cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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ip_fragment.c (18102B)


      1// SPDX-License-Identifier: GPL-2.0
      2/*
      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.
      6 *
      7 *		The IP fragmentation functionality.
      8 *
      9 * Authors:	Fred N. van Kempen <waltje@uWalt.NL.Mugnet.ORG>
     10 *		Alan Cox <alan@lxorguk.ukuu.org.uk>
     11 *
     12 * Fixes:
     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.
     22 */
     23
     24#define pr_fmt(fmt) "IPv4: " fmt
     25
     26#include <linux/compiler.h>
     27#include <linux/module.h>
     28#include <linux/types.h>
     29#include <linux/mm.h>
     30#include <linux/jiffies.h>
     31#include <linux/skbuff.h>
     32#include <linux/list.h>
     33#include <linux/ip.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>
     40#include <net/dst.h>
     41#include <net/sock.h>
     42#include <net/ip.h>
     43#include <net/icmp.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>
     53
     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
     57 */
     58static const char ip_frag_cache_name[] = "ip4-frags";
     59
     60/* Describe an entry in the "incomplete datagrams" queue. */
     61struct ipq {
     62	struct inet_frag_queue q;
     63
     64	u8		ecn; /* RFC3168 support */
     65	u16		max_df_size; /* largest frag with DF set seen */
     66	int             iif;
     67	unsigned int    rid;
     68	struct inet_peer *peer;
     69};
     70
     71static u8 ip4_frag_ecn(u8 tos)
     72{
     73	return 1 << (tos & INET_ECN_MASK);
     74}
     75
     76static struct inet_frags ip4_frags;
     77
     78static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
     79			 struct sk_buff *prev_tail, struct net_device *dev);
     80
     81
     82static void ip4_frag_init(struct inet_frag_queue *q, const void *a)
     83{
     84	struct ipq *qp = container_of(q, struct ipq, q);
     85	struct net *net = q->fqdir->net;
     86
     87	const struct frag_v4_compare_key *key = a;
     88
     89	q->key.v4 = *key;
     90	qp->ecn = 0;
     91	qp->peer = q->fqdir->max_dist ?
     92		inet_getpeer_v4(net->ipv4.peers, key->saddr, key->vif, 1) :
     93		NULL;
     94}
     95
     96static void ip4_frag_free(struct inet_frag_queue *q)
     97{
     98	struct ipq *qp;
     99
    100	qp = container_of(q, struct ipq, q);
    101	if (qp->peer)
    102		inet_putpeer(qp->peer);
    103}
    104
    105
    106/* Destruction primitives. */
    107
    108static void ipq_put(struct ipq *ipq)
    109{
    110	inet_frag_put(&ipq->q);
    111}
    112
    113/* Kill ipq entry. It is not destroyed immediately,
    114 * because caller (and someone more) holds reference count.
    115 */
    116static void ipq_kill(struct ipq *ipq)
    117{
    118	inet_frag_kill(&ipq->q);
    119}
    120
    121static bool frag_expire_skip_icmp(u32 user)
    122{
    123	return user == IP_DEFRAG_AF_PACKET ||
    124	       ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_IN,
    125					 __IP_DEFRAG_CONNTRACK_IN_END) ||
    126	       ip_defrag_user_in_between(user, IP_DEFRAG_CONNTRACK_BRIDGE_IN,
    127					 __IP_DEFRAG_CONNTRACK_BRIDGE_IN);
    128}
    129
    130/*
    131 * Oops, a fragment queue timed out.  Kill it and send an ICMP reply.
    132 */
    133static void ip_expire(struct timer_list *t)
    134{
    135	struct inet_frag_queue *frag = from_timer(frag, t, timer);
    136	const struct iphdr *iph;
    137	struct sk_buff *head = NULL;
    138	struct net *net;
    139	struct ipq *qp;
    140	int err;
    141
    142	qp = container_of(frag, struct ipq, q);
    143	net = qp->q.fqdir->net;
    144
    145	rcu_read_lock();
    146
    147	/* Paired with WRITE_ONCE() in fqdir_pre_exit(). */
    148	if (READ_ONCE(qp->q.fqdir->dead))
    149		goto out_rcu_unlock;
    150
    151	spin_lock(&qp->q.lock);
    152
    153	if (qp->q.flags & INET_FRAG_COMPLETE)
    154		goto out;
    155
    156	ipq_kill(qp);
    157	__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
    158	__IP_INC_STATS(net, IPSTATS_MIB_REASMTIMEOUT);
    159
    160	if (!(qp->q.flags & INET_FRAG_FIRST_IN))
    161		goto out;
    162
    163	/* sk_buff::dev and sk_buff::rbnode are unionized. So we
    164	 * pull the head out of the tree in order to be able to
    165	 * deal with head->dev.
    166	 */
    167	head = inet_frag_pull_head(&qp->q);
    168	if (!head)
    169		goto out;
    170	head->dev = dev_get_by_index_rcu(net, qp->iif);
    171	if (!head->dev)
    172		goto out;
    173
    174
    175	/* skb has no dst, perform route lookup again */
    176	iph = ip_hdr(head);
    177	err = ip_route_input_noref(head, iph->daddr, iph->saddr,
    178					   iph->tos, head->dev);
    179	if (err)
    180		goto out;
    181
    182	/* Only an end host needs to send an ICMP
    183	 * "Fragment Reassembly Timeout" message, per RFC792.
    184	 */
    185	if (frag_expire_skip_icmp(qp->q.key.v4.user) &&
    186	    (skb_rtable(head)->rt_type != RTN_LOCAL))
    187		goto out;
    188
    189	spin_unlock(&qp->q.lock);
    190	icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
    191	goto out_rcu_unlock;
    192
    193out:
    194	spin_unlock(&qp->q.lock);
    195out_rcu_unlock:
    196	rcu_read_unlock();
    197	kfree_skb(head);
    198	ipq_put(qp);
    199}
    200
    201/* Find the correct entry in the "incomplete datagrams" queue for
    202 * this IP datagram, and create new one, if nothing is found.
    203 */
    204static struct ipq *ip_find(struct net *net, struct iphdr *iph,
    205			   u32 user, int vif)
    206{
    207	struct frag_v4_compare_key key = {
    208		.saddr = iph->saddr,
    209		.daddr = iph->daddr,
    210		.user = user,
    211		.vif = vif,
    212		.id = iph->id,
    213		.protocol = iph->protocol,
    214	};
    215	struct inet_frag_queue *q;
    216
    217	q = inet_frag_find(net->ipv4.fqdir, &key);
    218	if (!q)
    219		return NULL;
    220
    221	return container_of(q, struct ipq, q);
    222}
    223
    224/* Is the fragment too far ahead to be part of ipq? */
    225static int ip_frag_too_far(struct ipq *qp)
    226{
    227	struct inet_peer *peer = qp->peer;
    228	unsigned int max = qp->q.fqdir->max_dist;
    229	unsigned int start, end;
    230
    231	int rc;
    232
    233	if (!peer || !max)
    234		return 0;
    235
    236	start = qp->rid;
    237	end = atomic_inc_return(&peer->rid);
    238	qp->rid = end;
    239
    240	rc = qp->q.fragments_tail && (end - start) > max;
    241
    242	if (rc)
    243		__IP_INC_STATS(qp->q.fqdir->net, IPSTATS_MIB_REASMFAILS);
    244
    245	return rc;
    246}
    247
    248static int ip_frag_reinit(struct ipq *qp)
    249{
    250	unsigned int sum_truesize = 0;
    251
    252	if (!mod_timer(&qp->q.timer, jiffies + qp->q.fqdir->timeout)) {
    253		refcount_inc(&qp->q.refcnt);
    254		return -ETIMEDOUT;
    255	}
    256
    257	sum_truesize = inet_frag_rbtree_purge(&qp->q.rb_fragments);
    258	sub_frag_mem_limit(qp->q.fqdir, sum_truesize);
    259
    260	qp->q.flags = 0;
    261	qp->q.len = 0;
    262	qp->q.meat = 0;
    263	qp->q.rb_fragments = RB_ROOT;
    264	qp->q.fragments_tail = NULL;
    265	qp->q.last_run_head = NULL;
    266	qp->iif = 0;
    267	qp->ecn = 0;
    268
    269	return 0;
    270}
    271
    272/* Add new segment to existing queue. */
    273static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb)
    274{
    275	struct net *net = qp->q.fqdir->net;
    276	int ihl, end, flags, offset;
    277	struct sk_buff *prev_tail;
    278	struct net_device *dev;
    279	unsigned int fragsize;
    280	int err = -ENOENT;
    281	u8 ecn;
    282
    283	if (qp->q.flags & INET_FRAG_COMPLETE)
    284		goto err;
    285
    286	if (!(IPCB(skb)->flags & IPSKB_FRAG_COMPLETE) &&
    287	    unlikely(ip_frag_too_far(qp)) &&
    288	    unlikely(err = ip_frag_reinit(qp))) {
    289		ipq_kill(qp);
    290		goto err;
    291	}
    292
    293	ecn = ip4_frag_ecn(ip_hdr(skb)->tos);
    294	offset = ntohs(ip_hdr(skb)->frag_off);
    295	flags = offset & ~IP_OFFSET;
    296	offset &= IP_OFFSET;
    297	offset <<= 3;		/* offset is in 8-byte chunks */
    298	ihl = ip_hdrlen(skb);
    299
    300	/* Determine the position of this fragment. */
    301	end = offset + skb->len - skb_network_offset(skb) - ihl;
    302	err = -EINVAL;
    303
    304	/* Is this the final fragment? */
    305	if ((flags & IP_MF) == 0) {
    306		/* If we already have some bits beyond end
    307		 * or have different end, the segment is corrupted.
    308		 */
    309		if (end < qp->q.len ||
    310		    ((qp->q.flags & INET_FRAG_LAST_IN) && end != qp->q.len))
    311			goto discard_qp;
    312		qp->q.flags |= INET_FRAG_LAST_IN;
    313		qp->q.len = end;
    314	} else {
    315		if (end&7) {
    316			end &= ~7;
    317			if (skb->ip_summed != CHECKSUM_UNNECESSARY)
    318				skb->ip_summed = CHECKSUM_NONE;
    319		}
    320		if (end > qp->q.len) {
    321			/* Some bits beyond end -> corruption. */
    322			if (qp->q.flags & INET_FRAG_LAST_IN)
    323				goto discard_qp;
    324			qp->q.len = end;
    325		}
    326	}
    327	if (end == offset)
    328		goto discard_qp;
    329
    330	err = -ENOMEM;
    331	if (!pskb_pull(skb, skb_network_offset(skb) + ihl))
    332		goto discard_qp;
    333
    334	err = pskb_trim_rcsum(skb, end - offset);
    335	if (err)
    336		goto discard_qp;
    337
    338	/* Note : skb->rbnode and skb->dev share the same location. */
    339	dev = skb->dev;
    340	/* Makes sure compiler wont do silly aliasing games */
    341	barrier();
    342
    343	prev_tail = qp->q.fragments_tail;
    344	err = inet_frag_queue_insert(&qp->q, skb, offset, end);
    345	if (err)
    346		goto insert_error;
    347
    348	if (dev)
    349		qp->iif = dev->ifindex;
    350
    351	qp->q.stamp = skb->tstamp;
    352	qp->q.mono_delivery_time = skb->mono_delivery_time;
    353	qp->q.meat += skb->len;
    354	qp->ecn |= ecn;
    355	add_frag_mem_limit(qp->q.fqdir, skb->truesize);
    356	if (offset == 0)
    357		qp->q.flags |= INET_FRAG_FIRST_IN;
    358
    359	fragsize = skb->len + ihl;
    360
    361	if (fragsize > qp->q.max_size)
    362		qp->q.max_size = fragsize;
    363
    364	if (ip_hdr(skb)->frag_off & htons(IP_DF) &&
    365	    fragsize > qp->max_df_size)
    366		qp->max_df_size = fragsize;
    367
    368	if (qp->q.flags == (INET_FRAG_FIRST_IN | INET_FRAG_LAST_IN) &&
    369	    qp->q.meat == qp->q.len) {
    370		unsigned long orefdst = skb->_skb_refdst;
    371
    372		skb->_skb_refdst = 0UL;
    373		err = ip_frag_reasm(qp, skb, prev_tail, dev);
    374		skb->_skb_refdst = orefdst;
    375		if (err)
    376			inet_frag_kill(&qp->q);
    377		return err;
    378	}
    379
    380	skb_dst_drop(skb);
    381	return -EINPROGRESS;
    382
    383insert_error:
    384	if (err == IPFRAG_DUP) {
    385		kfree_skb(skb);
    386		return -EINVAL;
    387	}
    388	err = -EINVAL;
    389	__IP_INC_STATS(net, IPSTATS_MIB_REASM_OVERLAPS);
    390discard_qp:
    391	inet_frag_kill(&qp->q);
    392	__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
    393err:
    394	kfree_skb(skb);
    395	return err;
    396}
    397
    398static bool ip_frag_coalesce_ok(const struct ipq *qp)
    399{
    400	return qp->q.key.v4.user == IP_DEFRAG_LOCAL_DELIVER;
    401}
    402
    403/* Build a new IP datagram from all its fragments. */
    404static int ip_frag_reasm(struct ipq *qp, struct sk_buff *skb,
    405			 struct sk_buff *prev_tail, struct net_device *dev)
    406{
    407	struct net *net = qp->q.fqdir->net;
    408	struct iphdr *iph;
    409	void *reasm_data;
    410	int len, err;
    411	u8 ecn;
    412
    413	ipq_kill(qp);
    414
    415	ecn = ip_frag_ecn_table[qp->ecn];
    416	if (unlikely(ecn == 0xff)) {
    417		err = -EINVAL;
    418		goto out_fail;
    419	}
    420
    421	/* Make the one we just received the head. */
    422	reasm_data = inet_frag_reasm_prepare(&qp->q, skb, prev_tail);
    423	if (!reasm_data)
    424		goto out_nomem;
    425
    426	len = ip_hdrlen(skb) + qp->q.len;
    427	err = -E2BIG;
    428	if (len > 65535)
    429		goto out_oversize;
    430
    431	inet_frag_reasm_finish(&qp->q, skb, reasm_data,
    432			       ip_frag_coalesce_ok(qp));
    433
    434	skb->dev = dev;
    435	IPCB(skb)->frag_max_size = max(qp->max_df_size, qp->q.max_size);
    436
    437	iph = ip_hdr(skb);
    438	iph->tot_len = htons(len);
    439	iph->tos |= ecn;
    440
    441	/* When we set IP_DF on a refragmented skb we must also force a
    442	 * call to ip_fragment to avoid forwarding a DF-skb of size s while
    443	 * original sender only sent fragments of size f (where f < s).
    444	 *
    445	 * We only set DF/IPSKB_FRAG_PMTU if such DF fragment was the largest
    446	 * frag seen to avoid sending tiny DF-fragments in case skb was built
    447	 * from one very small df-fragment and one large non-df frag.
    448	 */
    449	if (qp->max_df_size == qp->q.max_size) {
    450		IPCB(skb)->flags |= IPSKB_FRAG_PMTU;
    451		iph->frag_off = htons(IP_DF);
    452	} else {
    453		iph->frag_off = 0;
    454	}
    455
    456	ip_send_check(iph);
    457
    458	__IP_INC_STATS(net, IPSTATS_MIB_REASMOKS);
    459	qp->q.rb_fragments = RB_ROOT;
    460	qp->q.fragments_tail = NULL;
    461	qp->q.last_run_head = NULL;
    462	return 0;
    463
    464out_nomem:
    465	net_dbg_ratelimited("queue_glue: no memory for gluing queue %p\n", qp);
    466	err = -ENOMEM;
    467	goto out_fail;
    468out_oversize:
    469	net_info_ratelimited("Oversized IP packet from %pI4\n", &qp->q.key.v4.saddr);
    470out_fail:
    471	__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
    472	return err;
    473}
    474
    475/* Process an incoming IP datagram fragment. */
    476int ip_defrag(struct net *net, struct sk_buff *skb, u32 user)
    477{
    478	struct net_device *dev = skb->dev ? : skb_dst(skb)->dev;
    479	int vif = l3mdev_master_ifindex_rcu(dev);
    480	struct ipq *qp;
    481
    482	__IP_INC_STATS(net, IPSTATS_MIB_REASMREQDS);
    483	skb_orphan(skb);
    484
    485	/* Lookup (or create) queue header */
    486	qp = ip_find(net, ip_hdr(skb), user, vif);
    487	if (qp) {
    488		int ret;
    489
    490		spin_lock(&qp->q.lock);
    491
    492		ret = ip_frag_queue(qp, skb);
    493
    494		spin_unlock(&qp->q.lock);
    495		ipq_put(qp);
    496		return ret;
    497	}
    498
    499	__IP_INC_STATS(net, IPSTATS_MIB_REASMFAILS);
    500	kfree_skb(skb);
    501	return -ENOMEM;
    502}
    503EXPORT_SYMBOL(ip_defrag);
    504
    505struct sk_buff *ip_check_defrag(struct net *net, struct sk_buff *skb, u32 user)
    506{
    507	struct iphdr iph;
    508	int netoff;
    509	u32 len;
    510
    511	if (skb->protocol != htons(ETH_P_IP))
    512		return skb;
    513
    514	netoff = skb_network_offset(skb);
    515
    516	if (skb_copy_bits(skb, netoff, &iph, sizeof(iph)) < 0)
    517		return skb;
    518
    519	if (iph.ihl < 5 || iph.version != 4)
    520		return skb;
    521
    522	len = ntohs(iph.tot_len);
    523	if (skb->len < netoff + len || len < (iph.ihl * 4))
    524		return skb;
    525
    526	if (ip_is_fragment(&iph)) {
    527		skb = skb_share_check(skb, GFP_ATOMIC);
    528		if (skb) {
    529			if (!pskb_may_pull(skb, netoff + iph.ihl * 4)) {
    530				kfree_skb(skb);
    531				return NULL;
    532			}
    533			if (pskb_trim_rcsum(skb, netoff + len)) {
    534				kfree_skb(skb);
    535				return NULL;
    536			}
    537			memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
    538			if (ip_defrag(net, skb, user))
    539				return NULL;
    540			skb_clear_hash(skb);
    541		}
    542	}
    543	return skb;
    544}
    545EXPORT_SYMBOL(ip_check_defrag);
    546
    547#ifdef CONFIG_SYSCTL
    548static int dist_min;
    549
    550static struct ctl_table ip4_frags_ns_ctl_table[] = {
    551	{
    552		.procname	= "ipfrag_high_thresh",
    553		.maxlen		= sizeof(unsigned long),
    554		.mode		= 0644,
    555		.proc_handler	= proc_doulongvec_minmax,
    556	},
    557	{
    558		.procname	= "ipfrag_low_thresh",
    559		.maxlen		= sizeof(unsigned long),
    560		.mode		= 0644,
    561		.proc_handler	= proc_doulongvec_minmax,
    562	},
    563	{
    564		.procname	= "ipfrag_time",
    565		.maxlen		= sizeof(int),
    566		.mode		= 0644,
    567		.proc_handler	= proc_dointvec_jiffies,
    568	},
    569	{
    570		.procname	= "ipfrag_max_dist",
    571		.maxlen		= sizeof(int),
    572		.mode		= 0644,
    573		.proc_handler	= proc_dointvec_minmax,
    574		.extra1		= &dist_min,
    575	},
    576	{ }
    577};
    578
    579/* secret interval has been deprecated */
    580static int ip4_frags_secret_interval_unused;
    581static struct ctl_table ip4_frags_ctl_table[] = {
    582	{
    583		.procname	= "ipfrag_secret_interval",
    584		.data		= &ip4_frags_secret_interval_unused,
    585		.maxlen		= sizeof(int),
    586		.mode		= 0644,
    587		.proc_handler	= proc_dointvec_jiffies,
    588	},
    589	{ }
    590};
    591
    592static int __net_init ip4_frags_ns_ctl_register(struct net *net)
    593{
    594	struct ctl_table *table;
    595	struct ctl_table_header *hdr;
    596
    597	table = ip4_frags_ns_ctl_table;
    598	if (!net_eq(net, &init_net)) {
    599		table = kmemdup(table, sizeof(ip4_frags_ns_ctl_table), GFP_KERNEL);
    600		if (!table)
    601			goto err_alloc;
    602
    603	}
    604	table[0].data	= &net->ipv4.fqdir->high_thresh;
    605	table[0].extra1	= &net->ipv4.fqdir->low_thresh;
    606	table[1].data	= &net->ipv4.fqdir->low_thresh;
    607	table[1].extra2	= &net->ipv4.fqdir->high_thresh;
    608	table[2].data	= &net->ipv4.fqdir->timeout;
    609	table[3].data	= &net->ipv4.fqdir->max_dist;
    610
    611	hdr = register_net_sysctl(net, "net/ipv4", table);
    612	if (!hdr)
    613		goto err_reg;
    614
    615	net->ipv4.frags_hdr = hdr;
    616	return 0;
    617
    618err_reg:
    619	if (!net_eq(net, &init_net))
    620		kfree(table);
    621err_alloc:
    622	return -ENOMEM;
    623}
    624
    625static void __net_exit ip4_frags_ns_ctl_unregister(struct net *net)
    626{
    627	struct ctl_table *table;
    628
    629	table = net->ipv4.frags_hdr->ctl_table_arg;
    630	unregister_net_sysctl_table(net->ipv4.frags_hdr);
    631	kfree(table);
    632}
    633
    634static void __init ip4_frags_ctl_register(void)
    635{
    636	register_net_sysctl(&init_net, "net/ipv4", ip4_frags_ctl_table);
    637}
    638#else
    639static int ip4_frags_ns_ctl_register(struct net *net)
    640{
    641	return 0;
    642}
    643
    644static void ip4_frags_ns_ctl_unregister(struct net *net)
    645{
    646}
    647
    648static void __init ip4_frags_ctl_register(void)
    649{
    650}
    651#endif
    652
    653static int __net_init ipv4_frags_init_net(struct net *net)
    654{
    655	int res;
    656
    657	res = fqdir_init(&net->ipv4.fqdir, &ip4_frags, net);
    658	if (res < 0)
    659		return res;
    660	/* Fragment cache limits.
    661	 *
    662	 * The fragment memory accounting code, (tries to) account for
    663	 * the real memory usage, by measuring both the size of frag
    664	 * queue struct (inet_frag_queue (ipv4:ipq/ipv6:frag_queue))
    665	 * and the SKB's truesize.
    666	 *
    667	 * A 64K fragment consumes 129736 bytes (44*2944)+200
    668	 * (1500 truesize == 2944, sizeof(struct ipq) == 200)
    669	 *
    670	 * We will commit 4MB at one time. Should we cross that limit
    671	 * we will prune down to 3MB, making room for approx 8 big 64K
    672	 * fragments 8x128k.
    673	 */
    674	net->ipv4.fqdir->high_thresh = 4 * 1024 * 1024;
    675	net->ipv4.fqdir->low_thresh  = 3 * 1024 * 1024;
    676	/*
    677	 * Important NOTE! Fragment queue must be destroyed before MSL expires.
    678	 * RFC791 is wrong proposing to prolongate timer each fragment arrival
    679	 * by TTL.
    680	 */
    681	net->ipv4.fqdir->timeout = IP_FRAG_TIME;
    682
    683	net->ipv4.fqdir->max_dist = 64;
    684
    685	res = ip4_frags_ns_ctl_register(net);
    686	if (res < 0)
    687		fqdir_exit(net->ipv4.fqdir);
    688	return res;
    689}
    690
    691static void __net_exit ipv4_frags_pre_exit_net(struct net *net)
    692{
    693	fqdir_pre_exit(net->ipv4.fqdir);
    694}
    695
    696static void __net_exit ipv4_frags_exit_net(struct net *net)
    697{
    698	ip4_frags_ns_ctl_unregister(net);
    699	fqdir_exit(net->ipv4.fqdir);
    700}
    701
    702static struct pernet_operations ip4_frags_ops = {
    703	.init		= ipv4_frags_init_net,
    704	.pre_exit	= ipv4_frags_pre_exit_net,
    705	.exit		= ipv4_frags_exit_net,
    706};
    707
    708
    709static u32 ip4_key_hashfn(const void *data, u32 len, u32 seed)
    710{
    711	return jhash2(data,
    712		      sizeof(struct frag_v4_compare_key) / sizeof(u32), seed);
    713}
    714
    715static u32 ip4_obj_hashfn(const void *data, u32 len, u32 seed)
    716{
    717	const struct inet_frag_queue *fq = data;
    718
    719	return jhash2((const u32 *)&fq->key.v4,
    720		      sizeof(struct frag_v4_compare_key) / sizeof(u32), seed);
    721}
    722
    723static int ip4_obj_cmpfn(struct rhashtable_compare_arg *arg, const void *ptr)
    724{
    725	const struct frag_v4_compare_key *key = arg->key;
    726	const struct inet_frag_queue *fq = ptr;
    727
    728	return !!memcmp(&fq->key, key, sizeof(*key));
    729}
    730
    731static const struct rhashtable_params ip4_rhash_params = {
    732	.head_offset		= offsetof(struct inet_frag_queue, node),
    733	.key_offset		= offsetof(struct inet_frag_queue, key),
    734	.key_len		= sizeof(struct frag_v4_compare_key),
    735	.hashfn			= ip4_key_hashfn,
    736	.obj_hashfn		= ip4_obj_hashfn,
    737	.obj_cmpfn		= ip4_obj_cmpfn,
    738	.automatic_shrinking	= true,
    739};
    740
    741void __init ipfrag_init(void)
    742{
    743	ip4_frags.constructor = ip4_frag_init;
    744	ip4_frags.destructor = ip4_frag_free;
    745	ip4_frags.qsize = sizeof(struct ipq);
    746	ip4_frags.frag_expire = ip_expire;
    747	ip4_frags.frags_cache_name = ip_frag_cache_name;
    748	ip4_frags.rhash_params = ip4_rhash_params;
    749	if (inet_frags_init(&ip4_frags))
    750		panic("IP: failed to allocate ip4_frags cache\n");
    751	ip4_frags_ctl_register();
    752	register_pernet_subsys(&ip4_frags_ops);
    753}