forwarding it if source-routed.
92 *
93 * The pass argument is used when operating in the IPSTEALTH mode to tell
94 * what options to process: [LS]SRR (pass 0) or the others (pass 1).  The
95 * reason for as many as two passes is that when doing IPSTEALTH, non-routing
96 * options should be processed only if the packet is for us.
97 *
98 * Returns 1 if packet has been forwarded/freed, 0 if the packet should be
99 * processed further.
100 */
101int
102ip_dooptions(struct mbuf *m, int pass)
103{
104	struct ip *ip = mtod(m, struct ip *);
105	u_char *cp;
106	struct in_ifaddr *ia;
107	int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
108	struct in_addr *sin, dst;
109	uint32_t ntime;
110	struct nhop4_extended nh_ext;
111	struct	sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
112
113	/* Ignore or reject packets with IP options. */
114	if (V_ip_doopts == 0)
115		return 0;
116	else if (V_ip_doopts == 2) {
117		type = ICMP_UNREACH;
118		code = ICMP_UNREACH_FILTER_PROHIB;
119		goto bad_unlocked;
120	}
121
122	NET_EPOCH_ENTER();
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
145		default:
146			break;
147
148		/*
149		 * Source routing with record.  Find interface with current
150		 * destination address.  If none on this machine then drop if
151		 * strictly routed, or do nothing if loosely routed.  Record
152		 * interface address and bring up next address component.  If
153		 * strictly routed make sure next address is on directly
154		 * accessible net.
155		 */
156		case IPOPT_LSRR:
157		case IPOPT_SSRR:
158#ifdef IPSTEALTH
159			if (V_ipstealth && pass > 0)
160				break;
161#endif
162			if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
163				code = &cp[IPOPT_OLEN] - (u_char *)ip;
164				goto bad;
165			}
166			if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
167				code = &cp[IPOPT_OFFSET] - (u_char *)ip;
168				goto bad;
169			}
170			ipaddr.sin_addr = ip->ip_dst;
171			if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr)
172			    == 0) {
173				if (opt == IPOPT_SSRR) {
174					type = ICMP_UNREACH;
175					code = ICMP_UNREACH_SRCFAIL;
176					goto bad;
177				}
178				if (!V_ip_dosourceroute)
179					goto nosourcerouting;
180				/*
181				 * Loose routing, and not at next destination
182				 * yet; nothing to do except forward.
183				 */
184				break;
185			}
186			off--;			/* 0 origin */
187			if (off > optlen - (int)sizeof(struct in_addr)) {
188				/*
189				 * End of source route.  Should be for us.
190				 */
191				if (!V_ip_acceptsourceroute)
192					goto nosourcerouting;
193				save_rte(m, cp, ip->ip_src);
194				break;
195			}
196#ifdef IPSTEALTH
197			if (V_ipstealth)
198				goto dropit;
199#endif
200			if (!V_ip_dosourceroute) {
201				if (V_ipforwarding) {
202					char srcbuf[INET_ADDRSTRLEN];
203					char dstbuf[INET_ADDRSTRLEN];
204
205					/*
206					 * Acting as a router, so generate
207					 * ICMP
208					 */
209nosourcerouting:
210					log(LOG_WARNING,
211					    "attempted source route from %s "
212					    "to %s\n",
213					    inet_ntoa_r(ip->ip_src, srcbuf),
214					    inet_ntoa_r(ip->ip_dst, dstbuf));
215					type = ICMP_UNREACH;
216					code = ICMP_UNREACH_SRCFAIL;
217					goto bad;
218				} else {
219					/*
220					 * Not acting as a router, so
221					 * silently drop.
222					 */
223#ifdef IPSTEALTH
224dropit:
225#endif
226					IPSTAT_INC(ips_cantforward);
227					m_freem(m);
228					NET_EPOCH_EXIT();
229					return (1);
230				}
231			}
232
233			/*
234			 * locate outgoing interface
235			 */
236			(void)memcpy(&ipaddr.sin_addr, cp + off,
237			    sizeof(ipaddr.sin_addr));
238
239			type = ICMP_UNREACH;
240			code = ICMP_UNREACH_SRCFAIL;
241
242			if (opt == IPOPT_SSRR) {
243#define	INA	struct in_ifaddr *
244#define	SA	struct sockaddr *
245			    ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr,
246					    RT_ALL_FIBS);
247			    if (ia == NULL)
248				    ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0,
249						    RT_ALL_FIBS);
250				if (ia == NULL)
251					goto bad;
252
253				memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
254				    sizeof(struct in_addr));
255			} else {
256				/* XXX MRT 0 for routing */
257				if (fib4_lookup_nh_ext(M_GETFIB(m),
258				    ipaddr.sin_addr, 0, 0, &nh_ext) != 0)
259					goto bad;
260
261				memcpy(cp + off, &nh_ext.nh_src,
262				    sizeof(struct in_addr));
263			}
264
265			ip->ip_dst = ipaddr.sin_addr;
266			cp[IPOPT_OFFSET] += sizeof(struct in_addr);
267			/*
268			 * Let ip_intr's mcast routing check handle mcast pkts
269			 */
270			forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
271			break;
272
273		case IPOPT_RR:
274#ifdef IPSTEALTH
275			if (V_ipstealth && pass == 0)
276				break;
277#endif
278			if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
279				code = &cp[IPOPT_OFFSET] - (u_char *)ip;
280				goto bad;
281			}
282			if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
283				code = &cp[IPOPT_OFFSET] - (u_char *)ip;
284				goto bad;
285			}
286			/*
287			 * If no space remains, ignore.
288			 */
289			off--;			/* 0 origin */
290			if (off > optlen - (int)sizeof(struct in_addr))
291				break;
292			(void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
293			    sizeof(ipaddr.sin_addr));
294			/*
295			 * Locate outgoing interface; if we're the
296			 * destination, use the incoming interface (should be
297			 * same).
298			 */
299			if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) != NULL) {
300				memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
301				    sizeof(struct in_addr));
302			} else if (fib4_lookup_nh_ext(M_GETFIB(m),
303			    ipaddr.sin_addr, 0, 0, &nh_ext) == 0) {
304				memcpy(cp + off, &nh_ext.nh_src,
305				    sizeof(struct in_addr));
306			} else {
307				type = ICMP_UNREACH;
308				code = ICMP_UNREACH_HOST;
309				goto bad;
310			}
311			cp[IPOPT_OFFSET] += sizeof(struct in_addr);
312			break;
313
314		case IPOPT_TS:
315#ifdef IPSTEALTH
316			if (V_ipstealth && pass == 0)
317				break;
318#endif
319			code = cp - (u_char *)ip;
320			if (optlen < 4 || optlen > 40) {
321				code = &cp[IPOPT_OLEN] - (u_char *)ip;
322				goto bad;
323			}
324			if ((off = cp[IPOPT_OFFSET]) < 5) {
325				code = &cp[IPOPT_OLEN] - (u_char *)ip;
326				goto bad;
327			}
328			if (off > optlen - (int)sizeof(int32_t)) {
329				cp[IPOPT_OFFSET + 1] += (1 << 4);
330				if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
331					code = &cp[IPOPT_OFFSET] - (u_char *)ip;
332					goto bad;
333				}
334				break;
335			}
336			off--;				/* 0 origin */
337			sin = (struct in_addr *)(cp + off);
338			switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
339
340			case IPOPT_TS_TSONLY:
341				break;
342
343			case IPOPT_TS_TSANDADDR:
344				if (off + sizeof(uint32_t) +
345				    sizeof(struct in_addr) > optlen) {
346					code = &cp[IPOPT_OFFSET] - (u_char *)ip;
347					goto bad;
348				}
349				ipaddr.sin_addr = dst;
350				ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
351							    m->m_pkthdr.rcvif);
352				if (ia == NULL)
353					continue;
354				(void)memcpy(sin, &IA_SIN(ia)->sin_addr,
355				    sizeof(struct in_addr));
356				cp[IPOPT_OFFSET] += sizeof(struct in_addr);
357				off += sizeof(struct in_addr);
358				break;
359
360			case IPOPT_TS_PRESPEC:
361				if (off + sizeof(uint32_t) +
362				    sizeof(struct in_addr) > optlen) {
363					code = &cp[IPOPT_OFFSET] - (u_char *)ip;
364					goto bad;
365				}
366				(void)memcpy(&ipaddr.sin_addr, sin,
367				    sizeof(struct in_addr));
368				if (ifa_ifwithaddr_check((SA)&ipaddr) == 0)
369					continue;
370				cp[IPOPT_OFFSET] += sizeof(struct in_addr);
371				off += sizeof(struct in_addr);
372				break;
373
374			default:
375				code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
376				goto bad;
377			}
378			ntime = iptime();
379			(void)memcpy(cp + off, &ntime, sizeof(uint32_t));
380			cp[IPOPT_OFFSET] += sizeof(uint32_t);
381		}
382	}
383	NET_EPOCH_EXIT();
384	if (forward && V_ipforwarding) {
385		ip_forward(m, 1);
386		return (1);
387	}
388	return (0);
389bad:
390	NET_EPOCH_EXIT();
391bad_unlocked:
392	icmp_error(m, type, code, 0, 0);
393	IPSTAT_INC(ips_badoptions);
394	return (1);
395}
396
397/*
398 * Save incoming source route for use in replies, to be picked up later by
399 * ip_srcroute if the receiver is interested.
400 */
401static void
402save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
403{
404	unsigned olen;
405	struct ipopt_tag *opts;
406
407	opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
408	    sizeof(struct ipopt_tag), M_NOWAIT);
409	if (opts == NULL)
410		return;
411
412	olen = option[IPOPT_OLEN];
413	if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
414		m_tag_free((struct m_tag *)opts);
415		return;
416	}
417	bcopy(option, opts->ip_srcrt.srcopt, olen);
418	opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
419	opts->ip_srcrt.dst = dst;
420	m_tag_prepend(m, (struct m_tag *)opts);
421}
422
423/*
424 * Retrieve incoming source route for use in replies, in the same form used
425 * by setsockopt.  The first hop is placed before the options, will be
426 * removed later.
427 */
428struct mbuf *
429ip_srcroute(struct mbuf *m0)
430{
431	struct in_addr *p, *q;
432	struct mbuf *m;
433	struct ipopt_tag *opts;
434
435	opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
436	if (opts == NULL)
437		return (NULL);
438
439	if (opts->ip_nhops == 0)
440		return (NULL);
441	m = m_get(M_NOWAIT, MT_DATA);
442	if (m == NULL)
443		return (NULL);
444
445#define OPTSIZ	(sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
446
447	/* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
448	m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
449	    sizeof(struct in_addr) + OPTSIZ;
450
451	/*
452	 * First, save first hop for return route.
453	 */
454	p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
455	*(mtod(m, struct in_addr *)) = *p--;
456
457	/*
458	 * Copy option fields and padding (nop) to mbuf.
459	 */
460	opts->ip_srcrt.nop = IPOPT_NOP;
461	opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
462	(void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
463	    &(opts->ip_srcrt.nop), OPTSIZ);
464	q = (struct in_addr *)(mtod(m, caddr_t) +
465	    sizeof(struct in_addr) + OPTSIZ);
466#undef OPTSIZ
467	/*
468	 * Record return path as an IP source route, reversing the path
469	 * (pointers are now aligned).
470	 */
471	while (p >= opts->ip_srcrt.route) {
472		*q++ = *p--;
473	}
474	/*
475	 * Last hop goes to final destination.
476	 */
477	*q = opts->ip_srcrt.dst;
478	m_tag_delete(m0, (struct m_tag *)opts);
479	return (m);
480}
481
482/*
483 * Strip out IP options, at higher level protocol in the kernel.
484 */
485void
486ip_stripoptions(struct mbuf *m)
487{
488	struct ip *ip = mtod(m, struct ip *);
489	int olen;
490
491	olen = (ip->ip_hl << 2) - sizeof(struct ip);
492	m->m_len -= olen;
493	if (m->m_flags & M_PKTHDR)
494		m->m_pkthdr.len -= olen;
495	ip->ip_len = htons(ntohs(ip->ip_len) - olen);
496	ip->ip_hl = sizeof(struct ip) >> 2;
497
498	bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1),
499	    (size_t )(m->m_len - sizeof(struct ip)));
500}
501
502/*
503 * Insert IP options into preformed packet.  Adjust IP destination as
504 * required for IP source routing, as indicated by a non-zero in_addr at the
505 * start of the options.
506 *
507 * XXX This routine assumes that the packet has no options in place.
508 */
509struct mbuf *
510ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
511{
512	struct ipoption *p = mtod(opt, struct ipoption *);
513	struct mbuf *n;
514	struct ip *ip = mtod(m, struct ip *);
515	unsigned optlen;
516
517	optlen = opt->m_len - sizeof(p->ipopt_dst);
518	if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) {
519		*phlen = 0;
520		return (m);		/* XXX should fail */
521	}
522	if (p->ipopt_dst.s_addr)
523		ip->ip_dst = p->ipopt_dst;
524	if (!M_WRITABLE(m) || M_LEADINGSPACE(m) < optlen) {
525		n = m_gethdr(M_NOWAIT, MT_DATA);
526		if (n == NULL) {
527			*phlen = 0;
528			return (m);
529		}
530		m_move_pkthdr(n, m);
531		n->m_pkthdr.rcvif = NULL;
532		n->m_pkthdr.len += optlen;
533		m->m_len -= sizeof(struct ip);
534		m->m_data += sizeof(struct ip);
535		n->m_next = m;
536		m = n;
537		m->m_len = optlen + sizeof(struct ip);
538		m->m_data += max_linkhdr;
539		bcopy(ip, mtod(m, void *), sizeof(struct ip));
540	} else {
541		m->m_data -= optlen;
542		m->m_len += optlen;
543		m->m_pkthdr.len += optlen;
544		bcopy(ip, mtod(m, void *), sizeof(struct ip));
545	}
546	ip = mtod(m, struct ip *);
547	bcopy(p->ipopt_list, ip + 1, optlen);
548	*phlen = sizeof(struct ip) + optlen;
549	ip->ip_v = IPVERSION;
550	ip->ip_hl = *phlen >> 2;
551	ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
552	return (m);
553}
554
555/*
556 * Copy options from ip to jp, omitting those not copied during
557 * fragmentation.
558 */
559int
560ip_optcopy(struct ip *ip, struct ip *jp)
561{
562	u_char *cp, *dp;
563	int opt, optlen, cnt;
564
565	cp = (u_char *)(ip + 1);
566	dp = (u_char *)(jp + 1);
567	cnt = (ip->ip_hl << 2) - sizeof (struct ip);
568	for (; cnt > 0; cnt -= optlen, cp += optlen) {
569		opt = cp[0];
570		if (opt == IPOPT_EOL)
571			break;
572		if (opt == IPOPT_NOP) {
573			/* Preserve for IP mcast tunnel's LSRR alignment. */
574			*dp++ = IPOPT_NOP;
575			optlen = 1;
576			continue;
577		}
578
579		KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
580		    ("ip_optcopy: malformed ipv4 option"));
581		optlen = cp[IPOPT_OLEN];
582		KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
583		    ("ip_optcopy: malformed ipv4 option"));
584
585		/* Bogus lengths should have been caught by ip_dooptions. */
586		if (optlen > cnt)
587			optlen = cnt;
588		if (IPOPT_COPIED(opt)) {
589			bcopy(cp, dp, optlen);
590			dp += optlen;
591		}
592	}
593	for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
594		*dp++ = IPOPT_EOL;
595	return (optlen);
596}
597
598/*
599 * Set up IP options in pcb for insertion in output packets.  Store in mbuf
600 * with pointer in pcbopt, adding pseudo-option with destination address if
601 * source routed.
602 */
603int
604ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
605{
606	int cnt, optlen;
607	u_char *cp;
608	struct mbuf **pcbopt;
609	u_char opt;
610
611	INP_WLOCK_ASSERT(inp);
612
613	pcbopt = &inp->inp_options;
614
615	/* turn off any old options */
616	if (*pcbopt)
617		(void)m_free(*pcbopt);
618	*pcbopt = NULL;
619	if (m == NULL || m->m_len == 0) {
620		/*
621		 * Only turning off any previous options.
622		 */
623		if (m != NULL)
624			(void)m_free(m);
625		return (0);
626	}
627
628	if (m->m_len % sizeof(int32_t))
629		goto bad;
630	/*
631	 * IP first-hop destination address will be stored before actual
632	 * options; move other options back and clear it when none present.
633	 */
634	if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
635		goto bad;
636	cnt = m->m_len;
637	m->m_len += sizeof(struct in_addr);
638	cp = mtod(m, u_char *) + sizeof(struct in_addr);
639	bcopy(mtod(m, void *), cp, (unsigned)cnt);
640	bzero(mtod(m, void *), sizeof(struct in_addr));
641
642	for (; cnt > 0; cnt -= optlen, cp += optlen) {
643		opt = cp[IPOPT_OPTVAL];
644		if (opt == IPOPT_EOL)
645			break;
646		if (opt == IPOPT_NOP)
647			optlen = 1;
648		else {
649			if (cnt < IPOPT_OLEN + sizeof(*cp))
650				goto bad;
651			optlen = cp[IPOPT_OLEN];
652			if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
653				goto bad;
654		}
655		switch (opt) {
656
657		default:
658			break;
659
660		case IPOPT_LSRR:
661		case IPOPT_SSRR:
662			/*
663			 * User process specifies route as:
664			 *
665			 *	->A->B->C->D
666			 *
667			 * D must be our final destination (but we can't
668			 * check that since we may not have connected yet).
669			 * A is first hop destination, which doesn't appear
670			 * in actual IP option, but is stored before the
671			 * options.
672			 */
673			/* XXX-BZ PRIV_NETINET_SETHDROPTS? */
674			if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
675				goto bad;
676			m->m_len -= sizeof(struct in_addr);
677			cnt -= sizeof(struct in_addr);
678			optlen -= sizeof(struct in_addr);
679			cp[IPOPT_OLEN] = optlen;
680			/*
681			 * Move first hop before start of options.
682			 */
683			bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
684			    sizeof(struct in_addr));
685			/*
686			 * Then copy rest of options back
687			 * to close up the deleted entry.
688			 */
689			bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
690			    &cp[IPOPT_OFFSET+1],
691			    (unsigned)cnt - (IPOPT_MINOFF - 1));
692			break;
693		}
694	}
695	if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
696		goto bad;
697	*pcbopt = m;
698	return (0);
699
700bad:
701	(void)m_free(m);
702	return (EINVAL);
703}
704
705/*
706 * Check for the presence of the IP Router Alert option [RFC2113]
707 * in the header of an IPv4 datagram.
708 *
709 * This call is not intended for use from the forwarding path; it is here
710 * so that protocol domains may check for the presence of the option.
711 * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
712 * option does not have much relevance to the implementation, though this
713 * may change in future.
714 * Router alert options SHOULD be passed if running in IPSTEALTH mode and
715 * we are not the endpoint.
716 * Length checks on individual options should already have been performed
717 * by ip_dooptions() therefore they are folded under INVARIANTS here.
718 *
719 * Return zero if not present or options are invalid, non-zero if present.
720 */
721int
722ip_checkrouteralert(struct mbuf *m)
723{
724	struct ip *ip = mtod(m, struct ip *);
725	u_char *cp;
726	int opt, optlen, cnt, found_ra;
727
728	found_ra = 0;
729	cp = (u_char *)(ip + 1);
730	cnt = (ip->ip_hl << 2) - sizeof (struct ip);
731	for (; cnt > 0; cnt -= optlen, cp += optlen) {
732		opt = cp[IPOPT_OPTVAL];
733		if (opt == IPOPT_EOL)
734			break;
735		if (opt == IPOPT_NOP)
736			optlen = 1;
737		else {
738#ifdef INVARIANTS
739			if (cnt < IPOPT_OLEN + sizeof(*cp))
740				break;
741#endif
742			optlen = cp[IPOPT_OLEN];
743#ifdef INVARIANTS
744			if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
745				break;
746#endif
747		}
748		switch (opt) {
749		case IPOPT_RA:
750#ifdef INVARIANTS
751			if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
752			    (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
753			    break;
754			else
755#endif
756			found_ra = 1;
757			break;
758		default:
759			break;
760		}
761	}
762
763	return (found_ra);
764}
765