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