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/route/nhop.h>
  56 #include <net/netisr.h>
  57 #include <net/vnet.h>
  58
  59 #include <netinet/in.h>
  60 #include <netinet/in_fib.h>
  61 #include <netinet/in_systm.h>
  62 #include <netinet/in_var.h>
  63 #include <netinet/ip.h>
  64 #include <netinet/in_pcb.h>
  65 #include <netinet/ip_var.h>
  66 #include <netinet/ip_options.h>
  67 #include <netinet/ip_icmp.h>
  68 #include <machine/in_cksum.h>
  69
  70 #include <sys/socketvar.h>
  71
  72 VNET_DEFINE_STATIC(int, ip_dosourceroute);
  73 SYSCTL_INT(_net_inet_ip, IPCTL_SOURCEROUTE, sourceroute,
  74     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_dosourceroute), 0,
  75     "Enable forwarding source routed IP packets");
  76 #define V_ip_dosourceroute      VNET(ip_dosourceroute)
  77
  78 VNET_DEFINE_STATIC(int, ip_acceptsourceroute);
  79 SYSCTL_INT(_net_inet_ip, IPCTL_ACCEPTSOURCEROUTE, accept_sourceroute,
  80     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(ip_acceptsourceroute), 0,
  81     "Enable accepting source routed IP packets");
  82 #define V_ip_acceptsourceroute  VNET(ip_acceptsourceroute)
  83
  84 VNET_DEFINE(int, ip_doopts) = 1; /* 0 = ignore, 1 = process, 2 = reject */
  85 SYSCTL_INT(_net_inet_ip, OID_AUTO, process_options, CTLFLAG_VNET | CTLFLAG_RW,
  86     &VNET_NAME(ip_doopts), 0, "Enable IP options processing ([LS]SRR, RR, TS)");
  87
  88 static void     save_rte(struct mbuf *m, u_char *, struct in_addr);
  89
  90 /*
  91  * Do option processing on a datagram, possibly discarding it if bad options
  92  * are encountered, or forwarding it if source-routed.
  93  *
  94  * The pass argument is used when operating in the IPSTEALTH mode to tell
  95  * what options to process: [LS]SRR (pass 0) or the others (pass 1).  The
  96  * reason for as many as two passes is that when doing IPSTEALTH, non-routing
  97  * options should be processed only if the packet is for us.
  98  *
  99  * Returns 1 if packet has been forwarded/freed, 0 if the packet should be
 100  * processed further.
 101  */
 102 int
 103 ip_dooptions(struct mbuf *m, int pass)
 104 {
 105         struct ip *ip = mtod(m, struct ip *);
 106         u_char *cp;
 107         struct in_ifaddr *ia;
 108         int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0;
 109         struct in_addr *sin, dst;
 110         uint32_t ntime;
 111         struct nhop_object *nh;
 112         struct  sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
 113
 114         NET_EPOCH_ASSERT();
 115
 116         /* Ignore or reject packets with IP options. */
 117         if (V_ip_doopts == 0)
 118                 return 0;
 119         else if (V_ip_doopts == 2) {
 120                 type = ICMP_UNREACH;
 121                 code = ICMP_UNREACH_FILTER_PROHIB;
 122                 goto bad;
 123         }
 124
 125         dst = ip->ip_dst;
 126         cp = (u_char *)(ip + 1);
 127         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 128         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 129                 opt = cp[IPOPT_OPTVAL];
 130                 if (opt == IPOPT_EOL)
 131                         break;
 132                 if (opt == IPOPT_NOP)
 133                         optlen = 1;
 134                 else {
 135                         if (cnt < IPOPT_OLEN + sizeof(*cp)) {
 136                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 137                                 goto bad;
 138                         }
 139                         optlen = cp[IPOPT_OLEN];
 140                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt) {
 141                                 code = &cp[IPOPT_OLEN] - (u_char *)ip;
 142                                 goto bad;
 143                         }
 144                 }
 145                 switch (opt) {
 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                                         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                                 nh = fib4_lookup(M_GETFIB(m), ipaddr.sin_addr,
 258                                      0, NHR_NONE, 0);
 259                                 if (nh == NULL)
 260                                         goto bad;
 261
 262                                 memcpy(cp + off, &(IA_SIN(nh->nh_ifa)->sin_addr),
 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 ((nh = fib4_lookup(M_GETFIB(m),
 304                             ipaddr.sin_addr, 0, NHR_NONE, 0)) != NULL) {
 305                                 memcpy(cp + off, &(IA_SIN(nh->nh_ifa)->sin_addr),
 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                         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         if (forward && V_ipforwarding) {
 384                 ip_forward(m, 1);
 385                 return (1);
 386         }
 387         return (0);
 388 bad:
 389         icmp_error(m, type, code, 0, 0);
 390         IPSTAT_INC(ips_badoptions);
 391         return (1);
 392 }
 393
 394 /*
 395  * Save incoming source route for use in replies, to be picked up later by
 396  * ip_srcroute if the receiver is interested.
 397  */
 398 static void
 399 save_rte(struct mbuf *m, u_char *option, struct in_addr dst)
 400 {
 401         unsigned olen;
 402         struct ipopt_tag *opts;
 403
 404         opts = (struct ipopt_tag *)m_tag_get(PACKET_TAG_IPOPTIONS,
 405             sizeof(struct ipopt_tag), M_NOWAIT);
 406         if (opts == NULL)
 407                 return;
 408
 409         olen = option[IPOPT_OLEN];
 410         if (olen > sizeof(opts->ip_srcrt) - (1 + sizeof(dst))) {
 411                 m_tag_free((struct m_tag *)opts);
 412                 return;
 413         }
 414         bcopy(option, opts->ip_srcrt.srcopt, olen);
 415         opts->ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
 416         opts->ip_srcrt.dst = dst;
 417         m_tag_prepend(m, (struct m_tag *)opts);
 418 }
 419
 420 /*
 421  * Retrieve incoming source route for use in replies, in the same form used
 422  * by setsockopt.  The first hop is placed before the options, will be
 423  * removed later.
 424  */
 425 struct mbuf *
 426 ip_srcroute(struct mbuf *m0)
 427 {
 428         struct in_addr *p, *q;
 429         struct mbuf *m;
 430         struct ipopt_tag *opts;
 431
 432         opts = (struct ipopt_tag *)m_tag_find(m0, PACKET_TAG_IPOPTIONS, NULL);
 433         if (opts == NULL)
 434                 return (NULL);
 435
 436         if (opts->ip_nhops == 0)
 437                 return (NULL);
 438         m = m_get(M_NOWAIT, MT_DATA);
 439         if (m == NULL)
 440                 return (NULL);
 441
 442 #define OPTSIZ  (sizeof(opts->ip_srcrt.nop) + sizeof(opts->ip_srcrt.srcopt))
 443
 444         /* length is (nhops+1)*sizeof(addr) + sizeof(nop + srcrt header) */
 445         m->m_len = opts->ip_nhops * sizeof(struct in_addr) +
 446             sizeof(struct in_addr) + OPTSIZ;
 447
 448         /*
 449          * First, save first hop for return route.
 450          */
 451         p = &(opts->ip_srcrt.route[opts->ip_nhops - 1]);
 452         *(mtod(m, struct in_addr *)) = *p--;
 453
 454         /*
 455          * Copy option fields and padding (nop) to mbuf.
 456          */
 457         opts->ip_srcrt.nop = IPOPT_NOP;
 458         opts->ip_srcrt.srcopt[IPOPT_OFFSET] = IPOPT_MINOFF;
 459         (void)memcpy(mtod(m, caddr_t) + sizeof(struct in_addr),
 460             &(opts->ip_srcrt.nop), OPTSIZ);
 461         q = (struct in_addr *)(mtod(m, caddr_t) +
 462             sizeof(struct in_addr) + OPTSIZ);
 463 #undef OPTSIZ
 464         /*
 465          * Record return path as an IP source route, reversing the path
 466          * (pointers are now aligned).
 467          */
 468         while (p >= opts->ip_srcrt.route) {
 469                 *q++ = *p--;
 470         }
 471         /*
 472          * Last hop goes to final destination.
 473          */
 474         *q = opts->ip_srcrt.dst;
 475         m_tag_delete(m0, (struct m_tag *)opts);
 476         return (m);
 477 }
 478
 479 /*
 480  * Strip out IP options, at higher level protocol in the kernel.
 481  */
 482 void
 483 ip_stripoptions(struct mbuf *m)
 484 {
 485         struct ip *ip = mtod(m, struct ip *);
 486         int olen;
 487
 488         olen = (ip->ip_hl << 2) - sizeof(struct ip);
 489         m->m_len -= olen;
 490         if (m->m_flags & M_PKTHDR)
 491                 m->m_pkthdr.len -= olen;
 492         ip->ip_len = htons(ntohs(ip->ip_len) - olen);
 493         ip->ip_hl = sizeof(struct ip) >> 2;
 494
 495         bcopy((char *)ip + sizeof(struct ip) + olen, (ip + 1),
 496             (size_t )(m->m_len - sizeof(struct ip)));
 497 }
 498
 499 /*
 500  * Insert IP options into preformed packet.  Adjust IP destination as
 501  * required for IP source routing, as indicated by a non-zero in_addr at the
 502  * start of the options.
 503  *
 504  * XXX This routine assumes that the packet has no options in place.
 505  */
 506 struct mbuf *
 507 ip_insertoptions(struct mbuf *m, struct mbuf *opt, int *phlen)
 508 {
 509         struct ipoption *p = mtod(opt, struct ipoption *);
 510         struct mbuf *n;
 511         struct ip *ip = mtod(m, struct ip *);
 512         unsigned optlen;
 513
 514         optlen = opt->m_len - sizeof(p->ipopt_dst);
 515         if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET) {
 516                 *phlen = 0;
 517                 return (m);             /* XXX should fail */
 518         }
 519         if (p->ipopt_dst.s_addr)
 520                 ip->ip_dst = p->ipopt_dst;
 521         if (!M_WRITABLE(m) || M_LEADINGSPACE(m) < optlen) {
 522                 n = m_gethdr(M_NOWAIT, MT_DATA);
 523                 if (n == NULL) {
 524                         *phlen = 0;
 525                         return (m);
 526                 }
 527                 m_move_pkthdr(n, m);
 528                 n->m_pkthdr.rcvif = NULL;
 529                 n->m_pkthdr.len += optlen;
 530                 m->m_len -= sizeof(struct ip);
 531                 m->m_data += sizeof(struct ip);
 532                 n->m_next = m;
 533                 m = n;
 534                 m->m_len = optlen + sizeof(struct ip);
 535                 m->m_data += max_linkhdr;
 536                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 537         } else {
 538                 m->m_data -= optlen;
 539                 m->m_len += optlen;
 540                 m->m_pkthdr.len += optlen;
 541                 bcopy(ip, mtod(m, void *), sizeof(struct ip));
 542         }
 543         ip = mtod(m, struct ip *);
 544         bcopy(p->ipopt_list, ip + 1, optlen);
 545         *phlen = sizeof(struct ip) + optlen;
 546         ip->ip_v = IPVERSION;
 547         ip->ip_hl = *phlen >> 2;
 548         ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
 549         return (m);
 550 }
 551
 552 /*
 553  * Copy options from ip to jp, omitting those not copied during
 554  * fragmentation.
 555  */
 556 int
 557 ip_optcopy(struct ip *ip, struct ip *jp)
 558 {
 559         u_char *cp, *dp;
 560         int opt, optlen, cnt;
 561
 562         cp = (u_char *)(ip + 1);
 563         dp = (u_char *)(jp + 1);
 564         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 565         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 566                 opt = cp[0];
 567                 if (opt == IPOPT_EOL)
 568                         break;
 569                 if (opt == IPOPT_NOP) {
 570                         /* Preserve for IP mcast tunnel's LSRR alignment. */
 571                         *dp++ = IPOPT_NOP;
 572                         optlen = 1;
 573                         continue;
 574                 }
 575
 576                 KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp),
 577                     ("ip_optcopy: malformed ipv4 option"));
 578                 optlen = cp[IPOPT_OLEN];
 579                 KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen <= cnt,
 580                     ("ip_optcopy: malformed ipv4 option"));
 581
 582                 /* Bogus lengths should have been caught by ip_dooptions. */
 583                 if (optlen > cnt)
 584                         optlen = cnt;
 585                 if (IPOPT_COPIED(opt)) {
 586                         bcopy(cp, dp, optlen);
 587                         dp += optlen;
 588                 }
 589         }
 590         for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
 591                 *dp++ = IPOPT_EOL;
 592         return (optlen);
 593 }
 594
 595 /*
 596  * Set up IP options in pcb for insertion in output packets.  Store in mbuf
 597  * with pointer in pcbopt, adding pseudo-option with destination address if
 598  * source routed.
 599  */
 600 int
 601 ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)
 602 {
 603         int cnt, optlen;
 604         u_char *cp;
 605         struct mbuf **pcbopt;
 606         u_char opt;
 607
 608         INP_WLOCK_ASSERT(inp);
 609
 610         pcbopt = &inp->inp_options;
 611
 612         /* turn off any old options */
 613         if (*pcbopt)
 614                 (void)m_free(*pcbopt);
 615         *pcbopt = NULL;
 616         if (m == NULL || m->m_len == 0) {
 617                 /*
 618                  * Only turning off any previous options.
 619                  */
 620                 if (m != NULL)
 621                         (void)m_free(m);
 622                 return (0);
 623         }
 624
 625         if (m->m_len % sizeof(int32_t))
 626                 goto bad;
 627         /*
 628          * IP first-hop destination address will be stored before actual
 629          * options; move other options back and clear it when none present.
 630          */
 631         if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
 632                 goto bad;
 633         cnt = m->m_len;
 634         m->m_len += sizeof(struct in_addr);
 635         cp = mtod(m, u_char *) + sizeof(struct in_addr);
 636         bcopy(mtod(m, void *), cp, (unsigned)cnt);
 637         bzero(mtod(m, void *), sizeof(struct in_addr));
 638
 639         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 640                 opt = cp[IPOPT_OPTVAL];
 641                 if (opt == IPOPT_EOL)
 642                         break;
 643                 if (opt == IPOPT_NOP)
 644                         optlen = 1;
 645                 else {
 646                         if (cnt < IPOPT_OLEN + sizeof(*cp))
 647                                 goto bad;
 648                         optlen = cp[IPOPT_OLEN];
 649                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
 650                                 goto bad;
 651                 }
 652                 switch (opt) {
 653                 default:
 654                         break;
 655
 656                 case IPOPT_LSRR:
 657                 case IPOPT_SSRR:
 658                         /*
 659                          * User process specifies route as:
 660                          *
 661                          *      ->A->B->C->D
 662                          *
 663                          * D must be our final destination (but we can't
 664                          * check that since we may not have connected yet).
 665                          * A is first hop destination, which doesn't appear
 666                          * in actual IP option, but is stored before the
 667                          * options.
 668                          */
 669                         /* XXX-BZ PRIV_NETINET_SETHDROPTS? */
 670                         if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
 671                                 goto bad;
 672                         m->m_len -= sizeof(struct in_addr);
 673                         cnt -= sizeof(struct in_addr);
 674                         optlen -= sizeof(struct in_addr);
 675                         cp[IPOPT_OLEN] = optlen;
 676                         /*
 677                          * Move first hop before start of options.
 678                          */
 679                         bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
 680                             sizeof(struct in_addr));
 681                         /*
 682                          * Then copy rest of options back
 683                          * to close up the deleted entry.
 684                          */
 685                         bcopy((&cp[IPOPT_OFFSET+1] + sizeof(struct in_addr)),
 686                             &cp[IPOPT_OFFSET+1],
 687                             (unsigned)cnt - (IPOPT_MINOFF - 1));
 688                         break;
 689                 }
 690         }
 691         if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
 692                 goto bad;
 693         *pcbopt = m;
 694         return (0);
 695
 696 bad:
 697         (void)m_free(m);
 698         return (EINVAL);
 699 }
 700
 701 /*
 702  * Check for the presence of the IP Router Alert option [RFC2113]
 703  * in the header of an IPv4 datagram.
 704  *
 705  * This call is not intended for use from the forwarding path; it is here
 706  * so that protocol domains may check for the presence of the option.
 707  * Given how FreeBSD's IPv4 stack is currently structured, the Router Alert
 708  * option does not have much relevance to the implementation, though this
 709  * may change in future.
 710  * Router alert options SHOULD be passed if running in IPSTEALTH mode and
 711  * we are not the endpoint.
 712  * Length checks on individual options should already have been performed
 713  * by ip_dooptions() therefore they are folded under INVARIANTS here.
 714  *
 715  * Return zero if not present or options are invalid, non-zero if present.
 716  */
 717 int
 718 ip_checkrouteralert(struct mbuf *m)
 719 {
 720         struct ip *ip = mtod(m, struct ip *);
 721         u_char *cp;
 722         int opt, optlen, cnt, found_ra;
 723
 724         found_ra = 0;
 725         cp = (u_char *)(ip + 1);
 726         cnt = (ip->ip_hl << 2) - sizeof (struct ip);
 727         for (; cnt > 0; cnt -= optlen, cp += optlen) {
 728                 opt = cp[IPOPT_OPTVAL];
 729                 if (opt == IPOPT_EOL)
 730                         break;
 731                 if (opt == IPOPT_NOP)
 732                         optlen = 1;
 733                 else {
 734 #ifdef INVARIANTS
 735                         if (cnt < IPOPT_OLEN + sizeof(*cp))
 736                                 break;
 737 #endif
 738                         optlen = cp[IPOPT_OLEN];
 739 #ifdef INVARIANTS
 740                         if (optlen < IPOPT_OLEN + sizeof(*cp) || optlen > cnt)
 741                                 break;
 742 #endif
 743                 }
 744                 switch (opt) {
 745                 case IPOPT_RA:
 746 #ifdef INVARIANTS
 747                         if (optlen != IPOPT_OFFSET + sizeof(uint16_t) ||
 748                             (*((uint16_t *)&cp[IPOPT_OFFSET]) != 0))
 749                             break;
 750                         else
 751 #endif
 752                         found_ra = 1;
 753                         break;
 754                 default:
 755                         break;
 756                 }
 757         }
 758
 759         return (found_ra);
 760 }