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 buf[16]; /* aaa.bbb.ccc.ddd\0 */
 200                                         /*
 201                                          * Acting as a router, so generate
 202                                          * ICMP
 203                                          */
 204 nosourcerouting:
 205                                         strcpy(buf, inet_ntoa(ip->ip_dst));
 206                                         log(LOG_WARNING,
 207                                             "attempted source route from %s to %s\n",
 208                                             inet_ntoa(ip->ip_src), buf);
 209                                         type = ICMP_UNREACH;
 210                                         code = ICMP_UNREACH_SRCFAIL;
 211                                         goto bad;
 212                                 } else {
 213                                         /*
 214                                          * Not acting as a router, so
 215                                          * silently drop.
 216                                          */
 217 #ifdef IPSTEALTH
 218 dropit:
 219 #endif
 220                                         IPSTAT_INC(ips_cantforward);
 221                                         m_freem(m);
 222                                         return (1);
 223                                 }
 224                         }
 225
 226                         /*
 227                          * locate outgoing interface
 228                          */
 229                         (void)memcpy(&ipaddr.sin_addr, cp + off,
 230                             sizeof(ipaddr.sin_addr));
 231
 232                         type = ICMP_UNREACH;
 233                         code = ICMP_UNREACH_SRCFAIL;
 234
 235                         if (opt == IPOPT_SSRR) {
 236 #define INA     struct in_ifaddr *
 237 #define SA      struct sockaddr *
 238                             ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr,
 239                                             RT_ALL_FIBS);
 240                             if (ia == NULL)
 241                                     ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0,
 242                                                     RT_ALL_FIBS);
 243                                 if (ia == NULL)
 244                                         goto bad;
 245
 246                                 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
 247                                     sizeof(struct in_addr));
 248                                 ifa_free(&ia->ia_ifa);
 249                         } else {
 250                                 /* XXX MRT 0 for routing */
 251                                 if (fib4_lookup_nh_ext(M_GETFIB(m),
 252                                     ipaddr.sin_addr, 0, 0, &nh_ext) != 0)
 253                                         goto bad;
 254
 255                                 memcpy(cp + off, &nh_ext.nh_src,
 256                                     sizeof(struct in_addr));
 257                         }
 258
 259                         ip->ip_dst = ipaddr.sin_addr;
 260                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 261                         /*
 262                          * Let ip_intr's mcast routing check handle mcast pkts
 263                          */
 264                         forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
 265                         break;
 266
 267                 case IPOPT_RR:
 268 #ifdef IPSTEALTH
 269                         if (V_ipstealth && pass == 0)
 270                                 break;
 271 #endif
 272                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
 273                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 274                                 goto bad;
 275                         }
 276                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
 277                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 278                                 goto bad;
 279                         }
 280                         /*
 281                          * If no space remains, ignore.
 282                          */
 283                         off--;                  /* 0 origin */
 284                         if (off > optlen - (int)sizeof(struct in_addr))
 285                                 break;
 286                         (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
 287                             sizeof(ipaddr.sin_addr));
 288                         /*
 289                          * Locate outgoing interface; if we're the
 290                          * destination, use the incoming interface (should be
 291                          * same).
 292                          */
 293                         if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) != NULL) {
 294                                 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
 295                                     sizeof(struct in_addr));
 296                                 ifa_free(&ia->ia_ifa);
 297                         } else if (fib4_lookup_nh_ext(M_GETFIB(m),
 298                             ipaddr.sin_addr, 0, 0, &nh_ext) == 0) {
 299                                 memcpy(cp + off, &nh_ext.nh_src,
 300                                     sizeof(struct in_addr));
 301                         } else {
 302                                 type = ICMP_UNREACH;
 303                                 code = ICMP_UNREACH_HOST;
 304                                 goto bad;
 305                         }
 306                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 307                         break;
 308
 309                 case IPOPT_TS:
 310 #ifdef IPSTEALTH
 311                         if (V_ipstealth && pass == 0)
 312                                 break;
 313 #endif
 314                         code = cp - (u_char *)ip;
 315                         if (optlen < 4 || optlen > 40) {
 316                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 317                                 goto bad;
 318                         }
 319                         if ((off = cp[IPOPT_OFFSET]) < 5) {
 320                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 321                                 goto bad;
 322                         }
 323                         if (off > optlen - (int)sizeof(int32_t)) {
 324                                 cp[IPOPT_OFFSET + 1] += (1 << 4);
 325                                 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
 326                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 327                                         goto bad;
 328                                 }
 329                                 break;
 330                         }
 331                         off--;                          /* 0 origin */
 332                         sin = (struct in_addr *)(cp + off);
 333                         switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
 334
 335                         case IPOPT_TS_TSONLY:
 336                                 break;
 337
 338                         case IPOPT_TS_TSANDADDR:
 339                                 if (off + sizeof(uint32_t) +
 340                                     sizeof(struct in_addr) > optlen) {
 341                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 342                                         goto bad;
 343                                 }
 344                                 ipaddr.sin_addr = dst;
 345                                 ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
 346                                                             m->m_pkthdr.rcvif);
 347                                 if (ia == NULL)
 348                                         continue;
 349                                 (void)memcpy(sin, &IA_SIN(ia)->sin_addr,
 350                                     sizeof(struct in_addr));
 351                                 ifa_free(&ia->ia_ifa);
 352                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 353                                 off += sizeof(struct in_addr);
 354                                 break;
 355
 356                         case IPOPT_TS_PRESPEC:
 357                                 if (off + sizeof(uint32_t) +
 358                                     sizeof(struct in_addr) > optlen) {
 359                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 360                                         goto bad;
 361                                 }
 362                                 (void)memcpy(&ipaddr.sin_addr, sin,
 363                                     sizeof(struct in_addr));
 364                                 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0)
 365                                         continue;
 366                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 367                                 off += sizeof(struct in_addr);
 368                                 break;
 369
 370                         default:
 371                                 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
 372                                 goto bad;
 373                         }
 374                         ntime = iptime();
 375                         (void)memcpy(cp + off, &ntime, sizeof(uint32_t));
 376                         cp[IPOPT_OFFSET] += sizeof(uint32_t);
 377                 }
 378         }
 379         if (forward && V_ipforwarding) {
 380                 ip_forward(m, 1);
 381                 return (1);
 382         }
 383         return (0);
 384 bad:
 385         icmp_error(m, type, code, 0, 0);
 386         IPSTAT_INC(ips_badoptions);
 387         return (1);
 388 }
 389
 390 /*
 391  * Save incoming source route for use in replies, to be picked up later by
 392  * ip_srcroute if the receiver is interested.
 393  */
 394 static void
 395 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
 396 {
 397         unsigned olen;
 398         struct ipopt_tag *opts;
 399
 400         opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
 401             sizeof(struct ipopt_tag), M_NOWAIT);
 402         if (opts == NULL)
 403                 return;
 404
 405         olen = option[IPOPT_OLEN];
 406         if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
 407                 m_tag_free((struct m_tag *)opts);
 408                 return;
 409         }
 410         bcopy(option, opts->ip_srcrt.srcopt, olen);
 411         opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
 412         opts->ip_srcrt.dst = dst;
 413         m_tag_prepend(m, (struct m_tag *)opts);
 414 }
 415
 416 /*
 417  * Retrieve incoming source route for use in replies, in the same form used
 418  * by setsockopt.  The first hop is placed before the options, will be
 419  * removed later.
 420  */
 421 struct mbuf *
 422 ip_srcroute(struct mbuf *m0)
 423 {
 424         struct in_addr *p, *q;
 425         struct mbuf *m;
 426         struct ipopt_tag *opts;
 427
 428         opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
 429         if (opts == NULL)
 430                 return (NULL);
 431
 432         if (opts->ip_nhops == 0)
 433                 return (NULL);
 434         m = m_get(M_NOWAIT, MT_DATA);
 435         if (m == NULL)
 436                 return (NULL);
 437
 438 #define OPTSIZ  (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
 439
 440         /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
 441         m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
 442             sizeof(struct in_addr) + OPTSIZ;
 443
 444         /*
 445          * First, save first hop for return route.
 446          */
 447         p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
 448         *(mtod(m, struct in_addr *)) = *p--;
 449
 450         /*
 451          * Copy option fields and padding (nop) to mbuf.
 452          */
 453         opts->ip_srcrt.nop = IPOPT_NOP;
 454         opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
 455         (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
 456             &(opts->ip_srcrt.nop), OPTSIZ);
 457         q = (struct in_addr *)(mtod(m, caddr_t) +
 458             sizeof(struct in_addr) + OPTSIZ);
 459 #undef OPTSIZ
 460         /*
 461          * Record return path as an IP source route, reversing the path
 462          * (pointers are now aligned).
 463          */
 464         while (p >= opts->ip_srcrt.route) {
 465                 *q++ = *p--;
 466         }
 467         /*
 468          * Last hop goes to final destination.
 469          */
 470         *q = opts->ip_srcrt.dst;
 471         m_tag_delete(m0, (struct m_tag *)opts);
 472         return (m);
 473 }
 474
 475 /*
 476  * Strip out IP options, at higher level protocol in the kernel.
 477  */
 478 void
 479 ip_stripoptions(struct mbuf *m)
 480 {
 481         struct ip *ip = mtod(m, struct ip *);
 482         int olen;
 483
 484         olen = (ip->ip_hl << 2) - sizeof(struct ip);
 485         m->m_len -= olen;
 486         if (m->m_flags & M_PKTHDR)
 487                 m->m_pkthdr.len -= olen;
 488         ip->ip_len = htons(ntohs(ip->ip_len) - olen);
 489         ip->ip_hl = sizeof(struct ip) >> 2;
 490
 491         bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1),
 492             (size_t )(m->m_len - sizeof(struct ip)));
 493 }
 494
 495 /*
 496  * Insert IP options into preformed packet.  Adjust IP destination as
 497  * required for IP source routing, as indicated by a non-zero in_addr at the
 498  * start of the options.
 499  *
 500  * XXX This routine assumes that the packet has no options in place.
 501  */
 502 struct mbuf *
 503 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
 504 {
 505         struct ipoption *p = mtod(opt, struct ipoption *);
 506         struct mbuf *n;
 507         struct ip *ip = mtod(m, struct ip *);
 508         unsigned optlen;
 509
 510         optlen = opt->m_len - sizeof(p->ipopt_dst);
 511         if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) {
 512                 *phlen = 0;
 513                 return (m);             /* XXX should fail */
 514         }
 515         if (p->ipopt_dst.s_addr)
 516                 ip->ip_dst = p->ipopt_dst;
 517         if (!M_WRITABLE(m) || M_LEADINGSPACE(m) < optlen) {
 518                 n = m_gethdr(M_NOWAIT, MT_DATA);
 519                 if (n == NULL) {
 520                         *phlen = 0;
 521                         return (m);
 522                 }
 523                 m_move_pkthdr(n, m);
 524                 n->m_pkthdr.rcvif = NULL;
 525                 n->m_pkthdr.len += optlen;
 526                 m->m_len -= sizeof(struct ip);
 527                 m->m_data += sizeof(struct ip);
 528                 n->m_next = m;
 529                 m = n;
 530                 m->m_len = optlen + sizeof(struct ip);
 531                 m->m_data += max_linkhdr;
 532                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 533         } else {
 534                 m->m_data -= optlen;
 535                 m->m_len += optlen;
 536                 m->m_pkthdr.len += optlen;
 537                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 538         }
 539         ip = mtod(m, struct ip *);
 540         bcopy(p->ipopt_list, ip + 1, optlen);
 541         *phlen = sizeof(struct ip) + optlen;
 542         ip->ip_v = IPVERSION;
 543         ip->ip_hl = *phlen >> 2;
 544         ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
 545         return (m);
 546 }
 547
 548 /*
 549  * Copy options from ip to jp, omitting those not copied during
 550  * fragmentation.
 551  */
 552 int
 553 ip_optcopy(struct ip *ip, struct ip *jp)
 554 {
 555         u_char *cp, *dp;
 556         int opt, optlen, cnt;
 557
 558         cp = (u_char *)(ip + 1);
 559         dp = (u_char *)(jp + 1);
 560         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 561         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 562                 opt = cp[0];
 563                 if (opt == IPOPT_EOL)
 564                         break;
 565                 if (opt == IPOPT_NOP) {
 566                         /* Preserve for IP mcast tunnel's LSRR alignment. */
 567                         *dp++ = IPOPT_NOP;
 568                         optlen = 1;
 569                         continue;
 570                 }
 571
 572                 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
 573                     ("ip_optcopy: malformed ipv4 option"));
 574                 optlen = cp[IPOPT_OLEN];
 575                 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
 576                     ("ip_optcopy: malformed ipv4 option"));
 577
 578                 /* Bogus lengths should have been caught by ip_dooptions. */
 579                 if (optlen > cnt)
 580                         optlen = cnt;
 581                 if (IPOPT_COPIED(opt)) {
 582                         bcopy(cp, dp, optlen);
 583                         dp += optlen;
 584                 }
 585         }
 586         for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
 587                 *dp++ = IPOPT_EOL;
 588         return (optlen);
 589 }
 590
 591 /*
 592  * Set up IP options in pcb for insertion in output packets.  Store in mbuf
 593  * with pointer in pcbopt, adding pseudo-option with destination address if
 594  * source routed.
 595  */
 596 int
 597 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
 598 {
 599         int cnt, optlen;
 600         u_char *cp;
 601         struct mbuf **pcbopt;
 602         u_char opt;
 603
 604         INP_WLOCK_ASSERT(inp);
 605
 606         pcbopt = &inp->inp_options;
 607
 608         /* turn off any old options */
 609         if (*pcbopt)
 610                 (void)m_free(*pcbopt);
 611         *pcbopt = NULL;
 612         if (m == NULL || m->m_len == 0) {
 613                 /*
 614                  * Only turning off any previous options.
 615                  */
 616                 if (m != NULL)
 617                         (void)m_free(m);
 618                 return (0);
 619         }
 620
 621         if (m->m_len % sizeof(int32_t))
 622                 goto bad;
 623         /*
 624          * IP first-hop destination address will be stored before actual
 625          * options; move other options back and clear it when none present.
 626          */
 627         if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
 628                 goto bad;
 629         cnt = m->m_len;
 630         m->m_len += sizeof(struct in_addr);
 631         cp = mtod(m, u_char *) + sizeof(struct in_addr);
 632         bcopy(mtod(m, void *), cp, (unsigned)cnt);
 633         bzero(mtod(m, void *), sizeof(struct in_addr));
 634
 635         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 636                 opt = cp[IPOPT_OPTVAL];
 637                 if (opt == IPOPT_EOL)
 638                         break;
 639                 if (opt == IPOPT_NOP)
 640                         optlen = 1;
 641                 else {
 642                         if (cnt < IPOPT_OLEN + sizeof(*cp))
 643                                 goto bad;
 644                         optlen = cp[IPOPT_OLEN];
 645                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
 646                                 goto bad;
 647                 }
 648                 switch (opt) {
 649
 650                 default:
 651                         break;
 652
 653                 case IPOPT_LSRR:
 654                 case IPOPT_SSRR:
 655                         /*
 656                          * User process specifies route as:
 657                          *
 658                          *      ->A->B->C->D
 659                          *
 660                          * D must be our final destination (but we can't
 661                          * check that since we may not have connected yet).
 662                          * A is first hop destination, which doesn't appear
 663                          * in actual IP option, but is stored before the
 664                          * options.
 665                          */
 666                         /* XXX-BZ PRIV_NETINET_SETHDROPTS? */
 667                         if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
 668                                 goto bad;
 669                         m->m_len -= sizeof(struct in_addr);
 670                         cnt -= sizeof(struct in_addr);
 671                         optlen -= sizeof(struct in_addr);
 672                         cp[IPOPT_OLEN] = optlen;
 673                         /*
 674                          * Move first hop before start of options.
 675                          */
 676                         bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
 677                             sizeof(struct in_addr));
 678                         /*
 679                          * Then copy rest of options back
 680                          * to close up the deleted entry.
 681                          */
 682                         bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
 683                             &cp[IPOPT_OFFSET+1],
 684                             (unsigned)cnt - (IPOPT_MINOFF - 1));
 685                         break;
 686                 }
 687         }
 688         if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
 689                 goto bad;
 690         *pcbopt = m;
 691         return (0);
 692
 693 bad:
 694         (void)m_free(m);
 695         return (EINVAL);
 696 }
 697
 698 /*
 699  * Check for the presence of the IP Router Alert option [RFC2113]
 700  * in the header of an IPv4 datagram.
 701  *
 702  * This call is not intended for use from the forwarding path; it is here
 703  * so that protocol domains may check for the presence of the option.
 704  * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
 705  * option does not have much relevance to the implementation, though this
 706  * may change in future.
 707  * Router alert options SHOULD be passed if running in IPSTEALTH mode and
 708  * we are not the endpoint.
 709  * Length checks on individual options should already have been performed
 710  * by ip_dooptions() therefore they are folded under INVARIANTS here.
 711  *
 712  * Return zero if not present or options are invalid, non-zero if present.
 713  */
 714 int
 715 ip_checkrouteralert(struct mbuf *m)
 716 {
 717         struct ip *ip = mtod(m, struct ip *);
 718         u_char *cp;
 719         int opt, optlen, cnt, found_ra;
 720
 721         found_ra = 0;
 722         cp = (u_char *)(ip + 1);
 723         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 724         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 725                 opt = cp[IPOPT_OPTVAL];
 726                 if (opt == IPOPT_EOL)
 727                         break;
 728                 if (opt == IPOPT_NOP)
 729                         optlen = 1;
 730                 else {
 731 #ifdef INVARIANTS
 732                         if (cnt < IPOPT_OLEN + sizeof(*cp))
 733                                 break;
 734 #endif
 735                         optlen = cp[IPOPT_OLEN];
 736 #ifdef INVARIANTS
 737                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
 738                                 break;
 739 #endif
 740                 }
 741                 switch (opt) {
 742                 case IPOPT_RA:
 743 #ifdef INVARIANTS
 744                         if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
 745                             (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
 746                             break;
 747                         else
 748 #endif
 749                         found_ra = 1;
 750                         break;
 751                 default:
 752                         break;
 753                 }
 754         }
 755
 756         return (found_ra);
 757 }