[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/config.h>
#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 algorthim 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 || !ca->min_cwnd) {
		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_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 tcp_sock *tp)
{
	struct tcp_congestion_ops *ca;

	if (tp->ca_ops != &tcp_init_congestion_ops)
		return;

	rcu_read_lock();
	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
		if (try_module_get(ca->owner)) {
			tp->ca_ops = ca;
			break;
		}

	}
	rcu_read_unlock();

	if (tp->ca_ops->init)
		tp->ca_ops->init(tp);
}

/* Manage refcounts on socket close. */
void tcp_cleanup_congestion_control(struct tcp_sock *tp)
{
	if (tp->ca_ops->release)
		tp->ca_ops->release(tp);
	module_put(tp->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) {
		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) {
		list_move(&ca->list, &tcp_cong_list);
		ret = 0;
	}
	spin_unlock(&tcp_cong_list_lock);

	return ret;
}

/* 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();
}

/* Change congestion control for socket */
int tcp_set_congestion_control(struct tcp_sock *tp, const char *name)
{
	struct tcp_congestion_ops *ca;
	int err = 0;

	rcu_read_lock();
	ca = tcp_ca_find(name);
	if (ca == tp->ca_ops)
		goto out;

	if (!ca)
		err = -ENOENT;

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

	else {
		tcp_cleanup_congestion_control(tp);
		tp->ca_ops = ca;
		if (tp->ca_ops->init)
			tp->ca_ops->init(tp);
	}
 out:
	rcu_read_unlock();
	return err;
}

/*
 * 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 tcp_sock *tp, u32 ack, u32 rtt, u32 in_flight,
			 int flag)
{
	if (in_flight < tp->snd_cwnd)
		return;

        if (tp->snd_cwnd <= tp->snd_ssthresh) {
                /* In "safe" area, increase. */
		if (tp->snd_cwnd < tp->snd_cwnd_clamp)
			tp->snd_cwnd++;
	} else {
                /* In dangerous area, increase slowly.
		 * 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 tcp_sock *tp)
{
	return max(tp->snd_cwnd >> 1U, 2U);
}
EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);

/* Lower bound on congestion window. */
u32 tcp_reno_min_cwnd(struct tcp_sock *tp)
{
	return tp->snd_ssthresh/2;
}
EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd);

struct tcp_congestion_ops tcp_reno = {
	.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
	9	#include <linux/config.h>
	10	#include <linux/module.h>
	11	#include <linux/mm.h>
	12	#include <linux/types.h>
	13	#include <linux/list.h>
	14	#include <net/tcp.h>
	15
	16	static DEFINE_SPINLOCK(tcp_cong_list_lock);
	17	static LIST_HEAD(tcp_cong_list);
	18
	19	/* Simple linear search, don't expect many entries! */
	20	static struct tcp_congestion_ops tcp_ca_find(const char name)
	21	{
	22	struct tcp_congestion_ops *e;
	23
5f8ef48d	24	list_for_each_entry_rcu(e, &tcp_cong_list, list) {
317a76f9 SH	25	if (strcmp(e->name, name) == 0)
	26	return e;
	27	}
	28
	29	return NULL;
	30	}
	31
	32	/*
	33	* Attach new congestion control algorthim to the list
	34	* of available options.
	35	*/
	36	int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
	37	{
	38	int ret = 0;
	39
	40	/* all algorithms must implement ssthresh and cong_avoid ops */
	41	if (!ca->ssthresh \|\| !ca->cong_avoid \|\| !ca->min_cwnd) {
	42	printk(KERN_ERR "TCP %s does not implement required ops\n",
	43	ca->name);
	44	return -EINVAL;
	45	}
	46
	47	spin_lock(&tcp_cong_list_lock);
	48	if (tcp_ca_find(ca->name)) {
	49	printk(KERN_NOTICE "TCP %s already registered\n", ca->name);
	50	ret = -EEXIST;
	51	} else {
	52	list_add_rcu(&ca->list, &tcp_cong_list);
	53	printk(KERN_INFO "TCP %s registered\n", ca->name);
	54	}
	55	spin_unlock(&tcp_cong_list_lock);
	56
	57	return ret;
	58	}
	59	EXPORT_SYMBOL_GPL(tcp_register_congestion_control);
	60
	61	/*
	62	* Remove congestion control algorithm, called from
	63	* the module's remove function. Module ref counts are used
	64	* to ensure that this can't be done till all sockets using
	65	* that method are closed.
	66	*/
	67	void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
	68	{
	69	spin_lock(&tcp_cong_list_lock);
	70	list_del_rcu(&ca->list);
	71	spin_unlock(&tcp_cong_list_lock);
	72	}
	73	EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
	74
	75	/* Assign choice of congestion control. */
	76	void tcp_init_congestion_control(struct tcp_sock *tp)
	77	{
	78	struct tcp_congestion_ops *ca;
	79
5f8ef48d SH	80	if (tp->ca_ops != &tcp_init_congestion_ops)
	81	return;
	82
317a76f9 SH	83	rcu_read_lock();
	84	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
	85	if (try_module_get(ca->owner)) {
	86	tp->ca_ops = ca;
	87	break;
	88	}
	89
	90	}
	91	rcu_read_unlock();
	92
	93	if (tp->ca_ops->init)
	94	tp->ca_ops->init(tp);
	95	}
	96
	97	/* Manage refcounts on socket close. */
	98	void tcp_cleanup_congestion_control(struct tcp_sock *tp)
	99	{
	100	if (tp->ca_ops->release)
	101	tp->ca_ops->release(tp);
	102	module_put(tp->ca_ops->owner);
	103	}
	104
	105	/* Used by sysctl to change default congestion control */
	106	int tcp_set_default_congestion_control(const char *name)
	107	{
	108	struct tcp_congestion_ops *ca;
	109	int ret = -ENOENT;
	110
	111	spin_lock(&tcp_cong_list_lock);
	112	ca = tcp_ca_find(name);
	113	#ifdef CONFIG_KMOD
	114	if (!ca) {
	115	spin_unlock(&tcp_cong_list_lock);
	116
	117	request_module("tcp_%s", name);
	118	spin_lock(&tcp_cong_list_lock);
	119	ca = tcp_ca_find(name);
	120	}
	121	#endif
	122
	123	if (ca) {
	124	list_move(&ca->list, &tcp_cong_list);
	125	ret = 0;
	126	}
	127	spin_unlock(&tcp_cong_list_lock);
	128
	129	return ret;
	130	}
	131
	132	/* Get current default congestion control */
	133	void tcp_get_default_congestion_control(char *name)
	134	{
	135	struct tcp_congestion_ops *ca;
	136	/* We will always have reno... */
	137	BUG_ON(list_empty(&tcp_cong_list));
	138
	139	rcu_read_lock();
	140	ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list);
	141	strncpy(name, ca->name, TCP_CA_NAME_MAX);
	142	rcu_read_unlock();
	143	}
	144
5f8ef48d SH	145	/* Change congestion control for socket */
	146	int tcp_set_congestion_control(struct tcp_sock tp, const char name)
	147	{
	148	struct tcp_congestion_ops *ca;
	149	int err = 0;
	150
	151	rcu_read_lock();
	152	ca = tcp_ca_find(name);
	153	if (ca == tp->ca_ops)
	154	goto out;
	155
	156	if (!ca)
	157	err = -ENOENT;
	158
	159	else if (!try_module_get(ca->owner))
	160	err = -EBUSY;
	161
	162	else {
	163	tcp_cleanup_congestion_control(tp);
	164	tp->ca_ops = ca;
	165	if (tp->ca_ops->init)
	166	tp->ca_ops->init(tp);
	167	}
	168	out:
	169	rcu_read_unlock();
	170	return err;
	171	}
	172
317a76f9 SH	173	/*
	174	* TCP Reno congestion control
	175	* This is special case used for fallback as well.
	176	*/
	177	/* This is Jacobson's slow start and congestion avoidance.
	178	* SIGCOMM '88, p. 328.
	179	*/
	180	void tcp_reno_cong_avoid(struct tcp_sock *tp, u32 ack, u32 rtt, u32 in_flight,
	181	int flag)
	182	{
	183	if (in_flight < tp->snd_cwnd)
	184	return;
	185
	186	if (tp->snd_cwnd <= tp->snd_ssthresh) {
	187	/* In "safe" area, increase. */
	188	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
	189	tp->snd_cwnd++;
	190	} else {
	191	/* In dangerous area, increase slowly.
	192	* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
	193	*/
	194	if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
	195	if (tp->snd_cwnd < tp->snd_cwnd_clamp)
	196	tp->snd_cwnd++;
	197	tp->snd_cwnd_cnt = 0;
	198	} else
	199	tp->snd_cwnd_cnt++;
	200	}
	201	}
	202	EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
	203
	204	/* Slow start threshold is half the congestion window (min 2) */
	205	u32 tcp_reno_ssthresh(struct tcp_sock *tp)
	206	{
	207	return max(tp->snd_cwnd >> 1U, 2U);
	208	}
	209	EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
	210
	211	/* Lower bound on congestion window. */
	212	u32 tcp_reno_min_cwnd(struct tcp_sock *tp)
	213	{
	214	return tp->snd_ssthresh/2;
	215	}
	216	EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd);
	217
	218	struct tcp_congestion_ops tcp_reno = {
	219	.name = "reno",
	220	.owner = THIS_MODULE,
	221	.ssthresh = tcp_reno_ssthresh,
	222	.cong_avoid = tcp_reno_cong_avoid,
	223	.min_cwnd = tcp_reno_min_cwnd,
	224	};
	225
5f8ef48d SH	226	/* Initial congestion control used (until SYN)
	227	* really reno under another name so we can tell difference
	228	* during tcp_set_default_congestion_control
	229	*/
	230	struct tcp_congestion_ops tcp_init_congestion_ops = {
	231	.name = "",
	232	.owner = THIS_MODULE,
	233	.ssthresh = tcp_reno_ssthresh,
	234	.cong_avoid = tcp_reno_cong_avoid,
	235	.min_cwnd = tcp_reno_min_cwnd,
	236	};
	237	EXPORT_SYMBOL_GPL(tcp_init_congestion_ops);