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.
6 * The IP fragmentation functionality.
8 * Version: $Id: ip_fragment.c,v 1.59 2002/01/12 07:54:56 davem Exp $
10 * Authors: Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
11 * Alan Cox <Alan.Cox@linux.org>
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.
25 #include <linux/compiler.h>
26 #include <linux/module.h>
27 #include <linux/types.h>
29 #include <linux/jiffies.h>
30 #include <linux/skbuff.h>
31 #include <linux/list.h>
33 #include <linux/icmp.h>
34 #include <linux/netdevice.h>
35 #include <linux/jhash.h>
36 #include <linux/random.h>
40 #include <net/checksum.h>
41 #include <net/inetpeer.h>
42 #include <net/inet_frag.h>
43 #include <linux/tcp.h>
44 #include <linux/udp.h>
45 #include <linux/inet.h>
46 #include <linux/netfilter_ipv4.h>
48 /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
49 * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
50 * as well. Or notify me, at least. --ANK
53 int sysctl_ipfrag_max_dist __read_mostly
= 64;
57 struct inet_skb_parm h
;
61 #define FRAG_CB(skb) ((struct ipfrag_skb_cb*)((skb)->cb))
63 /* Describe an entry in the "incomplete datagrams" queue. */
65 struct inet_frag_queue q
;
74 struct inet_peer
*peer
;
77 struct inet_frags_ctl ip4_frags_ctl __read_mostly
= {
79 * Fragment cache limits. We will commit 256K at one time. Should we
80 * cross that limit we will prune down to 192K. This should cope with
81 * even the most extreme cases without allowing an attacker to
82 * measurably harm machine performance.
84 .high_thresh
= 256 * 1024,
85 .low_thresh
= 192 * 1024,
88 * Important NOTE! Fragment queue must be destroyed before MSL expires.
89 * RFC791 is wrong proposing to prolongate timer each fragment arrival
92 .timeout
= IP_FRAG_TIME
,
93 .secret_interval
= 10 * 60 * HZ
,
96 static struct inet_frags ip4_frags
;
98 int ip_frag_nqueues(void)
100 return ip4_frags
.nqueues
;
103 int ip_frag_mem(void)
105 return atomic_read(&ip4_frags
.mem
);
108 static int ip_frag_reasm(struct ipq
*qp
, struct sk_buff
*prev
,
109 struct net_device
*dev
);
111 struct ip4_create_arg
{
116 static unsigned int ipqhashfn(__be16 id
, __be32 saddr
, __be32 daddr
, u8 prot
)
118 return jhash_3words((__force u32
)id
<< 16 | prot
,
119 (__force u32
)saddr
, (__force u32
)daddr
,
120 ip4_frags
.rnd
) & (INETFRAGS_HASHSZ
- 1);
123 static unsigned int ip4_hashfn(struct inet_frag_queue
*q
)
127 ipq
= container_of(q
, struct ipq
, q
);
128 return ipqhashfn(ipq
->id
, ipq
->saddr
, ipq
->daddr
, ipq
->protocol
);
131 static int ip4_frag_match(struct inet_frag_queue
*q
, void *a
)
134 struct ip4_create_arg
*arg
= a
;
136 qp
= container_of(q
, struct ipq
, q
);
137 return (qp
->id
== arg
->iph
->id
&&
138 qp
->saddr
== arg
->iph
->saddr
&&
139 qp
->daddr
== arg
->iph
->daddr
&&
140 qp
->protocol
== arg
->iph
->protocol
&&
141 qp
->user
== arg
->user
);
144 /* Memory Tracking Functions. */
145 static __inline__
void frag_kfree_skb(struct sk_buff
*skb
, int *work
)
148 *work
-= skb
->truesize
;
149 atomic_sub(skb
->truesize
, &ip4_frags
.mem
);
153 static void ip4_frag_init(struct inet_frag_queue
*q
, void *a
)
155 struct ipq
*qp
= container_of(q
, struct ipq
, q
);
156 struct ip4_create_arg
*arg
= a
;
158 qp
->protocol
= arg
->iph
->protocol
;
159 qp
->id
= arg
->iph
->id
;
160 qp
->saddr
= arg
->iph
->saddr
;
161 qp
->daddr
= arg
->iph
->daddr
;
162 qp
->user
= arg
->user
;
163 qp
->peer
= sysctl_ipfrag_max_dist
?
164 inet_getpeer(arg
->iph
->saddr
, 1) : NULL
;
167 static __inline__
void ip4_frag_free(struct inet_frag_queue
*q
)
171 qp
= container_of(q
, struct ipq
, q
);
173 inet_putpeer(qp
->peer
);
177 /* Destruction primitives. */
179 static __inline__
void ipq_put(struct ipq
*ipq
)
181 inet_frag_put(&ipq
->q
, &ip4_frags
);
184 /* Kill ipq entry. It is not destroyed immediately,
185 * because caller (and someone more) holds reference count.
187 static void ipq_kill(struct ipq
*ipq
)
189 inet_frag_kill(&ipq
->q
, &ip4_frags
);
192 /* Memory limiting on fragments. Evictor trashes the oldest
193 * fragment queue until we are back under the threshold.
195 static void ip_evictor(void)
199 evicted
= inet_frag_evictor(&ip4_frags
);
201 IP_ADD_STATS_BH(IPSTATS_MIB_REASMFAILS
, evicted
);
205 * Oops, a fragment queue timed out. Kill it and send an ICMP reply.
207 static void ip_expire(unsigned long arg
)
211 qp
= container_of((struct inet_frag_queue
*) arg
, struct ipq
, q
);
213 spin_lock(&qp
->q
.lock
);
215 if (qp
->q
.last_in
& COMPLETE
)
220 IP_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT
);
221 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS
);
223 if ((qp
->q
.last_in
&FIRST_IN
) && qp
->q
.fragments
!= NULL
) {
224 struct sk_buff
*head
= qp
->q
.fragments
;
225 /* Send an ICMP "Fragment Reassembly Timeout" message. */
226 if ((head
->dev
= dev_get_by_index(&init_net
, qp
->iif
)) != NULL
) {
227 icmp_send(head
, ICMP_TIME_EXCEEDED
, ICMP_EXC_FRAGTIME
, 0);
232 spin_unlock(&qp
->q
.lock
);
236 /* Find the correct entry in the "incomplete datagrams" queue for
237 * this IP datagram, and create new one, if nothing is found.
239 static inline struct ipq
*ip_find(struct iphdr
*iph
, u32 user
)
241 struct inet_frag_queue
*q
;
242 struct ip4_create_arg arg
;
247 hash
= ipqhashfn(iph
->id
, iph
->saddr
, iph
->daddr
, iph
->protocol
);
249 q
= inet_frag_find(&ip4_frags
, &arg
, hash
);
253 return container_of(q
, struct ipq
, q
);
256 LIMIT_NETDEBUG(KERN_ERR
"ip_frag_create: no memory left !\n");
260 /* Is the fragment too far ahead to be part of ipq? */
261 static inline int ip_frag_too_far(struct ipq
*qp
)
263 struct inet_peer
*peer
= qp
->peer
;
264 unsigned int max
= sysctl_ipfrag_max_dist
;
265 unsigned int start
, end
;
273 end
= atomic_inc_return(&peer
->rid
);
276 rc
= qp
->q
.fragments
&& (end
- start
) > max
;
279 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS
);
285 static int ip_frag_reinit(struct ipq
*qp
)
289 if (!mod_timer(&qp
->q
.timer
, jiffies
+ ip4_frags_ctl
.timeout
)) {
290 atomic_inc(&qp
->q
.refcnt
);
294 fp
= qp
->q
.fragments
;
296 struct sk_buff
*xp
= fp
->next
;
297 frag_kfree_skb(fp
, NULL
);
304 qp
->q
.fragments
= NULL
;
310 /* Add new segment to existing queue. */
311 static int ip_frag_queue(struct ipq
*qp
, struct sk_buff
*skb
)
313 struct sk_buff
*prev
, *next
;
314 struct net_device
*dev
;
319 if (qp
->q
.last_in
& COMPLETE
)
322 if (!(IPCB(skb
)->flags
& IPSKB_FRAG_COMPLETE
) &&
323 unlikely(ip_frag_too_far(qp
)) &&
324 unlikely(err
= ip_frag_reinit(qp
))) {
329 offset
= ntohs(ip_hdr(skb
)->frag_off
);
330 flags
= offset
& ~IP_OFFSET
;
332 offset
<<= 3; /* offset is in 8-byte chunks */
333 ihl
= ip_hdrlen(skb
);
335 /* Determine the position of this fragment. */
336 end
= offset
+ skb
->len
- ihl
;
339 /* Is this the final fragment? */
340 if ((flags
& IP_MF
) == 0) {
341 /* If we already have some bits beyond end
342 * or have different end, the segment is corrrupted.
344 if (end
< qp
->q
.len
||
345 ((qp
->q
.last_in
& LAST_IN
) && end
!= qp
->q
.len
))
347 qp
->q
.last_in
|= LAST_IN
;
352 if (skb
->ip_summed
!= CHECKSUM_UNNECESSARY
)
353 skb
->ip_summed
= CHECKSUM_NONE
;
355 if (end
> qp
->q
.len
) {
356 /* Some bits beyond end -> corruption. */
357 if (qp
->q
.last_in
& LAST_IN
)
366 if (pskb_pull(skb
, ihl
) == NULL
)
369 err
= pskb_trim_rcsum(skb
, end
- offset
);
373 /* Find out which fragments are in front and at the back of us
374 * in the chain of fragments so far. We must know where to put
375 * this fragment, right?
378 for (next
= qp
->q
.fragments
; next
!= NULL
; next
= next
->next
) {
379 if (FRAG_CB(next
)->offset
>= offset
)
384 /* We found where to put this one. Check for overlap with
385 * preceding fragment, and, if needed, align things so that
386 * any overlaps are eliminated.
389 int i
= (FRAG_CB(prev
)->offset
+ prev
->len
) - offset
;
397 if (!pskb_pull(skb
, i
))
399 if (skb
->ip_summed
!= CHECKSUM_UNNECESSARY
)
400 skb
->ip_summed
= CHECKSUM_NONE
;
406 while (next
&& FRAG_CB(next
)->offset
< end
) {
407 int i
= end
- FRAG_CB(next
)->offset
; /* overlap is 'i' bytes */
410 /* Eat head of the next overlapped fragment
411 * and leave the loop. The next ones cannot overlap.
413 if (!pskb_pull(next
, i
))
415 FRAG_CB(next
)->offset
+= i
;
417 if (next
->ip_summed
!= CHECKSUM_UNNECESSARY
)
418 next
->ip_summed
= CHECKSUM_NONE
;
421 struct sk_buff
*free_it
= next
;
423 /* Old fragment is completely overridden with
431 qp
->q
.fragments
= next
;
433 qp
->q
.meat
-= free_it
->len
;
434 frag_kfree_skb(free_it
, NULL
);
438 FRAG_CB(skb
)->offset
= offset
;
440 /* Insert this fragment in the chain of fragments. */
445 qp
->q
.fragments
= skb
;
449 qp
->iif
= dev
->ifindex
;
452 qp
->q
.stamp
= skb
->tstamp
;
453 qp
->q
.meat
+= skb
->len
;
454 atomic_add(skb
->truesize
, &ip4_frags
.mem
);
456 qp
->q
.last_in
|= FIRST_IN
;
458 if (qp
->q
.last_in
== (FIRST_IN
| LAST_IN
) && qp
->q
.meat
== qp
->q
.len
)
459 return ip_frag_reasm(qp
, prev
, dev
);
461 write_lock(&ip4_frags
.lock
);
462 list_move_tail(&qp
->q
.lru_list
, &ip4_frags
.lru_list
);
463 write_unlock(&ip4_frags
.lock
);
472 /* Build a new IP datagram from all its fragments. */
474 static int ip_frag_reasm(struct ipq
*qp
, struct sk_buff
*prev
,
475 struct net_device
*dev
)
478 struct sk_buff
*fp
, *head
= qp
->q
.fragments
;
485 /* Make the one we just received the head. */
488 fp
= skb_clone(head
, GFP_ATOMIC
);
492 fp
->next
= head
->next
;
495 skb_morph(head
, qp
->q
.fragments
);
496 head
->next
= qp
->q
.fragments
->next
;
498 kfree_skb(qp
->q
.fragments
);
499 qp
->q
.fragments
= head
;
502 BUG_TRAP(head
!= NULL
);
503 BUG_TRAP(FRAG_CB(head
)->offset
== 0);
505 /* Allocate a new buffer for the datagram. */
506 ihlen
= ip_hdrlen(head
);
507 len
= ihlen
+ qp
->q
.len
;
513 /* Head of list must not be cloned. */
514 if (skb_cloned(head
) && pskb_expand_head(head
, 0, 0, GFP_ATOMIC
))
517 /* If the first fragment is fragmented itself, we split
518 * it to two chunks: the first with data and paged part
519 * and the second, holding only fragments. */
520 if (skb_shinfo(head
)->frag_list
) {
521 struct sk_buff
*clone
;
524 if ((clone
= alloc_skb(0, GFP_ATOMIC
)) == NULL
)
526 clone
->next
= head
->next
;
528 skb_shinfo(clone
)->frag_list
= skb_shinfo(head
)->frag_list
;
529 skb_shinfo(head
)->frag_list
= NULL
;
530 for (i
=0; i
<skb_shinfo(head
)->nr_frags
; i
++)
531 plen
+= skb_shinfo(head
)->frags
[i
].size
;
532 clone
->len
= clone
->data_len
= head
->data_len
- plen
;
533 head
->data_len
-= clone
->len
;
534 head
->len
-= clone
->len
;
536 clone
->ip_summed
= head
->ip_summed
;
537 atomic_add(clone
->truesize
, &ip4_frags
.mem
);
540 skb_shinfo(head
)->frag_list
= head
->next
;
541 skb_push(head
, head
->data
- skb_network_header(head
));
542 atomic_sub(head
->truesize
, &ip4_frags
.mem
);
544 for (fp
=head
->next
; fp
; fp
= fp
->next
) {
545 head
->data_len
+= fp
->len
;
546 head
->len
+= fp
->len
;
547 if (head
->ip_summed
!= fp
->ip_summed
)
548 head
->ip_summed
= CHECKSUM_NONE
;
549 else if (head
->ip_summed
== CHECKSUM_COMPLETE
)
550 head
->csum
= csum_add(head
->csum
, fp
->csum
);
551 head
->truesize
+= fp
->truesize
;
552 atomic_sub(fp
->truesize
, &ip4_frags
.mem
);
557 head
->tstamp
= qp
->q
.stamp
;
561 iph
->tot_len
= htons(len
);
562 IP_INC_STATS_BH(IPSTATS_MIB_REASMOKS
);
563 qp
->q
.fragments
= NULL
;
567 LIMIT_NETDEBUG(KERN_ERR
"IP: queue_glue: no memory for gluing "
574 "Oversized IP packet from %d.%d.%d.%d.\n",
577 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS
);
581 /* Process an incoming IP datagram fragment. */
582 int ip_defrag(struct sk_buff
*skb
, u32 user
)
586 IP_INC_STATS_BH(IPSTATS_MIB_REASMREQDS
);
588 /* Start by cleaning up the memory. */
589 if (atomic_read(&ip4_frags
.mem
) > ip4_frags_ctl
.high_thresh
)
592 /* Lookup (or create) queue header */
593 if ((qp
= ip_find(ip_hdr(skb
), user
)) != NULL
) {
596 spin_lock(&qp
->q
.lock
);
598 ret
= ip_frag_queue(qp
, skb
);
600 spin_unlock(&qp
->q
.lock
);
605 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS
);
610 void __init
ipfrag_init(void)
612 ip4_frags
.ctl
= &ip4_frags_ctl
;
613 ip4_frags
.hashfn
= ip4_hashfn
;
614 ip4_frags
.constructor
= ip4_frag_init
;
615 ip4_frags
.destructor
= ip4_frag_free
;
616 ip4_frags
.skb_free
= NULL
;
617 ip4_frags
.qsize
= sizeof(struct ipq
);
618 ip4_frags
.match
= ip4_frag_match
;
619 ip4_frags
.frag_expire
= ip_expire
;
620 inet_frags_init(&ip4_frags
);
623 EXPORT_SYMBOL(ip_defrag
);