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1/*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * The 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
52/* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
53 * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
54 * as well. Or notify me, at least. --ANK
55 */
56
57static int sysctl_ipfrag_max_dist __read_mostly = 64;
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 int iif;
78 unsigned int rid;
79 struct inet_peer *peer;
80};
81
82static inline u8 ip4_frag_ecn(u8 tos)
83{
84 return 1 << (tos & INET_ECN_MASK);
85}
86
87static struct inet_frags ip4_frags;
88
89int ip_frag_nqueues(struct net *net)
90{
91 return net->ipv4.frags.nqueues;
92}
93
94int ip_frag_mem(struct net *net)
95{
96 return sum_frag_mem_limit(&net->ipv4.frags);
97}
98
99static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
100 struct net_device *dev);
101
102struct ip4_create_arg {
103 struct iphdr *iph;
104 u32 user;
105};
106
107static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
108{
109 net_get_random_once(&ip4_frags.rnd, sizeof(ip4_frags.rnd));
110 return jhash_3words((__force u32)id << 16 | prot,
111 (__force u32)saddr, (__force u32)daddr,
112 ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1);
113}
114
115static unsigned int ip4_hashfn(struct inet_frag_queue *q)
116{
117 struct ipq *ipq;
118
119 ipq = container_of(q, struct ipq, q);
120 return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);
121}
122
123static bool ip4_frag_match(struct inet_frag_queue *q, void *a)
124{
125 struct ipq *qp;
126 struct ip4_create_arg *arg = a;
127
128 qp = container_of(q, struct ipq, q);
129 return qp->id == arg->iph->id &&
130 qp->saddr == arg->iph->saddr &&
131 qp->daddr == arg->iph->daddr &&
132 qp->protocol == arg->iph->protocol &&
133 qp->user == arg->user;
134}
135
136static void ip4_frag_init(struct inet_frag_queue *q, void *a)
137{
138 struct ipq *qp = container_of(q, struct ipq, q);
139 struct netns_ipv4 *ipv4 = container_of(q->net, struct netns_ipv4,
140 frags);
141 struct net *net = container_of(ipv4, struct net, ipv4);
142
143 struct ip4_create_arg *arg = a;
144
145 qp->protocol = arg->iph->protocol;
146 qp->id = arg->iph->id;
147 qp->ecn = ip4_frag_ecn(arg->iph->tos);
148 qp->saddr = arg->iph->saddr;
149 qp->daddr = arg->iph->daddr;
150 qp->user = arg->user;
151 qp->peer = sysctl_ipfrag_max_dist ?
152 inet_getpeer_v4(net->ipv4.peers, arg->iph->saddr, 1) : NULL;
153}
154
155static __inline__ void ip4_frag_free(struct inet_frag_queue *q)
156{
157 struct ipq *qp;
158
159 qp = container_of(q, struct ipq, q);
160 if (qp->peer)
161 inet_putpeer(qp->peer);
162}
163
164
165/* Destruction primitives. */
166
167static __inline__ void ipq_put(struct ipq *ipq)
168{
169 inet_frag_put(&ipq->q, &ip4_frags);
170}
171
172/* Kill ipq entry. It is not destroyed immediately,
173 * because caller (and someone more) holds reference count.
174 */
175static void ipq_kill(struct ipq *ipq)
176{
177 inet_frag_kill(&ipq->q, &ip4_frags);
178}
179
180/* Memory limiting on fragments. Evictor trashes the oldest
181 * fragment queue until we are back under the threshold.
182 */
183static void ip_evictor(struct net *net)
184{
185 int evicted;
186
187 evicted = inet_frag_evictor(&net->ipv4.frags, &ip4_frags, false);
188 if (evicted)
189 IP_ADD_STATS_BH(net, IPSTATS_MIB_REASMFAILS, evicted);
190}
191
192/*
193 * Oops, a fragment queue timed out. Kill it and send an ICMP reply.
194 */
195static void ip_expire(unsigned long arg)
196{
197 struct ipq *qp;
198 struct net *net;
199
200 qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);
201 net = container_of(qp->q.net, struct net, ipv4.frags);
202
203 spin_lock(&qp->q.lock);
204
205 if (qp->q.last_in & INET_FRAG_COMPLETE)
206 goto out;
207
208 ipq_kill(qp);
209
210 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMTIMEOUT);
211 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
212
213 if ((qp->q.last_in & INET_FRAG_FIRST_IN) && qp->q.fragments != NULL) {
214 struct sk_buff *head = qp->q.fragments;
215 const struct iphdr *iph;
216 int err;
217
218 rcu_read_lock();
219 head->dev = dev_get_by_index_rcu(net, qp->iif);
220 if (!head->dev)
221 goto out_rcu_unlock;
222
223 /* skb has no dst, perform route lookup again */
224 iph = ip_hdr(head);
225 err = ip_route_input_noref(head, iph->daddr, iph->saddr,
226 iph->tos, head->dev);
227 if (err)
228 goto out_rcu_unlock;
229
230 /*
231 * Only an end host needs to send an ICMP
232 * "Fragment Reassembly Timeout" message, per RFC792.
233 */
234 if (qp->user == IP_DEFRAG_AF_PACKET ||
235 ((qp->user >= IP_DEFRAG_CONNTRACK_IN) &&
236 (qp->user <= __IP_DEFRAG_CONNTRACK_IN_END) &&
237 (skb_rtable(head)->rt_type != RTN_LOCAL)))
238 goto out_rcu_unlock;
239
240
241 /* Send an ICMP "Fragment Reassembly Timeout" message. */
242 icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
243out_rcu_unlock:
244 rcu_read_unlock();
245 }
246out:
247 spin_unlock(&qp->q.lock);
248 ipq_put(qp);
249}
250
251/* Find the correct entry in the "incomplete datagrams" queue for
252 * this IP datagram, and create new one, if nothing is found.
253 */
254static inline struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user)
255{
256 struct inet_frag_queue *q;
257 struct ip4_create_arg arg;
258 unsigned int hash;
259
260 arg.iph = iph;
261 arg.user = user;
262
263 read_lock(&ip4_frags.lock);
264 hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
265
266 q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);
267 if (IS_ERR_OR_NULL(q)) {
268 inet_frag_maybe_warn_overflow(q, pr_fmt());
269 return NULL;
270 }
271 return container_of(q, struct ipq, q);
272}
273
274/* Is the fragment too far ahead to be part of ipq? */
275static inline int ip_frag_too_far(struct ipq *qp)
276{
277 struct inet_peer *peer = qp->peer;
278 unsigned int max = sysctl_ipfrag_max_dist;
279 unsigned int start, end;
280
281 int rc;
282
283 if (!peer || !max)
284 return 0;
285
286 start = qp->rid;
287 end = atomic_inc_return(&peer->rid);
288 qp->rid = end;
289
290 rc = qp->q.fragments && (end - start) > max;
291
292 if (rc) {
293 struct net *net;
294
295 net = container_of(qp->q.net, struct net, ipv4.frags);
296 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
297 }
298
299 return rc;
300}
301
302static int ip_frag_reinit(struct ipq *qp)
303{
304 struct sk_buff *fp;
305 unsigned int sum_truesize = 0;
306
307 if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
308 atomic_inc(&qp->q.refcnt);
309 return -ETIMEDOUT;
310 }
311
312 fp = qp->q.fragments;
313 do {
314 struct sk_buff *xp = fp->next;
315
316 sum_truesize += fp->truesize;
317 kfree_skb(fp);
318 fp = xp;
319 } while (fp);
320 sub_frag_mem_limit(&qp->q, sum_truesize);
321
322 qp->q.last_in = 0;
323 qp->q.len = 0;
324 qp->q.meat = 0;
325 qp->q.fragments = NULL;
326 qp->q.fragments_tail = NULL;
327 qp->iif = 0;
328 qp->ecn = 0;
329
330 return 0;
331}
332
333/* Add new segment to existing queue. */
334static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
335{
336 struct sk_buff *prev, *next;
337 struct net_device *dev;
338 int flags, offset;
339 int ihl, end;
340 int err = -ENOENT;
341 u8 ecn;
342
343 if (qp->q.last_in & INET_FRAG_COMPLETE)
344 goto err;
345
346 if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
347 unlikely(ip_frag_too_far(qp)) &&
348 unlikely(err = ip_frag_reinit(qp))) {
349 ipq_kill(qp);
350 goto err;
351 }
352
353 ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
354 offset = ntohs(ip_hdr(skb)->frag_off);
355 flags = offset & ~IP_OFFSET;
356 offset &= IP_OFFSET;
357 offset <<= 3; /* offset is in 8-byte chunks */
358 ihl = ip_hdrlen(skb);
359
360 /* Determine the position of this fragment. */
361 end = offset + skb->len - ihl;
362 err = -EINVAL;
363
364 /* Is this the final fragment? */
365 if ((flags & IP_MF) == 0) {
366 /* If we already have some bits beyond end
367 * or have different end, the segment is corrupted.
368 */
369 if (end < qp->q.len ||
370 ((qp->q.last_in & INET_FRAG_LAST_IN) && end != qp->q.len))
371 goto err;
372 qp->q.last_in |= INET_FRAG_LAST_IN;
373 qp->q.len = end;
374 } else {
375 if (end&7) {
376 end &= ~7;
377 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
378 skb->ip_summed = CHECKSUM_NONE;
379 }
380 if (end > qp->q.len) {
381 /* Some bits beyond end -> corruption. */
382 if (qp->q.last_in & INET_FRAG_LAST_IN)
383 goto err;
384 qp->q.len = end;
385 }
386 }
387 if (end == offset)
388 goto err;
389
390 err = -ENOMEM;
391 if (pskb_pull(skb, ihl) == NULL)
392 goto err;
393
394 err = pskb_trim_rcsum(skb, end - offset);
395 if (err)
396 goto err;
397
398 /* Find out which fragments are in front and at the back of us
399 * in the chain of fragments so far. We must know where to put
400 * this fragment, right?
401 */
402 prev = qp->q.fragments_tail;
403 if (!prev || FRAG_CB(prev)->offset < offset) {
404 next = NULL;
405 goto found;
406 }
407 prev = NULL;
408 for (next = qp->q.fragments; next != NULL; next = next->next) {
409 if (FRAG_CB(next)->offset >= offset)
410 break; /* bingo! */
411 prev = next;
412 }
413
414found:
415 /* We found where to put this one. Check for overlap with
416 * preceding fragment, and, if needed, align things so that
417 * any overlaps are eliminated.
418 */
419 if (prev) {
420 int i = (FRAG_CB(prev)->offset + prev->len) - offset;
421
422 if (i > 0) {
423 offset += i;
424 err = -EINVAL;
425 if (end <= offset)
426 goto err;
427 err = -ENOMEM;
428 if (!pskb_pull(skb, i))
429 goto err;
430 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
431 skb->ip_summed = CHECKSUM_NONE;
432 }
433 }
434
435 err = -ENOMEM;
436
437 while (next && FRAG_CB(next)->offset < end) {
438 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
439
440 if (i < next->len) {
441 /* Eat head of the next overlapped fragment
442 * and leave the loop. The next ones cannot overlap.
443 */
444 if (!pskb_pull(next, i))
445 goto err;
446 FRAG_CB(next)->offset += i;
447 qp->q.meat -= i;
448 if (next->ip_summed != CHECKSUM_UNNECESSARY)
449 next->ip_summed = CHECKSUM_NONE;
450 break;
451 } else {
452 struct sk_buff *free_it = next;
453
454 /* Old fragment is completely overridden with
455 * new one drop it.
456 */
457 next = next->next;
458
459 if (prev)
460 prev->next = next;
461 else
462 qp->q.fragments = next;
463
464 qp->q.meat -= free_it->len;
465 sub_frag_mem_limit(&qp->q, free_it->truesize);
466 kfree_skb(free_it);
467 }
468 }
469
470 FRAG_CB(skb)->offset = offset;
471
472 /* Insert this fragment in the chain of fragments. */
473 skb->next = next;
474 if (!next)
475 qp->q.fragments_tail = skb;
476 if (prev)
477 prev->next = skb;
478 else
479 qp->q.fragments = skb;
480
481 dev = skb->dev;
482 if (dev) {
483 qp->iif = dev->ifindex;
484 skb->dev = NULL;
485 }
486 qp->q.stamp = skb->tstamp;
487 qp->q.meat += skb->len;
488 qp->ecn |= ecn;
489 add_frag_mem_limit(&qp->q, skb->truesize);
490 if (offset == 0)
491 qp->q.last_in |= INET_FRAG_FIRST_IN;
492
493 if (ip_hdr(skb)->frag_off & htons(IP_DF) &&
494 skb->len + ihl > qp->q.max_size)
495 qp->q.max_size = skb->len + ihl;
496
497 if (qp->q.last_in == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
498 qp->q.meat == qp->q.len) {
499 unsigned long orefdst = skb->_skb_refdst;
500
501 skb->_skb_refdst = 0UL;
502 err = ip_frag_reasm(qp, prev, dev);
503 skb->_skb_refdst = orefdst;
504 return err;
505 }
506
507 skb_dst_drop(skb);
508 inet_frag_lru_move(&qp->q);
509 return -EINPROGRESS;
510
511err:
512 kfree_skb(skb);
513 return err;
514}
515
516
517/* Build a new IP datagram from all its fragments. */
518
519static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
520 struct net_device *dev)
521{
522 struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
523 struct iphdr *iph;
524 struct sk_buff *fp, *head = qp->q.fragments;
525 int len;
526 int ihlen;
527 int err;
528 int sum_truesize;
529 u8 ecn;
530
531 ipq_kill(qp);
532
533 ecn = ip_frag_ecn_table[qp->ecn];
534 if (unlikely(ecn == 0xff)) {
535 err = -EINVAL;
536 goto out_fail;
537 }
538 /* Make the one we just received the head. */
539 if (prev) {
540 head = prev->next;
541 fp = skb_clone(head, GFP_ATOMIC);
542 if (!fp)
543 goto out_nomem;
544
545 fp->next = head->next;
546 if (!fp->next)
547 qp->q.fragments_tail = fp;
548 prev->next = fp;
549
550 skb_morph(head, qp->q.fragments);
551 head->next = qp->q.fragments->next;
552
553 consume_skb(qp->q.fragments);
554 qp->q.fragments = head;
555 }
556
557 WARN_ON(head == NULL);
558 WARN_ON(FRAG_CB(head)->offset != 0);
559
560 /* Allocate a new buffer for the datagram. */
561 ihlen = ip_hdrlen(head);
562 len = ihlen + qp->q.len;
563
564 err = -E2BIG;
565 if (len > 65535)
566 goto out_oversize;
567
568 /* Head of list must not be cloned. */
569 if (skb_unclone(head, GFP_ATOMIC))
570 goto out_nomem;
571
572 /* If the first fragment is fragmented itself, we split
573 * it to two chunks: the first with data and paged part
574 * and the second, holding only fragments. */
575 if (skb_has_frag_list(head)) {
576 struct sk_buff *clone;
577 int i, plen = 0;
578
579 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
580 goto out_nomem;
581 clone->next = head->next;
582 head->next = clone;
583 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
584 skb_frag_list_init(head);
585 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
586 plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
587 clone->len = clone->data_len = head->data_len - plen;
588 head->data_len -= clone->len;
589 head->len -= clone->len;
590 clone->csum = 0;
591 clone->ip_summed = head->ip_summed;
592 add_frag_mem_limit(&qp->q, clone->truesize);
593 }
594
595 skb_push(head, head->data - skb_network_header(head));
596
597 sum_truesize = head->truesize;
598 for (fp = head->next; fp;) {
599 bool headstolen;
600 int delta;
601 struct sk_buff *next = fp->next;
602
603 sum_truesize += fp->truesize;
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
609 if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
610 kfree_skb_partial(fp, headstolen);
611 } else {
612 if (!skb_shinfo(head)->frag_list)
613 skb_shinfo(head)->frag_list = fp;
614 head->data_len += fp->len;
615 head->len += fp->len;
616 head->truesize += fp->truesize;
617 }
618 fp = next;
619 }
620 sub_frag_mem_limit(&qp->q, sum_truesize);
621
622 head->next = NULL;
623 head->dev = dev;
624 head->tstamp = qp->q.stamp;
625 IPCB(head)->frag_max_size = qp->q.max_size;
626
627 iph = ip_hdr(head);
628 /* max_size != 0 implies at least one fragment had IP_DF set */
629 iph->frag_off = qp->q.max_size ? htons(IP_DF) : 0;
630 iph->tot_len = htons(len);
631 iph->tos |= ecn;
632 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS);
633 qp->q.fragments = NULL;
634 qp->q.fragments_tail = NULL;
635 return 0;
636
637out_nomem:
638 LIMIT_NETDEBUG(KERN_ERR pr_fmt("queue_glue: no memory for gluing queue %p\n"),
639 qp);
640 err = -ENOMEM;
641 goto out_fail;
642out_oversize:
643 net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->saddr);
644out_fail:
645 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
646 return err;
647}
648
649/* Process an incoming IP datagram fragment. */
650int ip_defrag(struct sk_buff *skb, u32 user)
651{
652 struct ipq *qp;
653 struct net *net;
654
655 net = skb->dev ? dev_net(skb->dev) : dev_net(skb_dst(skb)->dev);
656 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMREQDS);
657
658 /* Start by cleaning up the memory. */
659 ip_evictor(net);
660
661 /* Lookup (or create) queue header */
662 if ((qp = ip_find(net, ip_hdr(skb), user)) != NULL) {
663 int ret;
664
665 spin_lock(&qp->q.lock);
666
667 ret = ip_frag_queue(qp, skb);
668
669 spin_unlock(&qp->q.lock);
670 ipq_put(qp);
671 return ret;
672 }
673
674 IP_INC_STATS_BH(net, IPSTATS_MIB_REASMFAILS);
675 kfree_skb(skb);
676 return -ENOMEM;
677}
678EXPORT_SYMBOL(ip_defrag);
679
680struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user)
681{
682 struct iphdr iph;
683 u32 len;
684
685 if (skb->protocol != htons(ETH_P_IP))
686 return skb;
687
688 if (!skb_copy_bits(skb, 0, &iph, sizeof(iph)))
689 return skb;
690
691 if (iph.ihl < 5 || iph.version != 4)
692 return skb;
693
694 len = ntohs(iph.tot_len);
695 if (skb->len < len || len < (iph.ihl * 4))
696 return skb;
697
698 if (ip_is_fragment(&iph)) {
699 skb = skb_share_check(skb, GFP_ATOMIC);
700 if (skb) {
701 if (!pskb_may_pull(skb, iph.ihl*4))
702 return skb;
703 if (pskb_trim_rcsum(skb, len))
704 return skb;
705 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
706 if (ip_defrag(skb, user))
707 return NULL;
708 skb_clear_hash(skb);
709 }
710 }
711 return skb;
712}
713EXPORT_SYMBOL(ip_check_defrag);
714
715#ifdef CONFIG_SYSCTL
716static int zero;
717
718static struct ctl_table ip4_frags_ns_ctl_table[] = {
719 {
720 .procname = "ipfrag_high_thresh",
721 .data = &init_net.ipv4.frags.high_thresh,
722 .maxlen = sizeof(int),
723 .mode = 0644,
724 .proc_handler = proc_dointvec
725 },
726 {
727 .procname = "ipfrag_low_thresh",
728 .data = &init_net.ipv4.frags.low_thresh,
729 .maxlen = sizeof(int),
730 .mode = 0644,
731 .proc_handler = proc_dointvec
732 },
733 {
734 .procname = "ipfrag_time",
735 .data = &init_net.ipv4.frags.timeout,
736 .maxlen = sizeof(int),
737 .mode = 0644,
738 .proc_handler = proc_dointvec_jiffies,
739 },
740 { }
741};
742
743static struct ctl_table ip4_frags_ctl_table[] = {
744 {
745 .procname = "ipfrag_secret_interval",
746 .data = &ip4_frags.secret_interval,
747 .maxlen = sizeof(int),
748 .mode = 0644,
749 .proc_handler = proc_dointvec_jiffies,
750 },
751 {
752 .procname = "ipfrag_max_dist",
753 .data = &sysctl_ipfrag_max_dist,
754 .maxlen = sizeof(int),
755 .mode = 0644,
756 .proc_handler = proc_dointvec_minmax,
757 .extra1 = &zero
758 },
759 { }
760};
761
762static int __net_init ip4_frags_ns_ctl_register(struct net *net)
763{
764 struct ctl_table *table;
765 struct ctl_table_header *hdr;
766
767 table = ip4_frags_ns_ctl_table;
768 if (!net_eq(net, &init_net)) {
769 table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
770 if (table == NULL)
771 goto err_alloc;
772
773 table[0].data = &net->ipv4.frags.high_thresh;
774 table[1].data = &net->ipv4.frags.low_thresh;
775 table[2].data = &net->ipv4.frags.timeout;
776
777 /* Don't export sysctls to unprivileged users */
778 if (net->user_ns != &init_user_ns)
779 table[0].procname = NULL;
780 }
781
782 hdr = register_net_sysctl(net, "net/ipv4", table);
783 if (hdr == NULL)
784 goto err_reg;
785
786 net->ipv4.frags_hdr = hdr;
787 return 0;
788
789err_reg:
790 if (!net_eq(net, &init_net))
791 kfree(table);
792err_alloc:
793 return -ENOMEM;
794}
795
796static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
797{
798 struct ctl_table *table;
799
800 table = net->ipv4.frags_hdr->ctl_table_arg;
801 unregister_net_sysctl_table(net->ipv4.frags_hdr);
802 kfree(table);
803}
804
805static void ip4_frags_ctl_register(void)
806{
807 register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
808}
809#else
810static inline int ip4_frags_ns_ctl_register(struct net *net)
811{
812 return 0;
813}
814
815static inline void ip4_frags_ns_ctl_unregister(struct net *net)
816{
817}
818
819static inline void ip4_frags_ctl_register(void)
820{
821}
822#endif
823
824static int __net_init ipv4_frags_init_net(struct net *net)
825{
826 /* Fragment cache limits.
827 *
828 * The fragment memory accounting code, (tries to) account for
829 * the real memory usage, by measuring both the size of frag
830 * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue))
831 * and the SKB's truesize.
832 *
833 * A 64K fragment consumes 129736 bytes (44*2944)+200
834 * (1500 truesize == 2944, sizeof(struct ipq) == 200)
835 *
836 * We will commit 4MB at one time. Should we cross that limit
837 * we will prune down to 3MB, making room for approx 8 big 64K
838 * fragments 8x128k.
839 */
840 net->ipv4.frags.high_thresh = 4 * 1024 * 1024;
841 net->ipv4.frags.low_thresh = 3 * 1024 * 1024;
842 /*
843 * Important NOTE! Fragment queue must be destroyed before MSL expires.
844 * RFC791 is wrong proposing to prolongate timer each fragment arrival
845 * by TTL.
846 */
847 net->ipv4.frags.timeout = IP_FRAG_TIME;
848
849 inet_frags_init_net(&net->ipv4.frags);
850
851 return ip4_frags_ns_ctl_register(net);
852}
853
854static void __net_exit ipv4_frags_exit_net(struct net *net)
855{
856 ip4_frags_ns_ctl_unregister(net);
857 inet_frags_exit_net(&net->ipv4.frags, &ip4_frags);
858}
859
860static struct pernet_operations ip4_frags_ops = {
861 .init = ipv4_frags_init_net,
862 .exit = ipv4_frags_exit_net,
863};
864
865void __init ipfrag_init(void)
866{
867 ip4_frags_ctl_register();
868 register_pernet_subsys(&ip4_frags_ops);
869 ip4_frags.hashfn = ip4_hashfn;
870 ip4_frags.constructor = ip4_frag_init;
871 ip4_frags.destructor = ip4_frag_free;
872 ip4_frags.skb_free = NULL;
873 ip4_frags.qsize = sizeof(struct ipq);
874 ip4_frags.match = ip4_frag_match;
875 ip4_frags.frag_expire = ip_expire;
876 ip4_frags.secret_interval = 10 * 60 * HZ;
877 inet_frags_init(&ip4_frags);
878}
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}