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TOMOYO Linux Cross Reference
Linux/net/ipv4/ip_options.c

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  1 /*
  2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
  3  *              operating system.  INET is implemented using the  BSD Socket
  4  *              interface as the means of communication with the user level.
  5  *
  6  *              The options processing module for ip.c
  7  *
  8  * Authors:     A.N.Kuznetsov
  9  *
 10  */
 11 
 12 #define pr_fmt(fmt) "IPv4: " fmt
 13 
 14 #include <linux/capability.h>
 15 #include <linux/module.h>
 16 #include <linux/slab.h>
 17 #include <linux/types.h>
 18 #include <asm/uaccess.h>
 19 #include <asm/unaligned.h>
 20 #include <linux/skbuff.h>
 21 #include <linux/ip.h>
 22 #include <linux/icmp.h>
 23 #include <linux/netdevice.h>
 24 #include <linux/rtnetlink.h>
 25 #include <net/sock.h>
 26 #include <net/ip.h>
 27 #include <net/icmp.h>
 28 #include <net/route.h>
 29 #include <net/cipso_ipv4.h>
 30 #include <net/ip_fib.h>
 31 
 32 /*
 33  * Write options to IP header, record destination address to
 34  * source route option, address of outgoing interface
 35  * (we should already know it, so that this  function is allowed be
 36  * called only after routing decision) and timestamp,
 37  * if we originate this datagram.
 38  *
 39  * daddr is real destination address, next hop is recorded in IP header.
 40  * saddr is address of outgoing interface.
 41  */
 42 
 43 void ip_options_build(struct sk_buff *skb, struct ip_options *opt,
 44                       __be32 daddr, struct rtable *rt, int is_frag)
 45 {
 46         unsigned char *iph = skb_network_header(skb);
 47 
 48         memcpy(&(IPCB(skb)->opt), opt, sizeof(struct ip_options));
 49         memcpy(iph+sizeof(struct iphdr), opt->__data, opt->optlen);
 50         opt = &(IPCB(skb)->opt);
 51 
 52         if (opt->srr)
 53                 memcpy(iph+opt->srr+iph[opt->srr+1]-4, &daddr, 4);
 54 
 55         if (!is_frag) {
 56                 if (opt->rr_needaddr)
 57                         ip_rt_get_source(iph+opt->rr+iph[opt->rr+2]-5, skb, rt);
 58                 if (opt->ts_needaddr)
 59                         ip_rt_get_source(iph+opt->ts+iph[opt->ts+2]-9, skb, rt);
 60                 if (opt->ts_needtime) {
 61                         __be32 midtime;
 62 
 63                         midtime = inet_current_timestamp();
 64                         memcpy(iph+opt->ts+iph[opt->ts+2]-5, &midtime, 4);
 65                 }
 66                 return;
 67         }
 68         if (opt->rr) {
 69                 memset(iph+opt->rr, IPOPT_NOP, iph[opt->rr+1]);
 70                 opt->rr = 0;
 71                 opt->rr_needaddr = 0;
 72         }
 73         if (opt->ts) {
 74                 memset(iph+opt->ts, IPOPT_NOP, iph[opt->ts+1]);
 75                 opt->ts = 0;
 76                 opt->ts_needaddr = opt->ts_needtime = 0;
 77         }
 78 }
 79 
 80 /*
 81  * Provided (sopt, skb) points to received options,
 82  * build in dopt compiled option set appropriate for answering.
 83  * i.e. invert SRR option, copy anothers,
 84  * and grab room in RR/TS options.
 85  *
 86  * NOTE: dopt cannot point to skb.
 87  */
 88 
 89 int __ip_options_echo(struct ip_options *dopt, struct sk_buff *skb,
 90                       const struct ip_options *sopt)
 91 {
 92         unsigned char *sptr, *dptr;
 93         int soffset, doffset;
 94         int     optlen;
 95 
 96         memset(dopt, 0, sizeof(struct ip_options));
 97 
 98         if (sopt->optlen == 0)
 99                 return 0;
100 
101         sptr = skb_network_header(skb);
102         dptr = dopt->__data;
103 
104         if (sopt->rr) {
105                 optlen  = sptr[sopt->rr+1];
106                 soffset = sptr[sopt->rr+2];
107                 dopt->rr = dopt->optlen + sizeof(struct iphdr);
108                 memcpy(dptr, sptr+sopt->rr, optlen);
109                 if (sopt->rr_needaddr && soffset <= optlen) {
110                         if (soffset + 3 > optlen)
111                                 return -EINVAL;
112                         dptr[2] = soffset + 4;
113                         dopt->rr_needaddr = 1;
114                 }
115                 dptr += optlen;
116                 dopt->optlen += optlen;
117         }
118         if (sopt->ts) {
119                 optlen = sptr[sopt->ts+1];
120                 soffset = sptr[sopt->ts+2];
121                 dopt->ts = dopt->optlen + sizeof(struct iphdr);
122                 memcpy(dptr, sptr+sopt->ts, optlen);
123                 if (soffset <= optlen) {
124                         if (sopt->ts_needaddr) {
125                                 if (soffset + 3 > optlen)
126                                         return -EINVAL;
127                                 dopt->ts_needaddr = 1;
128                                 soffset += 4;
129                         }
130                         if (sopt->ts_needtime) {
131                                 if (soffset + 3 > optlen)
132                                         return -EINVAL;
133                                 if ((dptr[3]&0xF) != IPOPT_TS_PRESPEC) {
134                                         dopt->ts_needtime = 1;
135                                         soffset += 4;
136                                 } else {
137                                         dopt->ts_needtime = 0;
138 
139                                         if (soffset + 7 <= optlen) {
140                                                 __be32 addr;
141 
142                                                 memcpy(&addr, dptr+soffset-1, 4);
143                                                 if (inet_addr_type(dev_net(skb_dst(skb)->dev), addr) != RTN_UNICAST) {
144                                                         dopt->ts_needtime = 1;
145                                                         soffset += 8;
146                                                 }
147                                         }
148                                 }
149                         }
150                         dptr[2] = soffset;
151                 }
152                 dptr += optlen;
153                 dopt->optlen += optlen;
154         }
155         if (sopt->srr) {
156                 unsigned char *start = sptr+sopt->srr;
157                 __be32 faddr;
158 
159                 optlen  = start[1];
160                 soffset = start[2];
161                 doffset = 0;
162                 if (soffset > optlen)
163                         soffset = optlen + 1;
164                 soffset -= 4;
165                 if (soffset > 3) {
166                         memcpy(&faddr, &start[soffset-1], 4);
167                         for (soffset -= 4, doffset = 4; soffset > 3; soffset -= 4, doffset += 4)
168                                 memcpy(&dptr[doffset-1], &start[soffset-1], 4);
169                         /*
170                          * RFC1812 requires to fix illegal source routes.
171                          */
172                         if (memcmp(&ip_hdr(skb)->saddr,
173                                    &start[soffset + 3], 4) == 0)
174                                 doffset -= 4;
175                 }
176                 if (doffset > 3) {
177                         __be32 daddr = fib_compute_spec_dst(skb);
178 
179                         memcpy(&start[doffset-1], &daddr, 4);
180                         dopt->faddr = faddr;
181                         dptr[0] = start[0];
182                         dptr[1] = doffset+3;
183                         dptr[2] = 4;
184                         dptr += doffset+3;
185                         dopt->srr = dopt->optlen + sizeof(struct iphdr);
186                         dopt->optlen += doffset+3;
187                         dopt->is_strictroute = sopt->is_strictroute;
188                 }
189         }
190         if (sopt->cipso) {
191                 optlen  = sptr[sopt->cipso+1];
192                 dopt->cipso = dopt->optlen+sizeof(struct iphdr);
193                 memcpy(dptr, sptr+sopt->cipso, optlen);
194                 dptr += optlen;
195                 dopt->optlen += optlen;
196         }
197         while (dopt->optlen & 3) {
198                 *dptr++ = IPOPT_END;
199                 dopt->optlen++;
200         }
201         return 0;
202 }
203 
204 /*
205  *      Options "fragmenting", just fill options not
206  *      allowed in fragments with NOOPs.
207  *      Simple and stupid 8), but the most efficient way.
208  */
209 
210 void ip_options_fragment(struct sk_buff *skb)
211 {
212         unsigned char *optptr = skb_network_header(skb) + sizeof(struct iphdr);
213         struct ip_options *opt = &(IPCB(skb)->opt);
214         int  l = opt->optlen;
215         int  optlen;
216 
217         while (l > 0) {
218                 switch (*optptr) {
219                 case IPOPT_END:
220                         return;
221                 case IPOPT_NOOP:
222                         l--;
223                         optptr++;
224                         continue;
225                 }
226                 optlen = optptr[1];
227                 if (optlen < 2 || optlen > l)
228                   return;
229                 if (!IPOPT_COPIED(*optptr))
230                         memset(optptr, IPOPT_NOOP, optlen);
231                 l -= optlen;
232                 optptr += optlen;
233         }
234         opt->ts = 0;
235         opt->rr = 0;
236         opt->rr_needaddr = 0;
237         opt->ts_needaddr = 0;
238         opt->ts_needtime = 0;
239 }
240 
241 /* helper used by ip_options_compile() to call fib_compute_spec_dst()
242  * at most one time.
243  */
244 static void spec_dst_fill(__be32 *spec_dst, struct sk_buff *skb)
245 {
246         if (*spec_dst == htonl(INADDR_ANY))
247                 *spec_dst = fib_compute_spec_dst(skb);
248 }
249 
250 /*
251  * Verify options and fill pointers in struct options.
252  * Caller should clear *opt, and set opt->data.
253  * If opt == NULL, then skb->data should point to IP header.
254  */
255 
256 int ip_options_compile(struct net *net,
257                        struct ip_options *opt, struct sk_buff *skb)
258 {
259         __be32 spec_dst = htonl(INADDR_ANY);
260         unsigned char *pp_ptr = NULL;
261         struct rtable *rt = NULL;
262         unsigned char *optptr;
263         unsigned char *iph;
264         int optlen, l;
265 
266         if (skb) {
267                 rt = skb_rtable(skb);
268                 optptr = (unsigned char *)&(ip_hdr(skb)[1]);
269         } else
270                 optptr = opt->__data;
271         iph = optptr - sizeof(struct iphdr);
272 
273         for (l = opt->optlen; l > 0; ) {
274                 switch (*optptr) {
275                 case IPOPT_END:
276                         for (optptr++, l--; l > 0; optptr++, l--) {
277                                 if (*optptr != IPOPT_END) {
278                                         *optptr = IPOPT_END;
279                                         opt->is_changed = 1;
280                                 }
281                         }
282                         goto eol;
283                 case IPOPT_NOOP:
284                         l--;
285                         optptr++;
286                         continue;
287                 }
288                 if (unlikely(l < 2)) {
289                         pp_ptr = optptr;
290                         goto error;
291                 }
292                 optlen = optptr[1];
293                 if (optlen < 2 || optlen > l) {
294                         pp_ptr = optptr;
295                         goto error;
296                 }
297                 switch (*optptr) {
298                 case IPOPT_SSRR:
299                 case IPOPT_LSRR:
300                         if (optlen < 3) {
301                                 pp_ptr = optptr + 1;
302                                 goto error;
303                         }
304                         if (optptr[2] < 4) {
305                                 pp_ptr = optptr + 2;
306                                 goto error;
307                         }
308                         /* NB: cf RFC-1812 5.2.4.1 */
309                         if (opt->srr) {
310                                 pp_ptr = optptr;
311                                 goto error;
312                         }
313                         if (!skb) {
314                                 if (optptr[2] != 4 || optlen < 7 || ((optlen-3) & 3)) {
315                                         pp_ptr = optptr + 1;
316                                         goto error;
317                                 }
318                                 memcpy(&opt->faddr, &optptr[3], 4);
319                                 if (optlen > 7)
320                                         memmove(&optptr[3], &optptr[7], optlen-7);
321                         }
322                         opt->is_strictroute = (optptr[0] == IPOPT_SSRR);
323                         opt->srr = optptr - iph;
324                         break;
325                 case IPOPT_RR:
326                         if (opt->rr) {
327                                 pp_ptr = optptr;
328                                 goto error;
329                         }
330                         if (optlen < 3) {
331                                 pp_ptr = optptr + 1;
332                                 goto error;
333                         }
334                         if (optptr[2] < 4) {
335                                 pp_ptr = optptr + 2;
336                                 goto error;
337                         }
338                         if (optptr[2] <= optlen) {
339                                 if (optptr[2]+3 > optlen) {
340                                         pp_ptr = optptr + 2;
341                                         goto error;
342                                 }
343                                 if (rt) {
344                                         spec_dst_fill(&spec_dst, skb);
345                                         memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
346                                         opt->is_changed = 1;
347                                 }
348                                 optptr[2] += 4;
349                                 opt->rr_needaddr = 1;
350                         }
351                         opt->rr = optptr - iph;
352                         break;
353                 case IPOPT_TIMESTAMP:
354                         if (opt->ts) {
355                                 pp_ptr = optptr;
356                                 goto error;
357                         }
358                         if (optlen < 4) {
359                                 pp_ptr = optptr + 1;
360                                 goto error;
361                         }
362                         if (optptr[2] < 5) {
363                                 pp_ptr = optptr + 2;
364                                 goto error;
365                         }
366                         if (optptr[2] <= optlen) {
367                                 unsigned char *timeptr = NULL;
368                                 if (optptr[2]+3 > optlen) {
369                                         pp_ptr = optptr + 2;
370                                         goto error;
371                                 }
372                                 switch (optptr[3]&0xF) {
373                                 case IPOPT_TS_TSONLY:
374                                         if (skb)
375                                                 timeptr = &optptr[optptr[2]-1];
376                                         opt->ts_needtime = 1;
377                                         optptr[2] += 4;
378                                         break;
379                                 case IPOPT_TS_TSANDADDR:
380                                         if (optptr[2]+7 > optlen) {
381                                                 pp_ptr = optptr + 2;
382                                                 goto error;
383                                         }
384                                         if (rt)  {
385                                                 spec_dst_fill(&spec_dst, skb);
386                                                 memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
387                                                 timeptr = &optptr[optptr[2]+3];
388                                         }
389                                         opt->ts_needaddr = 1;
390                                         opt->ts_needtime = 1;
391                                         optptr[2] += 8;
392                                         break;
393                                 case IPOPT_TS_PRESPEC:
394                                         if (optptr[2]+7 > optlen) {
395                                                 pp_ptr = optptr + 2;
396                                                 goto error;
397                                         }
398                                         {
399                                                 __be32 addr;
400                                                 memcpy(&addr, &optptr[optptr[2]-1], 4);
401                                                 if (inet_addr_type(net, addr) == RTN_UNICAST)
402                                                         break;
403                                                 if (skb)
404                                                         timeptr = &optptr[optptr[2]+3];
405                                         }
406                                         opt->ts_needtime = 1;
407                                         optptr[2] += 8;
408                                         break;
409                                 default:
410                                         if (!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) {
411                                                 pp_ptr = optptr + 3;
412                                                 goto error;
413                                         }
414                                         break;
415                                 }
416                                 if (timeptr) {
417                                         __be32 midtime;
418 
419                                         midtime = inet_current_timestamp();
420                                         memcpy(timeptr, &midtime, 4);
421                                         opt->is_changed = 1;
422                                 }
423                         } else if ((optptr[3]&0xF) != IPOPT_TS_PRESPEC) {
424                                 unsigned int overflow = optptr[3]>>4;
425                                 if (overflow == 15) {
426                                         pp_ptr = optptr + 3;
427                                         goto error;
428                                 }
429                                 if (skb) {
430                                         optptr[3] = (optptr[3]&0xF)|((overflow+1)<<4);
431                                         opt->is_changed = 1;
432                                 }
433                         }
434                         opt->ts = optptr - iph;
435                         break;
436                 case IPOPT_RA:
437                         if (optlen < 4) {
438                                 pp_ptr = optptr + 1;
439                                 goto error;
440                         }
441                         if (optptr[2] == 0 && optptr[3] == 0)
442                                 opt->router_alert = optptr - iph;
443                         break;
444                 case IPOPT_CIPSO:
445                         if ((!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) || opt->cipso) {
446                                 pp_ptr = optptr;
447                                 goto error;
448                         }
449                         opt->cipso = optptr - iph;
450                         if (cipso_v4_validate(skb, &optptr)) {
451                                 pp_ptr = optptr;
452                                 goto error;
453                         }
454                         break;
455                 case IPOPT_SEC:
456                 case IPOPT_SID:
457                 default:
458                         if (!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) {
459                                 pp_ptr = optptr;
460                                 goto error;
461                         }
462                         break;
463                 }
464                 l -= optlen;
465                 optptr += optlen;
466         }
467 
468 eol:
469         if (!pp_ptr)
470                 return 0;
471 
472 error:
473         if (skb) {
474                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((pp_ptr-iph)<<24));
475         }
476         return -EINVAL;
477 }
478 EXPORT_SYMBOL(ip_options_compile);
479 
480 /*
481  *      Undo all the changes done by ip_options_compile().
482  */
483 
484 void ip_options_undo(struct ip_options *opt)
485 {
486         if (opt->srr) {
487                 unsigned  char *optptr = opt->__data+opt->srr-sizeof(struct  iphdr);
488                 memmove(optptr+7, optptr+3, optptr[1]-7);
489                 memcpy(optptr+3, &opt->faddr, 4);
490         }
491         if (opt->rr_needaddr) {
492                 unsigned  char *optptr = opt->__data+opt->rr-sizeof(struct  iphdr);
493                 optptr[2] -= 4;
494                 memset(&optptr[optptr[2]-1], 0, 4);
495         }
496         if (opt->ts) {
497                 unsigned  char *optptr = opt->__data+opt->ts-sizeof(struct  iphdr);
498                 if (opt->ts_needtime) {
499                         optptr[2] -= 4;
500                         memset(&optptr[optptr[2]-1], 0, 4);
501                         if ((optptr[3]&0xF) == IPOPT_TS_PRESPEC)
502                                 optptr[2] -= 4;
503                 }
504                 if (opt->ts_needaddr) {
505                         optptr[2] -= 4;
506                         memset(&optptr[optptr[2]-1], 0, 4);
507                 }
508         }
509 }
510 
511 static struct ip_options_rcu *ip_options_get_alloc(const int optlen)
512 {
513         return kzalloc(sizeof(struct ip_options_rcu) + ((optlen + 3) & ~3),
514                        GFP_KERNEL);
515 }
516 
517 static int ip_options_get_finish(struct net *net, struct ip_options_rcu **optp,
518                                  struct ip_options_rcu *opt, int optlen)
519 {
520         while (optlen & 3)
521                 opt->opt.__data[optlen++] = IPOPT_END;
522         opt->opt.optlen = optlen;
523         if (optlen && ip_options_compile(net, &opt->opt, NULL)) {
524                 kfree(opt);
525                 return -EINVAL;
526         }
527         kfree(*optp);
528         *optp = opt;
529         return 0;
530 }
531 
532 int ip_options_get_from_user(struct net *net, struct ip_options_rcu **optp,
533                              unsigned char __user *data, int optlen)
534 {
535         struct ip_options_rcu *opt = ip_options_get_alloc(optlen);
536 
537         if (!opt)
538                 return -ENOMEM;
539         if (optlen && copy_from_user(opt->opt.__data, data, optlen)) {
540                 kfree(opt);
541                 return -EFAULT;
542         }
543         return ip_options_get_finish(net, optp, opt, optlen);
544 }
545 
546 int ip_options_get(struct net *net, struct ip_options_rcu **optp,
547                    unsigned char *data, int optlen)
548 {
549         struct ip_options_rcu *opt = ip_options_get_alloc(optlen);
550 
551         if (!opt)
552                 return -ENOMEM;
553         if (optlen)
554                 memcpy(opt->opt.__data, data, optlen);
555         return ip_options_get_finish(net, optp, opt, optlen);
556 }
557 
558 void ip_forward_options(struct sk_buff *skb)
559 {
560         struct   ip_options *opt        = &(IPCB(skb)->opt);
561         unsigned char *optptr;
562         struct rtable *rt = skb_rtable(skb);
563         unsigned char *raw = skb_network_header(skb);
564 
565         if (opt->rr_needaddr) {
566                 optptr = (unsigned char *)raw + opt->rr;
567                 ip_rt_get_source(&optptr[optptr[2]-5], skb, rt);
568                 opt->is_changed = 1;
569         }
570         if (opt->srr_is_hit) {
571                 int srrptr, srrspace;
572 
573                 optptr = raw + opt->srr;
574 
575                 for ( srrptr = optptr[2], srrspace = optptr[1];
576                      srrptr <= srrspace;
577                      srrptr += 4
578                      ) {
579                         if (srrptr + 3 > srrspace)
580                                 break;
581                         if (memcmp(&opt->nexthop, &optptr[srrptr-1], 4) == 0)
582                                 break;
583                 }
584                 if (srrptr + 3 <= srrspace) {
585                         opt->is_changed = 1;
586                         ip_hdr(skb)->daddr = opt->nexthop;
587                         ip_rt_get_source(&optptr[srrptr-1], skb, rt);
588                         optptr[2] = srrptr+4;
589                 } else {
590                         net_crit_ratelimited("%s(): Argh! Destination lost!\n",
591                                              __func__);
592                 }
593                 if (opt->ts_needaddr) {
594                         optptr = raw + opt->ts;
595                         ip_rt_get_source(&optptr[optptr[2]-9], skb, rt);
596                         opt->is_changed = 1;
597                 }
598         }
599         if (opt->is_changed) {
600                 opt->is_changed = 0;
601                 ip_send_check(ip_hdr(skb));
602         }
603 }
604 
605 int ip_options_rcv_srr(struct sk_buff *skb)
606 {
607         struct ip_options *opt = &(IPCB(skb)->opt);
608         int srrspace, srrptr;
609         __be32 nexthop;
610         struct iphdr *iph = ip_hdr(skb);
611         unsigned char *optptr = skb_network_header(skb) + opt->srr;
612         struct rtable *rt = skb_rtable(skb);
613         struct rtable *rt2;
614         unsigned long orefdst;
615         int err;
616 
617         if (!rt)
618                 return 0;
619 
620         if (skb->pkt_type != PACKET_HOST)
621                 return -EINVAL;
622         if (rt->rt_type == RTN_UNICAST) {
623                 if (!opt->is_strictroute)
624                         return 0;
625                 icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl(16<<24));
626                 return -EINVAL;
627         }
628         if (rt->rt_type != RTN_LOCAL)
629                 return -EINVAL;
630 
631         for (srrptr = optptr[2], srrspace = optptr[1]; srrptr <= srrspace; srrptr += 4) {
632                 if (srrptr + 3 > srrspace) {
633                         icmp_send(skb, ICMP_PARAMETERPROB, 0, htonl((opt->srr+2)<<24));
634                         return -EINVAL;
635                 }
636                 memcpy(&nexthop, &optptr[srrptr-1], 4);
637 
638                 orefdst = skb->_skb_refdst;
639                 skb_dst_set(skb, NULL);
640                 err = ip_route_input(skb, nexthop, iph->saddr, iph->tos, skb->dev);
641                 rt2 = skb_rtable(skb);
642                 if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
643                         skb_dst_drop(skb);
644                         skb->_skb_refdst = orefdst;
645                         return -EINVAL;
646                 }
647                 refdst_drop(orefdst);
648                 if (rt2->rt_type != RTN_LOCAL)
649                         break;
650                 /* Superfast 8) loopback forward */
651                 iph->daddr = nexthop;
652                 opt->is_changed = 1;
653         }
654         if (srrptr <= srrspace) {
655                 opt->srr_is_hit = 1;
656                 opt->nexthop = nexthop;
657                 opt->is_changed = 1;
658         }
659         return 0;
660 }
661 EXPORT_SYMBOL(ip_options_rcv_srr);
662 

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