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
  32 #include <sys/cdefs.h>
  33 __FBSDID("$FreeBSD$");
  34
  35 #include "opt_ipstealth.h"
  36
  37 #include <sys/param.h>
  38 #include <sys/systm.h>
  39 #include <sys/mbuf.h>
  40 #include <sys/domain.h>
  41 #include <sys/protosw.h>
  42 #include <sys/socket.h>
  43 #include <sys/time.h>
  44 #include <sys/kernel.h>
  45 #include <sys/syslog.h>
  46 #include <sys/sysctl.h>
  47
  48 #include <net/if.h>
  49 #include <net/if_types.h>
  50 #include <net/if_var.h>
  51 #include <net/if_dl.h>
  52 #include <net/route.h>
  53 #include <net/netisr.h>
  54 #include <net/vnet.h>
  55
  56 #include <netinet/in.h>
  57 #include <netinet/in_fib.h>
  58 #include <netinet/in_systm.h>
  59 #include <netinet/in_var.h>
  60 #include <netinet/ip.h>
  61 #include <netinet/in_pcb.h>
  62 #include <netinet/ip_var.h>
  63 #include <netinet/ip_options.h>
  64 #include <netinet/ip_icmp.h>
  65 #include <machine/in_cksum.h>
  66
  67 #include <sys/socketvar.h>
  68
  69 static VNET_DEFINE(int, ip_dosourceroute);
  70 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute,
  71     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_dosourceroute), 0,
  72     "Enable forwarding source routed IP packets");
  73 #define V_ip_dosourceroute      VNET(ip_dosourceroute)
  74
  75 static VNET_DEFINE(int, ip_acceptsourceroute);
  76 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute,
  77     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_acceptsourceroute), 0,
  78     "Enable accepting source routed IP packets");
  79 #define V_ip_acceptsourceroute  VNET(ip_acceptsourceroute)
  80
  81 VNET_DEFINE(int, ip_doopts) = 1; /* 0 = ignore, 1 = process, 2 = reject */
  82 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_VNET | CTLFLAG_RW,
  83     &VNET_NAME(ip_doopts), 0, "Enable IP options processing ([LS]SRR, RR, TS)");
  84
  85 static void     save_rte(struct mbuf *m, u_char *, struct in_addr);
  86
  87 /*
  88  * Do option processing on a datagram, possibly discarding it if bad options
  89  * are encountered, or forwarding it if source-routed.
  90  *
  91  * The pass argument is used when operating in the IPSTEALTH mode to tell
  92  * what options to process: [LS]SRR (pass 0) or the others (pass 1).  The
  93  * reason for as many as two passes is that when doing IPSTEALTH, non-routing
  94  * options should be processed only if the packet is for us.
  95  *
  96  * Returns 1 if packet has been forwarded/freed, 0 if the packet should be
  97  * processed further.
  98  */
  99 int
 100 ip_dooptions(struct mbuf *m, int pass)
 101 {
 102         struct ip *ip = mtod(m, struct ip *);
 103         u_char *cp;
 104         struct in_ifaddr *ia;
 105         int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
 106         struct in_addr *sin, dst;
 107         uint32_t ntime;
 108         struct nhop4_extended nh_ext;
 109         struct  sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
 110
 111         /* Ignore or reject packets with IP options. */
 112         if (V_ip_doopts == 0)
 113                 return 0;
 114         else if (V_ip_doopts == 2) {
 115                 type = ICMP_UNREACH;
 116                 code = ICMP_UNREACH_FILTER_PROHIB;
 117                 goto bad;
 118         }
 119
 120         dst = ip->ip_dst;
 121         cp = (u_char *)(ip + 1);
 122         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 123         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 124                 opt = cp[IPOPT_OPTVAL];
 125                 if (opt == IPOPT_EOL)
 126                         break;
 127                 if (opt == IPOPT_NOP)
 128                         optlen = 1;
 129                 else {
 130                         if (cnt < IPOPT_OLEN + sizeof(*cp)) {
 131                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 132                                 goto bad;
 133                         }
 134                         optlen = cp[IPOPT_OLEN];
 135                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
 136                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 137                                 goto bad;
 138                         }
 139                 }
 140                 switch (opt) {
 141
 142                 default:
 143                         break;
 144
 145                 /*
 146                  * Source routing with record.  Find interface with current
 147                  * destination address.  If none on this machine then drop if
 148                  * strictly routed, or do nothing if loosely routed.  Record
 149                  * interface address and bring up next address component.  If
 150                  * strictly routed make sure next address is on directly
 151                  * accessible net.
 152                  */
 153                 case IPOPT_LSRR:
 154                 case IPOPT_SSRR:
 155 #ifdef IPSTEALTH
 156                         if (V_ipstealth && pass > 0)
 157                                 break;
 158 #endif
 159                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
 160                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 161                                 goto bad;
 162                         }
 163                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
 164                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 165                                 goto bad;
 166                         }
 167                         ipaddr.sin_addr = ip->ip_dst;
 168                         if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr)
 169                             == 0) {
 170                                 if (opt == IPOPT_SSRR) {
 171                                         type = ICMP_UNREACH;
 172                                         code = ICMP_UNREACH_SRCFAIL;
 173                                         goto bad;
 174                                 }
 175                                 if (!V_ip_dosourceroute)
 176                                         goto nosourcerouting;
 177                                 /*
 178                                  * Loose routing, and not at next destination
 179                                  * yet; nothing to do except forward.
 180                                  */
 181                                 break;
 182                         }
 183                         off--;                  /* 0 origin */
 184                         if (off > optlen - (int)sizeof(struct in_addr)) {
 185                                 /*
 186                                  * End of source route.  Should be for us.
 187                                  */
 188                                 if (!V_ip_acceptsourceroute)
 189                                         goto nosourcerouting;
 190                                 save_rte(m, cp, ip->ip_src);
 191                                 break;
 192                         }
 193 #ifdef IPSTEALTH
 194                         if (V_ipstealth)
 195                                 goto dropit;
 196 #endif
 197                         if (!V_ip_dosourceroute) {
 198                                 if (V_ipforwarding) {
 199                                         char srcbuf[INET_ADDRSTRLEN];
 200                                         char dstbuf[INET_ADDRSTRLEN];
 201
 202                                         /*
 203                                          * Acting as a router, so generate
 204                                          * ICMP
 205                                          */
 206 nosourcerouting:
 207                                         log(LOG_WARNING,
 208                                             "attempted source route from %s "
 209                                             "to %s\n",
 210                                             inet_ntoa_r(ip->ip_src, srcbuf),
 211                                             inet_ntoa_r(ip->ip_dst, dstbuf));
 212                                         type = ICMP_UNREACH;
 213                                         code = ICMP_UNREACH_SRCFAIL;
 214                                         goto bad;
 215                                 } else {
 216                                         /*
 217                                          * Not acting as a router, so
 218                                          * silently drop.
 219                                          */
 220 #ifdef IPSTEALTH
 221 dropit:
 222 #endif
 223                                         IPSTAT_INC(ips_cantforward);
 224                                         m_freem(m);
 225                                         return (1);
 226                                 }
 227                         }
 228
 229                         /*
 230                          * locate outgoing interface
 231                          */
 232                         (void)memcpy(&ipaddr.sin_addr, cp + off,
 233                             sizeof(ipaddr.sin_addr));
 234
 235                         type = ICMP_UNREACH;
 236                         code = ICMP_UNREACH_SRCFAIL;
 237
 238                         if (opt == IPOPT_SSRR) {
 239 #define INA     struct in_ifaddr *
 240 #define SA      struct sockaddr *
 241                             ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr,
 242                                             RT_ALL_FIBS);
 243                             if (ia == NULL)
 244                                     ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0,
 245                                                     RT_ALL_FIBS);
 246                                 if (ia == NULL)
 247                                         goto bad;
 248
 249                                 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
 250                                     sizeof(struct in_addr));
 251                                 ifa_free(&ia->ia_ifa);
 252                         } else {
 253                                 /* XXX MRT 0 for routing */
 254                                 if (fib4_lookup_nh_ext(M_GETFIB(m),
 255                                     ipaddr.sin_addr, 0, 0, &nh_ext) != 0)
 256                                         goto bad;
 257
 258                                 memcpy(cp + off, &nh_ext.nh_src,
 259                                     sizeof(struct in_addr));
 260                         }
 261
 262                         ip->ip_dst = ipaddr.sin_addr;
 263                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 264                         /*
 265                          * Let ip_intr's mcast routing check handle mcast pkts
 266                          */
 267                         forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
 268                         break;
 269
 270                 case IPOPT_RR:
 271 #ifdef IPSTEALTH
 272                         if (V_ipstealth && pass == 0)
 273                                 break;
 274 #endif
 275                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
 276                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 277                                 goto bad;
 278                         }
 279                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
 280                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 281                                 goto bad;
 282                         }
 283                         /*
 284                          * If no space remains, ignore.
 285                          */
 286                         off--;                  /* 0 origin */
 287                         if (off > optlen - (int)sizeof(struct in_addr))
 288                                 break;
 289                         (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
 290                             sizeof(ipaddr.sin_addr));
 291                         /*
 292                          * Locate outgoing interface; if we're the
 293                          * destination, use the incoming interface (should be
 294                          * same).
 295                          */
 296                         if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) != NULL) {
 297                                 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
 298                                     sizeof(struct in_addr));
 299                                 ifa_free(&ia->ia_ifa);
 300                         } else if (fib4_lookup_nh_ext(M_GETFIB(m),
 301                             ipaddr.sin_addr, 0, 0, &nh_ext) == 0) {
 302                                 memcpy(cp + off, &nh_ext.nh_src,
 303                                     sizeof(struct in_addr));
 304                         } else {
 305                                 type = ICMP_UNREACH;
 306                                 code = ICMP_UNREACH_HOST;
 307                                 goto bad;
 308                         }
 309                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 310                         break;
 311
 312                 case IPOPT_TS:
 313 #ifdef IPSTEALTH
 314                         if (V_ipstealth && pass == 0)
 315                                 break;
 316 #endif
 317                         code = cp - (u_char *)ip;
 318                         if (optlen < 4 || optlen > 40) {
 319                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 320                                 goto bad;
 321                         }
 322                         if ((off = cp[IPOPT_OFFSET]) < 5) {
 323                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 324                                 goto bad;
 325                         }
 326                         if (off > optlen - (int)sizeof(int32_t)) {
 327                                 cp[IPOPT_OFFSET + 1] += (1 << 4);
 328                                 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
 329                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 330                                         goto bad;
 331                                 }
 332                                 break;
 333                         }
 334                         off--;                          /* 0 origin */
 335                         sin = (struct in_addr *)(cp + off);
 336                         switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
 337
 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                                 ifa_free(&ia->ia_ifa);
 355                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 356                                 off += sizeof(struct in_addr);
 357                                 break;
 358
 359                         case IPOPT_TS_PRESPEC:
 360                                 if (off + sizeof(uint32_t) +
 361                                     sizeof(struct in_addr) > optlen) {
 362                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 363                                         goto bad;
 364                                 }
 365                                 (void)memcpy(&ipaddr.sin_addr, sin,
 366                                     sizeof(struct in_addr));
 367                                 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0)
 368                                         continue;
 369                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 370                                 off += sizeof(struct in_addr);
 371                                 break;
 372
 373                         default:
 374                                 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
 375                                 goto bad;
 376                         }
 377                         ntime = iptime();
 378                         (void)memcpy(cp + off, &ntime, sizeof(uint32_t));
 379                         cp[IPOPT_OFFSET] += sizeof(uint32_t);
 380                 }
 381         }
 382         if (forward && V_ipforwarding) {
 383                 ip_forward(m, 1);
 384                 return (1);
 385         }
 386         return (0);
 387 bad:
 388         icmp_error(m, type, code, 0, 0);
 389         IPSTAT_INC(ips_badoptions);
 390         return (1);
 391 }
 392
 393 /*
 394  * Save incoming source route for use in replies, to be picked up later by
 395  * ip_srcroute if the receiver is interested.
 396  */
 397 static void
 398 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
 399 {
 400         unsigned olen;
 401         struct ipopt_tag *opts;
 402
 403         opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
 404             sizeof(struct ipopt_tag), M_NOWAIT);
 405         if (opts == NULL)
 406                 return;
 407
 408         olen = option[IPOPT_OLEN];
 409         if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
 410                 m_tag_free((struct m_tag *)opts);
 411                 return;
 412         }
 413         bcopy(option, opts->ip_srcrt.srcopt, olen);
 414         opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
 415         opts->ip_srcrt.dst = dst;
 416         m_tag_prepend(m, (struct m_tag *)opts);
 417 }
 418
 419 /*
 420  * Retrieve incoming source route for use in replies, in the same form used
 421  * by setsockopt.  The first hop is placed before the options, will be
 422  * removed later.
 423  */
 424 struct mbuf *
 425 ip_srcroute(struct mbuf *m0)
 426 {
 427         struct in_addr *p, *q;
 428         struct mbuf *m;
 429         struct ipopt_tag *opts;
 430
 431         opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
 432         if (opts == NULL)
 433                 return (NULL);
 434
 435         if (opts->ip_nhops == 0)
 436                 return (NULL);
 437         m = m_get(M_NOWAIT, MT_DATA);
 438         if (m == NULL)
 439                 return (NULL);
 440
 441 #define OPTSIZ  (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
 442
 443         /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
 444         m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
 445             sizeof(struct in_addr) + OPTSIZ;
 446
 447         /*
 448          * First, save first hop for return route.
 449          */
 450         p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
 451         *(mtod(m, struct in_addr *)) = *p--;
 452
 453         /*
 454          * Copy option fields and padding (nop) to mbuf.
 455          */
 456         opts->ip_srcrt.nop = IPOPT_NOP;
 457         opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
 458         (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
 459             &(opts->ip_srcrt.nop), OPTSIZ);
 460         q = (struct in_addr *)(mtod(m, caddr_t) +
 461             sizeof(struct in_addr) + OPTSIZ);
 462 #undef OPTSIZ
 463         /*
 464          * Record return path as an IP source route, reversing the path
 465          * (pointers are now aligned).
 466          */
 467         while (p >= opts->ip_srcrt.route) {
 468                 *q++ = *p--;
 469         }
 470         /*
 471          * Last hop goes to final destination.
 472          */
 473         *q = opts->ip_srcrt.dst;
 474         m_tag_delete(m0, (struct m_tag *)opts);
 475         return (m);
 476 }
 477
 478 /*
 479  * Strip out IP options, at higher level protocol in the kernel.
 480  */
 481 void
 482 ip_stripoptions(struct mbuf *m)
 483 {
 484         struct ip *ip = mtod(m, struct ip *);
 485         int olen;
 486
 487         olen = (ip->ip_hl << 2) - sizeof(struct ip);
 488         m->m_len -= olen;
 489         if (m->m_flags & M_PKTHDR)
 490                 m->m_pkthdr.len -= olen;
 491         ip->ip_len = htons(ntohs(ip->ip_len) - olen);
 492         ip->ip_hl = sizeof(struct ip) >> 2;
 493
 494         bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1),
 495             (size_t )(m->m_len - sizeof(struct ip)));
 496 }
 497
 498 /*
 499  * Insert IP options into preformed packet.  Adjust IP destination as
 500  * required for IP source routing, as indicated by a non-zero in_addr at the
 501  * start of the options.
 502  *
 503  * XXX This routine assumes that the packet has no options in place.
 504  */
 505 struct mbuf *
 506 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
 507 {
 508         struct ipoption *p = mtod(opt, struct ipoption *);
 509         struct mbuf *n;
 510         struct ip *ip = mtod(m, struct ip *);
 511         unsigned optlen;
 512
 513         optlen = opt->m_len - sizeof(p->ipopt_dst);
 514         if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) {
 515                 *phlen = 0;
 516                 return (m);             /* XXX should fail */
 517         }
 518         if (p->ipopt_dst.s_addr)
 519                 ip->ip_dst = p->ipopt_dst;
 520         if (!M_WRITABLE(m) || M_LEADINGSPACE(m) < optlen) {
 521                 n = m_gethdr(M_NOWAIT, MT_DATA);
 522                 if (n == NULL) {
 523                         *phlen = 0;
 524                         return (m);
 525                 }
 526                 m_move_pkthdr(n, m);
 527                 n->m_pkthdr.rcvif = NULL;
 528                 n->m_pkthdr.len += optlen;
 529                 m->m_len -= sizeof(struct ip);
 530                 m->m_data += sizeof(struct ip);
 531                 n->m_next = m;
 532                 m = n;
 533                 m->m_len = optlen + sizeof(struct ip);
 534                 m->m_data += max_linkhdr;
 535                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 536         } else {
 537                 m->m_data -= optlen;
 538                 m->m_len += optlen;
 539                 m->m_pkthdr.len += optlen;
 540                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 541         }
 542         ip = mtod(m, struct ip *);
 543         bcopy(p->ipopt_list, ip + 1, optlen);
 544         *phlen = sizeof(struct ip) + optlen;
 545         ip->ip_v = IPVERSION;
 546         ip->ip_hl = *phlen >> 2;
 547         ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
 548         return (m);
 549 }
 550
 551 /*
 552  * Copy options from ip to jp, omitting those not copied during
 553  * fragmentation.
 554  */
 555 int
 556 ip_optcopy(struct ip *ip, struct ip *jp)
 557 {
 558         u_char *cp, *dp;
 559         int opt, optlen, cnt;
 560
 561         cp = (u_char *)(ip + 1);
 562         dp = (u_char *)(jp + 1);
 563         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 564         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 565                 opt = cp[0];
 566                 if (opt == IPOPT_EOL)
 567                         break;
 568                 if (opt == IPOPT_NOP) {
 569                         /* Preserve for IP mcast tunnel's LSRR alignment. */
 570                         *dp++ = IPOPT_NOP;
 571                         optlen = 1;
 572                         continue;
 573                 }
 574
 575                 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
 576                     ("ip_optcopy: malformed ipv4 option"));
 577                 optlen = cp[IPOPT_OLEN];
 578                 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
 579                     ("ip_optcopy: malformed ipv4 option"));
 580
 581                 /* Bogus lengths should have been caught by ip_dooptions. */
 582                 if (optlen > cnt)
 583                         optlen = cnt;
 584                 if (IPOPT_COPIED(opt)) {
 585                         bcopy(cp, dp, optlen);
 586                         dp += optlen;
 587                 }
 588         }
 589         for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
 590                 *dp++ = IPOPT_EOL;
 591         return (optlen);
 592 }
 593
 594 /*
 595  * Set up IP options in pcb for insertion in output packets.  Store in mbuf
 596  * with pointer in pcbopt, adding pseudo-option with destination address if
 597  * source routed.
 598  */
 599 int
 600 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
 601 {
 602         int cnt, optlen;
 603         u_char *cp;
 604         struct mbuf **pcbopt;
 605         u_char opt;
 606
 607         INP_WLOCK_ASSERT(inp);
 608
 609         pcbopt = &inp->inp_options;
 610
 611         /* turn off any old options */
 612         if (*pcbopt)
 613                 (void)m_free(*pcbopt);
 614         *pcbopt = NULL;
 615         if (m == NULL || m->m_len == 0) {
 616                 /*
 617                  * Only turning off any previous options.
 618                  */
 619                 if (m != NULL)
 620                         (void)m_free(m);
 621                 return (0);
 622         }
 623
 624         if (m->m_len % sizeof(int32_t))
 625                 goto bad;
 626         /*
 627          * IP first-hop destination address will be stored before actual
 628          * options; move other options back and clear it when none present.
 629          */
 630         if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
 631                 goto bad;
 632         cnt = m->m_len;
 633         m->m_len += sizeof(struct in_addr);
 634         cp = mtod(m, u_char *) + sizeof(struct in_addr);
 635         bcopy(mtod(m, void *), cp, (unsigned)cnt);
 636         bzero(mtod(m, void *), sizeof(struct in_addr));
 637
 638         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 639                 opt = cp[IPOPT_OPTVAL];
 640                 if (opt == IPOPT_EOL)
 641                         break;
 642                 if (opt == IPOPT_NOP)
 643                         optlen = 1;
 644                 else {
 645                         if (cnt < IPOPT_OLEN + sizeof(*cp))
 646                                 goto bad;
 647                         optlen = cp[IPOPT_OLEN];
 648                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
 649                                 goto bad;
 650                 }
 651                 switch (opt) {
 652
 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
 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 }