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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                         struct timespec tv;
 62                         __be32 midtime;
 63                         getnstimeofday(&tv);
 64                         midtime = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + tv.tv_nsec / NSEC_PER_MSEC);
 65                         memcpy(iph+opt->ts+iph[opt->ts+2]-5, &midtime, 4);
 66                 }
 67                 return;
 68         }
 69         if (opt->rr) {
 70                 memset(iph+opt->rr, IPOPT_NOP, iph[opt->rr+1]);
 71                 opt->rr = 0;
 72                 opt->rr_needaddr = 0;
 73         }
 74         if (opt->ts) {
 75                 memset(iph+opt->ts, IPOPT_NOP, iph[opt->ts+1]);
 76                 opt->ts = 0;
 77                 opt->ts_needaddr = opt->ts_needtime = 0;
 78         }
 79 }
 80 
 81 /*
 82  * Provided (sopt, skb) points to received options,
 83  * build in dopt compiled option set appropriate for answering.
 84  * i.e. invert SRR option, copy anothers,
 85  * and grab room in RR/TS options.
 86  *
 87  * NOTE: dopt cannot point to skb.
 88  */
 89 
 90 int ip_options_echo(struct ip_options *dopt, struct sk_buff *skb)
 91 {
 92         const struct ip_options *sopt;
 93         unsigned char *sptr, *dptr;
 94         int soffset, doffset;
 95         int     optlen;
 96 
 97         memset(dopt, 0, sizeof(struct ip_options));
 98 
 99         sopt = &(IPCB(skb)->opt);
100 
101         if (sopt->optlen == 0)
102                 return 0;
103 
104         sptr = skb_network_header(skb);
105         dptr = dopt->__data;
106 
107         if (sopt->rr) {
108                 optlen  = sptr[sopt->rr+1];
109                 soffset = sptr[sopt->rr+2];
110                 dopt->rr = dopt->optlen + sizeof(struct iphdr);
111                 memcpy(dptr, sptr+sopt->rr, optlen);
112                 if (sopt->rr_needaddr && soffset <= optlen) {
113                         if (soffset + 3 > optlen)
114                                 return -EINVAL;
115                         dptr[2] = soffset + 4;
116                         dopt->rr_needaddr = 1;
117                 }
118                 dptr += optlen;
119                 dopt->optlen += optlen;
120         }
121         if (sopt->ts) {
122                 optlen = sptr[sopt->ts+1];
123                 soffset = sptr[sopt->ts+2];
124                 dopt->ts = dopt->optlen + sizeof(struct iphdr);
125                 memcpy(dptr, sptr+sopt->ts, optlen);
126                 if (soffset <= optlen) {
127                         if (sopt->ts_needaddr) {
128                                 if (soffset + 3 > optlen)
129                                         return -EINVAL;
130                                 dopt->ts_needaddr = 1;
131                                 soffset += 4;
132                         }
133                         if (sopt->ts_needtime) {
134                                 if (soffset + 3 > optlen)
135                                         return -EINVAL;
136                                 if ((dptr[3]&0xF) != IPOPT_TS_PRESPEC) {
137                                         dopt->ts_needtime = 1;
138                                         soffset += 4;
139                                 } else {
140                                         dopt->ts_needtime = 0;
141 
142                                         if (soffset + 7 <= optlen) {
143                                                 __be32 addr;
144 
145                                                 memcpy(&addr, dptr+soffset-1, 4);
146                                                 if (inet_addr_type(dev_net(skb_dst(skb)->dev), addr) != RTN_UNICAST) {
147                                                         dopt->ts_needtime = 1;
148                                                         soffset += 8;
149                                                 }
150                                         }
151                                 }
152                         }
153                         dptr[2] = soffset;
154                 }
155                 dptr += optlen;
156                 dopt->optlen += optlen;
157         }
158         if (sopt->srr) {
159                 unsigned char *start = sptr+sopt->srr;
160                 __be32 faddr;
161 
162                 optlen  = start[1];
163                 soffset = start[2];
164                 doffset = 0;
165                 if (soffset > optlen)
166                         soffset = optlen + 1;
167                 soffset -= 4;
168                 if (soffset > 3) {
169                         memcpy(&faddr, &start[soffset-1], 4);
170                         for (soffset-=4, doffset=4; soffset > 3; soffset-=4, doffset+=4)
171                                 memcpy(&dptr[doffset-1], &start[soffset-1], 4);
172                         /*
173                          * RFC1812 requires to fix illegal source routes.
174                          */
175                         if (memcmp(&ip_hdr(skb)->saddr,
176                                    &start[soffset + 3], 4) == 0)
177                                 doffset -= 4;
178                 }
179                 if (doffset > 3) {
180                         __be32 daddr = fib_compute_spec_dst(skb);
181 
182                         memcpy(&start[doffset-1], &daddr, 4);
183                         dopt->faddr = faddr;
184                         dptr[0] = start[0];
185                         dptr[1] = doffset+3;
186                         dptr[2] = 4;
187                         dptr += doffset+3;
188                         dopt->srr = dopt->optlen + sizeof(struct iphdr);
189                         dopt->optlen += doffset+3;
190                         dopt->is_strictroute = sopt->is_strictroute;
191                 }
192         }
193         if (sopt->cipso) {
194                 optlen  = sptr[sopt->cipso+1];
195                 dopt->cipso = dopt->optlen+sizeof(struct iphdr);
196                 memcpy(dptr, sptr+sopt->cipso, optlen);
197                 dptr += optlen;
198                 dopt->optlen += optlen;
199         }
200         while (dopt->optlen & 3) {
201                 *dptr++ = IPOPT_END;
202                 dopt->optlen++;
203         }
204         return 0;
205 }
206 
207 /*
208  *      Options "fragmenting", just fill options not
209  *      allowed in fragments with NOOPs.
210  *      Simple and stupid 8), but the most efficient way.
211  */
212 
213 void ip_options_fragment(struct sk_buff *skb)
214 {
215         unsigned char *optptr = skb_network_header(skb) + sizeof(struct iphdr);
216         struct ip_options *opt = &(IPCB(skb)->opt);
217         int  l = opt->optlen;
218         int  optlen;
219 
220         while (l > 0) {
221                 switch (*optptr) {
222                 case IPOPT_END:
223                         return;
224                 case IPOPT_NOOP:
225                         l--;
226                         optptr++;
227                         continue;
228                 }
229                 optlen = optptr[1];
230                 if (optlen<2 || optlen>l)
231                   return;
232                 if (!IPOPT_COPIED(*optptr))
233                         memset(optptr, IPOPT_NOOP, optlen);
234                 l -= optlen;
235                 optptr += optlen;
236         }
237         opt->ts = 0;
238         opt->rr = 0;
239         opt->rr_needaddr = 0;
240         opt->ts_needaddr = 0;
241         opt->ts_needtime = 0;
242 }
243 
244 /* helper used by ip_options_compile() to call fib_compute_spec_dst()
245  * at most one time.
246  */
247 static void spec_dst_fill(__be32 *spec_dst, struct sk_buff *skb)
248 {
249         if (*spec_dst == htonl(INADDR_ANY))
250                 *spec_dst = fib_compute_spec_dst(skb);
251 }
252 
253 /*
254  * Verify options and fill pointers in struct options.
255  * Caller should clear *opt, and set opt->data.
256  * If opt == NULL, then skb->data should point to IP header.
257  */
258 
259 int ip_options_compile(struct net *net,
260                        struct ip_options *opt, struct sk_buff *skb)
261 {
262         __be32 spec_dst = htonl(INADDR_ANY);
263         unsigned char *pp_ptr = NULL;
264         struct rtable *rt = NULL;
265         unsigned char *optptr;
266         unsigned char *iph;
267         int optlen, l;
268 
269         if (skb != NULL) {
270                 rt = skb_rtable(skb);
271                 optptr = (unsigned char *)&(ip_hdr(skb)[1]);
272         } else
273                 optptr = opt->__data;
274         iph = optptr - sizeof(struct iphdr);
275 
276         for (l = opt->optlen; l > 0; ) {
277                 switch (*optptr) {
278                       case IPOPT_END:
279                         for (optptr++, l--; l>0; optptr++, l--) {
280                                 if (*optptr != IPOPT_END) {
281                                         *optptr = IPOPT_END;
282                                         opt->is_changed = 1;
283                                 }
284                         }
285                         goto eol;
286                       case IPOPT_NOOP:
287                         l--;
288                         optptr++;
289                         continue;
290                 }
291                 optlen = optptr[1];
292                 if (optlen<2 || optlen>l) {
293                         pp_ptr = optptr;
294                         goto error;
295                 }
296                 switch (*optptr) {
297                       case IPOPT_SSRR:
298                       case IPOPT_LSRR:
299                         if (optlen < 3) {
300                                 pp_ptr = optptr + 1;
301                                 goto error;
302                         }
303                         if (optptr[2] < 4) {
304                                 pp_ptr = optptr + 2;
305                                 goto error;
306                         }
307                         /* NB: cf RFC-1812 5.2.4.1 */
308                         if (opt->srr) {
309                                 pp_ptr = optptr;
310                                 goto error;
311                         }
312                         if (!skb) {
313                                 if (optptr[2] != 4 || optlen < 7 || ((optlen-3) & 3)) {
314                                         pp_ptr = optptr + 1;
315                                         goto error;
316                                 }
317                                 memcpy(&opt->faddr, &optptr[3], 4);
318                                 if (optlen > 7)
319                                         memmove(&optptr[3], &optptr[7], optlen-7);
320                         }
321                         opt->is_strictroute = (optptr[0] == IPOPT_SSRR);
322                         opt->srr = optptr - iph;
323                         break;
324                       case IPOPT_RR:
325                         if (opt->rr) {
326                                 pp_ptr = optptr;
327                                 goto error;
328                         }
329                         if (optlen < 3) {
330                                 pp_ptr = optptr + 1;
331                                 goto error;
332                         }
333                         if (optptr[2] < 4) {
334                                 pp_ptr = optptr + 2;
335                                 goto error;
336                         }
337                         if (optptr[2] <= optlen) {
338                                 if (optptr[2]+3 > optlen) {
339                                         pp_ptr = optptr + 2;
340                                         goto error;
341                                 }
342                                 if (rt) {
343                                         spec_dst_fill(&spec_dst, skb);
344                                         memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
345                                         opt->is_changed = 1;
346                                 }
347                                 optptr[2] += 4;
348                                 opt->rr_needaddr = 1;
349                         }
350                         opt->rr = optptr - iph;
351                         break;
352                       case IPOPT_TIMESTAMP:
353                         if (opt->ts) {
354                                 pp_ptr = optptr;
355                                 goto error;
356                         }
357                         if (optlen < 4) {
358                                 pp_ptr = optptr + 1;
359                                 goto error;
360                         }
361                         if (optptr[2] < 5) {
362                                 pp_ptr = optptr + 2;
363                                 goto error;
364                         }
365                         if (optptr[2] <= optlen) {
366                                 unsigned char *timeptr = NULL;
367                                 if (optptr[2]+3 > optptr[1]) {
368                                         pp_ptr = optptr + 2;
369                                         goto error;
370                                 }
371                                 switch (optptr[3]&0xF) {
372                                       case IPOPT_TS_TSONLY:
373                                         if (skb)
374                                                 timeptr = &optptr[optptr[2]-1];
375                                         opt->ts_needtime = 1;
376                                         optptr[2] += 4;
377                                         break;
378                                       case IPOPT_TS_TSANDADDR:
379                                         if (optptr[2]+7 > optptr[1]) {
380                                                 pp_ptr = optptr + 2;
381                                                 goto error;
382                                         }
383                                         if (rt)  {
384                                                 spec_dst_fill(&spec_dst, skb);
385                                                 memcpy(&optptr[optptr[2]-1], &spec_dst, 4);
386                                                 timeptr = &optptr[optptr[2]+3];
387                                         }
388                                         opt->ts_needaddr = 1;
389                                         opt->ts_needtime = 1;
390                                         optptr[2] += 8;
391                                         break;
392                                       case IPOPT_TS_PRESPEC:
393                                         if (optptr[2]+7 > optptr[1]) {
394                                                 pp_ptr = optptr + 2;
395                                                 goto error;
396                                         }
397                                         {
398                                                 __be32 addr;
399                                                 memcpy(&addr, &optptr[optptr[2]-1], 4);
400                                                 if (inet_addr_type(net, addr) == RTN_UNICAST)
401                                                         break;
402                                                 if (skb)
403                                                         timeptr = &optptr[optptr[2]+3];
404                                         }
405                                         opt->ts_needtime = 1;
406                                         optptr[2] += 8;
407                                         break;
408                                       default:
409                                         if (!skb && !ns_capable(net->user_ns, CAP_NET_RAW)) {
410                                                 pp_ptr = optptr + 3;
411                                                 goto error;
412                                         }
413                                         break;
414                                 }
415                                 if (timeptr) {
416                                         struct timespec tv;
417                                         u32  midtime;
418                                         getnstimeofday(&tv);
419                                         midtime = (tv.tv_sec % 86400) * MSEC_PER_SEC + tv.tv_nsec / NSEC_PER_MSEC;
420                                         put_unaligned_be32(midtime, timeptr);
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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