[deliverable/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 <shemminger@osdl.org>
 */

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

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->non_restricted = 1;	/* 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->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 */
	list_for_each_entry_rcu(ca, &tcp_cong_list, list)
		ca->non_restricted = 0;

	/* pass 3 mark as allowed */
	while ((name = strsep(&val, " ")) && *name) {
		ca = tcp_ca_find(name);
		WARN_ON(!ca);
		if (ca)
			ca->non_restricted = 1;
	}
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->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;
}


/*
 * Linear increase during slow start
 */
void tcp_slow_start(struct tcp_sock *tp)
{
	if (sysctl_tcp_abc) {
		/* RFC3465: Slow Start
		 * 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 (tp->bytes_acked < tp->mss_cache)
			return;

		/* We MAY increase by 2 if discovered delayed ack */
		if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache) {
			if (tp->snd_cwnd < tp->snd_cwnd_clamp)
				tp->snd_cwnd++;
		}
	}
	tp->bytes_acked = 0;

	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 = {
	.name		= "reno",
	.non_restricted = 1,
	.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 <shemminger@osdl.org>
	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
	15	static DEFINE_SPINLOCK(tcp_cong_list_lock);
	16	static LIST_HEAD(tcp_cong_list);
	17
	18	/* Simple linear search, don't expect many entries! */
	19	static struct tcp_congestion_ops tcp_ca_find(const char name)
	20	{
	21	struct tcp_congestion_ops *e;
	22
5f8ef48d	23	list_for_each_entry_rcu(e, &tcp_cong_list, list) {
317a76f9 SH	24	if (strcmp(e->name, name) == 0)
	25	return e;
	26	}
	27
	28	return NULL;
	29	}
	30
	31	/*
d08df601	32	* Attach new congestion control algorithm to the list
317a76f9 SH	33	* of available options.
	34	*/
	35	int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
	36	{
	37	int ret = 0;
	38
	39	/* all algorithms must implement ssthresh and cong_avoid ops */
72dc5b92	40	if (!ca->ssthresh \|\| !ca->cong_avoid) {
317a76f9 SH	41	printk(KERN_ERR "TCP %s does not implement required ops\n",
	42	ca->name);
	43	return -EINVAL;
	44	}
	45
	46	spin_lock(&tcp_cong_list_lock);
	47	if (tcp_ca_find(ca->name)) {
	48	printk(KERN_NOTICE "TCP %s already registered\n", ca->name);
	49	ret = -EEXIST;
	50	} else {
3d2573f7	51	list_add_tail_rcu(&ca->list, &tcp_cong_list);
317a76f9 SH	52	printk(KERN_INFO "TCP %s registered\n", ca->name);
	53	}
	54	spin_unlock(&tcp_cong_list_lock);
	55
	56	return ret;
	57	}
	58	EXPORT_SYMBOL_GPL(tcp_register_congestion_control);
	59
	60	/*
	61	* Remove congestion control algorithm, called from
	62	* the module's remove function. Module ref counts are used
	63	* to ensure that this can't be done till all sockets using
	64	* that method are closed.
	65	*/
	66	void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
	67	{
	68	spin_lock(&tcp_cong_list_lock);
	69	list_del_rcu(&ca->list);
	70	spin_unlock(&tcp_cong_list_lock);
	71	}
	72	EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
	73
	74	/* Assign choice of congestion control. */
6687e988	75	void tcp_init_congestion_control(struct sock *sk)
317a76f9	76	{
6687e988	77	struct inet_connection_sock *icsk = inet_csk(sk);
317a76f9 SH	78	struct tcp_congestion_ops *ca;
317a76f9 SH	79
4d4d3d1e SH	80	/* if no choice made yet assign the current value set as default */
	81	if (icsk->icsk_ca_ops == &tcp_init_congestion_ops) {
	82	rcu_read_lock();
	83	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
	84	if (try_module_get(ca->owner)) {
	85	icsk->icsk_ca_ops = ca;
	86	break;
	87	}
5f8ef48d	88
4d4d3d1e	89	/* fallback to next available */
317a76f9	90	}
4d4d3d1e	91	rcu_read_unlock();
317a76f9	92	}
317a76f9	93
6687e988 ACM	94	if (icsk->icsk_ca_ops->init)
6687e988 ACM	95	icsk->icsk_ca_ops->init(sk);
317a76f9 SH	96	}
	97
	98	/* Manage refcounts on socket close. */
6687e988	99	void tcp_cleanup_congestion_control(struct sock *sk)
317a76f9	100	{
6687e988 ACM	101	struct inet_connection_sock *icsk = inet_csk(sk);
	102
	103	if (icsk->icsk_ca_ops->release)
	104	icsk->icsk_ca_ops->release(sk);
	105	module_put(icsk->icsk_ca_ops->owner);
317a76f9 SH	106	}
	107
	108	/* Used by sysctl to change default congestion control */
	109	int tcp_set_default_congestion_control(const char *name)
	110	{
	111	struct tcp_congestion_ops *ca;
	112	int ret = -ENOENT;
	113
	114	spin_lock(&tcp_cong_list_lock);
	115	ca = tcp_ca_find(name);
	116	#ifdef CONFIG_KMOD
35bfbc94	117	if (!ca && capable(CAP_SYS_MODULE)) {
317a76f9 SH	118	spin_unlock(&tcp_cong_list_lock);
	119
	120	request_module("tcp_%s", name);
	121	spin_lock(&tcp_cong_list_lock);
	122	ca = tcp_ca_find(name);
	123	}
	124	#endif
	125
	126	if (ca) {
ce7bc3bf	127	ca->non_restricted = 1; /* default is always allowed */
317a76f9 SH	128	list_move(&ca->list, &tcp_cong_list);
	129	ret = 0;
	130	}
	131	spin_unlock(&tcp_cong_list_lock);
	132
	133	return ret;
	134	}
	135
b1736a71 SH	136	/* Set default value from kernel configuration at bootup */
	137	static int __init tcp_congestion_default(void)
	138	{
	139	return tcp_set_default_congestion_control(CONFIG_DEFAULT_TCP_CONG);
	140	}
	141	late_initcall(tcp_congestion_default);
	142
	143
3ff825b2 SH	144	/* Build string with list of available congestion control values */
	145	void tcp_get_available_congestion_control(char *buf, size_t maxlen)
	146	{
	147	struct tcp_congestion_ops *ca;
	148	size_t offs = 0;
	149
	150	rcu_read_lock();
	151	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
	152	offs += snprintf(buf + offs, maxlen - offs,
	153	"%s%s",
	154	offs == 0 ? "" : " ", ca->name);
	155
	156	}
	157	rcu_read_unlock();
	158	}
	159
317a76f9 SH	160	/* Get current default congestion control */
	161	void tcp_get_default_congestion_control(char *name)
	162	{
	163	struct tcp_congestion_ops *ca;
	164	/* We will always have reno... */
	165	BUG_ON(list_empty(&tcp_cong_list));
	166
	167	rcu_read_lock();
	168	ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list);
	169	strncpy(name, ca->name, TCP_CA_NAME_MAX);
	170	rcu_read_unlock();
	171	}
	172
ce7bc3bf SH	173	/* Built list of non-restricted congestion control values */
	174	void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)
	175	{
	176	struct tcp_congestion_ops *ca;
	177	size_t offs = 0;
	178
	179	*buf = '\0';
	180	rcu_read_lock();
	181	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
	182	if (!ca->non_restricted)
	183	continue;
	184	offs += snprintf(buf + offs, maxlen - offs,
	185	"%s%s",
	186	offs == 0 ? "" : " ", ca->name);
	187
	188	}
	189	rcu_read_unlock();
	190	}
	191
	192	/* Change list of non-restricted congestion control */
	193	int tcp_set_allowed_congestion_control(char *val)
	194	{
	195	struct tcp_congestion_ops *ca;
	196	char clone, name;
	197	int ret = 0;
	198
	199	clone = kstrdup(val, GFP_USER);
	200	if (!clone)
	201	return -ENOMEM;
	202
	203	spin_lock(&tcp_cong_list_lock);
	204	/* pass 1 check for bad entries */
	205	while ((name = strsep(&clone, " ")) && *name) {
	206	ca = tcp_ca_find(name);
	207	if (!ca) {
	208	ret = -ENOENT;
	209	goto out;
	210	}
	211	}
	212
	213	/* pass 2 clear */
	214	list_for_each_entry_rcu(ca, &tcp_cong_list, list)
	215	ca->non_restricted = 0;
	216
	217	/* pass 3 mark as allowed */
	218	while ((name = strsep(&val, " ")) && *name) {
	219	ca = tcp_ca_find(name);
	220	WARN_ON(!ca);
	221	if (ca)
	222	ca->non_restricted = 1;
	223	}
	224	out:
	225	spin_unlock(&tcp_cong_list_lock);
	226
	227	return ret;
	228	}
	229
	230
5f8ef48d	231	/* Change congestion control for socket */
6687e988	232	int tcp_set_congestion_control(struct sock sk, const char name)
5f8ef48d	233	{
6687e988	234	struct inet_connection_sock *icsk = inet_csk(sk);
5f8ef48d SH	235	struct tcp_congestion_ops *ca;
	236	int err = 0;
	237
	238	rcu_read_lock();
	239	ca = tcp_ca_find(name);
4d4d3d1e	240
35bfbc94	241	/* no change asking for existing value */
6687e988	242	if (ca == icsk->icsk_ca_ops)
5f8ef48d SH	243	goto out;
5f8ef48d SH	244
35bfbc94 SH	245	#ifdef CONFIG_KMOD
	246	/* not found attempt to autoload module */
	247	if (!ca && capable(CAP_SYS_MODULE)) {
	248	rcu_read_unlock();
	249	request_module("tcp_%s", name);
	250	rcu_read_lock();
	251	ca = tcp_ca_find(name);
	252	}
	253	#endif
5f8ef48d SH	254	if (!ca)
	255	err = -ENOENT;
	256
ce7bc3bf SH	257	else if (!(ca->non_restricted \|\| capable(CAP_NET_ADMIN)))
	258	err = -EPERM;
	259
5f8ef48d SH	260	else if (!try_module_get(ca->owner))
	261	err = -EBUSY;
	262
	263	else {
6687e988 ACM	264	tcp_cleanup_congestion_control(sk);
6687e988 ACM	265	icsk->icsk_ca_ops = ca;
4d4d3d1e SH	266
4d4d3d1e SH	267	if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init)
6687e988	268	icsk->icsk_ca_ops->init(sk);
5f8ef48d SH	269	}
	270	out:
	271	rcu_read_unlock();
	272	return err;
	273	}
	274
40efc6fa SH	275
	276	/*
	277	* Linear increase during slow start
	278	*/
	279	void tcp_slow_start(struct tcp_sock *tp)
	280	{
	281	if (sysctl_tcp_abc) {
	282	/* RFC3465: Slow Start
	283	* TCP sender SHOULD increase cwnd by the number of
	284	* previously unacknowledged bytes ACKed by each incoming
	285	* acknowledgment, provided the increase is not more than L
	286	*/
	287	if (tp->bytes_acked < tp->mss_cache)
	288	return;
	289
	290	/* We MAY increase by 2 if discovered delayed ack */
3fdf3f0c	291	if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache) {
40efc6fa SH	292	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
	293	tp->snd_cwnd++;
	294	}
	295	}
	296	tp->bytes_acked = 0;
	297
	298	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
	299	tp->snd_cwnd++;
	300	}
	301	EXPORT_SYMBOL_GPL(tcp_slow_start);
	302
317a76f9 SH	303	/*
	304	* TCP Reno congestion control
	305	* This is special case used for fallback as well.
	306	*/
	307	/* This is Jacobson's slow start and congestion avoidance.
	308	* SIGCOMM '88, p. 328.
	309	*/
6687e988	310	void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 rtt, u32 in_flight,
317a76f9 SH	311	int flag)
317a76f9 SH	312	{
6687e988 ACM	313	struct tcp_sock *tp = tcp_sk(sk);
6687e988 ACM	314
f4805ede	315	if (!tcp_is_cwnd_limited(sk, in_flight))
317a76f9 SH	316	return;
317a76f9 SH	317
7faffa1c	318	/* In "safe" area, increase. */
e905a9ed	319	if (tp->snd_cwnd <= tp->snd_ssthresh)
7faffa1c	320	tcp_slow_start(tp);
9772efb9	321
e905a9ed	322	/* In dangerous area, increase slowly. */
9772efb9	323	else if (sysctl_tcp_abc) {
e905a9ed YH	324	/* RFC3465: Appropriate Byte Count
	325	* increase once for each full cwnd acked
	326	*/
	327	if (tp->bytes_acked >= tp->snd_cwnd*tp->mss_cache) {
	328	tp->bytes_acked -= tp->snd_cwnd*tp->mss_cache;
	329	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
	330	tp->snd_cwnd++;
	331	}
	332	} else {
	333	/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd */
	334	if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
	335	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
	336	tp->snd_cwnd++;
	337	tp->snd_cwnd_cnt = 0;
	338	} else
	339	tp->snd_cwnd_cnt++;
	340	}
317a76f9 SH	341	}
	342	EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
	343
	344	/* Slow start threshold is half the congestion window (min 2) */
6687e988	345	u32 tcp_reno_ssthresh(struct sock *sk)
317a76f9	346	{
6687e988	347	const struct tcp_sock *tp = tcp_sk(sk);
317a76f9 SH	348	return max(tp->snd_cwnd >> 1U, 2U);
	349	}
	350	EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
	351
72dc5b92 SH	352	/* Lower bound on congestion window with halving. */
72dc5b92 SH	353	u32 tcp_reno_min_cwnd(const struct sock *sk)
317a76f9	354	{
6687e988	355	const struct tcp_sock *tp = tcp_sk(sk);
317a76f9 SH	356	return tp->snd_ssthresh/2;
	357	}
	358	EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd);
	359
	360	struct tcp_congestion_ops tcp_reno = {
	361	.name = "reno",
ce7bc3bf	362	.non_restricted = 1,
317a76f9 SH	363	.owner = THIS_MODULE,
	364	.ssthresh = tcp_reno_ssthresh,
	365	.cong_avoid = tcp_reno_cong_avoid,
	366	.min_cwnd = tcp_reno_min_cwnd,
	367	};
	368
5f8ef48d SH	369	/* Initial congestion control used (until SYN)
	370	* really reno under another name so we can tell difference
	371	* during tcp_set_default_congestion_control
	372	*/
	373	struct tcp_congestion_ops tcp_init_congestion_ops = {
	374	.name = "",
	375	.owner = THIS_MODULE,
	376	.ssthresh = tcp_reno_ssthresh,
	377	.cong_avoid = tcp_reno_cong_avoid,
	378	.min_cwnd = tcp_reno_min_cwnd,
	379	};
	380	EXPORT_SYMBOL_GPL(tcp_init_congestion_ops);