sys/netinet/ip_options.c

   1 /*
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1982, 1986, 1988, 1993
   5  *      The Regents of the University of California.
   6  * Copyright (c) 2005 Andre Oppermann, Internet Business Solutions AG.
   7  * All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  * 3. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #include <sys/cdefs.h>
  35 __FBSDID("$FreeBSD$");
  36
  37 #include "opt_ipstealth.h"
  38
  39 #include <sys/param.h>
  40 #include <sys/systm.h>
  41 #include <sys/mbuf.h>
  42 #include <sys/domain.h>
  43 #include <sys/protosw.h>
  44 #include <sys/socket.h>
  45 #include <sys/time.h>
  46 #include <sys/kernel.h>
  47 #include <sys/syslog.h>
  48 #include <sys/sysctl.h>
  49
  50 #include <net/if.h>
  51 #include <net/if_types.h>
  52 #include <net/if_var.h>
  53 #include <net/if_dl.h>
  54 #include <net/route.h>
  55 #include <net/netisr.h>
  56 #include <net/vnet.h>
  57
  58 #include <netinet/in.h>
  59 #include <netinet/in_fib.h>
  60 #include <netinet/in_systm.h>
  61 #include <netinet/in_var.h>
  62 #include <netinet/ip.h>
  63 #include <netinet/in_pcb.h>
  64 #include <netinet/ip_var.h>
  65 #include <netinet/ip_options.h>
  66 #include <netinet/ip_icmp.h>
  67 #include <machine/in_cksum.h>
  68
  69 #include <sys/socketvar.h>
  70
  71 static VNET_DEFINE(int, ip_dosourceroute);
  72 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute,
  73     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_dosourceroute), 0,
  74     "Enable forwarding source routed IP packets");
  75 #define V_ip_dosourceroute      VNET(ip_dosourceroute)
  76
  77 static VNET_DEFINE(int, ip_acceptsourceroute);
  78 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute,
  79     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_acceptsourceroute), 0,
  80     "Enable accepting source routed IP packets");
  81 #define V_ip_acceptsourceroute  VNET(ip_acceptsourceroute)
  82
  83 VNET_DEFINE(int, ip_doopts) = 1; /* 0 = ignore, 1 = process, 2 = reject */
  84 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_VNET | CTLFLAG_RW,
  85     &VNET_NAME(ip_doopts), 0, "Enable IP options processing ([LS]SRR, RR, TS)");
  86
  87 static void     save_rte(struct mbuf *m, u_char *, struct in_addr);
  88
  89 /*
  90  * Do option processing on a datagram, possibly discarding it if bad options
  91  * are encountered, or forwarding it if source-routed.
  92  *
  93  * The pass argument is used when operating in the IPSTEALTH mode to tell
  94  * what options to process: [LS]SRR (pass 0) or the others (pass 1).  The
  95  * reason for as many as two passes is that when doing IPSTEALTH, non-routing
  96  * options should be processed only if the packet is for us.
  97  *
  98  * Returns 1 if packet has been forwarded/freed, 0 if the packet should be
  99  * processed further.
 100  */
 101 int
 102 ip_dooptions(struct mbuf *m, int pass)
 103 {
 104         struct ip *ip = mtod(m, struct ip *);
 105         u_char *cp;
 106         struct in_ifaddr *ia;
 107         int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
 108         struct in_addr *sin, dst;
 109         uint32_t ntime;
 110         struct nhop4_extended nh_ext;
 111         struct  sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
 112
 113         NET_EPOCH_ENTER();
 114         /* Ignore or reject packets with IP options. */
 115         if (V_ip_doopts == 0)
 116                 return 0;
 117         else if (V_ip_doopts == 2) {
 118                 type = ICMP_UNREACH;
 119                 code = ICMP_UNREACH_FILTER_PROHIB;
 120                 goto bad;
 121         }
 122
 123         dst = ip->ip_dst;
 124         cp = (u_char *)(ip + 1);
 125         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 126         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 127                 opt = cp[IPOPT_OPTVAL];
 128                 if (opt == IPOPT_EOL)
 129                         break;
 130                 if (opt == IPOPT_NOP)
 131                         optlen = 1;
 132                 else {
 133                         if (cnt < IPOPT_OLEN + sizeof(*cp)) {
 134                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 135                                 goto bad;
 136                         }
 137                         optlen = cp[IPOPT_OLEN];
 138                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
 139                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 140                                 goto bad;
 141                         }
 142                 }
 143                 switch (opt) {
 144
 145                 default:
 146                         break;
 147
 148                 /*
 149                  * Source routing with record.  Find interface with current
 150                  * destination address.  If none on this machine then drop if
 151                  * strictly routed, or do nothing if loosely routed.  Record
 152                  * interface address and bring up next address component.  If
 153                  * strictly routed make sure next address is on directly
 154                  * accessible net.
 155                  */
 156                 case IPOPT_LSRR:
 157                 case IPOPT_SSRR:
 158 #ifdef IPSTEALTH
 159                         if (V_ipstealth && pass > 0)
 160                                 break;
 161 #endif
 162                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
 163                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 164                                 goto bad;
 165                         }
 166                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
 167                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 168                                 goto bad;
 169                         }
 170                         ipaddr.sin_addr = ip->ip_dst;
 171                         if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr)
 172                             == 0) {
 173                                 if (opt == IPOPT_SSRR) {
 174                                         type = ICMP_UNREACH;
 175                                         code = ICMP_UNREACH_SRCFAIL;
 176                                         goto bad;
 177                                 }
 178                                 if (!V_ip_dosourceroute)
 179                                         goto nosourcerouting;
 180                                 /*
 181                                  * Loose routing, and not at next destination
 182                                  * yet; nothing to do except forward.
 183                                  */
 184                                 break;
 185                         }
 186                         off--;                  /* 0 origin */
 187                         if (off > optlen - (int)sizeof(struct in_addr)) {
 188                                 /*
 189                                  * End of source route.  Should be for us.
 190                                  */
 191                                 if (!V_ip_acceptsourceroute)
 192                                         goto nosourcerouting;
 193                                 save_rte(m, cp, ip->ip_src);
 194                                 break;
 195                         }
 196 #ifdef IPSTEALTH
 197                         if (V_ipstealth)
 198                                 goto dropit;
 199 #endif
 200                         if (!V_ip_dosourceroute) {
 201                                 if (V_ipforwarding) {
 202                                         char srcbuf[INET_ADDRSTRLEN];
 203                                         char dstbuf[INET_ADDRSTRLEN];
 204
 205                                         /*
 206                                          * Acting as a router, so generate
 207                                          * ICMP
 208                                          */
 209 nosourcerouting:
 210                                         log(LOG_WARNING,
 211                                             "attempted source route from %s "
 212                                             "to %s\n",
 213                                             inet_ntoa_r(ip->ip_src, srcbuf),
 214                                             inet_ntoa_r(ip->ip_dst, dstbuf));
 215                                         type = ICMP_UNREACH;
 216                                         code = ICMP_UNREACH_SRCFAIL;
 217                                         goto bad;
 218                                 } else {
 219                                         /*
 220                                          * Not acting as a router, so
 221                                          * silently drop.
 222                                          */
 223 #ifdef IPSTEALTH
 224 dropit:
 225 #endif
 226                                         IPSTAT_INC(ips_cantforward);
 227                                         m_freem(m);
 228                                         NET_EPOCH_EXIT();
 229                                         return (1);
 230                                 }
 231                         }
 232
 233                         /*
 234                          * locate outgoing interface
 235                          */
 236                         (void)memcpy(&ipaddr.sin_addr, cp + off,
 237                             sizeof(ipaddr.sin_addr));
 238
 239                         type = ICMP_UNREACH;
 240                         code = ICMP_UNREACH_SRCFAIL;
 241
 242                         if (opt == IPOPT_SSRR) {
 243 #define INA     struct in_ifaddr *
 244 #define SA      struct sockaddr *
 245                             ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr,
 246                                             RT_ALL_FIBS);
 247                             if (ia == NULL)
 248                                     ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0,
 249                                                     RT_ALL_FIBS);
 250                                 if (ia == NULL)
 251                                         goto bad;
 252
 253                                 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
 254                                     sizeof(struct in_addr));
 255                         } else {
 256                                 /* XXX MRT 0 for routing */
 257                                 if (fib4_lookup_nh_ext(M_GETFIB(m),
 258                                     ipaddr.sin_addr, 0, 0, &nh_ext) != 0)
 259                                         goto bad;
 260
 261                                 memcpy(cp + off, &nh_ext.nh_src,
 262                                     sizeof(struct in_addr));
 263                         }
 264
 265                         ip->ip_dst = ipaddr.sin_addr;
 266                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 267                         /*
 268                          * Let ip_intr's mcast routing check handle mcast pkts
 269                          */
 270                         forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
 271                         break;
 272
 273                 case IPOPT_RR:
 274 #ifdef IPSTEALTH
 275                         if (V_ipstealth && pass == 0)
 276                                 break;
 277 #endif
 278                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
 279                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 280                                 goto bad;
 281                         }
 282                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
 283                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 284                                 goto bad;
 285                         }
 286                         /*
 287                          * If no space remains, ignore.
 288                          */
 289                         off--;                  /* 0 origin */
 290                         if (off > optlen - (int)sizeof(struct in_addr))
 291                                 break;
 292                         (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
 293                             sizeof(ipaddr.sin_addr));
 294                         /*
 295                          * Locate outgoing interface; if we're the
 296                          * destination, use the incoming interface (should be
 297                          * same).
 298                          */
 299                         if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) != NULL) {
 300                                 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
 301                                     sizeof(struct in_addr));
 302                         } else if (fib4_lookup_nh_ext(M_GETFIB(m),
 303                             ipaddr.sin_addr, 0, 0, &nh_ext) == 0) {
 304                                 memcpy(cp + off, &nh_ext.nh_src,
 305                                     sizeof(struct in_addr));
 306                         } else {
 307                                 type = ICMP_UNREACH;
 308                                 code = ICMP_UNREACH_HOST;
 309                                 goto bad;
 310                         }
 311                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 312                         break;
 313
 314                 case IPOPT_TS:
 315 #ifdef IPSTEALTH
 316                         if (V_ipstealth && pass == 0)
 317                                 break;
 318 #endif
 319                         code = cp - (u_char *)ip;
 320                         if (optlen < 4 || optlen > 40) {
 321                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 322                                 goto bad;
 323                         }
 324                         if ((off = cp[IPOPT_OFFSET]) < 5) {
 325                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 326                                 goto bad;
 327                         }
 328                         if (off > optlen - (int)sizeof(int32_t)) {
 329                                 cp[IPOPT_OFFSET + 1] += (1 << 4);
 330                                 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
 331                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 332                                         goto bad;
 333                                 }
 334                                 break;
 335                         }
 336                         off--;                          /* 0 origin */
 337                         sin = (struct in_addr *)(cp + off);
 338                         switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
 339
 340                         case IPOPT_TS_TSONLY:
 341                                 break;
 342
 343                         case IPOPT_TS_TSANDADDR:
 344                                 if (off + sizeof(uint32_t) +
 345                                     sizeof(struct in_addr) > optlen) {
 346                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 347                                         goto bad;
 348                                 }
 349                                 ipaddr.sin_addr = dst;
 350                                 ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
 351                                                             m->m_pkthdr.rcvif);
 352                                 if (ia == NULL)
 353                                         continue;
 354                                 (void)memcpy(sin, &IA_SIN(ia)->sin_addr,
 355                                     sizeof(struct in_addr));
 356                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 357                                 off += sizeof(struct in_addr);
 358                                 break;
 359
 360                         case IPOPT_TS_PRESPEC:
 361                                 if (off + sizeof(uint32_t) +
 362                                     sizeof(struct in_addr) > optlen) {
 363                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 364                                         goto bad;
 365                                 }
 366                                 (void)memcpy(&ipaddr.sin_addr, sin,
 367                                     sizeof(struct in_addr));
 368                                 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0)
 369                                         continue;
 370                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 371                                 off += sizeof(struct in_addr);
 372                                 break;
 373
 374                         default:
 375                                 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
 376                                 goto bad;
 377                         }
 378                         ntime = iptime();
 379                         (void)memcpy(cp + off, &ntime, sizeof(uint32_t));
 380                         cp[IPOPT_OFFSET] += sizeof(uint32_t);
 381                 }
 382         }
 383         NET_EPOCH_EXIT();
 384         if (forward && V_ipforwarding) {
 385                 ip_forward(m, 1);
 386                 return (1);
 387         }
 388         return (0);
 389 bad:
 390         NET_EPOCH_EXIT();
 391         icmp_error(m, type, code, 0, 0);
 392         IPSTAT_INC(ips_badoptions);
 393         return (1);
 394 }
 395
 396 /*
 397  * Save incoming source route for use in replies, to be picked up later by
 398  * ip_srcroute if the receiver is interested.
 399  */
 400 static void
 401 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
 402 {
 403         unsigned olen;
 404         struct ipopt_tag *opts;
 405
 406         opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
 407             sizeof(struct ipopt_tag), M_NOWAIT);
 408         if (opts == NULL)
 409                 return;
 410
 411         olen = option[IPOPT_OLEN];
 412         if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
 413                 m_tag_free((struct m_tag *)opts);
 414                 return;
 415         }
 416         bcopy(option, opts->ip_srcrt.srcopt, olen);
 417         opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
 418         opts->ip_srcrt.dst = dst;
 419         m_tag_prepend(m, (struct m_tag *)opts);
 420 }
 421
 422 /*
 423  * Retrieve incoming source route for use in replies, in the same form used
 424  * by setsockopt.  The first hop is placed before the options, will be
 425  * removed later.
 426  */
 427 struct mbuf *
 428 ip_srcroute(struct mbuf *m0)
 429 {
 430         struct in_addr *p, *q;
 431         struct mbuf *m;
 432         struct ipopt_tag *opts;
 433
 434         opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
 435         if (opts == NULL)
 436                 return (NULL);
 437
 438         if (opts->ip_nhops == 0)
 439                 return (NULL);
 440         m = m_get(M_NOWAIT, MT_DATA);
 441         if (m == NULL)
 442                 return (NULL);
 443
 444 #define OPTSIZ  (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
 445
 446         /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
 447         m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
 448             sizeof(struct in_addr) + OPTSIZ;
 449
 450         /*
 451          * First, save first hop for return route.
 452          */
 453         p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
 454         *(mtod(m, struct in_addr *)) = *p--;
 455
 456         /*
 457          * Copy option fields and padding (nop) to mbuf.
 458          */
 459         opts->ip_srcrt.nop = IPOPT_NOP;
 460         opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
 461         (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
 462             &(opts->ip_srcrt.nop), OPTSIZ);
 463         q = (struct in_addr *)(mtod(m, caddr_t) +
 464             sizeof(struct in_addr) + OPTSIZ);
 465 #undef OPTSIZ
 466         /*
 467          * Record return path as an IP source route, reversing the path
 468          * (pointers are now aligned).
 469          */
 470         while (p >= opts->ip_srcrt.route) {
 471                 *q++ = *p--;
 472         }
 473         /*
 474          * Last hop goes to final destination.
 475          */
 476         *q = opts->ip_srcrt.dst;
 477         m_tag_delete(m0, (struct m_tag *)opts);
 478         return (m);
 479 }
 480
 481 /*
 482  * Strip out IP options, at higher level protocol in the kernel.
 483  */
 484 void
 485 ip_stripoptions(struct mbuf *m)
 486 {
 487         struct ip *ip = mtod(m, struct ip *);
 488         int olen;
 489
 490         olen = (ip->ip_hl << 2) - sizeof(struct ip);
 491         m->m_len -= olen;
 492         if (m->m_flags & M_PKTHDR)
 493                 m->m_pkthdr.len -= olen;
 494         ip->ip_len = htons(ntohs(ip->ip_len) - olen);
 495         ip->ip_hl = sizeof(struct ip) >> 2;
 496
 497         bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1),
 498             (size_t )(m->m_len - sizeof(struct ip)));
 499 }
 500
 501 /*
 502  * Insert IP options into preformed packet.  Adjust IP destination as
 503  * required for IP source routing, as indicated by a non-zero in_addr at the
 504  * start of the options.
 505  *
 506  * XXX This routine assumes that the packet has no options in place.
 507  */
 508 struct mbuf *
 509 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
 510 {
 511         struct ipoption *p = mtod(opt, struct ipoption *);
 512         struct mbuf *n;
 513         struct ip *ip = mtod(m, struct ip *);
 514         unsigned optlen;
 515
 516         optlen = opt->m_len - sizeof(p->ipopt_dst);
 517         if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) {
 518                 *phlen = 0;
 519                 return (m);             /* XXX should fail */
 520         }
 521         if (p->ipopt_dst.s_addr)
 522                 ip->ip_dst = p->ipopt_dst;
 523         if (!M_WRITABLE(m) || M_LEADINGSPACE(m) < optlen) {
 524                 n = m_gethdr(M_NOWAIT, MT_DATA);
 525                 if (n == NULL) {
 526                         *phlen = 0;
 527                         return (m);
 528                 }
 529                 m_move_pkthdr(n, m);
 530                 n->m_pkthdr.rcvif = NULL;
 531                 n->m_pkthdr.len += optlen;
 532                 m->m_len -= sizeof(struct ip);
 533                 m->m_data += sizeof(struct ip);
 534                 n->m_next = m;
 535                 m = n;
 536                 m->m_len = optlen + sizeof(struct ip);
 537                 m->m_data += max_linkhdr;
 538                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 539         } else {
 540                 m->m_data -= optlen;
 541                 m->m_len += optlen;
 542                 m->m_pkthdr.len += optlen;
 543                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 544         }
 545         ip = mtod(m, struct ip *);
 546         bcopy(p->ipopt_list, ip + 1, optlen);
 547         *phlen = sizeof(struct ip) + optlen;
 548         ip->ip_v = IPVERSION;
 549         ip->ip_hl = *phlen >> 2;
 550         ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
 551         return (m);
 552 }
 553
 554 /*
 555  * Copy options from ip to jp, omitting those not copied during
 556  * fragmentation.
 557  */
 558 int
 559 ip_optcopy(struct ip *ip, struct ip *jp)
 560 {
 561         u_char *cp, *dp;
 562         int opt, optlen, cnt;
 563
 564         cp = (u_char *)(ip + 1);
 565         dp = (u_char *)(jp + 1);
 566         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 567         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 568                 opt = cp[0];
 569                 if (opt == IPOPT_EOL)
 570                         break;
 571                 if (opt == IPOPT_NOP) {
 572                         /* Preserve for IP mcast tunnel's LSRR alignment. */
 573                         *dp++ = IPOPT_NOP;
 574                         optlen = 1;
 575                         continue;
 576                 }
 577
 578                 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
 579                     ("ip_optcopy: malformed ipv4 option"));
 580                 optlen = cp[IPOPT_OLEN];
 581                 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
 582                     ("ip_optcopy: malformed ipv4 option"));
 583
 584                 /* Bogus lengths should have been caught by ip_dooptions. */
 585                 if (optlen > cnt)
 586                         optlen = cnt;
 587                 if (IPOPT_COPIED(opt)) {
 588                         bcopy(cp, dp, optlen);
 589                         dp += optlen;
 590                 }
 591         }
 592         for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
 593                 *dp++ = IPOPT_EOL;
 594         return (optlen);
 595 }
 596
 597 /*
 598  * Set up IP options in pcb for insertion in output packets.  Store in mbuf
 599  * with pointer in pcbopt, adding pseudo-option with destination address if
 600  * source routed.
 601  */
 602 int
 603 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
 604 {
 605         int cnt, optlen;
 606         u_char *cp;
 607         struct mbuf **pcbopt;
 608         u_char opt;
 609
 610         INP_WLOCK_ASSERT(inp);
 611
 612         pcbopt = &inp->inp_options;
 613
 614         /* turn off any old options */
 615         if (*pcbopt)
 616                 (void)m_free(*pcbopt);
 617         *pcbopt = NULL;
 618         if (m == NULL || m->m_len == 0) {
 619                 /*
 620                  * Only turning off any previous options.
 621                  */
 622                 if (m != NULL)
 623                         (void)m_free(m);
 624                 return (0);
 625         }
 626
 627         if (m->m_len % sizeof(int32_t))
 628                 goto bad;
 629         /*
 630          * IP first-hop destination address will be stored before actual
 631          * options; move other options back and clear it when none present.
 632          */
 633         if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
 634                 goto bad;
 635         cnt = m->m_len;
 636         m->m_len += sizeof(struct in_addr);
 637         cp = mtod(m, u_char *) + sizeof(struct in_addr);
 638         bcopy(mtod(m, void *), cp, (unsigned)cnt);
 639         bzero(mtod(m, void *), sizeof(struct in_addr));
 640
 641         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 642                 opt = cp[IPOPT_OPTVAL];
 643                 if (opt == IPOPT_EOL)
 644                         break;
 645                 if (opt == IPOPT_NOP)
 646                         optlen = 1;
 647                 else {
 648                         if (cnt < IPOPT_OLEN + sizeof(*cp))
 649                                 goto bad;
 650                         optlen = cp[IPOPT_OLEN];
 651                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
 652                                 goto bad;
 653                 }
 654                 switch (opt) {
 655
 656                 default:
 657                         break;
 658
 659                 case IPOPT_LSRR:
 660                 case IPOPT_SSRR:
 661                         /*
 662                          * User process specifies route as:
 663                          *
 664                          *      ->A->B->C->D
 665                          *
 666                          * D must be our final destination (but we can't
 667                          * check that since we may not have connected yet).
 668                          * A is first hop destination, which doesn't appear
 669                          * in actual IP option, but is stored before the
 670                          * options.
 671                          */
 672                         /* XXX-BZ PRIV_NETINET_SETHDROPTS? */
 673                         if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
 674                                 goto bad;
 675                         m->m_len -= sizeof(struct in_addr);
 676                         cnt -= sizeof(struct in_addr);
 677                         optlen -= sizeof(struct in_addr);
 678                         cp[IPOPT_OLEN] = optlen;
 679                         /*
 680                          * Move first hop before start of options.
 681                          */
 682                         bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
 683                             sizeof(struct in_addr));
 684                         /*
 685                          * Then copy rest of options back
 686                          * to close up the deleted entry.
 687                          */
 688                         bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
 689                             &cp[IPOPT_OFFSET+1],
 690                             (unsigned)cnt - (IPOPT_MINOFF - 1));
 691                         break;
 692                 }
 693         }
 694         if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
 695                 goto bad;
 696         *pcbopt = m;
 697         return (0);
 698
 699 bad:
 700         (void)m_free(m);
 701         return (EINVAL);
 702 }
 703
 704 /*
 705  * Check for the presence of the IP Router Alert option [RFC2113]
 706  * in the header of an IPv4 datagram.
 707  *
 708  * This call is not intended for use from the forwarding path; it is here
 709  * so that protocol domains may check for the presence of the option.
 710  * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
 711  * option does not have much relevance to the implementation, though this
 712  * may change in future.
 713  * Router alert options SHOULD be passed if running in IPSTEALTH mode and
 714  * we are not the endpoint.
 715  * Length checks on individual options should already have been performed
 716  * by ip_dooptions() therefore they are folded under INVARIANTS here.
 717  *
 718  * Return zero if not present or options are invalid, non-zero if present.
 719  */
 720 int
 721 ip_checkrouteralert(struct mbuf *m)
 722 {
 723         struct ip *ip = mtod(m, struct ip *);
 724         u_char *cp;
 725         int opt, optlen, cnt, found_ra;
 726
 727         found_ra = 0;
 728         cp = (u_char *)(ip + 1);
 729         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 730         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 731                 opt = cp[IPOPT_OPTVAL];
 732                 if (opt == IPOPT_EOL)
 733                         break;
 734                 if (opt == IPOPT_NOP)
 735                         optlen = 1;
 736                 else {
 737 #ifdef INVARIANTS
 738                         if (cnt < IPOPT_OLEN + sizeof(*cp))
 739                                 break;
 740 #endif
 741                         optlen = cp[IPOPT_OLEN];
 742 #ifdef INVARIANTS
 743                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
 744                                 break;
 745 #endif
 746                 }
 747                 switch (opt) {
 748                 case IPOPT_RA:
 749 #ifdef INVARIANTS
 750                         if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
 751                             (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
 752                             break;
 753                         else
 754 #endif
 755                         found_ra = 1;
 756                         break;
 757                 default:
 758                         break;
 759                 }
 760         }
 761
 762         return (found_ra);
 763 }