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 {
  92         const struct ip_options *sopt;
  93         unsigned char *sptr, *dptr;
  94         int soffset, doffset;
  95         int     optlen;
  96
  97         memset(dopt, 0, sizeof(struct ip_options));
  98
  99         sopt = &(IPCB(skb)->opt);
 100
 101         if (sopt->optlen == 0)
 102                 return 0;
 103
 104         sptr = skb_network_header(skb);
 105         dptr = dopt->__data;
 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                         __be32 daddr = fib_compute_spec_dst(skb);
 181
 182                         memcpy(&start[doffset-1], &daddr, 4);
 183                         dopt->faddr = faddr;
 184                         dptr[0] = start[0];
 185                         dptr[1] = doffset+3;
 186                         dptr[2] = 4;
 187                         dptr += doffset+3;
 188                         dopt->srr = dopt->optlen + sizeof(struct iphdr);
 189                         dopt->optlen += doffset+3;
 190                         dopt->is_strictroute = sopt->is_strictroute;
 191                 }
 192         }
 193         if (sopt->cipso) {
 194                 optlen  = sptr[sopt->cipso+1];
 195                 dopt->cipso = dopt->optlen+sizeof(struct iphdr);
 196                 memcpy(dptr, sptr+sopt->cipso, optlen);
 197                 dptr += optlen;
 198                 dopt->optlen += optlen;
 199         }
 200         while (dopt->optlen & 3) {
 201                 *dptr++ = IPOPT_END;
 202                 dopt->optlen++;
 203         }
 204         return 0;
 205 }
 206
 207 /*
 208  *      Options "fragmenting", just fill options not
 209  *      allowed in fragments with NOOPs.
 210  *      Simple and stupid 8), but the most efficient way.
 211  */
 212
 213 void ip_options_fragment(struct sk_buff *skb)
 214 {
 215         unsigned char *optptr = skb_network_header(skb) + sizeof(struct iphdr);
 216         struct ip_options *opt = &(IPCB(skb)->opt);
 217         int  l = opt->optlen;
 218         int  optlen;
 219
 220         while (l > 0) {
 221                 switch (*optptr) {
 222                 case IPOPT_END:
 223                         return;
 224                 case IPOPT_NOOP:
 225                         l--;
 226                         optptr++;
 227                         continue;
 228                 }
 229                 optlen = optptr[1];
 230                 if (optlen<2 || optlen>l)
 231                   return;
 232                 if (!IPOPT_COPIED(*optptr))
 233                         memset(optptr, IPOPT_NOOP, optlen);
 234                 l -= optlen;
 235                 optptr += optlen;
 236         }
 237         opt->ts = 0;
 238         opt->rr = 0;
 239         opt->rr_needaddr = 0;
 240         opt->ts_needaddr = 0;
 241         opt->ts_needtime = 0;
 242 }
 243
 244 /* helper used by ip_options_compile() to call fib_compute_spec_dst()
 245  * at most one time.
 246  */
 247 static void spec_dst_fill(__be32 *spec_dst, struct sk_buff *skb)
 248 {
 249         if (*spec_dst == htonl(INADDR_ANY))
 250                 *spec_dst = fib_compute_spec_dst(skb);
 251 }
 252
 253 /*
 254  * Verify options and fill pointers in struct options.
 255  * Caller should clear *opt, and set opt->data.
 256  * If opt == NULL, then skb->data should point to IP header.
 257  */
 258
 259 int ip_options_compile(struct net *net,
 260                        struct ip_options *opt, struct sk_buff *skb)
 261 {
 262         __be32 spec_dst = htonl(INADDR_ANY);
 263         unsigned char *pp_ptr = NULL;
 264         struct rtable *rt = NULL;
 265         unsigned char *optptr;
 266         unsigned char *iph;
 267         int optlen, l;
 268
 269         if (skb != NULL) {
 270                 rt = skb_rtable(skb);
 271                 optptr = (unsigned char *)&(ip_hdr(skb)[1]);
 272         } else
 273                 optptr = opt->__data;
 274         iph = optptr - sizeof(struct iphdr);
 275
 276         for (l = opt->optlen; l > 0; ) {
 277                 switch (*optptr) {
 278                       case IPOPT_END:
 279                         for (optptr++, l--; l>0; optptr++, l--) {
 280                                 if (*optptr != IPOPT_END) {
 281                                         *optptr = IPOPT_END;
 282                                         opt->is_changed = 1;
 283                                 }
 284                         }
 285                         goto eol;
 286                       case IPOPT_NOOP:
 287                         l--;
 288                         optptr++;
 289                         continue;
 290                 }
 291                 optlen = optptr[1];
 292                 if (optlen<2 || optlen>l) {
 293                         pp_ptr = optptr;
 294                         goto error;
 295                 }
 296                 switch (*optptr) {
 297                       case IPOPT_SSRR:
 298                       case IPOPT_LSRR:
 299                         if (optlen < 3) {
 300                                 pp_ptr = optptr + 1;
 301                                 goto error;
 302                         }
 303                         if (optptr[2] < 4) {
 304                                 pp_ptr = optptr + 2;
 305                                 goto error;
 306                         }
 307                         /* NB: cf RFC-1812 5.2.4.1 */
 308                         if (opt->srr) {
 309                                 pp_ptr = optptr;
 310                                 goto error;
 311                         }
 312                         if (!skb) {
 313                                 if (optptr[2] != 4 || optlen < 7 || ((optlen-3) & 3)) {
 314                                         pp_ptr = optptr + 1;
 315                                         goto error;
 316                                 }
 317                                 memcpy(&opt->faddr, &optptr[3], 4);
 318                                 if (optlen > 7)
 319                                         memmove(&optptr[3], &optptr[7], optlen-7);
 320                         }
 321                         opt->is_strictroute = (optptr[0] == IPOPT_SSRR);
 322                         opt->srr = optptr - iph;
 323                         break;
 324                       case IPOPT_RR:
 325                         if (opt->rr) {
 326                                 pp_ptr = optptr;
 327                                 goto error;
 328                         }
 329                         if (optlen < 3) {
 330                                 pp_ptr = optptr + 1;
 331                                 goto error;
 332                         }
 333                         if (optptr[2] < 4) {
 334                                 pp_ptr = optptr + 2;
 335                                 goto error;
 336                         }
 337                         if (optptr[2] <= optlen) {
 338                                 if (optptr[2]+3 > optlen) {
 339                                         pp_ptr = optptr + 2;
 340                                         goto error;
 341                                 }
 342                                 if (rt) {
 343                                         spec_dst_fill(&spec_dst, skb);
 344                                         memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
 345                                         opt->is_changed = 1;
 346                                 }
 347                                 optptr[2] += 4;
 348                                 opt->rr_needaddr = 1;
 349                         }
 350                         opt->rr = optptr - iph;
 351                         break;
 352                       case IPOPT_TIMESTAMP:
 353                         if (opt->ts) {
 354                                 pp_ptr = optptr;
 355                                 goto error;
 356                         }
 357                         if (optlen < 4) {
 358                                 pp_ptr = optptr + 1;
 359                                 goto error;
 360                         }
 361                         if (optptr[2] < 5) {
 362                                 pp_ptr = optptr + 2;
 363                                 goto error;
 364                         }
 365                         if (optptr[2] <= optlen) {
 366                                 unsigned char *timeptr = NULL;
 367                                 if (optptr[2]+3 > optptr[1]) {
 368                                         pp_ptr = optptr + 2;
 369                                         goto error;
 370                                 }
 371                                 switch (optptr[3]&0xF) {
 372                                       case IPOPT_TS_TSONLY:
 373                                         if (skb)
 374                                                 timeptr = &optptr[optptr[2]-1];
 375                                         opt->ts_needtime = 1;
 376                                         optptr[2] += 4;
 377                                         break;
 378                                       case IPOPT_TS_TSANDADDR:
 379                                         if (optptr[2]+7 > optptr[1]) {
 380                                                 pp_ptr = optptr + 2;
 381                                                 goto error;
 382                                         }
 383                                         if (rt)  {
 384                                                 spec_dst_fill(&spec_dst, skb);
 385                                                 memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
 386                                                 timeptr = &optptr[optptr[2]+3];
 387                                         }
 388                                         opt->ts_needaddr = 1;
 389                                         opt->ts_needtime = 1;
 390                                         optptr[2] += 8;
 391                                         break;
 392                                       case IPOPT_TS_PRESPEC:
 393                                         if (optptr[2]+7 > optptr[1]) {
 394                                                 pp_ptr = optptr + 2;
 395                                                 goto error;
 396                                         }
 397                                         {
 398                                                 __be32 addr;
 399                                                 memcpy(&addr, &optptr[optptr[2]-1], 4);
 400                                                 if (inet_addr_type(net, addr) == RTN_UNICAST)
 401                                                         break;
 402                                                 if (skb)
 403                                                         timeptr = &optptr[optptr[2]+3];
 404                                         }
 405                                         opt->ts_needtime = 1;
 406                                         optptr[2] += 8;
 407                                         break;
 408                                       default:
 409                                         if (!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) {
 410                                                 pp_ptr = optptr + 3;
 411                                                 goto error;
 412                                         }
 413                                         break;
 414                                 }
 415                                 if (timeptr) {
 416                                         struct timespec tv;
 417                                         u32  midtime;
 418                                         getnstimeofday(&tv);
 419                                         midtime = (tv.tv_sec % 86400) * MSEC_PER_SEC + tv.tv_nsec / NSEC_PER_MSEC;
 420                                         put_unaligned_be32(midtime, timeptr);
 421                                         opt->is_changed = 1;
 422                                 }
 423                         } else if ((optptr[3]&0xF) != IPOPT_TS_PRESPEC) {
 424                                 unsigned int overflow = optptr[3]>>4;
 425                                 if (overflow == 15) {
 426                                         pp_ptr = optptr + 3;
 427                                         goto error;
 428                                 }
 429                                 if (skb) {
 430                                         optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
 431                                         opt->is_changed = 1;
 432                                 }
 433                         }
 434                         opt->ts = optptr - iph;
 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 && !ns_capable(net->user_ns, CAP_NET_RAW)) || opt->cipso) {
 446                                 pp_ptr = optptr;
 447                                 goto error;
 448                         }
 449                         opt->cipso = optptr - iph;
 450                         if (cipso_v4_validate(skb, &optptr)) {
 451                                 pp_ptr = optptr;
 452                                 goto error;
 453                         }
 454                         break;
 455                       case IPOPT_SEC:
 456                       case IPOPT_SID:
 457                       default:
 458                         if (!skb && !ns_capable(net->user_ns, 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 EXPORT_SYMBOL(ip_options_compile);
 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_rcu *ip_options_get_alloc(const int optlen)
 512 {
 513         return kzalloc(sizeof(struct ip_options_rcu) + ((optlen + 3) & ~3),
 514                        GFP_KERNEL);
 515 }
 516
 517 static int ip_options_get_finish(struct net *net, struct ip_options_rcu **optp,
 518                                  struct ip_options_rcu *opt, int optlen)
 519 {
 520         while (optlen & 3)
 521                 opt->opt.__data[optlen++] = IPOPT_END;
 522         opt->opt.optlen = optlen;
 523         if (optlen && ip_options_compile(net, &opt->opt, NULL)) {
 524                 kfree(opt);
 525                 return -EINVAL;
 526         }
 527         kfree(*optp);
 528         *optp = opt;
 529         return 0;
 530 }
 531
 532 int ip_options_get_from_user(struct net *net, struct ip_options_rcu **optp,
 533                              unsigned char __user *data, int optlen)
 534 {
 535         struct ip_options_rcu *opt = ip_options_get_alloc(optlen);
 536
 537         if (!opt)
 538                 return -ENOMEM;
 539         if (optlen && copy_from_user(opt->opt.__data, data, optlen)) {
 540                 kfree(opt);
 541                 return -EFAULT;
 542         }
 543         return ip_options_get_finish(net, optp, opt, optlen);
 544 }
 545
 546 int ip_options_get(struct net *net, struct ip_options_rcu **optp,
 547                    unsigned char *data, int optlen)
 548 {
 549         struct ip_options_rcu *opt = ip_options_get_alloc(optlen);
 550
 551         if (!opt)
 552                 return -ENOMEM;
 553         if (optlen)
 554                 memcpy(opt->opt.__data, data, optlen);
 555         return ip_options_get_finish(net, optp, opt, optlen);
 556 }
 557
 558 void ip_forward_options(struct sk_buff *skb)
 559 {
 560         struct   ip_options *opt        = &(IPCB(skb)->opt);
 561         unsigned char *optptr;
 562         struct rtable *rt = skb_rtable(skb);
 563         unsigned char *raw = skb_network_header(skb);
 564
 565         if (opt->rr_needaddr) {
 566                 optptr = (unsigned char *)raw + opt->rr;
 567                 ip_rt_get_source(&optptr[optptr[2]-5], skb, rt);
 568                 opt->is_changed = 1;
 569         }
 570         if (opt->srr_is_hit) {
 571                 int srrptr, srrspace;
 572
 573                 optptr = raw + opt->srr;
 574
 575                 for ( srrptr=optptr[2], srrspace = optptr[1];
 576                      srrptr <= srrspace;
 577                      srrptr += 4
 578                      ) {
 579                         if (srrptr + 3 > srrspace)
 580                                 break;
 581                         if (memcmp(&opt->nexthop, &optptr[srrptr-1], 4) == 0)
 582                                 break;
 583                 }
 584                 if (srrptr + 3 <= srrspace) {
 585                         opt->is_changed = 1;
 586                         ip_hdr(skb)->daddr = opt->nexthop;
 587                         ip_rt_get_source(&optptr[srrptr-1], skb, rt);
 588                         optptr[2] = srrptr+4;
 589                 } else {
 590                         net_crit_ratelimited("%s(): Argh! Destination lost!\n",
 591                                              __func__);
 592                 }
 593                 if (opt->ts_needaddr) {
 594                         optptr = raw + opt->ts;
 595                         ip_rt_get_source(&optptr[optptr[2]-9], skb, rt);
 596                         opt->is_changed = 1;
 597                 }
 598         }
 599         if (opt->is_changed) {
 600                 opt->is_changed = 0;
 601                 ip_send_check(ip_hdr(skb));
 602         }
 603 }
 604
 605 int ip_options_rcv_srr(struct sk_buff *skb)
 606 {
 607         struct ip_options *opt = &(IPCB(skb)->opt);
 608         int srrspace, srrptr;
 609         __be32 nexthop;
 610         struct iphdr *iph = ip_hdr(skb);
 611         unsigned char *optptr = skb_network_header(skb) + opt->srr;
 612         struct rtable *rt = skb_rtable(skb);
 613         struct rtable *rt2;
 614         unsigned long orefdst;
 615         int err;
 616
 617         if (!rt)
 618                 return 0;
 619
 620         if (skb->pkt_type != PACKET_HOST)
 621                 return -EINVAL;
 622         if (rt->rt_type == RTN_UNICAST) {
 623                 if (!opt->is_strictroute)
 624                         return 0;
 625                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
 626                 return -EINVAL;
 627         }
 628         if (rt->rt_type != RTN_LOCAL)
 629                 return -EINVAL;
 630
 631         for (srrptr=optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
 632                 if (srrptr + 3 > srrspace) {
 633                         icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
 634                         return -EINVAL;
 635                 }
 636                 memcpy(&nexthop, &optptr[srrptr-1], 4);
 637
 638                 orefdst = skb->_skb_refdst;
 639                 skb_dst_set(skb, NULL);
 640                 err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, skb->dev);
 641                 rt2 = skb_rtable(skb);
 642                 if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
 643                         skb_dst_drop(skb);
 644                         skb->_skb_refdst = orefdst;
 645                         return -EINVAL;
 646                 }
 647                 refdst_drop(orefdst);
 648                 if (rt2->rt_type != RTN_LOCAL)
 649                         break;
 650                 /* Superfast 8) loopback forward */
 651                 iph->daddr = nexthop;
 652                 opt->is_changed = 1;
 653         }
 654         if (srrptr <= srrspace) {
 655                 opt->srr_is_hit = 1;
 656                 opt->nexthop = nexthop;
 657                 opt->is_changed = 1;
 658         }
 659         return 0;
 660 }
 661 EXPORT_SYMBOL(ip_options_rcv_srr);