1 // SPDX-License-Identifier: GPL-2.0
3 * INET An implementation of the TCP/IP protocol suite for the LINUX
4 * operating system. INET is implemented using the BSD Socket
5 * interface as the means of communication with the user level.
7 * The IP fragmentation functionality.
9 * Authors: Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
10 * Alan Cox <alan@lxorguk.ukuu.org.uk>
13 * Alan Cox : Split from ip.c , see ip_input.c for history.
14 * David S. Miller : Begin massive cleanup...
15 * Andi Kleen : Add sysctls.
16 * xxxx : Overlapfrag bug.
17 * Ultima : ip_expire() kernel panic.
18 * Bill Hawes : Frag accounting and evictor fixes.
19 * John McDonald : 0 length frag bug.
20 * Alexey Kuznetsov: SMP races, threading, cleanup.
21 * Patrick McHardy : LRU queue of frag heads for evictor.
24 #define pr_fmt(fmt) "IPv4: " fmt
26 #include <linux/compiler.h>
27 #include <linux/module.h>
28 #include <linux/types.h>
30 #include <linux/jiffies.h>
31 #include <linux/skbuff.h>
32 #include <linux/list.h>
34 #include <linux/icmp.h>
35 #include <linux/netdevice.h>
36 #include <linux/jhash.h>
37 #include <linux/random.h>
38 #include <linux/slab.h>
39 #include <net/route.h>
44 #include <net/checksum.h>
45 #include <net/inetpeer.h>
46 #include <net/inet_frag.h>
47 #include <linux/tcp.h>
48 #include <linux/udp.h>
49 #include <linux/inet.h>
50 #include <linux/netfilter_ipv4.h>
51 #include <net/inet_ecn.h>
52 #include <net/l3mdev.h>
54 /* NOTE. Logic of IP defragmentation is parallel to corresponding IPv6
55 * code now. If you change something here, _PLEASE_ update ipv6/reassembly.c
56 * as well. Or notify me, at least. --ANK
58 static const char ip_frag_cache_name[] = "ip4-frags";
62 struct inet_skb_parm h;
66 #define FRAG_CB(skb) ((struct ipfrag_skb_cb *)((skb)->cb))
68 /* Describe an entry in the "incomplete datagrams" queue. */
70 struct inet_frag_queue q;
77 u8 ecn; /* RFC3168 support */
78 u16 max_df_size; /* largest frag with DF set seen */
80 int vif; /* L3 master device index */
82 struct inet_peer *peer;
85 static u8 ip4_frag_ecn(u8 tos)
87 return 1 << (tos & INET_ECN_MASK);
90 static struct inet_frags ip4_frags;
92 int ip_frag_mem(struct net *net)
94 return sum_frag_mem_limit(&net->ipv4.frags);
97 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
98 struct net_device *dev);
100 struct ip4_create_arg {
106 static unsigned int ipqhashfn(__be16 id, __be32 saddr, __be32 daddr, u8 prot)
108 net_get_random_once(&ip4_frags.rnd, sizeof(ip4_frags.rnd));
109 return jhash_3words((__force u32)id << 16 | prot,
110 (__force u32)saddr, (__force u32)daddr,
114 static unsigned int ip4_hashfn(const struct inet_frag_queue *q)
116 const struct ipq *ipq;
118 ipq = container_of(q, struct ipq, q);
119 return ipqhashfn(ipq->id, ipq->saddr, ipq->daddr, ipq->protocol);
122 static bool ip4_frag_match(const struct inet_frag_queue *q, const void *a)
124 const struct ipq *qp;
125 const struct ip4_create_arg *arg = a;
127 qp = container_of(q, struct ipq, q);
128 return qp->id == arg->iph->id &&
129 qp->saddr == arg->iph->saddr &&
130 qp->daddr == arg->iph->daddr &&
131 qp->protocol == arg->iph->protocol &&
132 qp->user == arg->user &&
136 static void ip4_frag_init(struct inet_frag_queue *q, const void *a)
138 struct ipq *qp = container_of(q, struct ipq, q);
139 struct netns_ipv4 *ipv4 = container_of(q->net, struct netns_ipv4,
141 struct net *net = container_of(ipv4, struct net, ipv4);
143 const struct ip4_create_arg *arg = a;
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;
151 qp->user = arg->user;
152 qp->peer = q->net->max_dist ?
153 inet_getpeer_v4(net->ipv4.peers, arg->iph->saddr, arg->vif, 1) :
157 static void ip4_frag_free(struct inet_frag_queue *q)
161 qp = container_of(q, struct ipq, q);
163 inet_putpeer(qp->peer);
167 /* Destruction primitives. */
169 static void ipq_put(struct ipq *ipq)
171 inet_frag_put(&ipq->q, &ip4_frags);
174 /* Kill ipq entry. It is not destroyed immediately,
175 * because caller (and someone more) holds reference count.
177 static void ipq_kill(struct ipq *ipq)
179 inet_frag_kill(&ipq->q, &ip4_frags);
182 static bool frag_expire_skip_icmp(u32 user)
184 return user == IP_DEFRAG_AF_PACKET ||
185 ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_IN,
186 __IP_DEFRAG_CONNTRACK_IN_END) ||
187 ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_BRIDGE_IN,
188 __IP_DEFRAG_CONNTRACK_BRIDGE_IN);
192 * Oops, a fragment queue timed out. Kill it and send an ICMP reply.
194 static void ip_expire(unsigned long arg)
199 qp = container_of((struct inet_frag_queue *) arg, struct ipq, q);
200 net = container_of(qp->q.net, struct net, ipv4.frags);
203 spin_lock(&qp->q.lock);
205 if (qp->q.flags & INET_FRAG_COMPLETE)
209 __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
211 if (!inet_frag_evicting(&qp->q)) {
212 struct sk_buff *clone, *head = qp->q.fragments;
213 const struct iphdr *iph;
216 __IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT);
218 if (!(qp->q.flags & INET_FRAG_FIRST_IN) || !qp->q.fragments)
221 head->dev = dev_get_by_index_rcu(net, qp->iif);
226 /* skb has no dst, perform route lookup again */
228 err = ip_route_input_noref(head, iph->daddr, iph->saddr,
229 iph->tos, head->dev);
233 /* Only an end host needs to send an ICMP
234 * "Fragment Reassembly Timeout" message, per RFC792.
236 if (frag_expire_skip_icmp(qp->user) &&
237 (skb_rtable(head)->rt_type != RTN_LOCAL))
240 clone = skb_clone(head, GFP_ATOMIC);
242 /* Send an ICMP "Fragment Reassembly Timeout" message. */
244 spin_unlock(&qp->q.lock);
245 icmp_send(clone, ICMP_TIME_EXCEEDED,
246 ICMP_EXC_FRAGTIME, 0);
252 spin_unlock(&qp->q.lock);
258 /* Find the correct entry in the "incomplete datagrams" queue for
259 * this IP datagram, and create new one, if nothing is found.
261 static struct ipq *ip_find(struct net *net, struct iphdr *iph,
264 struct inet_frag_queue *q;
265 struct ip4_create_arg arg;
272 hash = ipqhashfn(iph->id, iph->saddr, iph->daddr, iph->protocol);
274 q = inet_frag_find(&net->ipv4.frags, &ip4_frags, &arg, hash);
275 if (IS_ERR_OR_NULL(q)) {
276 inet_frag_maybe_warn_overflow(q, pr_fmt());
279 return container_of(q, struct ipq, q);
282 /* Is the fragment too far ahead to be part of ipq? */
283 static int ip_frag_too_far(struct ipq *qp)
285 struct inet_peer *peer = qp->peer;
286 unsigned int max = qp->q.net->max_dist;
287 unsigned int start, end;
295 end = atomic_inc_return(&peer->rid);
298 rc = qp->q.fragments && (end - start) > max;
303 net = container_of(qp->q.net, struct net, ipv4.frags);
304 __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
310 static int ip_frag_reinit(struct ipq *qp)
313 unsigned int sum_truesize = 0;
315 if (!mod_timer(&qp->q.timer, jiffies + qp->q.net->timeout)) {
316 refcount_inc(&qp->q.refcnt);
320 fp = qp->q.fragments;
322 struct sk_buff *xp = fp->next;
324 sum_truesize += fp->truesize;
328 sub_frag_mem_limit(qp->q.net, sum_truesize);
333 qp->q.fragments = NULL;
334 qp->q.fragments_tail = NULL;
341 /* Add new segment to existing queue. */
342 static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
344 struct sk_buff *prev, *next;
345 struct net_device *dev;
346 unsigned int fragsize;
352 if (qp->q.flags & INET_FRAG_COMPLETE)
355 if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
356 unlikely(ip_frag_too_far(qp)) &&
357 unlikely(err = ip_frag_reinit(qp))) {
362 ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
363 offset = ntohs(ip_hdr(skb)->frag_off);
364 flags = offset & ~IP_OFFSET;
366 offset <<= 3; /* offset is in 8-byte chunks */
367 ihl = ip_hdrlen(skb);
369 /* Determine the position of this fragment. */
370 end = offset + skb->len - skb_network_offset(skb) - ihl;
373 /* Is this the final fragment? */
374 if ((flags & IP_MF) == 0) {
375 /* If we already have some bits beyond end
376 * or have different end, the segment is corrupted.
378 if (end < qp->q.len ||
379 ((qp->q.flags & INET_FRAG_LAST_IN) && end != qp->q.len))
381 qp->q.flags |= INET_FRAG_LAST_IN;
386 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
387 skb->ip_summed = CHECKSUM_NONE;
389 if (end > qp->q.len) {
390 /* Some bits beyond end -> corruption. */
391 if (qp->q.flags & INET_FRAG_LAST_IN)
400 if (!pskb_pull(skb, skb_network_offset(skb) + ihl))
403 err = pskb_trim_rcsum(skb, end - offset);
407 /* Find out which fragments are in front and at the back of us
408 * in the chain of fragments so far. We must know where to put
409 * this fragment, right?
411 prev = qp->q.fragments_tail;
412 if (!prev || FRAG_CB(prev)->offset < offset) {
417 for (next = qp->q.fragments; next != NULL; next = next->next) {
418 if (FRAG_CB(next)->offset >= offset)
424 /* We found where to put this one. Check for overlap with
425 * preceding fragment, and, if needed, align things so that
426 * any overlaps are eliminated.
429 int i = (FRAG_CB(prev)->offset + prev->len) - offset;
437 if (!pskb_pull(skb, i))
439 if (skb->ip_summed != CHECKSUM_UNNECESSARY)
440 skb->ip_summed = CHECKSUM_NONE;
446 while (next && FRAG_CB(next)->offset < end) {
447 int i = end - FRAG_CB(next)->offset; /* overlap is 'i' bytes */
450 /* Eat head of the next overlapped fragment
451 * and leave the loop. The next ones cannot overlap.
453 if (!pskb_pull(next, i))
455 FRAG_CB(next)->offset += i;
457 if (next->ip_summed != CHECKSUM_UNNECESSARY)
458 next->ip_summed = CHECKSUM_NONE;
461 struct sk_buff *free_it = next;
463 /* Old fragment is completely overridden with
471 qp->q.fragments = next;
473 qp->q.meat -= free_it->len;
474 sub_frag_mem_limit(qp->q.net, free_it->truesize);
479 FRAG_CB(skb)->offset = offset;
481 /* Insert this fragment in the chain of fragments. */
484 qp->q.fragments_tail = skb;
488 qp->q.fragments = skb;
492 qp->iif = dev->ifindex;
495 qp->q.stamp = skb->tstamp;
496 qp->q.meat += skb->len;
498 add_frag_mem_limit(qp->q.net, skb->truesize);
500 qp->q.flags |= INET_FRAG_FIRST_IN;
502 fragsize = skb->len + ihl;
504 if (fragsize > qp->q.max_size)
505 qp->q.max_size = fragsize;
507 if (ip_hdr(skb)->frag_off & htons(IP_DF) &&
508 fragsize > qp->max_df_size)
509 qp->max_df_size = fragsize;
511 if (qp->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
512 qp->q.meat == qp->q.len) {
513 unsigned long orefdst = skb->_skb_refdst;
515 skb->_skb_refdst = 0UL;
516 err = ip_frag_reasm(qp, prev, dev);
517 skb->_skb_refdst = orefdst;
530 /* Build a new IP datagram from all its fragments. */
532 static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
533 struct net_device *dev)
535 struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
537 struct sk_buff *fp, *head = qp->q.fragments;
545 ecn = ip_frag_ecn_table[qp->ecn];
546 if (unlikely(ecn == 0xff)) {
550 /* Make the one we just received the head. */
553 fp = skb_clone(head, GFP_ATOMIC);
557 fp->next = head->next;
559 qp->q.fragments_tail = fp;
562 skb_morph(head, qp->q.fragments);
563 head->next = qp->q.fragments->next;
565 consume_skb(qp->q.fragments);
566 qp->q.fragments = head;
570 WARN_ON(FRAG_CB(head)->offset != 0);
572 /* Allocate a new buffer for the datagram. */
573 ihlen = ip_hdrlen(head);
574 len = ihlen + qp->q.len;
580 /* Head of list must not be cloned. */
581 if (skb_unclone(head, GFP_ATOMIC))
584 /* If the first fragment is fragmented itself, we split
585 * it to two chunks: the first with data and paged part
586 * and the second, holding only fragments. */
587 if (skb_has_frag_list(head)) {
588 struct sk_buff *clone;
591 clone = alloc_skb(0, GFP_ATOMIC);
594 clone->next = head->next;
596 skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
597 skb_frag_list_init(head);
598 for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
599 plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
600 clone->len = clone->data_len = head->data_len - plen;
601 head->data_len -= clone->len;
602 head->len -= clone->len;
604 clone->ip_summed = head->ip_summed;
605 add_frag_mem_limit(qp->q.net, clone->truesize);
608 skb_shinfo(head)->frag_list = head->next;
609 skb_push(head, head->data - skb_network_header(head));
611 for (fp=head->next; fp; fp = fp->next) {
612 head->data_len += fp->len;
613 head->len += fp->len;
614 if (head->ip_summed != fp->ip_summed)
615 head->ip_summed = CHECKSUM_NONE;
616 else if (head->ip_summed == CHECKSUM_COMPLETE)
617 head->csum = csum_add(head->csum, fp->csum);
618 head->truesize += fp->truesize;
620 sub_frag_mem_limit(qp->q.net, head->truesize);
624 head->tstamp = qp->q.stamp;
625 IPCB(head)->frag_max_size = max(qp->max_df_size, qp->q.max_size);
628 iph->tot_len = htons(len);
631 /* When we set IP_DF on a refragmented skb we must also force a
632 * call to ip_fragment to avoid forwarding a DF-skb of size s while
633 * original sender only sent fragments of size f (where f < s).
635 * We only set DF/IPSKB_FRAG_PMTU if such DF fragment was the largest
636 * frag seen to avoid sending tiny DF-fragments in case skb was built
637 * from one very small df-fragment and one large non-df frag.
639 if (qp->max_df_size == qp->q.max_size) {
640 IPCB(head)->flags |= IPSKB_FRAG_PMTU;
641 iph->frag_off = htons(IP_DF);
648 __IP_INC_STATS(net, IPSTATS_MIB_REASMOKS);
649 qp->q.fragments = NULL;
650 qp->q.fragments_tail = NULL;
654 net_dbg_ratelimited("queue_glue: no memory for gluing queue %p\n", qp);
658 net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->saddr);
660 __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
664 /* Process an incoming IP datagram fragment. */
665 int ip_defrag(struct net *net, struct sk_buff *skb, u32 user)
667 struct net_device *dev = skb->dev ? : skb_dst(skb)->dev;
668 int vif = l3mdev_master_ifindex_rcu(dev);
671 __IP_INC_STATS(net, IPSTATS_MIB_REASMREQDS);
674 /* Lookup (or create) queue header */
675 qp = ip_find(net, ip_hdr(skb), user, vif);
679 spin_lock(&qp->q.lock);
681 ret = ip_frag_queue(qp, skb);
683 spin_unlock(&qp->q.lock);
688 __IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
692 EXPORT_SYMBOL(ip_defrag);
694 struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user)
700 if (skb->protocol != htons(ETH_P_IP))
703 netoff = skb_network_offset(skb);
705 if (skb_copy_bits(skb, netoff, &iph, sizeof(iph)) < 0)
708 if (iph.ihl < 5 || iph.version != 4)
711 len = ntohs(iph.tot_len);
712 if (skb->len < netoff + len || len < (iph.ihl * 4))
715 if (ip_is_fragment(&iph)) {
716 skb = skb_share_check(skb, GFP_ATOMIC);
718 if (!pskb_may_pull(skb, netoff + iph.ihl * 4))
720 if (pskb_trim_rcsum(skb, netoff + len))
722 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
723 if (ip_defrag(net, skb, user))
730 EXPORT_SYMBOL(ip_check_defrag);
735 static struct ctl_table ip4_frags_ns_ctl_table[] = {
737 .procname = "ipfrag_high_thresh",
738 .data = &init_net.ipv4.frags.high_thresh,
739 .maxlen = sizeof(int),
741 .proc_handler = proc_dointvec_minmax,
742 .extra1 = &init_net.ipv4.frags.low_thresh
745 .procname = "ipfrag_low_thresh",
746 .data = &init_net.ipv4.frags.low_thresh,
747 .maxlen = sizeof(int),
749 .proc_handler = proc_dointvec_minmax,
751 .extra2 = &init_net.ipv4.frags.high_thresh
754 .procname = "ipfrag_time",
755 .data = &init_net.ipv4.frags.timeout,
756 .maxlen = sizeof(int),
758 .proc_handler = proc_dointvec_jiffies,
761 .procname = "ipfrag_max_dist",
762 .data = &init_net.ipv4.frags.max_dist,
763 .maxlen = sizeof(int),
765 .proc_handler = proc_dointvec_minmax,
771 /* secret interval has been deprecated */
772 static int ip4_frags_secret_interval_unused;
773 static struct ctl_table ip4_frags_ctl_table[] = {
775 .procname = "ipfrag_secret_interval",
776 .data = &ip4_frags_secret_interval_unused,
777 .maxlen = sizeof(int),
779 .proc_handler = proc_dointvec_jiffies,
784 static int __net_init ip4_frags_ns_ctl_register(struct net *net)
786 struct ctl_table *table;
787 struct ctl_table_header *hdr;
789 table = ip4_frags_ns_ctl_table;
790 if (!net_eq(net, &init_net)) {
791 table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
795 table[0].data = &net->ipv4.frags.high_thresh;
796 table[0].extra1 = &net->ipv4.frags.low_thresh;
797 table[0].extra2 = &init_net.ipv4.frags.high_thresh;
798 table[1].data = &net->ipv4.frags.low_thresh;
799 table[1].extra2 = &net->ipv4.frags.high_thresh;
800 table[2].data = &net->ipv4.frags.timeout;
801 table[3].data = &net->ipv4.frags.max_dist;
804 hdr = register_net_sysctl(net, "net/ipv4", table);
808 net->ipv4.frags_hdr = hdr;
812 if (!net_eq(net, &init_net))
818 static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
820 struct ctl_table *table;
822 table = net->ipv4.frags_hdr->ctl_table_arg;
823 unregister_net_sysctl_table(net->ipv4.frags_hdr);
827 static void __init ip4_frags_ctl_register(void)
829 register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
832 static int ip4_frags_ns_ctl_register(struct net *net)
837 static void ip4_frags_ns_ctl_unregister(struct net *net)
841 static void __init ip4_frags_ctl_register(void)
846 static int __net_init ipv4_frags_init_net(struct net *net)
848 /* Fragment cache limits.
850 * The fragment memory accounting code, (tries to) account for
851 * the real memory usage, by measuring both the size of frag
852 * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue))
853 * and the SKB's truesize.
855 * A 64K fragment consumes 129736 bytes (44*2944)+200
856 * (1500 truesize == 2944, sizeof(struct ipq) == 200)
858 * We will commit 4MB at one time. Should we cross that limit
859 * we will prune down to 3MB, making room for approx 8 big 64K
862 net->ipv4.frags.high_thresh = 4 * 1024 * 1024;
863 net->ipv4.frags.low_thresh = 3 * 1024 * 1024;
865 * Important NOTE! Fragment queue must be destroyed before MSL expires.
866 * RFC791 is wrong proposing to prolongate timer each fragment arrival
869 net->ipv4.frags.timeout = IP_FRAG_TIME;
871 net->ipv4.frags.max_dist = 64;
873 inet_frags_init_net(&net->ipv4.frags);
875 return ip4_frags_ns_ctl_register(net);
878 static void __net_exit ipv4_frags_exit_net(struct net *net)
880 ip4_frags_ns_ctl_unregister(net);
881 inet_frags_exit_net(&net->ipv4.frags, &ip4_frags);
884 static struct pernet_operations ip4_frags_ops = {
885 .init = ipv4_frags_init_net,
886 .exit = ipv4_frags_exit_net,
889 void __init ipfrag_init(void)
891 ip4_frags_ctl_register();
892 register_pernet_subsys(&ip4_frags_ops);
893 ip4_frags.hashfn = ip4_hashfn;
894 ip4_frags.constructor = ip4_frag_init;
895 ip4_frags.destructor = ip4_frag_free;
896 ip4_frags.qsize = sizeof(struct ipq);
897 ip4_frags.match = ip4_frag_match;
898 ip4_frags.frag_expire = ip_expire;
899 ip4_frags.frags_cache_name = ip_frag_cache_name;
900 if (inet_frags_init(&ip4_frags))
901 panic("IP: failed to allocate ip4_frags cache\n");