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  * Version:     $Id: ip_options.c,v 1.21 2001/09/01 00:31:50 davem Exp $
   9  *
  10  * Authors:     A.N.Kuznetsov
  11  *
  12  */
  13
  14 #include <linux/module.h>
  15 #include <linux/types.h>
  16 #include <asm/uaccess.h>
  17 #include <linux/skbuff.h>
  18 #include <linux/ip.h>
  19 #include <linux/icmp.h>
  20 #include <linux/netdevice.h>
  21 #include <linux/rtnetlink.h>
  22 #include <net/sock.h>
  23 #include <net/ip.h>
  24 #include <net/icmp.h>
  25
  26 /*
  27  * Write options to IP header, record destination address to
  28  * source route option, address of outgoing interface
  29  * (we should already know it, so that this  function is allowed be
  30  * called only after routing decision) and timestamp,
  31  * if we originate this datagram.
  32  *
  33  * daddr is real destination address, next hop is recorded in IP header.
  34  * saddr is address of outgoing interface.
  35  */
  36
  37 void ip_options_build(struct sk_buff * skb, struct ip_options * opt,
  38                             u32 daddr, struct rtable *rt, int is_frag)
  39 {
  40         unsigned char * iph = skb->nh.raw;
  41
  42         memcpy(&(IPCB(skb)->opt), opt, sizeof(struct ip_options));
  43         memcpy(iph+sizeof(struct iphdr), opt->__data, opt->optlen);
  44         opt = &(IPCB(skb)->opt);
  45         opt->is_data = 0;
  46
  47         if (opt->srr)
  48                 memcpy(iph+opt->srr+iph[opt->srr+1]-4, &daddr, 4);
  49
  50         if (!is_frag) {
  51                 if (opt->rr_needaddr)
  52                         ip_rt_get_source(iph+opt->rr+iph[opt->rr+2]-5, rt);
  53                 if (opt->ts_needaddr)
  54                         ip_rt_get_source(iph+opt->ts+iph[opt->ts+2]-9, rt);
  55                 if (opt->ts_needtime) {
  56                         struct timeval tv;
  57                         __u32 midtime;
  58                         do_gettimeofday(&tv);
  59                         midtime = htonl((tv.tv_sec % 86400) * 1000 + tv.tv_usec / 1000);
  60                         memcpy(iph+opt->ts+iph[opt->ts+2]-5, &midtime, 4);
  61                 }
  62                 return;
  63         }
  64         if (opt->rr) {
  65                 memset(iph+opt->rr, IPOPT_NOP, iph[opt->rr+1]);
  66                 opt->rr = 0;
  67                 opt->rr_needaddr = 0;
  68         }
  69         if (opt->ts) {
  70                 memset(iph+opt->ts, IPOPT_NOP, iph[opt->ts+1]);
  71                 opt->ts = 0;
  72                 opt->ts_needaddr = opt->ts_needtime = 0;
  73         }
  74 }
  75
  76 /*
  77  * Provided (sopt, skb) points to received options,
  78  * build in dopt compiled option set appropriate for answering.
  79  * i.e. invert SRR option, copy anothers,
  80  * and grab room in RR/TS options.
  81  *
  82  * NOTE: dopt cannot point to skb.
  83  */
  84
  85 int ip_options_echo(struct ip_options * dopt, struct sk_buff * skb)
  86 {
  87         struct ip_options *sopt;
  88         unsigned char *sptr, *dptr;
  89         int soffset, doffset;
  90         int     optlen;
  91         u32     daddr;
  92
  93         memset(dopt, 0, sizeof(struct ip_options));
  94
  95         dopt->is_data = 1;
  96
  97         sopt = &(IPCB(skb)->opt);
  98
  99         if (sopt->optlen == 0) {
 100                 dopt->optlen = 0;
 101                 return 0;
 102         }
 103
 104         sptr = skb->nh.raw;
 105         dptr = dopt->__data;
 106
 107         if (skb->dst)
 108                 daddr = ((struct rtable*)skb->dst)->rt_spec_dst;
 109         else
 110                 daddr = skb->nh.iph->daddr;
 111
 112         if (sopt->rr) {
 113                 optlen  = sptr[sopt->rr+1];
 114                 soffset = sptr[sopt->rr+2];
 115                 dopt->rr = dopt->optlen + sizeof(struct iphdr);
 116                 memcpy(dptr, sptr+sopt->rr, optlen);
 117                 if (sopt->rr_needaddr && soffset <= optlen) {
 118                         if (soffset + 3 > optlen)
 119                                 return -EINVAL;
 120                         dptr[2] = soffset + 4;
 121                         dopt->rr_needaddr = 1;
 122                 }
 123                 dptr += optlen;
 124                 dopt->optlen += optlen;
 125         }
 126         if (sopt->ts) {
 127                 optlen = sptr[sopt->ts+1];
 128                 soffset = sptr[sopt->ts+2];
 129                 dopt->ts = dopt->optlen + sizeof(struct iphdr);
 130                 memcpy(dptr, sptr+sopt->ts, optlen);
 131                 if (soffset <= optlen) {
 132                         if (sopt->ts_needaddr) {
 133                                 if (soffset + 3 > optlen)
 134                                         return -EINVAL;
 135                                 dopt->ts_needaddr = 1;
 136                                 soffset += 4;
 137                         }
 138                         if (sopt->ts_needtime) {
 139                                 if (soffset + 3 > optlen)
 140                                         return -EINVAL;
 141                                 if ((dptr[3]&0xF) != IPOPT_TS_PRESPEC) {
 142                                         dopt->ts_needtime = 1;
 143                                         soffset += 4;
 144                                 } else {
 145                                         dopt->ts_needtime = 0;
 146
 147                                         if (soffset + 8 <= optlen) {
 148                                                 __u32 addr;
 149
 150                                                 memcpy(&addr, sptr+soffset-1, 4);
 151                                                 if (inet_addr_type(addr) != RTN_LOCAL) {
 152                                                         dopt->ts_needtime = 1;
 153                                                         soffset += 8;
 154                                                 }
 155                                         }
 156                                 }
 157                         }
 158                         dptr[2] = soffset;
 159                 }
 160                 dptr += optlen;
 161                 dopt->optlen += optlen;
 162         }
 163         if (sopt->srr) {
 164                 unsigned char * start = sptr+sopt->srr;
 165                 u32 faddr;
 166
 167                 optlen  = start[1];
 168                 soffset = start[2];
 169                 doffset = 0;
 170                 if (soffset > optlen)
 171                         soffset = optlen + 1;
 172                 soffset -= 4;
 173                 if (soffset > 3) {
 174                         memcpy(&faddr, &start[soffset-1], 4);
 175                         for (soffset-=4, doffset=4; soffset > 3; soffset-=4, doffset+=4)
 176                                 memcpy(&dptr[doffset-1], &start[soffset-1], 4);
 177                         /*
 178                          * RFC1812 requires to fix illegal source routes.
 179                          */
 180                         if (memcmp(&skb->nh.iph->saddr, &start[soffset+3], 4) == 0)
 181                                 doffset -= 4;
 182                 }
 183                 if (doffset > 3) {
 184                         memcpy(&start[doffset-1], &daddr, 4);
 185                         dopt->faddr = faddr;
 186                         dptr[0] = start[0];
 187                         dptr[1] = doffset+3;
 188                         dptr[2] = 4;
 189                         dptr += doffset+3;
 190                         dopt->srr = dopt->optlen + sizeof(struct iphdr);
 191                         dopt->optlen += doffset+3;
 192                         dopt->is_strictroute = sopt->is_strictroute;
 193                 }
 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->nh.raw;
 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         return;
 238 }
 239
 240 /*
 241  * Verify options and fill pointers in struct options.
 242  * Caller should clear *opt, and set opt->data.
 243  * If opt == NULL, then skb->data should point to IP header.
 244  */
 245
 246 int ip_options_compile(struct ip_options * opt, struct sk_buff * skb)
 247 {
 248         int l;
 249         unsigned char * iph;
 250         unsigned char * optptr;
 251         int optlen;
 252         unsigned char * pp_ptr = NULL;
 253         struct rtable *rt = skb ? (struct rtable*)skb->dst : NULL;
 254
 255         if (!opt) {
 256                 opt = &(IPCB(skb)->opt);
 257                 memset(opt, 0, sizeof(struct ip_options));
 258                 iph = skb->nh.raw;
 259                 opt->optlen = ((struct iphdr *)iph)->ihl*4 - sizeof(struct iphdr);
 260                 optptr = iph + sizeof(struct iphdr);
 261                 opt->is_data = 0;
 262         } else {
 263                 optptr = opt->is_data ? opt->__data : (unsigned char*)&(skb->nh.iph[1]);
 264                 iph = optptr - sizeof(struct iphdr);
 265         }
 266
 267         for (l = opt->optlen; l > 0; ) {
 268                 switch (*optptr) {
 269                       case IPOPT_END:
 270                         for (optptr++, l--; l>0; optptr++, l--) {
 271                                 if (*optptr != IPOPT_END) {
 272                                         *optptr = IPOPT_END;
 273                                         opt->is_changed = 1;
 274                                 }
 275                         }
 276                         goto eol;
 277                       case IPOPT_NOOP:
 278                         l--;
 279                         optptr++;
 280                         continue;
 281                 }
 282                 optlen = optptr[1];
 283                 if (optlen<2 || optlen>l) {
 284                         pp_ptr = optptr;
 285                         goto error;
 286                 }
 287                 switch (*optptr) {
 288                       case IPOPT_SSRR:
 289                       case IPOPT_LSRR:
 290                         if (optlen < 3) {
 291                                 pp_ptr = optptr + 1;
 292                                 goto error;
 293                         }
 294                         if (optptr[2] < 4) {
 295                                 pp_ptr = optptr + 2;
 296                                 goto error;
 297                         }
 298                         /* NB: cf RFC-1812 5.2.4.1 */
 299                         if (opt->srr) {
 300                                 pp_ptr = optptr;
 301                                 goto error;
 302                         }
 303                         if (!skb) {
 304                                 if (optptr[2] != 4 || optlen < 7 || ((optlen-3) & 3)) {
 305                                         pp_ptr = optptr + 1;
 306                                         goto error;
 307                                 }
 308                                 memcpy(&opt->faddr, &optptr[3], 4);
 309                                 if (optlen > 7)
 310                                         memmove(&optptr[3], &optptr[7], optlen-7);
 311                         }
 312                         opt->is_strictroute = (optptr[0] == IPOPT_SSRR);
 313                         opt->srr = optptr - iph;
 314                         break;
 315                       case IPOPT_RR:
 316                         if (opt->rr) {
 317                                 pp_ptr = optptr;
 318                                 goto error;
 319                         }
 320                         if (optlen < 3) {
 321                                 pp_ptr = optptr + 1;
 322                                 goto error;
 323                         }
 324                         if (optptr[2] < 4) {
 325                                 pp_ptr = optptr + 2;
 326                                 goto error;
 327                         }
 328                         if (optptr[2] <= optlen) {
 329                                 if (optptr[2]+3 > optlen) {
 330                                         pp_ptr = optptr + 2;
 331                                         goto error;
 332                                 }
 333                                 if (skb) {
 334                                         memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
 335                                         opt->is_changed = 1;
 336                                 }
 337                                 optptr[2] += 4;
 338                                 opt->rr_needaddr = 1;
 339                         }
 340                         opt->rr = optptr - iph;
 341                         break;
 342                       case IPOPT_TIMESTAMP:
 343                         if (opt->ts) {
 344                                 pp_ptr = optptr;
 345                                 goto error;
 346                         }
 347                         if (optlen < 4) {
 348                                 pp_ptr = optptr + 1;
 349                                 goto error;
 350                         }
 351                         if (optptr[2] < 5) {
 352                                 pp_ptr = optptr + 2;
 353                                 goto error;
 354                         }
 355                         if (optptr[2] <= optlen) {
 356                                 __u32 * timeptr = NULL;
 357                                 if (optptr[2]+3 > optptr[1]) {
 358                                         pp_ptr = optptr + 2;
 359                                         goto error;
 360                                 }
 361                                 switch (optptr[3]&0xF) {
 362                                       case IPOPT_TS_TSONLY:
 363                                         opt->ts = optptr - iph;
 364                                         if (skb)
 365                                                 timeptr = (__u32*)&optptr[optptr[2]-1];
 366                                         opt->ts_needtime = 1;
 367                                         optptr[2] += 4;
 368                                         break;
 369                                       case IPOPT_TS_TSANDADDR:
 370                                         if (optptr[2]+7 > optptr[1]) {
 371                                                 pp_ptr = optptr + 2;
 372                                                 goto error;
 373                                         }
 374                                         opt->ts = optptr - iph;
 375                                         if (skb) {
 376                                                 memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
 377                                                 timeptr = (__u32*)&optptr[optptr[2]+3];
 378                                         }
 379                                         opt->ts_needaddr = 1;
 380                                         opt->ts_needtime = 1;
 381                                         optptr[2] += 8;
 382                                         break;
 383                                       case IPOPT_TS_PRESPEC:
 384                                         if (optptr[2]+7 > optptr[1]) {
 385                                                 pp_ptr = optptr + 2;
 386                                                 goto error;
 387                                         }
 388                                         opt->ts = optptr - iph;
 389                                         {
 390                                                 u32 addr;
 391                                                 memcpy(&addr, &optptr[optptr[2]-1], 4);
 392                                                 if (inet_addr_type(addr) == RTN_UNICAST)
 393                                                         break;
 394                                                 if (skb)
 395                                                         timeptr = (__u32*)&optptr[optptr[2]+3];
 396                                         }
 397                                         opt->ts_needtime = 1;
 398                                         optptr[2] += 8;
 399                                         break;
 400                                       default:
 401                                         if (!skb && !capable(CAP_NET_RAW)) {
 402                                                 pp_ptr = optptr + 3;
 403                                                 goto error;
 404                                         }
 405                                         break;
 406                                 }
 407                                 if (timeptr) {
 408                                         struct timeval tv;
 409                                         __u32  midtime;
 410                                         do_gettimeofday(&tv);
 411                                         midtime = htonl((tv.tv_sec % 86400) * 1000 + tv.tv_usec / 1000);
 412                                         memcpy(timeptr, &midtime, sizeof(__u32));
 413                                         opt->is_changed = 1;
 414                                 }
 415                         } else {
 416                                 unsigned overflow = optptr[3]>>4;
 417                                 if (overflow == 15) {
 418                                         pp_ptr = optptr + 3;
 419                                         goto error;
 420                                 }
 421                                 opt->ts = optptr - iph;
 422                                 if (skb) {
 423                                         optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
 424                                         opt->is_changed = 1;
 425                                 }
 426                         }
 427                         break;
 428                       case IPOPT_RA:
 429                         if (optlen < 4) {
 430                                 pp_ptr = optptr + 1;
 431                                 goto error;
 432                         }
 433                         if (optptr[2] == 0 && optptr[3] == 0)
 434                                 opt->router_alert = optptr - iph;
 435                         break;
 436                       case IPOPT_SEC:
 437                       case IPOPT_SID:
 438                       default:
 439                         if (!skb && !capable(CAP_NET_RAW)) {
 440                                 pp_ptr = optptr;
 441                                 goto error;
 442                         }
 443                         break;
 444                 }
 445                 l -= optlen;
 446                 optptr += optlen;
 447         }
 448
 449 eol:
 450         if (!pp_ptr)
 451                 return 0;
 452
 453 error:
 454         if (skb) {
 455                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((pp_ptr-iph)<<24));
 456         }
 457         return -EINVAL;
 458 }
 459
 460
 461 /*
 462  *      Undo all the changes done by ip_options_compile().
 463  */
 464
 465 void ip_options_undo(struct ip_options * opt)
 466 {
 467         if (opt->srr) {
 468                 unsigned  char * optptr = opt->__data+opt->srr-sizeof(struct  iphdr);
 469                 memmove(optptr+7, optptr+3, optptr[1]-7);
 470                 memcpy(optptr+3, &opt->faddr, 4);
 471         }
 472         if (opt->rr_needaddr) {
 473                 unsigned  char * optptr = opt->__data+opt->rr-sizeof(struct  iphdr);
 474                 optptr[2] -= 4;
 475                 memset(&optptr[optptr[2]-1], 0, 4);
 476         }
 477         if (opt->ts) {
 478                 unsigned  char * optptr = opt->__data+opt->ts-sizeof(struct  iphdr);
 479                 if (opt->ts_needtime) {
 480                         optptr[2] -= 4;
 481                         memset(&optptr[optptr[2]-1], 0, 4);
 482                         if ((optptr[3]&0xF) == IPOPT_TS_PRESPEC)
 483                                 optptr[2] -= 4;
 484                 }
 485                 if (opt->ts_needaddr) {
 486                         optptr[2] -= 4;
 487                         memset(&optptr[optptr[2]-1], 0, 4);
 488                 }
 489         }
 490 }
 491
 492 int ip_options_get(struct ip_options **optp, unsigned char *data, int optlen, int user)
 493 {
 494         struct ip_options *opt;
 495
 496         opt = kmalloc(sizeof(struct ip_options)+((optlen+3)&~3), GFP_KERNEL);
 497         if (!opt)
 498                 return -ENOMEM;
 499         memset(opt, 0, sizeof(struct ip_options));
 500         if (optlen) {
 501                 if (user) {
 502                         if (copy_from_user(opt->__data, data, optlen)) {
 503                                 kfree(opt);
 504                                 return -EFAULT;
 505                         }
 506                 } else
 507                         memcpy(opt->__data, data, optlen);
 508         }
 509         while (optlen & 3)
 510                 opt->__data[optlen++] = IPOPT_END;
 511         opt->optlen = optlen;
 512         opt->is_data = 1;
 513         opt->is_setbyuser = 1;
 514         if (optlen && ip_options_compile(opt, NULL)) {
 515                 kfree(opt);
 516                 return -EINVAL;
 517         }
 518         *optp = opt;
 519         return 0;
 520 }
 521
 522 void ip_forward_options(struct sk_buff *skb)
 523 {
 524         struct   ip_options * opt       = &(IPCB(skb)->opt);
 525         unsigned char * optptr;
 526         struct rtable *rt = (struct rtable*)skb->dst;
 527         unsigned char *raw = skb->nh.raw;
 528
 529         if (opt->rr_needaddr) {
 530                 optptr = (unsigned char *)raw + opt->rr;
 531                 ip_rt_get_source(&optptr[optptr[2]-5], rt);
 532                 opt->is_changed = 1;
 533         }
 534         if (opt->srr_is_hit) {
 535                 int srrptr, srrspace;
 536
 537                 optptr = raw + opt->srr;
 538
 539                 for ( srrptr=optptr[2], srrspace = optptr[1];
 540                      srrptr <= srrspace;
 541                      srrptr += 4
 542                      ) {
 543                         if (srrptr + 3 > srrspace)
 544                                 break;
 545                         if (memcmp(&rt->rt_dst, &optptr[srrptr-1], 4) == 0)
 546                                 break;
 547                 }
 548                 if (srrptr + 3 <= srrspace) {
 549                         opt->is_changed = 1;
 550                         ip_rt_get_source(&optptr[srrptr-1], rt);
 551                         skb->nh.iph->daddr = rt->rt_dst;
 552                         optptr[2] = srrptr+4;
 553                 } else if (net_ratelimit())
 554                         printk(KERN_CRIT "ip_forward(): Argh! Destination lost!\n");
 555                 if (opt->ts_needaddr) {
 556                         optptr = raw + opt->ts;
 557                         ip_rt_get_source(&optptr[optptr[2]-9], rt);
 558                         opt->is_changed = 1;
 559                 }
 560         }
 561         if (opt->is_changed) {
 562                 opt->is_changed = 0;
 563                 ip_send_check(skb->nh.iph);
 564         }
 565 }
 566
 567 int ip_options_rcv_srr(struct sk_buff *skb)
 568 {
 569         struct ip_options *opt = &(IPCB(skb)->opt);
 570         int srrspace, srrptr;
 571         u32 nexthop;
 572         struct iphdr *iph = skb->nh.iph;
 573         unsigned char * optptr = skb->nh.raw + opt->srr;
 574         struct rtable *rt = (struct rtable*)skb->dst;
 575         struct rtable *rt2;
 576         int err;
 577
 578         if (!opt->srr)
 579                 return 0;
 580
 581         if (skb->pkt_type != PACKET_HOST)
 582                 return -EINVAL;
 583         if (rt->rt_type == RTN_UNICAST) {
 584                 if (!opt->is_strictroute)
 585                         return 0;
 586                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
 587                 return -EINVAL;
 588         }
 589         if (rt->rt_type != RTN_LOCAL)
 590                 return -EINVAL;
 591
 592         for (srrptr=optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
 593                 if (srrptr + 3 > srrspace) {
 594                         icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
 595                         return -EINVAL;
 596                 }
 597                 memcpy(&nexthop, &optptr[srrptr-1], 4);
 598
 599                 rt = (struct rtable*)skb->dst;
 600                 skb->dst = NULL;
 601                 err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, skb->dev);
 602                 rt2 = (struct rtable*)skb->dst;
 603                 if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
 604                         ip_rt_put(rt2);
 605                         skb->dst = &rt->u.dst;
 606                         return -EINVAL;
 607                 }
 608                 ip_rt_put(rt);
 609                 if (rt2->rt_type != RTN_LOCAL)
 610                         break;
 611                 /* Superfast 8) loopback forward */
 612                 memcpy(&iph->daddr, &optptr[srrptr-1], 4);
 613                 opt->is_changed = 1;
 614         }
 615         if (srrptr <= srrspace) {
 616                 opt->srr_is_hit = 1;
 617                 opt->is_changed = 1;
 618         }
 619         return 0;
 620 }
 621
 622 EXPORT_SYMBOL(ip_options_compile);
 623 EXPORT_SYMBOL(ip_options_undo);