sys/netinet/ip_options.c

   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
 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
 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 *
 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
 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 *
 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         if (p->ipopt_dst.s_addr)
 518                 ip->ip_dst = p->ipopt_dst;
 519         if (!M_WRITABLE(m) || M_LEADINGSPACE(m) < optlen) {
 520                 n = m_gethdr(M_NOWAIT, MT_DATA);
 521                 if (n == NULL) {
 522                         *phlen = 0;
 523                         return (m);
 524                 }
 525                 m_move_pkthdr(n, m);
 526                 n->m_pkthdr.rcvif = NULL;
 527                 n->m_pkthdr.len += optlen;
 528                 m->m_len -= sizeof(struct ip);
 529                 m->m_data += sizeof(struct ip);
 530                 n->m_next = m;
 531                 m = n;
 532                 m->m_len = optlen + sizeof(struct ip);
 533                 m->m_data += max_linkhdr;
 534                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 535         } else {
 536                 m->m_data -= optlen;
 537                 m->m_len += optlen;
 538                 m->m_pkthdr.len += optlen;
 539                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 540         }
 541         ip = mtod(m, struct ip *);
 542         bcopy(p->ipopt_list, ip + 1, optlen);
 543         *phlen = sizeof(struct ip) + optlen;
 544         ip->ip_v = IPVERSION;
 545         ip->ip_hl = *phlen >> 2;
 546         ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
 547         return (m);
 548 }
 549
 550 /*
 551  * Copy options from ip to jp, omitting those not copied during
 552  * fragmentation.
 553  */
 554 int
 555 ip_optcopy(struct ip *ip, struct ip *jp)
 556 {
 557         u_char *cp, *dp;
 558         int opt, optlen, cnt;
 559
 560         cp = (u_char *)(ip + 1);
 561         dp = (u_char *)(jp + 1);
 562         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 563         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 564                 opt = cp[0];
 565                 if (opt == IPOPT_EOL)
 566                         break;
 567                 if (opt == IPOPT_NOP) {
 568                         /* Preserve for IP mcast tunnel's LSRR alignment. */
 569                         *dp++ = IPOPT_NOP;
 570                         optlen = 1;
 571                         continue;
 572                 }
 573
 574                 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
 575                     ("ip_optcopy: malformed ipv4 option"));
 576                 optlen = cp[IPOPT_OLEN];
 577                 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
 578                     ("ip_optcopy: malformed ipv4 option"));
 579
 580                 /* Bogus lengths should have been caught by ip_dooptions. */
 581                 if (optlen > cnt)
 582                         optlen = cnt;
 583                 if (IPOPT_COPIED(opt)) {
 584                         bcopy(cp, dp, optlen);
 585                         dp += optlen;
 586                 }
 587         }
 588         for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
 589                 *dp++ = IPOPT_EOL;
 590         return (optlen);
 591 }
 592
 593 /*
 594  * Set up IP options in pcb for insertion in output packets.  Store in mbuf
 595  * with pointer in pcbopt, adding pseudo-option with destination address if
 596  * source routed.
 597  */
 598 int
 599 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
 600 {
 601         int cnt, optlen;
 602         u_char *cp;
 603         struct mbuf **pcbopt;
 604         u_char opt;
 605
 606         INP_WLOCK_ASSERT(inp);
 607
 608         pcbopt = &inp->inp_options;
 609
 610         /* turn off any old options */
 611         if (*pcbopt)
 612                 (void)m_free(*pcbopt);
 613         *pcbopt = NULL;
 614         if (m == NULL || m->m_len == 0) {
 615                 /*
 616                  * Only turning off any previous options.
 617                  */
 618                 if (m != NULL)
 619                         (void)m_free(m);
 620                 return (0);
 621         }
 622
 623         if (m->m_len % sizeof(int32_t))
 624                 goto bad;
 625         /*
 626          * IP first-hop destination address will be stored before actual
 627          * options; move other options back and clear it when none present.
 628          */
 629         if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
 630                 goto bad;
 631         cnt = m->m_len;
 632         m->m_len += sizeof(struct in_addr);
 633         cp = mtod(m, u_char *) + sizeof(struct in_addr);
 634         bcopy(mtod(m, void *), cp, (unsigned)cnt);
 635         bzero(mtod(m, void *), sizeof(struct in_addr));
 636
 637         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 638                 opt = cp[IPOPT_OPTVAL];
 639                 if (opt == IPOPT_EOL)
 640                         break;
 641                 if (opt == IPOPT_NOP)
 642                         optlen = 1;
 643                 else {
 644                         if (cnt < IPOPT_OLEN + sizeof(*cp))
 645                                 goto bad;
 646                         optlen = cp[IPOPT_OLEN];
 647                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
 648                                 goto bad;
 649                 }
 650                 switch (opt) {
 651                 default:
 652                         break;
 653
 654                 case IPOPT_LSRR:
 655                 case IPOPT_SSRR:
 656                         /*
 657                          * User process specifies route as:
 658                          *
 659                          *      ->A->B->C->D
 660                          *
 661                          * D must be our final destination (but we can't
 662                          * check that since we may not have connected yet).
 663                          * A is first hop destination, which doesn't appear
 664                          * in actual IP option, but is stored before the
 665                          * options.
 666                          */
 667                         /* XXX-BZ PRIV_NETINET_SETHDROPTS? */
 668                         if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
 669                                 goto bad;
 670                         m->m_len -= sizeof(struct in_addr);
 671                         cnt -= sizeof(struct in_addr);
 672                         optlen -= sizeof(struct in_addr);
 673                         cp[IPOPT_OLEN] = optlen;
 674                         /*
 675                          * Move first hop before start of options.
 676                          */
 677                         bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
 678                             sizeof(struct in_addr));
 679                         /*
 680                          * Then copy rest of options back
 681                          * to close up the deleted entry.
 682                          */
 683                         bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
 684                             &cp[IPOPT_OFFSET+1],
 685                             (unsigned)cnt - (IPOPT_MINOFF - 1));
 686                         break;
 687                 }
 688         }
 689         if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
 690                 goto bad;
 691         *pcbopt = m;
 692         return (0);
 693
 694 bad:
 695         (void)m_free(m);
 696         return (EINVAL);
 697 }
 698
 699 /*
 700  * Check for the presence of the IP Router Alert option [RFC2113]
 701  * in the header of an IPv4 datagram.
 702  *
 703  * This call is not intended for use from the forwarding path; it is here
 704  * so that protocol domains may check for the presence of the option.
 705  * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
 706  * option does not have much relevance to the implementation, though this
 707  * may change in future.
 708  * Router alert options SHOULD be passed if running in IPSTEALTH mode and
 709  * we are not the endpoint.
 710  * Length checks on individual options should already have been performed
 711  * by ip_dooptions() therefore they are folded under INVARIANTS here.
 712  *
 713  * Return zero if not present or options are invalid, non-zero if present.
 714  */
 715 int
 716 ip_checkrouteralert(struct mbuf *m)
 717 {
 718         struct ip *ip = mtod(m, struct ip *);
 719         u_char *cp;
 720         int opt, optlen, cnt, found_ra;
 721
 722         found_ra = 0;
 723         cp = (u_char *)(ip + 1);
 724         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 725         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 726                 opt = cp[IPOPT_OPTVAL];
 727                 if (opt == IPOPT_EOL)
 728                         break;
 729                 if (opt == IPOPT_NOP)
 730                         optlen = 1;
 731                 else {
 732 #ifdef INVARIANTS
 733                         if (cnt < IPOPT_OLEN + sizeof(*cp))
 734                                 break;
 735 #endif
 736                         optlen = cp[IPOPT_OLEN];
 737 #ifdef INVARIANTS
 738                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
 739                                 break;
 740 #endif
 741                 }
 742                 switch (opt) {
 743                 case IPOPT_RA:
 744 #ifdef INVARIANTS
 745                         if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
 746                             (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
 747                             break;
 748                         else
 749 #endif
 750                         found_ra = 1;
 751                         break;
 752                 default:
 753                         break;
 754                 }
 755         }
 756
 757         return (found_ra);
 758 }