[linux.git] / net / ipv4 / tcp_cong.c

/*
 * Plugable TCP congestion control support and newReno
 * congestion control.
 * Based on ideas from I/O scheduler suport and Web100.
 *
 * Copyright (C) 2005 Stephen Hemminger <[email protected]>
 */

#include <linux/module.h>
#include <linux/mm.h>
#include <linux/types.h>
#include <linux/list.h>
#include <net/tcp.h>

int sysctl_tcp_max_ssthresh = 0;

static DEFINE_SPINLOCK(tcp_cong_list_lock);
static LIST_HEAD(tcp_cong_list);

/* Simple linear search, don't expect many entries! */
static struct tcp_congestion_ops *tcp_ca_find(const char *name)
{
	struct tcp_congestion_ops *e;

	list_for_each_entry_rcu(e, &tcp_cong_list, list) {
		if (strcmp(e->name, name) == 0)
			return e;
	}

	return NULL;
}

/*
 * Attach new congestion control algorithm to the list
 * of available options.
 */
int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
{
	int ret = 0;

	/* all algorithms must implement ssthresh and cong_avoid ops */
	if (!ca->ssthresh || !ca->cong_avoid) {
		printk(KERN_ERR "TCP %s does not implement required ops\n",
		       ca->name);
		return -EINVAL;
	}

	spin_lock(&tcp_cong_list_lock);
	if (tcp_ca_find(ca->name)) {
		printk(KERN_NOTICE "TCP %s already registered\n", ca->name);
		ret = -EEXIST;
	} else {
		list_add_tail_rcu(&ca->list, &tcp_cong_list);
		printk(KERN_INFO "TCP %s registered\n", ca->name);
	}
	spin_unlock(&tcp_cong_list_lock);

	return ret;
}
EXPORT_SYMBOL_GPL(tcp_register_congestion_control);

/*
 * Remove congestion control algorithm, called from
 * the module's remove function.  Module ref counts are used
 * to ensure that this can't be done till all sockets using
 * that method are closed.
 */
void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
{
	spin_lock(&tcp_cong_list_lock);
	list_del_rcu(&ca->list);
	spin_unlock(&tcp_cong_list_lock);
}
EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);

/* Assign choice of congestion control. */
void tcp_init_congestion_control(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct tcp_congestion_ops *ca;

	/* if no choice made yet assign the current value set as default */
	if (icsk->icsk_ca_ops == &tcp_init_congestion_ops) {
		rcu_read_lock();
		list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
			if (try_module_get(ca->owner)) {
				icsk->icsk_ca_ops = ca;
				break;
			}

			/* fallback to next available */
		}
		rcu_read_unlock();
	}

	if (icsk->icsk_ca_ops->init)
		icsk->icsk_ca_ops->init(sk);
}

/* Manage refcounts on socket close. */
void tcp_cleanup_congestion_control(struct sock *sk)
{
	struct inet_connection_sock *icsk = inet_csk(sk);

	if (icsk->icsk_ca_ops->release)
		icsk->icsk_ca_ops->release(sk);
	module_put(icsk->icsk_ca_ops->owner);
}

/* Used by sysctl to change default congestion control */
int tcp_set_default_congestion_control(const char *name)
{
	struct tcp_congestion_ops *ca;
	int ret = -ENOENT;

	spin_lock(&tcp_cong_list_lock);
	ca = tcp_ca_find(name);
#ifdef CONFIG_KMOD
	if (!ca && capable(CAP_SYS_MODULE)) {
		spin_unlock(&tcp_cong_list_lock);

		request_module("tcp_%s", name);
		spin_lock(&tcp_cong_list_lock);
		ca = tcp_ca_find(name);
	}
#endif

	if (ca) {
		ca->flags |= TCP_CONG_NON_RESTRICTED;	/* default is always allowed */
		list_move(&ca->list, &tcp_cong_list);
		ret = 0;
	}
	spin_unlock(&tcp_cong_list_lock);

	return ret;
}

/* Set default value from kernel configuration at bootup */
static int __init tcp_congestion_default(void)
{
	return tcp_set_default_congestion_control(CONFIG_DEFAULT_TCP_CONG);
}
late_initcall(tcp_congestion_default);


/* Build string with list of available congestion control values */
void tcp_get_available_congestion_control(char *buf, size_t maxlen)
{
	struct tcp_congestion_ops *ca;
	size_t offs = 0;

	rcu_read_lock();
	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
		offs += snprintf(buf + offs, maxlen - offs,
				 "%s%s",
				 offs == 0 ? "" : " ", ca->name);

	}
	rcu_read_unlock();
}

/* Get current default congestion control */
void tcp_get_default_congestion_control(char *name)
{
	struct tcp_congestion_ops *ca;
	/* We will always have reno... */
	BUG_ON(list_empty(&tcp_cong_list));

	rcu_read_lock();
	ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list);
	strncpy(name, ca->name, TCP_CA_NAME_MAX);
	rcu_read_unlock();
}

/* Built list of non-restricted congestion control values */
void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)
{
	struct tcp_congestion_ops *ca;
	size_t offs = 0;

	*buf = '\0';
	rcu_read_lock();
	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
		if (!(ca->flags & TCP_CONG_NON_RESTRICTED))
			continue;
		offs += snprintf(buf + offs, maxlen - offs,
				 "%s%s",
				 offs == 0 ? "" : " ", ca->name);

	}
	rcu_read_unlock();
}

/* Change list of non-restricted congestion control */
int tcp_set_allowed_congestion_control(char *val)
{
	struct tcp_congestion_ops *ca;
	char *clone, *name;
	int ret = 0;

	clone = kstrdup(val, GFP_USER);
	if (!clone)
		return -ENOMEM;

	spin_lock(&tcp_cong_list_lock);
	/* pass 1 check for bad entries */
	while ((name = strsep(&clone, " ")) && *name) {
		ca = tcp_ca_find(name);
		if (!ca) {
			ret = -ENOENT;
			goto out;
		}
	}

	/* pass 2 clear old values */
	list_for_each_entry_rcu(ca, &tcp_cong_list, list)
		ca->flags &= ~TCP_CONG_NON_RESTRICTED;

	/* pass 3 mark as allowed */
	while ((name = strsep(&val, " ")) && *name) {
		ca = tcp_ca_find(name);
		WARN_ON(!ca);
		if (ca)
			ca->flags |= TCP_CONG_NON_RESTRICTED;
	}
out:
	spin_unlock(&tcp_cong_list_lock);

	return ret;
}


/* Change congestion control for socket */
int tcp_set_congestion_control(struct sock *sk, const char *name)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	struct tcp_congestion_ops *ca;
	int err = 0;

	rcu_read_lock();
	ca = tcp_ca_find(name);

	/* no change asking for existing value */
	if (ca == icsk->icsk_ca_ops)
		goto out;

#ifdef CONFIG_KMOD
	/* not found attempt to autoload module */
	if (!ca && capable(CAP_SYS_MODULE)) {
		rcu_read_unlock();
		request_module("tcp_%s", name);
		rcu_read_lock();
		ca = tcp_ca_find(name);
	}
#endif
	if (!ca)
		err = -ENOENT;

	else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || capable(CAP_NET_ADMIN)))
		err = -EPERM;

	else if (!try_module_get(ca->owner))
		err = -EBUSY;

	else {
		tcp_cleanup_congestion_control(sk);
		icsk->icsk_ca_ops = ca;

		if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init)
			icsk->icsk_ca_ops->init(sk);
	}
 out:
	rcu_read_unlock();
	return err;
}


/*
 * Slow start is used when congestion window is less than slow start
 * threshold. This version implements the basic RFC2581 version
 * and optionally supports:
 * 	RFC3742 Limited Slow Start  	  - growth limited to max_ssthresh
 *	RFC3465 Appropriate Byte Counting - growth limited by bytes acknowledged
 */
void tcp_slow_start(struct tcp_sock *tp)
{
	int cnt; /* increase in packets */

	/* RFC3465: ABC Slow start
	 * Increase only after a full MSS of bytes is acked
	 *
	 * TCP sender SHOULD increase cwnd by the number of
	 * previously unacknowledged bytes ACKed by each incoming
	 * acknowledgment, provided the increase is not more than L
	 */
	if (sysctl_tcp_abc && tp->bytes_acked < tp->mss_cache)
		return;

	if (sysctl_tcp_max_ssthresh > 0 && tp->snd_cwnd > sysctl_tcp_max_ssthresh)
		cnt = sysctl_tcp_max_ssthresh >> 1;	/* limited slow start */
	else
		cnt = tp->snd_cwnd;			/* exponential increase */

	/* RFC3465: ABC
	 * We MAY increase by 2 if discovered delayed ack
	 */
	if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache)
		cnt <<= 1;
	tp->bytes_acked = 0;

	tp->snd_cwnd_cnt += cnt;
	while (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
		tp->snd_cwnd_cnt -= tp->snd_cwnd;
		if (tp->snd_cwnd < tp->snd_cwnd_clamp)
			tp->snd_cwnd++;
	}
}
EXPORT_SYMBOL_GPL(tcp_slow_start);

/*
 * TCP Reno congestion control
 * This is special case used for fallback as well.
 */
/* This is Jacobson's slow start and congestion avoidance.
 * SIGCOMM '88, p. 328.
 */
void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 rtt, u32 in_flight,
			 int flag)
{
	struct tcp_sock *tp = tcp_sk(sk);

	if (!tcp_is_cwnd_limited(sk, in_flight))
		return;

	/* In "safe" area, increase. */
	if (tp->snd_cwnd <= tp->snd_ssthresh)
		tcp_slow_start(tp);

	/* In dangerous area, increase slowly. */
	else if (sysctl_tcp_abc) {
		/* RFC3465: Appropriate Byte Count
		 * increase once for each full cwnd acked
		 */
		if (tp->bytes_acked >= tp->snd_cwnd*tp->mss_cache) {
			tp->bytes_acked -= tp->snd_cwnd*tp->mss_cache;
			if (tp->snd_cwnd < tp->snd_cwnd_clamp)
				tp->snd_cwnd++;
		}
	} else {
		/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd */
		if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
			if (tp->snd_cwnd < tp->snd_cwnd_clamp)
				tp->snd_cwnd++;
			tp->snd_cwnd_cnt = 0;
		} else
			tp->snd_cwnd_cnt++;
	}
}
EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);

/* Slow start threshold is half the congestion window (min 2) */
u32 tcp_reno_ssthresh(struct sock *sk)
{
	const struct tcp_sock *tp = tcp_sk(sk);
	return max(tp->snd_cwnd >> 1U, 2U);
}
EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);

/* Lower bound on congestion window with halving. */
u32 tcp_reno_min_cwnd(const struct sock *sk)
{
	const struct tcp_sock *tp = tcp_sk(sk);
	return tp->snd_ssthresh/2;
}
EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd);

struct tcp_congestion_ops tcp_reno = {
	.flags		= TCP_CONG_NON_RESTRICTED,
	.name		= "reno",
	.owner		= THIS_MODULE,
	.ssthresh	= tcp_reno_ssthresh,
	.cong_avoid	= tcp_reno_cong_avoid,
	.min_cwnd	= tcp_reno_min_cwnd,
};

/* Initial congestion control used (until SYN)
 * really reno under another name so we can tell difference
 * during tcp_set_default_congestion_control
 */
struct tcp_congestion_ops tcp_init_congestion_ops  = {
	.name		= "",
	.owner		= THIS_MODULE,
	.ssthresh	= tcp_reno_ssthresh,
	.cong_avoid	= tcp_reno_cong_avoid,
	.min_cwnd	= tcp_reno_min_cwnd,
};
EXPORT_SYMBOL_GPL(tcp_init_congestion_ops);
Commit	Line	Data
317a76f9 SH	1	/*
	2	* Plugable TCP congestion control support and newReno
	3	* congestion control.
	4	* Based on ideas from I/O scheduler suport and Web100.
	5	*
	6	* Copyright (C) 2005 Stephen Hemminger <[email protected]>
	7	*/
	8
317a76f9 SH	9	#include <linux/module.h>
	10	#include <linux/mm.h>
	11	#include <linux/types.h>
	12	#include <linux/list.h>
	13	#include <net/tcp.h>
	14
886236c1 JH	15	int sysctl_tcp_max_ssthresh = 0;
886236c1 JH	16
317a76f9 SH	17	static DEFINE_SPINLOCK(tcp_cong_list_lock);
	18	static LIST_HEAD(tcp_cong_list);
	19
	20	/* Simple linear search, don't expect many entries! */
	21	static struct tcp_congestion_ops tcp_ca_find(const char name)
	22	{
	23	struct tcp_congestion_ops *e;
	24
5f8ef48d	25	list_for_each_entry_rcu(e, &tcp_cong_list, list) {
317a76f9 SH	26	if (strcmp(e->name, name) == 0)
	27	return e;
	28	}
	29
	30	return NULL;
	31	}
	32
	33	/*
d08df601	34	* Attach new congestion control algorithm to the list
317a76f9 SH	35	* of available options.
	36	*/
	37	int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
	38	{
	39	int ret = 0;
	40
	41	/* all algorithms must implement ssthresh and cong_avoid ops */
72dc5b92	42	if (!ca->ssthresh \|\| !ca->cong_avoid) {
317a76f9 SH	43	printk(KERN_ERR "TCP %s does not implement required ops\n",
	44	ca->name);
	45	return -EINVAL;
	46	}
	47
	48	spin_lock(&tcp_cong_list_lock);
	49	if (tcp_ca_find(ca->name)) {
	50	printk(KERN_NOTICE "TCP %s already registered\n", ca->name);
	51	ret = -EEXIST;
	52	} else {
3d2573f7	53	list_add_tail_rcu(&ca->list, &tcp_cong_list);
317a76f9 SH	54	printk(KERN_INFO "TCP %s registered\n", ca->name);
	55	}
	56	spin_unlock(&tcp_cong_list_lock);
	57
	58	return ret;
	59	}
	60	EXPORT_SYMBOL_GPL(tcp_register_congestion_control);
	61
	62	/*
	63	* Remove congestion control algorithm, called from
	64	* the module's remove function. Module ref counts are used
	65	* to ensure that this can't be done till all sockets using
	66	* that method are closed.
	67	*/
	68	void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
	69	{
	70	spin_lock(&tcp_cong_list_lock);
	71	list_del_rcu(&ca->list);
	72	spin_unlock(&tcp_cong_list_lock);
	73	}
	74	EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
	75
	76	/* Assign choice of congestion control. */
6687e988	77	void tcp_init_congestion_control(struct sock *sk)
317a76f9	78	{
6687e988	79	struct inet_connection_sock *icsk = inet_csk(sk);
317a76f9 SH	80	struct tcp_congestion_ops *ca;
317a76f9 SH	81
4d4d3d1e SH	82	/* if no choice made yet assign the current value set as default */
	83	if (icsk->icsk_ca_ops == &tcp_init_congestion_ops) {
	84	rcu_read_lock();
	85	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
	86	if (try_module_get(ca->owner)) {
	87	icsk->icsk_ca_ops = ca;
	88	break;
	89	}
5f8ef48d	90
4d4d3d1e	91	/* fallback to next available */
317a76f9	92	}
4d4d3d1e	93	rcu_read_unlock();
317a76f9	94	}
317a76f9	95
6687e988 ACM	96	if (icsk->icsk_ca_ops->init)
6687e988 ACM	97	icsk->icsk_ca_ops->init(sk);
317a76f9 SH	98	}
	99
	100	/* Manage refcounts on socket close. */
6687e988	101	void tcp_cleanup_congestion_control(struct sock *sk)
317a76f9	102	{
6687e988 ACM	103	struct inet_connection_sock *icsk = inet_csk(sk);
	104
	105	if (icsk->icsk_ca_ops->release)
	106	icsk->icsk_ca_ops->release(sk);
	107	module_put(icsk->icsk_ca_ops->owner);
317a76f9 SH	108	}
	109
	110	/* Used by sysctl to change default congestion control */
	111	int tcp_set_default_congestion_control(const char *name)
	112	{
	113	struct tcp_congestion_ops *ca;
	114	int ret = -ENOENT;
	115
	116	spin_lock(&tcp_cong_list_lock);
	117	ca = tcp_ca_find(name);
	118	#ifdef CONFIG_KMOD
35bfbc94	119	if (!ca && capable(CAP_SYS_MODULE)) {
317a76f9 SH	120	spin_unlock(&tcp_cong_list_lock);
	121
	122	request_module("tcp_%s", name);
	123	spin_lock(&tcp_cong_list_lock);
	124	ca = tcp_ca_find(name);
	125	}
	126	#endif
	127
	128	if (ca) {
164891aa	129	ca->flags \|= TCP_CONG_NON_RESTRICTED; /* default is always allowed */
317a76f9 SH	130	list_move(&ca->list, &tcp_cong_list);
	131	ret = 0;
	132	}
	133	spin_unlock(&tcp_cong_list_lock);
	134
	135	return ret;
	136	}
	137
b1736a71 SH	138	/* Set default value from kernel configuration at bootup */
	139	static int __init tcp_congestion_default(void)
	140	{
	141	return tcp_set_default_congestion_control(CONFIG_DEFAULT_TCP_CONG);
	142	}
	143	late_initcall(tcp_congestion_default);
	144
	145
3ff825b2 SH	146	/* Build string with list of available congestion control values */
	147	void tcp_get_available_congestion_control(char *buf, size_t maxlen)
	148	{
	149	struct tcp_congestion_ops *ca;
	150	size_t offs = 0;
	151
	152	rcu_read_lock();
	153	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
	154	offs += snprintf(buf + offs, maxlen - offs,
	155	"%s%s",
	156	offs == 0 ? "" : " ", ca->name);
	157
	158	}
	159	rcu_read_unlock();
	160	}
	161
317a76f9 SH	162	/* Get current default congestion control */
	163	void tcp_get_default_congestion_control(char *name)
	164	{
	165	struct tcp_congestion_ops *ca;
	166	/* We will always have reno... */
	167	BUG_ON(list_empty(&tcp_cong_list));
	168
	169	rcu_read_lock();
	170	ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list);
	171	strncpy(name, ca->name, TCP_CA_NAME_MAX);
	172	rcu_read_unlock();
	173	}
	174
ce7bc3bf SH	175	/* Built list of non-restricted congestion control values */
	176	void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)
	177	{
	178	struct tcp_congestion_ops *ca;
	179	size_t offs = 0;
	180
	181	*buf = '\0';
	182	rcu_read_lock();
	183	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
164891aa	184	if (!(ca->flags & TCP_CONG_NON_RESTRICTED))
ce7bc3bf SH	185	continue;
	186	offs += snprintf(buf + offs, maxlen - offs,
	187	"%s%s",
	188	offs == 0 ? "" : " ", ca->name);
	189
	190	}
	191	rcu_read_unlock();
	192	}
	193
	194	/* Change list of non-restricted congestion control */
	195	int tcp_set_allowed_congestion_control(char *val)
	196	{
	197	struct tcp_congestion_ops *ca;
	198	char clone, name;
	199	int ret = 0;
	200
	201	clone = kstrdup(val, GFP_USER);
	202	if (!clone)
	203	return -ENOMEM;
	204
	205	spin_lock(&tcp_cong_list_lock);
	206	/* pass 1 check for bad entries */
	207	while ((name = strsep(&clone, " ")) && *name) {
	208	ca = tcp_ca_find(name);
	209	if (!ca) {
	210	ret = -ENOENT;
	211	goto out;
	212	}
	213	}
	214
164891aa	215	/* pass 2 clear old values */
ce7bc3bf	216	list_for_each_entry_rcu(ca, &tcp_cong_list, list)
164891aa	217	ca->flags &= ~TCP_CONG_NON_RESTRICTED;
ce7bc3bf SH	218
	219	/* pass 3 mark as allowed */
	220	while ((name = strsep(&val, " ")) && *name) {
	221	ca = tcp_ca_find(name);
	222	WARN_ON(!ca);
	223	if (ca)
164891aa	224	ca->flags \|= TCP_CONG_NON_RESTRICTED;
ce7bc3bf SH	225	}
	226	out:
	227	spin_unlock(&tcp_cong_list_lock);
	228
	229	return ret;
	230	}
	231
	232
5f8ef48d	233	/* Change congestion control for socket */
6687e988	234	int tcp_set_congestion_control(struct sock sk, const char name)
5f8ef48d	235	{
6687e988	236	struct inet_connection_sock *icsk = inet_csk(sk);
5f8ef48d SH	237	struct tcp_congestion_ops *ca;
	238	int err = 0;
	239
	240	rcu_read_lock();
	241	ca = tcp_ca_find(name);
4d4d3d1e	242
35bfbc94	243	/* no change asking for existing value */
6687e988	244	if (ca == icsk->icsk_ca_ops)
5f8ef48d SH	245	goto out;
5f8ef48d SH	246
35bfbc94 SH	247	#ifdef CONFIG_KMOD
	248	/* not found attempt to autoload module */
	249	if (!ca && capable(CAP_SYS_MODULE)) {
	250	rcu_read_unlock();
	251	request_module("tcp_%s", name);
	252	rcu_read_lock();
	253	ca = tcp_ca_find(name);
	254	}
	255	#endif
5f8ef48d SH	256	if (!ca)
	257	err = -ENOENT;
	258
164891aa	259	else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) \|\| capable(CAP_NET_ADMIN)))
ce7bc3bf SH	260	err = -EPERM;
ce7bc3bf SH	261
5f8ef48d SH	262	else if (!try_module_get(ca->owner))
	263	err = -EBUSY;
	264
	265	else {
6687e988 ACM	266	tcp_cleanup_congestion_control(sk);
6687e988 ACM	267	icsk->icsk_ca_ops = ca;
4d4d3d1e SH	268
4d4d3d1e SH	269	if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init)
6687e988	270	icsk->icsk_ca_ops->init(sk);
5f8ef48d SH	271	}
	272	out:
	273	rcu_read_unlock();
	274	return err;
	275	}
	276
40efc6fa SH	277
40efc6fa SH	278	/*
a02ba041 SH	279	* Slow start is used when congestion window is less than slow start
	280	* threshold. This version implements the basic RFC2581 version
	281	* and optionally supports:
	282	* RFC3742 Limited Slow Start - growth limited to max_ssthresh
	283	* RFC3465 Appropriate Byte Counting - growth limited by bytes acknowledged
40efc6fa SH	284	*/
	285	void tcp_slow_start(struct tcp_sock *tp)
	286	{
a02ba041 SH	287	int cnt; /* increase in packets */
	288
	289	/* RFC3465: ABC Slow start
	290	* Increase only after a full MSS of bytes is acked
	291	*
	292	* TCP sender SHOULD increase cwnd by the number of
	293	* previously unacknowledged bytes ACKed by each incoming
	294	* acknowledgment, provided the increase is not more than L
	295	*/
	296	if (sysctl_tcp_abc && tp->bytes_acked < tp->mss_cache)
	297	return;
	298
	299	if (sysctl_tcp_max_ssthresh > 0 && tp->snd_cwnd > sysctl_tcp_max_ssthresh)
	300	cnt = sysctl_tcp_max_ssthresh >> 1; /* limited slow start */
886236c1	301	else
a02ba041	302	cnt = tp->snd_cwnd; /* exponential increase */
886236c1	303
a02ba041 SH	304	/* RFC3465: ABC
	305	* We MAY increase by 2 if discovered delayed ack
	306	*/
886236c1 JH	307	if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache)
886236c1 JH	308	cnt <<= 1;
40efc6fa SH	309	tp->bytes_acked = 0;
40efc6fa SH	310
886236c1 JH	311	tp->snd_cwnd_cnt += cnt;
	312	while (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
	313	tp->snd_cwnd_cnt -= tp->snd_cwnd;
	314	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
	315	tp->snd_cwnd++;
	316	}
40efc6fa SH	317	}
	318	EXPORT_SYMBOL_GPL(tcp_slow_start);
	319
317a76f9 SH	320	/*
	321	* TCP Reno congestion control
	322	* This is special case used for fallback as well.
	323	*/
	324	/* This is Jacobson's slow start and congestion avoidance.
	325	* SIGCOMM '88, p. 328.
	326	*/
6687e988	327	void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 rtt, u32 in_flight,
317a76f9 SH	328	int flag)
317a76f9 SH	329	{
6687e988 ACM	330	struct tcp_sock *tp = tcp_sk(sk);
6687e988 ACM	331
f4805ede	332	if (!tcp_is_cwnd_limited(sk, in_flight))
317a76f9 SH	333	return;
317a76f9 SH	334
7faffa1c	335	/* In "safe" area, increase. */
e905a9ed	336	if (tp->snd_cwnd <= tp->snd_ssthresh)
7faffa1c	337	tcp_slow_start(tp);
9772efb9	338
e905a9ed	339	/* In dangerous area, increase slowly. */
9772efb9	340	else if (sysctl_tcp_abc) {
e905a9ed YH	341	/* RFC3465: Appropriate Byte Count
	342	* increase once for each full cwnd acked
	343	*/
	344	if (tp->bytes_acked >= tp->snd_cwnd*tp->mss_cache) {
	345	tp->bytes_acked -= tp->snd_cwnd*tp->mss_cache;
	346	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
	347	tp->snd_cwnd++;
	348	}
	349	} else {
	350	/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd */
	351	if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
	352	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
	353	tp->snd_cwnd++;
	354	tp->snd_cwnd_cnt = 0;
	355	} else
	356	tp->snd_cwnd_cnt++;
	357	}
317a76f9 SH	358	}
	359	EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
	360
	361	/* Slow start threshold is half the congestion window (min 2) */
6687e988	362	u32 tcp_reno_ssthresh(struct sock *sk)
317a76f9	363	{
6687e988	364	const struct tcp_sock *tp = tcp_sk(sk);
317a76f9 SH	365	return max(tp->snd_cwnd >> 1U, 2U);
	366	}
	367	EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
	368
72dc5b92 SH	369	/* Lower bound on congestion window with halving. */
72dc5b92 SH	370	u32 tcp_reno_min_cwnd(const struct sock *sk)
317a76f9	371	{
6687e988	372	const struct tcp_sock *tp = tcp_sk(sk);
317a76f9 SH	373	return tp->snd_ssthresh/2;
	374	}
	375	EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd);
	376
	377	struct tcp_congestion_ops tcp_reno = {
164891aa	378	.flags = TCP_CONG_NON_RESTRICTED,
317a76f9 SH	379	.name = "reno",
	380	.owner = THIS_MODULE,
	381	.ssthresh = tcp_reno_ssthresh,
	382	.cong_avoid = tcp_reno_cong_avoid,
	383	.min_cwnd = tcp_reno_min_cwnd,
	384	};
	385
5f8ef48d SH	386	/* Initial congestion control used (until SYN)
	387	* really reno under another name so we can tell difference
	388	* during tcp_set_default_congestion_control
	389	*/
	390	struct tcp_congestion_ops tcp_init_congestion_ops = {
	391	.name = "",
	392	.owner = THIS_MODULE,
	393	.ssthresh = tcp_reno_ssthresh,
	394	.cong_avoid = tcp_reno_cong_avoid,
	395	.min_cwnd = tcp_reno_min_cwnd,
	396	};
	397	EXPORT_SYMBOL_GPL(tcp_init_congestion_ops);