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/types.h>
  15 #include <asm/uaccess.h>
  16 #include <linux/skbuff.h>
  17 #include <linux/ip.h>
  18 #include <linux/icmp.h>
  19 #include <linux/netdevice.h>
  20 #include <linux/rtnetlink.h>
  21 #include <net/sock.h>
  22 #include <net/ip.h>
  23 #include <net/icmp.h>
  24
  25 /*
  26  * Write options to IP header, record destination address to
  27  * source route option, address of outgoing interface
  28  * (we should already know it, so that this  function is allowed be
  29  * called only after routing decision) and timestamp,
  30  * if we originate this datagram.
  31  *
  32  * daddr is real destination address, next hop is recorded in IP header.
  33  * saddr is address of outgoing interface.
  34  */
  35
  36 void ip_options_build(struct sk_buff * skb, struct ip_options * opt,
  37                             u32 daddr, struct rtable *rt, int is_frag)
  38 {
  39         unsigned char * iph = skb->nh.raw;
  40
  41         memcpy(&(IPCB(skb)->opt), opt, sizeof(struct ip_options));
  42         memcpy(iph+sizeof(struct iphdr), opt->__data, opt->optlen);
  43         opt = &(IPCB(skb)->opt);
  44         opt->is_data = 0;
  45
  46         if (opt->srr)
  47                 memcpy(iph+opt->srr+iph[opt->srr+1]-4, &daddr, 4);
  48
  49         if (!is_frag) {
  50                 if (opt->rr_needaddr)
  51                         ip_rt_get_source(iph+opt->rr+iph[opt->rr+2]-5, rt);
  52                 if (opt->ts_needaddr)
  53                         ip_rt_get_source(iph+opt->ts+iph[opt->ts+2]-9, rt);
  54                 if (opt->ts_needtime) {
  55                         struct timeval tv;
  56                         __u32 midtime;
  57                         do_gettimeofday(&tv);
  58                         midtime = htonl((tv.tv_sec % 86400) * 1000 + tv.tv_usec / 1000);
  59                         memcpy(iph+opt->ts+iph[opt->ts+2]-5, &midtime, 4);
  60                 }
  61                 return;
  62         }
  63         if (opt->rr) {
  64                 memset(iph+opt->rr, IPOPT_NOP, iph[opt->rr+1]);
  65                 opt->rr = 0;
  66                 opt->rr_needaddr = 0;
  67         }
  68         if (opt->ts) {
  69                 memset(iph+opt->ts, IPOPT_NOP, iph[opt->ts+1]);
  70                 opt->ts = 0;
  71                 opt->ts_needaddr = opt->ts_needtime = 0;
  72         }
  73 }
  74
  75 /*
  76  * Provided (sopt, skb) points to received options,
  77  * build in dopt compiled option set appropriate for answering.
  78  * i.e. invert SRR option, copy anothers,
  79  * and grab room in RR/TS options.
  80  *
  81  * NOTE: dopt cannot point to skb.
  82  */
  83
  84 int ip_options_echo(struct ip_options * dopt, struct sk_buff * skb)
  85 {
  86         struct ip_options *sopt;
  87         unsigned char *sptr, *dptr;
  88         int soffset, doffset;
  89         int     optlen;
  90         u32     daddr;
  91
  92         memset(dopt, 0, sizeof(struct ip_options));
  93
  94         dopt->is_data = 1;
  95
  96         sopt = &(IPCB(skb)->opt);
  97
  98         if (sopt->optlen == 0) {
  99                 dopt->optlen = 0;
 100                 return 0;
 101         }
 102
 103         sptr = skb->nh.raw;
 104         dptr = dopt->__data;
 105
 106         if (skb->dst)
 107                 daddr = ((struct rtable*)skb->dst)->rt_spec_dst;
 108         else
 109                 daddr = skb->nh.iph->daddr;
 110
 111         if (sopt->rr) {
 112                 optlen  = sptr[sopt->rr+1];
 113                 soffset = sptr[sopt->rr+2];
 114                 dopt->rr = dopt->optlen + sizeof(struct iphdr);
 115                 memcpy(dptr, sptr+sopt->rr, optlen);
 116                 if (sopt->rr_needaddr && soffset <= optlen) {
 117                         if (soffset + 3 > optlen)
 118                                 return -EINVAL;
 119                         dptr[2] = soffset + 4;
 120                         dopt->rr_needaddr = 1;
 121                 }
 122                 dptr += optlen;
 123                 dopt->optlen += optlen;
 124         }
 125         if (sopt->ts) {
 126                 optlen = sptr[sopt->ts+1];
 127                 soffset = sptr[sopt->ts+2];
 128                 dopt->ts = dopt->optlen + sizeof(struct iphdr);
 129                 memcpy(dptr, sptr+sopt->ts, optlen);
 130                 if (soffset <= optlen) {
 131                         if (sopt->ts_needaddr) {
 132                                 if (soffset + 3 > optlen)
 133                                         return -EINVAL;
 134                                 dopt->ts_needaddr = 1;
 135                                 soffset += 4;
 136                         }
 137                         if (sopt->ts_needtime) {
 138                                 if (soffset + 3 > optlen)
 139                                         return -EINVAL;
 140                                 if ((dptr[3]&0xF) != IPOPT_TS_PRESPEC) {
 141                                         dopt->ts_needtime = 1;
 142                                         soffset += 4;
 143                                 } else {
 144                                         dopt->ts_needtime = 0;
 145
 146                                         if (soffset + 8 <= optlen) {
 147                                                 __u32 addr;
 148
 149                                                 memcpy(&addr, sptr+soffset-1, 4);
 150                                                 if (inet_addr_type(addr) != RTN_LOCAL) {
 151                                                         dopt->ts_needtime = 1;
 152                                                         soffset += 8;
 153                                                 }
 154                                         }
 155                                 }
 156                         }
 157                         dptr[2] = soffset;
 158                 }
 159                 dptr += optlen;
 160                 dopt->optlen += optlen;
 161         }
 162         if (sopt->srr) {
 163                 unsigned char * start = sptr+sopt->srr;
 164                 u32 faddr;
 165
 166                 optlen  = start[1];
 167                 soffset = start[2];
 168                 doffset = 0;
 169                 if (soffset > optlen)
 170                         soffset = optlen + 1;
 171                 soffset -= 4;
 172                 if (soffset > 3) {
 173                         memcpy(&faddr, &start[soffset-1], 4);
 174                         for (soffset-=4, doffset=4; soffset > 3; soffset-=4, doffset+=4)
 175                                 memcpy(&dptr[doffset-1], &start[soffset-1], 4);
 176                         /*
 177                          * RFC1812 requires to fix illegal source routes.
 178                          */
 179                         if (memcmp(&skb->nh.iph->saddr, &start[soffset+3], 4) == 0)
 180                                 doffset -= 4;
 181                 }
 182                 if (doffset > 3) {
 183                         memcpy(&start[doffset-1], &daddr, 4);
 184                         dopt->faddr = faddr;
 185                         dptr[0] = start[0];
 186                         dptr[1] = doffset+3;
 187                         dptr[2] = 4;
 188                         dptr += doffset+3;
 189                         dopt->srr = dopt->optlen + sizeof(struct iphdr);
 190                         dopt->optlen += doffset+3;
 191                         dopt->is_strictroute = sopt->is_strictroute;
 192                 }
 193         }
 194         while (dopt->optlen & 3) {
 195                 *dptr++ = IPOPT_END;
 196                 dopt->optlen++;
 197         }
 198         return 0;
 199 }
 200
 201 /*
 202  *      Options "fragmenting", just fill options not
 203  *      allowed in fragments with NOOPs.
 204  *      Simple and stupid 8), but the most efficient way.
 205  */
 206
 207 void ip_options_fragment(struct sk_buff * skb)
 208 {
 209         unsigned char * optptr = skb->nh.raw;
 210         struct ip_options * opt = &(IPCB(skb)->opt);
 211         int  l = opt->optlen;
 212         int  optlen;
 213
 214         while (l > 0) {
 215                 switch (*optptr) {
 216                 case IPOPT_END:
 217                         return;
 218                 case IPOPT_NOOP:
 219                         l--;
 220                         optptr++;
 221                         continue;
 222                 }
 223                 optlen = optptr[1];
 224                 if (optlen<2 || optlen>l)
 225                   return;
 226                 if (!IPOPT_COPIED(*optptr))
 227                         memset(optptr, IPOPT_NOOP, optlen);
 228                 l -= optlen;
 229                 optptr += optlen;
 230         }
 231         opt->ts = 0;
 232         opt->rr = 0;
 233         opt->rr_needaddr = 0;
 234         opt->ts_needaddr = 0;
 235         opt->ts_needtime = 0;
 236         return;
 237 }
 238
 239 /*
 240  * Verify options and fill pointers in struct options.
 241  * Caller should clear *opt, and set opt->data.
 242  * If opt == NULL, then skb->data should point to IP header.
 243  */
 244
 245 int ip_options_compile(struct ip_options * opt, struct sk_buff * skb)
 246 {
 247         int l;
 248         unsigned char * iph;
 249         unsigned char * optptr;
 250         int optlen;
 251         unsigned char * pp_ptr = NULL;
 252         struct rtable *rt = skb ? (struct rtable*)skb->dst : NULL;
 253
 254         if (!opt) {
 255                 opt = &(IPCB(skb)->opt);
 256                 memset(opt, 0, sizeof(struct ip_options));
 257                 iph = skb->nh.raw;
 258                 opt->optlen = ((struct iphdr *)iph)->ihl*4 - sizeof(struct iphdr);
 259                 optptr = iph + sizeof(struct iphdr);
 260                 opt->is_data = 0;
 261         } else {
 262                 optptr = opt->is_data ? opt->__data : (unsigned char*)&(skb->nh.iph[1]);
 263                 iph = optptr - sizeof(struct iphdr);
 264         }
 265
 266         for (l = opt->optlen; l > 0; ) {
 267                 switch (*optptr) {
 268                       case IPOPT_END:
 269                         for (optptr++, l--; l>0; optptr++, l--) {
 270                                 if (*optptr != IPOPT_END) {
 271                                         *optptr = IPOPT_END;
 272                                         opt->is_changed = 1;
 273                                 }
 274                         }
 275                         goto eol;
 276                       case IPOPT_NOOP:
 277                         l--;
 278                         optptr++;
 279                         continue;
 280                 }
 281                 optlen = optptr[1];
 282                 if (optlen<2 || optlen>l) {
 283                         pp_ptr = optptr;
 284                         goto error;
 285                 }
 286                 switch (*optptr) {
 287                       case IPOPT_SSRR:
 288                       case IPOPT_LSRR:
 289                         if (optlen < 3) {
 290                                 pp_ptr = optptr + 1;
 291                                 goto error;
 292                         }
 293                         if (optptr[2] < 4) {
 294                                 pp_ptr = optptr + 2;
 295                                 goto error;
 296                         }
 297                         /* NB: cf RFC-1812 5.2.4.1 */
 298                         if (opt->srr) {
 299                                 pp_ptr = optptr;
 300                                 goto error;
 301                         }
 302                         if (!skb) {
 303                                 if (optptr[2] != 4 || optlen < 7 || ((optlen-3) & 3)) {
 304                                         pp_ptr = optptr + 1;
 305                                         goto error;
 306                                 }
 307                                 memcpy(&opt->faddr, &optptr[3], 4);
 308                                 if (optlen > 7)
 309                                         memmove(&optptr[3], &optptr[7], optlen-7);
 310                         }
 311                         opt->is_strictroute = (optptr[0] == IPOPT_SSRR);
 312                         opt->srr = optptr - iph;
 313                         break;
 314                       case IPOPT_RR:
 315                         if (opt->rr) {
 316                                 pp_ptr = optptr;
 317                                 goto error;
 318                         }
 319                         if (optlen < 3) {
 320                                 pp_ptr = optptr + 1;
 321                                 goto error;
 322                         }
 323                         if (optptr[2] < 4) {
 324                                 pp_ptr = optptr + 2;
 325                                 goto error;
 326                         }
 327                         if (optptr[2] <= optlen) {
 328                                 if (optptr[2]+3 > optlen) {
 329                                         pp_ptr = optptr + 2;
 330                                         goto error;
 331                                 }
 332                                 if (skb) {
 333                                         memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
 334                                         opt->is_changed = 1;
 335                                 }
 336                                 optptr[2] += 4;
 337                                 opt->rr_needaddr = 1;
 338                         }
 339                         opt->rr = optptr - iph;
 340                         break;
 341                       case IPOPT_TIMESTAMP:
 342                         if (opt->ts) {
 343                                 pp_ptr = optptr;
 344                                 goto error;
 345                         }
 346                         if (optlen < 4) {
 347                                 pp_ptr = optptr + 1;
 348                                 goto error;
 349                         }
 350                         if (optptr[2] < 5) {
 351                                 pp_ptr = optptr + 2;
 352                                 goto error;
 353                         }
 354                         if (optptr[2] <= optlen) {
 355                                 __u32 * timeptr = NULL;
 356                                 if (optptr[2]+3 > optptr[1]) {
 357                                         pp_ptr = optptr + 2;
 358                                         goto error;
 359                                 }
 360                                 switch (optptr[3]&0xF) {
 361                                       case IPOPT_TS_TSONLY:
 362                                         opt->ts = optptr - iph;
 363                                         if (skb)
 364                                                 timeptr = (__u32*)&optptr[optptr[2]-1];
 365                                         opt->ts_needtime = 1;
 366                                         optptr[2] += 4;
 367                                         break;
 368                                       case IPOPT_TS_TSANDADDR:
 369                                         if (optptr[2]+7 > optptr[1]) {
 370                                                 pp_ptr = optptr + 2;
 371                                                 goto error;
 372                                         }
 373                                         opt->ts = optptr - iph;
 374                                         if (skb) {
 375                                                 memcpy(&optptr[optptr[2]-1], &rt->rt_spec_dst, 4);
 376                                                 timeptr = (__u32*)&optptr[optptr[2]+3];
 377                                         }
 378                                         opt->ts_needaddr = 1;
 379                                         opt->ts_needtime = 1;
 380                                         optptr[2] += 8;
 381                                         break;
 382                                       case IPOPT_TS_PRESPEC:
 383                                         if (optptr[2]+7 > optptr[1]) {
 384                                                 pp_ptr = optptr + 2;
 385                                                 goto error;
 386                                         }
 387                                         opt->ts = optptr - iph;
 388                                         {
 389                                                 u32 addr;
 390                                                 memcpy(&addr, &optptr[optptr[2]-1], 4);
 391                                                 if (inet_addr_type(addr) == RTN_UNICAST)
 392                                                         break;
 393                                                 if (skb)
 394                                                         timeptr = (__u32*)&optptr[optptr[2]+3];
 395                                         }
 396                                         opt->ts_needtime = 1;
 397                                         optptr[2] += 8;
 398                                         break;
 399                                       default:
 400                                         if (!skb && !capable(CAP_NET_RAW)) {
 401                                                 pp_ptr = optptr + 3;
 402                                                 goto error;
 403                                         }
 404                                         break;
 405                                 }
 406                                 if (timeptr) {
 407                                         struct timeval tv;
 408                                         __u32  midtime;
 409                                         do_gettimeofday(&tv);
 410                                         midtime = htonl((tv.tv_sec % 86400) * 1000 + tv.tv_usec / 1000);
 411                                         memcpy(timeptr, &midtime, sizeof(__u32));
 412                                         opt->is_changed = 1;
 413                                 }
 414                         } else {
 415                                 unsigned overflow = optptr[3]>>4;
 416                                 if (overflow == 15) {
 417                                         pp_ptr = optptr + 3;
 418                                         goto error;
 419                                 }
 420                                 opt->ts = optptr - iph;
 421                                 if (skb) {
 422                                         optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
 423                                         opt->is_changed = 1;
 424                                 }
 425                         }
 426                         break;
 427                       case IPOPT_RA:
 428                         if (optlen < 4) {
 429                                 pp_ptr = optptr + 1;
 430                                 goto error;
 431                         }
 432                         if (optptr[2] == 0 && optptr[3] == 0)
 433                                 opt->router_alert = optptr - iph;
 434                         break;
 435                       case IPOPT_SEC:
 436                       case IPOPT_SID:
 437                       default:
 438                         if (!skb && !capable(CAP_NET_RAW)) {
 439                                 pp_ptr = optptr;
 440                                 goto error;
 441                         }
 442                         break;
 443                 }
 444                 l -= optlen;
 445                 optptr += optlen;
 446         }
 447
 448 eol:
 449         if (!pp_ptr)
 450                 return 0;
 451
 452 error:
 453         if (skb) {
 454                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((pp_ptr-iph)<<24));
 455         }
 456         return -EINVAL;
 457 }
 458
 459
 460 /*
 461  *      Undo all the changes done by ip_options_compile().
 462  */
 463
 464 void ip_options_undo(struct ip_options * opt)
 465 {
 466         if (opt->srr) {
 467                 unsigned  char * optptr = opt->__data+opt->srr-sizeof(struct  iphdr);
 468                 memmove(optptr+7, optptr+3, optptr[1]-7);
 469                 memcpy(optptr+3, &opt->faddr, 4);
 470         }
 471         if (opt->rr_needaddr) {
 472                 unsigned  char * optptr = opt->__data+opt->rr-sizeof(struct  iphdr);
 473                 optptr[2] -= 4;
 474                 memset(&optptr[optptr[2]-1], 0, 4);
 475         }
 476         if (opt->ts) {
 477                 unsigned  char * optptr = opt->__data+opt->ts-sizeof(struct  iphdr);
 478                 if (opt->ts_needtime) {
 479                         optptr[2] -= 4;
 480                         memset(&optptr[optptr[2]-1], 0, 4);
 481                         if ((optptr[3]&0xF) == IPOPT_TS_PRESPEC)
 482                                 optptr[2] -= 4;
 483                 }
 484                 if (opt->ts_needaddr) {
 485                         optptr[2] -= 4;
 486                         memset(&optptr[optptr[2]-1], 0, 4);
 487                 }
 488         }
 489 }
 490
 491 int ip_options_get(struct ip_options **optp, unsigned char *data, int optlen, int user)
 492 {
 493         struct ip_options *opt;
 494
 495         opt = kmalloc(sizeof(struct ip_options)+((optlen+3)&~3), GFP_KERNEL);
 496         if (!opt)
 497                 return -ENOMEM;
 498         memset(opt, 0, sizeof(struct ip_options));
 499         if (optlen) {
 500                 if (user) {
 501                         if (copy_from_user(opt->__data, data, optlen)) {
 502                                 kfree(opt);
 503                                 return -EFAULT;
 504                         }
 505                 } else
 506                         memcpy(opt->__data, data, optlen);
 507         }
 508         while (optlen & 3)
 509                 opt->__data[optlen++] = IPOPT_END;
 510         opt->optlen = optlen;
 511         opt->is_data = 1;
 512         opt->is_setbyuser = 1;
 513         if (optlen && ip_options_compile(opt, NULL)) {
 514                 kfree(opt);
 515                 return -EINVAL;
 516         }
 517         if (*optp)
 518                 kfree(*optp);
 519         *optp = opt;
 520         return 0;
 521 }
 522
 523 void ip_forward_options(struct sk_buff *skb)
 524 {
 525         struct   ip_options * opt       = &(IPCB(skb)->opt);
 526         unsigned char * optptr;
 527         struct rtable *rt = (struct rtable*)skb->dst;
 528         unsigned char *raw = skb->nh.raw;
 529
 530         if (opt->rr_needaddr) {
 531                 optptr = (unsigned char *)raw + opt->rr;
 532                 ip_rt_get_source(&optptr[optptr[2]-5], rt);
 533                 opt->is_changed = 1;
 534         }
 535         if (opt->srr_is_hit) {
 536                 int srrptr, srrspace;
 537
 538                 optptr = raw + opt->srr;
 539
 540                 for ( srrptr=optptr[2], srrspace = optptr[1];
 541                      srrptr <= srrspace;
 542                      srrptr += 4
 543                      ) {
 544                         if (srrptr + 3 > srrspace)
 545                                 break;
 546                         if (memcmp(&rt->rt_dst, &optptr[srrptr-1], 4) == 0)
 547                                 break;
 548                 }
 549                 if (srrptr + 3 <= srrspace) {
 550                         opt->is_changed = 1;
 551                         ip_rt_get_source(&optptr[srrptr-1], rt);
 552                         skb->nh.iph->daddr = rt->rt_dst;
 553                         optptr[2] = srrptr+4;
 554                 } else if (net_ratelimit())
 555                         printk(KERN_CRIT "ip_forward(): Argh! Destination lost!\n");
 556                 if (opt->ts_needaddr) {
 557                         optptr = raw + opt->ts;
 558                         ip_rt_get_source(&optptr[optptr[2]-9], rt);
 559                         opt->is_changed = 1;
 560                 }
 561         }
 562         if (opt->is_changed) {
 563                 opt->is_changed = 0;
 564                 ip_send_check(skb->nh.iph);
 565         }
 566 }
 567
 568 int ip_options_rcv_srr(struct sk_buff *skb)
 569 {
 570         struct ip_options *opt = &(IPCB(skb)->opt);
 571         int srrspace, srrptr;
 572         u32 nexthop;
 573         struct iphdr *iph = skb->nh.iph;
 574         unsigned char * optptr = skb->nh.raw + opt->srr;
 575         struct rtable *rt = (struct rtable*)skb->dst;
 576         struct rtable *rt2;
 577         int err;
 578
 579         if (!opt->srr)
 580                 return 0;
 581
 582         if (skb->pkt_type != PACKET_HOST)
 583                 return -EINVAL;
 584         if (rt->rt_type == RTN_UNICAST) {
 585                 if (!opt->is_strictroute)
 586                         return 0;
 587                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
 588                 return -EINVAL;
 589         }
 590         if (rt->rt_type != RTN_LOCAL)
 591                 return -EINVAL;
 592
 593         for (srrptr=optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
 594                 if (srrptr + 3 > srrspace) {
 595                         icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
 596                         return -EINVAL;
 597                 }
 598                 memcpy(&nexthop, &optptr[srrptr-1], 4);
 599
 600                 rt = (struct rtable*)skb->dst;
 601                 skb->dst = NULL;
 602                 err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, skb->dev);
 603                 rt2 = (struct rtable*)skb->dst;
 604                 if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
 605                         ip_rt_put(rt2);
 606                         skb->dst = &rt->u.dst;
 607                         return -EINVAL;
 608                 }
 609                 ip_rt_put(rt);
 610                 if (rt2->rt_type != RTN_LOCAL)
 611                         break;
 612                 /* Superfast 8) loopback forward */
 613                 memcpy(&iph->daddr, &optptr[srrptr-1], 4);
 614                 opt->is_changed = 1;
 615         }
 616         if (srrptr <= srrspace) {
 617                 opt->srr_is_hit = 1;
 618                 opt->is_changed = 1;
 619         }
 620         return 0;
 621 }