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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 *prev,
79 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 struct netns_ipv4 *ipv4 = container_of(q->net, struct netns_ipv4,
86 frags);
87 struct net *net = container_of(ipv4, struct net, ipv4);
88
89 const struct frag_v4_compare_key *key = a;
90
91 q->key.v4 = *key;
92 qp->ecn = 0;
93 qp->peer = q->net->max_dist ?
94 inet_getpeer_v4(net->ipv4.peers, key->saddr, key->vif, 1) :
95 NULL;
96}
97
98static void ip4_frag_free(struct inet_frag_queue *q)
99{
100 struct ipq *qp;
101
102 qp = container_of(q, struct ipq, q);
103 if (qp->peer)
104 inet_putpeer(qp->peer);
105}
106
107
108/* Destruction primitives. */
109
110static void ipq_put(struct ipq *ipq)
111{
112 inet_frag_put(&ipq->q);
113}
114
115/* Kill ipq entry. It is not destroyed immediately,
116 * because caller (and someone more) holds reference count.
117 */
118static void ipq_kill(struct ipq *ipq)
119{
120 inet_frag_kill(&ipq->q);
121}
122
123static bool frag_expire_skip_icmp(u32 user)
124{
125 return user == IP_DEFRAG_AF_PACKET ||
126 ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_IN,
127 __IP_DEFRAG_CONNTRACK_IN_END) ||
128 ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_BRIDGE_IN,
129 __IP_DEFRAG_CONNTRACK_BRIDGE_IN);
130}
131
132/*
133 * Oops, a fragment queue timed out. Kill it and send an ICMP reply.
134 */
135static void ip_expire(struct timer_list *t)
136{
137 struct inet_frag_queue *frag = from_timer(frag, t, timer);
138 const struct iphdr *iph;
139 struct sk_buff *head;
140 struct net *net;
141 struct ipq *qp;
142 int err;
143
144 qp = container_of(frag, struct ipq, q);
145 net = container_of(qp->q.net, struct net, ipv4.frags);
146
147 rcu_read_lock();
148 spin_lock(&qp->q.lock);
149
150 if (qp->q.flags & INET_FRAG_COMPLETE)
151 goto out;
152
153 ipq_kill(qp);
154 __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
155
156 head = qp->q.fragments;
157
158 __IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT);
159
160 if (!(qp->q.flags & INET_FRAG_FIRST_IN) || !head)
161 goto out;
162
163 head->dev = dev_get_by_index_rcu(net, qp->iif);
164 if (!head->dev)
165 goto out;
166
167
168 /* skb has no dst, perform route lookup again */
169 iph = ip_hdr(head);
170 err = ip_route_input_noref(head, iph->daddr, iph->saddr,
171 iph->tos, head->dev);
172 if (err)
173 goto out;
174
175 /* Only an end host needs to send an ICMP
176 * "Fragment Reassembly Timeout" message, per RFC792.
177 */
178 if (frag_expire_skip_icmp(qp->q.key.v4.user) &&
179 (skb_rtable(head)->rt_type != RTN_LOCAL))
180 goto out;
181
182 skb_get(head);
183 spin_unlock(&qp->q.lock);
184 icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
185 kfree_skb(head);
186 goto out_rcu_unlock;
187
188out:
189 spin_unlock(&qp->q.lock);
190out_rcu_unlock:
191 rcu_read_unlock();
192 ipq_put(qp);
193}
194
195/* Find the correct entry in the "incomplete datagrams" queue for
196 * this IP datagram, and create new one, if nothing is found.
197 */
198static struct ipq *ip_find(struct net *net, struct iphdr *iph,
199 u32 user, int vif)
200{
201 struct frag_v4_compare_key key = {
202 .saddr = iph->saddr,
203 .daddr = iph->daddr,
204 .user = user,
205 .vif = vif,
206 .id = iph->id,
207 .protocol = iph->protocol,
208 };
209 struct inet_frag_queue *q;
210
211 q = inet_frag_find(&net->ipv4.frags, &key);
212 if (!q)
213 return NULL;
214
215 return container_of(q, struct ipq, q);
216}
217
218/* Is the fragment too far ahead to be part of ipq? */
219static int ip_frag_too_far(struct ipq *qp)
220{
221 struct inet_peer *peer = qp->peer;
222 unsigned int max = qp->q.net->max_dist;
223 unsigned int start, end;
224
225 int rc;
226
227 if (!peer || !max)
228 return 0;
229
230 start = qp->rid;
231 end = atomic_inc_return(&peer->rid);
232 qp->rid = end;
233
234 rc = qp->q.fragments && (end - start) > max;
235
236 if (rc) {
237 struct net *net;
238
239 net = container_of(qp->q.net, struct net, ipv4.frags);
240 __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
241 }
242
243 return rc;
244}
245
246static int ip_frag_reinit(struct ipq *qp)
247{
248 struct sk_buff *fp;
249 unsigned int sum_truesize = 0;
250
251 if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
252 refcount_inc(&qp->q.refcnt);
253 return -ETIMEDOUT;
254 }
255
256 fp = qp->q.fragments;
257 do {
258 struct sk_buff *xp = fp->next;
259
260 sum_truesize += fp->truesize;
261 kfree_skb(fp);
262 fp = xp;
263 } while (fp);
264 sub_frag_mem_limit(qp->q.net, sum_truesize);
265
266 qp->q.flags = 0;
267 qp->q.len = 0;
268 qp->q.meat = 0;
269 qp->q.fragments = NULL;
270 qp->q.fragments_tail = NULL;
271 qp->iif = 0;
272 qp->ecn = 0;
273
274 return 0;
275}
276
277/* Add new segment to existing queue. */
278static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
279{
280 struct sk_buff *prev, *next;
281 struct net_device *dev;
282 unsigned int fragsize;
283 int flags, offset;
284 int ihl, end;
285 int err = -ENOENT;
286 u8 ecn;
287
288 if (qp->q.flags & INET_FRAG_COMPLETE)
289 goto err;
290
291 if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
292 unlikely(ip_frag_too_far(qp)) &&
293 unlikely(err = ip_frag_reinit(qp))) {
294 ipq_kill(qp);
295 goto err;
296 }
297
298 ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
299 offset = ntohs(ip_hdr(skb)->frag_off);
300 flags = offset & ~IP_OFFSET;
301 offset &= IP_OFFSET;
302 offset <<= 3; /* offset is in 8-byte chunks */
303 ihl = ip_hdrlen(skb);
304
305 /* Determine the position of this fragment. */
306 end = offset + skb->len - skb_network_offset(skb) - ihl;
307 err = -EINVAL;
308
309 /* Is this the final fragment? */
310 if ((flags & IP_MF) == 0) {
311 /* If we already have some bits beyond end
312 * or have different end, the segment is corrupted.
313 */
314 if (end < qp->q.len ||
315 ((qp->q.flags & INET_FRAG_LAST_IN) && end != qp->q.len))
316 goto err;
317 qp->q.flags |= INET_FRAG_LAST_IN;
318 qp->q.len = end;
319 } else {
320 if (end&7) {
321 end &= ~7;
322 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
323 skb->ip_summed = CHECKSUM_NONE;
324 }
325 if (end > qp->q.len) {
326 /* Some bits beyond end -> corruption. */
327 if (qp->q.flags & INET_FRAG_LAST_IN)
328 goto err;
329 qp->q.len = end;
330 }
331 }
332 if (end == offset)
333 goto err;
334
335 err = -ENOMEM;
336 if (!pskb_pull(skb, skb_network_offset(skb) + ihl))
337 goto err;
338
339 err = pskb_trim_rcsum(skb, end - offset);
340 if (err)
341 goto err;
342
343 /* Find out which fragments are in front and at the back of us
344 * in the chain of fragments so far. We must know where to put
345 * this fragment, right?
346 */
347 prev = qp->q.fragments_tail;
348 if (!prev || prev->ip_defrag_offset < offset) {
349 next = NULL;
350 goto found;
351 }
352 prev = NULL;
353 for (next = qp->q.fragments; next != NULL; next = next->next) {
354 if (next->ip_defrag_offset >= offset)
355 break; /* bingo! */
356 prev = next;
357 }
358
359found:
360 /* We found where to put this one. Check for overlap with
361 * preceding fragment, and, if needed, align things so that
362 * any overlaps are eliminated.
363 */
364 if (prev) {
365 int i = (prev->ip_defrag_offset + prev->len) - offset;
366
367 if (i > 0) {
368 offset += i;
369 err = -EINVAL;
370 if (end <= offset)
371 goto err;
372 err = -ENOMEM;
373 if (!pskb_pull(skb, i))
374 goto err;
375 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
376 skb->ip_summed = CHECKSUM_NONE;
377 }
378 }
379
380 err = -ENOMEM;
381
382 while (next && next->ip_defrag_offset < end) {
383 int i = end - next->ip_defrag_offset; /* overlap is 'i' bytes */
384
385 if (i < next->len) {
386 /* Eat head of the next overlapped fragment
387 * and leave the loop. The next ones cannot overlap.
388 */
389 if (!pskb_pull(next, i))
390 goto err;
391 next->ip_defrag_offset += i;
392 qp->q.meat -= i;
393 if (next->ip_summed != CHECKSUM_UNNECESSARY)
394 next->ip_summed = CHECKSUM_NONE;
395 break;
396 } else {
397 struct sk_buff *free_it = next;
398
399 /* Old fragment is completely overridden with
400 * new one drop it.
401 */
402 next = next->next;
403
404 if (prev)
405 prev->next = next;
406 else
407 qp->q.fragments = next;
408
409 qp->q.meat -= free_it->len;
410 sub_frag_mem_limit(qp->q.net, free_it->truesize);
411 kfree_skb(free_it);
412 }
413 }
414
415 /* Note : skb->ip_defrag_offset and skb->dev share the same location */
416 dev = skb->dev;
417 if (dev)
418 qp->iif = dev->ifindex;
419 /* Makes sure compiler wont do silly aliasing games */
420 barrier();
421 skb->ip_defrag_offset = offset;
422
423 /* Insert this fragment in the chain of fragments. */
424 skb->next = next;
425 if (!next)
426 qp->q.fragments_tail = skb;
427 if (prev)
428 prev->next = skb;
429 else
430 qp->q.fragments = skb;
431
432 qp->q.stamp = skb->tstamp;
433 qp->q.meat += skb->len;
434 qp->ecn |= ecn;
435 add_frag_mem_limit(qp->q.net, skb->truesize);
436 if (offset == 0)
437 qp->q.flags |= INET_FRAG_FIRST_IN;
438
439 fragsize = skb->len + ihl;
440
441 if (fragsize > qp->q.max_size)
442 qp->q.max_size = fragsize;
443
444 if (ip_hdr(skb)->frag_off & htons(IP_DF) &&
445 fragsize > qp->max_df_size)
446 qp->max_df_size = fragsize;
447
448 if (qp->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
449 qp->q.meat == qp->q.len) {
450 unsigned long orefdst = skb->_skb_refdst;
451
452 skb->_skb_refdst = 0UL;
453 err = ip_frag_reasm(qp, prev, dev);
454 skb->_skb_refdst = orefdst;
455 return err;
456 }
457
458 skb_dst_drop(skb);
459 return -EINPROGRESS;
460
461err:
462 kfree_skb(skb);
463 return err;
464}
465
466
467/* Build a new IP datagram from all its fragments. */
468
469static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
470 struct net_device *dev)
471{
472 struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
473 struct iphdr *iph;
474 struct sk_buff *fp, *head = qp->q.fragments;
475 int len;
476 int ihlen;
477 int err;
478 u8 ecn;
479
480 ipq_kill(qp);
481
482 ecn = ip_frag_ecn_table[qp->ecn];
483 if (unlikely(ecn == 0xff)) {
484 err = -EINVAL;
485 goto out_fail;
486 }
487 /* Make the one we just received the head. */
488 if (prev) {
489 head = prev->next;
490 fp = skb_clone(head, GFP_ATOMIC);
491 if (!fp)
492 goto out_nomem;
493
494 fp->next = head->next;
495 if (!fp->next)
496 qp->q.fragments_tail = fp;
497 prev->next = fp;
498
499 skb_morph(head, qp->q.fragments);
500 head->next = qp->q.fragments->next;
501
502 consume_skb(qp->q.fragments);
503 qp->q.fragments = head;
504 }
505
506 WARN_ON(!head);
507 WARN_ON(head->ip_defrag_offset != 0);
508
509 /* Allocate a new buffer for the datagram. */
510 ihlen = ip_hdrlen(head);
511 len = ihlen + qp->q.len;
512
513 err = -E2BIG;
514 if (len > 65535)
515 goto out_oversize;
516
517 /* Head of list must not be cloned. */
518 if (skb_unclone(head, GFP_ATOMIC))
519 goto out_nomem;
520
521 /* If the first fragment is fragmented itself, we split
522 * it to two chunks: the first with data and paged part
523 * and the second, holding only fragments. */
524 if (skb_has_frag_list(head)) {
525 struct sk_buff *clone;
526 int i, plen = 0;
527
528 clone = alloc_skb(0, GFP_ATOMIC);
529 if (!clone)
530 goto out_nomem;
531 clone->next = head->next;
532 head->next = clone;
533 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
534 skb_frag_list_init(head);
535 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
536 plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
537 clone->len = clone->data_len = head->data_len - plen;
538 head->data_len -= clone->len;
539 head->len -= clone->len;
540 clone->csum = 0;
541 clone->ip_summed = head->ip_summed;
542 add_frag_mem_limit(qp->q.net, clone->truesize);
543 }
544
545 skb_shinfo(head)->frag_list = head->next;
546 skb_push(head, head->data - skb_network_header(head));
547
548 for (fp=head->next; fp; fp = fp->next) {
549 head->data_len += fp->len;
550 head->len += fp->len;
551 if (head->ip_summed != fp->ip_summed)
552 head->ip_summed = CHECKSUM_NONE;
553 else if (head->ip_summed == CHECKSUM_COMPLETE)
554 head->csum = csum_add(head->csum, fp->csum);
555 head->truesize += fp->truesize;
556 }
557 sub_frag_mem_limit(qp->q.net, head->truesize);
558
559 head->next = NULL;
560 head->dev = dev;
561 head->tstamp = qp->q.stamp;
562 IPCB(head)->frag_max_size = max(qp->max_df_size, qp->q.max_size);
563
564 iph = ip_hdr(head);
565 iph->tot_len = htons(len);
566 iph->tos |= ecn;
567
568 /* When we set IP_DF on a refragmented skb we must also force a
569 * call to ip_fragment to avoid forwarding a DF-skb of size s while
570 * original sender only sent fragments of size f (where f < s).
571 *
572 * We only set DF/IPSKB_FRAG_PMTU if such DF fragment was the largest
573 * frag seen to avoid sending tiny DF-fragments in case skb was built
574 * from one very small df-fragment and one large non-df frag.
575 */
576 if (qp->max_df_size == qp->q.max_size) {
577 IPCB(head)->flags |= IPSKB_FRAG_PMTU;
578 iph->frag_off = htons(IP_DF);
579 } else {
580 iph->frag_off = 0;
581 }
582
583 ip_send_check(iph);
584
585 __IP_INC_STATS(net, IPSTATS_MIB_REASMOKS);
586 qp->q.fragments = NULL;
587 qp->q.fragments_tail = NULL;
588 return 0;
589
590out_nomem:
591 net_dbg_ratelimited("queue_glue: no memory for gluing queue %p\n", qp);
592 err = -ENOMEM;
593 goto out_fail;
594out_oversize:
595 net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->q.key.v4.saddr);
596out_fail:
597 __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
598 return err;
599}
600
601/* Process an incoming IP datagram fragment. */
602int ip_defrag(struct net *net, struct sk_buff *skb, u32 user)
603{
604 struct net_device *dev = skb->dev ? : skb_dst(skb)->dev;
605 int vif = l3mdev_master_ifindex_rcu(dev);
606 struct ipq *qp;
607
608 __IP_INC_STATS(net, IPSTATS_MIB_REASMREQDS);
609 skb_orphan(skb);
610
611 /* Lookup (or create) queue header */
612 qp = ip_find(net, ip_hdr(skb), user, vif);
613 if (qp) {
614 int ret;
615
616 spin_lock(&qp->q.lock);
617
618 ret = ip_frag_queue(qp, skb);
619
620 spin_unlock(&qp->q.lock);
621 ipq_put(qp);
622 return ret;
623 }
624
625 __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
626 kfree_skb(skb);
627 return -ENOMEM;
628}
629EXPORT_SYMBOL(ip_defrag);
630
631struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user)
632{
633 struct iphdr iph;
634 int netoff;
635 u32 len;
636
637 if (skb->protocol != htons(ETH_P_IP))
638 return skb;
639
640 netoff = skb_network_offset(skb);
641
642 if (skb_copy_bits(skb, netoff, &iph, sizeof(iph)) < 0)
643 return skb;
644
645 if (iph.ihl < 5 || iph.version != 4)
646 return skb;
647
648 len = ntohs(iph.tot_len);
649 if (skb->len < netoff + len || len < (iph.ihl * 4))
650 return skb;
651
652 if (ip_is_fragment(&iph)) {
653 skb = skb_share_check(skb, GFP_ATOMIC);
654 if (skb) {
655 if (!pskb_may_pull(skb, netoff + iph.ihl * 4))
656 return skb;
657 if (pskb_trim_rcsum(skb, netoff + len))
658 return skb;
659 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
660 if (ip_defrag(net, skb, user))
661 return NULL;
662 skb_clear_hash(skb);
663 }
664 }
665 return skb;
666}
667EXPORT_SYMBOL(ip_check_defrag);
668
669#ifdef CONFIG_SYSCTL
670static int dist_min;
671
672static struct ctl_table ip4_frags_ns_ctl_table[] = {
673 {
674 .procname = "ipfrag_high_thresh",
675 .data = &init_net.ipv4.frags.high_thresh,
676 .maxlen = sizeof(unsigned long),
677 .mode = 0644,
678 .proc_handler = proc_doulongvec_minmax,
679 .extra1 = &init_net.ipv4.frags.low_thresh
680 },
681 {
682 .procname = "ipfrag_low_thresh",
683 .data = &init_net.ipv4.frags.low_thresh,
684 .maxlen = sizeof(unsigned long),
685 .mode = 0644,
686 .proc_handler = proc_doulongvec_minmax,
687 .extra2 = &init_net.ipv4.frags.high_thresh
688 },
689 {
690 .procname = "ipfrag_time",
691 .data = &init_net.ipv4.frags.timeout,
692 .maxlen = sizeof(int),
693 .mode = 0644,
694 .proc_handler = proc_dointvec_jiffies,
695 },
696 {
697 .procname = "ipfrag_max_dist",
698 .data = &init_net.ipv4.frags.max_dist,
699 .maxlen = sizeof(int),
700 .mode = 0644,
701 .proc_handler = proc_dointvec_minmax,
702 .extra1 = &dist_min,
703 },
704 { }
705};
706
707/* secret interval has been deprecated */
708static int ip4_frags_secret_interval_unused;
709static struct ctl_table ip4_frags_ctl_table[] = {
710 {
711 .procname = "ipfrag_secret_interval",
712 .data = &ip4_frags_secret_interval_unused,
713 .maxlen = sizeof(int),
714 .mode = 0644,
715 .proc_handler = proc_dointvec_jiffies,
716 },
717 { }
718};
719
720static int __net_init ip4_frags_ns_ctl_register(struct net *net)
721{
722 struct ctl_table *table;
723 struct ctl_table_header *hdr;
724
725 table = ip4_frags_ns_ctl_table;
726 if (!net_eq(net, &init_net)) {
727 table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
728 if (!table)
729 goto err_alloc;
730
731 table[0].data = &net->ipv4.frags.high_thresh;
732 table[0].extra1 = &net->ipv4.frags.low_thresh;
733 table[0].extra2 = &init_net.ipv4.frags.high_thresh;
734 table[1].data = &net->ipv4.frags.low_thresh;
735 table[1].extra2 = &net->ipv4.frags.high_thresh;
736 table[2].data = &net->ipv4.frags.timeout;
737 table[3].data = &net->ipv4.frags.max_dist;
738 }
739
740 hdr = register_net_sysctl(net, "net/ipv4", table);
741 if (!hdr)
742 goto err_reg;
743
744 net->ipv4.frags_hdr = hdr;
745 return 0;
746
747err_reg:
748 if (!net_eq(net, &init_net))
749 kfree(table);
750err_alloc:
751 return -ENOMEM;
752}
753
754static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
755{
756 struct ctl_table *table;
757
758 table = net->ipv4.frags_hdr->ctl_table_arg;
759 unregister_net_sysctl_table(net->ipv4.frags_hdr);
760 kfree(table);
761}
762
763static void __init ip4_frags_ctl_register(void)
764{
765 register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
766}
767#else
768static int ip4_frags_ns_ctl_register(struct net *net)
769{
770 return 0;
771}
772
773static void ip4_frags_ns_ctl_unregister(struct net *net)
774{
775}
776
777static void __init ip4_frags_ctl_register(void)
778{
779}
780#endif
781
782static int __net_init ipv4_frags_init_net(struct net *net)
783{
784 int res;
785
786 /* Fragment cache limits.
787 *
788 * The fragment memory accounting code, (tries to) account for
789 * the real memory usage, by measuring both the size of frag
790 * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue))
791 * and the SKB's truesize.
792 *
793 * A 64K fragment consumes 129736 bytes (44*2944)+200
794 * (1500 truesize == 2944, sizeof(struct ipq) == 200)
795 *
796 * We will commit 4MB at one time. Should we cross that limit
797 * we will prune down to 3MB, making room for approx 8 big 64K
798 * fragments 8x128k.
799 */
800 net->ipv4.frags.high_thresh = 4 * 1024 * 1024;
801 net->ipv4.frags.low_thresh = 3 * 1024 * 1024;
802 /*
803 * Important NOTE! Fragment queue must be destroyed before MSL expires.
804 * RFC791 is wrong proposing to prolongate timer each fragment arrival
805 * by TTL.
806 */
807 net->ipv4.frags.timeout = IP_FRAG_TIME;
808
809 net->ipv4.frags.max_dist = 64;
810 net->ipv4.frags.f = &ip4_frags;
811
812 res = inet_frags_init_net(&net->ipv4.frags);
813 if (res < 0)
814 return res;
815 res = ip4_frags_ns_ctl_register(net);
816 if (res < 0)
817 inet_frags_exit_net(&net->ipv4.frags);
818 return res;
819}
820
821static void __net_exit ipv4_frags_exit_net(struct net *net)
822{
823 ip4_frags_ns_ctl_unregister(net);
824 inet_frags_exit_net(&net->ipv4.frags);
825}
826
827static struct pernet_operations ip4_frags_ops = {
828 .init = ipv4_frags_init_net,
829 .exit = ipv4_frags_exit_net,
830};
831
832
833static u32 ip4_key_hashfn(const void *data, u32 len, u32 seed)
834{
835 return jhash2(data,
836 sizeof(struct frag_v4_compare_key) / sizeof(u32), seed);
837}
838
839static u32 ip4_obj_hashfn(const void *data, u32 len, u32 seed)
840{
841 const struct inet_frag_queue *fq = data;
842
843 return jhash2((const u32 *)&fq->key.v4,
844 sizeof(struct frag_v4_compare_key) / sizeof(u32), seed);
845}
846
847static int ip4_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr)
848{
849 const struct frag_v4_compare_key *key = arg->key;
850 const struct inet_frag_queue *fq = ptr;
851
852 return !!memcmp(&fq->key, key, sizeof(*key));
853}
854
855static const struct rhashtable_params ip4_rhash_params = {
856 .head_offset = offsetof(struct inet_frag_queue, node),
857 .key_offset = offsetof(struct inet_frag_queue, key),
858 .key_len = sizeof(struct frag_v4_compare_key),
859 .hashfn = ip4_key_hashfn,
860 .obj_hashfn = ip4_obj_hashfn,
861 .obj_cmpfn = ip4_obj_cmpfn,
862 .automatic_shrinking = true,
863};
864
865void __init ipfrag_init(void)
866{
867 ip4_frags.constructor = ip4_frag_init;
868 ip4_frags.destructor = ip4_frag_free;
869 ip4_frags.qsize = sizeof(struct ipq);
870 ip4_frags.frag_expire = ip_expire;
871 ip4_frags.frags_cache_name = ip_frag_cache_name;
872 ip4_frags.rhash_params = ip4_rhash_params;
873 if (inet_frags_init(&ip4_frags))
874 panic("IP: failed to allocate ip4_frags cache\n");
875 ip4_frags_ctl_register();
876 register_pernet_subsys(&ip4_frags_ops);
877}
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#define pr_fmt(fmt) "IPv4: " fmt
24
25#include <linux/compiler.h>
26#include <linux/module.h>
27#include <linux/types.h>
28#include <linux/mm.h>
29#include <linux/jiffies.h>
30#include <linux/skbuff.h>
31#include <linux/list.h>
32#include <linux/ip.h>
33#include <linux/icmp.h>
34#include <linux/netdevice.h>
35#include <linux/jhash.h>
36#include <linux/random.h>
37#include <linux/slab.h>
38#include <net/route.h>
39#include <net/dst.h>
40#include <net/sock.h>
41#include <net/ip.h>
42#include <net/icmp.h>
43#include <net/checksum.h>
44#include <net/inetpeer.h>
45#include <net/inet_frag.h>
46#include <linux/tcp.h>
47#include <linux/udp.h>
48#include <linux/inet.h>
49#include <linux/netfilter_ipv4.h>
50#include <net/inet_ecn.h>
51#include <net/l3mdev.h>
52
53/* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
54 * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
55 * as well. Or notify me, at least. --ANK
56 */
57static const char ip_frag_cache_name[] = "ip4-frags";
58
59struct ipfrag_skb_cb
60{
61 struct inet_skb_parm h;
62 int offset;
63};
64
65#define FRAG_CB(skb) ((struct ipfrag_skb_cb *)((skb)->cb))
66
67/* Describe an entry in the "incomplete datagrams" queue. */
68struct ipq {
69 struct inet_frag_queue q;
70
71 u32 user;
72 __be32 saddr;
73 __be32 daddr;
74 __be16 id;
75 u8 protocol;
76 u8 ecn; /* RFC3168 support */
77 u16 max_df_size; /* largest frag with DF set seen */
78 int iif;
79 int vif; /* L3 master device index */
80 unsigned int rid;
81 struct inet_peer *peer;
82};
83
84static u8 ip4_frag_ecn(u8 tos)
85{
86 return 1 << (tos & INET_ECN_MASK);
87}
88
89static struct inet_frags ip4_frags;
90
91int ip_frag_mem(struct net *net)
92{
93 return sum_frag_mem_limit(&net->ipv4.frags);
94}
95
96static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
97 struct net_device *dev);
98
99struct ip4_create_arg {
100 struct iphdr *iph;
101 u32 user;
102 int vif;
103};
104
105static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
106{
107 net_get_random_once(&ip4_frags.rnd, sizeof(ip4_frags.rnd));
108 return jhash_3words((__force u32)id << 16 | prot,
109 (__force u32)saddr, (__force u32)daddr,
110 ip4_frags.rnd);
111}
112
113static unsigned int ip4_hashfn(const struct inet_frag_queue *q)
114{
115 const struct ipq *ipq;
116
117 ipq = container_of(q, struct ipq, q);
118 return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);
119}
120
121static bool ip4_frag_match(const struct inet_frag_queue *q, const void *a)
122{
123 const struct ipq *qp;
124 const struct ip4_create_arg *arg = a;
125
126 qp = container_of(q, struct ipq, q);
127 return qp->id == arg->iph->id &&
128 qp->saddr == arg->iph->saddr &&
129 qp->daddr == arg->iph->daddr &&
130 qp->protocol == arg->iph->protocol &&
131 qp->user == arg->user &&
132 qp->vif == arg->vif;
133}
134
135static void ip4_frag_init(struct inet_frag_queue *q, const void *a)
136{
137 struct ipq *qp = container_of(q, struct ipq, q);
138 struct netns_ipv4 *ipv4 = container_of(q->net, struct netns_ipv4,
139 frags);
140 struct net *net = container_of(ipv4, struct net, ipv4);
141
142 const struct ip4_create_arg *arg = a;
143
144 qp->protocol = arg->iph->protocol;
145 qp->id = arg->iph->id;
146 qp->ecn = ip4_frag_ecn(arg->iph->tos);
147 qp->saddr = arg->iph->saddr;
148 qp->daddr = arg->iph->daddr;
149 qp->vif = arg->vif;
150 qp->user = arg->user;
151 qp->peer = q->net->max_dist ?
152 inet_getpeer_v4(net->ipv4.peers, arg->iph->saddr, arg->vif, 1) :
153 NULL;
154}
155
156static void ip4_frag_free(struct inet_frag_queue *q)
157{
158 struct ipq *qp;
159
160 qp = container_of(q, struct ipq, q);
161 if (qp->peer)
162 inet_putpeer(qp->peer);
163}
164
165
166/* Destruction primitives. */
167
168static void ipq_put(struct ipq *ipq)
169{
170 inet_frag_put(&ipq->q, &ip4_frags);
171}
172
173/* Kill ipq entry. It is not destroyed immediately,
174 * because caller (and someone more) holds reference count.
175 */
176static void ipq_kill(struct ipq *ipq)
177{
178 inet_frag_kill(&ipq->q, &ip4_frags);
179}
180
181static bool frag_expire_skip_icmp(u32 user)
182{
183 return user == IP_DEFRAG_AF_PACKET ||
184 ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_IN,
185 __IP_DEFRAG_CONNTRACK_IN_END) ||
186 ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_BRIDGE_IN,
187 __IP_DEFRAG_CONNTRACK_BRIDGE_IN);
188}
189
190/*
191 * Oops, a fragment queue timed out. Kill it and send an ICMP reply.
192 */
193static void ip_expire(unsigned long arg)
194{
195 struct ipq *qp;
196 struct net *net;
197
198 qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);
199 net = container_of(qp->q.net, struct net, ipv4.frags);
200
201 spin_lock(&qp->q.lock);
202
203 if (qp->q.flags & INET_FRAG_COMPLETE)
204 goto out;
205
206 ipq_kill(qp);
207 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
208
209 if (!inet_frag_evicting(&qp->q)) {
210 struct sk_buff *head = qp->q.fragments;
211 const struct iphdr *iph;
212 int err;
213
214 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMTIMEOUT);
215
216 if (!(qp->q.flags & INET_FRAG_FIRST_IN) || !qp->q.fragments)
217 goto out;
218
219 rcu_read_lock();
220 head->dev = dev_get_by_index_rcu(net, qp->iif);
221 if (!head->dev)
222 goto out_rcu_unlock;
223
224 /* skb has no dst, perform route lookup again */
225 iph = ip_hdr(head);
226 err = ip_route_input_noref(head, iph->daddr, iph->saddr,
227 iph->tos, head->dev);
228 if (err)
229 goto out_rcu_unlock;
230
231 /* Only an end host needs to send an ICMP
232 * "Fragment Reassembly Timeout" message, per RFC792.
233 */
234 if (frag_expire_skip_icmp(qp->user) &&
235 (skb_rtable(head)->rt_type != RTN_LOCAL))
236 goto out_rcu_unlock;
237
238 /* Send an ICMP "Fragment Reassembly Timeout" message. */
239 icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
240out_rcu_unlock:
241 rcu_read_unlock();
242 }
243out:
244 spin_unlock(&qp->q.lock);
245 ipq_put(qp);
246}
247
248/* Find the correct entry in the "incomplete datagrams" queue for
249 * this IP datagram, and create new one, if nothing is found.
250 */
251static struct ipq *ip_find(struct net *net, struct iphdr *iph,
252 u32 user, int vif)
253{
254 struct inet_frag_queue *q;
255 struct ip4_create_arg arg;
256 unsigned int hash;
257
258 arg.iph = iph;
259 arg.user = user;
260 arg.vif = vif;
261
262 hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
263
264 q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);
265 if (IS_ERR_OR_NULL(q)) {
266 inet_frag_maybe_warn_overflow(q, pr_fmt());
267 return NULL;
268 }
269 return container_of(q, struct ipq, q);
270}
271
272/* Is the fragment too far ahead to be part of ipq? */
273static int ip_frag_too_far(struct ipq *qp)
274{
275 struct inet_peer *peer = qp->peer;
276 unsigned int max = qp->q.net->max_dist;
277 unsigned int start, end;
278
279 int rc;
280
281 if (!peer || !max)
282 return 0;
283
284 start = qp->rid;
285 end = atomic_inc_return(&peer->rid);
286 qp->rid = end;
287
288 rc = qp->q.fragments && (end - start) > max;
289
290 if (rc) {
291 struct net *net;
292
293 net = container_of(qp->q.net, struct net, ipv4.frags);
294 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
295 }
296
297 return rc;
298}
299
300static int ip_frag_reinit(struct ipq *qp)
301{
302 struct sk_buff *fp;
303 unsigned int sum_truesize = 0;
304
305 if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
306 atomic_inc(&qp->q.refcnt);
307 return -ETIMEDOUT;
308 }
309
310 fp = qp->q.fragments;
311 do {
312 struct sk_buff *xp = fp->next;
313
314 sum_truesize += fp->truesize;
315 kfree_skb(fp);
316 fp = xp;
317 } while (fp);
318 sub_frag_mem_limit(qp->q.net, sum_truesize);
319
320 qp->q.flags = 0;
321 qp->q.len = 0;
322 qp->q.meat = 0;
323 qp->q.fragments = NULL;
324 qp->q.fragments_tail = NULL;
325 qp->iif = 0;
326 qp->ecn = 0;
327
328 return 0;
329}
330
331/* Add new segment to existing queue. */
332static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
333{
334 struct sk_buff *prev, *next;
335 struct net_device *dev;
336 unsigned int fragsize;
337 int flags, offset;
338 int ihl, end;
339 int err = -ENOENT;
340 u8 ecn;
341
342 if (qp->q.flags & INET_FRAG_COMPLETE)
343 goto err;
344
345 if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
346 unlikely(ip_frag_too_far(qp)) &&
347 unlikely(err = ip_frag_reinit(qp))) {
348 ipq_kill(qp);
349 goto err;
350 }
351
352 ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
353 offset = ntohs(ip_hdr(skb)->frag_off);
354 flags = offset & ~IP_OFFSET;
355 offset &= IP_OFFSET;
356 offset <<= 3; /* offset is in 8-byte chunks */
357 ihl = ip_hdrlen(skb);
358
359 /* Determine the position of this fragment. */
360 end = offset + skb->len - skb_network_offset(skb) - ihl;
361 err = -EINVAL;
362
363 /* Is this the final fragment? */
364 if ((flags & IP_MF) == 0) {
365 /* If we already have some bits beyond end
366 * or have different end, the segment is corrupted.
367 */
368 if (end < qp->q.len ||
369 ((qp->q.flags & INET_FRAG_LAST_IN) && end != qp->q.len))
370 goto err;
371 qp->q.flags |= INET_FRAG_LAST_IN;
372 qp->q.len = end;
373 } else {
374 if (end&7) {
375 end &= ~7;
376 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
377 skb->ip_summed = CHECKSUM_NONE;
378 }
379 if (end > qp->q.len) {
380 /* Some bits beyond end -> corruption. */
381 if (qp->q.flags & INET_FRAG_LAST_IN)
382 goto err;
383 qp->q.len = end;
384 }
385 }
386 if (end == offset)
387 goto err;
388
389 err = -ENOMEM;
390 if (!pskb_pull(skb, skb_network_offset(skb) + ihl))
391 goto err;
392
393 err = pskb_trim_rcsum(skb, end - offset);
394 if (err)
395 goto err;
396
397 /* Find out which fragments are in front and at the back of us
398 * in the chain of fragments so far. We must know where to put
399 * this fragment, right?
400 */
401 prev = qp->q.fragments_tail;
402 if (!prev || FRAG_CB(prev)->offset < offset) {
403 next = NULL;
404 goto found;
405 }
406 prev = NULL;
407 for (next = qp->q.fragments; next != NULL; next = next->next) {
408 if (FRAG_CB(next)->offset >= offset)
409 break; /* bingo! */
410 prev = next;
411 }
412
413found:
414 /* We found where to put this one. Check for overlap with
415 * preceding fragment, and, if needed, align things so that
416 * any overlaps are eliminated.
417 */
418 if (prev) {
419 int i = (FRAG_CB(prev)->offset + prev->len) - offset;
420
421 if (i > 0) {
422 offset += i;
423 err = -EINVAL;
424 if (end <= offset)
425 goto err;
426 err = -ENOMEM;
427 if (!pskb_pull(skb, i))
428 goto err;
429 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
430 skb->ip_summed = CHECKSUM_NONE;
431 }
432 }
433
434 err = -ENOMEM;
435
436 while (next && FRAG_CB(next)->offset < end) {
437 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
438
439 if (i < next->len) {
440 /* Eat head of the next overlapped fragment
441 * and leave the loop. The next ones cannot overlap.
442 */
443 if (!pskb_pull(next, i))
444 goto err;
445 FRAG_CB(next)->offset += i;
446 qp->q.meat -= i;
447 if (next->ip_summed != CHECKSUM_UNNECESSARY)
448 next->ip_summed = CHECKSUM_NONE;
449 break;
450 } else {
451 struct sk_buff *free_it = next;
452
453 /* Old fragment is completely overridden with
454 * new one drop it.
455 */
456 next = next->next;
457
458 if (prev)
459 prev->next = next;
460 else
461 qp->q.fragments = next;
462
463 qp->q.meat -= free_it->len;
464 sub_frag_mem_limit(qp->q.net, free_it->truesize);
465 kfree_skb(free_it);
466 }
467 }
468
469 FRAG_CB(skb)->offset = offset;
470
471 /* Insert this fragment in the chain of fragments. */
472 skb->next = next;
473 if (!next)
474 qp->q.fragments_tail = skb;
475 if (prev)
476 prev->next = skb;
477 else
478 qp->q.fragments = skb;
479
480 dev = skb->dev;
481 if (dev) {
482 qp->iif = dev->ifindex;
483 skb->dev = NULL;
484 }
485 qp->q.stamp = skb->tstamp;
486 qp->q.meat += skb->len;
487 qp->ecn |= ecn;
488 add_frag_mem_limit(qp->q.net, skb->truesize);
489 if (offset == 0)
490 qp->q.flags |= INET_FRAG_FIRST_IN;
491
492 fragsize = skb->len + ihl;
493
494 if (fragsize > qp->q.max_size)
495 qp->q.max_size = fragsize;
496
497 if (ip_hdr(skb)->frag_off & htons(IP_DF) &&
498 fragsize > qp->max_df_size)
499 qp->max_df_size = fragsize;
500
501 if (qp->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
502 qp->q.meat == qp->q.len) {
503 unsigned long orefdst = skb->_skb_refdst;
504
505 skb->_skb_refdst = 0UL;
506 err = ip_frag_reasm(qp, prev, dev);
507 skb->_skb_refdst = orefdst;
508 return err;
509 }
510
511 skb_dst_drop(skb);
512 return -EINPROGRESS;
513
514err:
515 kfree_skb(skb);
516 return err;
517}
518
519
520/* Build a new IP datagram from all its fragments. */
521
522static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
523 struct net_device *dev)
524{
525 struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
526 struct iphdr *iph;
527 struct sk_buff *fp, *head = qp->q.fragments;
528 int len;
529 int ihlen;
530 int err;
531 u8 ecn;
532
533 ipq_kill(qp);
534
535 ecn = ip_frag_ecn_table[qp->ecn];
536 if (unlikely(ecn == 0xff)) {
537 err = -EINVAL;
538 goto out_fail;
539 }
540 /* Make the one we just received the head. */
541 if (prev) {
542 head = prev->next;
543 fp = skb_clone(head, GFP_ATOMIC);
544 if (!fp)
545 goto out_nomem;
546
547 fp->next = head->next;
548 if (!fp->next)
549 qp->q.fragments_tail = fp;
550 prev->next = fp;
551
552 skb_morph(head, qp->q.fragments);
553 head->next = qp->q.fragments->next;
554
555 consume_skb(qp->q.fragments);
556 qp->q.fragments = head;
557 }
558
559 WARN_ON(!head);
560 WARN_ON(FRAG_CB(head)->offset != 0);
561
562 /* Allocate a new buffer for the datagram. */
563 ihlen = ip_hdrlen(head);
564 len = ihlen + qp->q.len;
565
566 err = -E2BIG;
567 if (len > 65535)
568 goto out_oversize;
569
570 /* Head of list must not be cloned. */
571 if (skb_unclone(head, GFP_ATOMIC))
572 goto out_nomem;
573
574 /* If the first fragment is fragmented itself, we split
575 * it to two chunks: the first with data and paged part
576 * and the second, holding only fragments. */
577 if (skb_has_frag_list(head)) {
578 struct sk_buff *clone;
579 int i, plen = 0;
580
581 clone = alloc_skb(0, GFP_ATOMIC);
582 if (!clone)
583 goto out_nomem;
584 clone->next = head->next;
585 head->next = clone;
586 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
587 skb_frag_list_init(head);
588 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
589 plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
590 clone->len = clone->data_len = head->data_len - plen;
591 head->data_len -= clone->len;
592 head->len -= clone->len;
593 clone->csum = 0;
594 clone->ip_summed = head->ip_summed;
595 add_frag_mem_limit(qp->q.net, clone->truesize);
596 }
597
598 skb_shinfo(head)->frag_list = head->next;
599 skb_push(head, head->data - skb_network_header(head));
600
601 for (fp=head->next; fp; fp = fp->next) {
602 head->data_len += fp->len;
603 head->len += fp->len;
604 if (head->ip_summed != fp->ip_summed)
605 head->ip_summed = CHECKSUM_NONE;
606 else if (head->ip_summed == CHECKSUM_COMPLETE)
607 head->csum = csum_add(head->csum, fp->csum);
608 head->truesize += fp->truesize;
609 }
610 sub_frag_mem_limit(qp->q.net, head->truesize);
611
612 head->next = NULL;
613 head->dev = dev;
614 head->tstamp = qp->q.stamp;
615 IPCB(head)->frag_max_size = max(qp->max_df_size, qp->q.max_size);
616
617 iph = ip_hdr(head);
618 iph->tot_len = htons(len);
619 iph->tos |= ecn;
620
621 /* When we set IP_DF on a refragmented skb we must also force a
622 * call to ip_fragment to avoid forwarding a DF-skb of size s while
623 * original sender only sent fragments of size f (where f < s).
624 *
625 * We only set DF/IPSKB_FRAG_PMTU if such DF fragment was the largest
626 * frag seen to avoid sending tiny DF-fragments in case skb was built
627 * from one very small df-fragment and one large non-df frag.
628 */
629 if (qp->max_df_size == qp->q.max_size) {
630 IPCB(head)->flags |= IPSKB_FRAG_PMTU;
631 iph->frag_off = htons(IP_DF);
632 } else {
633 iph->frag_off = 0;
634 }
635
636 ip_send_check(iph);
637
638 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS);
639 qp->q.fragments = NULL;
640 qp->q.fragments_tail = NULL;
641 return 0;
642
643out_nomem:
644 net_dbg_ratelimited("queue_glue: no memory for gluing queue %p\n", qp);
645 err = -ENOMEM;
646 goto out_fail;
647out_oversize:
648 net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->saddr);
649out_fail:
650 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
651 return err;
652}
653
654/* Process an incoming IP datagram fragment. */
655int ip_defrag(struct net *net, struct sk_buff *skb, u32 user)
656{
657 struct net_device *dev = skb->dev ? : skb_dst(skb)->dev;
658 int vif = l3mdev_master_ifindex_rcu(dev);
659 struct ipq *qp;
660
661 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMREQDS);
662 skb_orphan(skb);
663
664 /* Lookup (or create) queue header */
665 qp = ip_find(net, ip_hdr(skb), user, vif);
666 if (qp) {
667 int ret;
668
669 spin_lock(&qp->q.lock);
670
671 ret = ip_frag_queue(qp, skb);
672
673 spin_unlock(&qp->q.lock);
674 ipq_put(qp);
675 return ret;
676 }
677
678 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
679 kfree_skb(skb);
680 return -ENOMEM;
681}
682EXPORT_SYMBOL(ip_defrag);
683
684struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user)
685{
686 struct iphdr iph;
687 int netoff;
688 u32 len;
689
690 if (skb->protocol != htons(ETH_P_IP))
691 return skb;
692
693 netoff = skb_network_offset(skb);
694
695 if (skb_copy_bits(skb, netoff, &iph, sizeof(iph)) < 0)
696 return skb;
697
698 if (iph.ihl < 5 || iph.version != 4)
699 return skb;
700
701 len = ntohs(iph.tot_len);
702 if (skb->len < netoff + len || len < (iph.ihl * 4))
703 return skb;
704
705 if (ip_is_fragment(&iph)) {
706 skb = skb_share_check(skb, GFP_ATOMIC);
707 if (skb) {
708 if (!pskb_may_pull(skb, netoff + iph.ihl * 4))
709 return skb;
710 if (pskb_trim_rcsum(skb, netoff + len))
711 return skb;
712 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
713 if (ip_defrag(net, skb, user))
714 return NULL;
715 skb_clear_hash(skb);
716 }
717 }
718 return skb;
719}
720EXPORT_SYMBOL(ip_check_defrag);
721
722#ifdef CONFIG_SYSCTL
723static int zero;
724
725static struct ctl_table ip4_frags_ns_ctl_table[] = {
726 {
727 .procname = "ipfrag_high_thresh",
728 .data = &init_net.ipv4.frags.high_thresh,
729 .maxlen = sizeof(int),
730 .mode = 0644,
731 .proc_handler = proc_dointvec_minmax,
732 .extra1 = &init_net.ipv4.frags.low_thresh
733 },
734 {
735 .procname = "ipfrag_low_thresh",
736 .data = &init_net.ipv4.frags.low_thresh,
737 .maxlen = sizeof(int),
738 .mode = 0644,
739 .proc_handler = proc_dointvec_minmax,
740 .extra1 = &zero,
741 .extra2 = &init_net.ipv4.frags.high_thresh
742 },
743 {
744 .procname = "ipfrag_time",
745 .data = &init_net.ipv4.frags.timeout,
746 .maxlen = sizeof(int),
747 .mode = 0644,
748 .proc_handler = proc_dointvec_jiffies,
749 },
750 {
751 .procname = "ipfrag_max_dist",
752 .data = &init_net.ipv4.frags.max_dist,
753 .maxlen = sizeof(int),
754 .mode = 0644,
755 .proc_handler = proc_dointvec_minmax,
756 .extra1 = &zero
757 },
758 { }
759};
760
761/* secret interval has been deprecated */
762static int ip4_frags_secret_interval_unused;
763static struct ctl_table ip4_frags_ctl_table[] = {
764 {
765 .procname = "ipfrag_secret_interval",
766 .data = &ip4_frags_secret_interval_unused,
767 .maxlen = sizeof(int),
768 .mode = 0644,
769 .proc_handler = proc_dointvec_jiffies,
770 },
771 { }
772};
773
774static int __net_init ip4_frags_ns_ctl_register(struct net *net)
775{
776 struct ctl_table *table;
777 struct ctl_table_header *hdr;
778
779 table = ip4_frags_ns_ctl_table;
780 if (!net_eq(net, &init_net)) {
781 table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
782 if (!table)
783 goto err_alloc;
784
785 table[0].data = &net->ipv4.frags.high_thresh;
786 table[0].extra1 = &net->ipv4.frags.low_thresh;
787 table[0].extra2 = &init_net.ipv4.frags.high_thresh;
788 table[1].data = &net->ipv4.frags.low_thresh;
789 table[1].extra2 = &net->ipv4.frags.high_thresh;
790 table[2].data = &net->ipv4.frags.timeout;
791 table[3].data = &net->ipv4.frags.max_dist;
792 }
793
794 hdr = register_net_sysctl(net, "net/ipv4", table);
795 if (!hdr)
796 goto err_reg;
797
798 net->ipv4.frags_hdr = hdr;
799 return 0;
800
801err_reg:
802 if (!net_eq(net, &init_net))
803 kfree(table);
804err_alloc:
805 return -ENOMEM;
806}
807
808static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
809{
810 struct ctl_table *table;
811
812 table = net->ipv4.frags_hdr->ctl_table_arg;
813 unregister_net_sysctl_table(net->ipv4.frags_hdr);
814 kfree(table);
815}
816
817static void __init ip4_frags_ctl_register(void)
818{
819 register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
820}
821#else
822static int ip4_frags_ns_ctl_register(struct net *net)
823{
824 return 0;
825}
826
827static void ip4_frags_ns_ctl_unregister(struct net *net)
828{
829}
830
831static void __init ip4_frags_ctl_register(void)
832{
833}
834#endif
835
836static int __net_init ipv4_frags_init_net(struct net *net)
837{
838 int res;
839
840 /* Fragment cache limits.
841 *
842 * The fragment memory accounting code, (tries to) account for
843 * the real memory usage, by measuring both the size of frag
844 * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue))
845 * and the SKB's truesize.
846 *
847 * A 64K fragment consumes 129736 bytes (44*2944)+200
848 * (1500 truesize == 2944, sizeof(struct ipq) == 200)
849 *
850 * We will commit 4MB at one time. Should we cross that limit
851 * we will prune down to 3MB, making room for approx 8 big 64K
852 * fragments 8x128k.
853 */
854 net->ipv4.frags.high_thresh = 4 * 1024 * 1024;
855 net->ipv4.frags.low_thresh = 3 * 1024 * 1024;
856 /*
857 * Important NOTE! Fragment queue must be destroyed before MSL expires.
858 * RFC791 is wrong proposing to prolongate timer each fragment arrival
859 * by TTL.
860 */
861 net->ipv4.frags.timeout = IP_FRAG_TIME;
862
863 net->ipv4.frags.max_dist = 64;
864
865 res = inet_frags_init_net(&net->ipv4.frags);
866 if (res)
867 return res;
868 res = ip4_frags_ns_ctl_register(net);
869 if (res)
870 inet_frags_uninit_net(&net->ipv4.frags);
871 return res;
872}
873
874static void __net_exit ipv4_frags_exit_net(struct net *net)
875{
876 ip4_frags_ns_ctl_unregister(net);
877 inet_frags_exit_net(&net->ipv4.frags, &ip4_frags);
878}
879
880static struct pernet_operations ip4_frags_ops = {
881 .init = ipv4_frags_init_net,
882 .exit = ipv4_frags_exit_net,
883};
884
885void __init ipfrag_init(void)
886{
887 ip4_frags_ctl_register();
888 register_pernet_subsys(&ip4_frags_ops);
889 ip4_frags.hashfn = ip4_hashfn;
890 ip4_frags.constructor = ip4_frag_init;
891 ip4_frags.destructor = ip4_frag_free;
892 ip4_frags.qsize = sizeof(struct ipq);
893 ip4_frags.match = ip4_frag_match;
894 ip4_frags.frag_expire = ip_expire;
895 ip4_frags.frags_cache_name = ip_frag_cache_name;
896 if (inet_frags_init(&ip4_frags))
897 panic("IP: failed to allocate ip4_frags cache\n");
898}