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 VNET_DEFINE_STATIC(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 VNET_DEFINE_STATIC(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         struct epoch_tracker et;
 113
 114         /* Ignore or reject packets with IP options. */
 115         if (V_ip_doopts == 0)
 116                 return 0;
 117         else if (V_ip_doopts == 2) {
 118                 type = ICMP_UNREACH;
 119                 code = ICMP_UNREACH_FILTER_PROHIB;
 120                 goto bad_unlocked;
 121         }
 122
 123         NET_EPOCH_ENTER(et);
 124         dst = ip->ip_dst;
 125         cp = (u_char *)(ip + 1);
 126         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 127         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 128                 opt = cp[IPOPT_OPTVAL];
 129                 if (opt == IPOPT_EOL)
 130                         break;
 131                 if (opt == IPOPT_NOP)
 132                         optlen = 1;
 133                 else {
 134                         if (cnt < IPOPT_OLEN + sizeof(*cp)) {
 135                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 136                                 goto bad;
 137                         }
 138                         optlen = cp[IPOPT_OLEN];
 139                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
 140                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 141                                 goto bad;
 142                         }
 143                 }
 144                 switch (opt) {
 145
 146                 default:
 147                         break;
 148
 149                 /*
 150                  * Source routing with record.  Find interface with current
 151                  * destination address.  If none on this machine then drop if
 152                  * strictly routed, or do nothing if loosely routed.  Record
 153                  * interface address and bring up next address component.  If
 154                  * strictly routed make sure next address is on directly
 155                  * accessible net.
 156                  */
 157                 case IPOPT_LSRR:
 158                 case IPOPT_SSRR:
 159 #ifdef IPSTEALTH
 160                         if (V_ipstealth && pass > 0)
 161                                 break;
 162 #endif
 163                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
 164                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 165                                 goto bad;
 166                         }
 167                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
 168                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 169                                 goto bad;
 170                         }
 171                         ipaddr.sin_addr = ip->ip_dst;
 172                         if (ifa_ifwithaddr_check((struct sockaddr *)&ipaddr)
 173                             == 0) {
 174                                 if (opt == IPOPT_SSRR) {
 175                                         type = ICMP_UNREACH;
 176                                         code = ICMP_UNREACH_SRCFAIL;
 177                                         goto bad;
 178                                 }
 179                                 if (!V_ip_dosourceroute)
 180                                         goto nosourcerouting;
 181                                 /*
 182                                  * Loose routing, and not at next destination
 183                                  * yet; nothing to do except forward.
 184                                  */
 185                                 break;
 186                         }
 187                         off--;                  /* 0 origin */
 188                         if (off > optlen - (int)sizeof(struct in_addr)) {
 189                                 /*
 190                                  * End of source route.  Should be for us.
 191                                  */
 192                                 if (!V_ip_acceptsourceroute)
 193                                         goto nosourcerouting;
 194                                 save_rte(m, cp, ip->ip_src);
 195                                 break;
 196                         }
 197 #ifdef IPSTEALTH
 198                         if (V_ipstealth)
 199                                 goto dropit;
 200 #endif
 201                         if (!V_ip_dosourceroute) {
 202                                 if (V_ipforwarding) {
 203                                         char srcbuf[INET_ADDRSTRLEN];
 204                                         char dstbuf[INET_ADDRSTRLEN];
 205
 206                                         /*
 207                                          * Acting as a router, so generate
 208                                          * ICMP
 209                                          */
 210 nosourcerouting:
 211                                         log(LOG_WARNING,
 212                                             "attempted source route from %s "
 213                                             "to %s\n",
 214                                             inet_ntoa_r(ip->ip_src, srcbuf),
 215                                             inet_ntoa_r(ip->ip_dst, dstbuf));
 216                                         type = ICMP_UNREACH;
 217                                         code = ICMP_UNREACH_SRCFAIL;
 218                                         goto bad;
 219                                 } else {
 220                                         /*
 221                                          * Not acting as a router, so
 222                                          * silently drop.
 223                                          */
 224 #ifdef IPSTEALTH
 225 dropit:
 226 #endif
 227                                         IPSTAT_INC(ips_cantforward);
 228                                         m_freem(m);
 229                                         NET_EPOCH_EXIT(et);
 230                                         return (1);
 231                                 }
 232                         }
 233
 234                         /*
 235                          * locate outgoing interface
 236                          */
 237                         (void)memcpy(&ipaddr.sin_addr, cp + off,
 238                             sizeof(ipaddr.sin_addr));
 239
 240                         type = ICMP_UNREACH;
 241                         code = ICMP_UNREACH_SRCFAIL;
 242
 243                         if (opt == IPOPT_SSRR) {
 244 #define INA     struct in_ifaddr *
 245 #define SA      struct sockaddr *
 246                             ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr,
 247                                             RT_ALL_FIBS);
 248                             if (ia == NULL)
 249                                     ia = (INA)ifa_ifwithnet((SA)&ipaddr, 0,
 250                                                     RT_ALL_FIBS);
 251                                 if (ia == NULL)
 252                                         goto bad;
 253
 254                                 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
 255                                     sizeof(struct in_addr));
 256                         } else {
 257                                 /* XXX MRT 0 for routing */
 258                                 if (fib4_lookup_nh_ext(M_GETFIB(m),
 259                                     ipaddr.sin_addr, 0, 0, &nh_ext) != 0)
 260                                         goto bad;
 261
 262                                 memcpy(cp + off, &nh_ext.nh_src,
 263                                     sizeof(struct in_addr));
 264                         }
 265
 266                         ip->ip_dst = ipaddr.sin_addr;
 267                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 268                         /*
 269                          * Let ip_intr's mcast routing check handle mcast pkts
 270                          */
 271                         forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
 272                         break;
 273
 274                 case IPOPT_RR:
 275 #ifdef IPSTEALTH
 276                         if (V_ipstealth && pass == 0)
 277                                 break;
 278 #endif
 279                         if (optlen < IPOPT_OFFSET + sizeof(*cp)) {
 280                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 281                                 goto bad;
 282                         }
 283                         if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
 284                                 code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 285                                 goto bad;
 286                         }
 287                         /*
 288                          * If no space remains, ignore.
 289                          */
 290                         off--;                  /* 0 origin */
 291                         if (off > optlen - (int)sizeof(struct in_addr))
 292                                 break;
 293                         (void)memcpy(&ipaddr.sin_addr, &ip->ip_dst,
 294                             sizeof(ipaddr.sin_addr));
 295                         /*
 296                          * Locate outgoing interface; if we're the
 297                          * destination, use the incoming interface (should be
 298                          * same).
 299                          */
 300                         if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) != NULL) {
 301                                 memcpy(cp + off, &(IA_SIN(ia)->sin_addr),
 302                                     sizeof(struct in_addr));
 303                         } else if (fib4_lookup_nh_ext(M_GETFIB(m),
 304                             ipaddr.sin_addr, 0, 0, &nh_ext) == 0) {
 305                                 memcpy(cp + off, &nh_ext.nh_src,
 306                                     sizeof(struct in_addr));
 307                         } else {
 308                                 type = ICMP_UNREACH;
 309                                 code = ICMP_UNREACH_HOST;
 310                                 goto bad;
 311                         }
 312                         cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 313                         break;
 314
 315                 case IPOPT_TS:
 316 #ifdef IPSTEALTH
 317                         if (V_ipstealth && pass == 0)
 318                                 break;
 319 #endif
 320                         code = cp - (u_char *)ip;
 321                         if (optlen < 4 || optlen > 40) {
 322                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 323                                 goto bad;
 324                         }
 325                         if ((off = cp[IPOPT_OFFSET]) < 5) {
 326                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 327                                 goto bad;
 328                         }
 329                         if (off > optlen - (int)sizeof(int32_t)) {
 330                                 cp[IPOPT_OFFSET + 1] += (1 << 4);
 331                                 if ((cp[IPOPT_OFFSET + 1] & 0xf0) == 0) {
 332                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 333                                         goto bad;
 334                                 }
 335                                 break;
 336                         }
 337                         off--;                          /* 0 origin */
 338                         sin = (struct in_addr *)(cp + off);
 339                         switch (cp[IPOPT_OFFSET + 1] & 0x0f) {
 340
 341                         case IPOPT_TS_TSONLY:
 342                                 break;
 343
 344                         case IPOPT_TS_TSANDADDR:
 345                                 if (off + sizeof(uint32_t) +
 346                                     sizeof(struct in_addr) > optlen) {
 347                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 348                                         goto bad;
 349                                 }
 350                                 ipaddr.sin_addr = dst;
 351                                 ia = (INA)ifaof_ifpforaddr((SA)&ipaddr,
 352                                                             m->m_pkthdr.rcvif);
 353                                 if (ia == NULL)
 354                                         continue;
 355                                 (void)memcpy(sin, &IA_SIN(ia)->sin_addr,
 356                                     sizeof(struct in_addr));
 357                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 358                                 off += sizeof(struct in_addr);
 359                                 break;
 360
 361                         case IPOPT_TS_PRESPEC:
 362                                 if (off + sizeof(uint32_t) +
 363                                     sizeof(struct in_addr) > optlen) {
 364                                         code = &cp[IPOPT_OFFSET] - (u_char *)ip;
 365                                         goto bad;
 366                                 }
 367                                 (void)memcpy(&ipaddr.sin_addr, sin,
 368                                     sizeof(struct in_addr));
 369                                 if (ifa_ifwithaddr_check((SA)&ipaddr) == 0)
 370                                         continue;
 371                                 cp[IPOPT_OFFSET] += sizeof(struct in_addr);
 372                                 off += sizeof(struct in_addr);
 373                                 break;
 374
 375                         default:
 376                                 code = &cp[IPOPT_OFFSET + 1] - (u_char *)ip;
 377                                 goto bad;
 378                         }
 379                         ntime = iptime();
 380                         (void)memcpy(cp + off, &ntime, sizeof(uint32_t));
 381                         cp[IPOPT_OFFSET] += sizeof(uint32_t);
 382                 }
 383         }
 384         NET_EPOCH_EXIT(et);
 385         if (forward && V_ipforwarding) {
 386                 ip_forward(m, 1);
 387                 return (1);
 388         }
 389         return (0);
 390 bad:
 391         NET_EPOCH_EXIT(et);
 392 bad_unlocked:
 393         icmp_error(m, type, code, 0, 0);
 394         IPSTAT_INC(ips_badoptions);
 395         return (1);
 396 }
 397
 398 /*
 399  * Save incoming source route for use in replies, to be picked up later by
 400  * ip_srcroute if the receiver is interested.
 401  */
 402 static void
 403 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
 404 {
 405         unsigned olen;
 406         struct ipopt_tag *opts;
 407
 408         opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
 409             sizeof(struct ipopt_tag), M_NOWAIT);
 410         if (opts == NULL)
 411                 return;
 412
 413         olen = option[IPOPT_OLEN];
 414         if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
 415                 m_tag_free((struct m_tag *)opts);
 416                 return;
 417         }
 418         bcopy(option, opts->ip_srcrt.srcopt, olen);
 419         opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
 420         opts->ip_srcrt.dst = dst;
 421         m_tag_prepend(m, (struct m_tag *)opts);
 422 }
 423
 424 /*
 425  * Retrieve incoming source route for use in replies, in the same form used
 426  * by setsockopt.  The first hop is placed before the options, will be
 427  * removed later.
 428  */
 429 struct mbuf *
 430 ip_srcroute(struct mbuf *m0)
 431 {
 432         struct in_addr *p, *q;
 433         struct mbuf *m;
 434         struct ipopt_tag *opts;
 435
 436         opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
 437         if (opts == NULL)
 438                 return (NULL);
 439
 440         if (opts->ip_nhops == 0)
 441                 return (NULL);
 442         m = m_get(M_NOWAIT, MT_DATA);
 443         if (m == NULL)
 444                 return (NULL);
 445
 446 #define OPTSIZ  (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
 447
 448         /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
 449         m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
 450             sizeof(struct in_addr) + OPTSIZ;
 451
 452         /*
 453          * First, save first hop for return route.
 454          */
 455         p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
 456         *(mtod(m, struct in_addr *)) = *p--;
 457
 458         /*
 459          * Copy option fields and padding (nop) to mbuf.
 460          */
 461         opts->ip_srcrt.nop = IPOPT_NOP;
 462         opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
 463         (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
 464             &(opts->ip_srcrt.nop), OPTSIZ);
 465         q = (struct in_addr *)(mtod(m, caddr_t) +
 466             sizeof(struct in_addr) + OPTSIZ);
 467 #undef OPTSIZ
 468         /*
 469          * Record return path as an IP source route, reversing the path
 470          * (pointers are now aligned).
 471          */
 472         while (p >= opts->ip_srcrt.route) {
 473                 *q++ = *p--;
 474         }
 475         /*
 476          * Last hop goes to final destination.
 477          */
 478         *q = opts->ip_srcrt.dst;
 479         m_tag_delete(m0, (struct m_tag *)opts);
 480         return (m);
 481 }
 482
 483 /*
 484  * Strip out IP options, at higher level protocol in the kernel.
 485  */
 486 void
 487 ip_stripoptions(struct mbuf *m)
 488 {
 489         struct ip *ip = mtod(m, struct ip *);
 490         int olen;
 491
 492         olen = (ip->ip_hl << 2) - sizeof(struct ip);
 493         m->m_len -= olen;
 494         if (m->m_flags & M_PKTHDR)
 495                 m->m_pkthdr.len -= olen;
 496         ip->ip_len = htons(ntohs(ip->ip_len) - olen);
 497         ip->ip_hl = sizeof(struct ip) >> 2;
 498
 499         bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1),
 500             (size_t )(m->m_len - sizeof(struct ip)));
 501 }
 502
 503 /*
 504  * Insert IP options into preformed packet.  Adjust IP destination as
 505  * required for IP source routing, as indicated by a non-zero in_addr at the
 506  * start of the options.
 507  *
 508  * XXX This routine assumes that the packet has no options in place.
 509  */
 510 struct mbuf *
 511 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
 512 {
 513         struct ipoption *p = mtod(opt, struct ipoption *);
 514         struct mbuf *n;
 515         struct ip *ip = mtod(m, struct ip *);
 516         unsigned optlen;
 517
 518         optlen = opt->m_len - sizeof(p->ipopt_dst);
 519         if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) {
 520                 *phlen = 0;
 521                 return (m);             /* XXX should fail */
 522         }
 523         if (p->ipopt_dst.s_addr)
 524                 ip->ip_dst = p->ipopt_dst;
 525         if (!M_WRITABLE(m) || M_LEADINGSPACE(m) < optlen) {
 526                 n = m_gethdr(M_NOWAIT, MT_DATA);
 527                 if (n == NULL) {
 528                         *phlen = 0;
 529                         return (m);
 530                 }
 531                 m_move_pkthdr(n, m);
 532                 n->m_pkthdr.rcvif = NULL;
 533                 n->m_pkthdr.len += optlen;
 534                 m->m_len -= sizeof(struct ip);
 535                 m->m_data += sizeof(struct ip);
 536                 n->m_next = m;
 537                 m = n;
 538                 m->m_len = optlen + sizeof(struct ip);
 539                 m->m_data += max_linkhdr;
 540                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 541         } else {
 542                 m->m_data -= optlen;
 543                 m->m_len += optlen;
 544                 m->m_pkthdr.len += optlen;
 545                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 546         }
 547         ip = mtod(m, struct ip *);
 548         bcopy(p->ipopt_list, ip + 1, optlen);
 549         *phlen = sizeof(struct ip) + optlen;
 550         ip->ip_v = IPVERSION;
 551         ip->ip_hl = *phlen >> 2;
 552         ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
 553         return (m);
 554 }
 555
 556 /*
 557  * Copy options from ip to jp, omitting those not copied during
 558  * fragmentation.
 559  */
 560 int
 561 ip_optcopy(struct ip *ip, struct ip *jp)
 562 {
 563         u_char *cp, *dp;
 564         int opt, optlen, cnt;
 565
 566         cp = (u_char *)(ip + 1);
 567         dp = (u_char *)(jp + 1);
 568         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 569         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 570                 opt = cp[0];
 571                 if (opt == IPOPT_EOL)
 572                         break;
 573                 if (opt == IPOPT_NOP) {
 574                         /* Preserve for IP mcast tunnel's LSRR alignment. */
 575                         *dp++ = IPOPT_NOP;
 576                         optlen = 1;
 577                         continue;
 578                 }
 579
 580                 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
 581                     ("ip_optcopy: malformed ipv4 option"));
 582                 optlen = cp[IPOPT_OLEN];
 583                 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
 584                     ("ip_optcopy: malformed ipv4 option"));
 585
 586                 /* Bogus lengths should have been caught by ip_dooptions. */
 587                 if (optlen > cnt)
 588                         optlen = cnt;
 589                 if (IPOPT_COPIED(opt)) {
 590                         bcopy(cp, dp, optlen);
 591                         dp += optlen;
 592                 }
 593         }
 594         for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
 595                 *dp++ = IPOPT_EOL;
 596         return (optlen);
 597 }
 598
 599 /*
 600  * Set up IP options in pcb for insertion in output packets.  Store in mbuf
 601  * with pointer in pcbopt, adding pseudo-option with destination address if
 602  * source routed.
 603  */
 604 int
 605 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
 606 {
 607         int cnt, optlen;
 608         u_char *cp;
 609         struct mbuf **pcbopt;
 610         u_char opt;
 611
 612         INP_WLOCK_ASSERT(inp);
 613
 614         pcbopt = &inp->inp_options;
 615
 616         /* turn off any old options */
 617         if (*pcbopt)
 618                 (void)m_free(*pcbopt);
 619         *pcbopt = NULL;
 620         if (m == NULL || m->m_len == 0) {
 621                 /*
 622                  * Only turning off any previous options.
 623                  */
 624                 if (m != NULL)
 625                         (void)m_free(m);
 626                 return (0);
 627         }
 628
 629         if (m->m_len % sizeof(int32_t))
 630                 goto bad;
 631         /*
 632          * IP first-hop destination address will be stored before actual
 633          * options; move other options back and clear it when none present.
 634          */
 635         if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
 636                 goto bad;
 637         cnt = m->m_len;
 638         m->m_len += sizeof(struct in_addr);
 639         cp = mtod(m, u_char *) + sizeof(struct in_addr);
 640         bcopy(mtod(m, void *), cp, (unsigned)cnt);
 641         bzero(mtod(m, void *), sizeof(struct in_addr));
 642
 643         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 644                 opt = cp[IPOPT_OPTVAL];
 645                 if (opt == IPOPT_EOL)
 646                         break;
 647                 if (opt == IPOPT_NOP)
 648                         optlen = 1;
 649                 else {
 650                         if (cnt < IPOPT_OLEN + sizeof(*cp))
 651                                 goto bad;
 652                         optlen = cp[IPOPT_OLEN];
 653                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
 654                                 goto bad;
 655                 }
 656                 switch (opt) {
 657
 658                 default:
 659                         break;
 660
 661                 case IPOPT_LSRR:
 662                 case IPOPT_SSRR:
 663                         /*
 664                          * User process specifies route as:
 665                          *
 666                          *      ->A->B->C->D
 667                          *
 668                          * D must be our final destination (but we can't
 669                          * check that since we may not have connected yet).
 670                          * A is first hop destination, which doesn't appear
 671                          * in actual IP option, but is stored before the
 672                          * options.
 673                          */
 674                         /* XXX-BZ PRIV_NETINET_SETHDROPTS? */
 675                         if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
 676                                 goto bad;
 677                         m->m_len -= sizeof(struct in_addr);
 678                         cnt -= sizeof(struct in_addr);
 679                         optlen -= sizeof(struct in_addr);
 680                         cp[IPOPT_OLEN] = optlen;
 681                         /*
 682                          * Move first hop before start of options.
 683                          */
 684                         bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
 685                             sizeof(struct in_addr));
 686                         /*
 687                          * Then copy rest of options back
 688                          * to close up the deleted entry.
 689                          */
 690                         bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
 691                             &cp[IPOPT_OFFSET+1],
 692                             (unsigned)cnt - (IPOPT_MINOFF - 1));
 693                         break;
 694                 }
 695         }
 696         if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
 697                 goto bad;
 698         *pcbopt = m;
 699         return (0);
 700
 701 bad:
 702         (void)m_free(m);
 703         return (EINVAL);
 704 }
 705
 706 /*
 707  * Check for the presence of the IP Router Alert option [RFC2113]
 708  * in the header of an IPv4 datagram.
 709  *
 710  * This call is not intended for use from the forwarding path; it is here
 711  * so that protocol domains may check for the presence of the option.
 712  * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
 713  * option does not have much relevance to the implementation, though this
 714  * may change in future.
 715  * Router alert options SHOULD be passed if running in IPSTEALTH mode and
 716  * we are not the endpoint.
 717  * Length checks on individual options should already have been performed
 718  * by ip_dooptions() therefore they are folded under INVARIANTS here.
 719  *
 720  * Return zero if not present or options are invalid, non-zero if present.
 721  */
 722 int
 723 ip_checkrouteralert(struct mbuf *m)
 724 {
 725         struct ip *ip = mtod(m, struct ip *);
 726         u_char *cp;
 727         int opt, optlen, cnt, found_ra;
 728
 729         found_ra = 0;
 730         cp = (u_char *)(ip + 1);
 731         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 732         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 733                 opt = cp[IPOPT_OPTVAL];
 734                 if (opt == IPOPT_EOL)
 735                         break;
 736                 if (opt == IPOPT_NOP)
 737                         optlen = 1;
 738                 else {
 739 #ifdef INVARIANTS
 740                         if (cnt < IPOPT_OLEN + sizeof(*cp))
 741                                 break;
 742 #endif
 743                         optlen = cp[IPOPT_OLEN];
 744 #ifdef INVARIANTS
 745                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
 746                                 break;
 747 #endif
 748                 }
 749                 switch (opt) {
 750                 case IPOPT_RA:
 751 #ifdef INVARIANTS
 752                         if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
 753                             (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
 754                             break;
 755                         else
 756 #endif
 757                         found_ra = 1;
 758                         break;
 759                 default:
 760                         break;
 761                 }
 762         }
 763
 764         return (found_ra);
 765 }