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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * INET An implementation of the TCP/IP protocol suite for the LINUX
4 * operating system. INET is implemented using the BSD Socket
5 * interface as the means of communication with the user level.
6 *
7 * The IP fragmentation functionality.
8 *
9 * Authors: Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
10 * Alan Cox <alan@lxorguk.ukuu.org.uk>
11 *
12 * Fixes:
13 * Alan Cox : Split from ip.c , see ip_input.c for history.
14 * David S. Miller : Begin massive cleanup...
15 * Andi Kleen : Add sysctls.
16 * xxxx : Overlapfrag bug.
17 * Ultima : ip_expire() kernel panic.
18 * Bill Hawes : Frag accounting and evictor fixes.
19 * John McDonald : 0 length frag bug.
20 * Alexey Kuznetsov: SMP races, threading, cleanup.
21 * Patrick McHardy : LRU queue of frag heads for evictor.
22 */
23
24#define pr_fmt(fmt) "IPv4: " fmt
25
26#include <linux/compiler.h>
27#include <linux/module.h>
28#include <linux/types.h>
29#include <linux/mm.h>
30#include <linux/jiffies.h>
31#include <linux/skbuff.h>
32#include <linux/list.h>
33#include <linux/ip.h>
34#include <linux/icmp.h>
35#include <linux/netdevice.h>
36#include <linux/jhash.h>
37#include <linux/random.h>
38#include <linux/slab.h>
39#include <net/route.h>
40#include <net/dst.h>
41#include <net/sock.h>
42#include <net/ip.h>
43#include <net/icmp.h>
44#include <net/checksum.h>
45#include <net/inetpeer.h>
46#include <net/inet_frag.h>
47#include <linux/tcp.h>
48#include <linux/udp.h>
49#include <linux/inet.h>
50#include <linux/netfilter_ipv4.h>
51#include <net/inet_ecn.h>
52#include <net/l3mdev.h>
53
54/* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
55 * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
56 * as well. Or notify me, at least. --ANK
57 */
58static const char ip_frag_cache_name[] = "ip4-frags";
59
60/* Describe an entry in the "incomplete datagrams" queue. */
61struct ipq {
62 struct inet_frag_queue q;
63
64 u8 ecn; /* RFC3168 support */
65 u16 max_df_size; /* largest frag with DF set seen */
66 int iif;
67 unsigned int rid;
68 struct inet_peer *peer;
69};
70
71static u8 ip4_frag_ecn(u8 tos)
72{
73 return 1 << (tos & INET_ECN_MASK);
74}
75
76static struct inet_frags ip4_frags;
77
78static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
79 struct sk_buff *prev_tail, struct net_device *dev);
80
81
82static void ip4_frag_init(struct inet_frag_queue *q, const void *a)
83{
84 struct ipq *qp = container_of(q, struct ipq, q);
85 const struct frag_v4_compare_key *key = a;
86 struct net *net = q->fqdir->net;
87 struct inet_peer *p = NULL;
88
89 q->key.v4 = *key;
90 qp->ecn = 0;
91 if (q->fqdir->max_dist) {
92 rcu_read_lock();
93 p = inet_getpeer_v4(net->ipv4.peers, key->saddr, key->vif);
94 if (p && !refcount_inc_not_zero(&p->refcnt))
95 p = NULL;
96 rcu_read_unlock();
97 }
98 qp->peer = p;
99}
100
101static void ip4_frag_free(struct inet_frag_queue *q)
102{
103 struct ipq *qp;
104
105 qp = container_of(q, struct ipq, q);
106 if (qp->peer)
107 inet_putpeer(qp->peer);
108}
109
110
111/* Destruction primitives. */
112
113static void ipq_put(struct ipq *ipq)
114{
115 inet_frag_put(&ipq->q);
116}
117
118/* Kill ipq entry. It is not destroyed immediately,
119 * because caller (and someone more) holds reference count.
120 */
121static void ipq_kill(struct ipq *ipq)
122{
123 inet_frag_kill(&ipq->q);
124}
125
126static bool frag_expire_skip_icmp(u32 user)
127{
128 return user == IP_DEFRAG_AF_PACKET ||
129 ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_IN,
130 __IP_DEFRAG_CONNTRACK_IN_END) ||
131 ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_BRIDGE_IN,
132 __IP_DEFRAG_CONNTRACK_BRIDGE_IN);
133}
134
135/*
136 * Oops, a fragment queue timed out. Kill it and send an ICMP reply.
137 */
138static void ip_expire(struct timer_list *t)
139{
140 enum skb_drop_reason reason = SKB_DROP_REASON_FRAG_REASM_TIMEOUT;
141 struct inet_frag_queue *frag = from_timer(frag, t, timer);
142 const struct iphdr *iph;
143 struct sk_buff *head = NULL;
144 struct net *net;
145 struct ipq *qp;
146
147 qp = container_of(frag, struct ipq, q);
148 net = qp->q.fqdir->net;
149
150 rcu_read_lock();
151
152 /* Paired with WRITE_ONCE() in fqdir_pre_exit(). */
153 if (READ_ONCE(qp->q.fqdir->dead))
154 goto out_rcu_unlock;
155
156 spin_lock(&qp->q.lock);
157
158 if (qp->q.flags & INET_FRAG_COMPLETE)
159 goto out;
160
161 qp->q.flags |= INET_FRAG_DROP;
162 ipq_kill(qp);
163 __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
164 __IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT);
165
166 if (!(qp->q.flags & INET_FRAG_FIRST_IN))
167 goto out;
168
169 /* sk_buff::dev and sk_buff::rbnode are unionized. So we
170 * pull the head out of the tree in order to be able to
171 * deal with head->dev.
172 */
173 head = inet_frag_pull_head(&qp->q);
174 if (!head)
175 goto out;
176 head->dev = dev_get_by_index_rcu(net, qp->iif);
177 if (!head->dev)
178 goto out;
179
180
181 /* skb has no dst, perform route lookup again */
182 iph = ip_hdr(head);
183 reason = ip_route_input_noref(head, iph->daddr, iph->saddr,
184 ip4h_dscp(iph), head->dev);
185 if (reason)
186 goto out;
187
188 /* Only an end host needs to send an ICMP
189 * "Fragment Reassembly Timeout" message, per RFC792.
190 */
191 reason = SKB_DROP_REASON_FRAG_REASM_TIMEOUT;
192 if (frag_expire_skip_icmp(qp->q.key.v4.user) &&
193 (skb_rtable(head)->rt_type != RTN_LOCAL))
194 goto out;
195
196 spin_unlock(&qp->q.lock);
197 icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
198 goto out_rcu_unlock;
199
200out:
201 spin_unlock(&qp->q.lock);
202out_rcu_unlock:
203 rcu_read_unlock();
204 kfree_skb_reason(head, reason);
205 ipq_put(qp);
206}
207
208/* Find the correct entry in the "incomplete datagrams" queue for
209 * this IP datagram, and create new one, if nothing is found.
210 */
211static struct ipq *ip_find(struct net *net, struct iphdr *iph,
212 u32 user, int vif)
213{
214 struct frag_v4_compare_key key = {
215 .saddr = iph->saddr,
216 .daddr = iph->daddr,
217 .user = user,
218 .vif = vif,
219 .id = iph->id,
220 .protocol = iph->protocol,
221 };
222 struct inet_frag_queue *q;
223
224 q = inet_frag_find(net->ipv4.fqdir, &key);
225 if (!q)
226 return NULL;
227
228 return container_of(q, struct ipq, q);
229}
230
231/* Is the fragment too far ahead to be part of ipq? */
232static int ip_frag_too_far(struct ipq *qp)
233{
234 struct inet_peer *peer = qp->peer;
235 unsigned int max = qp->q.fqdir->max_dist;
236 unsigned int start, end;
237
238 int rc;
239
240 if (!peer || !max)
241 return 0;
242
243 start = qp->rid;
244 end = atomic_inc_return(&peer->rid);
245 qp->rid = end;
246
247 rc = qp->q.fragments_tail && (end - start) > max;
248
249 if (rc)
250 __IP_INC_STATS(qp->q.fqdir->net, IPSTATS_MIB_REASMFAILS);
251
252 return rc;
253}
254
255static int ip_frag_reinit(struct ipq *qp)
256{
257 unsigned int sum_truesize = 0;
258
259 if (!mod_timer(&qp->q.timer, jiffies + qp->q.fqdir->timeout)) {
260 refcount_inc(&qp->q.refcnt);
261 return -ETIMEDOUT;
262 }
263
264 sum_truesize = inet_frag_rbtree_purge(&qp->q.rb_fragments,
265 SKB_DROP_REASON_FRAG_TOO_FAR);
266 sub_frag_mem_limit(qp->q.fqdir, sum_truesize);
267
268 qp->q.flags = 0;
269 qp->q.len = 0;
270 qp->q.meat = 0;
271 qp->q.rb_fragments = RB_ROOT;
272 qp->q.fragments_tail = NULL;
273 qp->q.last_run_head = NULL;
274 qp->iif = 0;
275 qp->ecn = 0;
276
277 return 0;
278}
279
280/* Add new segment to existing queue. */
281static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
282{
283 struct net *net = qp->q.fqdir->net;
284 int ihl, end, flags, offset;
285 struct sk_buff *prev_tail;
286 struct net_device *dev;
287 unsigned int fragsize;
288 int err = -ENOENT;
289 SKB_DR(reason);
290 u8 ecn;
291
292 /* If reassembly is already done, @skb must be a duplicate frag. */
293 if (qp->q.flags & INET_FRAG_COMPLETE) {
294 SKB_DR_SET(reason, DUP_FRAG);
295 goto err;
296 }
297
298 if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
299 unlikely(ip_frag_too_far(qp)) &&
300 unlikely(err = ip_frag_reinit(qp))) {
301 ipq_kill(qp);
302 goto err;
303 }
304
305 ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
306 offset = ntohs(ip_hdr(skb)->frag_off);
307 flags = offset & ~IP_OFFSET;
308 offset &= IP_OFFSET;
309 offset <<= 3; /* offset is in 8-byte chunks */
310 ihl = ip_hdrlen(skb);
311
312 /* Determine the position of this fragment. */
313 end = offset + skb->len - skb_network_offset(skb) - ihl;
314 err = -EINVAL;
315
316 /* Is this the final fragment? */
317 if ((flags & IP_MF) == 0) {
318 /* If we already have some bits beyond end
319 * or have different end, the segment is corrupted.
320 */
321 if (end < qp->q.len ||
322 ((qp->q.flags & INET_FRAG_LAST_IN) && end != qp->q.len))
323 goto discard_qp;
324 qp->q.flags |= INET_FRAG_LAST_IN;
325 qp->q.len = end;
326 } else {
327 if (end&7) {
328 end &= ~7;
329 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
330 skb->ip_summed = CHECKSUM_NONE;
331 }
332 if (end > qp->q.len) {
333 /* Some bits beyond end -> corruption. */
334 if (qp->q.flags & INET_FRAG_LAST_IN)
335 goto discard_qp;
336 qp->q.len = end;
337 }
338 }
339 if (end == offset)
340 goto discard_qp;
341
342 err = -ENOMEM;
343 if (!pskb_pull(skb, skb_network_offset(skb) + ihl))
344 goto discard_qp;
345
346 err = pskb_trim_rcsum(skb, end - offset);
347 if (err)
348 goto discard_qp;
349
350 /* Note : skb->rbnode and skb->dev share the same location. */
351 dev = skb->dev;
352 /* Makes sure compiler wont do silly aliasing games */
353 barrier();
354
355 prev_tail = qp->q.fragments_tail;
356 err = inet_frag_queue_insert(&qp->q, skb, offset, end);
357 if (err)
358 goto insert_error;
359
360 if (dev)
361 qp->iif = dev->ifindex;
362
363 qp->q.stamp = skb->tstamp;
364 qp->q.tstamp_type = skb->tstamp_type;
365 qp->q.meat += skb->len;
366 qp->ecn |= ecn;
367 add_frag_mem_limit(qp->q.fqdir, skb->truesize);
368 if (offset == 0)
369 qp->q.flags |= INET_FRAG_FIRST_IN;
370
371 fragsize = skb->len + ihl;
372
373 if (fragsize > qp->q.max_size)
374 qp->q.max_size = fragsize;
375
376 if (ip_hdr(skb)->frag_off & htons(IP_DF) &&
377 fragsize > qp->max_df_size)
378 qp->max_df_size = fragsize;
379
380 if (qp->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
381 qp->q.meat == qp->q.len) {
382 unsigned long orefdst = skb->_skb_refdst;
383
384 skb->_skb_refdst = 0UL;
385 err = ip_frag_reasm(qp, skb, prev_tail, dev);
386 skb->_skb_refdst = orefdst;
387 if (err)
388 inet_frag_kill(&qp->q);
389 return err;
390 }
391
392 skb_dst_drop(skb);
393 skb_orphan(skb);
394 return -EINPROGRESS;
395
396insert_error:
397 if (err == IPFRAG_DUP) {
398 SKB_DR_SET(reason, DUP_FRAG);
399 err = -EINVAL;
400 goto err;
401 }
402 err = -EINVAL;
403 __IP_INC_STATS(net, IPSTATS_MIB_REASM_OVERLAPS);
404discard_qp:
405 inet_frag_kill(&qp->q);
406 __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
407err:
408 kfree_skb_reason(skb, reason);
409 return err;
410}
411
412static bool ip_frag_coalesce_ok(const struct ipq *qp)
413{
414 return qp->q.key.v4.user == IP_DEFRAG_LOCAL_DELIVER;
415}
416
417/* Build a new IP datagram from all its fragments. */
418static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
419 struct sk_buff *prev_tail, struct net_device *dev)
420{
421 struct net *net = qp->q.fqdir->net;
422 struct iphdr *iph;
423 void *reasm_data;
424 int len, err;
425 u8 ecn;
426
427 ipq_kill(qp);
428
429 ecn = ip_frag_ecn_table[qp->ecn];
430 if (unlikely(ecn == 0xff)) {
431 err = -EINVAL;
432 goto out_fail;
433 }
434
435 /* Make the one we just received the head. */
436 reasm_data = inet_frag_reasm_prepare(&qp->q, skb, prev_tail);
437 if (!reasm_data)
438 goto out_nomem;
439
440 len = ip_hdrlen(skb) + qp->q.len;
441 err = -E2BIG;
442 if (len > 65535)
443 goto out_oversize;
444
445 inet_frag_reasm_finish(&qp->q, skb, reasm_data,
446 ip_frag_coalesce_ok(qp));
447
448 skb->dev = dev;
449 IPCB(skb)->frag_max_size = max(qp->max_df_size, qp->q.max_size);
450
451 iph = ip_hdr(skb);
452 iph->tot_len = htons(len);
453 iph->tos |= ecn;
454
455 /* When we set IP_DF on a refragmented skb we must also force a
456 * call to ip_fragment to avoid forwarding a DF-skb of size s while
457 * original sender only sent fragments of size f (where f < s).
458 *
459 * We only set DF/IPSKB_FRAG_PMTU if such DF fragment was the largest
460 * frag seen to avoid sending tiny DF-fragments in case skb was built
461 * from one very small df-fragment and one large non-df frag.
462 */
463 if (qp->max_df_size == qp->q.max_size) {
464 IPCB(skb)->flags |= IPSKB_FRAG_PMTU;
465 iph->frag_off = htons(IP_DF);
466 } else {
467 iph->frag_off = 0;
468 }
469
470 ip_send_check(iph);
471
472 __IP_INC_STATS(net, IPSTATS_MIB_REASMOKS);
473 qp->q.rb_fragments = RB_ROOT;
474 qp->q.fragments_tail = NULL;
475 qp->q.last_run_head = NULL;
476 return 0;
477
478out_nomem:
479 net_dbg_ratelimited("queue_glue: no memory for gluing queue %p\n", qp);
480 err = -ENOMEM;
481 goto out_fail;
482out_oversize:
483 net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->q.key.v4.saddr);
484out_fail:
485 __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
486 return err;
487}
488
489/* Process an incoming IP datagram fragment. */
490int ip_defrag(struct net *net, struct sk_buff *skb, u32 user)
491{
492 struct net_device *dev = skb->dev ? : skb_dst(skb)->dev;
493 int vif = l3mdev_master_ifindex_rcu(dev);
494 struct ipq *qp;
495
496 __IP_INC_STATS(net, IPSTATS_MIB_REASMREQDS);
497
498 /* Lookup (or create) queue header */
499 qp = ip_find(net, ip_hdr(skb), user, vif);
500 if (qp) {
501 int ret;
502
503 spin_lock(&qp->q.lock);
504
505 ret = ip_frag_queue(qp, skb);
506
507 spin_unlock(&qp->q.lock);
508 ipq_put(qp);
509 return ret;
510 }
511
512 __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
513 kfree_skb(skb);
514 return -ENOMEM;
515}
516EXPORT_SYMBOL(ip_defrag);
517
518struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user)
519{
520 struct iphdr iph;
521 int netoff;
522 u32 len;
523
524 if (skb->protocol != htons(ETH_P_IP))
525 return skb;
526
527 netoff = skb_network_offset(skb);
528
529 if (skb_copy_bits(skb, netoff, &iph, sizeof(iph)) < 0)
530 return skb;
531
532 if (iph.ihl < 5 || iph.version != 4)
533 return skb;
534
535 len = ntohs(iph.tot_len);
536 if (skb->len < netoff + len || len < (iph.ihl * 4))
537 return skb;
538
539 if (ip_is_fragment(&iph)) {
540 skb = skb_share_check(skb, GFP_ATOMIC);
541 if (skb) {
542 if (!pskb_may_pull(skb, netoff + iph.ihl * 4)) {
543 kfree_skb(skb);
544 return NULL;
545 }
546 if (pskb_trim_rcsum(skb, netoff + len)) {
547 kfree_skb(skb);
548 return NULL;
549 }
550 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
551 if (ip_defrag(net, skb, user))
552 return NULL;
553 skb_clear_hash(skb);
554 }
555 }
556 return skb;
557}
558EXPORT_SYMBOL(ip_check_defrag);
559
560#ifdef CONFIG_SYSCTL
561static int dist_min;
562
563static struct ctl_table ip4_frags_ns_ctl_table[] = {
564 {
565 .procname = "ipfrag_high_thresh",
566 .maxlen = sizeof(unsigned long),
567 .mode = 0644,
568 .proc_handler = proc_doulongvec_minmax,
569 },
570 {
571 .procname = "ipfrag_low_thresh",
572 .maxlen = sizeof(unsigned long),
573 .mode = 0644,
574 .proc_handler = proc_doulongvec_minmax,
575 },
576 {
577 .procname = "ipfrag_time",
578 .maxlen = sizeof(int),
579 .mode = 0644,
580 .proc_handler = proc_dointvec_jiffies,
581 },
582 {
583 .procname = "ipfrag_max_dist",
584 .maxlen = sizeof(int),
585 .mode = 0644,
586 .proc_handler = proc_dointvec_minmax,
587 .extra1 = &dist_min,
588 },
589};
590
591/* secret interval has been deprecated */
592static int ip4_frags_secret_interval_unused;
593static struct ctl_table ip4_frags_ctl_table[] = {
594 {
595 .procname = "ipfrag_secret_interval",
596 .data = &ip4_frags_secret_interval_unused,
597 .maxlen = sizeof(int),
598 .mode = 0644,
599 .proc_handler = proc_dointvec_jiffies,
600 },
601};
602
603static int __net_init ip4_frags_ns_ctl_register(struct net *net)
604{
605 struct ctl_table *table;
606 struct ctl_table_header *hdr;
607
608 table = ip4_frags_ns_ctl_table;
609 if (!net_eq(net, &init_net)) {
610 table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
611 if (!table)
612 goto err_alloc;
613
614 }
615 table[0].data = &net->ipv4.fqdir->high_thresh;
616 table[0].extra1 = &net->ipv4.fqdir->low_thresh;
617 table[1].data = &net->ipv4.fqdir->low_thresh;
618 table[1].extra2 = &net->ipv4.fqdir->high_thresh;
619 table[2].data = &net->ipv4.fqdir->timeout;
620 table[3].data = &net->ipv4.fqdir->max_dist;
621
622 hdr = register_net_sysctl_sz(net, "net/ipv4", table,
623 ARRAY_SIZE(ip4_frags_ns_ctl_table));
624 if (!hdr)
625 goto err_reg;
626
627 net->ipv4.frags_hdr = hdr;
628 return 0;
629
630err_reg:
631 if (!net_eq(net, &init_net))
632 kfree(table);
633err_alloc:
634 return -ENOMEM;
635}
636
637static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
638{
639 const struct ctl_table *table;
640
641 table = net->ipv4.frags_hdr->ctl_table_arg;
642 unregister_net_sysctl_table(net->ipv4.frags_hdr);
643 kfree(table);
644}
645
646static void __init ip4_frags_ctl_register(void)
647{
648 register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
649}
650#else
651static int ip4_frags_ns_ctl_register(struct net *net)
652{
653 return 0;
654}
655
656static void ip4_frags_ns_ctl_unregister(struct net *net)
657{
658}
659
660static void __init ip4_frags_ctl_register(void)
661{
662}
663#endif
664
665static int __net_init ipv4_frags_init_net(struct net *net)
666{
667 int res;
668
669 res = fqdir_init(&net->ipv4.fqdir, &ip4_frags, net);
670 if (res < 0)
671 return res;
672 /* Fragment cache limits.
673 *
674 * The fragment memory accounting code, (tries to) account for
675 * the real memory usage, by measuring both the size of frag
676 * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue))
677 * and the SKB's truesize.
678 *
679 * A 64K fragment consumes 129736 bytes (44*2944)+200
680 * (1500 truesize == 2944, sizeof(struct ipq) == 200)
681 *
682 * We will commit 4MB at one time. Should we cross that limit
683 * we will prune down to 3MB, making room for approx 8 big 64K
684 * fragments 8x128k.
685 */
686 net->ipv4.fqdir->high_thresh = 4 * 1024 * 1024;
687 net->ipv4.fqdir->low_thresh = 3 * 1024 * 1024;
688 /*
689 * Important NOTE! Fragment queue must be destroyed before MSL expires.
690 * RFC791 is wrong proposing to prolongate timer each fragment arrival
691 * by TTL.
692 */
693 net->ipv4.fqdir->timeout = IP_FRAG_TIME;
694
695 net->ipv4.fqdir->max_dist = 64;
696
697 res = ip4_frags_ns_ctl_register(net);
698 if (res < 0)
699 fqdir_exit(net->ipv4.fqdir);
700 return res;
701}
702
703static void __net_exit ipv4_frags_pre_exit_net(struct net *net)
704{
705 fqdir_pre_exit(net->ipv4.fqdir);
706}
707
708static void __net_exit ipv4_frags_exit_net(struct net *net)
709{
710 ip4_frags_ns_ctl_unregister(net);
711 fqdir_exit(net->ipv4.fqdir);
712}
713
714static struct pernet_operations ip4_frags_ops = {
715 .init = ipv4_frags_init_net,
716 .pre_exit = ipv4_frags_pre_exit_net,
717 .exit = ipv4_frags_exit_net,
718};
719
720
721static u32 ip4_key_hashfn(const void *data, u32 len, u32 seed)
722{
723 return jhash2(data,
724 sizeof(struct frag_v4_compare_key) / sizeof(u32), seed);
725}
726
727static u32 ip4_obj_hashfn(const void *data, u32 len, u32 seed)
728{
729 const struct inet_frag_queue *fq = data;
730
731 return jhash2((const u32 *)&fq->key.v4,
732 sizeof(struct frag_v4_compare_key) / sizeof(u32), seed);
733}
734
735static int ip4_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr)
736{
737 const struct frag_v4_compare_key *key = arg->key;
738 const struct inet_frag_queue *fq = ptr;
739
740 return !!memcmp(&fq->key, key, sizeof(*key));
741}
742
743static const struct rhashtable_params ip4_rhash_params = {
744 .head_offset = offsetof(struct inet_frag_queue, node),
745 .key_offset = offsetof(struct inet_frag_queue, key),
746 .key_len = sizeof(struct frag_v4_compare_key),
747 .hashfn = ip4_key_hashfn,
748 .obj_hashfn = ip4_obj_hashfn,
749 .obj_cmpfn = ip4_obj_cmpfn,
750 .automatic_shrinking = true,
751};
752
753void __init ipfrag_init(void)
754{
755 ip4_frags.constructor = ip4_frag_init;
756 ip4_frags.destructor = ip4_frag_free;
757 ip4_frags.qsize = sizeof(struct ipq);
758 ip4_frags.frag_expire = ip_expire;
759 ip4_frags.frags_cache_name = ip_frag_cache_name;
760 ip4_frags.rhash_params = ip4_rhash_params;
761 if (inet_frags_init(&ip4_frags))
762 panic("IP: failed to allocate ip4_frags cache\n");
763 ip4_frags_ctl_register();
764 register_pernet_subsys(&ip4_frags_ops);
765}
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 IP fragmentation functionality.
7 *
8 * Authors: Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
9 * Alan Cox <alan@lxorguk.ukuu.org.uk>
10 *
11 * Fixes:
12 * Alan Cox : Split from ip.c , see ip_input.c for history.
13 * David S. Miller : Begin massive cleanup...
14 * Andi Kleen : Add sysctls.
15 * xxxx : Overlapfrag bug.
16 * Ultima : ip_expire() kernel panic.
17 * Bill Hawes : Frag accounting and evictor fixes.
18 * John McDonald : 0 length frag bug.
19 * Alexey Kuznetsov: SMP races, threading, cleanup.
20 * Patrick McHardy : LRU queue of frag heads for evictor.
21 */
22
23#include <linux/compiler.h>
24#include <linux/module.h>
25#include <linux/types.h>
26#include <linux/mm.h>
27#include <linux/jiffies.h>
28#include <linux/skbuff.h>
29#include <linux/list.h>
30#include <linux/ip.h>
31#include <linux/icmp.h>
32#include <linux/netdevice.h>
33#include <linux/jhash.h>
34#include <linux/random.h>
35#include <linux/slab.h>
36#include <net/route.h>
37#include <net/dst.h>
38#include <net/sock.h>
39#include <net/ip.h>
40#include <net/icmp.h>
41#include <net/checksum.h>
42#include <net/inetpeer.h>
43#include <net/inet_frag.h>
44#include <linux/tcp.h>
45#include <linux/udp.h>
46#include <linux/inet.h>
47#include <linux/netfilter_ipv4.h>
48#include <net/inet_ecn.h>
49
50/* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
51 * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
52 * as well. Or notify me, at least. --ANK
53 */
54
55static int sysctl_ipfrag_max_dist __read_mostly = 64;
56
57struct ipfrag_skb_cb
58{
59 struct inet_skb_parm h;
60 int offset;
61};
62
63#define FRAG_CB(skb) ((struct ipfrag_skb_cb *)((skb)->cb))
64
65/* Describe an entry in the "incomplete datagrams" queue. */
66struct ipq {
67 struct inet_frag_queue q;
68
69 u32 user;
70 __be32 saddr;
71 __be32 daddr;
72 __be16 id;
73 u8 protocol;
74 u8 ecn; /* RFC3168 support */
75 int iif;
76 unsigned int rid;
77 struct inet_peer *peer;
78};
79
80/* RFC 3168 support :
81 * We want to check ECN values of all fragments, do detect invalid combinations.
82 * In ipq->ecn, we store the OR value of each ip4_frag_ecn() fragment value.
83 */
84#define IPFRAG_ECN_NOT_ECT 0x01 /* one frag had ECN_NOT_ECT */
85#define IPFRAG_ECN_ECT_1 0x02 /* one frag had ECN_ECT_1 */
86#define IPFRAG_ECN_ECT_0 0x04 /* one frag had ECN_ECT_0 */
87#define IPFRAG_ECN_CE 0x08 /* one frag had ECN_CE */
88
89static inline u8 ip4_frag_ecn(u8 tos)
90{
91 return 1 << (tos & INET_ECN_MASK);
92}
93
94/* Given the OR values of all fragments, apply RFC 3168 5.3 requirements
95 * Value : 0xff if frame should be dropped.
96 * 0 or INET_ECN_CE value, to be ORed in to final iph->tos field
97 */
98static const u8 ip4_frag_ecn_table[16] = {
99 /* at least one fragment had CE, and others ECT_0 or ECT_1 */
100 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = INET_ECN_CE,
101 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = INET_ECN_CE,
102 [IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = INET_ECN_CE,
103
104 /* invalid combinations : drop frame */
105 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE] = 0xff,
106 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0] = 0xff,
107 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_1] = 0xff,
108 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
109 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0] = 0xff,
110 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_1] = 0xff,
111 [IPFRAG_ECN_NOT_ECT | IPFRAG_ECN_CE | IPFRAG_ECN_ECT_0 | IPFRAG_ECN_ECT_1] = 0xff,
112};
113
114static struct inet_frags ip4_frags;
115
116int ip_frag_nqueues(struct net *net)
117{
118 return net->ipv4.frags.nqueues;
119}
120
121int ip_frag_mem(struct net *net)
122{
123 return atomic_read(&net->ipv4.frags.mem);
124}
125
126static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
127 struct net_device *dev);
128
129struct ip4_create_arg {
130 struct iphdr *iph;
131 u32 user;
132};
133
134static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
135{
136 return jhash_3words((__force u32)id << 16 | prot,
137 (__force u32)saddr, (__force u32)daddr,
138 ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1);
139}
140
141static unsigned int ip4_hashfn(struct inet_frag_queue *q)
142{
143 struct ipq *ipq;
144
145 ipq = container_of(q, struct ipq, q);
146 return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);
147}
148
149static int ip4_frag_match(struct inet_frag_queue *q, void *a)
150{
151 struct ipq *qp;
152 struct ip4_create_arg *arg = a;
153
154 qp = container_of(q, struct ipq, q);
155 return qp->id == arg->iph->id &&
156 qp->saddr == arg->iph->saddr &&
157 qp->daddr == arg->iph->daddr &&
158 qp->protocol == arg->iph->protocol &&
159 qp->user == arg->user;
160}
161
162/* Memory Tracking Functions. */
163static void frag_kfree_skb(struct netns_frags *nf, struct sk_buff *skb)
164{
165 atomic_sub(skb->truesize, &nf->mem);
166 kfree_skb(skb);
167}
168
169static void ip4_frag_init(struct inet_frag_queue *q, void *a)
170{
171 struct ipq *qp = container_of(q, struct ipq, q);
172 struct ip4_create_arg *arg = a;
173
174 qp->protocol = arg->iph->protocol;
175 qp->id = arg->iph->id;
176 qp->ecn = ip4_frag_ecn(arg->iph->tos);
177 qp->saddr = arg->iph->saddr;
178 qp->daddr = arg->iph->daddr;
179 qp->user = arg->user;
180 qp->peer = sysctl_ipfrag_max_dist ?
181 inet_getpeer_v4(arg->iph->saddr, 1) : NULL;
182}
183
184static __inline__ void ip4_frag_free(struct inet_frag_queue *q)
185{
186 struct ipq *qp;
187
188 qp = container_of(q, struct ipq, q);
189 if (qp->peer)
190 inet_putpeer(qp->peer);
191}
192
193
194/* Destruction primitives. */
195
196static __inline__ void ipq_put(struct ipq *ipq)
197{
198 inet_frag_put(&ipq->q, &ip4_frags);
199}
200
201/* Kill ipq entry. It is not destroyed immediately,
202 * because caller (and someone more) holds reference count.
203 */
204static void ipq_kill(struct ipq *ipq)
205{
206 inet_frag_kill(&ipq->q, &ip4_frags);
207}
208
209/* Memory limiting on fragments. Evictor trashes the oldest
210 * fragment queue until we are back under the threshold.
211 */
212static void ip_evictor(struct net *net)
213{
214 int evicted;
215
216 evicted = inet_frag_evictor(&net->ipv4.frags, &ip4_frags);
217 if (evicted)
218 IP_ADD_STATS_BH(net, IPSTATS_MIB_REASMFAILS, evicted);
219}
220
221/*
222 * Oops, a fragment queue timed out. Kill it and send an ICMP reply.
223 */
224static void ip_expire(unsigned long arg)
225{
226 struct ipq *qp;
227 struct net *net;
228
229 qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);
230 net = container_of(qp->q.net, struct net, ipv4.frags);
231
232 spin_lock(&qp->q.lock);
233
234 if (qp->q.last_in & INET_FRAG_COMPLETE)
235 goto out;
236
237 ipq_kill(qp);
238
239 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMTIMEOUT);
240 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
241
242 if ((qp->q.last_in & INET_FRAG_FIRST_IN) && qp->q.fragments != NULL) {
243 struct sk_buff *head = qp->q.fragments;
244 const struct iphdr *iph;
245 int err;
246
247 rcu_read_lock();
248 head->dev = dev_get_by_index_rcu(net, qp->iif);
249 if (!head->dev)
250 goto out_rcu_unlock;
251
252 /* skb dst is stale, drop it, and perform route lookup again */
253 skb_dst_drop(head);
254 iph = ip_hdr(head);
255 err = ip_route_input_noref(head, iph->daddr, iph->saddr,
256 iph->tos, head->dev);
257 if (err)
258 goto out_rcu_unlock;
259
260 /*
261 * Only an end host needs to send an ICMP
262 * "Fragment Reassembly Timeout" message, per RFC792.
263 */
264 if (qp->user == IP_DEFRAG_AF_PACKET ||
265 (qp->user == IP_DEFRAG_CONNTRACK_IN &&
266 skb_rtable(head)->rt_type != RTN_LOCAL))
267 goto out_rcu_unlock;
268
269
270 /* Send an ICMP "Fragment Reassembly Timeout" message. */
271 icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
272out_rcu_unlock:
273 rcu_read_unlock();
274 }
275out:
276 spin_unlock(&qp->q.lock);
277 ipq_put(qp);
278}
279
280/* Find the correct entry in the "incomplete datagrams" queue for
281 * this IP datagram, and create new one, if nothing is found.
282 */
283static inline struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user)
284{
285 struct inet_frag_queue *q;
286 struct ip4_create_arg arg;
287 unsigned int hash;
288
289 arg.iph = iph;
290 arg.user = user;
291
292 read_lock(&ip4_frags.lock);
293 hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
294
295 q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);
296 if (q == NULL)
297 goto out_nomem;
298
299 return container_of(q, struct ipq, q);
300
301out_nomem:
302 LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n");
303 return NULL;
304}
305
306/* Is the fragment too far ahead to be part of ipq? */
307static inline int ip_frag_too_far(struct ipq *qp)
308{
309 struct inet_peer *peer = qp->peer;
310 unsigned int max = sysctl_ipfrag_max_dist;
311 unsigned int start, end;
312
313 int rc;
314
315 if (!peer || !max)
316 return 0;
317
318 start = qp->rid;
319 end = atomic_inc_return(&peer->rid);
320 qp->rid = end;
321
322 rc = qp->q.fragments && (end - start) > max;
323
324 if (rc) {
325 struct net *net;
326
327 net = container_of(qp->q.net, struct net, ipv4.frags);
328 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
329 }
330
331 return rc;
332}
333
334static int ip_frag_reinit(struct ipq *qp)
335{
336 struct sk_buff *fp;
337
338 if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
339 atomic_inc(&qp->q.refcnt);
340 return -ETIMEDOUT;
341 }
342
343 fp = qp->q.fragments;
344 do {
345 struct sk_buff *xp = fp->next;
346 frag_kfree_skb(qp->q.net, fp);
347 fp = xp;
348 } while (fp);
349
350 qp->q.last_in = 0;
351 qp->q.len = 0;
352 qp->q.meat = 0;
353 qp->q.fragments = NULL;
354 qp->q.fragments_tail = NULL;
355 qp->iif = 0;
356 qp->ecn = 0;
357
358 return 0;
359}
360
361/* Add new segment to existing queue. */
362static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
363{
364 struct sk_buff *prev, *next;
365 struct net_device *dev;
366 int flags, offset;
367 int ihl, end;
368 int err = -ENOENT;
369 u8 ecn;
370
371 if (qp->q.last_in & INET_FRAG_COMPLETE)
372 goto err;
373
374 if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
375 unlikely(ip_frag_too_far(qp)) &&
376 unlikely(err = ip_frag_reinit(qp))) {
377 ipq_kill(qp);
378 goto err;
379 }
380
381 ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
382 offset = ntohs(ip_hdr(skb)->frag_off);
383 flags = offset & ~IP_OFFSET;
384 offset &= IP_OFFSET;
385 offset <<= 3; /* offset is in 8-byte chunks */
386 ihl = ip_hdrlen(skb);
387
388 /* Determine the position of this fragment. */
389 end = offset + skb->len - ihl;
390 err = -EINVAL;
391
392 /* Is this the final fragment? */
393 if ((flags & IP_MF) == 0) {
394 /* If we already have some bits beyond end
395 * or have different end, the segment is corrrupted.
396 */
397 if (end < qp->q.len ||
398 ((qp->q.last_in & INET_FRAG_LAST_IN) && end != qp->q.len))
399 goto err;
400 qp->q.last_in |= INET_FRAG_LAST_IN;
401 qp->q.len = end;
402 } else {
403 if (end&7) {
404 end &= ~7;
405 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
406 skb->ip_summed = CHECKSUM_NONE;
407 }
408 if (end > qp->q.len) {
409 /* Some bits beyond end -> corruption. */
410 if (qp->q.last_in & INET_FRAG_LAST_IN)
411 goto err;
412 qp->q.len = end;
413 }
414 }
415 if (end == offset)
416 goto err;
417
418 err = -ENOMEM;
419 if (pskb_pull(skb, ihl) == NULL)
420 goto err;
421
422 err = pskb_trim_rcsum(skb, end - offset);
423 if (err)
424 goto err;
425
426 /* Find out which fragments are in front and at the back of us
427 * in the chain of fragments so far. We must know where to put
428 * this fragment, right?
429 */
430 prev = qp->q.fragments_tail;
431 if (!prev || FRAG_CB(prev)->offset < offset) {
432 next = NULL;
433 goto found;
434 }
435 prev = NULL;
436 for (next = qp->q.fragments; next != NULL; next = next->next) {
437 if (FRAG_CB(next)->offset >= offset)
438 break; /* bingo! */
439 prev = next;
440 }
441
442found:
443 /* We found where to put this one. Check for overlap with
444 * preceding fragment, and, if needed, align things so that
445 * any overlaps are eliminated.
446 */
447 if (prev) {
448 int i = (FRAG_CB(prev)->offset + prev->len) - offset;
449
450 if (i > 0) {
451 offset += i;
452 err = -EINVAL;
453 if (end <= offset)
454 goto err;
455 err = -ENOMEM;
456 if (!pskb_pull(skb, i))
457 goto err;
458 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
459 skb->ip_summed = CHECKSUM_NONE;
460 }
461 }
462
463 err = -ENOMEM;
464
465 while (next && FRAG_CB(next)->offset < end) {
466 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
467
468 if (i < next->len) {
469 /* Eat head of the next overlapped fragment
470 * and leave the loop. The next ones cannot overlap.
471 */
472 if (!pskb_pull(next, i))
473 goto err;
474 FRAG_CB(next)->offset += i;
475 qp->q.meat -= i;
476 if (next->ip_summed != CHECKSUM_UNNECESSARY)
477 next->ip_summed = CHECKSUM_NONE;
478 break;
479 } else {
480 struct sk_buff *free_it = next;
481
482 /* Old fragment is completely overridden with
483 * new one drop it.
484 */
485 next = next->next;
486
487 if (prev)
488 prev->next = next;
489 else
490 qp->q.fragments = next;
491
492 qp->q.meat -= free_it->len;
493 frag_kfree_skb(qp->q.net, free_it);
494 }
495 }
496
497 FRAG_CB(skb)->offset = offset;
498
499 /* Insert this fragment in the chain of fragments. */
500 skb->next = next;
501 if (!next)
502 qp->q.fragments_tail = skb;
503 if (prev)
504 prev->next = skb;
505 else
506 qp->q.fragments = skb;
507
508 dev = skb->dev;
509 if (dev) {
510 qp->iif = dev->ifindex;
511 skb->dev = NULL;
512 }
513 qp->q.stamp = skb->tstamp;
514 qp->q.meat += skb->len;
515 qp->ecn |= ecn;
516 atomic_add(skb->truesize, &qp->q.net->mem);
517 if (offset == 0)
518 qp->q.last_in |= INET_FRAG_FIRST_IN;
519
520 if (qp->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
521 qp->q.meat == qp->q.len)
522 return ip_frag_reasm(qp, prev, dev);
523
524 write_lock(&ip4_frags.lock);
525 list_move_tail(&qp->q.lru_list, &qp->q.net->lru_list);
526 write_unlock(&ip4_frags.lock);
527 return -EINPROGRESS;
528
529err:
530 kfree_skb(skb);
531 return err;
532}
533
534
535/* Build a new IP datagram from all its fragments. */
536
537static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
538 struct net_device *dev)
539{
540 struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
541 struct iphdr *iph;
542 struct sk_buff *fp, *head = qp->q.fragments;
543 int len;
544 int ihlen;
545 int err;
546 u8 ecn;
547
548 ipq_kill(qp);
549
550 ecn = ip4_frag_ecn_table[qp->ecn];
551 if (unlikely(ecn == 0xff)) {
552 err = -EINVAL;
553 goto out_fail;
554 }
555 /* Make the one we just received the head. */
556 if (prev) {
557 head = prev->next;
558 fp = skb_clone(head, GFP_ATOMIC);
559 if (!fp)
560 goto out_nomem;
561
562 fp->next = head->next;
563 if (!fp->next)
564 qp->q.fragments_tail = fp;
565 prev->next = fp;
566
567 skb_morph(head, qp->q.fragments);
568 head->next = qp->q.fragments->next;
569
570 kfree_skb(qp->q.fragments);
571 qp->q.fragments = head;
572 }
573
574 WARN_ON(head == NULL);
575 WARN_ON(FRAG_CB(head)->offset != 0);
576
577 /* Allocate a new buffer for the datagram. */
578 ihlen = ip_hdrlen(head);
579 len = ihlen + qp->q.len;
580
581 err = -E2BIG;
582 if (len > 65535)
583 goto out_oversize;
584
585 /* Head of list must not be cloned. */
586 if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC))
587 goto out_nomem;
588
589 /* If the first fragment is fragmented itself, we split
590 * it to two chunks: the first with data and paged part
591 * and the second, holding only fragments. */
592 if (skb_has_frag_list(head)) {
593 struct sk_buff *clone;
594 int i, plen = 0;
595
596 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
597 goto out_nomem;
598 clone->next = head->next;
599 head->next = clone;
600 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
601 skb_frag_list_init(head);
602 for (i=0; i<skb_shinfo(head)->nr_frags; i++)
603 plen += skb_shinfo(head)->frags[i].size;
604 clone->len = clone->data_len = head->data_len - plen;
605 head->data_len -= clone->len;
606 head->len -= clone->len;
607 clone->csum = 0;
608 clone->ip_summed = head->ip_summed;
609 atomic_add(clone->truesize, &qp->q.net->mem);
610 }
611
612 skb_shinfo(head)->frag_list = head->next;
613 skb_push(head, head->data - skb_network_header(head));
614
615 for (fp=head->next; fp; fp = fp->next) {
616 head->data_len += fp->len;
617 head->len += fp->len;
618 if (head->ip_summed != fp->ip_summed)
619 head->ip_summed = CHECKSUM_NONE;
620 else if (head->ip_summed == CHECKSUM_COMPLETE)
621 head->csum = csum_add(head->csum, fp->csum);
622 head->truesize += fp->truesize;
623 }
624 atomic_sub(head->truesize, &qp->q.net->mem);
625
626 head->next = NULL;
627 head->dev = dev;
628 head->tstamp = qp->q.stamp;
629
630 iph = ip_hdr(head);
631 iph->frag_off = 0;
632 iph->tot_len = htons(len);
633 iph->tos |= ecn;
634 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS);
635 qp->q.fragments = NULL;
636 qp->q.fragments_tail = NULL;
637 return 0;
638
639out_nomem:
640 LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing "
641 "queue %p\n", qp);
642 err = -ENOMEM;
643 goto out_fail;
644out_oversize:
645 if (net_ratelimit())
646 printk(KERN_INFO "Oversized IP packet from %pI4.\n",
647 &qp->saddr);
648out_fail:
649 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
650 return err;
651}
652
653/* Process an incoming IP datagram fragment. */
654int ip_defrag(struct sk_buff *skb, u32 user)
655{
656 struct ipq *qp;
657 struct net *net;
658
659 net = skb->dev ? dev_net(skb->dev) : dev_net(skb_dst(skb)->dev);
660 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMREQDS);
661
662 /* Start by cleaning up the memory. */
663 if (atomic_read(&net->ipv4.frags.mem) > net->ipv4.frags.high_thresh)
664 ip_evictor(net);
665
666 /* Lookup (or create) queue header */
667 if ((qp = ip_find(net, ip_hdr(skb), user)) != NULL) {
668 int ret;
669
670 spin_lock(&qp->q.lock);
671
672 ret = ip_frag_queue(qp, skb);
673
674 spin_unlock(&qp->q.lock);
675 ipq_put(qp);
676 return ret;
677 }
678
679 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
680 kfree_skb(skb);
681 return -ENOMEM;
682}
683EXPORT_SYMBOL(ip_defrag);
684
685#ifdef CONFIG_SYSCTL
686static int zero;
687
688static struct ctl_table ip4_frags_ns_ctl_table[] = {
689 {
690 .procname = "ipfrag_high_thresh",
691 .data = &init_net.ipv4.frags.high_thresh,
692 .maxlen = sizeof(int),
693 .mode = 0644,
694 .proc_handler = proc_dointvec
695 },
696 {
697 .procname = "ipfrag_low_thresh",
698 .data = &init_net.ipv4.frags.low_thresh,
699 .maxlen = sizeof(int),
700 .mode = 0644,
701 .proc_handler = proc_dointvec
702 },
703 {
704 .procname = "ipfrag_time",
705 .data = &init_net.ipv4.frags.timeout,
706 .maxlen = sizeof(int),
707 .mode = 0644,
708 .proc_handler = proc_dointvec_jiffies,
709 },
710 { }
711};
712
713static struct ctl_table ip4_frags_ctl_table[] = {
714 {
715 .procname = "ipfrag_secret_interval",
716 .data = &ip4_frags.secret_interval,
717 .maxlen = sizeof(int),
718 .mode = 0644,
719 .proc_handler = proc_dointvec_jiffies,
720 },
721 {
722 .procname = "ipfrag_max_dist",
723 .data = &sysctl_ipfrag_max_dist,
724 .maxlen = sizeof(int),
725 .mode = 0644,
726 .proc_handler = proc_dointvec_minmax,
727 .extra1 = &zero
728 },
729 { }
730};
731
732static int __net_init ip4_frags_ns_ctl_register(struct net *net)
733{
734 struct ctl_table *table;
735 struct ctl_table_header *hdr;
736
737 table = ip4_frags_ns_ctl_table;
738 if (!net_eq(net, &init_net)) {
739 table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
740 if (table == NULL)
741 goto err_alloc;
742
743 table[0].data = &net->ipv4.frags.high_thresh;
744 table[1].data = &net->ipv4.frags.low_thresh;
745 table[2].data = &net->ipv4.frags.timeout;
746 }
747
748 hdr = register_net_sysctl_table(net, net_ipv4_ctl_path, table);
749 if (hdr == NULL)
750 goto err_reg;
751
752 net->ipv4.frags_hdr = hdr;
753 return 0;
754
755err_reg:
756 if (!net_eq(net, &init_net))
757 kfree(table);
758err_alloc:
759 return -ENOMEM;
760}
761
762static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
763{
764 struct ctl_table *table;
765
766 table = net->ipv4.frags_hdr->ctl_table_arg;
767 unregister_net_sysctl_table(net->ipv4.frags_hdr);
768 kfree(table);
769}
770
771static void ip4_frags_ctl_register(void)
772{
773 register_net_sysctl_rotable(net_ipv4_ctl_path, ip4_frags_ctl_table);
774}
775#else
776static inline int ip4_frags_ns_ctl_register(struct net *net)
777{
778 return 0;
779}
780
781static inline void ip4_frags_ns_ctl_unregister(struct net *net)
782{
783}
784
785static inline void ip4_frags_ctl_register(void)
786{
787}
788#endif
789
790static int __net_init ipv4_frags_init_net(struct net *net)
791{
792 /*
793 * Fragment cache limits. We will commit 256K at one time. Should we
794 * cross that limit we will prune down to 192K. This should cope with
795 * even the most extreme cases without allowing an attacker to
796 * measurably harm machine performance.
797 */
798 net->ipv4.frags.high_thresh = 256 * 1024;
799 net->ipv4.frags.low_thresh = 192 * 1024;
800 /*
801 * Important NOTE! Fragment queue must be destroyed before MSL expires.
802 * RFC791 is wrong proposing to prolongate timer each fragment arrival
803 * by TTL.
804 */
805 net->ipv4.frags.timeout = IP_FRAG_TIME;
806
807 inet_frags_init_net(&net->ipv4.frags);
808
809 return ip4_frags_ns_ctl_register(net);
810}
811
812static void __net_exit ipv4_frags_exit_net(struct net *net)
813{
814 ip4_frags_ns_ctl_unregister(net);
815 inet_frags_exit_net(&net->ipv4.frags, &ip4_frags);
816}
817
818static struct pernet_operations ip4_frags_ops = {
819 .init = ipv4_frags_init_net,
820 .exit = ipv4_frags_exit_net,
821};
822
823void __init ipfrag_init(void)
824{
825 ip4_frags_ctl_register();
826 register_pernet_subsys(&ip4_frags_ops);
827 ip4_frags.hashfn = ip4_hashfn;
828 ip4_frags.constructor = ip4_frag_init;
829 ip4_frags.destructor = ip4_frag_free;
830 ip4_frags.skb_free = NULL;
831 ip4_frags.qsize = sizeof(struct ipq);
832 ip4_frags.match = ip4_frag_match;
833 ip4_frags.frag_expire = ip_expire;
834 ip4_frags.secret_interval = 10 * 60 * HZ;
835 inet_frags_init(&ip4_frags);
836}