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netfilter: ipv6: nf_defrag: Pass on packets to stack per RFC2460
[android-x86/kernel.git] / net / ipv6 / netfilter / nf_conntrack_reasm.c
1 /*
2  * IPv6 fragment reassembly for connection tracking
3  *
4  * Copyright (C)2004 USAGI/WIDE Project
5  *
6  * Author:
7  *      Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
8  *
9  * Based on: net/ipv6/reassembly.c
10  *
11  * This program is free software; you can redistribute it and/or
12  * modify it under the terms of the GNU General Public License
13  * as published by the Free Software Foundation; either version
14  * 2 of the License, or (at your option) any later version.
15  */
16
17 #define pr_fmt(fmt) "IPv6-nf: " fmt
18
19 #include <linux/errno.h>
20 #include <linux/types.h>
21 #include <linux/string.h>
22 #include <linux/socket.h>
23 #include <linux/sockios.h>
24 #include <linux/jiffies.h>
25 #include <linux/net.h>
26 #include <linux/list.h>
27 #include <linux/netdevice.h>
28 #include <linux/in6.h>
29 #include <linux/ipv6.h>
30 #include <linux/icmpv6.h>
31 #include <linux/random.h>
32 #include <linux/slab.h>
33
34 #include <net/sock.h>
35 #include <net/snmp.h>
36 #include <net/inet_frag.h>
37
38 #include <net/ipv6.h>
39 #include <net/protocol.h>
40 #include <net/transp_v6.h>
41 #include <net/rawv6.h>
42 #include <net/ndisc.h>
43 #include <net/addrconf.h>
44 #include <net/inet_ecn.h>
45 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
46 #include <linux/sysctl.h>
47 #include <linux/netfilter.h>
48 #include <linux/netfilter_ipv6.h>
49 #include <linux/kernel.h>
50 #include <linux/module.h>
51 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
52
53 static const char nf_frags_cache_name[] = "nf-frags";
54
55 struct nf_ct_frag6_skb_cb
56 {
57         struct inet6_skb_parm   h;
58         int                     offset;
59 };
60
61 #define NFCT_FRAG6_CB(skb)      ((struct nf_ct_frag6_skb_cb *)((skb)->cb))
62
63 static struct inet_frags nf_frags;
64
65 #ifdef CONFIG_SYSCTL
66 static int zero;
67
68 static struct ctl_table nf_ct_frag6_sysctl_table[] = {
69         {
70                 .procname       = "nf_conntrack_frag6_timeout",
71                 .data           = &init_net.nf_frag.frags.timeout,
72                 .maxlen         = sizeof(unsigned int),
73                 .mode           = 0644,
74                 .proc_handler   = proc_dointvec_jiffies,
75         },
76         {
77                 .procname       = "nf_conntrack_frag6_low_thresh",
78                 .data           = &init_net.nf_frag.frags.low_thresh,
79                 .maxlen         = sizeof(unsigned int),
80                 .mode           = 0644,
81                 .proc_handler   = proc_dointvec_minmax,
82                 .extra1         = &zero,
83                 .extra2         = &init_net.nf_frag.frags.high_thresh
84         },
85         {
86                 .procname       = "nf_conntrack_frag6_high_thresh",
87                 .data           = &init_net.nf_frag.frags.high_thresh,
88                 .maxlen         = sizeof(unsigned int),
89                 .mode           = 0644,
90                 .proc_handler   = proc_dointvec_minmax,
91                 .extra1         = &init_net.nf_frag.frags.low_thresh
92         },
93         { }
94 };
95
96 static int nf_ct_frag6_sysctl_register(struct net *net)
97 {
98         struct ctl_table *table;
99         struct ctl_table_header *hdr;
100
101         table = nf_ct_frag6_sysctl_table;
102         if (!net_eq(net, &init_net)) {
103                 table = kmemdup(table, sizeof(nf_ct_frag6_sysctl_table),
104                                 GFP_KERNEL);
105                 if (table == NULL)
106                         goto err_alloc;
107
108                 table[0].data = &net->nf_frag.frags.timeout;
109                 table[1].data = &net->nf_frag.frags.low_thresh;
110                 table[1].extra2 = &net->nf_frag.frags.high_thresh;
111                 table[2].data = &net->nf_frag.frags.high_thresh;
112                 table[2].extra1 = &net->nf_frag.frags.low_thresh;
113                 table[2].extra2 = &init_net.nf_frag.frags.high_thresh;
114         }
115
116         hdr = register_net_sysctl(net, "net/netfilter", table);
117         if (hdr == NULL)
118                 goto err_reg;
119
120         net->nf_frag.sysctl.frags_hdr = hdr;
121         return 0;
122
123 err_reg:
124         if (!net_eq(net, &init_net))
125                 kfree(table);
126 err_alloc:
127         return -ENOMEM;
128 }
129
130 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
131 {
132         struct ctl_table *table;
133
134         table = net->nf_frag.sysctl.frags_hdr->ctl_table_arg;
135         unregister_net_sysctl_table(net->nf_frag.sysctl.frags_hdr);
136         if (!net_eq(net, &init_net))
137                 kfree(table);
138 }
139
140 #else
141 static int nf_ct_frag6_sysctl_register(struct net *net)
142 {
143         return 0;
144 }
145 static void __net_exit nf_ct_frags6_sysctl_unregister(struct net *net)
146 {
147 }
148 #endif
149
150 static inline u8 ip6_frag_ecn(const struct ipv6hdr *ipv6h)
151 {
152         return 1 << (ipv6_get_dsfield(ipv6h) & INET_ECN_MASK);
153 }
154
155 static unsigned int nf_hash_frag(__be32 id, const struct in6_addr *saddr,
156                                  const struct in6_addr *daddr)
157 {
158         net_get_random_once(&nf_frags.rnd, sizeof(nf_frags.rnd));
159         return jhash_3words(ipv6_addr_hash(saddr), ipv6_addr_hash(daddr),
160                             (__force u32)id, nf_frags.rnd);
161 }
162
163
164 static unsigned int nf_hashfn(const struct inet_frag_queue *q)
165 {
166         const struct frag_queue *nq;
167
168         nq = container_of(q, struct frag_queue, q);
169         return nf_hash_frag(nq->id, &nq->saddr, &nq->daddr);
170 }
171
172 static void nf_ct_frag6_expire(unsigned long data)
173 {
174         struct frag_queue *fq;
175         struct net *net;
176
177         fq = container_of((struct inet_frag_queue *)data, struct frag_queue, q);
178         net = container_of(fq->q.net, struct net, nf_frag.frags);
179
180         ip6_expire_frag_queue(net, fq, &nf_frags);
181 }
182
183 /* Creation primitives. */
184 static inline struct frag_queue *fq_find(struct net *net, __be32 id,
185                                          u32 user, struct in6_addr *src,
186                                          struct in6_addr *dst, int iif, u8 ecn)
187 {
188         struct inet_frag_queue *q;
189         struct ip6_create_arg arg;
190         unsigned int hash;
191
192         arg.id = id;
193         arg.user = user;
194         arg.src = src;
195         arg.dst = dst;
196         arg.iif = iif;
197         arg.ecn = ecn;
198
199         local_bh_disable();
200         hash = nf_hash_frag(id, src, dst);
201
202         q = inet_frag_find(&net->nf_frag.frags, &nf_frags, &arg, hash);
203         local_bh_enable();
204         if (IS_ERR_OR_NULL(q)) {
205                 inet_frag_maybe_warn_overflow(q, pr_fmt());
206                 return NULL;
207         }
208         return container_of(q, struct frag_queue, q);
209 }
210
211
212 static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
213                              const struct frag_hdr *fhdr, int nhoff)
214 {
215         struct sk_buff *prev, *next;
216         unsigned int payload_len;
217         int offset, end;
218         u8 ecn;
219
220         if (fq->q.flags & INET_FRAG_COMPLETE) {
221                 pr_debug("Already completed\n");
222                 goto err;
223         }
224
225         payload_len = ntohs(ipv6_hdr(skb)->payload_len);
226
227         offset = ntohs(fhdr->frag_off) & ~0x7;
228         end = offset + (payload_len -
229                         ((u8 *)(fhdr + 1) - (u8 *)(ipv6_hdr(skb) + 1)));
230
231         if ((unsigned int)end > IPV6_MAXPLEN) {
232                 pr_debug("offset is too large.\n");
233                 return -EINVAL;
234         }
235
236         ecn = ip6_frag_ecn(ipv6_hdr(skb));
237
238         if (skb->ip_summed == CHECKSUM_COMPLETE) {
239                 const unsigned char *nh = skb_network_header(skb);
240                 skb->csum = csum_sub(skb->csum,
241                                      csum_partial(nh, (u8 *)(fhdr + 1) - nh,
242                                                   0));
243         }
244
245         /* Is this the final fragment? */
246         if (!(fhdr->frag_off & htons(IP6_MF))) {
247                 /* If we already have some bits beyond end
248                  * or have different end, the segment is corrupted.
249                  */
250                 if (end < fq->q.len ||
251                     ((fq->q.flags & INET_FRAG_LAST_IN) && end != fq->q.len)) {
252                         pr_debug("already received last fragment\n");
253                         goto err;
254                 }
255                 fq->q.flags |= INET_FRAG_LAST_IN;
256                 fq->q.len = end;
257         } else {
258                 /* Check if the fragment is rounded to 8 bytes.
259                  * Required by the RFC.
260                  */
261                 if (end & 0x7) {
262                         /* RFC2460 says always send parameter problem in
263                          * this case. -DaveM
264                          */
265                         pr_debug("end of fragment not rounded to 8 bytes.\n");
266                         return -EPROTO;
267                 }
268                 if (end > fq->q.len) {
269                         /* Some bits beyond end -> corruption. */
270                         if (fq->q.flags & INET_FRAG_LAST_IN) {
271                                 pr_debug("last packet already reached.\n");
272                                 goto err;
273                         }
274                         fq->q.len = end;
275                 }
276         }
277
278         if (end == offset)
279                 goto err;
280
281         /* Point into the IP datagram 'data' part. */
282         if (!pskb_pull(skb, (u8 *) (fhdr + 1) - skb->data)) {
283                 pr_debug("queue: message is too short.\n");
284                 goto err;
285         }
286         if (pskb_trim_rcsum(skb, end - offset)) {
287                 pr_debug("Can't trim\n");
288                 goto err;
289         }
290
291         /* Find out which fragments are in front and at the back of us
292          * in the chain of fragments so far.  We must know where to put
293          * this fragment, right?
294          */
295         prev = fq->q.fragments_tail;
296         if (!prev || NFCT_FRAG6_CB(prev)->offset < offset) {
297                 next = NULL;
298                 goto found;
299         }
300         prev = NULL;
301         for (next = fq->q.fragments; next != NULL; next = next->next) {
302                 if (NFCT_FRAG6_CB(next)->offset >= offset)
303                         break;  /* bingo! */
304                 prev = next;
305         }
306
307 found:
308         /* RFC5722, Section 4:
309          *                                  When reassembling an IPv6 datagram, if
310          *   one or more its constituent fragments is determined to be an
311          *   overlapping fragment, the entire datagram (and any constituent
312          *   fragments, including those not yet received) MUST be silently
313          *   discarded.
314          */
315
316         /* Check for overlap with preceding fragment. */
317         if (prev &&
318             (NFCT_FRAG6_CB(prev)->offset + prev->len) > offset)
319                 goto discard_fq;
320
321         /* Look for overlap with succeeding segment. */
322         if (next && NFCT_FRAG6_CB(next)->offset < end)
323                 goto discard_fq;
324
325         NFCT_FRAG6_CB(skb)->offset = offset;
326
327         /* Insert this fragment in the chain of fragments. */
328         skb->next = next;
329         if (!next)
330                 fq->q.fragments_tail = skb;
331         if (prev)
332                 prev->next = skb;
333         else
334                 fq->q.fragments = skb;
335
336         if (skb->dev) {
337                 fq->iif = skb->dev->ifindex;
338                 skb->dev = NULL;
339         }
340         fq->q.stamp = skb->tstamp;
341         fq->q.meat += skb->len;
342         fq->ecn |= ecn;
343         if (payload_len > fq->q.max_size)
344                 fq->q.max_size = payload_len;
345         add_frag_mem_limit(fq->q.net, skb->truesize);
346
347         /* The first fragment.
348          * nhoffset is obtained from the first fragment, of course.
349          */
350         if (offset == 0) {
351                 fq->nhoffset = nhoff;
352                 fq->q.flags |= INET_FRAG_FIRST_IN;
353         }
354
355         return 0;
356
357 discard_fq:
358         inet_frag_kill(&fq->q, &nf_frags);
359 err:
360         return -EINVAL;
361 }
362
363 /*
364  *      Check if this packet is complete.
365  *
366  *      It is called with locked fq, and caller must check that
367  *      queue is eligible for reassembly i.e. it is not COMPLETE,
368  *      the last and the first frames arrived and all the bits are here.
369  *
370  *      returns true if *prev skb has been transformed into the reassembled
371  *      skb, false otherwise.
372  */
373 static bool
374 nf_ct_frag6_reasm(struct frag_queue *fq, struct sk_buff *prev,  struct net_device *dev)
375 {
376         struct sk_buff *fp, *head = fq->q.fragments;
377         int    payload_len;
378         u8 ecn;
379
380         inet_frag_kill(&fq->q, &nf_frags);
381
382         WARN_ON(head == NULL);
383         WARN_ON(NFCT_FRAG6_CB(head)->offset != 0);
384
385         ecn = ip_frag_ecn_table[fq->ecn];
386         if (unlikely(ecn == 0xff))
387                 return false;
388
389         /* Unfragmented part is taken from the first segment. */
390         payload_len = ((head->data - skb_network_header(head)) -
391                        sizeof(struct ipv6hdr) + fq->q.len -
392                        sizeof(struct frag_hdr));
393         if (payload_len > IPV6_MAXPLEN) {
394                 net_dbg_ratelimited("nf_ct_frag6_reasm: payload len = %d\n",
395                                     payload_len);
396                 return false;
397         }
398
399         /* Head of list must not be cloned. */
400         if (skb_unclone(head, GFP_ATOMIC))
401                 return false;
402
403         /* If the first fragment is fragmented itself, we split
404          * it to two chunks: the first with data and paged part
405          * and the second, holding only fragments. */
406         if (skb_has_frag_list(head)) {
407                 struct sk_buff *clone;
408                 int i, plen = 0;
409
410                 clone = alloc_skb(0, GFP_ATOMIC);
411                 if (clone == NULL)
412                         return false;
413
414                 clone->next = head->next;
415                 head->next = clone;
416                 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
417                 skb_frag_list_init(head);
418                 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
419                         plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
420                 clone->len = clone->data_len = head->data_len - plen;
421                 head->data_len -= clone->len;
422                 head->len -= clone->len;
423                 clone->csum = 0;
424                 clone->ip_summed = head->ip_summed;
425
426                 add_frag_mem_limit(fq->q.net, clone->truesize);
427         }
428
429         /* morph head into last received skb: prev.
430          *
431          * This allows callers of ipv6 conntrack defrag to continue
432          * to use the last skb(frag) passed into the reasm engine.
433          * The last skb frag 'silently' turns into the full reassembled skb.
434          *
435          * Since prev is also part of q->fragments we have to clone it first.
436          */
437         if (head != prev) {
438                 struct sk_buff *iter;
439
440                 fp = skb_clone(prev, GFP_ATOMIC);
441                 if (!fp)
442                         return false;
443
444                 fp->next = prev->next;
445
446                 iter = head;
447                 while (iter) {
448                         if (iter->next == prev) {
449                                 iter->next = fp;
450                                 break;
451                         }
452                         iter = iter->next;
453                 }
454
455                 skb_morph(prev, head);
456                 prev->next = head->next;
457                 consume_skb(head);
458                 head = prev;
459         }
460
461         /* We have to remove fragment header from datagram and to relocate
462          * header in order to calculate ICV correctly. */
463         skb_network_header(head)[fq->nhoffset] = skb_transport_header(head)[0];
464         memmove(head->head + sizeof(struct frag_hdr), head->head,
465                 (head->data - head->head) - sizeof(struct frag_hdr));
466         head->mac_header += sizeof(struct frag_hdr);
467         head->network_header += sizeof(struct frag_hdr);
468
469         skb_shinfo(head)->frag_list = head->next;
470         skb_reset_transport_header(head);
471         skb_push(head, head->data - skb_network_header(head));
472
473         for (fp = head->next; fp; fp = fp->next) {
474                 head->data_len += fp->len;
475                 head->len += fp->len;
476                 if (head->ip_summed != fp->ip_summed)
477                         head->ip_summed = CHECKSUM_NONE;
478                 else if (head->ip_summed == CHECKSUM_COMPLETE)
479                         head->csum = csum_add(head->csum, fp->csum);
480                 head->truesize += fp->truesize;
481         }
482         sub_frag_mem_limit(fq->q.net, head->truesize);
483
484         head->ignore_df = 1;
485         head->next = NULL;
486         head->dev = dev;
487         head->tstamp = fq->q.stamp;
488         ipv6_hdr(head)->payload_len = htons(payload_len);
489         ipv6_change_dsfield(ipv6_hdr(head), 0xff, ecn);
490         IP6CB(head)->frag_max_size = sizeof(struct ipv6hdr) + fq->q.max_size;
491
492         /* Yes, and fold redundant checksum back. 8) */
493         if (head->ip_summed == CHECKSUM_COMPLETE)
494                 head->csum = csum_partial(skb_network_header(head),
495                                           skb_network_header_len(head),
496                                           head->csum);
497
498         fq->q.fragments = NULL;
499         fq->q.fragments_tail = NULL;
500
501         return true;
502 }
503
504 /*
505  * find the header just before Fragment Header.
506  *
507  * if success return 0 and set ...
508  * (*prevhdrp): the value of "Next Header Field" in the header
509  *              just before Fragment Header.
510  * (*prevhoff): the offset of "Next Header Field" in the header
511  *              just before Fragment Header.
512  * (*fhoff)   : the offset of Fragment Header.
513  *
514  * Based on ipv6_skip_hdr() in net/ipv6/exthdr.c
515  *
516  */
517 static int
518 find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
519 {
520         u8 nexthdr = ipv6_hdr(skb)->nexthdr;
521         const int netoff = skb_network_offset(skb);
522         u8 prev_nhoff = netoff + offsetof(struct ipv6hdr, nexthdr);
523         int start = netoff + sizeof(struct ipv6hdr);
524         int len = skb->len - start;
525         u8 prevhdr = NEXTHDR_IPV6;
526
527         while (nexthdr != NEXTHDR_FRAGMENT) {
528                 struct ipv6_opt_hdr hdr;
529                 int hdrlen;
530
531                 if (!ipv6_ext_hdr(nexthdr)) {
532                         return -1;
533                 }
534                 if (nexthdr == NEXTHDR_NONE) {
535                         pr_debug("next header is none\n");
536                         return -1;
537                 }
538                 if (len < (int)sizeof(struct ipv6_opt_hdr)) {
539                         pr_debug("too short\n");
540                         return -1;
541                 }
542                 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
543                         BUG();
544                 if (nexthdr == NEXTHDR_AUTH)
545                         hdrlen = (hdr.hdrlen+2)<<2;
546                 else
547                         hdrlen = ipv6_optlen(&hdr);
548
549                 prevhdr = nexthdr;
550                 prev_nhoff = start;
551
552                 nexthdr = hdr.nexthdr;
553                 len -= hdrlen;
554                 start += hdrlen;
555         }
556
557         if (len < 0)
558                 return -1;
559
560         *prevhdrp = prevhdr;
561         *prevhoff = prev_nhoff;
562         *fhoff = start;
563
564         return 0;
565 }
566
567 int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
568 {
569         u16 savethdr = skb->transport_header;
570         struct net_device *dev = skb->dev;
571         int fhoff, nhoff, ret;
572         struct frag_hdr *fhdr;
573         struct frag_queue *fq;
574         struct ipv6hdr *hdr;
575         u8 prevhdr;
576
577         /* Jumbo payload inhibits frag. header */
578         if (ipv6_hdr(skb)->payload_len == 0) {
579                 pr_debug("payload len = 0\n");
580                 return 0;
581         }
582
583         if (find_prev_fhdr(skb, &prevhdr, &nhoff, &fhoff) < 0)
584                 return 0;
585
586         if (!pskb_may_pull(skb, fhoff + sizeof(*fhdr)))
587                 return -ENOMEM;
588
589         skb_set_transport_header(skb, fhoff);
590         hdr = ipv6_hdr(skb);
591         fhdr = (struct frag_hdr *)skb_transport_header(skb);
592
593         skb_orphan(skb);
594         fq = fq_find(net, fhdr->identification, user, &hdr->saddr, &hdr->daddr,
595                      skb->dev ? skb->dev->ifindex : 0, ip6_frag_ecn(hdr));
596         if (fq == NULL) {
597                 pr_debug("Can't find and can't create new queue\n");
598                 return -ENOMEM;
599         }
600
601         spin_lock_bh(&fq->q.lock);
602
603         ret = nf_ct_frag6_queue(fq, skb, fhdr, nhoff);
604         if (ret < 0) {
605                 if (ret == -EPROTO) {
606                         skb->transport_header = savethdr;
607                         ret = 0;
608                 }
609                 goto out_unlock;
610         }
611
612         /* after queue has assumed skb ownership, only 0 or -EINPROGRESS
613          * must be returned.
614          */
615         ret = -EINPROGRESS;
616         if (fq->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
617             fq->q.meat == fq->q.len &&
618             nf_ct_frag6_reasm(fq, skb, dev))
619                 ret = 0;
620
621 out_unlock:
622         spin_unlock_bh(&fq->q.lock);
623         inet_frag_put(&fq->q, &nf_frags);
624         return ret;
625 }
626 EXPORT_SYMBOL_GPL(nf_ct_frag6_gather);
627
628 static int nf_ct_net_init(struct net *net)
629 {
630         net->nf_frag.frags.high_thresh = IPV6_FRAG_HIGH_THRESH;
631         net->nf_frag.frags.low_thresh = IPV6_FRAG_LOW_THRESH;
632         net->nf_frag.frags.timeout = IPV6_FRAG_TIMEOUT;
633         inet_frags_init_net(&net->nf_frag.frags);
634
635         return nf_ct_frag6_sysctl_register(net);
636 }
637
638 static void nf_ct_net_exit(struct net *net)
639 {
640         nf_ct_frags6_sysctl_unregister(net);
641         inet_frags_exit_net(&net->nf_frag.frags, &nf_frags);
642 }
643
644 static struct pernet_operations nf_ct_net_ops = {
645         .init = nf_ct_net_init,
646         .exit = nf_ct_net_exit,
647 };
648
649 int nf_ct_frag6_init(void)
650 {
651         int ret = 0;
652
653         nf_frags.hashfn = nf_hashfn;
654         nf_frags.constructor = ip6_frag_init;
655         nf_frags.destructor = NULL;
656         nf_frags.qsize = sizeof(struct frag_queue);
657         nf_frags.match = ip6_frag_match;
658         nf_frags.frag_expire = nf_ct_frag6_expire;
659         nf_frags.frags_cache_name = nf_frags_cache_name;
660         ret = inet_frags_init(&nf_frags);
661         if (ret)
662                 goto out;
663         ret = register_pernet_subsys(&nf_ct_net_ops);
664         if (ret)
665                 inet_frags_fini(&nf_frags);
666
667 out:
668         return ret;
669 }
670
671 void nf_ct_frag6_cleanup(void)
672 {
673         unregister_pernet_subsys(&nf_ct_net_ops);
674         inet_frags_fini(&nf_frags);
675 }