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 static 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 static 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,
86 .secret_interval = 10 * 60 * HZ,
89 static struct inet_frags ip4_frags;
91 int ip_frag_nqueues(struct net *net)
93 return net->ipv4.frags.nqueues;
96 int ip_frag_mem(struct net *net)
98 return atomic_read(&net->ipv4.frags.mem);
101 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
102 struct net_device *dev);
104 struct ip4_create_arg {
109 static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
111 return jhash_3words((__force u32)id << 16 | prot,
112 (__force u32)saddr, (__force u32)daddr,
113 ip4_frags.rnd) & (INETFRAGS_HASHSZ - 1);
116 static unsigned int ip4_hashfn(struct inet_frag_queue *q)
120 ipq = container_of(q, struct ipq, q);
121 return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);
124 static int ip4_frag_match(struct inet_frag_queue *q, void *a)
127 struct ip4_create_arg *arg = a;
129 qp = container_of(q, struct ipq, q);
130 return (qp->id == arg->iph->id &&
131 qp->saddr == arg->iph->saddr &&
132 qp->daddr == arg->iph->daddr &&
133 qp->protocol == arg->iph->protocol &&
134 qp->user == arg->user);
137 /* Memory Tracking Functions. */
138 static __inline__ void frag_kfree_skb(struct netns_frags *nf,
139 struct sk_buff *skb, int *work)
142 *work -= skb->truesize;
143 atomic_sub(skb->truesize, &nf->mem);
147 static void ip4_frag_init(struct inet_frag_queue *q, void *a)
149 struct ipq *qp = container_of(q, struct ipq, q);
150 struct ip4_create_arg *arg = a;
152 qp->protocol = arg->iph->protocol;
153 qp->id = arg->iph->id;
154 qp->saddr = arg->iph->saddr;
155 qp->daddr = arg->iph->daddr;
156 qp->user = arg->user;
157 qp->peer = sysctl_ipfrag_max_dist ?
158 inet_getpeer(arg->iph->saddr, 1) : NULL;
161 static __inline__ void ip4_frag_free(struct inet_frag_queue *q)
165 qp = container_of(q, struct ipq, q);
167 inet_putpeer(qp->peer);
171 /* Destruction primitives. */
173 static __inline__ void ipq_put(struct ipq *ipq)
175 inet_frag_put(&ipq->q, &ip4_frags);
178 /* Kill ipq entry. It is not destroyed immediately,
179 * because caller (and someone more) holds reference count.
181 static void ipq_kill(struct ipq *ipq)
183 inet_frag_kill(&ipq->q, &ip4_frags);
186 /* Memory limiting on fragments. Evictor trashes the oldest
187 * fragment queue until we are back under the threshold.
189 static void ip_evictor(struct net *net)
193 evicted = inet_frag_evictor(&net->ipv4.frags, &ip4_frags);
195 IP_ADD_STATS_BH(IPSTATS_MIB_REASMFAILS, evicted);
199 * Oops, a fragment queue timed out. Kill it and send an ICMP reply.
201 static void ip_expire(unsigned long arg)
205 qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);
207 spin_lock(&qp->q.lock);
209 if (qp->q.last_in & COMPLETE)
214 IP_INC_STATS_BH(IPSTATS_MIB_REASMTIMEOUT);
215 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
217 if ((qp->q.last_in&FIRST_IN) && qp->q.fragments != NULL) {
218 struct sk_buff *head = qp->q.fragments;
219 /* Send an ICMP "Fragment Reassembly Timeout" message. */
220 if ((head->dev = dev_get_by_index(&init_net, qp->iif)) != NULL) {
221 icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
226 spin_unlock(&qp->q.lock);
230 /* Find the correct entry in the "incomplete datagrams" queue for
231 * this IP datagram, and create new one, if nothing is found.
233 static inline struct ipq *ip_find(struct net *net, struct iphdr *iph, u32 user)
235 struct inet_frag_queue *q;
236 struct ip4_create_arg arg;
241 hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
243 q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);
247 return container_of(q, struct ipq, q);
250 LIMIT_NETDEBUG(KERN_ERR "ip_frag_create: no memory left !\n");
254 /* Is the fragment too far ahead to be part of ipq? */
255 static inline int ip_frag_too_far(struct ipq *qp)
257 struct inet_peer *peer = qp->peer;
258 unsigned int max = sysctl_ipfrag_max_dist;
259 unsigned int start, end;
267 end = atomic_inc_return(&peer->rid);
270 rc = qp->q.fragments && (end - start) > max;
273 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
279 static int ip_frag_reinit(struct ipq *qp)
283 if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
284 atomic_inc(&qp->q.refcnt);
288 fp = qp->q.fragments;
290 struct sk_buff *xp = fp->next;
291 frag_kfree_skb(qp->q.net, fp, NULL);
298 qp->q.fragments = NULL;
304 /* Add new segment to existing queue. */
305 static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
307 struct sk_buff *prev, *next;
308 struct net_device *dev;
313 if (qp->q.last_in & COMPLETE)
316 if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
317 unlikely(ip_frag_too_far(qp)) &&
318 unlikely(err = ip_frag_reinit(qp))) {
323 offset = ntohs(ip_hdr(skb)->frag_off);
324 flags = offset & ~IP_OFFSET;
326 offset <<= 3; /* offset is in 8-byte chunks */
327 ihl = ip_hdrlen(skb);
329 /* Determine the position of this fragment. */
330 end = offset + skb->len - ihl;
333 /* Is this the final fragment? */
334 if ((flags & IP_MF) == 0) {
335 /* If we already have some bits beyond end
336 * or have different end, the segment is corrrupted.
338 if (end < qp->q.len ||
339 ((qp->q.last_in & LAST_IN) && end != qp->q.len))
341 qp->q.last_in |= LAST_IN;
346 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
347 skb->ip_summed = CHECKSUM_NONE;
349 if (end > qp->q.len) {
350 /* Some bits beyond end -> corruption. */
351 if (qp->q.last_in & LAST_IN)
360 if (pskb_pull(skb, ihl) == NULL)
363 err = pskb_trim_rcsum(skb, end - offset);
367 /* Find out which fragments are in front and at the back of us
368 * in the chain of fragments so far. We must know where to put
369 * this fragment, right?
372 for (next = qp->q.fragments; next != NULL; next = next->next) {
373 if (FRAG_CB(next)->offset >= offset)
378 /* We found where to put this one. Check for overlap with
379 * preceding fragment, and, if needed, align things so that
380 * any overlaps are eliminated.
383 int i = (FRAG_CB(prev)->offset + prev->len) - offset;
391 if (!pskb_pull(skb, i))
393 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
394 skb->ip_summed = CHECKSUM_NONE;
400 while (next && FRAG_CB(next)->offset < end) {
401 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
404 /* Eat head of the next overlapped fragment
405 * and leave the loop. The next ones cannot overlap.
407 if (!pskb_pull(next, i))
409 FRAG_CB(next)->offset += i;
411 if (next->ip_summed != CHECKSUM_UNNECESSARY)
412 next->ip_summed = CHECKSUM_NONE;
415 struct sk_buff *free_it = next;
417 /* Old fragment is completely overridden with
425 qp->q.fragments = next;
427 qp->q.meat -= free_it->len;
428 frag_kfree_skb(qp->q.net, free_it, NULL);
432 FRAG_CB(skb)->offset = offset;
434 /* Insert this fragment in the chain of fragments. */
439 qp->q.fragments = skb;
443 qp->iif = dev->ifindex;
446 qp->q.stamp = skb->tstamp;
447 qp->q.meat += skb->len;
448 atomic_add(skb->truesize, &qp->q.net->mem);
450 qp->q.last_in |= FIRST_IN;
452 if (qp->q.last_in == (FIRST_IN | LAST_IN) && qp->q.meat == qp->q.len)
453 return ip_frag_reasm(qp, prev, dev);
455 write_lock(&ip4_frags.lock);
456 list_move_tail(&qp->q.lru_list, &ip4_frags.lru_list);
457 write_unlock(&ip4_frags.lock);
466 /* Build a new IP datagram from all its fragments. */
468 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
469 struct net_device *dev)
472 struct sk_buff *fp, *head = qp->q.fragments;
479 /* Make the one we just received the head. */
482 fp = skb_clone(head, GFP_ATOMIC);
486 fp->next = head->next;
489 skb_morph(head, qp->q.fragments);
490 head->next = qp->q.fragments->next;
492 kfree_skb(qp->q.fragments);
493 qp->q.fragments = head;
496 BUG_TRAP(head != NULL);
497 BUG_TRAP(FRAG_CB(head)->offset == 0);
499 /* Allocate a new buffer for the datagram. */
500 ihlen = ip_hdrlen(head);
501 len = ihlen + qp->q.len;
507 /* Head of list must not be cloned. */
508 if (skb_cloned(head) && pskb_expand_head(head, 0, 0, GFP_ATOMIC))
511 /* If the first fragment is fragmented itself, we split
512 * it to two chunks: the first with data and paged part
513 * and the second, holding only fragments. */
514 if (skb_shinfo(head)->frag_list) {
515 struct sk_buff *clone;
518 if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
520 clone->next = head->next;
522 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
523 skb_shinfo(head)->frag_list = NULL;
524 for (i=0; i<skb_shinfo(head)->nr_frags; i++)
525 plen += skb_shinfo(head)->frags[i].size;
526 clone->len = clone->data_len = head->data_len - plen;
527 head->data_len -= clone->len;
528 head->len -= clone->len;
530 clone->ip_summed = head->ip_summed;
531 atomic_add(clone->truesize, &qp->q.net->mem);
534 skb_shinfo(head)->frag_list = head->next;
535 skb_push(head, head->data - skb_network_header(head));
536 atomic_sub(head->truesize, &qp->q.net->mem);
538 for (fp=head->next; fp; fp = fp->next) {
539 head->data_len += fp->len;
540 head->len += fp->len;
541 if (head->ip_summed != fp->ip_summed)
542 head->ip_summed = CHECKSUM_NONE;
543 else if (head->ip_summed == CHECKSUM_COMPLETE)
544 head->csum = csum_add(head->csum, fp->csum);
545 head->truesize += fp->truesize;
546 atomic_sub(fp->truesize, &qp->q.net->mem);
551 head->tstamp = qp->q.stamp;
555 iph->tot_len = htons(len);
556 IP_INC_STATS_BH(IPSTATS_MIB_REASMOKS);
557 qp->q.fragments = NULL;
561 LIMIT_NETDEBUG(KERN_ERR "IP: queue_glue: no memory for gluing "
568 "Oversized IP packet from %d.%d.%d.%d.\n",
571 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
575 /* Process an incoming IP datagram fragment. */
576 int ip_defrag(struct sk_buff *skb, u32 user)
581 IP_INC_STATS_BH(IPSTATS_MIB_REASMREQDS);
583 net = skb->dev->nd_net;
584 /* Start by cleaning up the memory. */
585 if (atomic_read(&net->ipv4.frags.mem) > ip4_frags_ctl.high_thresh)
588 /* Lookup (or create) queue header */
589 if ((qp = ip_find(net, ip_hdr(skb), user)) != NULL) {
592 spin_lock(&qp->q.lock);
594 ret = ip_frag_queue(qp, skb);
596 spin_unlock(&qp->q.lock);
601 IP_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
609 static struct ctl_table ip4_frags_ctl_table[] = {
611 .ctl_name = NET_IPV4_IPFRAG_HIGH_THRESH,
612 .procname = "ipfrag_high_thresh",
613 .data = &ip4_frags_ctl.high_thresh,
614 .maxlen = sizeof(int),
616 .proc_handler = &proc_dointvec
619 .ctl_name = NET_IPV4_IPFRAG_LOW_THRESH,
620 .procname = "ipfrag_low_thresh",
621 .data = &ip4_frags_ctl.low_thresh,
622 .maxlen = sizeof(int),
624 .proc_handler = &proc_dointvec
627 .ctl_name = NET_IPV4_IPFRAG_TIME,
628 .procname = "ipfrag_time",
629 .data = &init_net.ipv4.frags.timeout,
630 .maxlen = sizeof(int),
632 .proc_handler = &proc_dointvec_jiffies,
633 .strategy = &sysctl_jiffies
636 .ctl_name = NET_IPV4_IPFRAG_SECRET_INTERVAL,
637 .procname = "ipfrag_secret_interval",
638 .data = &ip4_frags_ctl.secret_interval,
639 .maxlen = sizeof(int),
641 .proc_handler = &proc_dointvec_jiffies,
642 .strategy = &sysctl_jiffies
645 .procname = "ipfrag_max_dist",
646 .data = &sysctl_ipfrag_max_dist,
647 .maxlen = sizeof(int),
649 .proc_handler = &proc_dointvec_minmax,
655 static int ip4_frags_ctl_register(struct net *net)
657 struct ctl_table *table;
658 struct ctl_table_header *hdr;
660 table = ip4_frags_ctl_table;
661 if (net != &init_net) {
662 table = kmemdup(table, sizeof(ip4_frags_ctl_table), GFP_KERNEL);
666 table[0].mode &= ~0222;
667 table[1].mode &= ~0222;
668 table[2].data = &net->ipv4.frags.timeout;
669 table[3].mode &= ~0222;
670 table[4].mode &= ~0222;
673 hdr = register_net_sysctl_table(net, net_ipv4_ctl_path, table);
677 net->ipv4.frags_hdr = hdr;
681 if (net != &init_net)
687 static void ip4_frags_ctl_unregister(struct net *net)
689 struct ctl_table *table;
691 table = net->ipv4.frags_hdr->ctl_table_arg;
692 unregister_net_sysctl_table(net->ipv4.frags_hdr);
696 static inline int ip4_frags_ctl_register(struct net *net)
701 static inline void ip4_frags_ctl_unregister(struct net *net)
706 static int ipv4_frags_init_net(struct net *net)
709 * Important NOTE! Fragment queue must be destroyed before MSL expires.
710 * RFC791 is wrong proposing to prolongate timer each fragment arrival
713 net->ipv4.frags.timeout = IP_FRAG_TIME;
715 inet_frags_init_net(&net->ipv4.frags);
717 return ip4_frags_ctl_register(net);
720 void __init ipfrag_init(void)
722 ipv4_frags_init_net(&init_net);
723 ip4_frags.ctl = &ip4_frags_ctl;
724 ip4_frags.hashfn = ip4_hashfn;
725 ip4_frags.constructor = ip4_frag_init;
726 ip4_frags.destructor = ip4_frag_free;
727 ip4_frags.skb_free = NULL;
728 ip4_frags.qsize = sizeof(struct ipq);
729 ip4_frags.match = ip4_frag_match;
730 ip4_frags.frag_expire = ip_expire;
731 inet_frags_init(&ip4_frags);
734 EXPORT_SYMBOL(ip_defrag);