[net-next-2.6.git] / net / ipv4 / inet_timewait_sock.c

/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Generic TIME_WAIT sockets functions
 *
 *		From code orinally in TCP
 */

#include <linux/config.h>

#include <net/inet_hashtables.h>
#include <net/inet_timewait_sock.h>
#include <net/ip.h>

/* Must be called with locally disabled BHs. */
void __inet_twsk_kill(struct inet_timewait_sock *tw, struct inet_hashinfo *hashinfo)
{
	struct inet_bind_hashbucket *bhead;
	struct inet_bind_bucket *tb;
	/* Unlink from established hashes. */
	struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, tw->tw_hash);

	write_lock(&ehead->lock);
	if (hlist_unhashed(&tw->tw_node)) {
		write_unlock(&ehead->lock);
		return;
	}
	__hlist_del(&tw->tw_node);
	sk_node_init(&tw->tw_node);
	write_unlock(&ehead->lock);

	/* Disassociate with bind bucket. */
	bhead = &hashinfo->bhash[inet_bhashfn(tw->tw_num, hashinfo->bhash_size)];
	spin_lock(&bhead->lock);
	tb = tw->tw_tb;
	__hlist_del(&tw->tw_bind_node);
	tw->tw_tb = NULL;
	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
	spin_unlock(&bhead->lock);
#ifdef SOCK_REFCNT_DEBUG
	if (atomic_read(&tw->tw_refcnt) != 1) {
		printk(KERN_DEBUG "%s timewait_sock %p refcnt=%d\n",
		       tw->tw_prot->name, tw, atomic_read(&tw->tw_refcnt));
	}
#endif
	inet_twsk_put(tw);
}

EXPORT_SYMBOL_GPL(__inet_twsk_kill);

/*
 * Enter the time wait state. This is called with locally disabled BH.
 * Essentially we whip up a timewait bucket, copy the relevant info into it
 * from the SK, and mess with hash chains and list linkage.
 */
void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
			   struct inet_hashinfo *hashinfo)
{
	const struct inet_sock *inet = inet_sk(sk);
	const struct inet_connection_sock *icsk = inet_csk(sk);
	struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
	struct inet_bind_hashbucket *bhead;
	/* Step 1: Put TW into bind hash. Original socket stays there too.
	   Note, that any socket with inet->num != 0 MUST be bound in
	   binding cache, even if it is closed.
	 */
	bhead = &hashinfo->bhash[inet_bhashfn(inet->num, hashinfo->bhash_size)];
	spin_lock(&bhead->lock);
	tw->tw_tb = icsk->icsk_bind_hash;
	BUG_TRAP(icsk->icsk_bind_hash);
	inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
	spin_unlock(&bhead->lock);

	write_lock(&ehead->lock);

	/* Step 2: Remove SK from established hash. */
	if (__sk_del_node_init(sk))
		sock_prot_dec_use(sk->sk_prot);

	/* Step 3: Hash TW into TIMEWAIT half of established hash table. */
	inet_twsk_add_node(tw, &(ehead + hashinfo->ehash_size)->chain);
	atomic_inc(&tw->tw_refcnt);

	write_unlock(&ehead->lock);
}

EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);

struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, const int state)
{
	struct inet_timewait_sock *tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_slab,
							 SLAB_ATOMIC);
	if (tw != NULL) {
		const struct inet_sock *inet = inet_sk(sk);

		/* Give us an identity. */
		tw->tw_daddr	    = inet->daddr;
		tw->tw_rcv_saddr    = inet->rcv_saddr;
		tw->tw_bound_dev_if = sk->sk_bound_dev_if;
		tw->tw_num	    = inet->num;
		tw->tw_state	    = TCP_TIME_WAIT;
		tw->tw_substate	    = state;
		tw->tw_sport	    = inet->sport;
		tw->tw_dport	    = inet->dport;
		tw->tw_family	    = sk->sk_family;
		tw->tw_reuse	    = sk->sk_reuse;
		tw->tw_hash	    = sk->sk_hash;
		tw->tw_ipv6only	    = 0;
		tw->tw_prot	    = sk->sk_prot_creator;
		atomic_set(&tw->tw_refcnt, 1);
		inet_twsk_dead_node_init(tw);
	}

	return tw;
}

EXPORT_SYMBOL_GPL(inet_twsk_alloc);

/* Returns non-zero if quota exceeded.  */
static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr,
				    const int slot)
{
	struct inet_timewait_sock *tw;
	struct hlist_node *node;
	unsigned int killed;
	int ret;

	/* NOTE: compare this to previous version where lock
	 * was released after detaching chain. It was racy,
	 * because tw buckets are scheduled in not serialized context
	 * in 2.3 (with netfilter), and with softnet it is common, because
	 * soft irqs are not sequenced.
	 */
	killed = 0;
	ret = 0;
rescan:
	inet_twsk_for_each_inmate(tw, node, &twdr->cells[slot]) {
		__inet_twsk_del_dead_node(tw);
		spin_unlock(&twdr->death_lock);
		__inet_twsk_kill(tw, twdr->hashinfo);
		inet_twsk_put(tw);
		killed++;
		spin_lock(&twdr->death_lock);
		if (killed > INET_TWDR_TWKILL_QUOTA) {
			ret = 1;
			break;
		}

		/* While we dropped twdr->death_lock, another cpu may have
		 * killed off the next TW bucket in the list, therefore
		 * do a fresh re-read of the hlist head node with the
		 * lock reacquired.  We still use the hlist traversal
		 * macro in order to get the prefetches.
		 */
		goto rescan;
	}

	twdr->tw_count -= killed;
	NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITED, killed);

	return ret;
}

void inet_twdr_hangman(unsigned long data)
{
	struct inet_timewait_death_row *twdr;
	int unsigned need_timer;

	twdr = (struct inet_timewait_death_row *)data;
	spin_lock(&twdr->death_lock);

	if (twdr->tw_count == 0)
		goto out;

	need_timer = 0;
	if (inet_twdr_do_twkill_work(twdr, twdr->slot)) {
		twdr->thread_slots |= (1 << twdr->slot);
		mb();
		schedule_work(&twdr->twkill_work);
		need_timer = 1;
	} else {
		/* We purged the entire slot, anything left?  */
		if (twdr->tw_count)
			need_timer = 1;
	}
	twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1));
	if (need_timer)
		mod_timer(&twdr->tw_timer, jiffies + twdr->period);
out:
	spin_unlock(&twdr->death_lock);
}

EXPORT_SYMBOL_GPL(inet_twdr_hangman);

extern void twkill_slots_invalid(void);

void inet_twdr_twkill_work(void *data)
{
	struct inet_timewait_death_row *twdr = data;
	int i;

	if ((INET_TWDR_TWKILL_SLOTS - 1) > (sizeof(twdr->thread_slots) * 8))
		twkill_slots_invalid();

	while (twdr->thread_slots) {
		spin_lock_bh(&twdr->death_lock);
		for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) {
			if (!(twdr->thread_slots & (1 << i)))
				continue;

			while (inet_twdr_do_twkill_work(twdr, i) != 0) {
				if (need_resched()) {
					spin_unlock_bh(&twdr->death_lock);
					schedule();
					spin_lock_bh(&twdr->death_lock);
				}
			}

			twdr->thread_slots &= ~(1 << i);
		}
		spin_unlock_bh(&twdr->death_lock);
	}
}

EXPORT_SYMBOL_GPL(inet_twdr_twkill_work);

/* These are always called from BH context.  See callers in
 * tcp_input.c to verify this.
 */

/* This is for handling early-kills of TIME_WAIT sockets. */
void inet_twsk_deschedule(struct inet_timewait_sock *tw,
			  struct inet_timewait_death_row *twdr)
{
	spin_lock(&twdr->death_lock);
	if (inet_twsk_del_dead_node(tw)) {
		inet_twsk_put(tw);
		if (--twdr->tw_count == 0)
			del_timer(&twdr->tw_timer);
	}
	spin_unlock(&twdr->death_lock);
	__inet_twsk_kill(tw, twdr->hashinfo);
}

EXPORT_SYMBOL(inet_twsk_deschedule);

void inet_twsk_schedule(struct inet_timewait_sock *tw,
		       struct inet_timewait_death_row *twdr,
		       const int timeo, const int timewait_len)
{
	struct hlist_head *list;
	int slot;

	/* timeout := RTO * 3.5
	 *
	 * 3.5 = 1+2+0.5 to wait for two retransmits.
	 *
	 * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
	 * our ACK acking that FIN can be lost. If N subsequent retransmitted
	 * FINs (or previous seqments) are lost (probability of such event
	 * is p^(N+1), where p is probability to lose single packet and
	 * time to detect the loss is about RTO*(2^N - 1) with exponential
	 * backoff). Normal timewait length is calculated so, that we
	 * waited at least for one retransmitted FIN (maximal RTO is 120sec).
	 * [ BTW Linux. following BSD, violates this requirement waiting
	 *   only for 60sec, we should wait at least for 240 secs.
	 *   Well, 240 consumes too much of resources 8)
	 * ]
	 * This interval is not reduced to catch old duplicate and
	 * responces to our wandering segments living for two MSLs.
	 * However, if we use PAWS to detect
	 * old duplicates, we can reduce the interval to bounds required
	 * by RTO, rather than MSL. So, if peer understands PAWS, we
	 * kill tw bucket after 3.5*RTO (it is important that this number
	 * is greater than TS tick!) and detect old duplicates with help
	 * of PAWS.
	 */
	slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK;

	spin_lock(&twdr->death_lock);

	/* Unlink it, if it was scheduled */
	if (inet_twsk_del_dead_node(tw))
		twdr->tw_count--;
	else
		atomic_inc(&tw->tw_refcnt);

	if (slot >= INET_TWDR_RECYCLE_SLOTS) {
		/* Schedule to slow timer */
		if (timeo >= timewait_len) {
			slot = INET_TWDR_TWKILL_SLOTS - 1;
		} else {
			slot = (timeo + twdr->period - 1) / twdr->period;
			if (slot >= INET_TWDR_TWKILL_SLOTS)
				slot = INET_TWDR_TWKILL_SLOTS - 1;
		}
		tw->tw_ttd = jiffies + timeo;
		slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1);
		list = &twdr->cells[slot];
	} else {
		tw->tw_ttd = jiffies + (slot << INET_TWDR_RECYCLE_TICK);

		if (twdr->twcal_hand < 0) {
			twdr->twcal_hand = 0;
			twdr->twcal_jiffie = jiffies;
			twdr->twcal_timer.expires = twdr->twcal_jiffie +
					      (slot << INET_TWDR_RECYCLE_TICK);
			add_timer(&twdr->twcal_timer);
		} else {
			if (time_after(twdr->twcal_timer.expires,
				       jiffies + (slot << INET_TWDR_RECYCLE_TICK)))
				mod_timer(&twdr->twcal_timer,
					  jiffies + (slot << INET_TWDR_RECYCLE_TICK));
			slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1);
		}
		list = &twdr->twcal_row[slot];
	}

	hlist_add_head(&tw->tw_death_node, list);

	if (twdr->tw_count++ == 0)
		mod_timer(&twdr->tw_timer, jiffies + twdr->period);
	spin_unlock(&twdr->death_lock);
}

EXPORT_SYMBOL_GPL(inet_twsk_schedule);

void inet_twdr_twcal_tick(unsigned long data)
{
	struct inet_timewait_death_row *twdr;
	int n, slot;
	unsigned long j;
	unsigned long now = jiffies;
	int killed = 0;
	int adv = 0;

	twdr = (struct inet_timewait_death_row *)data;

	spin_lock(&twdr->death_lock);
	if (twdr->twcal_hand < 0)
		goto out;

	slot = twdr->twcal_hand;
	j = twdr->twcal_jiffie;

	for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) {
		if (time_before_eq(j, now)) {
			struct hlist_node *node, *safe;
			struct inet_timewait_sock *tw;

			inet_twsk_for_each_inmate_safe(tw, node, safe,
						       &twdr->twcal_row[slot]) {
				__inet_twsk_del_dead_node(tw);
				__inet_twsk_kill(tw, twdr->hashinfo);
				inet_twsk_put(tw);
				killed++;
			}
		} else {
			if (!adv) {
				adv = 1;
				twdr->twcal_jiffie = j;
				twdr->twcal_hand = slot;
			}

			if (!hlist_empty(&twdr->twcal_row[slot])) {
				mod_timer(&twdr->twcal_timer, j);
				goto out;
			}
		}
		j += 1 << INET_TWDR_RECYCLE_TICK;
		slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1);
	}
	twdr->twcal_hand = -1;

out:
	if ((twdr->tw_count -= killed) == 0)
		del_timer(&twdr->tw_timer);
	NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITKILLED, killed);
	spin_unlock(&twdr->death_lock);
}

EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick);
Commit	Line	Data
e48c414e ACM	1	/*
	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	* Generic TIME_WAIT sockets functions
	7	*
	8	* From code orinally in TCP
	9	*/
	10
	11	#include <linux/config.h>
	12
	13	#include <net/inet_hashtables.h>
	14	#include <net/inet_timewait_sock.h>
696ab2d3	15	#include <net/ip.h>
e48c414e ACM	16
	17	/* Must be called with locally disabled BHs. */
	18	void __inet_twsk_kill(struct inet_timewait_sock tw, struct inet_hashinfo hashinfo)
	19	{
	20	struct inet_bind_hashbucket *bhead;
	21	struct inet_bind_bucket *tb;
	22	/* Unlink from established hashes. */
81c3d547	23	struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, tw->tw_hash);
e48c414e ACM	24
	25	write_lock(&ehead->lock);
	26	if (hlist_unhashed(&tw->tw_node)) {
	27	write_unlock(&ehead->lock);
	28	return;
	29	}
	30	__hlist_del(&tw->tw_node);
	31	sk_node_init(&tw->tw_node);
	32	write_unlock(&ehead->lock);
	33
	34	/* Disassociate with bind bucket. */
	35	bhead = &hashinfo->bhash[inet_bhashfn(tw->tw_num, hashinfo->bhash_size)];
	36	spin_lock(&bhead->lock);
	37	tb = tw->tw_tb;
	38	__hlist_del(&tw->tw_bind_node);
	39	tw->tw_tb = NULL;
	40	inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
	41	spin_unlock(&bhead->lock);
	42	#ifdef SOCK_REFCNT_DEBUG
	43	if (atomic_read(&tw->tw_refcnt) != 1) {
	44	printk(KERN_DEBUG "%s timewait_sock %p refcnt=%d\n",
	45	tw->tw_prot->name, tw, atomic_read(&tw->tw_refcnt));
	46	}
	47	#endif
	48	inet_twsk_put(tw);
	49	}
	50
d8c97a94 ACM	51	EXPORT_SYMBOL_GPL(__inet_twsk_kill);
d8c97a94 ACM	52
e48c414e ACM	53	/*
	54	* Enter the time wait state. This is called with locally disabled BH.
	55	* Essentially we whip up a timewait bucket, copy the relevant info into it
	56	* from the SK, and mess with hash chains and list linkage.
	57	*/
	58	void __inet_twsk_hashdance(struct inet_timewait_sock tw, struct sock sk,
	59	struct inet_hashinfo *hashinfo)
	60	{
	61	const struct inet_sock *inet = inet_sk(sk);
463c84b9	62	const struct inet_connection_sock *icsk = inet_csk(sk);
81c3d547	63	struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
e48c414e ACM	64	struct inet_bind_hashbucket *bhead;
	65	/* Step 1: Put TW into bind hash. Original socket stays there too.
	66	Note, that any socket with inet->num != 0 MUST be bound in
	67	binding cache, even if it is closed.
	68	*/
	69	bhead = &hashinfo->bhash[inet_bhashfn(inet->num, hashinfo->bhash_size)];
	70	spin_lock(&bhead->lock);
463c84b9 ACM	71	tw->tw_tb = icsk->icsk_bind_hash;
463c84b9 ACM	72	BUG_TRAP(icsk->icsk_bind_hash);
e48c414e ACM	73	inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
	74	spin_unlock(&bhead->lock);
	75
	76	write_lock(&ehead->lock);
	77
	78	/* Step 2: Remove SK from established hash. */
	79	if (__sk_del_node_init(sk))
	80	sock_prot_dec_use(sk->sk_prot);
	81
	82	/* Step 3: Hash TW into TIMEWAIT half of established hash table. */
	83	inet_twsk_add_node(tw, &(ehead + hashinfo->ehash_size)->chain);
	84	atomic_inc(&tw->tw_refcnt);
	85
	86	write_unlock(&ehead->lock);
	87	}
c676270b	88
696ab2d3 ACM	89	EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);
696ab2d3 ACM	90
c676270b ACM	91	struct inet_timewait_sock inet_twsk_alloc(const struct sock sk, const int state)
	92	{
	93	struct inet_timewait_sock *tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_slab,
	94	SLAB_ATOMIC);
	95	if (tw != NULL) {
	96	const struct inet_sock *inet = inet_sk(sk);
	97
	98	/* Give us an identity. */
	99	tw->tw_daddr = inet->daddr;
	100	tw->tw_rcv_saddr = inet->rcv_saddr;
	101	tw->tw_bound_dev_if = sk->sk_bound_dev_if;
	102	tw->tw_num = inet->num;
	103	tw->tw_state = TCP_TIME_WAIT;
	104	tw->tw_substate = state;
	105	tw->tw_sport = inet->sport;
	106	tw->tw_dport = inet->dport;
	107	tw->tw_family = sk->sk_family;
	108	tw->tw_reuse = sk->sk_reuse;
81c3d547	109	tw->tw_hash = sk->sk_hash;
c676270b ACM	110	tw->tw_ipv6only = 0;
	111	tw->tw_prot = sk->sk_prot_creator;
	112	atomic_set(&tw->tw_refcnt, 1);
	113	inet_twsk_dead_node_init(tw);
	114	}
	115
	116	return tw;
	117	}
696ab2d3 ACM	118
	119	EXPORT_SYMBOL_GPL(inet_twsk_alloc);
	120
	121	/* Returns non-zero if quota exceeded. */
	122	static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr,
	123	const int slot)
	124	{
	125	struct inet_timewait_sock *tw;
	126	struct hlist_node *node;
	127	unsigned int killed;
	128	int ret;
	129
	130	/* NOTE: compare this to previous version where lock
	131	* was released after detaching chain. It was racy,
	132	* because tw buckets are scheduled in not serialized context
	133	* in 2.3 (with netfilter), and with softnet it is common, because
	134	* soft irqs are not sequenced.
	135	*/
	136	killed = 0;
	137	ret = 0;
	138	rescan:
	139	inet_twsk_for_each_inmate(tw, node, &twdr->cells[slot]) {
	140	__inet_twsk_del_dead_node(tw);
	141	spin_unlock(&twdr->death_lock);
	142	__inet_twsk_kill(tw, twdr->hashinfo);
	143	inet_twsk_put(tw);
	144	killed++;
	145	spin_lock(&twdr->death_lock);
	146	if (killed > INET_TWDR_TWKILL_QUOTA) {
	147	ret = 1;
	148	break;
	149	}
	150
	151	/* While we dropped twdr->death_lock, another cpu may have
	152	* killed off the next TW bucket in the list, therefore
	153	* do a fresh re-read of the hlist head node with the
	154	* lock reacquired. We still use the hlist traversal
	155	* macro in order to get the prefetches.
	156	*/
	157	goto rescan;
	158	}
	159
	160	twdr->tw_count -= killed;
	161	NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITED, killed);
	162
	163	return ret;
	164	}
	165
	166	void inet_twdr_hangman(unsigned long data)
	167	{
	168	struct inet_timewait_death_row *twdr;
	169	int unsigned need_timer;
	170
	171	twdr = (struct inet_timewait_death_row *)data;
	172	spin_lock(&twdr->death_lock);
	173
	174	if (twdr->tw_count == 0)
	175	goto out;
	176
	177	need_timer = 0;
	178	if (inet_twdr_do_twkill_work(twdr, twdr->slot)) {
	179	twdr->thread_slots \|= (1 << twdr->slot);
	180	mb();
	181	schedule_work(&twdr->twkill_work);
182	need_timer = 1;
183	} else {
184	/* We purged the entire slot, anything left? */
185	if (twdr->tw_count)
186	need_timer = 1;
187	}
188	twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1));
189	if (need_timer)
190	mod_timer(&twdr->tw_timer, jiffies + twdr->period);
191	out:
192	spin_unlock(&twdr->death_lock);
193	}
194
195	EXPORT_SYMBOL_GPL(inet_twdr_hangman);
196
197	extern void twkill_slots_invalid(void);
198
199	void inet_twdr_twkill_work(void *data)
200	{
201	struct inet_timewait_death_row *twdr = data;
202	int i;
203
204	if ((INET_TWDR_TWKILL_SLOTS - 1) > (sizeof(twdr->thread_slots) * 8))
205	twkill_slots_invalid();
206
207	while (twdr->thread_slots) {
208	spin_lock_bh(&twdr->death_lock);
209	for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) {
210	if (!(twdr->thread_slots & (1 << i)))
211	continue;
212
213	while (inet_twdr_do_twkill_work(twdr, i) != 0) {
214	if (need_resched()) {
215	spin_unlock_bh(&twdr->death_lock);
216	schedule();
217	spin_lock_bh(&twdr->death_lock);
218	}
219	}
220
221	twdr->thread_slots &= ~(1 << i);
222	}
223	spin_unlock_bh(&twdr->death_lock);
224	}
225	}
226
227	EXPORT_SYMBOL_GPL(inet_twdr_twkill_work);
228
229	/* These are always called from BH context. See callers in
230	* tcp_input.c to verify this.
231	*/
232
233	/* This is for handling early-kills of TIME_WAIT sockets. */
234	void inet_twsk_deschedule(struct inet_timewait_sock *tw,
235	struct inet_timewait_death_row *twdr)
236	{
237	spin_lock(&twdr->death_lock);
238	if (inet_twsk_del_dead_node(tw)) {
239	inet_twsk_put(tw);
240	if (--twdr->tw_count == 0)
241	del_timer(&twdr->tw_timer);
242	}
243	spin_unlock(&twdr->death_lock);
244	__inet_twsk_kill(tw, twdr->hashinfo);
245	}
246
247	EXPORT_SYMBOL(inet_twsk_deschedule);
248
249	void inet_twsk_schedule(struct inet_timewait_sock *tw,
250	struct inet_timewait_death_row *twdr,
251	const int timeo, const int timewait_len)
252	{
253	struct hlist_head *list;
254	int slot;
255
256	/* timeout := RTO * 3.5
257	*
258	* 3.5 = 1+2+0.5 to wait for two retransmits.
259	*
260	* RATIONALE: if FIN arrived and we entered TIME-WAIT state,
261	* our ACK acking that FIN can be lost. If N subsequent retransmitted
262	* FINs (or previous seqments) are lost (probability of such event
263	* is p^(N+1), where p is probability to lose single packet and
264	* time to detect the loss is about RTO*(2^N - 1) with exponential
265	* backoff). Normal timewait length is calculated so, that we
266	* waited at least for one retransmitted FIN (maximal RTO is 120sec).
267	* [ BTW Linux. following BSD, violates this requirement waiting
268	* only for 60sec, we should wait at least for 240 secs.
269	* Well, 240 consumes too much of resources 8)
270	* ]
271	* This interval is not reduced to catch old duplicate and
272	* responces to our wandering segments living for two MSLs.
273	* However, if we use PAWS to detect
274	* old duplicates, we can reduce the interval to bounds required
275	* by RTO, rather than MSL. So, if peer understands PAWS, we
276	* kill tw bucket after 3.5*RTO (it is important that this number
277	* is greater than TS tick!) and detect old duplicates with help
278	* of PAWS.
279	*/
280	slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK;
281
282	spin_lock(&twdr->death_lock);
283
284	/* Unlink it, if it was scheduled */
285	if (inet_twsk_del_dead_node(tw))
286	twdr->tw_count--;
287	else
288	atomic_inc(&tw->tw_refcnt);
289
290	if (slot >= INET_TWDR_RECYCLE_SLOTS) {
291	/* Schedule to slow timer */
292	if (timeo >= timewait_len) {
293	slot = INET_TWDR_TWKILL_SLOTS - 1;
294	} else {
295	slot = (timeo + twdr->period - 1) / twdr->period;
296	if (slot >= INET_TWDR_TWKILL_SLOTS)
297	slot = INET_TWDR_TWKILL_SLOTS - 1;
298	}
299	tw->tw_ttd = jiffies + timeo;
300	slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1);
301	list = &twdr->cells[slot];
302	} else {
303	tw->tw_ttd = jiffies + (slot << INET_TWDR_RECYCLE_TICK);
304
305	if (twdr->twcal_hand < 0) {
306	twdr->twcal_hand = 0;
307	twdr->twcal_jiffie = jiffies;
308	twdr->twcal_timer.expires = twdr->twcal_jiffie +
309	(slot << INET_TWDR_RECYCLE_TICK);
310	add_timer(&twdr->twcal_timer);
311	} else {
312	if (time_after(twdr->twcal_timer.expires,
313	jiffies + (slot << INET_TWDR_RECYCLE_TICK)))
314	mod_timer(&twdr->twcal_timer,
315	jiffies + (slot << INET_TWDR_RECYCLE_TICK));
316	slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1);
317	}
318	list = &twdr->twcal_row[slot];
319	}
320
321	hlist_add_head(&tw->tw_death_node, list);
322
323	if (twdr->tw_count++ == 0)
324	mod_timer(&twdr->tw_timer, jiffies + twdr->period);
325	spin_unlock(&twdr->death_lock);
326	}
327
328	EXPORT_SYMBOL_GPL(inet_twsk_schedule);
329
330	void inet_twdr_twcal_tick(unsigned long data)
331	{
332	struct inet_timewait_death_row *twdr;
333	int n, slot;
334	unsigned long j;
335	unsigned long now = jiffies;
336	int killed = 0;
337	int adv = 0;
338
339	twdr = (struct inet_timewait_death_row *)data;
340
341	spin_lock(&twdr->death_lock);
342	if (twdr->twcal_hand < 0)
343	goto out;
344
345	slot = twdr->twcal_hand;
346	j = twdr->twcal_jiffie;
347
348	for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) {
349	if (time_before_eq(j, now)) {
350	struct hlist_node node, safe;
351	struct inet_timewait_sock *tw;
352
353	inet_twsk_for_each_inmate_safe(tw, node, safe,
354	&twdr->twcal_row[slot]) {
355	__inet_twsk_del_dead_node(tw);
356	__inet_twsk_kill(tw, twdr->hashinfo);
357	inet_twsk_put(tw);
358	killed++;
359	}
360	} else {
361	if (!adv) {
362	adv = 1;
363	twdr->twcal_jiffie = j;
364	twdr->twcal_hand = slot;
365	}
366
367	if (!hlist_empty(&twdr->twcal_row[slot])) {
368	mod_timer(&twdr->twcal_timer, j);
369	goto out;
370	}
371	}
372	j += 1 << INET_TWDR_RECYCLE_TICK;
373	slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1);
374	}
375	twdr->twcal_hand = -1;
376
377	out:
378	if ((twdr->tw_count -= killed) == 0)
379	del_timer(&twdr->tw_timer);
380	NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITKILLED, killed);
381	spin_unlock(&twdr->death_lock);
382	}
383
384	EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick);