net/ipv4/ip_options.c

   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              The options processing module for ip.c
   7  *
   8  * Version:     $Id: ip_options.c,v 1.21 2001/09/01 00:31:50 davem Exp $
   9  *
  10  * Authors:     A.N.Kuznetsov
  11  *
  12  */
  13
  14 #include <linux/capability.h>
  15 #include <linux/module.h>
  16 #include <linux/types.h>
  17 #include <asm/uaccess.h>
  18 #include <linux/skbuff.h>
  19 #include <linux/ip.h>
  20 #include <linux/icmp.h>
  21 #include <linux/netdevice.h>
  22 #include <linux/rtnetlink.h>
  23 #include <net/sock.h>
  24 #include <net/ip.h>
  25 #include <net/icmp.h>
  26 #include <net/route.h>
  27 #include <net/cipso_ipv4.h>
  28
  29 /*
  30  * Write options to IP header, record destination address to
  31  * source route option, address of outgoing interface
  32  * (we should already know it, so that this  function is allowed be
  33  * called only after routing decision) and timestamp,
  34  * if we originate this datagram.
  35  *
  36  * daddr is real destination address, next hop is recorded in IP header.
  37  * saddr is address of outgoing interface.
  38  */
  39
  40 void ip_options_build(struct sk_buff * skb, struct ip_options * opt,
  41                             __be32 daddr, struct rtable *rt, int is_frag)
  42 {
  43         unsigned char *iph = skb_network_header(skb);
  44
  45         memcpy(&(IPCB(skb)->opt), opt, sizeof(struct ip_options));
  46         memcpy(iph+sizeof(struct iphdr), opt->__data, opt->optlen);
  47         opt = &(IPCB(skb)->opt);
  48         opt->is_data = 0;
  49
  50         if (opt->srr)
  51                 memcpy(iph+opt->srr+iph[opt->srr+1]-4, &daddr, 4);
  52
  53         if (!is_frag) {
  54                 if (opt->rr_needaddr)
  55                         ip_rt_get_source(iph+opt->rr+iph[opt->rr+2]-5, rt);
  56                 if (opt->ts_needaddr)
  57                         ip_rt_get_source(iph+opt->ts+iph[opt->ts+2]-9, rt);
  58                 if (opt->ts_needtime) {
  59                         struct timeval tv;
  60                         __be32 midtime;
  61                         do_gettimeofday(&tv);
  62                         midtime = htonl((tv.tv_sec % 86400) * 1000 + tv.tv_usec / 1000);
  63                         memcpy(iph+opt->ts+iph[opt->ts+2]-5, &midtime, 4);
  64                 }
  65                 return;
  66         }
  67         if (opt->rr) {
  68                 memset(iph+opt->rr, IPOPT_NOP, iph[opt->rr+1]);
  69                 opt->rr = 0;
  70                 opt->rr_needaddr = 0;
  71         }
  72         if (opt->ts) {
  73                 memset(iph+opt->ts, IPOPT_NOP, iph[opt->ts+1]);
  74                 opt->ts = 0;
  75                 opt->ts_needaddr = opt->ts_needtime = 0;
  76         }
  77 }
  78
  79 /*
  80  * Provided (sopt, skb) points to received options,
  81  * build in dopt compiled option set appropriate for answering.
  82  * i.e. invert SRR option, copy anothers,
  83  * and grab room in RR/TS options.
  84  *
  85  * NOTE: dopt cannot point to skb.
  86  */
  87
  88 int ip_options_echo(struct ip_options * dopt, struct sk_buff * skb)
  89 {
  90         struct ip_options *sopt;
  91         unsigned char *sptr, *dptr;
  92         int soffset, doffset;
  93         int     optlen;
  94         __be32  daddr;
  95
  96         memset(dopt, 0, sizeof(struct ip_options));
  97
  98         dopt->is_data = 1;
  99
 100         sopt = &(IPCB(skb)->opt);
 101
 102         if (sopt->optlen == 0) {
 103                 dopt->optlen = 0;
 104                 return 0;
 105         }
 106
 107         sptr = skb_network_header(skb);
 108         dptr = dopt->__data;
 109
 110         daddr = skb->rtable->rt_spec_dst;
 111
 112         if (sopt->rr) {
 113                 optlen  = sptr[sopt->rr+1];
 114                 soffset = sptr[sopt->rr+2];
 115                 dopt->rr = dopt->optlen + sizeof(struct iphdr);
 116                 memcpy(dptr, sptr+sopt->rr, optlen);
 117                 if (sopt->rr_needaddr && soffset <= optlen) {
 118                         if (soffset + 3 > optlen)
 119                                 return -EINVAL;
 120                         dptr[2] = soffset + 4;
 121                         dopt->rr_needaddr = 1;
 122                 }
 123                 dptr += optlen;
 124                 dopt->optlen += optlen;
 125         }
 126         if (sopt->ts) {
 127                 optlen = sptr[sopt->ts+1];
 128                 soffset = sptr[sopt->ts+2];
 129                 dopt->ts = dopt->optlen + sizeof(struct iphdr);
 130                 memcpy(dptr, sptr+sopt->ts, optlen);
 131                 if (soffset <= optlen) {
 132                         if (sopt->ts_needaddr) {
 133                                 if (soffset + 3 > optlen)
 134                                         return -EINVAL;
 135                                 dopt->ts_needaddr = 1;
 136                                 soffset += 4;
 137                         }
 138                         if (sopt->ts_needtime) {
 139                                 if (soffset + 3 > optlen)
 140                                         return -EINVAL;
 141                                 if ((dptr[3]&0xF) != IPOPT_TS_PRESPEC) {
 142                                         dopt->ts_needtime = 1;
 143                                         soffset += 4;
 144                                 } else {
 145                                         dopt->ts_needtime = 0;
 146
 147                                         if (soffset + 8 <= optlen) {
 148                                                 __be32 addr;
 149
 150                                                 memcpy(&addr, sptr+soffset-1, 4);
 151                                                 if (inet_addr_type(&init_net, addr) != RTN_LOCAL) {
 152                                                         dopt->ts_needtime = 1;
 153                                                         soffset += 8;
 154                                                 }
 155                                         }
 156                                 }
 157                         }
 158                         dptr[2] = soffset;
 159                 }
 160                 dptr += optlen;
 161                 dopt->optlen += optlen;
 162         }
 163         if (sopt->srr) {
 164                 unsigned char * start = sptr+sopt->srr;
 165                 __be32 faddr;
 166
 167                 optlen  = start[1];
 168                 soffset = start[2];
 169                 doffset = 0;
 170                 if (soffset > optlen)
 171                         soffset = optlen + 1;
 172                 soffset -= 4;
 173                 if (soffset > 3) {
 174                         memcpy(&faddr, &start[soffset-1], 4);
 175                         for (soffset-=4, doffset=4; soffset > 3; soffset-=4, doffset+=4)
 176                                 memcpy(&dptr[doffset-1], &start[soffset-1], 4);
 177                         /*
 178                          * RFC1812 requires to fix illegal source routes.
 179                          */
 180                         if (memcmp(&ip_hdr(skb)->saddr,
 181                                    &start[soffset + 3], 4) == 0)
 182                                 doffset -= 4;
 183                 }
 184                 if (doffset > 3) {
 185                         memcpy(&start[doffset-1], &daddr, 4);
 186                         dopt->faddr = faddr;
 187                         dptr[0] = start[0];
 188                         dptr[1] = doffset+3;
 189                         dptr[2] = 4;
 190                         dptr += doffset+3;
 191                         dopt->srr = dopt->optlen + sizeof(struct iphdr);
 192                         dopt->optlen += doffset+3;
 193                         dopt->is_strictroute = sopt->is_strictroute;
 194                 }
 195         }
 196         if (sopt->cipso) {
 197                 optlen  = sptr[sopt->cipso+1];
 198                 dopt->cipso = dopt->optlen+sizeof(struct iphdr);
 199                 memcpy(dptr, sptr+sopt->cipso, optlen);
 200                 dptr += optlen;
 201                 dopt->optlen += optlen;
 202         }
 203         while (dopt->optlen & 3) {
 204                 *dptr++ = IPOPT_END;
 205                 dopt->optlen++;
 206         }
 207         return 0;
 208 }
 209
 210 /*
 211  *      Options "fragmenting", just fill options not
 212  *      allowed in fragments with NOOPs.
 213  *      Simple and stupid 8), but the most efficient way.
 214  */
 215
 216 void ip_options_fragment(struct sk_buff * skb)
 217 {
 218         unsigned char *optptr = skb_network_header(skb) + sizeof(struct iphdr);
 219         struct ip_options * opt = &(IPCB(skb)->opt);
 220         int  l = opt->optlen;
 221         int  optlen;
 222
 223         while (l > 0) {
 224                 switch (*optptr) {
 225                 case IPOPT_END:
 226                         return;
 227                 case IPOPT_NOOP:
 228                         l--;
 229                         optptr++;
 230                         continue;
 231                 }
 232                 optlen = optptr[1];
 233                 if (optlen<2 || optlen>l)
 234                   return;
 235                 if (!IPOPT_COPIED(*optptr))
 236                         memset(optptr, IPOPT_NOOP, optlen);
 237                 l -= optlen;
 238                 optptr += optlen;
 239         }
 240         opt->ts = 0;
 241         opt->rr = 0;
 242         opt->rr_needaddr = 0;
 243         opt->ts_needaddr = 0;
 244         opt->ts_needtime = 0;
 245         return;
 246 }
 247
 248 /*
 249  * Verify options and fill pointers in struct options.
 250  * Caller should clear *opt, and set opt->data.
 251  * If opt == NULL, then skb->data should point to IP header.
 252  */
 253
 254 int ip_options_compile(struct ip_options * opt, struct sk_buff * skb)
 255 {
 256         int l;
 257         unsigned char * iph;
 258         unsigned char * optptr;
 259         int optlen;
 260         unsigned char * pp_ptr = NULL;
 261         struct rtable *rt = skb ? skb->rtable : NULL;
 262
 263         if (!opt) {
 264                 opt = &(IPCB(skb)->opt);
 265                 iph = skb_network_header(skb);
 266                 opt->optlen = ((struct iphdr *)iph)->ihl*4 - sizeof(struct iphdr);
 267                 optptr = iph + sizeof(struct iphdr);
 268                 opt->is_data = 0;
 269         } else {
 270                 optptr = opt->is_data ? opt->__data :
 271                                         (unsigned char *)&(ip_hdr(skb)[1]);
 272                 iph = optptr - sizeof(struct iphdr);
 273         }
 274
 275         for (l = opt->optlen; l > 0; ) {
 276                 switch (*optptr) {
 277                       case IPOPT_END:
 278                         for (optptr++, l--; l>0; optptr++, l--) {
 279                                 if (*optptr != IPOPT_END) {
 280                                         *optptr = IPOPT_END;
 281                                         opt->is_changed = 1;
 282                                 }
 283                         }
 284                         goto eol;
 285                       case IPOPT_NOOP:
 286                         l--;
 287                         optptr++;
 288                         continue;
 289                 }
 290                 optlen = optptr[1];
 291                 if (optlen<2 || optlen>l) {
 292                         pp_ptr = optptr;
 293                         goto error;
 294                 }
 295                 switch (*optptr) {
 296                       case IPOPT_SSRR:
 297                       case IPOPT_LSRR:
 298                         if (optlen < 3) {
 299                                 pp_ptr = optptr + 1;
 300                                 goto error;
 301                         }
 302                         if (optptr[2] < 4) {
 303                                 pp_ptr = optptr + 2;
 304                                 goto error;
 305                         }
 306                         /* NB: cf RFC-1812 5.2.4.1 */
 307                         if (opt->srr) {
 308                                 pp_ptr = optptr;
 309                                 goto error;
 310                         }
 311                         if (!skb) {
 312                                 if (optptr[2] != 4 || optlen < 7 || ((optlen-3) & 3)) {
 313                                         pp_ptr = optptr + 1;
 314                                         goto error;
 315                                 }
 316                                 memcpy(&opt->faddr, &optptr[3], 4);
 317                                 if (optlen > 7)
 318                                         memmove(&optptr[3], &optptr[7], optlen-7);
 319                         }
 320                         opt->is_strictroute = (optptr[0] == IPOPT_SSRR);
 321                         opt->srr = optptr - iph;
 322                         break;
 323                       case IPOPT_RR:
 324                         if (opt->rr) {
 325                                 pp_ptr = optptr;
 326                                 goto error;
 327                         }
 328                         if (optlen < 3) {
 329                                 pp_ptr = optptr + 1;
 330                                 goto error;
 331                         }
 332                         if (optptr[2] < 4) {
 333                                 pp_ptr = optptr + 2;
 334                                 goto error;
 335                         }
 336                         if (optptr[2] <= optlen) {
 337                                 if (optptr[2]+3 > optlen) {
 338                                         pp_ptr = optptr + 2;
 339                                         goto error;
 340                                 }
 341                                 if (skb) {
 342                                         memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
 343                                         opt->is_changed = 1;
 344                                 }
 345                                 optptr[2] += 4;
 346                                 opt->rr_needaddr = 1;
 347                         }
 348                         opt->rr = optptr - iph;
 349                         break;
 350                       case IPOPT_TIMESTAMP:
 351                         if (opt->ts) {
 352                                 pp_ptr = optptr;
 353                                 goto error;
 354                         }
 355                         if (optlen < 4) {
 356                                 pp_ptr = optptr + 1;
 357                                 goto error;
 358                         }
 359                         if (optptr[2] < 5) {
 360                                 pp_ptr = optptr + 2;
 361                                 goto error;
 362                         }
 363                         if (optptr[2] <= optlen) {
 364                                 __be32 *timeptr = NULL;
 365                                 if (optptr[2]+3 > optptr[1]) {
 366                                         pp_ptr = optptr + 2;
 367                                         goto error;
 368                                 }
 369                                 switch (optptr[3]&0xF) {
 370                                       case IPOPT_TS_TSONLY:
 371                                         opt->ts = optptr - iph;
 372                                         if (skb)
 373                                                 timeptr = (__be32*)&optptr[optptr[2]-1];
 374                                         opt->ts_needtime = 1;
 375                                         optptr[2] += 4;
 376                                         break;
 377                                       case IPOPT_TS_TSANDADDR:
 378                                         if (optptr[2]+7 > optptr[1]) {
 379                                                 pp_ptr = optptr + 2;
 380                                                 goto error;
 381                                         }
 382                                         opt->ts = optptr - iph;
 383                                         if (skb) {
 384                                                 memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
 385                                                 timeptr = (__be32*)&optptr[optptr[2]+3];
 386                                         }
 387                                         opt->ts_needaddr = 1;
 388                                         opt->ts_needtime = 1;
 389                                         optptr[2] += 8;
 390                                         break;
 391                                       case IPOPT_TS_PRESPEC:
 392                                         if (optptr[2]+7 > optptr[1]) {
 393                                                 pp_ptr = optptr + 2;
 394                                                 goto error;
 395                                         }
 396                                         opt->ts = optptr - iph;
 397                                         {
 398                                                 __be32 addr;
 399                                                 memcpy(&addr, &optptr[optptr[2]-1], 4);
 400                                                 if (inet_addr_type(&init_net, addr) == RTN_UNICAST)
 401                                                         break;
 402                                                 if (skb)
 403                                                         timeptr = (__be32*)&optptr[optptr[2]+3];
 404                                         }
 405                                         opt->ts_needtime = 1;
 406                                         optptr[2] += 8;
 407                                         break;
 408                                       default:
 409                                         if (!skb && !capable(CAP_NET_RAW)) {
 410                                                 pp_ptr = optptr + 3;
 411                                                 goto error;
 412                                         }
 413                                         break;
 414                                 }
 415                                 if (timeptr) {
 416                                         struct timeval tv;
 417                                         __be32  midtime;
 418                                         do_gettimeofday(&tv);
 419                                         midtime = htonl((tv.tv_sec % 86400) * 1000 + tv.tv_usec / 1000);
 420                                         memcpy(timeptr, &midtime, sizeof(__be32));
 421                                         opt->is_changed = 1;
 422                                 }
 423                         } else {
 424                                 unsigned overflow = optptr[3]>>4;
 425                                 if (overflow == 15) {
 426                                         pp_ptr = optptr + 3;
 427                                         goto error;
 428                                 }
 429                                 opt->ts = optptr - iph;
 430                                 if (skb) {
 431                                         optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
 432                                         opt->is_changed = 1;
 433                                 }
 434                         }
 435                         break;
 436                       case IPOPT_RA:
 437                         if (optlen < 4) {
 438                                 pp_ptr = optptr + 1;
 439                                 goto error;
 440                         }
 441                         if (optptr[2] == 0 && optptr[3] == 0)
 442                                 opt->router_alert = optptr - iph;
 443                         break;
 444                       case IPOPT_CIPSO:
 445                         if ((!skb && !capable(CAP_NET_RAW)) || opt->cipso) {
 446                                 pp_ptr = optptr;
 447                                 goto error;
 448                         }
 449                         opt->cipso = optptr - iph;
 450                         if (cipso_v4_validate(&optptr)) {
 451                                 pp_ptr = optptr;
 452                                 goto error;
 453                         }
 454                         break;
 455                       case IPOPT_SEC:
 456                       case IPOPT_SID:
 457                       default:
 458                         if (!skb && !capable(CAP_NET_RAW)) {
 459                                 pp_ptr = optptr;
 460                                 goto error;
 461                         }
 462                         break;
 463                 }
 464                 l -= optlen;
 465                 optptr += optlen;
 466         }
 467
 468 eol:
 469         if (!pp_ptr)
 470                 return 0;
 471
 472 error:
 473         if (skb) {
 474                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((pp_ptr-iph)<<24));
 475         }
 476         return -EINVAL;
 477 }
 478
 479
 480 /*
 481  *      Undo all the changes done by ip_options_compile().
 482  */
 483
 484 void ip_options_undo(struct ip_options * opt)
 485 {
 486         if (opt->srr) {
 487                 unsigned  char * optptr = opt->__data+opt->srr-sizeof(struct  iphdr);
 488                 memmove(optptr+7, optptr+3, optptr[1]-7);
 489                 memcpy(optptr+3, &opt->faddr, 4);
 490         }
 491         if (opt->rr_needaddr) {
 492                 unsigned  char * optptr = opt->__data+opt->rr-sizeof(struct  iphdr);
 493                 optptr[2] -= 4;
 494                 memset(&optptr[optptr[2]-1], 0, 4);
 495         }
 496         if (opt->ts) {
 497                 unsigned  char * optptr = opt->__data+opt->ts-sizeof(struct  iphdr);
 498                 if (opt->ts_needtime) {
 499                         optptr[2] -= 4;
 500                         memset(&optptr[optptr[2]-1], 0, 4);
 501                         if ((optptr[3]&0xF) == IPOPT_TS_PRESPEC)
 502                                 optptr[2] -= 4;
 503                 }
 504                 if (opt->ts_needaddr) {
 505                         optptr[2] -= 4;
 506                         memset(&optptr[optptr[2]-1], 0, 4);
 507                 }
 508         }
 509 }
 510
 511 static struct ip_options *ip_options_get_alloc(const int optlen)
 512 {
 513         return kzalloc(sizeof(struct ip_options) + ((optlen + 3) & ~3),
 514                        GFP_KERNEL);
 515 }
 516
 517 static int ip_options_get_finish(struct ip_options **optp,
 518                                  struct ip_options *opt, int optlen)
 519 {
 520         while (optlen & 3)
 521                 opt->__data[optlen++] = IPOPT_END;
 522         opt->optlen = optlen;
 523         opt->is_data = 1;
 524         if (optlen && ip_options_compile(opt, NULL)) {
 525                 kfree(opt);
 526                 return -EINVAL;
 527         }
 528         kfree(*optp);
 529         *optp = opt;
 530         return 0;
 531 }
 532
 533 int ip_options_get_from_user(struct ip_options **optp, unsigned char __user *data, int optlen)
 534 {
 535         struct ip_options *opt = ip_options_get_alloc(optlen);
 536
 537         if (!opt)
 538                 return -ENOMEM;
 539         if (optlen && copy_from_user(opt->__data, data, optlen)) {
 540                 kfree(opt);
 541                 return -EFAULT;
 542         }
 543         return ip_options_get_finish(optp, opt, optlen);
 544 }
 545
 546 int ip_options_get(struct ip_options **optp, unsigned char *data, int optlen)
 547 {
 548         struct ip_options *opt = ip_options_get_alloc(optlen);
 549
 550         if (!opt)
 551                 return -ENOMEM;
 552         if (optlen)
 553                 memcpy(opt->__data, data, optlen);
 554         return ip_options_get_finish(optp, opt, optlen);
 555 }
 556
 557 void ip_forward_options(struct sk_buff *skb)
 558 {
 559         struct   ip_options * opt       = &(IPCB(skb)->opt);
 560         unsigned char * optptr;
 561         struct rtable *rt = skb->rtable;
 562         unsigned char *raw = skb_network_header(skb);
 563
 564         if (opt->rr_needaddr) {
 565                 optptr = (unsigned char *)raw + opt->rr;
 566                 ip_rt_get_source(&optptr[optptr[2]-5], rt);
 567                 opt->is_changed = 1;
 568         }
 569         if (opt->srr_is_hit) {
 570                 int srrptr, srrspace;
 571
 572                 optptr = raw + opt->srr;
 573
 574                 for ( srrptr=optptr[2], srrspace = optptr[1];
 575                      srrptr <= srrspace;
 576                      srrptr += 4
 577                      ) {
 578                         if (srrptr + 3 > srrspace)
 579                                 break;
 580                         if (memcmp(&rt->rt_dst, &optptr[srrptr-1], 4) == 0)
 581                                 break;
 582                 }
 583                 if (srrptr + 3 <= srrspace) {
 584                         opt->is_changed = 1;
 585                         ip_rt_get_source(&optptr[srrptr-1], rt);
 586                         ip_hdr(skb)->daddr = rt->rt_dst;
 587                         optptr[2] = srrptr+4;
 588                 } else if (net_ratelimit())
 589                         printk(KERN_CRIT "ip_forward(): Argh! Destination lost!\n");
 590                 if (opt->ts_needaddr) {
 591                         optptr = raw + opt->ts;
 592                         ip_rt_get_source(&optptr[optptr[2]-9], rt);
 593                         opt->is_changed = 1;
 594                 }
 595         }
 596         if (opt->is_changed) {
 597                 opt->is_changed = 0;
 598                 ip_send_check(ip_hdr(skb));
 599         }
 600 }
 601
 602 int ip_options_rcv_srr(struct sk_buff *skb)
 603 {
 604         struct ip_options *opt = &(IPCB(skb)->opt);
 605         int srrspace, srrptr;
 606         __be32 nexthop;
 607         struct iphdr *iph = ip_hdr(skb);
 608         unsigned char *optptr = skb_network_header(skb) + opt->srr;
 609         struct rtable *rt = skb->rtable;
 610         struct rtable *rt2;
 611         int err;
 612
 613         if (!opt->srr)
 614                 return 0;
 615
 616         if (skb->pkt_type != PACKET_HOST)
 617                 return -EINVAL;
 618         if (rt->rt_type == RTN_UNICAST) {
 619                 if (!opt->is_strictroute)
 620                         return 0;
 621                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
 622                 return -EINVAL;
 623         }
 624         if (rt->rt_type != RTN_LOCAL)
 625                 return -EINVAL;
 626
 627         for (srrptr=optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
 628                 if (srrptr + 3 > srrspace) {
 629                         icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
 630                         return -EINVAL;
 631                 }
 632                 memcpy(&nexthop, &optptr[srrptr-1], 4);
 633
 634                 rt = skb->rtable;
 635                 skb->rtable = NULL;
 636                 err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, skb->dev);
 637                 rt2 = skb->rtable;
 638                 if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
 639                         ip_rt_put(rt2);
 640                         skb->rtable = rt;
 641                         return -EINVAL;
 642                 }
 643                 ip_rt_put(rt);
 644                 if (rt2->rt_type != RTN_LOCAL)
 645                         break;
 646                 /* Superfast 8) loopback forward */
 647                 memcpy(&iph->daddr, &optptr[srrptr-1], 4);
 648                 opt->is_changed = 1;
 649         }
 650         if (srrptr <= srrspace) {
 651                 opt->srr_is_hit = 1;
 652                 opt->is_changed = 1;
 653         }
 654         return 0;
 655 }