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  * Authors:     A.N.Kuznetsov
   9  *
  10  */
  11
  12 #include <linux/capability.h>
  13 #include <linux/module.h>
  14 #include <linux/slab.h>
  15 #include <linux/types.h>
  16 #include <asm/uaccess.h>
  17 #include <asm/unaligned.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
  49         if (opt->srr)
  50                 memcpy(iph+opt->srr+iph[opt->srr+1]-4, &daddr, 4);
  51
  52         if (!is_frag) {
  53                 if (opt->rr_needaddr)
  54                         ip_rt_get_source(iph+opt->rr+iph[opt->rr+2]-5, skb, rt);
  55                 if (opt->ts_needaddr)
  56                         ip_rt_get_source(iph+opt->ts+iph[opt->ts+2]-9, skb, rt);
  57                 if (opt->ts_needtime) {
  58                         struct timespec tv;
  59                         __be32 midtime;
  60                         getnstimeofday(&tv);
  61                         midtime = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + tv.tv_nsec / NSEC_PER_MSEC);
  62                         memcpy(iph+opt->ts+iph[opt->ts+2]-5, &midtime, 4);
  63                 }
  64                 return;
  65         }
  66         if (opt->rr) {
  67                 memset(iph+opt->rr, IPOPT_NOP, iph[opt->rr+1]);
  68                 opt->rr = 0;
  69                 opt->rr_needaddr = 0;
  70         }
  71         if (opt->ts) {
  72                 memset(iph+opt->ts, IPOPT_NOP, iph[opt->ts+1]);
  73                 opt->ts = 0;
  74                 opt->ts_needaddr = opt->ts_needtime = 0;
  75         }
  76 }
  77
  78 /*
  79  * Provided (sopt, skb) points to received options,
  80  * build in dopt compiled option set appropriate for answering.
  81  * i.e. invert SRR option, copy anothers,
  82  * and grab room in RR/TS options.
  83  *
  84  * NOTE: dopt cannot point to skb.
  85  */
  86
  87 int ip_options_echo(struct ip_options *dopt, struct sk_buff *skb)
  88 {
  89         const struct ip_options *sopt;
  90         unsigned char *sptr, *dptr;
  91         int soffset, doffset;
  92         int     optlen;
  93         __be32  daddr;
  94
  95         memset(dopt, 0, sizeof(struct ip_options));
  96
  97         sopt = &(IPCB(skb)->opt);
  98
  99         if (sopt->optlen == 0)
 100                 return 0;
 101
 102         sptr = skb_network_header(skb);
 103         dptr = dopt->__data;
 104
 105         daddr = skb_rtable(skb)->rt_spec_dst;
 106
 107         if (sopt->rr) {
 108                 optlen  = sptr[sopt->rr+1];
 109                 soffset = sptr[sopt->rr+2];
 110                 dopt->rr = dopt->optlen + sizeof(struct iphdr);
 111                 memcpy(dptr, sptr+sopt->rr, optlen);
 112                 if (sopt->rr_needaddr && soffset <= optlen) {
 113                         if (soffset + 3 > optlen)
 114                                 return -EINVAL;
 115                         dptr[2] = soffset + 4;
 116                         dopt->rr_needaddr = 1;
 117                 }
 118                 dptr += optlen;
 119                 dopt->optlen += optlen;
 120         }
 121         if (sopt->ts) {
 122                 optlen = sptr[sopt->ts+1];
 123                 soffset = sptr[sopt->ts+2];
 124                 dopt->ts = dopt->optlen + sizeof(struct iphdr);
 125                 memcpy(dptr, sptr+sopt->ts, optlen);
 126                 if (soffset <= optlen) {
 127                         if (sopt->ts_needaddr) {
 128                                 if (soffset + 3 > optlen)
 129                                         return -EINVAL;
 130                                 dopt->ts_needaddr = 1;
 131                                 soffset += 4;
 132                         }
 133                         if (sopt->ts_needtime) {
 134                                 if (soffset + 3 > optlen)
 135                                         return -EINVAL;
 136                                 if ((dptr[3]&0xF) != IPOPT_TS_PRESPEC) {
 137                                         dopt->ts_needtime = 1;
 138                                         soffset += 4;
 139                                 } else {
 140                                         dopt->ts_needtime = 0;
 141
 142                                         if (soffset + 7 <= optlen) {
 143                                                 __be32 addr;
 144
 145                                                 memcpy(&addr, dptr+soffset-1, 4);
 146                                                 if (inet_addr_type(dev_net(skb_dst(skb)->dev), addr) != RTN_UNICAST) {
 147                                                         dopt->ts_needtime = 1;
 148                                                         soffset += 8;
 149                                                 }
 150                                         }
 151                                 }
 152                         }
 153                         dptr[2] = soffset;
 154                 }
 155                 dptr += optlen;
 156                 dopt->optlen += optlen;
 157         }
 158         if (sopt->srr) {
 159                 unsigned char *start = sptr+sopt->srr;
 160                 __be32 faddr;
 161
 162                 optlen  = start[1];
 163                 soffset = start[2];
 164                 doffset = 0;
 165                 if (soffset > optlen)
 166                         soffset = optlen + 1;
 167                 soffset -= 4;
 168                 if (soffset > 3) {
 169                         memcpy(&faddr, &start[soffset-1], 4);
 170                         for (soffset-=4, doffset=4; soffset > 3; soffset-=4, doffset+=4)
 171                                 memcpy(&dptr[doffset-1], &start[soffset-1], 4);
 172                         /*
 173                          * RFC1812 requires to fix illegal source routes.
 174                          */
 175                         if (memcmp(&ip_hdr(skb)->saddr,
 176                                    &start[soffset + 3], 4) == 0)
 177                                 doffset -= 4;
 178                 }
 179                 if (doffset > 3) {
 180                         memcpy(&start[doffset-1], &daddr, 4);
 181                         dopt->faddr = faddr;
 182                         dptr[0] = start[0];
 183                         dptr[1] = doffset+3;
 184                         dptr[2] = 4;
 185                         dptr += doffset+3;
 186                         dopt->srr = dopt->optlen + sizeof(struct iphdr);
 187                         dopt->optlen += doffset+3;
 188                         dopt->is_strictroute = sopt->is_strictroute;
 189                 }
 190         }
 191         if (sopt->cipso) {
 192                 optlen  = sptr[sopt->cipso+1];
 193                 dopt->cipso = dopt->optlen+sizeof(struct iphdr);
 194                 memcpy(dptr, sptr+sopt->cipso, optlen);
 195                 dptr += optlen;
 196                 dopt->optlen += optlen;
 197         }
 198         while (dopt->optlen & 3) {
 199                 *dptr++ = IPOPT_END;
 200                 dopt->optlen++;
 201         }
 202         return 0;
 203 }
 204
 205 /*
 206  *      Options "fragmenting", just fill options not
 207  *      allowed in fragments with NOOPs.
 208  *      Simple and stupid 8), but the most efficient way.
 209  */
 210
 211 void ip_options_fragment(struct sk_buff * skb)
 212 {
 213         unsigned char *optptr = skb_network_header(skb) + sizeof(struct iphdr);
 214         struct ip_options * opt = &(IPCB(skb)->opt);
 215         int  l = opt->optlen;
 216         int  optlen;
 217
 218         while (l > 0) {
 219                 switch (*optptr) {
 220                 case IPOPT_END:
 221                         return;
 222                 case IPOPT_NOOP:
 223                         l--;
 224                         optptr++;
 225                         continue;
 226                 }
 227                 optlen = optptr[1];
 228                 if (optlen<2 || optlen>l)
 229                   return;
 230                 if (!IPOPT_COPIED(*optptr))
 231                         memset(optptr, IPOPT_NOOP, optlen);
 232                 l -= optlen;
 233                 optptr += optlen;
 234         }
 235         opt->ts = 0;
 236         opt->rr = 0;
 237         opt->rr_needaddr = 0;
 238         opt->ts_needaddr = 0;
 239         opt->ts_needtime = 0;
 240 }
 241
 242 /*
 243  * Verify options and fill pointers in struct options.
 244  * Caller should clear *opt, and set opt->data.
 245  * If opt == NULL, then skb->data should point to IP header.
 246  */
 247
 248 int ip_options_compile(struct net *net,
 249                        struct ip_options * opt, struct sk_buff * skb)
 250 {
 251         int l;
 252         unsigned char * iph;
 253         unsigned char * optptr;
 254         int optlen;
 255         unsigned char * pp_ptr = NULL;
 256         struct rtable *rt = NULL;
 257
 258         if (skb != NULL) {
 259                 rt = skb_rtable(skb);
 260                 optptr = (unsigned char *)&(ip_hdr(skb)[1]);
 261         } else
 262                 optptr = opt->__data;
 263         iph = optptr - sizeof(struct iphdr);
 264
 265         for (l = opt->optlen; l > 0; ) {
 266                 switch (*optptr) {
 267                       case IPOPT_END:
 268                         for (optptr++, l--; l>0; optptr++, l--) {
 269                                 if (*optptr != IPOPT_END) {
 270                                         *optptr = IPOPT_END;
 271                                         opt->is_changed = 1;
 272                                 }
 273                         }
 274                         goto eol;
 275                       case IPOPT_NOOP:
 276                         l--;
 277                         optptr++;
 278                         continue;
 279                 }
 280                 optlen = optptr[1];
 281                 if (optlen<2 || optlen>l) {
 282                         pp_ptr = optptr;
 283                         goto error;
 284                 }
 285                 switch (*optptr) {
 286                       case IPOPT_SSRR:
 287                       case IPOPT_LSRR:
 288                         if (optlen < 3) {
 289                                 pp_ptr = optptr + 1;
 290                                 goto error;
 291                         }
 292                         if (optptr[2] < 4) {
 293                                 pp_ptr = optptr + 2;
 294                                 goto error;
 295                         }
 296                         /* NB: cf RFC-1812 5.2.4.1 */
 297                         if (opt->srr) {
 298                                 pp_ptr = optptr;
 299                                 goto error;
 300                         }
 301                         if (!skb) {
 302                                 if (optptr[2] != 4 || optlen < 7 || ((optlen-3) & 3)) {
 303                                         pp_ptr = optptr + 1;
 304                                         goto error;
 305                                 }
 306                                 memcpy(&opt->faddr, &optptr[3], 4);
 307                                 if (optlen > 7)
 308                                         memmove(&optptr[3], &optptr[7], optlen-7);
 309                         }
 310                         opt->is_strictroute = (optptr[0] == IPOPT_SSRR);
 311                         opt->srr = optptr - iph;
 312                         break;
 313                       case IPOPT_RR:
 314                         if (opt->rr) {
 315                                 pp_ptr = optptr;
 316                                 goto error;
 317                         }
 318                         if (optlen < 3) {
 319                                 pp_ptr = optptr + 1;
 320                                 goto error;
 321                         }
 322                         if (optptr[2] < 4) {
 323                                 pp_ptr = optptr + 2;
 324                                 goto error;
 325                         }
 326                         if (optptr[2] <= optlen) {
 327                                 if (optptr[2]+3 > optlen) {
 328                                         pp_ptr = optptr + 2;
 329                                         goto error;
 330                                 }
 331                                 if (rt) {
 332                                         memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
 333                                         opt->is_changed = 1;
 334                                 }
 335                                 optptr[2] += 4;
 336                                 opt->rr_needaddr = 1;
 337                         }
 338                         opt->rr = optptr - iph;
 339                         break;
 340                       case IPOPT_TIMESTAMP:
 341                         if (opt->ts) {
 342                                 pp_ptr = optptr;
 343                                 goto error;
 344                         }
 345                         if (optlen < 4) {
 346                                 pp_ptr = optptr + 1;
 347                                 goto error;
 348                         }
 349                         if (optptr[2] < 5) {
 350                                 pp_ptr = optptr + 2;
 351                                 goto error;
 352                         }
 353                         if (optptr[2] <= optlen) {
 354                                 unsigned char *timeptr = NULL;
 355                                 if (optptr[2]+3 > optptr[1]) {
 356                                         pp_ptr = optptr + 2;
 357                                         goto error;
 358                                 }
 359                                 switch (optptr[3]&0xF) {
 360                                       case IPOPT_TS_TSONLY:
 361                                         opt->ts = optptr - iph;
 362                                         if (skb)
 363                                                 timeptr = &optptr[optptr[2]-1];
 364                                         opt->ts_needtime = 1;
 365                                         optptr[2] += 4;
 366                                         break;
 367                                       case IPOPT_TS_TSANDADDR:
 368                                         if (optptr[2]+7 > optptr[1]) {
 369                                                 pp_ptr = optptr + 2;
 370                                                 goto error;
 371                                         }
 372                                         opt->ts = optptr - iph;
 373                                         if (rt)  {
 374                                                 memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
 375                                                 timeptr = &optptr[optptr[2]+3];
 376                                         }
 377                                         opt->ts_needaddr = 1;
 378                                         opt->ts_needtime = 1;
 379                                         optptr[2] += 8;
 380                                         break;
 381                                       case IPOPT_TS_PRESPEC:
 382                                         if (optptr[2]+7 > optptr[1]) {
 383                                                 pp_ptr = optptr + 2;
 384                                                 goto error;
 385                                         }
 386                                         opt->ts = optptr - iph;
 387                                         {
 388                                                 __be32 addr;
 389                                                 memcpy(&addr, &optptr[optptr[2]-1], 4);
 390                                                 if (inet_addr_type(net, addr) == RTN_UNICAST)
 391                                                         break;
 392                                                 if (skb)
 393                                                         timeptr = &optptr[optptr[2]+3];
 394                                         }
 395                                         opt->ts_needtime = 1;
 396                                         optptr[2] += 8;
 397                                         break;
 398                                       default:
 399                                         if (!skb && !capable(CAP_NET_RAW)) {
 400                                                 pp_ptr = optptr + 3;
 401                                                 goto error;
 402                                         }
 403                                         break;
 404                                 }
 405                                 if (timeptr) {
 406                                         struct timespec tv;
 407                                         u32  midtime;
 408                                         getnstimeofday(&tv);
 409                                         midtime = (tv.tv_sec % 86400) * MSEC_PER_SEC + tv.tv_nsec / NSEC_PER_MSEC;
 410                                         put_unaligned_be32(midtime, timeptr);
 411                                         opt->is_changed = 1;
 412                                 }
 413                         } else {
 414                                 unsigned overflow = optptr[3]>>4;
 415                                 if (overflow == 15) {
 416                                         pp_ptr = optptr + 3;
 417                                         goto error;
 418                                 }
 419                                 opt->ts = optptr - iph;
 420                                 if (skb) {
 421                                         optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
 422                                         opt->is_changed = 1;
 423                                 }
 424                         }
 425                         break;
 426                       case IPOPT_RA:
 427                         if (optlen < 4) {
 428                                 pp_ptr = optptr + 1;
 429                                 goto error;
 430                         }
 431                         if (optptr[2] == 0 && optptr[3] == 0)
 432                                 opt->router_alert = optptr - iph;
 433                         break;
 434                       case IPOPT_CIPSO:
 435                         if ((!skb && !capable(CAP_NET_RAW)) || opt->cipso) {
 436                                 pp_ptr = optptr;
 437                                 goto error;
 438                         }
 439                         opt->cipso = optptr - iph;
 440                         if (cipso_v4_validate(skb, &optptr)) {
 441                                 pp_ptr = optptr;
 442                                 goto error;
 443                         }
 444                         break;
 445                       case IPOPT_SEC:
 446                       case IPOPT_SID:
 447                       default:
 448                         if (!skb && !capable(CAP_NET_RAW)) {
 449                                 pp_ptr = optptr;
 450                                 goto error;
 451                         }
 452                         break;
 453                 }
 454                 l -= optlen;
 455                 optptr += optlen;
 456         }
 457
 458 eol:
 459         if (!pp_ptr)
 460                 return 0;
 461
 462 error:
 463         if (skb) {
 464                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((pp_ptr-iph)<<24));
 465         }
 466         return -EINVAL;
 467 }
 468 EXPORT_SYMBOL(ip_options_compile);
 469
 470 /*
 471  *      Undo all the changes done by ip_options_compile().
 472  */
 473
 474 void ip_options_undo(struct ip_options * opt)
 475 {
 476         if (opt->srr) {
 477                 unsigned  char * optptr = opt->__data+opt->srr-sizeof(struct  iphdr);
 478                 memmove(optptr+7, optptr+3, optptr[1]-7);
 479                 memcpy(optptr+3, &opt->faddr, 4);
 480         }
 481         if (opt->rr_needaddr) {
 482                 unsigned  char * optptr = opt->__data+opt->rr-sizeof(struct  iphdr);
 483                 optptr[2] -= 4;
 484                 memset(&optptr[optptr[2]-1], 0, 4);
 485         }
 486         if (opt->ts) {
 487                 unsigned  char * optptr = opt->__data+opt->ts-sizeof(struct  iphdr);
 488                 if (opt->ts_needtime) {
 489                         optptr[2] -= 4;
 490                         memset(&optptr[optptr[2]-1], 0, 4);
 491                         if ((optptr[3]&0xF) == IPOPT_TS_PRESPEC)
 492                                 optptr[2] -= 4;
 493                 }
 494                 if (opt->ts_needaddr) {
 495                         optptr[2] -= 4;
 496                         memset(&optptr[optptr[2]-1], 0, 4);
 497                 }
 498         }
 499 }
 500
 501 static struct ip_options_rcu *ip_options_get_alloc(const int optlen)
 502 {
 503         return kzalloc(sizeof(struct ip_options_rcu) + ((optlen + 3) & ~3),
 504                        GFP_KERNEL);
 505 }
 506
 507 static int ip_options_get_finish(struct net *net, struct ip_options_rcu **optp,
 508                                  struct ip_options_rcu *opt, int optlen)
 509 {
 510         while (optlen & 3)
 511                 opt->opt.__data[optlen++] = IPOPT_END;
 512         opt->opt.optlen = optlen;
 513         if (optlen && ip_options_compile(net, &opt->opt, NULL)) {
 514                 kfree(opt);
 515                 return -EINVAL;
 516         }
 517         kfree(*optp);
 518         *optp = opt;
 519         return 0;
 520 }
 521
 522 int ip_options_get_from_user(struct net *net, struct ip_options_rcu **optp,
 523                              unsigned char __user *data, int optlen)
 524 {
 525         struct ip_options_rcu *opt = ip_options_get_alloc(optlen);
 526
 527         if (!opt)
 528                 return -ENOMEM;
 529         if (optlen && copy_from_user(opt->opt.__data, data, optlen)) {
 530                 kfree(opt);
 531                 return -EFAULT;
 532         }
 533         return ip_options_get_finish(net, optp, opt, optlen);
 534 }
 535
 536 int ip_options_get(struct net *net, struct ip_options_rcu **optp,
 537                    unsigned char *data, int optlen)
 538 {
 539         struct ip_options_rcu *opt = ip_options_get_alloc(optlen);
 540
 541         if (!opt)
 542                 return -ENOMEM;
 543         if (optlen)
 544                 memcpy(opt->opt.__data, data, optlen);
 545         return ip_options_get_finish(net, optp, opt, optlen);
 546 }
 547
 548 void ip_forward_options(struct sk_buff *skb)
 549 {
 550         struct   ip_options * opt       = &(IPCB(skb)->opt);
 551         unsigned char * optptr;
 552         struct rtable *rt = skb_rtable(skb);
 553         unsigned char *raw = skb_network_header(skb);
 554
 555         if (opt->rr_needaddr) {
 556                 optptr = (unsigned char *)raw + opt->rr;
 557                 ip_rt_get_source(&optptr[optptr[2]-5], skb, rt);
 558                 opt->is_changed = 1;
 559         }
 560         if (opt->srr_is_hit) {
 561                 int srrptr, srrspace;
 562
 563                 optptr = raw + opt->srr;
 564
 565                 for ( srrptr=optptr[2], srrspace = optptr[1];
 566                      srrptr <= srrspace;
 567                      srrptr += 4
 568                      ) {
 569                         if (srrptr + 3 > srrspace)
 570                                 break;
 571                         if (memcmp(&opt->nexthop, &optptr[srrptr-1], 4) == 0)
 572                                 break;
 573                 }
 574                 if (srrptr + 3 <= srrspace) {
 575                         opt->is_changed = 1;
 576                         ip_rt_get_source(&optptr[srrptr-1], skb, rt);
 577                         ip_hdr(skb)->daddr = opt->nexthop;
 578                         optptr[2] = srrptr+4;
 579                 } else if (net_ratelimit())
 580                         printk(KERN_CRIT "ip_forward(): Argh! Destination lost!\n");
 581                 if (opt->ts_needaddr) {
 582                         optptr = raw + opt->ts;
 583                         ip_rt_get_source(&optptr[optptr[2]-9], skb, rt);
 584                         opt->is_changed = 1;
 585                 }
 586         }
 587         if (opt->is_changed) {
 588                 opt->is_changed = 0;
 589                 ip_send_check(ip_hdr(skb));
 590         }
 591 }
 592
 593 int ip_options_rcv_srr(struct sk_buff *skb)
 594 {
 595         struct ip_options *opt = &(IPCB(skb)->opt);
 596         int srrspace, srrptr;
 597         __be32 nexthop;
 598         struct iphdr *iph = ip_hdr(skb);
 599         unsigned char *optptr = skb_network_header(skb) + opt->srr;
 600         struct rtable *rt = skb_rtable(skb);
 601         struct rtable *rt2;
 602         unsigned long orefdst;
 603         int err;
 604
 605         if (!rt)
 606                 return 0;
 607
 608         if (skb->pkt_type != PACKET_HOST)
 609                 return -EINVAL;
 610         if (rt->rt_type == RTN_UNICAST) {
 611                 if (!opt->is_strictroute)
 612                         return 0;
 613                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
 614                 return -EINVAL;
 615         }
 616         if (rt->rt_type != RTN_LOCAL)
 617                 return -EINVAL;
 618
 619         for (srrptr=optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
 620                 if (srrptr + 3 > srrspace) {
 621                         icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
 622                         return -EINVAL;
 623                 }
 624                 memcpy(&nexthop, &optptr[srrptr-1], 4);
 625
 626                 orefdst = skb->_skb_refdst;
 627                 skb_dst_set(skb, NULL);
 628                 err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, skb->dev);
 629                 rt2 = skb_rtable(skb);
 630                 if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
 631                         skb_dst_drop(skb);
 632                         skb->_skb_refdst = orefdst;
 633                         return -EINVAL;
 634                 }
 635                 refdst_drop(orefdst);
 636                 if (rt2->rt_type != RTN_LOCAL)
 637                         break;
 638                 /* Superfast 8) loopback forward */
 639                 iph->daddr = nexthop;
 640                 opt->is_changed = 1;
 641         }
 642         if (srrptr <= srrspace) {
 643                 opt->srr_is_hit = 1;
 644                 opt->nexthop = nexthop;
 645                 opt->is_changed = 1;
 646         }
 647         return 0;
 648 }
 649 EXPORT_SYMBOL(ip_options_rcv_srr);