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 #define pr_fmt(fmt) "IPv4: " fmt
  13
  14 #include <linux/capability.h>
  15 #include <linux/module.h>
  16 #include <linux/slab.h>
  17 #include <linux/types.h>
  18 #include <asm/uaccess.h>
  19 #include <asm/unaligned.h>
  20 #include <linux/skbuff.h>
  21 #include <linux/ip.h>
  22 #include <linux/icmp.h>
  23 #include <linux/netdevice.h>
  24 #include <linux/rtnetlink.h>
  25 #include <net/sock.h>
  26 #include <net/ip.h>
  27 #include <net/icmp.h>
  28 #include <net/route.h>
  29 #include <net/cipso_ipv4.h>
  30 #include <net/ip_fib.h>
  31
  32 /*
  33  * Write options to IP header, record destination address to
  34  * source route option, address of outgoing interface
  35  * (we should already know it, so that this  function is allowed be
  36  * called only after routing decision) and timestamp,
  37  * if we originate this datagram.
  38  *
  39  * daddr is real destination address, next hop is recorded in IP header.
  40  * saddr is address of outgoing interface.
  41  */
  42
  43 void ip_options_build(struct sk_buff *skb, struct ip_options *opt,
  44                       __be32 daddr, struct rtable *rt, int is_frag)
  45 {
  46         unsigned char *iph = skb_network_header(skb);
  47
  48         memcpy(&(IPCB(skb)->opt), opt, sizeof(struct ip_options));
  49         memcpy(iph+sizeof(struct iphdr), opt->__data, opt->optlen);
  50         opt = &(IPCB(skb)->opt);
  51
  52         if (opt->srr)
  53                 memcpy(iph+opt->srr+iph[opt->srr+1]-4, &daddr, 4);
  54
  55         if (!is_frag) {
  56                 if (opt->rr_needaddr)
  57                         ip_rt_get_source(iph+opt->rr+iph[opt->rr+2]-5, skb, rt);
  58                 if (opt->ts_needaddr)
  59                         ip_rt_get_source(iph+opt->ts+iph[opt->ts+2]-9, skb, rt);
  60                 if (opt->ts_needtime) {
  61                         struct timespec tv;
  62                         __be32 midtime;
  63                         getnstimeofday(&tv);
  64                         midtime = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + tv.tv_nsec / NSEC_PER_MSEC);
  65                         memcpy(iph+opt->ts+iph[opt->ts+2]-5, &midtime, 4);
  66                 }
  67                 return;
  68         }
  69         if (opt->rr) {
  70                 memset(iph+opt->rr, IPOPT_NOP, iph[opt->rr+1]);
  71                 opt->rr = 0;
  72                 opt->rr_needaddr = 0;
  73         }
  74         if (opt->ts) {
  75                 memset(iph+opt->ts, IPOPT_NOP, iph[opt->ts+1]);
  76                 opt->ts = 0;
  77                 opt->ts_needaddr = opt->ts_needtime = 0;
  78         }
  79 }
  80
  81 /*
  82  * Provided (sopt, skb) points to received options,
  83  * build in dopt compiled option set appropriate for answering.
  84  * i.e. invert SRR option, copy anothers,
  85  * and grab room in RR/TS options.
  86  *
  87  * NOTE: dopt cannot point to skb.
  88  */
  89
  90 int __ip_options_echo(struct ip_options *dopt, struct sk_buff *skb,
  91                       const struct ip_options *sopt)
  92 {
  93         unsigned char *sptr, *dptr;
  94         int soffset, doffset;
  95         int     optlen;
  96
  97         memset(dopt, 0, sizeof(struct ip_options));
  98
  99         if (sopt->optlen == 0)
 100                 return 0;
 101
 102         sptr = skb_network_header(skb);
 103         dptr = dopt->__data;
 104
 105         if (sopt->rr) {
 106                 optlen  = sptr[sopt->rr+1];
 107                 soffset = sptr[sopt->rr+2];
 108                 dopt->rr = dopt->optlen + sizeof(struct iphdr);
 109                 memcpy(dptr, sptr+sopt->rr, optlen);
 110                 if (sopt->rr_needaddr && soffset <= optlen) {
 111                         if (soffset + 3 > optlen)
 112                                 return -EINVAL;
 113                         dptr[2] = soffset + 4;
 114                         dopt->rr_needaddr = 1;
 115                 }
 116                 dptr += optlen;
 117                 dopt->optlen += optlen;
 118         }
 119         if (sopt->ts) {
 120                 optlen = sptr[sopt->ts+1];
 121                 soffset = sptr[sopt->ts+2];
 122                 dopt->ts = dopt->optlen + sizeof(struct iphdr);
 123                 memcpy(dptr, sptr+sopt->ts, optlen);
 124                 if (soffset <= optlen) {
 125                         if (sopt->ts_needaddr) {
 126                                 if (soffset + 3 > optlen)
 127                                         return -EINVAL;
 128                                 dopt->ts_needaddr = 1;
 129                                 soffset += 4;
 130                         }
 131                         if (sopt->ts_needtime) {
 132                                 if (soffset + 3 > optlen)
 133                                         return -EINVAL;
 134                                 if ((dptr[3]&0xF) != IPOPT_TS_PRESPEC) {
 135                                         dopt->ts_needtime = 1;
 136                                         soffset += 4;
 137                                 } else {
 138                                         dopt->ts_needtime = 0;
 139
 140                                         if (soffset + 7 <= optlen) {
 141                                                 __be32 addr;
 142
 143                                                 memcpy(&addr, dptr+soffset-1, 4);
 144                                                 if (inet_addr_type(dev_net(skb_dst(skb)->dev), addr) != RTN_UNICAST) {
 145                                                         dopt->ts_needtime = 1;
 146                                                         soffset += 8;
 147                                                 }
 148                                         }
 149                                 }
 150                         }
 151                         dptr[2] = soffset;
 152                 }
 153                 dptr += optlen;
 154                 dopt->optlen += optlen;
 155         }
 156         if (sopt->srr) {
 157                 unsigned char *start = sptr+sopt->srr;
 158                 __be32 faddr;
 159
 160                 optlen  = start[1];
 161                 soffset = start[2];
 162                 doffset = 0;
 163                 if (soffset > optlen)
 164                         soffset = optlen + 1;
 165                 soffset -= 4;
 166                 if (soffset > 3) {
 167                         memcpy(&faddr, &start[soffset-1], 4);
 168                         for (soffset -= 4, doffset = 4; soffset > 3; soffset -= 4, doffset += 4)
 169                                 memcpy(&dptr[doffset-1], &start[soffset-1], 4);
 170                         /*
 171                          * RFC1812 requires to fix illegal source routes.
 172                          */
 173                         if (memcmp(&ip_hdr(skb)->saddr,
 174                                    &start[soffset + 3], 4) == 0)
 175                                 doffset -= 4;
 176                 }
 177                 if (doffset > 3) {
 178                         __be32 daddr = fib_compute_spec_dst(skb);
 179
 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 /* helper used by ip_options_compile() to call fib_compute_spec_dst()
 243  * at most one time.
 244  */
 245 static void spec_dst_fill(__be32 *spec_dst, struct sk_buff *skb)
 246 {
 247         if (*spec_dst == htonl(INADDR_ANY))
 248                 *spec_dst = fib_compute_spec_dst(skb);
 249 }
 250
 251 /*
 252  * Verify options and fill pointers in struct options.
 253  * Caller should clear *opt, and set opt->data.
 254  * If opt == NULL, then skb->data should point to IP header.
 255  */
 256
 257 int ip_options_compile(struct net *net,
 258                        struct ip_options *opt, struct sk_buff *skb)
 259 {
 260         __be32 spec_dst = htonl(INADDR_ANY);
 261         unsigned char *pp_ptr = NULL;
 262         struct rtable *rt = NULL;
 263         unsigned char *optptr;
 264         unsigned char *iph;
 265         int optlen, l;
 266
 267         if (skb) {
 268                 rt = skb_rtable(skb);
 269                 optptr = (unsigned char *)&(ip_hdr(skb)[1]);
 270         } else
 271                 optptr = opt->__data;
 272         iph = optptr - sizeof(struct iphdr);
 273
 274         for (l = opt->optlen; l > 0; ) {
 275                 switch (*optptr) {
 276                 case IPOPT_END:
 277                         for (optptr++, l--; l > 0; optptr++, l--) {
 278                                 if (*optptr != IPOPT_END) {
 279                                         *optptr = IPOPT_END;
 280                                         opt->is_changed = 1;
 281                                 }
 282                         }
 283                         goto eol;
 284                 case IPOPT_NOOP:
 285                         l--;
 286                         optptr++;
 287                         continue;
 288                 }
 289                 if (unlikely(l < 2)) {
 290                         pp_ptr = optptr;
 291                         goto error;
 292                 }
 293                 optlen = optptr[1];
 294                 if (optlen < 2 || optlen > l) {
 295                         pp_ptr = optptr;
 296                         goto error;
 297                 }
 298                 switch (*optptr) {
 299                 case IPOPT_SSRR:
 300                 case IPOPT_LSRR:
 301                         if (optlen < 3) {
 302                                 pp_ptr = optptr + 1;
 303                                 goto error;
 304                         }
 305                         if (optptr[2] < 4) {
 306                                 pp_ptr = optptr + 2;
 307                                 goto error;
 308                         }
 309                         /* NB: cf RFC-1812 5.2.4.1 */
 310                         if (opt->srr) {
 311                                 pp_ptr = optptr;
 312                                 goto error;
 313                         }
 314                         if (!skb) {
 315                                 if (optptr[2] != 4 || optlen < 7 || ((optlen-3) & 3)) {
 316                                         pp_ptr = optptr + 1;
 317                                         goto error;
 318                                 }
 319                                 memcpy(&opt->faddr, &optptr[3], 4);
 320                                 if (optlen > 7)
 321                                         memmove(&optptr[3], &optptr[7], optlen-7);
 322                         }
 323                         opt->is_strictroute = (optptr[0] == IPOPT_SSRR);
 324                         opt->srr = optptr - iph;
 325                         break;
 326                 case IPOPT_RR:
 327                         if (opt->rr) {
 328                                 pp_ptr = optptr;
 329                                 goto error;
 330                         }
 331                         if (optlen < 3) {
 332                                 pp_ptr = optptr + 1;
 333                                 goto error;
 334                         }
 335                         if (optptr[2] < 4) {
 336                                 pp_ptr = optptr + 2;
 337                                 goto error;
 338                         }
 339                         if (optptr[2] <= optlen) {
 340                                 if (optptr[2]+3 > optlen) {
 341                                         pp_ptr = optptr + 2;
 342                                         goto error;
 343                                 }
 344                                 if (rt) {
 345                                         spec_dst_fill(&spec_dst, skb);
 346                                         memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
 347                                         opt->is_changed = 1;
 348                                 }
 349                                 optptr[2] += 4;
 350                                 opt->rr_needaddr = 1;
 351                         }
 352                         opt->rr = optptr - iph;
 353                         break;
 354                 case IPOPT_TIMESTAMP:
 355                         if (opt->ts) {
 356                                 pp_ptr = optptr;
 357                                 goto error;
 358                         }
 359                         if (optlen < 4) {
 360                                 pp_ptr = optptr + 1;
 361                                 goto error;
 362                         }
 363                         if (optptr[2] < 5) {
 364                                 pp_ptr = optptr + 2;
 365                                 goto error;
 366                         }
 367                         if (optptr[2] <= optlen) {
 368                                 unsigned char *timeptr = NULL;
 369                                 if (optptr[2]+3 > optlen) {
 370                                         pp_ptr = optptr + 2;
 371                                         goto error;
 372                                 }
 373                                 switch (optptr[3]&0xF) {
 374                                 case IPOPT_TS_TSONLY:
 375                                         if (skb)
 376                                                 timeptr = &optptr[optptr[2]-1];
 377                                         opt->ts_needtime = 1;
 378                                         optptr[2] += 4;
 379                                         break;
 380                                 case IPOPT_TS_TSANDADDR:
 381                                         if (optptr[2]+7 > optlen) {
 382                                                 pp_ptr = optptr + 2;
 383                                                 goto error;
 384                                         }
 385                                         if (rt)  {
 386                                                 spec_dst_fill(&spec_dst, skb);
 387                                                 memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
 388                                                 timeptr = &optptr[optptr[2]+3];
 389                                         }
 390                                         opt->ts_needaddr = 1;
 391                                         opt->ts_needtime = 1;
 392                                         optptr[2] += 8;
 393                                         break;
 394                                 case IPOPT_TS_PRESPEC:
 395                                         if (optptr[2]+7 > optlen) {
 396                                                 pp_ptr = optptr + 2;
 397                                                 goto error;
 398                                         }
 399                                         {
 400                                                 __be32 addr;
 401                                                 memcpy(&addr, &optptr[optptr[2]-1], 4);
 402                                                 if (inet_addr_type(net, addr) == RTN_UNICAST)
 403                                                         break;
 404                                                 if (skb)
 405                                                         timeptr = &optptr[optptr[2]+3];
 406                                         }
 407                                         opt->ts_needtime = 1;
 408                                         optptr[2] += 8;
 409                                         break;
 410                                 default:
 411                                         if (!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) {
 412                                                 pp_ptr = optptr + 3;
 413                                                 goto error;
 414                                         }
 415                                         break;
 416                                 }
 417                                 if (timeptr) {
 418                                         struct timespec tv;
 419                                         u32  midtime;
 420                                         getnstimeofday(&tv);
 421                                         midtime = (tv.tv_sec % 86400) * MSEC_PER_SEC + tv.tv_nsec / NSEC_PER_MSEC;
 422                                         put_unaligned_be32(midtime, timeptr);
 423                                         opt->is_changed = 1;
 424                                 }
 425                         } else if ((optptr[3]&0xF) != IPOPT_TS_PRESPEC) {
 426                                 unsigned int overflow = optptr[3]>>4;
 427                                 if (overflow == 15) {
 428                                         pp_ptr = optptr + 3;
 429                                         goto error;
 430                                 }
 431                                 if (skb) {
 432                                         optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
 433                                         opt->is_changed = 1;
 434                                 }
 435                         }
 436                         opt->ts = optptr - iph;
 437                         break;
 438                 case IPOPT_RA:
 439                         if (optlen < 4) {
 440                                 pp_ptr = optptr + 1;
 441                                 goto error;
 442                         }
 443                         if (optptr[2] == 0 && optptr[3] == 0)
 444                                 opt->router_alert = optptr - iph;
 445                         break;
 446                 case IPOPT_CIPSO:
 447                         if ((!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) || opt->cipso) {
 448                                 pp_ptr = optptr;
 449                                 goto error;
 450                         }
 451                         opt->cipso = optptr - iph;
 452                         if (cipso_v4_validate(skb, &optptr)) {
 453                                 pp_ptr = optptr;
 454                                 goto error;
 455                         }
 456                         break;
 457                 case IPOPT_SEC:
 458                 case IPOPT_SID:
 459                 default:
 460                         if (!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) {
 461                                 pp_ptr = optptr;
 462                                 goto error;
 463                         }
 464                         break;
 465                 }
 466                 l -= optlen;
 467                 optptr += optlen;
 468         }
 469
 470 eol:
 471         if (!pp_ptr)
 472                 return 0;
 473
 474 error:
 475         if (skb) {
 476                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((pp_ptr-iph)<<24));
 477         }
 478         return -EINVAL;
 479 }
 480 EXPORT_SYMBOL(ip_options_compile);
 481
 482 /*
 483  *      Undo all the changes done by ip_options_compile().
 484  */
 485
 486 void ip_options_undo(struct ip_options *opt)
 487 {
 488         if (opt->srr) {
 489                 unsigned  char *optptr = opt->__data+opt->srr-sizeof(struct  iphdr);
 490                 memmove(optptr+7, optptr+3, optptr[1]-7);
 491                 memcpy(optptr+3, &opt->faddr, 4);
 492         }
 493         if (opt->rr_needaddr) {
 494                 unsigned  char *optptr = opt->__data+opt->rr-sizeof(struct  iphdr);
 495                 optptr[2] -= 4;
 496                 memset(&optptr[optptr[2]-1], 0, 4);
 497         }
 498         if (opt->ts) {
 499                 unsigned  char *optptr = opt->__data+opt->ts-sizeof(struct  iphdr);
 500                 if (opt->ts_needtime) {
 501                         optptr[2] -= 4;
 502                         memset(&optptr[optptr[2]-1], 0, 4);
 503                         if ((optptr[3]&0xF) == IPOPT_TS_PRESPEC)
 504                                 optptr[2] -= 4;
 505                 }
 506                 if (opt->ts_needaddr) {
 507                         optptr[2] -= 4;
 508                         memset(&optptr[optptr[2]-1], 0, 4);
 509                 }
 510         }
 511 }
 512
 513 static struct ip_options_rcu *ip_options_get_alloc(const int optlen)
 514 {
 515         return kzalloc(sizeof(struct ip_options_rcu) + ((optlen + 3) & ~3),
 516                        GFP_KERNEL);
 517 }
 518
 519 static int ip_options_get_finish(struct net *net, struct ip_options_rcu **optp,
 520                                  struct ip_options_rcu *opt, int optlen)
 521 {
 522         while (optlen & 3)
 523                 opt->opt.__data[optlen++] = IPOPT_END;
 524         opt->opt.optlen = optlen;
 525         if (optlen && ip_options_compile(net, &opt->opt, NULL)) {
 526                 kfree(opt);
 527                 return -EINVAL;
 528         }
 529         kfree(*optp);
 530         *optp = opt;
 531         return 0;
 532 }
 533
 534 int ip_options_get_from_user(struct net *net, struct ip_options_rcu **optp,
 535                              unsigned char __user *data, int optlen)
 536 {
 537         struct ip_options_rcu *opt = ip_options_get_alloc(optlen);
 538
 539         if (!opt)
 540                 return -ENOMEM;
 541         if (optlen && copy_from_user(opt->opt.__data, data, optlen)) {
 542                 kfree(opt);
 543                 return -EFAULT;
 544         }
 545         return ip_options_get_finish(net, optp, opt, optlen);
 546 }
 547
 548 int ip_options_get(struct net *net, struct ip_options_rcu **optp,
 549                    unsigned char *data, int optlen)
 550 {
 551         struct ip_options_rcu *opt = ip_options_get_alloc(optlen);
 552
 553         if (!opt)
 554                 return -ENOMEM;
 555         if (optlen)
 556                 memcpy(opt->opt.__data, data, optlen);
 557         return ip_options_get_finish(net, optp, opt, optlen);
 558 }
 559
 560 void ip_forward_options(struct sk_buff *skb)
 561 {
 562         struct   ip_options *opt        = &(IPCB(skb)->opt);
 563         unsigned char *optptr;
 564         struct rtable *rt = skb_rtable(skb);
 565         unsigned char *raw = skb_network_header(skb);
 566
 567         if (opt->rr_needaddr) {
 568                 optptr = (unsigned char *)raw + opt->rr;
 569                 ip_rt_get_source(&optptr[optptr[2]-5], skb, rt);
 570                 opt->is_changed = 1;
 571         }
 572         if (opt->srr_is_hit) {
 573                 int srrptr, srrspace;
 574
 575                 optptr = raw + opt->srr;
 576
 577                 for ( srrptr = optptr[2], srrspace = optptr[1];
 578                      srrptr <= srrspace;
 579                      srrptr += 4
 580                      ) {
 581                         if (srrptr + 3 > srrspace)
 582                                 break;
 583                         if (memcmp(&opt->nexthop, &optptr[srrptr-1], 4) == 0)
 584                                 break;
 585                 }
 586                 if (srrptr + 3 <= srrspace) {
 587                         opt->is_changed = 1;
 588                         ip_hdr(skb)->daddr = opt->nexthop;
 589                         ip_rt_get_source(&optptr[srrptr-1], skb, rt);
 590                         optptr[2] = srrptr+4;
 591                 } else {
 592                         net_crit_ratelimited("%s(): Argh! Destination lost!\n",
 593                                              __func__);
 594                 }
 595                 if (opt->ts_needaddr) {
 596                         optptr = raw + opt->ts;
 597                         ip_rt_get_source(&optptr[optptr[2]-9], skb, rt);
 598                         opt->is_changed = 1;
 599                 }
 600         }
 601         if (opt->is_changed) {
 602                 opt->is_changed = 0;
 603                 ip_send_check(ip_hdr(skb));
 604         }
 605 }
 606
 607 int ip_options_rcv_srr(struct sk_buff *skb)
 608 {
 609         struct ip_options *opt = &(IPCB(skb)->opt);
 610         int srrspace, srrptr;
 611         __be32 nexthop;
 612         struct iphdr *iph = ip_hdr(skb);
 613         unsigned char *optptr = skb_network_header(skb) + opt->srr;
 614         struct rtable *rt = skb_rtable(skb);
 615         struct rtable *rt2;
 616         unsigned long orefdst;
 617         int err;
 618
 619         if (!rt)
 620                 return 0;
 621
 622         if (skb->pkt_type != PACKET_HOST)
 623                 return -EINVAL;
 624         if (rt->rt_type == RTN_UNICAST) {
 625                 if (!opt->is_strictroute)
 626                         return 0;
 627                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
 628                 return -EINVAL;
 629         }
 630         if (rt->rt_type != RTN_LOCAL)
 631                 return -EINVAL;
 632
 633         for (srrptr = optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
 634                 if (srrptr + 3 > srrspace) {
 635                         icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
 636                         return -EINVAL;
 637                 }
 638                 memcpy(&nexthop, &optptr[srrptr-1], 4);
 639
 640                 orefdst = skb->_skb_refdst;
 641                 skb_dst_set(skb, NULL);
 642                 err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, skb->dev);
 643                 rt2 = skb_rtable(skb);
 644                 if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
 645                         skb_dst_drop(skb);
 646                         skb->_skb_refdst = orefdst;
 647                         return -EINVAL;
 648                 }
 649                 refdst_drop(orefdst);
 650                 if (rt2->rt_type != RTN_LOCAL)
 651                         break;
 652                 /* Superfast 8) loopback forward */
 653                 iph->daddr = nexthop;
 654                 opt->is_changed = 1;
 655         }
 656         if (srrptr <= srrspace) {
 657                 opt->srr_is_hit = 1;
 658                 opt->nexthop = nexthop;
 659                 opt->is_changed = 1;
 660         }
 661         return 0;
 662 }
 663 EXPORT_SYMBOL(ip_options_rcv_srr);