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/capability.h>
  15 #include <linux/module.h>
  16 #include <linux/types.h>
  17 #include <asm/uaccess.h>
  18 #include <linux/skbuff.h>
  19 #include <linux/ip.h>
  20 #include <linux/icmp.h>
  21 #include <linux/netdevice.h>
  22 #include <linux/rtnetlink.h>
  23 #include <net/sock.h>
  24 #include <net/ip.h>
  25 #include <net/icmp.h>
  26 #include <net/route.h>
  27
  28 /*
  29  * Write options to IP header, record destination address to
  30  * source route option, address of outgoing interface
  31  * (we should already know it, so that this  function is allowed be
  32  * called only after routing decision) and timestamp,
  33  * if we originate this datagram.
  34  *
  35  * daddr is real destination address, next hop is recorded in IP header.
  36  * saddr is address of outgoing interface.
  37  */
  38
  39 void ip_options_build(struct sk_buff * skb, struct ip_options * opt,
  40                             u32 daddr, struct rtable *rt, int is_frag)
  41 {
  42         unsigned char * iph = skb->nh.raw;
  43
  44         memcpy(&(IPCB(skb)->opt), opt, sizeof(struct ip_options));
  45         memcpy(iph+sizeof(struct iphdr), opt->__data, opt->optlen);
  46         opt = &(IPCB(skb)->opt);
  47         opt->is_data = 0;
  48
  49         if (opt->srr)
  50                 memcpy(iph+opt->srr+iph[opt->srr+1]-4, &daddr, 4);
  51
  52         if (!is_frag) {
  53                 if (opt->rr_needaddr)
  54                         ip_rt_get_source(iph+opt->rr+iph[opt->rr+2]-5, rt);
  55                 if (opt->ts_needaddr)
  56                         ip_rt_get_source(iph+opt->ts+iph[opt->ts+2]-9, rt);
  57                 if (opt->ts_needtime) {
  58                         struct timeval tv;
  59                         __u32 midtime;
  60                         do_gettimeofday(&tv);
  61                         midtime = htonl((tv.tv_sec % 86400) * 1000 + tv.tv_usec / 1000);
  62                         memcpy(iph+opt->ts+iph[opt->ts+2]-5, &midtime, 4);
  63                 }
  64                 return;
  65         }
  66         if (opt->rr) {
  67                 memset(iph+opt->rr, IPOPT_NOP, iph[opt->rr+1]);
  68                 opt->rr = 0;
  69                 opt->rr_needaddr = 0;
  70         }
  71         if (opt->ts) {
  72                 memset(iph+opt->ts, IPOPT_NOP, iph[opt->ts+1]);
  73                 opt->ts = 0;
  74                 opt->ts_needaddr = opt->ts_needtime = 0;
  75         }
  76 }
  77
  78 /*
  79  * Provided (sopt, skb) points to received options,
  80  * build in dopt compiled option set appropriate for answering.
  81  * i.e. invert SRR option, copy anothers,
  82  * and grab room in RR/TS options.
  83  *
  84  * NOTE: dopt cannot point to skb.
  85  */
  86
  87 int ip_options_echo(struct ip_options * dopt, struct sk_buff * skb)
  88 {
  89         struct ip_options *sopt;
  90         unsigned char *sptr, *dptr;
  91         int soffset, doffset;
  92         int     optlen;
  93         u32     daddr;
  94
  95         memset(dopt, 0, sizeof(struct ip_options));
  96
  97         dopt->is_data = 1;
  98
  99         sopt = &(IPCB(skb)->opt);
 100
 101         if (sopt->optlen == 0) {
 102                 dopt->optlen = 0;
 103                 return 0;
 104         }
 105
 106         sptr = skb->nh.raw;
 107         dptr = dopt->__data;
 108
 109         if (skb->dst)
 110                 daddr = ((struct rtable*)skb->dst)->rt_spec_dst;
 111         else
 112                 daddr = skb->nh.iph->daddr;
 113
 114         if (sopt->rr) {
 115                 optlen  = sptr[sopt->rr+1];
 116                 soffset = sptr[sopt->rr+2];
 117                 dopt->rr = dopt->optlen + sizeof(struct iphdr);
 118                 memcpy(dptr, sptr+sopt->rr, optlen);
 119                 if (sopt->rr_needaddr && soffset <= optlen) {
 120                         if (soffset + 3 > optlen)
 121                                 return -EINVAL;
 122                         dptr[2] = soffset + 4;
 123                         dopt->rr_needaddr = 1;
 124                 }
 125                 dptr += optlen;
 126                 dopt->optlen += optlen;
 127         }
 128         if (sopt->ts) {
 129                 optlen = sptr[sopt->ts+1];
 130                 soffset = sptr[sopt->ts+2];
 131                 dopt->ts = dopt->optlen + sizeof(struct iphdr);
 132                 memcpy(dptr, sptr+sopt->ts, optlen);
 133                 if (soffset <= optlen) {
 134                         if (sopt->ts_needaddr) {
 135                                 if (soffset + 3 > optlen)
 136                                         return -EINVAL;
 137                                 dopt->ts_needaddr = 1;
 138                                 soffset += 4;
 139                         }
 140                         if (sopt->ts_needtime) {
 141                                 if (soffset + 3 > optlen)
 142                                         return -EINVAL;
 143                                 if ((dptr[3]&0xF) != IPOPT_TS_PRESPEC) {
 144                                         dopt->ts_needtime = 1;
 145                                         soffset += 4;
 146                                 } else {
 147                                         dopt->ts_needtime = 0;
 148
 149                                         if (soffset + 8 <= optlen) {
 150                                                 __u32 addr;
 151
 152                                                 memcpy(&addr, sptr+soffset-1, 4);
 153                                                 if (inet_addr_type(addr) != RTN_LOCAL) {
 154                                                         dopt->ts_needtime = 1;
 155                                                         soffset += 8;
 156                                                 }
 157                                         }
 158                                 }
 159                         }
 160                         dptr[2] = soffset;
 161                 }
 162                 dptr += optlen;
 163                 dopt->optlen += optlen;
 164         }
 165         if (sopt->srr) {
 166                 unsigned char * start = sptr+sopt->srr;
 167                 u32 faddr;
 168
 169                 optlen  = start[1];
 170                 soffset = start[2];
 171                 doffset = 0;
 172                 if (soffset > optlen)
 173                         soffset = optlen + 1;
 174                 soffset -= 4;
 175                 if (soffset > 3) {
 176                         memcpy(&faddr, &start[soffset-1], 4);
 177                         for (soffset-=4, doffset=4; soffset > 3; soffset-=4, doffset+=4)
 178                                 memcpy(&dptr[doffset-1], &start[soffset-1], 4);
 179                         /*
 180                          * RFC1812 requires to fix illegal source routes.
 181                          */
 182                         if (memcmp(&skb->nh.iph->saddr, &start[soffset+3], 4) == 0)
 183                                 doffset -= 4;
 184                 }
 185                 if (doffset > 3) {
 186                         memcpy(&start[doffset-1], &daddr, 4);
 187                         dopt->faddr = faddr;
 188                         dptr[0] = start[0];
 189                         dptr[1] = doffset+3;
 190                         dptr[2] = 4;
 191                         dptr += doffset+3;
 192                         dopt->srr = dopt->optlen + sizeof(struct iphdr);
 193                         dopt->optlen += doffset+3;
 194                         dopt->is_strictroute = sopt->is_strictroute;
 195                 }
 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->nh.raw + 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         return;
 240 }
 241
 242 /*
 243  * Verify options and fill pointers in struct options.
 244  * Caller should clear *opt, and set opt->data.
 245  * If opt == NULL, then skb->data should point to IP header.
 246  */
 247
 248 int ip_options_compile(struct ip_options * opt, struct sk_buff * skb)
 249 {
 250         int l;
 251         unsigned char * iph;
 252         unsigned char * optptr;
 253         int optlen;
 254         unsigned char * pp_ptr = NULL;
 255         struct rtable *rt = skb ? (struct rtable*)skb->dst : NULL;
 256
 257         if (!opt) {
 258                 opt = &(IPCB(skb)->opt);
 259                 iph = skb->nh.raw;
 260                 opt->optlen = ((struct iphdr *)iph)->ihl*4 - sizeof(struct iphdr);
 261                 optptr = iph + sizeof(struct iphdr);
 262                 opt->is_data = 0;
 263         } else {
 264                 optptr = opt->is_data ? opt->__data : (unsigned char*)&(skb->nh.iph[1]);
 265                 iph = optptr - sizeof(struct iphdr);
 266         }
 267
 268         for (l = opt->optlen; l > 0; ) {
 269                 switch (*optptr) {
 270                       case IPOPT_END:
 271                         for (optptr++, l--; l>0; optptr++, l--) {
 272                                 if (*optptr != IPOPT_END) {
 273                                         *optptr = IPOPT_END;
 274                                         opt->is_changed = 1;
 275                                 }
 276                         }
 277                         goto eol;
 278                       case IPOPT_NOOP:
 279                         l--;
 280                         optptr++;
 281                         continue;
 282                 }
 283                 optlen = optptr[1];
 284                 if (optlen<2 || optlen>l) {
 285                         pp_ptr = optptr;
 286                         goto error;
 287                 }
 288                 switch (*optptr) {
 289                       case IPOPT_SSRR:
 290                       case IPOPT_LSRR:
 291                         if (optlen < 3) {
 292                                 pp_ptr = optptr + 1;
 293                                 goto error;
 294                         }
 295                         if (optptr[2] < 4) {
 296                                 pp_ptr = optptr + 2;
 297                                 goto error;
 298                         }
 299                         /* NB: cf RFC-1812 5.2.4.1 */
 300                         if (opt->srr) {
 301                                 pp_ptr = optptr;
 302                                 goto error;
 303                         }
 304                         if (!skb) {
 305                                 if (optptr[2] != 4 || optlen < 7 || ((optlen-3) & 3)) {
 306                                         pp_ptr = optptr + 1;
 307                                         goto error;
 308                                 }
 309                                 memcpy(&opt->faddr, &optptr[3], 4);
 310                                 if (optlen > 7)
 311                                         memmove(&optptr[3], &optptr[7], optlen-7);
 312                         }
 313                         opt->is_strictroute = (optptr[0] == IPOPT_SSRR);
 314                         opt->srr = optptr - iph;
 315                         break;
 316                       case IPOPT_RR:
 317                         if (opt->rr) {
 318                                 pp_ptr = optptr;
 319                                 goto error;
 320                         }
 321                         if (optlen < 3) {
 322                                 pp_ptr = optptr + 1;
 323                                 goto error;
 324                         }
 325                         if (optptr[2] < 4) {
 326                                 pp_ptr = optptr + 2;
 327                                 goto error;
 328                         }
 329                         if (optptr[2] <= optlen) {
 330                                 if (optptr[2]+3 > optlen) {
 331                                         pp_ptr = optptr + 2;
 332                                         goto error;
 333                                 }
 334                                 if (skb) {
 335                                         memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
 336                                         opt->is_changed = 1;
 337                                 }
 338                                 optptr[2] += 4;
 339                                 opt->rr_needaddr = 1;
 340                         }
 341                         opt->rr = optptr - iph;
 342                         break;
 343                       case IPOPT_TIMESTAMP:
 344                         if (opt->ts) {
 345                                 pp_ptr = optptr;
 346                                 goto error;
 347                         }
 348                         if (optlen < 4) {
 349                                 pp_ptr = optptr + 1;
 350                                 goto error;
 351                         }
 352                         if (optptr[2] < 5) {
 353                                 pp_ptr = optptr + 2;
 354                                 goto error;
 355                         }
 356                         if (optptr[2] <= optlen) {
 357                                 __u32 * timeptr = NULL;
 358                                 if (optptr[2]+3 > optptr[1]) {
 359                                         pp_ptr = optptr + 2;
 360                                         goto error;
 361                                 }
 362                                 switch (optptr[3]&0xF) {
 363                                       case IPOPT_TS_TSONLY:
 364                                         opt->ts = optptr - iph;
 365                                         if (skb)
 366                                                 timeptr = (__u32*)&optptr[optptr[2]-1];
 367                                         opt->ts_needtime = 1;
 368                                         optptr[2] += 4;
 369                                         break;
 370                                       case IPOPT_TS_TSANDADDR:
 371                                         if (optptr[2]+7 > optptr[1]) {
 372                                                 pp_ptr = optptr + 2;
 373                                                 goto error;
 374                                         }
 375                                         opt->ts = optptr - iph;
 376                                         if (skb) {
 377                                                 memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
 378                                                 timeptr = (__u32*)&optptr[optptr[2]+3];
 379                                         }
 380                                         opt->ts_needaddr = 1;
 381                                         opt->ts_needtime = 1;
 382                                         optptr[2] += 8;
 383                                         break;
 384                                       case IPOPT_TS_PRESPEC:
 385                                         if (optptr[2]+7 > optptr[1]) {
 386                                                 pp_ptr = optptr + 2;
 387                                                 goto error;
 388                                         }
 389                                         opt->ts = optptr - iph;
 390                                         {
 391                                                 u32 addr;
 392                                                 memcpy(&addr, &optptr[optptr[2]-1], 4);
 393                                                 if (inet_addr_type(addr) == RTN_UNICAST)
 394                                                         break;
 395                                                 if (skb)
 396                                                         timeptr = (__u32*)&optptr[optptr[2]+3];
 397                                         }
 398                                         opt->ts_needtime = 1;
 399                                         optptr[2] += 8;
 400                                         break;
 401                                       default:
 402                                         if (!skb && !capable(CAP_NET_RAW)) {
 403                                                 pp_ptr = optptr + 3;
 404                                                 goto error;
 405                                         }
 406                                         break;
 407                                 }
 408                                 if (timeptr) {
 409                                         struct timeval tv;
 410                                         __u32  midtime;
 411                                         do_gettimeofday(&tv);
 412                                         midtime = htonl((tv.tv_sec % 86400) * 1000 + tv.tv_usec / 1000);
 413                                         memcpy(timeptr, &midtime, sizeof(__u32));
 414                                         opt->is_changed = 1;
 415                                 }
 416                         } else {
 417                                 unsigned overflow = optptr[3]>>4;
 418                                 if (overflow == 15) {
 419                                         pp_ptr = optptr + 3;
 420                                         goto error;
 421                                 }
 422                                 opt->ts = optptr - iph;
 423                                 if (skb) {
 424                                         optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
 425                                         opt->is_changed = 1;
 426                                 }
 427                         }
 428                         break;
 429                       case IPOPT_RA:
 430                         if (optlen < 4) {
 431                                 pp_ptr = optptr + 1;
 432                                 goto error;
 433                         }
 434                         if (optptr[2] == 0 && optptr[3] == 0)
 435                                 opt->router_alert = optptr - iph;
 436                         break;
 437                       case IPOPT_SEC:
 438                       case IPOPT_SID:
 439                       default:
 440                         if (!skb && !capable(CAP_NET_RAW)) {
 441                                 pp_ptr = optptr;
 442                                 goto error;
 443                         }
 444                         break;
 445                 }
 446                 l -= optlen;
 447                 optptr += optlen;
 448         }
 449
 450 eol:
 451         if (!pp_ptr)
 452                 return 0;
 453
 454 error:
 455         if (skb) {
 456                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((pp_ptr-iph)<<24));
 457         }
 458         return -EINVAL;
 459 }
 460
 461
 462 /*
 463  *      Undo all the changes done by ip_options_compile().
 464  */
 465
 466 void ip_options_undo(struct ip_options * opt)
 467 {
 468         if (opt->srr) {
 469                 unsigned  char * optptr = opt->__data+opt->srr-sizeof(struct  iphdr);
 470                 memmove(optptr+7, optptr+3, optptr[1]-7);
 471                 memcpy(optptr+3, &opt->faddr, 4);
 472         }
 473         if (opt->rr_needaddr) {
 474                 unsigned  char * optptr = opt->__data+opt->rr-sizeof(struct  iphdr);
 475                 optptr[2] -= 4;
 476                 memset(&optptr[optptr[2]-1], 0, 4);
 477         }
 478         if (opt->ts) {
 479                 unsigned  char * optptr = opt->__data+opt->ts-sizeof(struct  iphdr);
 480                 if (opt->ts_needtime) {
 481                         optptr[2] -= 4;
 482                         memset(&optptr[optptr[2]-1], 0, 4);
 483                         if ((optptr[3]&0xF) == IPOPT_TS_PRESPEC)
 484                                 optptr[2] -= 4;
 485                 }
 486                 if (opt->ts_needaddr) {
 487                         optptr[2] -= 4;
 488                         memset(&optptr[optptr[2]-1], 0, 4);
 489                 }
 490         }
 491 }
 492
 493 static struct ip_options *ip_options_get_alloc(const int optlen)
 494 {
 495         struct ip_options *opt = kmalloc(sizeof(*opt) + ((optlen + 3) & ~3),
 496                                          GFP_KERNEL);
 497         if (opt)
 498                 memset(opt, 0, sizeof(*opt));
 499         return opt;
 500 }
 501
 502 static int ip_options_get_finish(struct ip_options **optp,
 503                                  struct ip_options *opt, int optlen)
 504 {
 505         while (optlen & 3)
 506                 opt->__data[optlen++] = IPOPT_END;
 507         opt->optlen = optlen;
 508         opt->is_data = 1;
 509         opt->is_setbyuser = 1;
 510         if (optlen && ip_options_compile(opt, NULL)) {
 511                 kfree(opt);
 512                 return -EINVAL;
 513         }
 514         kfree(*optp);
 515         *optp = opt;
 516         return 0;
 517 }
 518
 519 int ip_options_get_from_user(struct ip_options **optp, unsigned char __user *data, int optlen)
 520 {
 521         struct ip_options *opt = ip_options_get_alloc(optlen);
 522
 523         if (!opt)
 524                 return -ENOMEM;
 525         if (optlen && copy_from_user(opt->__data, data, optlen)) {
 526                 kfree(opt);
 527                 return -EFAULT;
 528         }
 529         return ip_options_get_finish(optp, opt, optlen);
 530 }
 531
 532 int ip_options_get(struct ip_options **optp, unsigned char *data, int optlen)
 533 {
 534         struct ip_options *opt = ip_options_get_alloc(optlen);
 535
 536         if (!opt)
 537                 return -ENOMEM;
 538         if (optlen)
 539                 memcpy(opt->__data, data, optlen);
 540         return ip_options_get_finish(optp, opt, optlen);
 541 }
 542
 543 void ip_forward_options(struct sk_buff *skb)
 544 {
 545         struct   ip_options * opt       = &(IPCB(skb)->opt);
 546         unsigned char * optptr;
 547         struct rtable *rt = (struct rtable*)skb->dst;
 548         unsigned char *raw = skb->nh.raw;
 549
 550         if (opt->rr_needaddr) {
 551                 optptr = (unsigned char *)raw + opt->rr;
 552                 ip_rt_get_source(&optptr[optptr[2]-5], rt);
 553                 opt->is_changed = 1;
 554         }
 555         if (opt->srr_is_hit) {
 556                 int srrptr, srrspace;
 557
 558                 optptr = raw + opt->srr;
 559
 560                 for ( srrptr=optptr[2], srrspace = optptr[1];
 561                      srrptr <= srrspace;
 562                      srrptr += 4
 563                      ) {
 564                         if (srrptr + 3 > srrspace)
 565                                 break;
 566                         if (memcmp(&rt->rt_dst, &optptr[srrptr-1], 4) == 0)
 567                                 break;
 568                 }
 569                 if (srrptr + 3 <= srrspace) {
 570                         opt->is_changed = 1;
 571                         ip_rt_get_source(&optptr[srrptr-1], rt);
 572                         skb->nh.iph->daddr = rt->rt_dst;
 573                         optptr[2] = srrptr+4;
 574                 } else if (net_ratelimit())
 575                         printk(KERN_CRIT "ip_forward(): Argh! Destination lost!\n");
 576                 if (opt->ts_needaddr) {
 577                         optptr = raw + opt->ts;
 578                         ip_rt_get_source(&optptr[optptr[2]-9], rt);
 579                         opt->is_changed = 1;
 580                 }
 581         }
 582         if (opt->is_changed) {
 583                 opt->is_changed = 0;
 584                 ip_send_check(skb->nh.iph);
 585         }
 586 }
 587
 588 int ip_options_rcv_srr(struct sk_buff *skb)
 589 {
 590         struct ip_options *opt = &(IPCB(skb)->opt);
 591         int srrspace, srrptr;
 592         u32 nexthop;
 593         struct iphdr *iph = skb->nh.iph;
 594         unsigned char * optptr = skb->nh.raw + opt->srr;
 595         struct rtable *rt = (struct rtable*)skb->dst;
 596         struct rtable *rt2;
 597         int err;
 598
 599         if (!opt->srr)
 600                 return 0;
 601
 602         if (skb->pkt_type != PACKET_HOST)
 603                 return -EINVAL;
 604         if (rt->rt_type == RTN_UNICAST) {
 605                 if (!opt->is_strictroute)
 606                         return 0;
 607                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
 608                 return -EINVAL;
 609         }
 610         if (rt->rt_type != RTN_LOCAL)
 611                 return -EINVAL;
 612
 613         for (srrptr=optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
 614                 if (srrptr + 3 > srrspace) {
 615                         icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
 616                         return -EINVAL;
 617                 }
 618                 memcpy(&nexthop, &optptr[srrptr-1], 4);
 619
 620                 rt = (struct rtable*)skb->dst;
 621                 skb->dst = NULL;
 622                 err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, skb->dev);
 623                 rt2 = (struct rtable*)skb->dst;
 624                 if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
 625                         ip_rt_put(rt2);
 626                         skb->dst = &rt->u.dst;
 627                         return -EINVAL;
 628                 }
 629                 ip_rt_put(rt);
 630                 if (rt2->rt_type != RTN_LOCAL)
 631                         break;
 632                 /* Superfast 8) loopback forward */
 633                 memcpy(&iph->daddr, &optptr[srrptr-1], 4);
 634                 opt->is_changed = 1;
 635         }
 636         if (srrptr <= srrspace) {
 637                 opt->srr_is_hit = 1;
 638                 opt->is_changed = 1;
 639         }
 640         return 0;
 641 }