[linux-2.6-block.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>
 */

#define pr_fmt(fmt) "TCP: " fmt

#include <linux/module.h>
#include <linux/mm.h>
#include <linux/types.h>
#include <linux/list.h>
#include <linux/gfp.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) {
		pr_err("%s does not implement required ops\n", ca->name);
		return -EINVAL;
	}

	spin_lock(&tcp_cong_list_lock);
	if (tcp_ca_find(ca->name)) {
		pr_notice("%s already registered\n", ca->name);
		ret = -EEXIST;
	} else {
		list_add_tail_rcu(&ca->list, &tcp_cong_list);
		pr_info("%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_MODULES
	if (!ca && capable(CAP_NET_ADMIN)) {
		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 *saved_clone, *clone, *name;
	int ret = 0;

	saved_clone = 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);
	kfree(saved_clone);

	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_MODULES
	/* not found attempt to autoload module */
	if (!ca && capable(CAP_NET_ADMIN)) {
		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;
}

/* RFC2861 Check whether we are limited by application or congestion window
 * This is the inverse of cwnd check in tcp_tso_should_defer
 */
bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight)
{
	const struct tcp_sock *tp = tcp_sk(sk);
	u32 left;

	if (in_flight >= tp->snd_cwnd)
		return true;

	left = tp->snd_cwnd - in_flight;
	if (sk_can_gso(sk) &&
	    left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd &&
	    left * tp->mss_cache < sk->sk_gso_max_size &&
	    left < sk->sk_gso_max_segs)
		return true;
	return left <= tcp_max_tso_deferred_mss(tp);
}
EXPORT_SYMBOL_GPL(tcp_is_cwnd_limited);

/*
 * 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 */
	unsigned int delta = 0;

	/* 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;
		delta++;
	}
	tp->snd_cwnd = min(tp->snd_cwnd + delta, tp->snd_cwnd_clamp);
}
EXPORT_SYMBOL_GPL(tcp_slow_start);

/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w) */
void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w)
{
	if (tp->snd_cwnd_cnt >= w) {
		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_cong_avoid_ai);

/*
 * 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 in_flight)
{
	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 {
		tcp_cong_avoid_ai(tp, tp->snd_cwnd);
	}
}
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 <shemminger@osdl.org>
	7	*/
	8
afd46503 JP	9	#define pr_fmt(fmt) "TCP: " fmt
afd46503 JP	10
317a76f9 SH	11	#include <linux/module.h>
	12	#include <linux/mm.h>
	13	#include <linux/types.h>
	14	#include <linux/list.h>
5a0e3ad6	15	#include <linux/gfp.h>
317a76f9 SH	16	#include <net/tcp.h>
317a76f9 SH	17
886236c1 JH	18	int sysctl_tcp_max_ssthresh = 0;
886236c1 JH	19
317a76f9 SH	20	static DEFINE_SPINLOCK(tcp_cong_list_lock);
	21	static LIST_HEAD(tcp_cong_list);
	22
	23	/* Simple linear search, don't expect many entries! */
	24	static struct tcp_congestion_ops tcp_ca_find(const char name)
	25	{
	26	struct tcp_congestion_ops *e;
	27
5f8ef48d	28	list_for_each_entry_rcu(e, &tcp_cong_list, list) {
317a76f9 SH	29	if (strcmp(e->name, name) == 0)
	30	return e;
	31	}
	32
	33	return NULL;
	34	}
	35
	36	/*
d08df601	37	* Attach new congestion control algorithm to the list
317a76f9 SH	38	* of available options.
	39	*/
	40	int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
	41	{
	42	int ret = 0;
	43
	44	/* all algorithms must implement ssthresh and cong_avoid ops */
72dc5b92	45	if (!ca->ssthresh \|\| !ca->cong_avoid) {
afd46503	46	pr_err("%s does not implement required ops\n", ca->name);
317a76f9 SH	47	return -EINVAL;
	48	}
	49
	50	spin_lock(&tcp_cong_list_lock);
	51	if (tcp_ca_find(ca->name)) {
afd46503	52	pr_notice("%s already registered\n", ca->name);
317a76f9 SH	53	ret = -EEXIST;
317a76f9 SH	54	} else {
3d2573f7	55	list_add_tail_rcu(&ca->list, &tcp_cong_list);
afd46503	56	pr_info("%s registered\n", ca->name);
317a76f9 SH	57	}
	58	spin_unlock(&tcp_cong_list_lock);
	59
	60	return ret;
	61	}
	62	EXPORT_SYMBOL_GPL(tcp_register_congestion_control);
	63
	64	/*
	65	* Remove congestion control algorithm, called from
	66	* the module's remove function. Module ref counts are used
	67	* to ensure that this can't be done till all sockets using
	68	* that method are closed.
	69	*/
	70	void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
	71	{
	72	spin_lock(&tcp_cong_list_lock);
	73	list_del_rcu(&ca->list);
	74	spin_unlock(&tcp_cong_list_lock);
	75	}
	76	EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
	77
	78	/* Assign choice of congestion control. */
6687e988	79	void tcp_init_congestion_control(struct sock *sk)
317a76f9	80	{
6687e988	81	struct inet_connection_sock *icsk = inet_csk(sk);
317a76f9 SH	82	struct tcp_congestion_ops *ca;
317a76f9 SH	83
4d4d3d1e SH	84	/* if no choice made yet assign the current value set as default */
	85	if (icsk->icsk_ca_ops == &tcp_init_congestion_ops) {
	86	rcu_read_lock();
	87	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
	88	if (try_module_get(ca->owner)) {
	89	icsk->icsk_ca_ops = ca;
	90	break;
	91	}
5f8ef48d	92
4d4d3d1e	93	/* fallback to next available */
317a76f9	94	}
4d4d3d1e	95	rcu_read_unlock();
317a76f9	96	}
317a76f9	97
6687e988 ACM	98	if (icsk->icsk_ca_ops->init)
6687e988 ACM	99	icsk->icsk_ca_ops->init(sk);
317a76f9 SH	100	}
	101
	102	/* Manage refcounts on socket close. */
6687e988	103	void tcp_cleanup_congestion_control(struct sock *sk)
317a76f9	104	{
6687e988 ACM	105	struct inet_connection_sock *icsk = inet_csk(sk);
	106
	107	if (icsk->icsk_ca_ops->release)
	108	icsk->icsk_ca_ops->release(sk);
	109	module_put(icsk->icsk_ca_ops->owner);
317a76f9 SH	110	}
	111
	112	/* Used by sysctl to change default congestion control */
	113	int tcp_set_default_congestion_control(const char *name)
	114	{
	115	struct tcp_congestion_ops *ca;
	116	int ret = -ENOENT;
	117
	118	spin_lock(&tcp_cong_list_lock);
	119	ca = tcp_ca_find(name);
95a5afca	120	#ifdef CONFIG_MODULES
a8f80e8f	121	if (!ca && capable(CAP_NET_ADMIN)) {
317a76f9 SH	122	spin_unlock(&tcp_cong_list_lock);
	123
	124	request_module("tcp_%s", name);
	125	spin_lock(&tcp_cong_list_lock);
	126	ca = tcp_ca_find(name);
	127	}
	128	#endif
	129
	130	if (ca) {
164891aa	131	ca->flags \|= TCP_CONG_NON_RESTRICTED; /* default is always allowed */
317a76f9 SH	132	list_move(&ca->list, &tcp_cong_list);
	133	ret = 0;
	134	}
	135	spin_unlock(&tcp_cong_list_lock);
	136
	137	return ret;
	138	}
	139
b1736a71 SH	140	/* Set default value from kernel configuration at bootup */
	141	static int __init tcp_congestion_default(void)
	142	{
	143	return tcp_set_default_congestion_control(CONFIG_DEFAULT_TCP_CONG);
	144	}
	145	late_initcall(tcp_congestion_default);
	146
	147
3ff825b2 SH	148	/* Build string with list of available congestion control values */
	149	void tcp_get_available_congestion_control(char *buf, size_t maxlen)
	150	{
	151	struct tcp_congestion_ops *ca;
	152	size_t offs = 0;
	153
	154	rcu_read_lock();
	155	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
	156	offs += snprintf(buf + offs, maxlen - offs,
	157	"%s%s",
	158	offs == 0 ? "" : " ", ca->name);
	159
	160	}
	161	rcu_read_unlock();
	162	}
	163
317a76f9 SH	164	/* Get current default congestion control */
	165	void tcp_get_default_congestion_control(char *name)
	166	{
	167	struct tcp_congestion_ops *ca;
	168	/* We will always have reno... */
	169	BUG_ON(list_empty(&tcp_cong_list));
	170
	171	rcu_read_lock();
	172	ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list);
	173	strncpy(name, ca->name, TCP_CA_NAME_MAX);
	174	rcu_read_unlock();
	175	}
	176
ce7bc3bf SH	177	/* Built list of non-restricted congestion control values */
	178	void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)
	179	{
	180	struct tcp_congestion_ops *ca;
	181	size_t offs = 0;
	182
	183	*buf = '\0';
	184	rcu_read_lock();
	185	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
164891aa	186	if (!(ca->flags & TCP_CONG_NON_RESTRICTED))
ce7bc3bf SH	187	continue;
	188	offs += snprintf(buf + offs, maxlen - offs,
	189	"%s%s",
	190	offs == 0 ? "" : " ", ca->name);
	191
	192	}
	193	rcu_read_unlock();
	194	}
	195
	196	/* Change list of non-restricted congestion control */
	197	int tcp_set_allowed_congestion_control(char *val)
	198	{
	199	struct tcp_congestion_ops *ca;
c34186ed	200	char saved_clone, clone, *name;
ce7bc3bf SH	201	int ret = 0;
ce7bc3bf SH	202
c34186ed	203	saved_clone = clone = kstrdup(val, GFP_USER);
ce7bc3bf SH	204	if (!clone)
	205	return -ENOMEM;
	206
	207	spin_lock(&tcp_cong_list_lock);
	208	/* pass 1 check for bad entries */
	209	while ((name = strsep(&clone, " ")) && *name) {
	210	ca = tcp_ca_find(name);
	211	if (!ca) {
	212	ret = -ENOENT;
	213	goto out;
	214	}
	215	}
	216
164891aa	217	/* pass 2 clear old values */
ce7bc3bf	218	list_for_each_entry_rcu(ca, &tcp_cong_list, list)
164891aa	219	ca->flags &= ~TCP_CONG_NON_RESTRICTED;
ce7bc3bf SH	220
	221	/* pass 3 mark as allowed */
	222	while ((name = strsep(&val, " ")) && *name) {
	223	ca = tcp_ca_find(name);
	224	WARN_ON(!ca);
	225	if (ca)
164891aa	226	ca->flags \|= TCP_CONG_NON_RESTRICTED;
ce7bc3bf SH	227	}
	228	out:
	229	spin_unlock(&tcp_cong_list_lock);
c34186ed	230	kfree(saved_clone);
ce7bc3bf SH	231
	232	return ret;
	233	}
	234
	235
5f8ef48d	236	/* Change congestion control for socket */
6687e988	237	int tcp_set_congestion_control(struct sock sk, const char name)
5f8ef48d	238	{
6687e988	239	struct inet_connection_sock *icsk = inet_csk(sk);
5f8ef48d SH	240	struct tcp_congestion_ops *ca;
	241	int err = 0;
	242
	243	rcu_read_lock();
	244	ca = tcp_ca_find(name);
4d4d3d1e	245
35bfbc94	246	/* no change asking for existing value */
6687e988	247	if (ca == icsk->icsk_ca_ops)
5f8ef48d SH	248	goto out;
5f8ef48d SH	249
95a5afca	250	#ifdef CONFIG_MODULES
35bfbc94	251	/* not found attempt to autoload module */
a8f80e8f	252	if (!ca && capable(CAP_NET_ADMIN)) {
35bfbc94 SH	253	rcu_read_unlock();
	254	request_module("tcp_%s", name);
	255	rcu_read_lock();
	256	ca = tcp_ca_find(name);
	257	}
	258	#endif
5f8ef48d SH	259	if (!ca)
	260	err = -ENOENT;
	261
164891aa	262	else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) \|\| capable(CAP_NET_ADMIN)))
ce7bc3bf SH	263	err = -EPERM;
ce7bc3bf SH	264
5f8ef48d SH	265	else if (!try_module_get(ca->owner))
	266	err = -EBUSY;
	267
	268	else {
6687e988 ACM	269	tcp_cleanup_congestion_control(sk);
6687e988 ACM	270	icsk->icsk_ca_ops = ca;
4d4d3d1e SH	271
4d4d3d1e SH	272	if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init)
6687e988	273	icsk->icsk_ca_ops->init(sk);
5f8ef48d SH	274	}
	275	out:
	276	rcu_read_unlock();
	277	return err;
	278	}
	279
cea14e0e IJ	280	/* RFC2861 Check whether we are limited by application or congestion window
	281	* This is the inverse of cwnd check in tcp_tso_should_defer
	282	*/
a2a385d6	283	bool tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight)
cea14e0e IJ	284	{
	285	const struct tcp_sock *tp = tcp_sk(sk);
	286	u32 left;
	287
	288	if (in_flight >= tp->snd_cwnd)
a2a385d6	289	return true;
cea14e0e	290
cea14e0e	291	left = tp->snd_cwnd - in_flight;
ce447eb9	292	if (sk_can_gso(sk) &&
246eb2af	293	left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd &&
1485348d BH	294	left * tp->mss_cache < sk->sk_gso_max_size &&
1485348d BH	295	left < sk->sk_gso_max_segs)
a2a385d6	296	return true;
6b5a5c0d	297	return left <= tcp_max_tso_deferred_mss(tp);
cea14e0e IJ	298	}
cea14e0e IJ	299	EXPORT_SYMBOL_GPL(tcp_is_cwnd_limited);
40efc6fa SH	300
40efc6fa SH	301	/*
a02ba041 SH	302	* Slow start is used when congestion window is less than slow start
	303	* threshold. This version implements the basic RFC2581 version
	304	* and optionally supports:
	305	* RFC3742 Limited Slow Start - growth limited to max_ssthresh
	306	* RFC3465 Appropriate Byte Counting - growth limited by bytes acknowledged
40efc6fa SH	307	*/
	308	void tcp_slow_start(struct tcp_sock *tp)
	309	{
a02ba041	310	int cnt; /* increase in packets */
9dc27415	311	unsigned int delta = 0;
a02ba041 SH	312
	313	/* RFC3465: ABC Slow start
	314	* Increase only after a full MSS of bytes is acked
	315	*
	316	* TCP sender SHOULD increase cwnd by the number of
	317	* previously unacknowledged bytes ACKed by each incoming
	318	* acknowledgment, provided the increase is not more than L
	319	*/
	320	if (sysctl_tcp_abc && tp->bytes_acked < tp->mss_cache)
	321	return;
	322
	323	if (sysctl_tcp_max_ssthresh > 0 && tp->snd_cwnd > sysctl_tcp_max_ssthresh)
	324	cnt = sysctl_tcp_max_ssthresh >> 1; /* limited slow start */
886236c1	325	else
a02ba041	326	cnt = tp->snd_cwnd; /* exponential increase */
886236c1	327
a02ba041 SH	328	/* RFC3465: ABC
	329	* We MAY increase by 2 if discovered delayed ack
	330	*/
886236c1 JH	331	if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache)
886236c1 JH	332	cnt <<= 1;
40efc6fa SH	333	tp->bytes_acked = 0;
40efc6fa SH	334
886236c1 JH	335	tp->snd_cwnd_cnt += cnt;
	336	while (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
	337	tp->snd_cwnd_cnt -= tp->snd_cwnd;
9dc27415	338	delta++;
886236c1	339	}
9dc27415	340	tp->snd_cwnd = min(tp->snd_cwnd + delta, tp->snd_cwnd_clamp);
40efc6fa SH	341	}
	342	EXPORT_SYMBOL_GPL(tcp_slow_start);
	343
758ce5c8 IJ	344	/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w) */
	345	void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w)
	346	{
	347	if (tp->snd_cwnd_cnt >= w) {
	348	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
	349	tp->snd_cwnd++;
	350	tp->snd_cwnd_cnt = 0;
	351	} else {
	352	tp->snd_cwnd_cnt++;
	353	}
	354	}
	355	EXPORT_SYMBOL_GPL(tcp_cong_avoid_ai);
	356
317a76f9 SH	357	/*
	358	* TCP Reno congestion control
	359	* This is special case used for fallback as well.
	360	*/
	361	/* This is Jacobson's slow start and congestion avoidance.
	362	* SIGCOMM '88, p. 328.
	363	*/
c3a05c60	364	void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
317a76f9	365	{
6687e988 ACM	366	struct tcp_sock *tp = tcp_sk(sk);
6687e988 ACM	367
f4805ede	368	if (!tcp_is_cwnd_limited(sk, in_flight))
317a76f9 SH	369	return;
317a76f9 SH	370
7faffa1c	371	/* In "safe" area, increase. */
e905a9ed	372	if (tp->snd_cwnd <= tp->snd_ssthresh)
7faffa1c	373	tcp_slow_start(tp);
9772efb9	374
e905a9ed	375	/* In dangerous area, increase slowly. */
9772efb9	376	else if (sysctl_tcp_abc) {
e905a9ed YH	377	/* RFC3465: Appropriate Byte Count
	378	* increase once for each full cwnd acked
	379	*/
	380	if (tp->bytes_acked >= tp->snd_cwnd*tp->mss_cache) {
	381	tp->bytes_acked -= tp->snd_cwnd*tp->mss_cache;
	382	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
	383	tp->snd_cwnd++;
	384	}
	385	} else {
758ce5c8	386	tcp_cong_avoid_ai(tp, tp->snd_cwnd);
e905a9ed	387	}
317a76f9 SH	388	}
	389	EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
	390
	391	/* Slow start threshold is half the congestion window (min 2) */
6687e988	392	u32 tcp_reno_ssthresh(struct sock *sk)
317a76f9	393	{
6687e988	394	const struct tcp_sock *tp = tcp_sk(sk);
317a76f9 SH	395	return max(tp->snd_cwnd >> 1U, 2U);
	396	}
	397	EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
	398
72dc5b92 SH	399	/* Lower bound on congestion window with halving. */
72dc5b92 SH	400	u32 tcp_reno_min_cwnd(const struct sock *sk)
317a76f9	401	{
6687e988	402	const struct tcp_sock *tp = tcp_sk(sk);
317a76f9 SH	403	return tp->snd_ssthresh/2;
	404	}
	405	EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd);
	406
	407	struct tcp_congestion_ops tcp_reno = {
164891aa	408	.flags = TCP_CONG_NON_RESTRICTED,
317a76f9 SH	409	.name = "reno",
	410	.owner = THIS_MODULE,
	411	.ssthresh = tcp_reno_ssthresh,
	412	.cong_avoid = tcp_reno_cong_avoid,
	413	.min_cwnd = tcp_reno_min_cwnd,
	414	};
	415
5f8ef48d SH	416	/* Initial congestion control used (until SYN)
	417	* really reno under another name so we can tell difference
	418	* during tcp_set_default_congestion_control
	419	*/
	420	struct tcp_congestion_ops tcp_init_congestion_ops = {
	421	.name = "",
	422	.owner = THIS_MODULE,
	423	.ssthresh = tcp_reno_ssthresh,
	424	.cong_avoid = tcp_reno_cong_avoid,
	425	.min_cwnd = tcp_reno_min_cwnd,
	426	};
	427	EXPORT_SYMBOL_GPL(tcp_init_congestion_ops);