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