sys/netinet6/in6_src.c

   1 /*      $FreeBSD: src/sys/netinet6/in6_src.c,v 1.1.2.3 2002/02/26 18:02:06 ume Exp $    */
   2 /*      $DragonFly: src/sys/netinet6/in6_src.c,v 1.13 2006/12/29 18:02:56 victor Exp $  */
   3 /*      $KAME: in6_src.c,v 1.37 2001/03/29 05:34:31 itojun Exp $        */
   4
   5 /*
   6  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
   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 project 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 PROJECT 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 PROJECT 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 /*
  35  * Copyright (c) 1982, 1986, 1991, 1993
  36  *      The Regents of the University of California.  All rights reserved.
  37  *
  38  * Redistribution and use in source and binary forms, with or without
  39  * modification, are permitted provided that the following conditions
  40  * are met:
  41  * 1. Redistributions of source code must retain the above copyright
  42  *    notice, this list of conditions and the following disclaimer.
  43  * 2. Redistributions in binary form must reproduce the above copyright
  44  *    notice, this list of conditions and the following disclaimer in the
  45  *    documentation and/or other materials provided with the distribution.
  46  * 3. All advertising materials mentioning features or use of this software
  47  *    must display the following acknowledgement:
  48  *      This product includes software developed by the University of
  49  *      California, Berkeley and its contributors.
  50  * 4. Neither the name of the University nor the names of its contributors
  51  *    may be used to endorse or promote products derived from this software
  52  *    without specific prior written permission.
  53  *
  54  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  55  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  56  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  57  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  58  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  59  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  60  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  61  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  62  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  63  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  64  * SUCH DAMAGE.
  65  *
  66  *      @(#)in_pcb.c    8.2 (Berkeley) 1/4/94
  67  */
  68
  69 #include "opt_inet.h"
  70 #include "opt_inet6.h"
  71
  72 #include <sys/param.h>
  73 #include <sys/systm.h>
  74 #include <sys/jail.h>
  75 #include <sys/malloc.h>
  76 #include <sys/mbuf.h>
  77 #include <sys/protosw.h>
  78 #include <sys/socket.h>
  79 #include <sys/socketvar.h>
  80 #include <sys/errno.h>
  81 #include <sys/time.h>
  82 #include <sys/proc.h>
  83
  84 #include <net/if.h>
  85 #include <net/route.h>
  86
  87 #include <netinet/in.h>
  88 #include <netinet/in_var.h>
  89 #include <netinet/in_systm.h>
  90 #include <netinet/ip.h>
  91 #include <netinet/in_pcb.h>
  92 #include <netinet6/in6_var.h>
  93 #include <netinet/ip6.h>
  94 #include <netinet6/in6_pcb.h>
  95 #include <netinet6/ip6_var.h>
  96 #include <netinet6/nd6.h>
  97 #ifdef ENABLE_DEFAULT_SCOPE
  98 #include <netinet6/scope6_var.h>
  99 #endif
 100
 101 #include <net/net_osdep.h>
 102
 103 #include "use_loop.h"
 104
 105 /*
 106  * Return an IPv6 address, which is the most appropriate for a given
 107  * destination and user specified options.
 108  * If necessary, this function lookups the routing table and returns
 109  * an entry to the caller for later use.
 110  */
 111 struct in6_addr *
 112 in6_selectsrc(struct sockaddr_in6 *dstsock, struct ip6_pktopts *opts,
 113               struct ip6_moptions *mopts, struct route_in6 *ro,
 114               struct in6_addr *laddr, int *errorp, struct thread *td)
 115 {
 116         struct sockaddr_in6 jsin6;
 117         struct ucred *cred = NULL;
 118         struct in6_addr *dst;
 119         struct in6_ifaddr *ia6 = 0;
 120         struct in6_pktinfo *pi = NULL;
 121         int jailed = 0;
 122
 123         if (td && td->td_proc && td->td_proc->p_ucred)
 124                 cred = td->td_proc->p_ucred;
 125         if (cred && cred->cr_prison)
 126                 jailed = 1;
 127         jsin6.sin6_family = AF_INET6;
 128         dst = &dstsock->sin6_addr;
 129         *errorp = 0;
 130
 131         /*
 132          * If the source address is explicitly specified by the caller,
 133          * use it.
 134          */
 135         if (opts && (pi = opts->ip6po_pktinfo) &&
 136             !IN6_IS_ADDR_UNSPECIFIED(&pi->ipi6_addr)) {
 137                 jsin6.sin6_addr = pi->ipi6_addr;
 138                 if (jailed && !jailed_ip(cred->cr_prison,
 139                     (struct sockaddr *)&jsin6)) {
 140                         return(0);
 141                 } else {
 142                         return (&pi->ipi6_addr);
 143                 }
 144         }
 145
 146         /*
 147          * If the source address is not specified but the socket(if any)
 148          * is already bound, use the bound address.
 149          */
 150         if (laddr && !IN6_IS_ADDR_UNSPECIFIED(laddr)) {
 151                 jsin6.sin6_addr = *laddr;
 152                 if (jailed && !jailed_ip(cred->cr_prison,
 153                     (struct sockaddr *)&jsin6)) {
 154                         return(0);
 155                 } else {
 156                         return (laddr);
 157                 }
 158         }
 159
 160         /*
 161          * If the caller doesn't specify the source address but
 162          * the outgoing interface, use an address associated with
 163          * the interface.
 164          */
 165         if (pi && pi->ipi6_ifindex) {
 166                 /* XXX boundary check is assumed to be already done. */
 167                 ia6 = in6_ifawithscope(ifindex2ifnet[pi->ipi6_ifindex],
 168                                        dst);
 169
 170                 if (ia6 && jailed) {
 171                         jsin6.sin6_addr = (&ia6->ia_addr)->sin6_addr;
 172                         if (!jailed_ip(cred->cr_prison,
 173                                 (struct sockaddr *)&jsin6))
 174                                 ia6 = 0;
 175                 }
 176
 177                 if (ia6 == 0) {
 178                         *errorp = EADDRNOTAVAIL;
 179                         return (0);
 180                 }
 181                 return (&satosin6(&ia6->ia_addr)->sin6_addr);
 182         }
 183
 184         /*
 185          * If the destination address is a link-local unicast address or
 186          * a multicast address, and if the outgoing interface is specified
 187          * by the sin6_scope_id filed, use an address associated with the
 188          * interface.
 189          * XXX: We're now trying to define more specific semantics of
 190          *      sin6_scope_id field, so this part will be rewritten in
 191          *      the near future.
 192          */
 193         if ((IN6_IS_ADDR_LINKLOCAL(dst) || IN6_IS_ADDR_MULTICAST(dst)) &&
 194             dstsock->sin6_scope_id) {
 195                 /*
 196                  * I'm not sure if boundary check for scope_id is done
 197                  * somewhere...
 198                  */
 199                 if (dstsock->sin6_scope_id < 0 ||
 200                     if_index < dstsock->sin6_scope_id) {
 201                         *errorp = ENXIO; /* XXX: better error? */
 202                         return (0);
 203                 }
 204                 ia6 = in6_ifawithscope(ifindex2ifnet[dstsock->sin6_scope_id],
 205                                        dst);
 206
 207                 if (ia6 && jailed) {
 208                         jsin6.sin6_addr = (&ia6->ia_addr)->sin6_addr;
 209                         if (!jailed_ip(cred->cr_prison,
 210                                 (struct sockaddr *)&jsin6))
 211                                 ia6 = 0;
 212                 }
 213
 214                 if (ia6 == 0) {
 215                         *errorp = EADDRNOTAVAIL;
 216                         return (0);
 217                 }
 218                 return (&satosin6(&ia6->ia_addr)->sin6_addr);
 219         }
 220
 221         /*
 222          * If the destination address is a multicast address and
 223          * the outgoing interface for the address is specified
 224          * by the caller, use an address associated with the interface.
 225          * There is a sanity check here; if the destination has node-local
 226          * scope, the outgoing interfacde should be a loopback address.
 227          * Even if the outgoing interface is not specified, we also
 228          * choose a loopback interface as the outgoing interface.
 229          */
 230         if (!jailed && IN6_IS_ADDR_MULTICAST(dst)) {
 231                 struct ifnet *ifp = mopts ? mopts->im6o_multicast_ifp : NULL;
 232
 233                 if (ifp == NULL && IN6_IS_ADDR_MC_NODELOCAL(dst)) {
 234                         ifp = &loif[0];
 235                 }
 236
 237                 if (ifp) {
 238                         ia6 = in6_ifawithscope(ifp, dst);
 239                         if (ia6 == 0) {
 240                                 *errorp = EADDRNOTAVAIL;
 241                                 return (0);
 242                         }
 243                         return (&satosin6(&ia6->ia_addr)->sin6_addr);
 244                 }
 245         }
 246
 247         /*
 248          * If the next hop address for the packet is specified
 249          * by caller, use an address associated with the route
 250          * to the next hop.
 251          */
 252         {
 253                 struct sockaddr_in6 *sin6_next;
 254                 struct rtentry *rt;
 255
 256                 if (opts && opts->ip6po_nexthop) {
 257                         sin6_next = satosin6(opts->ip6po_nexthop);
 258                         rt = nd6_lookup(&sin6_next->sin6_addr, 1, NULL);
 259                         if (rt) {
 260                                 ia6 = in6_ifawithscope(rt->rt_ifp, dst);
 261                                 if (ia6 == 0)
 262                                         ia6 = ifatoia6(rt->rt_ifa);
 263                         }
 264                         if (ia6 && jailed) {
 265                                 jsin6.sin6_addr = (&ia6->ia_addr)->sin6_addr;
 266                                 if (!jailed_ip(cred->cr_prison,
 267                                         (struct sockaddr *)&jsin6))
 268                                         ia6 = 0;
 269                         }
 270
 271                         if (ia6 == 0) {
 272                                 *errorp = EADDRNOTAVAIL;
 273                                 return (0);
 274                         }
 275                         return (&satosin6(&ia6->ia_addr)->sin6_addr);
 276                 }
 277         }
 278
 279         /*
 280          * If route is known or can be allocated now,
 281          * our src addr is taken from the i/f, else punt.
 282          */
 283         if (ro) {
 284                 if (ro->ro_rt &&
 285                     (!(ro->ro_rt->rt_flags & RTF_UP) ||
 286                      satosin6(&ro->ro_dst)->sin6_family != AF_INET6 ||
 287                      !IN6_ARE_ADDR_EQUAL(&satosin6(&ro->ro_dst)->sin6_addr,
 288                                          dst))) {
 289                         RTFREE(ro->ro_rt);
 290                         ro->ro_rt = NULL;
 291                 }
 292                 if (ro->ro_rt == NULL || ro->ro_rt->rt_ifp == NULL) {
 293                         struct sockaddr_in6 *sa6;
 294
 295                         /* No route yet, so try to acquire one */
 296                         bzero(&ro->ro_dst, sizeof(struct sockaddr_in6));
 297                         sa6 = &ro->ro_dst;
 298                         sa6->sin6_family = AF_INET6;
 299                         sa6->sin6_len = sizeof(struct sockaddr_in6);
 300                         sa6->sin6_addr = *dst;
 301                         sa6->sin6_scope_id = dstsock->sin6_scope_id;
 302                         if (!jailed && IN6_IS_ADDR_MULTICAST(dst)) {
 303                                 ro->ro_rt =
 304                                   rtpurelookup((struct sockaddr *)&ro->ro_dst);
 305                         } else {
 306                                 rtalloc((struct route *)ro);
 307                         }
 308                 }
 309
 310                 /*
 311                  * in_pcbconnect() checks out IFF_LOOPBACK to skip using
 312                  * the address. But we don't know why it does so.
 313                  * It is necessary to ensure the scope even for lo0
 314                  * so doesn't check out IFF_LOOPBACK.
 315                  */
 316
 317                 if (ro->ro_rt) {
 318                         ia6 = in6_ifawithscope(ro->ro_rt->rt_ifa->ifa_ifp, dst);
 319                         if (ia6 && jailed) {
 320                                 jsin6.sin6_addr = (&ia6->ia_addr)->sin6_addr;
 321                                 if (!jailed_ip(cred->cr_prison,
 322                                         (struct sockaddr *)&jsin6))
 323                                         ia6 = 0;
 324                         }
 325
 326                         if (ia6 == 0) /* xxx scope error ?*/
 327                                 ia6 = ifatoia6(ro->ro_rt->rt_ifa);
 328
 329                         if (ia6 && jailed) {
 330                                 jsin6.sin6_addr = (&ia6->ia_addr)->sin6_addr;
 331                                 if (!jailed_ip(cred->cr_prison,
 332                                         (struct sockaddr *)&jsin6))
 333                                         ia6 = 0;
 334                         }
 335                 }
 336 #if 0
 337                 /*
 338                  * xxx The followings are necessary? (kazu)
 339                  * I don't think so.
 340                  * It's for SO_DONTROUTE option in IPv4.(jinmei)
 341                  */
 342                 if (ia6 == 0) {
 343                         struct sockaddr_in6 sin6 = {sizeof(sin6), AF_INET6, 0};
 344
 345                         sin6->sin6_addr = *dst;
 346
 347                         ia6 = ifatoia6(ifa_ifwithdstaddr(sin6tosa(&sin6)));
 348                         if (ia6 == 0)
 349                                 ia6 = ifatoia6(ifa_ifwithnet(sin6tosa(&sin6)));
 350                         if (ia6 == 0)
 351                                 return (0);
 352                         return (&satosin6(&ia6->ia_addr)->sin6_addr);
 353                 }
 354 #endif /* 0 */
 355                 if (ia6 == 0) {
 356                         *errorp = EHOSTUNREACH; /* no route */
 357                         return (0);
 358                 }
 359                 return (&satosin6(&ia6->ia_addr)->sin6_addr);
 360         }
 361
 362         *errorp = EADDRNOTAVAIL;
 363         return (0);
 364 }
 365
 366 /*
 367  * Default hop limit selection. The precedence is as follows:
 368  * 1. Hoplimit value specified via ioctl.
 369  * 2. (If the outgoing interface is detected) the current
 370  *     hop limit of the interface specified by router advertisement.
 371  * 3. The system default hoplimit.
 372 */
 373 int
 374 in6_selecthlim(struct in6pcb *in6p, struct ifnet *ifp)
 375 {
 376         if (in6p && in6p->in6p_hops >= 0)
 377                 return (in6p->in6p_hops);
 378         else if (ifp)
 379                 return (ND_IFINFO(ifp)->chlim);
 380         else
 381                 return (ip6_defhlim);
 382 }
 383
 384 /*
 385  * XXX: this is borrowed from in6_pcbbind(). If possible, we should
 386  * share this function by all *bsd*...
 387  */
 388 int
 389 in6_pcbsetport(struct in6_addr *laddr, struct inpcb *inp, struct thread *td)
 390 {
 391         struct socket *so = inp->inp_socket;
 392         u_int16_t lport = 0, first, last, *lastport;
 393         int count, error = 0, wild = 0;
 394         struct inpcbinfo *pcbinfo = inp->inp_pcbinfo;
 395         struct ucred *cred = NULL;
 396
 397         /* XXX: this is redundant when called from in6_pcbbind */
 398         if ((so->so_options & (SO_REUSEADDR|SO_REUSEPORT)) == 0)
 399                 wild = INPLOOKUP_WILDCARD;
 400         if (td->td_proc && td->td_proc->p_ucred)
 401                 cred = td->td_proc->p_ucred;
 402
 403         inp->inp_flags |= INP_ANONPORT;
 404
 405         if (inp->inp_flags & INP_HIGHPORT) {
 406                 first = ipport_hifirstauto;     /* sysctl */
 407                 last  = ipport_hilastauto;
 408                 lastport = &pcbinfo->lasthi;
 409         } else if (inp->inp_flags & INP_LOWPORT) {
 410                 if ((error = suser(td)) != 0)
 411                         return error;
 412                 first = ipport_lowfirstauto;    /* 1023 */
 413                 last  = ipport_lowlastauto;     /* 600 */
 414                 lastport = &pcbinfo->lastlow;
 415         } else {
 416                 first = ipport_firstauto;       /* sysctl */
 417                 last  = ipport_lastauto;
 418                 lastport = &pcbinfo->lastport;
 419         }
 420         /*
 421          * Simple check to ensure all ports are not used up causing
 422          * a deadlock here.
 423          *
 424          * We split the two cases (up and down) so that the direction
 425          * is not being tested on each round of the loop.
 426          */
 427         if (first > last) {
 428                 /*
 429                  * counting down
 430                  */
 431                 count = first - last;
 432
 433                 do {
 434                         if (count-- < 0) {      /* completely used? */
 435                                 /*
 436                                  * Undo any address bind that may have
 437                                  * occurred above.
 438                                  */
 439                                 inp->in6p_laddr = kin6addr_any;
 440                                 return (EAGAIN);
 441                         }
 442                         --*lastport;
 443                         if (*lastport > first || *lastport < last)
 444                                 *lastport = first;
 445                         lport = htons(*lastport);
 446                 } while (in6_pcblookup_local(pcbinfo, &inp->in6p_laddr,
 447                          lport, wild, cred));
 448         } else {
 449                 /*
 450                  * counting up
 451                  */
 452                 count = last - first;
 453
 454                 do {
 455                         if (count-- < 0) {      /* completely used? */
 456                                 /*
 457                                  * Undo any address bind that may have
 458                                  * occurred above.
 459                                  */
 460                                 inp->in6p_laddr = kin6addr_any;
 461                                 return (EAGAIN);
 462                         }
 463                         ++*lastport;
 464                         if (*lastport < first || *lastport > last)
 465                                 *lastport = first;
 466                         lport = htons(*lastport);
 467                 } while (in6_pcblookup_local(pcbinfo, &inp->in6p_laddr,
 468                          lport, wild, cred));
 469         }
 470
 471         inp->inp_lport = lport;
 472         if (in_pcbinsporthash(inp) != 0) {
 473                 inp->in6p_laddr = kin6addr_any;
 474                 inp->inp_lport = 0;
 475                 return (EAGAIN);
 476         }
 477
 478         return (0);
 479 }
 480
 481 /*
 482  * generate kernel-internal form (scopeid embedded into s6_addr16[1]).
 483  * If the address scope of is link-local, embed the interface index in the
 484  * address.  The routine determines our precedence
 485  * between advanced API scope/interface specification and basic API
 486  * specification.
 487  *
 488  * this function should be nuked in the future, when we get rid of
 489  * embedded scopeid thing.
 490  *
 491  * XXX actually, it is over-specification to return ifp against sin6_scope_id.
 492  * there can be multiple interfaces that belong to a particular scope zone
 493  * (in specification, we have 1:N mapping between a scope zone and interfaces).
 494  * we may want to change the function to return something other than ifp.
 495  */
 496 int
 497 in6_embedscope(struct in6_addr *in6,
 498                const struct sockaddr_in6 *sin6,
 499 #ifdef HAVE_NRL_INPCB
 500                struct inpcb *in6p,
 501 #define in6p_outputopts inp_outputopts6
 502 #define in6p_moptions   inp_moptions6
 503 #else
 504                struct in6pcb *in6p,
 505 #endif
 506                struct ifnet **ifpp)
 507 {
 508         struct ifnet *ifp = NULL;
 509         u_int32_t scopeid;
 510
 511         *in6 = sin6->sin6_addr;
 512         scopeid = sin6->sin6_scope_id;
 513         if (ifpp)
 514                 *ifpp = NULL;
 515
 516         /*
 517          * don't try to read sin6->sin6_addr beyond here, since the caller may
 518          * ask us to overwrite existing sockaddr_in6
 519          */
 520
 521 #ifdef ENABLE_DEFAULT_SCOPE
 522         if (scopeid == 0)
 523                 scopeid = scope6_addr2default(in6);
 524 #endif
 525
 526         if (IN6_IS_SCOPE_LINKLOCAL(in6)) {
 527                 struct in6_pktinfo *pi;
 528
 529                 /*
 530                  * KAME assumption: link id == interface id
 531                  */
 532
 533                 if (in6p && in6p->in6p_outputopts &&
 534                     (pi = in6p->in6p_outputopts->ip6po_pktinfo) &&
 535                     pi->ipi6_ifindex) {
 536                         ifp = ifindex2ifnet[pi->ipi6_ifindex];
 537                         in6->s6_addr16[1] = htons(pi->ipi6_ifindex);
 538                 } else if (in6p && IN6_IS_ADDR_MULTICAST(in6) &&
 539                            in6p->in6p_moptions &&
 540                            in6p->in6p_moptions->im6o_multicast_ifp) {
 541                         ifp = in6p->in6p_moptions->im6o_multicast_ifp;
 542                         in6->s6_addr16[1] = htons(ifp->if_index);
 543                 } else if (scopeid) {
 544                         /* boundary check */
 545                         if (scopeid < 0 || if_index < scopeid)
 546                                 return ENXIO;  /* XXX EINVAL? */
 547                         ifp = ifindex2ifnet[scopeid];
 548                         /*XXX assignment to 16bit from 32bit variable */
 549                         in6->s6_addr16[1] = htons(scopeid & 0xffff);
 550                 }
 551
 552                 if (ifpp)
 553                         *ifpp = ifp;
 554         }
 555
 556         return 0;
 557 }
 558 #ifdef HAVE_NRL_INPCB
 559 #undef in6p_outputopts
 560 #undef in6p_moptions
 561 #endif
 562
 563 /*
 564  * generate standard sockaddr_in6 from embedded form.
 565  * touches sin6_addr and sin6_scope_id only.
 566  *
 567  * this function should be nuked in the future, when we get rid of
 568  * embedded scopeid thing.
 569  */
 570 int
 571 in6_recoverscope(struct sockaddr_in6 *sin6, const struct in6_addr *in6,
 572                  struct ifnet *ifp)
 573 {
 574         u_int32_t scopeid;
 575
 576         sin6->sin6_addr = *in6;
 577
 578         /*
 579          * don't try to read *in6 beyond here, since the caller may
 580          * ask us to overwrite existing sockaddr_in6
 581          */
 582
 583         sin6->sin6_scope_id = 0;
 584         if (IN6_IS_SCOPE_LINKLOCAL(in6)) {
 585                 /*
 586                  * KAME assumption: link id == interface id
 587                  */
 588                 scopeid = ntohs(sin6->sin6_addr.s6_addr16[1]);
 589                 if (scopeid) {
 590                         /* sanity check */
 591                         if (scopeid < 0 || if_index < scopeid)
 592                                 return ENXIO;
 593                         if (ifp && ifp->if_index != scopeid)
 594                                 return ENXIO;
 595                         sin6->sin6_addr.s6_addr16[1] = 0;
 596                         sin6->sin6_scope_id = scopeid;
 597                 }
 598         }
 599
 600         return 0;
 601 }
 602
 603 /*
 604  * just clear the embedded scope identifer.
 605  * XXX: currently used for bsdi4 only as a supplement function.
 606  */
 607 void
 608 in6_clearscope(struct in6_addr *addr)
 609 {
 610         if (IN6_IS_SCOPE_LINKLOCAL(addr))
 611                 addr->s6_addr16[1] = 0;
 612 }