net/ipv4/ip_options.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   4  *              operating system.  INET is implemented using the  BSD Socket
   5  *              interface as the means of communication with the user level.
   6  *
   7  *              The options processing module for ip.c
   8  *
   9  * Authors:     A.N.Kuznetsov
  10  *
  11  */
  12
  13 #define pr_fmt(fmt) "IPv4: " fmt
  14
  15 #include <linux/capability.h>
  16 #include <linux/module.h>
  17 #include <linux/slab.h>
  18 #include <linux/types.h>
  19 #include <linux/uaccess.h>
  20 #include <asm/unaligned.h>
  21 #include <linux/skbuff.h>
  22 #include <linux/ip.h>
  23 #include <linux/icmp.h>
  24 #include <linux/netdevice.h>
  25 #include <linux/rtnetlink.h>
  26 #include <net/sock.h>
  27 #include <net/ip.h>
  28 #include <net/icmp.h>
  29 #include <net/route.h>
  30 #include <net/cipso_ipv4.h>
  31 #include <net/ip_fib.h>
  32
  33 /*
  34  * Write options to IP header, record destination address to
  35  * source route option, address of outgoing interface
  36  * (we should already know it, so that this  function is allowed be
  37  * called only after routing decision) and timestamp,
  38  * if we originate this datagram.
  39  *
  40  * daddr is real destination address, next hop is recorded in IP header.
  41  * saddr is address of outgoing interface.
  42  */
  43
  44 void ip_options_build(struct sk_buff *skb, struct ip_options *opt,
  45                       __be32 daddr, struct rtable *rt, int is_frag)
  46 {
  47         unsigned char *iph = skb_network_header(skb);
  48
  49         memcpy(&(IPCB(skb)->opt), opt, sizeof(struct ip_options));
  50         memcpy(iph+sizeof(struct iphdr), opt->__data, opt->optlen);
  51         opt = &(IPCB(skb)->opt);
  52
  53         if (opt->srr)
  54                 memcpy(iph+opt->srr+iph[opt->srr+1]-4, &daddr, 4);
  55
  56         if (!is_frag) {
  57                 if (opt->rr_needaddr)
  58                         ip_rt_get_source(iph+opt->rr+iph[opt->rr+2]-5, skb, rt);
  59                 if (opt->ts_needaddr)
  60                         ip_rt_get_source(iph+opt->ts+iph[opt->ts+2]-9, skb, rt);
  61                 if (opt->ts_needtime) {
  62                         __be32 midtime;
  63
  64                         midtime = inet_current_timestamp();
  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 net *net, struct ip_options *dopt,
  91                       struct sk_buff *skb, 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(net, 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                         dopt->faddr = faddr;
 179                         dptr[0] = start[0];
 180                         dptr[1] = doffset+3;
 181                         dptr[2] = 4;
 182                         dptr += doffset+3;
 183                         dopt->srr = dopt->optlen + sizeof(struct iphdr);
 184                         dopt->optlen += doffset+3;
 185                         dopt->is_strictroute = sopt->is_strictroute;
 186                 }
 187         }
 188         if (sopt->cipso) {
 189                 optlen  = sptr[sopt->cipso+1];
 190                 dopt->cipso = dopt->optlen+sizeof(struct iphdr);
 191                 memcpy(dptr, sptr+sopt->cipso, optlen);
 192                 dptr += optlen;
 193                 dopt->optlen += optlen;
 194         }
 195         while (dopt->optlen & 3) {
 196                 *dptr++ = IPOPT_END;
 197                 dopt->optlen++;
 198         }
 199         return 0;
 200 }
 201
 202 /*
 203  *      Options "fragmenting", just fill options not
 204  *      allowed in fragments with NOOPs.
 205  *      Simple and stupid 8), but the most efficient way.
 206  */
 207
 208 void ip_options_fragment(struct sk_buff *skb)
 209 {
 210         unsigned char *optptr = skb_network_header(skb) + sizeof(struct iphdr);
 211         struct ip_options *opt = &(IPCB(skb)->opt);
 212         int  l = opt->optlen;
 213         int  optlen;
 214
 215         while (l > 0) {
 216                 switch (*optptr) {
 217                 case IPOPT_END:
 218                         return;
 219                 case IPOPT_NOOP:
 220                         l--;
 221                         optptr++;
 222                         continue;
 223                 }
 224                 optlen = optptr[1];
 225                 if (optlen < 2 || optlen > l)
 226                   return;
 227                 if (!IPOPT_COPIED(*optptr))
 228                         memset(optptr, IPOPT_NOOP, optlen);
 229                 l -= optlen;
 230                 optptr += optlen;
 231         }
 232         opt->ts = 0;
 233         opt->rr = 0;
 234         opt->rr_needaddr = 0;
 235         opt->ts_needaddr = 0;
 236         opt->ts_needtime = 0;
 237 }
 238
 239 /* helper used by ip_options_compile() to call fib_compute_spec_dst()
 240  * at most one time.
 241  */
 242 static void spec_dst_fill(__be32 *spec_dst, struct sk_buff *skb)
 243 {
 244         if (*spec_dst == htonl(INADDR_ANY))
 245                 *spec_dst = fib_compute_spec_dst(skb);
 246 }
 247
 248 /*
 249  * Verify options and fill pointers in struct options.
 250  * Caller should clear *opt, and set opt->data.
 251  * If opt == NULL, then skb->data should point to IP header.
 252  */
 253
 254 int __ip_options_compile(struct net *net,
 255                          struct ip_options *opt, struct sk_buff *skb,
 256                          __be32 *info)
 257 {
 258         __be32 spec_dst = htonl(INADDR_ANY);
 259         unsigned char *pp_ptr = NULL;
 260         struct rtable *rt = NULL;
 261         unsigned char *optptr;
 262         unsigned char *iph;
 263         int optlen, l;
 264
 265         if (skb) {
 266                 rt = skb_rtable(skb);
 267                 optptr = (unsigned char *)&(ip_hdr(skb)[1]);
 268         } else
 269                 optptr = opt->__data;
 270         iph = optptr - sizeof(struct iphdr);
 271
 272         for (l = opt->optlen; l > 0; ) {
 273                 switch (*optptr) {
 274                 case IPOPT_END:
 275                         for (optptr++, l--; l > 0; optptr++, l--) {
 276                                 if (*optptr != IPOPT_END) {
 277                                         *optptr = IPOPT_END;
 278                                         opt->is_changed = 1;
 279                                 }
 280                         }
 281                         goto eol;
 282                 case IPOPT_NOOP:
 283                         l--;
 284                         optptr++;
 285                         continue;
 286                 }
 287                 if (unlikely(l < 2)) {
 288                         pp_ptr = optptr;
 289                         goto error;
 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 > optlen) {
 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 > optlen) {
 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 > optlen) {
 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                                         __be32 midtime;
 417
 418                                         midtime = inet_current_timestamp();
 419                                         memcpy(timeptr, &midtime, 4);
 420                                         opt->is_changed = 1;
 421                                 }
 422                         } else if ((optptr[3]&0xF) != IPOPT_TS_PRESPEC) {
 423                                 unsigned int overflow = optptr[3]>>4;
 424                                 if (overflow == 15) {
 425                                         pp_ptr = optptr + 3;
 426                                         goto error;
 427                                 }
 428                                 if (skb) {
 429                                         optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
 430                                         opt->is_changed = 1;
 431                                 }
 432                         }
 433                         opt->ts = optptr - iph;
 434                         break;
 435                 case IPOPT_RA:
 436                         if (optlen < 4) {
 437                                 pp_ptr = optptr + 1;
 438                                 goto error;
 439                         }
 440                         if (optptr[2] == 0 && optptr[3] == 0)
 441                                 opt->router_alert = optptr - iph;
 442                         break;
 443                 case IPOPT_CIPSO:
 444                         if ((!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) || opt->cipso) {
 445                                 pp_ptr = optptr;
 446                                 goto error;
 447                         }
 448                         opt->cipso = optptr - iph;
 449                         if (cipso_v4_validate(skb, &optptr)) {
 450                                 pp_ptr = optptr;
 451                                 goto error;
 452                         }
 453                         break;
 454                 case IPOPT_SEC:
 455                 case IPOPT_SID:
 456                 default:
 457                         if (!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) {
 458                                 pp_ptr = optptr;
 459                                 goto error;
 460                         }
 461                         break;
 462                 }
 463                 l -= optlen;
 464                 optptr += optlen;
 465         }
 466
 467 eol:
 468         if (!pp_ptr)
 469                 return 0;
 470
 471 error:
 472         if (info)
 473                 *info = htonl((pp_ptr-iph)<<24);
 474         return -EINVAL;
 475 }
 476 EXPORT_SYMBOL(__ip_options_compile);
 477
 478 int ip_options_compile(struct net *net,
 479                        struct ip_options *opt, struct sk_buff *skb)
 480 {
 481         int ret;
 482         __be32 info;
 483
 484         ret = __ip_options_compile(net, opt, skb, &info);
 485         if (ret != 0 && skb)
 486                 icmp_send(skb, ICMP_PARAMETERPROB, 0, info);
 487         return ret;
 488 }
 489 EXPORT_SYMBOL(ip_options_compile);
 490
 491 /*
 492  *      Undo all the changes done by ip_options_compile().
 493  */
 494
 495 void ip_options_undo(struct ip_options *opt)
 496 {
 497         if (opt->srr) {
 498                 unsigned  char *optptr = opt->__data+opt->srr-sizeof(struct  iphdr);
 499                 memmove(optptr+7, optptr+3, optptr[1]-7);
 500                 memcpy(optptr+3, &opt->faddr, 4);
 501         }
 502         if (opt->rr_needaddr) {
 503                 unsigned  char *optptr = opt->__data+opt->rr-sizeof(struct  iphdr);
 504                 optptr[2] -= 4;
 505                 memset(&optptr[optptr[2]-1], 0, 4);
 506         }
 507         if (opt->ts) {
 508                 unsigned  char *optptr = opt->__data+opt->ts-sizeof(struct  iphdr);
 509                 if (opt->ts_needtime) {
 510                         optptr[2] -= 4;
 511                         memset(&optptr[optptr[2]-1], 0, 4);
 512                         if ((optptr[3]&0xF) == IPOPT_TS_PRESPEC)
 513                                 optptr[2] -= 4;
 514                 }
 515                 if (opt->ts_needaddr) {
 516                         optptr[2] -= 4;
 517                         memset(&optptr[optptr[2]-1], 0, 4);
 518                 }
 519         }
 520 }
 521
 522 int ip_options_get(struct net *net, struct ip_options_rcu **optp,
 523                    sockptr_t data, int optlen)
 524 {
 525         struct ip_options_rcu *opt;
 526
 527         opt = kzalloc(sizeof(struct ip_options_rcu) + ((optlen + 3) & ~3),
 528                        GFP_KERNEL);
 529         if (!opt)
 530                 return -ENOMEM;
 531         if (optlen && copy_from_sockptr(opt->opt.__data, data, optlen)) {
 532                 kfree(opt);
 533                 return -EFAULT;
 534         }
 535
 536         while (optlen & 3)
 537                 opt->opt.__data[optlen++] = IPOPT_END;
 538         opt->opt.optlen = optlen;
 539         if (optlen && ip_options_compile(net, &opt->opt, NULL)) {
 540                 kfree(opt);
 541                 return -EINVAL;
 542         }
 543         kfree(*optp);
 544         *optp = opt;
 545         return 0;
 546 }
 547
 548 void ip_forward_options(struct sk_buff *skb)
 549 {
 550         struct   ip_options *opt        = &(IPCB(skb)->opt);
 551         unsigned char *optptr;
 552         struct rtable *rt = skb_rtable(skb);
 553         unsigned char *raw = skb_network_header(skb);
 554
 555         if (opt->rr_needaddr) {
 556                 optptr = (unsigned char *)raw + opt->rr;
 557                 ip_rt_get_source(&optptr[optptr[2]-5], skb, rt);
 558                 opt->is_changed = 1;
 559         }
 560         if (opt->srr_is_hit) {
 561                 int srrptr, srrspace;
 562
 563                 optptr = raw + opt->srr;
 564
 565                 for ( srrptr = optptr[2], srrspace = optptr[1];
 566                      srrptr <= srrspace;
 567                      srrptr += 4
 568                      ) {
 569                         if (srrptr + 3 > srrspace)
 570                                 break;
 571                         if (memcmp(&opt->nexthop, &optptr[srrptr-1], 4) == 0)
 572                                 break;
 573                 }
 574                 if (srrptr + 3 <= srrspace) {
 575                         opt->is_changed = 1;
 576                         ip_hdr(skb)->daddr = opt->nexthop;
 577                         ip_rt_get_source(&optptr[srrptr-1], skb, rt);
 578                         optptr[2] = srrptr+4;
 579                 } else {
 580                         net_crit_ratelimited("%s(): Argh! Destination lost!\n",
 581                                              __func__);
 582                 }
 583                 if (opt->ts_needaddr) {
 584                         optptr = raw + opt->ts;
 585                         ip_rt_get_source(&optptr[optptr[2]-9], skb, rt);
 586                         opt->is_changed = 1;
 587                 }
 588         }
 589         if (opt->is_changed) {
 590                 opt->is_changed = 0;
 591                 ip_send_check(ip_hdr(skb));
 592         }
 593 }
 594
 595 int ip_options_rcv_srr(struct sk_buff *skb, struct net_device *dev)
 596 {
 597         struct ip_options *opt = &(IPCB(skb)->opt);
 598         int srrspace, srrptr;
 599         __be32 nexthop;
 600         struct iphdr *iph = ip_hdr(skb);
 601         unsigned char *optptr = skb_network_header(skb) + opt->srr;
 602         struct rtable *rt = skb_rtable(skb);
 603         struct rtable *rt2;
 604         unsigned long orefdst;
 605         int err;
 606
 607         if (!rt)
 608                 return 0;
 609
 610         if (skb->pkt_type != PACKET_HOST)
 611                 return -EINVAL;
 612         if (rt->rt_type == RTN_UNICAST) {
 613                 if (!opt->is_strictroute)
 614                         return 0;
 615                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
 616                 return -EINVAL;
 617         }
 618         if (rt->rt_type != RTN_LOCAL)
 619                 return -EINVAL;
 620
 621         for (srrptr = optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
 622                 if (srrptr + 3 > srrspace) {
 623                         icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
 624                         return -EINVAL;
 625                 }
 626                 memcpy(&nexthop, &optptr[srrptr-1], 4);
 627
 628                 orefdst = skb->_skb_refdst;
 629                 skb_dst_set(skb, NULL);
 630                 err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, dev);
 631                 rt2 = skb_rtable(skb);
 632                 if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
 633                         skb_dst_drop(skb);
 634                         skb->_skb_refdst = orefdst;
 635                         return -EINVAL;
 636                 }
 637                 refdst_drop(orefdst);
 638                 if (rt2->rt_type != RTN_LOCAL)
 639                         break;
 640                 /* Superfast 8) loopback forward */
 641                 iph->daddr = nexthop;
 642                 opt->is_changed = 1;
 643         }
 644         if (srrptr <= srrspace) {
 645                 opt->srr_is_hit = 1;
 646                 opt->nexthop = nexthop;
 647                 opt->is_changed = 1;
 648         }
 649         return 0;
 650 }
 651 EXPORT_SYMBOL(ip_options_rcv_srr);