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                         __be32 midtime;
  62
  63                         midtime = inet_current_timestamp();
  64                         memcpy(iph+opt->ts+iph[opt->ts+2]-5, &midtime, 4);
  65                 }
  66                 return;
  67         }
  68         if (opt->rr) {
  69                 memset(iph+opt->rr, IPOPT_NOP, iph[opt->rr+1]);
  70                 opt->rr = 0;
  71                 opt->rr_needaddr = 0;
  72         }
  73         if (opt->ts) {
  74                 memset(iph+opt->ts, IPOPT_NOP, iph[opt->ts+1]);
  75                 opt->ts = 0;
  76                 opt->ts_needaddr = opt->ts_needtime = 0;
  77         }
  78 }
  79
  80 /*
  81  * Provided (sopt, skb) points to received options,
  82  * build in dopt compiled option set appropriate for answering.
  83  * i.e. invert SRR option, copy anothers,
  84  * and grab room in RR/TS options.
  85  *
  86  * NOTE: dopt cannot point to skb.
  87  */
  88
  89 int __ip_options_echo(struct ip_options *dopt, struct sk_buff *skb,
  90                       const struct ip_options *sopt)
  91 {
  92         unsigned char *sptr, *dptr;
  93         int soffset, doffset;
  94         int     optlen;
  95
  96         memset(dopt, 0, sizeof(struct ip_options));
  97
  98         if (sopt->optlen == 0)
  99                 return 0;
 100
 101         sptr = skb_network_header(skb);
 102         dptr = dopt->__data;
 103
 104         if (sopt->rr) {
 105                 optlen  = sptr[sopt->rr+1];
 106                 soffset = sptr[sopt->rr+2];
 107                 dopt->rr = dopt->optlen + sizeof(struct iphdr);
 108                 memcpy(dptr, sptr+sopt->rr, optlen);
 109                 if (sopt->rr_needaddr && soffset <= optlen) {
 110                         if (soffset + 3 > optlen)
 111                                 return -EINVAL;
 112                         dptr[2] = soffset + 4;
 113                         dopt->rr_needaddr = 1;
 114                 }
 115                 dptr += optlen;
 116                 dopt->optlen += optlen;
 117         }
 118         if (sopt->ts) {
 119                 optlen = sptr[sopt->ts+1];
 120                 soffset = sptr[sopt->ts+2];
 121                 dopt->ts = dopt->optlen + sizeof(struct iphdr);
 122                 memcpy(dptr, sptr+sopt->ts, optlen);
 123                 if (soffset <= optlen) {
 124                         if (sopt->ts_needaddr) {
 125                                 if (soffset + 3 > optlen)
 126                                         return -EINVAL;
 127                                 dopt->ts_needaddr = 1;
 128                                 soffset += 4;
 129                         }
 130                         if (sopt->ts_needtime) {
 131                                 if (soffset + 3 > optlen)
 132                                         return -EINVAL;
 133                                 if ((dptr[3]&0xF) != IPOPT_TS_PRESPEC) {
 134                                         dopt->ts_needtime = 1;
 135                                         soffset += 4;
 136                                 } else {
 137                                         dopt->ts_needtime = 0;
 138
 139                                         if (soffset + 7 <= optlen) {
 140                                                 __be32 addr;
 141
 142                                                 memcpy(&addr, dptr+soffset-1, 4);
 143                                                 if (inet_addr_type(dev_net(skb_dst(skb)->dev), addr) != RTN_UNICAST) {
 144                                                         dopt->ts_needtime = 1;
 145                                                         soffset += 8;
 146                                                 }
 147                                         }
 148                                 }
 149                         }
 150                         dptr[2] = soffset;
 151                 }
 152                 dptr += optlen;
 153                 dopt->optlen += optlen;
 154         }
 155         if (sopt->srr) {
 156                 unsigned char *start = sptr+sopt->srr;
 157                 __be32 faddr;
 158
 159                 optlen  = start[1];
 160                 soffset = start[2];
 161                 doffset = 0;
 162                 if (soffset > optlen)
 163                         soffset = optlen + 1;
 164                 soffset -= 4;
 165                 if (soffset > 3) {
 166                         memcpy(&faddr, &start[soffset-1], 4);
 167                         for (soffset -= 4, doffset = 4; soffset > 3; soffset -= 4, doffset += 4)
 168                                 memcpy(&dptr[doffset-1], &start[soffset-1], 4);
 169                         /*
 170                          * RFC1812 requires to fix illegal source routes.
 171                          */
 172                         if (memcmp(&ip_hdr(skb)->saddr,
 173                                    &start[soffset + 3], 4) == 0)
 174                                 doffset -= 4;
 175                 }
 176                 if (doffset > 3) {
 177                         __be32 daddr = fib_compute_spec_dst(skb);
 178
 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 /* helper used by ip_options_compile() to call fib_compute_spec_dst()
 242  * at most one time.
 243  */
 244 static void spec_dst_fill(__be32 *spec_dst, struct sk_buff *skb)
 245 {
 246         if (*spec_dst == htonl(INADDR_ANY))
 247                 *spec_dst = fib_compute_spec_dst(skb);
 248 }
 249
 250 /*
 251  * Verify options and fill pointers in struct options.
 252  * Caller should clear *opt, and set opt->data.
 253  * If opt == NULL, then skb->data should point to IP header.
 254  */
 255
 256 int __ip_options_compile(struct net *net,
 257                          struct ip_options *opt, struct sk_buff *skb,
 258                          __be32 *info)
 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                                         __be32 midtime;
 419
 420                                         midtime = inet_current_timestamp();
 421                                         memcpy(timeptr, &midtime, 4);
 422                                         opt->is_changed = 1;
 423                                 }
 424                         } else if ((optptr[3]&0xF) != IPOPT_TS_PRESPEC) {
 425                                 unsigned int overflow = optptr[3]>>4;
 426                                 if (overflow == 15) {
 427                                         pp_ptr = optptr + 3;
 428                                         goto error;
 429                                 }
 430                                 if (skb) {
 431                                         optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
 432                                         opt->is_changed = 1;
 433                                 }
 434                         }
 435                         opt->ts = optptr - iph;
 436                         break;
 437                 case IPOPT_RA:
 438                         if (optlen < 4) {
 439                                 pp_ptr = optptr + 1;
 440                                 goto error;
 441                         }
 442                         if (optptr[2] == 0 && optptr[3] == 0)
 443                                 opt->router_alert = optptr - iph;
 444                         break;
 445                 case IPOPT_CIPSO:
 446                         if ((!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) || opt->cipso) {
 447                                 pp_ptr = optptr;
 448                                 goto error;
 449                         }
 450                         opt->cipso = optptr - iph;
 451                         if (cipso_v4_validate(skb, &optptr)) {
 452                                 pp_ptr = optptr;
 453                                 goto error;
 454                         }
 455                         break;
 456                 case IPOPT_SEC:
 457                 case IPOPT_SID:
 458                 default:
 459                         if (!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) {
 460                                 pp_ptr = optptr;
 461                                 goto error;
 462                         }
 463                         break;
 464                 }
 465                 l -= optlen;
 466                 optptr += optlen;
 467         }
 468
 469 eol:
 470         if (!pp_ptr)
 471                 return 0;
 472
 473 error:
 474         if (info)
 475                 *info = htonl((pp_ptr-iph)<<24);
 476         return -EINVAL;
 477 }
 478
 479 int ip_options_compile(struct net *net,
 480                        struct ip_options *opt, struct sk_buff *skb)
 481 {
 482         int ret;
 483         __be32 info;
 484
 485         ret = __ip_options_compile(net, opt, skb, &info);
 486         if (ret != 0 && skb)
 487                 icmp_send(skb, ICMP_PARAMETERPROB, 0, info);
 488         return ret;
 489 }
 490 EXPORT_SYMBOL(ip_options_compile);
 491
 492 /*
 493  *      Undo all the changes done by ip_options_compile().
 494  */
 495
 496 void ip_options_undo(struct ip_options *opt)
 497 {
 498         if (opt->srr) {
 499                 unsigned  char *optptr = opt->__data+opt->srr-sizeof(struct  iphdr);
 500                 memmove(optptr+7, optptr+3, optptr[1]-7);
 501                 memcpy(optptr+3, &opt->faddr, 4);
 502         }
 503         if (opt->rr_needaddr) {
 504                 unsigned  char *optptr = opt->__data+opt->rr-sizeof(struct  iphdr);
 505                 optptr[2] -= 4;
 506                 memset(&optptr[optptr[2]-1], 0, 4);
 507         }
 508         if (opt->ts) {
 509                 unsigned  char *optptr = opt->__data+opt->ts-sizeof(struct  iphdr);
 510                 if (opt->ts_needtime) {
 511                         optptr[2] -= 4;
 512                         memset(&optptr[optptr[2]-1], 0, 4);
 513                         if ((optptr[3]&0xF) == IPOPT_TS_PRESPEC)
 514                                 optptr[2] -= 4;
 515                 }
 516                 if (opt->ts_needaddr) {
 517                         optptr[2] -= 4;
 518                         memset(&optptr[optptr[2]-1], 0, 4);
 519                 }
 520         }
 521 }
 522
 523 static struct ip_options_rcu *ip_options_get_alloc(const int optlen)
 524 {
 525         return kzalloc(sizeof(struct ip_options_rcu) + ((optlen + 3) & ~3),
 526                        GFP_KERNEL);
 527 }
 528
 529 static int ip_options_get_finish(struct net *net, struct ip_options_rcu **optp,
 530                                  struct ip_options_rcu *opt, int optlen)
 531 {
 532         while (optlen & 3)
 533                 opt->opt.__data[optlen++] = IPOPT_END;
 534         opt->opt.optlen = optlen;
 535         if (optlen && ip_options_compile(net, &opt->opt, NULL)) {
 536                 kfree(opt);
 537                 return -EINVAL;
 538         }
 539         kfree(*optp);
 540         *optp = opt;
 541         return 0;
 542 }
 543
 544 int ip_options_get_from_user(struct net *net, struct ip_options_rcu **optp,
 545                              unsigned char __user *data, int optlen)
 546 {
 547         struct ip_options_rcu *opt = ip_options_get_alloc(optlen);
 548
 549         if (!opt)
 550                 return -ENOMEM;
 551         if (optlen && copy_from_user(opt->opt.__data, data, optlen)) {
 552                 kfree(opt);
 553                 return -EFAULT;
 554         }
 555         return ip_options_get_finish(net, optp, opt, optlen);
 556 }
 557
 558 int ip_options_get(struct net *net, struct ip_options_rcu **optp,
 559                    unsigned char *data, int optlen)
 560 {
 561         struct ip_options_rcu *opt = ip_options_get_alloc(optlen);
 562
 563         if (!opt)
 564                 return -ENOMEM;
 565         if (optlen)
 566                 memcpy(opt->opt.__data, data, optlen);
 567         return ip_options_get_finish(net, optp, opt, optlen);
 568 }
 569
 570 void ip_forward_options(struct sk_buff *skb)
 571 {
 572         struct   ip_options *opt        = &(IPCB(skb)->opt);
 573         unsigned char *optptr;
 574         struct rtable *rt = skb_rtable(skb);
 575         unsigned char *raw = skb_network_header(skb);
 576
 577         if (opt->rr_needaddr) {
 578                 optptr = (unsigned char *)raw + opt->rr;
 579                 ip_rt_get_source(&optptr[optptr[2]-5], skb, rt);
 580                 opt->is_changed = 1;
 581         }
 582         if (opt->srr_is_hit) {
 583                 int srrptr, srrspace;
 584
 585                 optptr = raw + opt->srr;
 586
 587                 for ( srrptr = optptr[2], srrspace = optptr[1];
 588                      srrptr <= srrspace;
 589                      srrptr += 4
 590                      ) {
 591                         if (srrptr + 3 > srrspace)
 592                                 break;
 593                         if (memcmp(&opt->nexthop, &optptr[srrptr-1], 4) == 0)
 594                                 break;
 595                 }
 596                 if (srrptr + 3 <= srrspace) {
 597                         opt->is_changed = 1;
 598                         ip_hdr(skb)->daddr = opt->nexthop;
 599                         ip_rt_get_source(&optptr[srrptr-1], skb, rt);
 600                         optptr[2] = srrptr+4;
 601                 } else {
 602                         net_crit_ratelimited("%s(): Argh! Destination lost!\n",
 603                                              __func__);
 604                 }
 605                 if (opt->ts_needaddr) {
 606                         optptr = raw + opt->ts;
 607                         ip_rt_get_source(&optptr[optptr[2]-9], skb, rt);
 608                         opt->is_changed = 1;
 609                 }
 610         }
 611         if (opt->is_changed) {
 612                 opt->is_changed = 0;
 613                 ip_send_check(ip_hdr(skb));
 614         }
 615 }
 616
 617 int ip_options_rcv_srr(struct sk_buff *skb, struct net_device *dev)
 618 {
 619         struct ip_options *opt = &(IPCB(skb)->opt);
 620         int srrspace, srrptr;
 621         __be32 nexthop;
 622         struct iphdr *iph = ip_hdr(skb);
 623         unsigned char *optptr = skb_network_header(skb) + opt->srr;
 624         struct rtable *rt = skb_rtable(skb);
 625         struct rtable *rt2;
 626         unsigned long orefdst;
 627         int err;
 628
 629         if (!rt)
 630                 return 0;
 631
 632         if (skb->pkt_type != PACKET_HOST)
 633                 return -EINVAL;
 634         if (rt->rt_type == RTN_UNICAST) {
 635                 if (!opt->is_strictroute)
 636                         return 0;
 637                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
 638                 return -EINVAL;
 639         }
 640         if (rt->rt_type != RTN_LOCAL)
 641                 return -EINVAL;
 642
 643         for (srrptr = optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
 644                 if (srrptr + 3 > srrspace) {
 645                         icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
 646                         return -EINVAL;
 647                 }
 648                 memcpy(&nexthop, &optptr[srrptr-1], 4);
 649
 650                 orefdst = skb->_skb_refdst;
 651                 skb_dst_set(skb, NULL);
 652                 err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, dev);
 653                 rt2 = skb_rtable(skb);
 654                 if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
 655                         skb_dst_drop(skb);
 656                         skb->_skb_refdst = orefdst;
 657                         return -EINVAL;
 658                 }
 659                 refdst_drop(orefdst);
 660                 if (rt2->rt_type != RTN_LOCAL)
 661                         break;
 662                 /* Superfast 8) loopback forward */
 663                 iph->daddr = nexthop;
 664                 opt->is_changed = 1;
 665         }
 666         if (srrptr <= srrspace) {
 667                 opt->srr_is_hit = 1;
 668                 opt->nexthop = nexthop;
 669                 opt->is_changed = 1;
 670         }
 671         return 0;
 672 }
 673 EXPORT_SYMBOL(ip_options_rcv_srr);