blob: fabb86db763b01efb6fde8d29178420e275f9dd7 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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.
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09007 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07008 * Version: $Id: ip_fragment.c,v 1.59 2002/01/12 07:54:56 davem Exp $
9 *
10 * Authors: Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
11 * Alan Cox <Alan.Cox@linux.org>
12 *
13 * Fixes:
14 * Alan Cox : Split from ip.c , see ip_input.c for history.
15 * David S. Miller : Begin massive cleanup...
16 * Andi Kleen : Add sysctls.
17 * xxxx : Overlapfrag bug.
18 * Ultima : ip_expire() kernel panic.
19 * Bill Hawes : Frag accounting and evictor fixes.
20 * John McDonald : 0 length frag bug.
21 * Alexey Kuznetsov: SMP races, threading, cleanup.
22 * Patrick McHardy : LRU queue of frag heads for evictor.
23 */
24
Herbert Xu89cee8b2005-12-13 23:14:27 -080025#include <linux/compiler.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070026#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 <net/sock.h>
38#include <net/ip.h>
39#include <net/icmp.h>
40#include <net/checksum.h>
Herbert Xu89cee8b2005-12-13 23:14:27 -080041#include <net/inetpeer.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070042#include <linux/tcp.h>
43#include <linux/udp.h>
44#include <linux/inet.h>
45#include <linux/netfilter_ipv4.h>
46
47/* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
48 * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
49 * as well. Or notify me, at least. --ANK
50 */
51
52/* Fragment cache limits. We will commit 256K at one time. Should we
53 * cross that limit we will prune down to 192K. This should cope with
54 * even the most extreme cases without allowing an attacker to measurably
55 * harm machine performance.
56 */
Brian Haleyab32ea52006-09-22 14:15:41 -070057int sysctl_ipfrag_high_thresh __read_mostly = 256*1024;
58int sysctl_ipfrag_low_thresh __read_mostly = 192*1024;
Linus Torvalds1da177e2005-04-16 15:20:36 -070059
Brian Haleyab32ea52006-09-22 14:15:41 -070060int sysctl_ipfrag_max_dist __read_mostly = 64;
Herbert Xu89cee8b2005-12-13 23:14:27 -080061
Linus Torvalds1da177e2005-04-16 15:20:36 -070062/* Important NOTE! Fragment queue must be destroyed before MSL expires.
63 * RFC791 is wrong proposing to prolongate timer each fragment arrival by TTL.
64 */
Brian Haleyab32ea52006-09-22 14:15:41 -070065int sysctl_ipfrag_time __read_mostly = IP_FRAG_TIME;
Linus Torvalds1da177e2005-04-16 15:20:36 -070066
67struct ipfrag_skb_cb
68{
69 struct inet_skb_parm h;
70 int offset;
71};
72
73#define FRAG_CB(skb) ((struct ipfrag_skb_cb*)((skb)->cb))
74
75/* Describe an entry in the "incomplete datagrams" queue. */
76struct ipq {
Yasuyuki Kozakaie7c8a412005-11-16 12:55:37 -080077 struct hlist_node list;
Linus Torvalds1da177e2005-04-16 15:20:36 -070078 struct list_head lru_list; /* lru list member */
79 u32 user;
Al Viro18277772006-09-26 22:19:02 -070080 __be32 saddr;
81 __be32 daddr;
82 __be16 id;
Linus Torvalds1da177e2005-04-16 15:20:36 -070083 u8 protocol;
84 u8 last_in;
85#define COMPLETE 4
86#define FIRST_IN 2
87#define LAST_IN 1
88
89 struct sk_buff *fragments; /* linked list of received fragments */
90 int len; /* total length of original datagram */
91 int meat;
92 spinlock_t lock;
93 atomic_t refcnt;
94 struct timer_list timer; /* when will this queue expire? */
Eric Dumazetb7aa0bf2007-04-19 16:16:32 -070095 ktime_t stamp;
Herbert Xu89cee8b2005-12-13 23:14:27 -080096 int iif;
97 unsigned int rid;
98 struct inet_peer *peer;
Linus Torvalds1da177e2005-04-16 15:20:36 -070099};
100
101/* Hash table. */
102
103#define IPQ_HASHSZ 64
104
105/* Per-bucket lock is easy to add now. */
Yasuyuki Kozakaie7c8a412005-11-16 12:55:37 -0800106static struct hlist_head ipq_hash[IPQ_HASHSZ];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700107static DEFINE_RWLOCK(ipfrag_lock);
108static u32 ipfrag_hash_rnd;
109static LIST_HEAD(ipq_lru_list);
110int ip_frag_nqueues = 0;
111
112static __inline__ void __ipq_unlink(struct ipq *qp)
113{
Yasuyuki Kozakaie7c8a412005-11-16 12:55:37 -0800114 hlist_del(&qp->list);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 list_del(&qp->lru_list);
116 ip_frag_nqueues--;
117}
118
119static __inline__ void ipq_unlink(struct ipq *ipq)
120{
121 write_lock(&ipfrag_lock);
122 __ipq_unlink(ipq);
123 write_unlock(&ipfrag_lock);
124}
125
Al Viro18277772006-09-26 22:19:02 -0700126static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127{
Al Viro18277772006-09-26 22:19:02 -0700128 return jhash_3words((__force u32)id << 16 | prot,
129 (__force u32)saddr, (__force u32)daddr,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130 ipfrag_hash_rnd) & (IPQ_HASHSZ - 1);
131}
132
133static struct timer_list ipfrag_secret_timer;
Brian Haleyab32ea52006-09-22 14:15:41 -0700134int sysctl_ipfrag_secret_interval __read_mostly = 10 * 60 * HZ;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135
136static void ipfrag_secret_rebuild(unsigned long dummy)
137{
138 unsigned long now = jiffies;
139 int i;
140
141 write_lock(&ipfrag_lock);
142 get_random_bytes(&ipfrag_hash_rnd, sizeof(u32));
143 for (i = 0; i < IPQ_HASHSZ; i++) {
144 struct ipq *q;
Yasuyuki Kozakaie7c8a412005-11-16 12:55:37 -0800145 struct hlist_node *p, *n;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146
Yasuyuki Kozakaie7c8a412005-11-16 12:55:37 -0800147 hlist_for_each_entry_safe(q, p, n, &ipq_hash[i], list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700148 unsigned int hval = ipqhashfn(q->id, q->saddr,
149 q->daddr, q->protocol);
150
151 if (hval != i) {
Yasuyuki Kozakaie7c8a412005-11-16 12:55:37 -0800152 hlist_del(&q->list);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700153
154 /* Relink to new hash chain. */
Yasuyuki Kozakaie7c8a412005-11-16 12:55:37 -0800155 hlist_add_head(&q->list, &ipq_hash[hval]);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157 }
158 }
159 write_unlock(&ipfrag_lock);
160
161 mod_timer(&ipfrag_secret_timer, now + sysctl_ipfrag_secret_interval);
162}
163
164atomic_t ip_frag_mem = ATOMIC_INIT(0); /* Memory used for fragments */
165
166/* Memory Tracking Functions. */
167static __inline__ void frag_kfree_skb(struct sk_buff *skb, int *work)
168{
169 if (work)
170 *work -= skb->truesize;
171 atomic_sub(skb->truesize, &ip_frag_mem);
172 kfree_skb(skb);
173}
174
175static __inline__ void frag_free_queue(struct ipq *qp, int *work)
176{
177 if (work)
178 *work -= sizeof(struct ipq);
179 atomic_sub(sizeof(struct ipq), &ip_frag_mem);
180 kfree(qp);
181}
182
183static __inline__ struct ipq *frag_alloc_queue(void)
184{
185 struct ipq *qp = kmalloc(sizeof(struct ipq), GFP_ATOMIC);
186
Stephen Hemminger132adf52007-03-08 20:44:43 -0800187 if (!qp)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700188 return NULL;
189 atomic_add(sizeof(struct ipq), &ip_frag_mem);
190 return qp;
191}
192
193
194/* Destruction primitives. */
195
196/* Complete destruction of ipq. */
197static void ip_frag_destroy(struct ipq *qp, int *work)
198{
199 struct sk_buff *fp;
200
201 BUG_TRAP(qp->last_in&COMPLETE);
202 BUG_TRAP(del_timer(&qp->timer) == 0);
203
Herbert Xu89cee8b2005-12-13 23:14:27 -0800204 if (qp->peer)
205 inet_putpeer(qp->peer);
206
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207 /* Release all fragment data. */
208 fp = qp->fragments;
209 while (fp) {
210 struct sk_buff *xp = fp->next;
211
212 frag_kfree_skb(fp, work);
213 fp = xp;
214 }
215
216 /* Finally, release the queue descriptor itself. */
217 frag_free_queue(qp, work);
218}
219
220static __inline__ void ipq_put(struct ipq *ipq, int *work)
221{
222 if (atomic_dec_and_test(&ipq->refcnt))
223 ip_frag_destroy(ipq, work);
224}
225
226/* Kill ipq entry. It is not destroyed immediately,
227 * because caller (and someone more) holds reference count.
228 */
229static void ipq_kill(struct ipq *ipq)
230{
231 if (del_timer(&ipq->timer))
232 atomic_dec(&ipq->refcnt);
233
234 if (!(ipq->last_in & COMPLETE)) {
235 ipq_unlink(ipq);
236 atomic_dec(&ipq->refcnt);
237 ipq->last_in |= COMPLETE;
238 }
239}
240
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900241/* Memory limiting on fragments. Evictor trashes the oldest
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242 * fragment queue until we are back under the threshold.
243 */
244static void ip_evictor(void)
245{
246 struct ipq *qp;
247 struct list_head *tmp;
248 int work;
249
250 work = atomic_read(&ip_frag_mem) - sysctl_ipfrag_low_thresh;
251 if (work <= 0)
252 return;
253
254 while (work > 0) {
255 read_lock(&ipfrag_lock);
256 if (list_empty(&ipq_lru_list)) {
257 read_unlock(&ipfrag_lock);
258 return;
259 }
260 tmp = ipq_lru_list.next;
261 qp = list_entry(tmp, struct ipq, lru_list);
262 atomic_inc(&qp->refcnt);
263 read_unlock(&ipfrag_lock);
264
265 spin_lock(&qp->lock);
266 if (!(qp->last_in&COMPLETE))
267 ipq_kill(qp);
268 spin_unlock(&qp->lock);
269
270 ipq_put(qp, &work);
271 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
272 }
273}
274
275/*
276 * Oops, a fragment queue timed out. Kill it and send an ICMP reply.
277 */
278static void ip_expire(unsigned long arg)
279{
280 struct ipq *qp = (struct ipq *) arg;
281
282 spin_lock(&qp->lock);
283
284 if (qp->last_in & COMPLETE)
285 goto out;
286
287 ipq_kill(qp);
288
289 IP_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT);
290 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
291
292 if ((qp->last_in&FIRST_IN) && qp->fragments != NULL) {
293 struct sk_buff *head = qp->fragments;
294 /* Send an ICMP "Fragment Reassembly Timeout" message. */
Eric W. Biederman881d9662007-09-17 11:56:21 -0700295 if ((head->dev = dev_get_by_index(&init_net, qp->iif)) != NULL) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700296 icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
297 dev_put(head->dev);
298 }
299 }
300out:
301 spin_unlock(&qp->lock);
302 ipq_put(qp, NULL);
303}
304
305/* Creation primitives. */
306
David S. Miller55c00222006-04-09 22:43:55 -0700307static struct ipq *ip_frag_intern(struct ipq *qp_in)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700308{
309 struct ipq *qp;
Yasuyuki Kozakaie7c8a412005-11-16 12:55:37 -0800310#ifdef CONFIG_SMP
311 struct hlist_node *n;
312#endif
David S. Miller55c00222006-04-09 22:43:55 -0700313 unsigned int hash;
314
Linus Torvalds1da177e2005-04-16 15:20:36 -0700315 write_lock(&ipfrag_lock);
David S. Miller55c00222006-04-09 22:43:55 -0700316 hash = ipqhashfn(qp_in->id, qp_in->saddr, qp_in->daddr,
317 qp_in->protocol);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700318#ifdef CONFIG_SMP
319 /* With SMP race we have to recheck hash table, because
320 * such entry could be created on other cpu, while we
321 * promoted read lock to write lock.
322 */
Yasuyuki Kozakaie7c8a412005-11-16 12:55:37 -0800323 hlist_for_each_entry(qp, n, &ipq_hash[hash], list) {
Stephen Hemminger132adf52007-03-08 20:44:43 -0800324 if (qp->id == qp_in->id &&
325 qp->saddr == qp_in->saddr &&
326 qp->daddr == qp_in->daddr &&
327 qp->protocol == qp_in->protocol &&
328 qp->user == qp_in->user) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700329 atomic_inc(&qp->refcnt);
330 write_unlock(&ipfrag_lock);
331 qp_in->last_in |= COMPLETE;
332 ipq_put(qp_in, NULL);
333 return qp;
334 }
335 }
336#endif
337 qp = qp_in;
338
339 if (!mod_timer(&qp->timer, jiffies + sysctl_ipfrag_time))
340 atomic_inc(&qp->refcnt);
341
342 atomic_inc(&qp->refcnt);
Yasuyuki Kozakaie7c8a412005-11-16 12:55:37 -0800343 hlist_add_head(&qp->list, &ipq_hash[hash]);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344 INIT_LIST_HEAD(&qp->lru_list);
345 list_add_tail(&qp->lru_list, &ipq_lru_list);
346 ip_frag_nqueues++;
347 write_unlock(&ipfrag_lock);
348 return qp;
349}
350
351/* Add an entry to the 'ipq' queue for a newly received IP datagram. */
David S. Miller55c00222006-04-09 22:43:55 -0700352static struct ipq *ip_frag_create(struct iphdr *iph, u32 user)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700353{
354 struct ipq *qp;
355
356 if ((qp = frag_alloc_queue()) == NULL)
357 goto out_nomem;
358
359 qp->protocol = iph->protocol;
360 qp->last_in = 0;
361 qp->id = iph->id;
362 qp->saddr = iph->saddr;
363 qp->daddr = iph->daddr;
364 qp->user = user;
365 qp->len = 0;
366 qp->meat = 0;
367 qp->fragments = NULL;
368 qp->iif = 0;
Herbert Xu89cee8b2005-12-13 23:14:27 -0800369 qp->peer = sysctl_ipfrag_max_dist ? inet_getpeer(iph->saddr, 1) : NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700370
371 /* Initialize a timer for this entry. */
372 init_timer(&qp->timer);
373 qp->timer.data = (unsigned long) qp; /* pointer to queue */
374 qp->timer.function = ip_expire; /* expire function */
375 spin_lock_init(&qp->lock);
376 atomic_set(&qp->refcnt, 1);
377
David S. Miller55c00222006-04-09 22:43:55 -0700378 return ip_frag_intern(qp);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700379
380out_nomem:
Patrick McHardy64ce2072005-08-09 20:50:53 -0700381 LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382 return NULL;
383}
384
385/* Find the correct entry in the "incomplete datagrams" queue for
386 * this IP datagram, and create new one, if nothing is found.
387 */
388static inline struct ipq *ip_find(struct iphdr *iph, u32 user)
389{
Alexey Dobriyan76ab6082006-01-06 13:24:29 -0800390 __be16 id = iph->id;
Al Viro18277772006-09-26 22:19:02 -0700391 __be32 saddr = iph->saddr;
392 __be32 daddr = iph->daddr;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700393 __u8 protocol = iph->protocol;
David S. Miller55c00222006-04-09 22:43:55 -0700394 unsigned int hash;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700395 struct ipq *qp;
Yasuyuki Kozakaie7c8a412005-11-16 12:55:37 -0800396 struct hlist_node *n;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700397
398 read_lock(&ipfrag_lock);
David S. Miller55c00222006-04-09 22:43:55 -0700399 hash = ipqhashfn(id, saddr, daddr, protocol);
Yasuyuki Kozakaie7c8a412005-11-16 12:55:37 -0800400 hlist_for_each_entry(qp, n, &ipq_hash[hash], list) {
Stephen Hemminger132adf52007-03-08 20:44:43 -0800401 if (qp->id == id &&
402 qp->saddr == saddr &&
403 qp->daddr == daddr &&
404 qp->protocol == protocol &&
405 qp->user == user) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700406 atomic_inc(&qp->refcnt);
407 read_unlock(&ipfrag_lock);
408 return qp;
409 }
410 }
411 read_unlock(&ipfrag_lock);
412
David S. Miller55c00222006-04-09 22:43:55 -0700413 return ip_frag_create(iph, user);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700414}
415
Herbert Xu89cee8b2005-12-13 23:14:27 -0800416/* Is the fragment too far ahead to be part of ipq? */
417static inline int ip_frag_too_far(struct ipq *qp)
418{
419 struct inet_peer *peer = qp->peer;
420 unsigned int max = sysctl_ipfrag_max_dist;
421 unsigned int start, end;
422
423 int rc;
424
425 if (!peer || !max)
426 return 0;
427
428 start = qp->rid;
429 end = atomic_inc_return(&peer->rid);
430 qp->rid = end;
431
432 rc = qp->fragments && (end - start) > max;
433
434 if (rc) {
435 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
436 }
437
438 return rc;
439}
440
441static int ip_frag_reinit(struct ipq *qp)
442{
443 struct sk_buff *fp;
444
445 if (!mod_timer(&qp->timer, jiffies + sysctl_ipfrag_time)) {
446 atomic_inc(&qp->refcnt);
447 return -ETIMEDOUT;
448 }
449
450 fp = qp->fragments;
451 do {
452 struct sk_buff *xp = fp->next;
453 frag_kfree_skb(fp, NULL);
454 fp = xp;
455 } while (fp);
456
457 qp->last_in = 0;
458 qp->len = 0;
459 qp->meat = 0;
460 qp->fragments = NULL;
461 qp->iif = 0;
462
463 return 0;
464}
465
Linus Torvalds1da177e2005-04-16 15:20:36 -0700466/* Add new segment to existing queue. */
467static void ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
468{
469 struct sk_buff *prev, *next;
470 int flags, offset;
471 int ihl, end;
472
473 if (qp->last_in & COMPLETE)
474 goto err;
475
Herbert Xu89cee8b2005-12-13 23:14:27 -0800476 if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
477 unlikely(ip_frag_too_far(qp)) && unlikely(ip_frag_reinit(qp))) {
478 ipq_kill(qp);
479 goto err;
480 }
481
Arnaldo Carvalho de Meloeddc9ec2007-04-20 22:47:35 -0700482 offset = ntohs(ip_hdr(skb)->frag_off);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700483 flags = offset & ~IP_OFFSET;
484 offset &= IP_OFFSET;
485 offset <<= 3; /* offset is in 8-byte chunks */
Arnaldo Carvalho de Meloc9bdd4b2007-03-12 20:09:15 -0300486 ihl = ip_hdrlen(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700487
488 /* Determine the position of this fragment. */
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900489 end = offset + skb->len - ihl;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700490
491 /* Is this the final fragment? */
492 if ((flags & IP_MF) == 0) {
493 /* If we already have some bits beyond end
494 * or have different end, the segment is corrrupted.
495 */
496 if (end < qp->len ||
497 ((qp->last_in & LAST_IN) && end != qp->len))
498 goto err;
499 qp->last_in |= LAST_IN;
500 qp->len = end;
501 } else {
502 if (end&7) {
503 end &= ~7;
504 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
505 skb->ip_summed = CHECKSUM_NONE;
506 }
507 if (end > qp->len) {
508 /* Some bits beyond end -> corruption. */
509 if (qp->last_in & LAST_IN)
510 goto err;
511 qp->len = end;
512 }
513 }
514 if (end == offset)
515 goto err;
516
517 if (pskb_pull(skb, ihl) == NULL)
518 goto err;
Stephen Hemminger48bc41a2005-09-06 15:51:48 -0700519 if (pskb_trim_rcsum(skb, end-offset))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700520 goto err;
521
522 /* Find out which fragments are in front and at the back of us
523 * in the chain of fragments so far. We must know where to put
524 * this fragment, right?
525 */
526 prev = NULL;
Stephen Hemminger132adf52007-03-08 20:44:43 -0800527 for (next = qp->fragments; next != NULL; next = next->next) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700528 if (FRAG_CB(next)->offset >= offset)
529 break; /* bingo! */
530 prev = next;
531 }
532
533 /* We found where to put this one. Check for overlap with
534 * preceding fragment, and, if needed, align things so that
535 * any overlaps are eliminated.
536 */
537 if (prev) {
538 int i = (FRAG_CB(prev)->offset + prev->len) - offset;
539
540 if (i > 0) {
541 offset += i;
542 if (end <= offset)
543 goto err;
544 if (!pskb_pull(skb, i))
545 goto err;
546 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
547 skb->ip_summed = CHECKSUM_NONE;
548 }
549 }
550
551 while (next && FRAG_CB(next)->offset < end) {
552 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
553
554 if (i < next->len) {
555 /* Eat head of the next overlapped fragment
556 * and leave the loop. The next ones cannot overlap.
557 */
558 if (!pskb_pull(next, i))
559 goto err;
560 FRAG_CB(next)->offset += i;
561 qp->meat -= i;
562 if (next->ip_summed != CHECKSUM_UNNECESSARY)
563 next->ip_summed = CHECKSUM_NONE;
564 break;
565 } else {
566 struct sk_buff *free_it = next;
567
Peter Zijlstra47c6bf772006-12-12 19:48:59 +0100568 /* Old fragment is completely overridden with
Linus Torvalds1da177e2005-04-16 15:20:36 -0700569 * new one drop it.
570 */
571 next = next->next;
572
573 if (prev)
574 prev->next = next;
575 else
576 qp->fragments = next;
577
578 qp->meat -= free_it->len;
579 frag_kfree_skb(free_it, NULL);
580 }
581 }
582
583 FRAG_CB(skb)->offset = offset;
584
585 /* Insert this fragment in the chain of fragments. */
586 skb->next = next;
587 if (prev)
588 prev->next = skb;
589 else
590 qp->fragments = skb;
591
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900592 if (skb->dev)
593 qp->iif = skb->dev->ifindex;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700594 skb->dev = NULL;
Eric Dumazetb7aa0bf2007-04-19 16:16:32 -0700595 qp->stamp = skb->tstamp;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700596 qp->meat += skb->len;
597 atomic_add(skb->truesize, &ip_frag_mem);
598 if (offset == 0)
599 qp->last_in |= FIRST_IN;
600
601 write_lock(&ipfrag_lock);
602 list_move_tail(&qp->lru_list, &ipq_lru_list);
603 write_unlock(&ipfrag_lock);
604
605 return;
606
607err:
608 kfree_skb(skb);
609}
610
611
612/* Build a new IP datagram from all its fragments. */
613
614static struct sk_buff *ip_frag_reasm(struct ipq *qp, struct net_device *dev)
615{
616 struct iphdr *iph;
617 struct sk_buff *fp, *head = qp->fragments;
618 int len;
619 int ihlen;
620
621 ipq_kill(qp);
622
623 BUG_TRAP(head != NULL);
624 BUG_TRAP(FRAG_CB(head)->offset == 0);
625
626 /* Allocate a new buffer for the datagram. */
Arnaldo Carvalho de Meloc9bdd4b2007-03-12 20:09:15 -0300627 ihlen = ip_hdrlen(head);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700628 len = ihlen + qp->len;
629
Stephen Hemminger132adf52007-03-08 20:44:43 -0800630 if (len > 65535)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631 goto out_oversize;
632
633 /* Head of list must not be cloned. */
634 if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC))
635 goto out_nomem;
636
637 /* If the first fragment is fragmented itself, we split
638 * it to two chunks: the first with data and paged part
639 * and the second, holding only fragments. */
640 if (skb_shinfo(head)->frag_list) {
641 struct sk_buff *clone;
642 int i, plen = 0;
643
644 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
645 goto out_nomem;
646 clone->next = head->next;
647 head->next = clone;
648 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
649 skb_shinfo(head)->frag_list = NULL;
650 for (i=0; i<skb_shinfo(head)->nr_frags; i++)
651 plen += skb_shinfo(head)->frags[i].size;
652 clone->len = clone->data_len = head->data_len - plen;
653 head->data_len -= clone->len;
654 head->len -= clone->len;
655 clone->csum = 0;
656 clone->ip_summed = head->ip_summed;
657 atomic_add(clone->truesize, &ip_frag_mem);
658 }
659
660 skb_shinfo(head)->frag_list = head->next;
Arnaldo Carvalho de Melod56f90a2007-04-10 20:50:43 -0700661 skb_push(head, head->data - skb_network_header(head));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700662 atomic_sub(head->truesize, &ip_frag_mem);
663
664 for (fp=head->next; fp; fp = fp->next) {
665 head->data_len += fp->len;
666 head->len += fp->len;
667 if (head->ip_summed != fp->ip_summed)
668 head->ip_summed = CHECKSUM_NONE;
Patrick McHardy84fa7932006-08-29 16:44:56 -0700669 else if (head->ip_summed == CHECKSUM_COMPLETE)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700670 head->csum = csum_add(head->csum, fp->csum);
671 head->truesize += fp->truesize;
672 atomic_sub(fp->truesize, &ip_frag_mem);
673 }
674
675 head->next = NULL;
676 head->dev = dev;
Eric Dumazetb7aa0bf2007-04-19 16:16:32 -0700677 head->tstamp = qp->stamp;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700678
Arnaldo Carvalho de Meloeddc9ec2007-04-20 22:47:35 -0700679 iph = ip_hdr(head);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680 iph->frag_off = 0;
681 iph->tot_len = htons(len);
682 IP_INC_STATS_BH(IPSTATS_MIB_REASMOKS);
683 qp->fragments = NULL;
684 return head;
685
686out_nomem:
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900687 LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing "
Patrick McHardy64ce2072005-08-09 20:50:53 -0700688 "queue %p\n", qp);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700689 goto out_fail;
690out_oversize:
691 if (net_ratelimit())
692 printk(KERN_INFO
693 "Oversized IP packet from %d.%d.%d.%d.\n",
694 NIPQUAD(qp->saddr));
695out_fail:
696 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
697 return NULL;
698}
699
700/* Process an incoming IP datagram fragment. */
701struct sk_buff *ip_defrag(struct sk_buff *skb, u32 user)
702{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700703 struct ipq *qp;
704 struct net_device *dev;
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900705
Linus Torvalds1da177e2005-04-16 15:20:36 -0700706 IP_INC_STATS_BH(IPSTATS_MIB_REASMREQDS);
707
708 /* Start by cleaning up the memory. */
709 if (atomic_read(&ip_frag_mem) > sysctl_ipfrag_high_thresh)
710 ip_evictor();
711
712 dev = skb->dev;
713
714 /* Lookup (or create) queue header */
Arnaldo Carvalho de Meloeddc9ec2007-04-20 22:47:35 -0700715 if ((qp = ip_find(ip_hdr(skb), user)) != NULL) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716 struct sk_buff *ret = NULL;
717
718 spin_lock(&qp->lock);
719
720 ip_frag_queue(qp, skb);
721
722 if (qp->last_in == (FIRST_IN|LAST_IN) &&
723 qp->meat == qp->len)
724 ret = ip_frag_reasm(qp, dev);
725
726 spin_unlock(&qp->lock);
727 ipq_put(qp, NULL);
728 return ret;
729 }
730
731 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
732 kfree_skb(skb);
733 return NULL;
734}
735
Eric Dumazetb7aa0bf2007-04-19 16:16:32 -0700736void __init ipfrag_init(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700737{
738 ipfrag_hash_rnd = (u32) ((num_physpages ^ (num_physpages>>7)) ^
739 (jiffies ^ (jiffies >> 6)));
740
741 init_timer(&ipfrag_secret_timer);
742 ipfrag_secret_timer.function = ipfrag_secret_rebuild;
743 ipfrag_secret_timer.expires = jiffies + sysctl_ipfrag_secret_interval;
744 add_timer(&ipfrag_secret_timer);
745}
746
747EXPORT_SYMBOL(ip_defrag);