sys/netinet/ip_options.c

   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  * $FreeBSD$
  32  */
  33
  34 #include "opt_ipstealth.h"
  35 #include "opt_mac.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
  55 #include <netinet/in.h>
  56 #include <netinet/in_systm.h>
  57 #include <netinet/in_var.h>
  58 #include <netinet/ip.h>
  59 #include <netinet/in_pcb.h>
  60 #include <netinet/ip_var.h>
  61 #include <netinet/ip_options.h>
  62 #include <netinet/ip_icmp.h>
  63 #include <machine/in_cksum.h>
  64
  65 #include <sys/socketvar.h>
  66
  67 #include <security/mac/mac_framework.h>
  68
  69 static int      ip_dosourceroute = 0;
  70 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute, CTLFLAG_RW,
  71     &ip_dosourceroute, 0, "Enable forwarding source routed IP packets");
  72
  73 static int      ip_acceptsourceroute = 0;
  74 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute,
  75     CTLFLAG_RW, &ip_acceptsourceroute, 0,
  76     "Enable accepting source routed IP packets");
  77
  78 int             ip_doopts = 1;  /* 0 = ignore, 1 = process, 2 = reject */
  79 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_RW,
  80     &ip_doopts, 0, "Enable IP options processing ([LS]SRR, RR, TS)");
  81
  82 static void     save_rte(struct mbuf *m, u_char *, struct in_addr);
  83
  84 /*
  85  * Do option processing on a datagram, possibly discarding it if bad options
  86  * are encountered, or forwarding it if source-routed.
  87  *
  88  * The pass argument is used when operating in the IPSTEALTH mode to tell
  89  * what options to process: [LS]SRR (pass 0) or the others (pass 1).  The
  90  * reason for as many as two passes is that when doing IPSTEALTH, non-routing
  91  * options should be processed only if the packet is for us.
  92  *
  93  * Returns 1 if packet has been forwarded/freed, 0 if the packet should be
  94  * processed further.
  95  */
  96 int
  97 ip_dooptions(struct mbuf *m, int pass)
  98 {
  99         struct ip *ip = mtod(m, struct ip *);
 100         u_char *cp;
 101         struct in_ifaddr *ia;
 102         int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
 103         struct in_addr *sin, dst;
 104         n_time ntime;
 105         struct  sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
 106
 107         /* Ignore or reject packets with IP options. */
 108         if (ip_doopts == 0)
 109                 return 0;
 110         else if (ip_doopts == 2) {
 111                 type = ICMP_UNREACH;
 112                 code = ICMP_UNREACH_FILTER_PROHIB;
 113                 goto bad;
 114         }
 115
 116         dst = ip->ip_dst;
 117         cp = (u_char *)(ip + 1);
 118         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 119         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 120                 opt = cp[IPOPT_OPTVAL];
 121                 if (opt == IPOPT_EOL)
 122                         break;
 123                 if (opt == IPOPT_NOP)
 124                         optlen = 1;
 125                 else {
 126                         if (cnt < IPOPT_OLEN + sizeof(*cp)) {
 127                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 128                                 goto bad;
 129                         }
 130                         optlen = cp[IPOPT_OLEN];
 131                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
 132                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 133                                 goto bad;
 134                         }
 135                 }
 136                 switch (opt) {
 137
 138                 default:
 139                         break;
 140
 141                 /*
 142                  * Source routing with record.  Find interface with current
 143                  * destination address.  If none on this machine then drop if
 144                  * strictly routed, or do nothing if loosely routed.  Record
 145                  * interface address and bring up next address component.  If
 146                  * strictly routed make sure next address is on directly
 147                  * accessible net.
 148                  */
 149                 case IPOPT_LSRR:
 150                 case IPOPT_SSRR:
 151 #ifdef IPSTEALTH
 152                         if (ipstealth && pass > 0)
 153                                 break;
 154 #endif
 155                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
 156                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 157                                 goto bad;
 158                         }
 159                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
 160                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 161                                 goto bad;
 162                         }
 163                         ipaddr.sin_addr = ip->ip_dst;
 164                         ia = (struct in_ifaddr *)
 165                                 ifa_ifwithaddr((struct sockaddr *)&ipaddr);
 166                         if (ia == NULL) {
 167                                 if (opt == IPOPT_SSRR) {
 168                                         type = ICMP_UNREACH;
 169                                         code = ICMP_UNREACH_SRCFAIL;
 170                                         goto bad;
 171                                 }
 172                                 if (!ip_dosourceroute)
 173                                         goto nosourcerouting;
 174                                 /*
 175                                  * Loose routing, and not at next destination
 176                                  * yet; nothing to do except forward.
 177                                  */
 178                                 break;
 179                         }
 180                         off--;                  /* 0 origin */
 181                         if (off > optlen - (int)sizeof(struct in_addr)) {
 182                                 /*
 183                                  * End of source route.  Should be for us.
 184                                  */
 185                                 if (!ip_acceptsourceroute)
 186                                         goto nosourcerouting;
 187                                 save_rte(m, cp, ip->ip_src);
 188                                 break;
 189                         }
 190 #ifdef IPSTEALTH
 191                         if (ipstealth)
 192                                 goto dropit;
 193 #endif
 194                         if (!ip_dosourceroute) {
 195                                 if (ipforwarding) {
 196                                         char buf[16]; /* aaa.bbb.ccc.ddd\0 */
 197                                         /*
 198                                          * Acting as a router, so generate
 199                                          * ICMP
 200                                          */
 201 nosourcerouting:
 202                                         strcpy(buf, inet_ntoa(ip->ip_dst));
 203                                         log(LOG_WARNING,
 204                                             "attempted source route from %s to %s\n",
 205                                             inet_ntoa(ip->ip_src), buf);
 206                                         type = ICMP_UNREACH;
 207                                         code = ICMP_UNREACH_SRCFAIL;
 208                                         goto bad;
 209                                 } else {
 210                                         /*
 211                                          * Not acting as a router, so
 212                                          * silently drop.
 213                                          */
 214 #ifdef IPSTEALTH
 215 dropit:
 216 #endif
 217                                         ipstat.ips_cantforward++;
 218                                         m_freem(m);
 219                                         return (1);
 220                                 }
 221                         }
 222
 223                         /*
 224                          * locate outgoing interface
 225                          */
 226                         (void)memcpy(&ipaddr.sin_addr, cp + off,
 227                             sizeof(ipaddr.sin_addr));
 228
 229                         if (opt == IPOPT_SSRR) {
 230 #define INA     struct in_ifaddr *
 231 #define SA      struct sockaddr *
 232                             if ((ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr)) == NULL)
 233                                 ia = (INA)ifa_ifwithnet((SA)&ipaddr);
 234                         } else
 235                                 ia = ip_rtaddr(ipaddr.sin_addr);
 236                         if (ia == NULL) {
 237                                 type = ICMP_UNREACH;
 238                                 code = ICMP_UNREACH_SRCFAIL;
 239                                 goto bad;
 240                         }
 241                         ip->ip_dst = ipaddr.sin_addr;
 242                         (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
 243                             sizeof(struct in_addr));
 244                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 245                         /*
 246                          * Let ip_intr's mcast routing check handle mcast pkts
 247                          */
 248                         forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
 249                         break;
 250
 251                 case IPOPT_RR:
 252 #ifdef IPSTEALTH
 253                         if (ipstealth && pass == 0)
 254                                 break;
 255 #endif
 256                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
 257                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 258                                 goto bad;
 259                         }
 260                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
 261                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 262                                 goto bad;
 263                         }
 264                         /*
 265                          * If no space remains, ignore.
 266                          */
 267                         off--;                  /* 0 origin */
 268                         if (off > optlen - (int)sizeof(struct in_addr))
 269                                 break;
 270                         (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
 271                             sizeof(ipaddr.sin_addr));
 272                         /*
 273                          * Locate outgoing interface; if we're the
 274                          * destination, use the incoming interface (should be
 275                          * same).
 276                          */
 277                         if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) == NULL &&
 278                             (ia = ip_rtaddr(ipaddr.sin_addr)) == NULL) {
 279                                 type = ICMP_UNREACH;
 280                                 code = ICMP_UNREACH_HOST;
 281                                 goto bad;
 282                         }
 283                         (void)memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
 284                             sizeof(struct in_addr));
 285                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 286                         break;
 287
 288                 case IPOPT_TS:
 289 #ifdef IPSTEALTH
 290                         if (ipstealth && pass == 0)
 291                                 break;
 292 #endif
 293                         code = cp - (u_char *)ip;
 294                         if (optlen < 4 || optlen > 40) {
 295                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 296                                 goto bad;
 297                         }
 298                         if ((off = cp[IPOPT_OFFSET]) < 5) {
 299                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 300                                 goto bad;
 301                         }
 302                         if (off > optlen - (int)sizeof(int32_t)) {
 303                                 cp[IPOPT_OFFSET + 1] += (1 << 4);
 304                                 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
 305                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 306                                         goto bad;
 307                                 }
 308                                 break;
 309                         }
 310                         off--;                          /* 0 origin */
 311                         sin = (struct in_addr *)(cp + off);
 312                         switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
 313
 314                         case IPOPT_TS_TSONLY:
 315                                 break;
 316
 317                         case IPOPT_TS_TSANDADDR:
 318                                 if (off + sizeof(n_time) +
 319                                     sizeof(struct in_addr) > optlen) {
 320                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 321                                         goto bad;
 322                                 }
 323                                 ipaddr.sin_addr = dst;
 324                                 ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
 325                                                             m->m_pkthdr.rcvif);
 326                                 if (ia == NULL)
 327                                         continue;
 328                                 (void)memcpy(sin, &IA_SIN(ia)->sin_addr,
 329                                     sizeof(struct in_addr));
 330                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 331                                 off += sizeof(struct in_addr);
 332                                 break;
 333
 334                         case IPOPT_TS_PRESPEC:
 335                                 if (off + sizeof(n_time) +
 336                                     sizeof(struct in_addr) > optlen) {
 337                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 338                                         goto bad;
 339                                 }
 340                                 (void)memcpy(&ipaddr.sin_addr, sin,
 341                                     sizeof(struct in_addr));
 342                                 if (ifa_ifwithaddr((SA)&ipaddr) == NULL)
 343                                         continue;
 344                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 345                                 off += sizeof(struct in_addr);
 346                                 break;
 347
 348                         default:
 349                                 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
 350                                 goto bad;
 351                         }
 352                         ntime = iptime();
 353                         (void)memcpy(cp + off, &ntime, sizeof(n_time));
 354                         cp[IPOPT_OFFSET] += sizeof(n_time);
 355                 }
 356         }
 357         if (forward && ipforwarding) {
 358                 ip_forward(m, 1);
 359                 return (1);
 360         }
 361         return (0);
 362 bad:
 363         icmp_error(m, type, code, 0, 0);
 364         ipstat.ips_badoptions++;
 365         return (1);
 366 }
 367
 368 /*
 369  * Save incoming source route for use in replies, to be picked up later by
 370  * ip_srcroute if the receiver is interested.
 371  */
 372 static void
 373 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
 374 {
 375         unsigned olen;
 376         struct ipopt_tag *opts;
 377
 378         opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
 379             sizeof(struct ipopt_tag), M_NOWAIT);
 380         if (opts == NULL)
 381                 return;
 382
 383         olen = option[IPOPT_OLEN];
 384         if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
 385                 m_tag_free((struct m_tag *)opts);
 386                 return;
 387         }
 388         bcopy(option, opts->ip_srcrt.srcopt, olen);
 389         opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
 390         opts->ip_srcrt.dst = dst;
 391         m_tag_prepend(m, (struct m_tag *)opts);
 392 }
 393
 394 /*
 395  * Retrieve incoming source route for use in replies, in the same form used
 396  * by setsockopt.  The first hop is placed before the options, will be
 397  * removed later.
 398  */
 399 struct mbuf *
 400 ip_srcroute(struct mbuf *m0)
 401 {
 402         struct in_addr *p, *q;
 403         struct mbuf *m;
 404         struct ipopt_tag *opts;
 405
 406         opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
 407         if (opts == NULL)
 408                 return (NULL);
 409
 410         if (opts->ip_nhops == 0)
 411                 return (NULL);
 412         m = m_get(M_DONTWAIT, MT_DATA);
 413         if (m == NULL)
 414                 return (NULL);
 415
 416 #define OPTSIZ  (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
 417
 418         /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
 419         m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
 420             sizeof(struct in_addr) + OPTSIZ;
 421
 422         /*
 423          * First, save first hop for return route.
 424          */
 425         p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
 426         *(mtod(m, struct in_addr *)) = *p--;
 427
 428         /*
 429          * Copy option fields and padding (nop) to mbuf.
 430          */
 431         opts->ip_srcrt.nop = IPOPT_NOP;
 432         opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
 433         (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
 434             &(opts->ip_srcrt.nop), OPTSIZ);
 435         q = (struct in_addr *)(mtod(m, caddr_t) +
 436             sizeof(struct in_addr) + OPTSIZ);
 437 #undef OPTSIZ
 438         /*
 439          * Record return path as an IP source route, reversing the path
 440          * (pointers are now aligned).
 441          */
 442         while (p >= opts->ip_srcrt.route) {
 443                 *q++ = *p--;
 444         }
 445         /*
 446          * Last hop goes to final destination.
 447          */
 448         *q = opts->ip_srcrt.dst;
 449         m_tag_delete(m0, (struct m_tag *)opts);
 450         return (m);
 451 }
 452
 453 /*
 454  * Strip out IP options, at higher level protocol in the kernel.  Second
 455  * argument is buffer to which options will be moved, and return value is
 456  * their length.
 457  *
 458  * XXX should be deleted; last arg currently ignored.
 459  */
 460 void
 461 ip_stripoptions(struct mbuf *m, struct mbuf *mopt)
 462 {
 463         int i;
 464         struct ip *ip = mtod(m, struct ip *);
 465         caddr_t opts;
 466         int olen;
 467
 468         olen = (ip->ip_hl << 2) - sizeof (struct ip);
 469         opts = (caddr_t)(ip + 1);
 470         i = m->m_len - (sizeof (struct ip) + olen);
 471         bcopy(opts + olen, opts, (unsigned)i);
 472         m->m_len -= olen;
 473         if (m->m_flags & M_PKTHDR)
 474                 m->m_pkthdr.len -= olen;
 475         ip->ip_v = IPVERSION;
 476         ip->ip_hl = sizeof(struct ip) >> 2;
 477 }
 478
 479 /*
 480  * Insert IP options into preformed packet.  Adjust IP destination as
 481  * required for IP source routing, as indicated by a non-zero in_addr at the
 482  * start of the options.
 483  *
 484  * XXX This routine assumes that the packet has no options in place.
 485  */
 486 struct mbuf *
 487 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
 488 {
 489         struct ipoption *p = mtod(opt, struct ipoption *);
 490         struct mbuf *n;
 491         struct ip *ip = mtod(m, struct ip *);
 492         unsigned optlen;
 493
 494         optlen = opt->m_len - sizeof(p->ipopt_dst);
 495         if (optlen + ip->ip_len > IP_MAXPACKET) {
 496                 *phlen = 0;
 497                 return (m);             /* XXX should fail */
 498         }
 499         if (p->ipopt_dst.s_addr)
 500                 ip->ip_dst = p->ipopt_dst;
 501         if (m->m_flags & M_EXT || m->m_data - optlen < m->m_pktdat) {
 502                 MGETHDR(n, M_DONTWAIT, MT_DATA);
 503                 if (n == NULL) {
 504                         *phlen = 0;
 505                         return (m);
 506                 }
 507                 M_MOVE_PKTHDR(n, m);
 508                 n->m_pkthdr.rcvif = NULL;
 509 #ifdef MAC
 510                 mac_copy_mbuf(m, n);
 511 #endif
 512                 n->m_pkthdr.len += optlen;
 513                 m->m_len -= sizeof(struct ip);
 514                 m->m_data += sizeof(struct ip);
 515                 n->m_next = m;
 516                 m = n;
 517                 m->m_len = optlen + sizeof(struct ip);
 518                 m->m_data += max_linkhdr;
 519                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 520         } else {
 521                 m->m_data -= optlen;
 522                 m->m_len += optlen;
 523                 m->m_pkthdr.len += optlen;
 524                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 525         }
 526         ip = mtod(m, struct ip *);
 527         bcopy(p->ipopt_list, ip + 1, optlen);
 528         *phlen = sizeof(struct ip) + optlen;
 529         ip->ip_v = IPVERSION;
 530         ip->ip_hl = *phlen >> 2;
 531         ip->ip_len += optlen;
 532         return (m);
 533 }
 534
 535 /*
 536  * Copy options from ip to jp, omitting those not copied during
 537  * fragmentation.
 538  */
 539 int
 540 ip_optcopy(struct ip *ip, struct ip *jp)
 541 {
 542         u_char *cp, *dp;
 543         int opt, optlen, cnt;
 544
 545         cp = (u_char *)(ip + 1);
 546         dp = (u_char *)(jp + 1);
 547         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 548         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 549                 opt = cp[0];
 550                 if (opt == IPOPT_EOL)
 551                         break;
 552                 if (opt == IPOPT_NOP) {
 553                         /* Preserve for IP mcast tunnel's LSRR alignment. */
 554                         *dp++ = IPOPT_NOP;
 555                         optlen = 1;
 556                         continue;
 557                 }
 558
 559                 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
 560                     ("ip_optcopy: malformed ipv4 option"));
 561                 optlen = cp[IPOPT_OLEN];
 562                 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
 563                     ("ip_optcopy: malformed ipv4 option"));
 564
 565                 /* Bogus lengths should have been caught by ip_dooptions. */
 566                 if (optlen > cnt)
 567                         optlen = cnt;
 568                 if (IPOPT_COPIED(opt)) {
 569                         bcopy(cp, dp, optlen);
 570                         dp += optlen;
 571                 }
 572         }
 573         for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
 574                 *dp++ = IPOPT_EOL;
 575         return (optlen);
 576 }
 577
 578 /*
 579  * Set up IP options in pcb for insertion in output packets.  Store in mbuf
 580  * with pointer in pcbopt, adding pseudo-option with destination address if
 581  * source routed.
 582  */
 583 int
 584 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
 585 {
 586         int cnt, optlen;
 587         u_char *cp;
 588         struct mbuf **pcbopt;
 589         u_char opt;
 590
 591         INP_LOCK_ASSERT(inp);
 592
 593         pcbopt = &inp->inp_options;
 594
 595         /* turn off any old options */
 596         if (*pcbopt)
 597                 (void)m_free(*pcbopt);
 598         *pcbopt = 0;
 599         if (m == NULL || m->m_len == 0) {
 600                 /*
 601                  * Only turning off any previous options.
 602                  */
 603                 if (m != NULL)
 604                         (void)m_free(m);
 605                 return (0);
 606         }
 607
 608         if (m->m_len % sizeof(int32_t))
 609                 goto bad;
 610         /*
 611          * IP first-hop destination address will be stored before actual
 612          * options; move other options back and clear it when none present.
 613          */
 614         if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
 615                 goto bad;
 616         cnt = m->m_len;
 617         m->m_len += sizeof(struct in_addr);
 618         cp = mtod(m, u_char *) + sizeof(struct in_addr);
 619         bcopy(mtod(m, void *), cp, (unsigned)cnt);
 620         bzero(mtod(m, void *), sizeof(struct in_addr));
 621
 622         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 623                 opt = cp[IPOPT_OPTVAL];
 624                 if (opt == IPOPT_EOL)
 625                         break;
 626                 if (opt == IPOPT_NOP)
 627                         optlen = 1;
 628                 else {
 629                         if (cnt < IPOPT_OLEN + sizeof(*cp))
 630                                 goto bad;
 631                         optlen = cp[IPOPT_OLEN];
 632                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
 633                                 goto bad;
 634                 }
 635                 switch (opt) {
 636
 637                 default:
 638                         break;
 639
 640                 case IPOPT_LSRR:
 641                 case IPOPT_SSRR:
 642                         /*
 643                          * User process specifies route as:
 644                          *
 645                          *      ->A->B->C->D
 646                          *
 647                          * D must be our final destination (but we can't
 648                          * check that since we may not have connected yet).
 649                          * A is first hop destination, which doesn't appear
 650                          * in actual IP option, but is stored before the
 651                          * options.
 652                          */
 653                         if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
 654                                 goto bad;
 655                         m->m_len -= sizeof(struct in_addr);
 656                         cnt -= sizeof(struct in_addr);
 657                         optlen -= sizeof(struct in_addr);
 658                         cp[IPOPT_OLEN] = optlen;
 659                         /*
 660                          * Move first hop before start of options.
 661                          */
 662                         bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
 663                             sizeof(struct in_addr));
 664                         /*
 665                          * Then copy rest of options back
 666                          * to close up the deleted entry.
 667                          */
 668                         bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
 669                             &cp[IPOPT_OFFSET+1],
 670                             (unsigned)cnt - (IPOPT_MINOFF - 1));
 671                         break;
 672                 }
 673         }
 674         if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
 675                 goto bad;
 676         *pcbopt = m;
 677         return (0);
 678
 679 bad:
 680         (void)m_free(m);
 681         return (EINVAL);
 682 }