[mirror_ubuntu-eoan-kernel.git] / net / ipv4 / tcp_cong.c

/*
 * Pluggable TCP congestion control support and newReno
 * congestion control.
 * Based on ideas from I/O scheduler support 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 <linux/jhash.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;
}

/* Must be called with rcu lock held */
static struct tcp_congestion_ops *tcp_ca_find_autoload(struct net *net,
						       const char *name)
{
	struct tcp_congestion_ops *ca = tcp_ca_find(name);

#ifdef CONFIG_MODULES
	if (!ca && capable(CAP_NET_ADMIN)) {
		rcu_read_unlock();
		request_module("tcp_%s", name);
		rcu_read_lock();
		ca = tcp_ca_find(name);
	}
#endif
	return ca;
}

/* Simple linear search, not much in here. */
struct tcp_congestion_ops *tcp_ca_find_key(u32 key)
{
	struct tcp_congestion_ops *e;

	list_for_each_entry_rcu(e, &tcp_cong_list, list) {
		if (e->key == key)
			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 these */
	if (!ca->ssthresh || !ca->undo_cwnd ||
	    !(ca->cong_avoid || ca->cong_control)) {
		pr_err("%s does not implement required ops\n", ca->name);
		return -EINVAL;
	}

	ca->key = jhash(ca->name, sizeof(ca->name), strlen(ca->name));

	spin_lock(&tcp_cong_list_lock);
	if (ca->key == TCP_CA_UNSPEC || tcp_ca_find_key(ca->key)) {
		pr_notice("%s already registered or non-unique key\n",
			  ca->name);
		ret = -EEXIST;
	} else {
		list_add_tail_rcu(&ca->list, &tcp_cong_list);
		pr_debug("%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);

	/* Wait for outstanding readers to complete before the
	 * module gets removed entirely.
	 *
	 * A try_module_get() should fail by now as our module is
	 * in "going" state since no refs are held anymore and
	 * module_exit() handler being called.
	 */
	synchronize_rcu();
}
EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);

u32 tcp_ca_get_key_by_name(struct net *net, const char *name, bool *ecn_ca)
{
	const struct tcp_congestion_ops *ca;
	u32 key = TCP_CA_UNSPEC;

	might_sleep();

	rcu_read_lock();
	ca = tcp_ca_find_autoload(net, name);
	if (ca) {
		key = ca->key;
		*ecn_ca = ca->flags & TCP_CONG_NEEDS_ECN;
	}
	rcu_read_unlock();

	return key;
}
EXPORT_SYMBOL_GPL(tcp_ca_get_key_by_name);

char *tcp_ca_get_name_by_key(u32 key, char *buffer)
{
	const struct tcp_congestion_ops *ca;
	char *ret = NULL;

	rcu_read_lock();
	ca = tcp_ca_find_key(key);
	if (ca)
		ret = strncpy(buffer, ca->name,
			      TCP_CA_NAME_MAX);
	rcu_read_unlock();

	return ret;
}
EXPORT_SYMBOL_GPL(tcp_ca_get_name_by_key);

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

	rcu_read_lock();
	ca = rcu_dereference(net->ipv4.tcp_congestion_control);
	if (unlikely(!try_module_get(ca->owner)))
		ca = &tcp_reno;
	icsk->icsk_ca_ops = ca;
	rcu_read_unlock();

	memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
	if (ca->flags & TCP_CONG_NEEDS_ECN)
		INET_ECN_xmit(sk);
	else
		INET_ECN_dontxmit(sk);
}

void tcp_init_congestion_control(struct sock *sk)
{
	const struct inet_connection_sock *icsk = inet_csk(sk);

	tcp_sk(sk)->prior_ssthresh = 0;
	if (icsk->icsk_ca_ops->init)
		icsk->icsk_ca_ops->init(sk);
	if (tcp_ca_needs_ecn(sk))
		INET_ECN_xmit(sk);
	else
		INET_ECN_dontxmit(sk);
}

static void tcp_reinit_congestion_control(struct sock *sk,
					  const struct tcp_congestion_ops *ca)
{
	struct inet_connection_sock *icsk = inet_csk(sk);

	tcp_cleanup_congestion_control(sk);
	icsk->icsk_ca_ops = ca;
	icsk->icsk_ca_setsockopt = 1;
	memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));

	if (sk->sk_state != TCP_CLOSE)
		tcp_init_congestion_control(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(struct net *net, const char *name)
{
	struct tcp_congestion_ops *ca;
	const struct tcp_congestion_ops *prev;
	int ret;

	rcu_read_lock();
	ca = tcp_ca_find_autoload(net, name);
	if (!ca) {
		ret = -ENOENT;
	} else if (!try_module_get(ca->owner)) {
		ret = -EBUSY;
	} else {
		prev = xchg(&net->ipv4.tcp_congestion_control, ca);
		if (prev)
			module_put(prev->owner);

		ca->flags |= TCP_CONG_NON_RESTRICTED;
		ret = 0;
	}
	rcu_read_unlock();

	return ret;
}

/* Set default value from kernel configuration at bootup */
static int __init tcp_congestion_default(void)
{
	return tcp_set_default_congestion_control(&init_net,
						  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(struct net *net, char *name)
{
	const struct tcp_congestion_ops *ca;

	rcu_read_lock();
	ca = rcu_dereference(net->ipv4.tcp_congestion_control);
	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. If load is false, then it is the
 * responsibility of the caller to call tcp_init_congestion_control or
 * tcp_reinit_congestion_control (if the current congestion control was
 * already initialized.
 */
int tcp_set_congestion_control(struct sock *sk, const char *name, bool load, bool reinit)
{
	struct inet_connection_sock *icsk = inet_csk(sk);
	const struct tcp_congestion_ops *ca;
	int err = 0;

	if (icsk->icsk_ca_dst_locked)
		return -EPERM;

	rcu_read_lock();
	if (!load)
		ca = tcp_ca_find(name);
	else
		ca = tcp_ca_find_autoload(sock_net(sk), name);

	/* No change asking for existing value */
	if (ca == icsk->icsk_ca_ops) {
		icsk->icsk_ca_setsockopt = 1;
		goto out;
	}

	if (!ca) {
		err = -ENOENT;
	} else if (!load) {
		const struct tcp_congestion_ops *old_ca = icsk->icsk_ca_ops;

		if (try_module_get(ca->owner)) {
			if (reinit) {
				tcp_reinit_congestion_control(sk, ca);
			} else {
				icsk->icsk_ca_ops = ca;
				module_put(old_ca->owner);
			}
		} else {
			err = -EBUSY;
		}
	} else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) ||
		     ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))) {
		err = -EPERM;
	} else if (!try_module_get(ca->owner)) {
		err = -EBUSY;
	} else {
		tcp_reinit_congestion_control(sk, ca);
	}
 out:
	rcu_read_unlock();
	return err;
}

/* Slow start is used when congestion window is no greater than the slow start
 * threshold. We base on RFC2581 and also handle stretch ACKs properly.
 * We do not implement RFC3465 Appropriate Byte Counting (ABC) per se but
 * something better;) a packet is only considered (s)acked in its entirety to
 * defend the ACK attacks described in the RFC. Slow start processes a stretch
 * ACK of degree N as if N acks of degree 1 are received back to back except
 * ABC caps N to 2. Slow start exits when cwnd grows over ssthresh and
 * returns the leftover acks to adjust cwnd in congestion avoidance mode.
 */
u32 tcp_slow_start(struct tcp_sock *tp, u32 acked)
{
	u32 cwnd = min(tp->snd_cwnd + acked, tp->snd_ssthresh);

	acked -= cwnd - tp->snd_cwnd;
	tp->snd_cwnd = min(cwnd, tp->snd_cwnd_clamp);

	return acked;
}
EXPORT_SYMBOL_GPL(tcp_slow_start);

/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w),
 * for every packet that was ACKed.
 */
void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked)
{
	/* If credits accumulated at a higher w, apply them gently now. */
	if (tp->snd_cwnd_cnt >= w) {
		tp->snd_cwnd_cnt = 0;
		tp->snd_cwnd++;
	}

	tp->snd_cwnd_cnt += acked;
	if (tp->snd_cwnd_cnt >= w) {
		u32 delta = tp->snd_cwnd_cnt / w;

		tp->snd_cwnd_cnt -= delta * w;
		tp->snd_cwnd += delta;
	}
	tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_cwnd_clamp);
}
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 acked)
{
	struct tcp_sock *tp = tcp_sk(sk);

	if (!tcp_is_cwnd_limited(sk))
		return;

	/* In "safe" area, increase. */
	if (tcp_in_slow_start(tp)) {
		acked = tcp_slow_start(tp, acked);
		if (!acked)
			return;
	}
	/* In dangerous area, increase slowly. */
	tcp_cong_avoid_ai(tp, tp->snd_cwnd, acked);
}
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);

u32 tcp_reno_undo_cwnd(struct sock *sk)
{
	const struct tcp_sock *tp = tcp_sk(sk);

	return max(tp->snd_cwnd, tp->prior_cwnd);
}
EXPORT_SYMBOL_GPL(tcp_reno_undo_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,
	.undo_cwnd	= tcp_reno_undo_cwnd,
};
Commit	Line	Data
317a76f9	1	/*
b92022f3	2	* Pluggable TCP congestion control support and newReno
317a76f9	3	* congestion control.
02582e9b	4	* Based on ideas from I/O scheduler support and Web100.
317a76f9 SH	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>
c5c6a8ab	16	#include <linux/jhash.h>
317a76f9 SH	17	#include <net/tcp.h>
	18
	19	static DEFINE_SPINLOCK(tcp_cong_list_lock);
	20	static LIST_HEAD(tcp_cong_list);
	21
	22	/* Simple linear search, don't expect many entries! */
	23	static struct tcp_congestion_ops tcp_ca_find(const char name)
	24	{
	25	struct tcp_congestion_ops *e;
	26
5f8ef48d	27	list_for_each_entry_rcu(e, &tcp_cong_list, list) {
317a76f9 SH	28	if (strcmp(e->name, name) == 0)
	29	return e;
	30	}
	31
	32	return NULL;
	33	}
	34
c5c6a8ab	35	/* Must be called with rcu lock held */
6670e152 SH	36	static struct tcp_congestion_ops tcp_ca_find_autoload(struct net net,
6670e152 SH	37	const char *name)
c5c6a8ab	38	{
6670e152 SH	39	struct tcp_congestion_ops *ca = tcp_ca_find(name);
6670e152 SH	40
c5c6a8ab DB	41	#ifdef CONFIG_MODULES
	42	if (!ca && capable(CAP_NET_ADMIN)) {
	43	rcu_read_unlock();
	44	request_module("tcp_%s", name);
	45	rcu_read_lock();
	46	ca = tcp_ca_find(name);
	47	}
	48	#endif
	49	return ca;
	50	}
	51
	52	/* Simple linear search, not much in here. */
	53	struct tcp_congestion_ops *tcp_ca_find_key(u32 key)
	54	{
	55	struct tcp_congestion_ops *e;
	56
	57	list_for_each_entry_rcu(e, &tcp_cong_list, list) {
	58	if (e->key == key)
	59	return e;
	60	}
	61
	62	return NULL;
	63	}
	64
317a76f9	65	/*
d08df601	66	* Attach new congestion control algorithm to the list
317a76f9 SH	67	* of available options.
	68	*/
	69	int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
	70	{
	71	int ret = 0;
	72
e9799183 FW	73	/* all algorithms must implement these */
	74	if (!ca->ssthresh \|\| !ca->undo_cwnd \|\|
	75	!(ca->cong_avoid \|\| ca->cong_control)) {
afd46503	76	pr_err("%s does not implement required ops\n", ca->name);
317a76f9 SH	77	return -EINVAL;
	78	}
	79
c5c6a8ab DB	80	ca->key = jhash(ca->name, sizeof(ca->name), strlen(ca->name));
c5c6a8ab DB	81
317a76f9	82	spin_lock(&tcp_cong_list_lock);
c5c6a8ab DB	83	if (ca->key == TCP_CA_UNSPEC \|\| tcp_ca_find_key(ca->key)) {
	84	pr_notice("%s already registered or non-unique key\n",
	85	ca->name);
317a76f9 SH	86	ret = -EEXIST;
317a76f9 SH	87	} else {
3d2573f7	88	list_add_tail_rcu(&ca->list, &tcp_cong_list);
db2855ae	89	pr_debug("%s registered\n", ca->name);
317a76f9 SH	90	}
	91	spin_unlock(&tcp_cong_list_lock);
	92
	93	return ret;
	94	}
	95	EXPORT_SYMBOL_GPL(tcp_register_congestion_control);
	96
	97	/*
	98	* Remove congestion control algorithm, called from
	99	* the module's remove function. Module ref counts are used
	100	* to ensure that this can't be done till all sockets using
	101	* that method are closed.
	102	*/
	103	void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
	104	{
	105	spin_lock(&tcp_cong_list_lock);
	106	list_del_rcu(&ca->list);
	107	spin_unlock(&tcp_cong_list_lock);
c5c6a8ab DB	108
	109	/* Wait for outstanding readers to complete before the
	110	* module gets removed entirely.
	111	*
	112	* A try_module_get() should fail by now as our module is
	113	* in "going" state since no refs are held anymore and
	114	* module_exit() handler being called.
	115	*/
	116	synchronize_rcu();
317a76f9 SH	117	}
	118	EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
	119
6670e152	120	u32 tcp_ca_get_key_by_name(struct net net, const char name, bool *ecn_ca)
c5c6a8ab DB	121	{
c5c6a8ab DB	122	const struct tcp_congestion_ops *ca;
c3a8d947	123	u32 key = TCP_CA_UNSPEC;
c5c6a8ab DB	124
	125	might_sleep();
	126
	127	rcu_read_lock();
6670e152	128	ca = tcp_ca_find_autoload(net, name);
c3a8d947 DB	129	if (ca) {
	130	key = ca->key;
	131	*ecn_ca = ca->flags & TCP_CONG_NEEDS_ECN;
	132	}
c5c6a8ab DB	133	rcu_read_unlock();
	134
	135	return key;
	136	}
	137	EXPORT_SYMBOL_GPL(tcp_ca_get_key_by_name);
	138
	139	char tcp_ca_get_name_by_key(u32 key, char buffer)
	140	{
	141	const struct tcp_congestion_ops *ca;
	142	char *ret = NULL;
	143
	144	rcu_read_lock();
	145	ca = tcp_ca_find_key(key);
	146	if (ca)
	147	ret = strncpy(buffer, ca->name,
	148	TCP_CA_NAME_MAX);
	149	rcu_read_unlock();
	150
	151	return ret;
	152	}
	153	EXPORT_SYMBOL_GPL(tcp_ca_get_name_by_key);
	154
317a76f9	155	/* Assign choice of congestion control. */
55d8694f	156	void tcp_assign_congestion_control(struct sock *sk)
317a76f9	157	{
6670e152	158	struct net *net = sock_net(sk);
6687e988	159	struct inet_connection_sock *icsk = inet_csk(sk);
6670e152	160	const struct tcp_congestion_ops *ca;
317a76f9	161
55d8694f	162	rcu_read_lock();
6670e152 SH	163	ca = rcu_dereference(net->ipv4.tcp_congestion_control);
	164	if (unlikely(!try_module_get(ca->owner)))
	165	ca = &tcp_reno;
	166	icsk->icsk_ca_ops = ca;
55d8694f FW	167	rcu_read_unlock();
55d8694f FW	168
6670e152	169	memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
6ac705b1 ED	170	if (ca->flags & TCP_CONG_NEEDS_ECN)
	171	INET_ECN_xmit(sk);
	172	else
	173	INET_ECN_dontxmit(sk);
55d8694f FW	174	}
	175
	176	void tcp_init_congestion_control(struct sock *sk)
	177	{
	178	const struct inet_connection_sock *icsk = inet_csk(sk);
317a76f9	179
44abafc4	180	tcp_sk(sk)->prior_ssthresh = 0;
6687e988 ACM	181	if (icsk->icsk_ca_ops->init)
6687e988 ACM	182	icsk->icsk_ca_ops->init(sk);
6ac705b1 ED	183	if (tcp_ca_needs_ecn(sk))
	184	INET_ECN_xmit(sk);
	185	else
	186	INET_ECN_dontxmit(sk);
317a76f9 SH	187	}
317a76f9 SH	188
ebfa00c5 SD	189	static void tcp_reinit_congestion_control(struct sock *sk,
ebfa00c5 SD	190	const struct tcp_congestion_ops *ca)
29ba4fff DB	191	{
	192	struct inet_connection_sock *icsk = inet_csk(sk);
	193
	194	tcp_cleanup_congestion_control(sk);
	195	icsk->icsk_ca_ops = ca;
9f950415	196	icsk->icsk_ca_setsockopt = 1;
c1201444	197	memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
29ba4fff	198
c1201444	199	if (sk->sk_state != TCP_CLOSE)
6ac705b1	200	tcp_init_congestion_control(sk);
29ba4fff DB	201	}
29ba4fff DB	202
317a76f9	203	/* Manage refcounts on socket close. */
6687e988	204	void tcp_cleanup_congestion_control(struct sock *sk)
317a76f9	205	{
6687e988 ACM	206	struct inet_connection_sock *icsk = inet_csk(sk);
	207
	208	if (icsk->icsk_ca_ops->release)
	209	icsk->icsk_ca_ops->release(sk);
	210	module_put(icsk->icsk_ca_ops->owner);
317a76f9 SH	211	}
	212
	213	/* Used by sysctl to change default congestion control */
6670e152	214	int tcp_set_default_congestion_control(struct net net, const char name)
317a76f9 SH	215	{
317a76f9 SH	216	struct tcp_congestion_ops *ca;
6670e152 SH	217	const struct tcp_congestion_ops *prev;
6670e152 SH	218	int ret;
317a76f9	219
6670e152 SH	220	rcu_read_lock();
	221	ca = tcp_ca_find_autoload(net, name);
	222	if (!ca) {
	223	ret = -ENOENT;
	224	} else if (!try_module_get(ca->owner)) {
	225	ret = -EBUSY;
	226	} else {
	227	prev = xchg(&net->ipv4.tcp_congestion_control, ca);
	228	if (prev)
	229	module_put(prev->owner);
317a76f9	230
6670e152	231	ca->flags \|= TCP_CONG_NON_RESTRICTED;
317a76f9 SH	232	ret = 0;
317a76f9 SH	233	}
6670e152	234	rcu_read_unlock();
317a76f9 SH	235
	236	return ret;
	237	}
	238
b1736a71 SH	239	/* Set default value from kernel configuration at bootup */
	240	static int __init tcp_congestion_default(void)
	241	{
6670e152 SH	242	return tcp_set_default_congestion_control(&init_net,
6670e152 SH	243	CONFIG_DEFAULT_TCP_CONG);
b1736a71 SH	244	}
	245	late_initcall(tcp_congestion_default);
	246
3ff825b2 SH	247	/* Build string with list of available congestion control values */
	248	void tcp_get_available_congestion_control(char *buf, size_t maxlen)
	249	{
	250	struct tcp_congestion_ops *ca;
	251	size_t offs = 0;
	252
	253	rcu_read_lock();
	254	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
	255	offs += snprintf(buf + offs, maxlen - offs,
	256	"%s%s",
	257	offs == 0 ? "" : " ", ca->name);
3ff825b2 SH	258	}
	259	rcu_read_unlock();
	260	}
	261
317a76f9	262	/* Get current default congestion control */
6670e152	263	void tcp_get_default_congestion_control(struct net net, char name)
317a76f9	264	{
6670e152	265	const struct tcp_congestion_ops *ca;
317a76f9 SH	266
317a76f9 SH	267	rcu_read_lock();
6670e152	268	ca = rcu_dereference(net->ipv4.tcp_congestion_control);
317a76f9 SH	269	strncpy(name, ca->name, TCP_CA_NAME_MAX);
	270	rcu_read_unlock();
	271	}
	272
ce7bc3bf SH	273	/* Built list of non-restricted congestion control values */
	274	void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)
	275	{
	276	struct tcp_congestion_ops *ca;
	277	size_t offs = 0;
	278
	279	*buf = '\0';
	280	rcu_read_lock();
	281	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
164891aa	282	if (!(ca->flags & TCP_CONG_NON_RESTRICTED))
ce7bc3bf SH	283	continue;
	284	offs += snprintf(buf + offs, maxlen - offs,
	285	"%s%s",
	286	offs == 0 ? "" : " ", ca->name);
ce7bc3bf SH	287	}
	288	rcu_read_unlock();
	289	}
	290
	291	/* Change list of non-restricted congestion control */
	292	int tcp_set_allowed_congestion_control(char *val)
	293	{
	294	struct tcp_congestion_ops *ca;
c34186ed	295	char saved_clone, clone, *name;
ce7bc3bf SH	296	int ret = 0;
ce7bc3bf SH	297
c34186ed	298	saved_clone = clone = kstrdup(val, GFP_USER);
ce7bc3bf SH	299	if (!clone)
	300	return -ENOMEM;
	301
	302	spin_lock(&tcp_cong_list_lock);
	303	/* pass 1 check for bad entries */
	304	while ((name = strsep(&clone, " ")) && *name) {
	305	ca = tcp_ca_find(name);
	306	if (!ca) {
	307	ret = -ENOENT;
	308	goto out;
	309	}
	310	}
	311
164891aa	312	/* pass 2 clear old values */
ce7bc3bf	313	list_for_each_entry_rcu(ca, &tcp_cong_list, list)
164891aa	314	ca->flags &= ~TCP_CONG_NON_RESTRICTED;
ce7bc3bf SH	315
	316	/* pass 3 mark as allowed */
	317	while ((name = strsep(&val, " ")) && *name) {
	318	ca = tcp_ca_find(name);
	319	WARN_ON(!ca);
	320	if (ca)
164891aa	321	ca->flags \|= TCP_CONG_NON_RESTRICTED;
ce7bc3bf SH	322	}
	323	out:
	324	spin_unlock(&tcp_cong_list_lock);
c34186ed	325	kfree(saved_clone);
ce7bc3bf SH	326
	327	return ret;
	328	}
	329
91b5b21c LB	330	/* Change congestion control for socket. If load is false, then it is the
	331	* responsibility of the caller to call tcp_init_congestion_control or
	332	* tcp_reinit_congestion_control (if the current congestion control was
	333	* already initialized.
	334	*/
ebfa00c5	335	int tcp_set_congestion_control(struct sock sk, const char name, bool load, bool reinit)
5f8ef48d	336	{
6687e988	337	struct inet_connection_sock *icsk = inet_csk(sk);
c5c6a8ab	338	const struct tcp_congestion_ops *ca;
5f8ef48d SH	339	int err = 0;
5f8ef48d SH	340
c5c6a8ab DB	341	if (icsk->icsk_ca_dst_locked)
c5c6a8ab DB	342	return -EPERM;
4d4d3d1e	343
c5c6a8ab	344	rcu_read_lock();
91b5b21c LB	345	if (!load)
	346	ca = tcp_ca_find(name);
	347	else
6670e152 SH	348	ca = tcp_ca_find_autoload(sock_net(sk), name);
6670e152 SH	349
c5c6a8ab	350	/* No change asking for existing value */
9f950415 NC	351	if (ca == icsk->icsk_ca_ops) {
9f950415 NC	352	icsk->icsk_ca_setsockopt = 1;
5f8ef48d	353	goto out;
9f950415	354	}
6670e152	355
91b5b21c	356	if (!ca) {
5f8ef48d	357	err = -ENOENT;
91b5b21c	358	} else if (!load) {
ebfa00c5 SD	359	const struct tcp_congestion_ops *old_ca = icsk->icsk_ca_ops;
	360
	361	if (try_module_get(ca->owner)) {
	362	if (reinit) {
	363	tcp_reinit_congestion_control(sk, ca);
	364	} else {
	365	icsk->icsk_ca_ops = ca;
	366	module_put(old_ca->owner);
	367	}
	368	} else {
91b5b21c	369	err = -EBUSY;
ebfa00c5	370	}
91b5b21c LB	371	} else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) \|\|
91b5b21c LB	372	ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))) {
ce7bc3bf	373	err = -EPERM;
91b5b21c	374	} else if (!try_module_get(ca->owner)) {
5f8ef48d	375	err = -EBUSY;
91b5b21c	376	} else {
29ba4fff	377	tcp_reinit_congestion_control(sk, ca);
91b5b21c	378	}
5f8ef48d SH	379	out:
	380	rcu_read_unlock();
	381	return err;
	382	}
	383
9f9843a7 YC	384	/* Slow start is used when congestion window is no greater than the slow start
	385	* threshold. We base on RFC2581 and also handle stretch ACKs properly.
	386	* We do not implement RFC3465 Appropriate Byte Counting (ABC) per se but
	387	* something better;) a packet is only considered (s)acked in its entirety to
	388	* defend the ACK attacks described in the RFC. Slow start processes a stretch
	389	* ACK of degree N as if N acks of degree 1 are received back to back except
	390	* ABC caps N to 2. Slow start exits when cwnd grows over ssthresh and
	391	* returns the leftover acks to adjust cwnd in congestion avoidance mode.
40efc6fa	392	*/
e73ebb08	393	u32 tcp_slow_start(struct tcp_sock *tp, u32 acked)
40efc6fa	394	{
76174004	395	u32 cwnd = min(tp->snd_cwnd + acked, tp->snd_ssthresh);
a02ba041	396
e73ebb08	397	acked -= cwnd - tp->snd_cwnd;
9f9843a7	398	tp->snd_cwnd = min(cwnd, tp->snd_cwnd_clamp);
e73ebb08 NC	399
e73ebb08 NC	400	return acked;
40efc6fa SH	401	}
	402	EXPORT_SYMBOL_GPL(tcp_slow_start);
	403
814d488c NC	404	/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w),
	405	* for every packet that was ACKed.
	406	*/
e73ebb08	407	void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked)
758ce5c8	408	{
9949afa4 NC	409	/* If credits accumulated at a higher w, apply them gently now. */
	410	if (tp->snd_cwnd_cnt >= w) {
	411	tp->snd_cwnd_cnt = 0;
	412	tp->snd_cwnd++;
	413	}
	414
814d488c	415	tp->snd_cwnd_cnt += acked;
758ce5c8	416	if (tp->snd_cwnd_cnt >= w) {
814d488c NC	417	u32 delta = tp->snd_cwnd_cnt / w;
	418
	419	tp->snd_cwnd_cnt -= delta * w;
	420	tp->snd_cwnd += delta;
758ce5c8	421	}
814d488c	422	tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_cwnd_clamp);
758ce5c8 IJ	423	}
	424	EXPORT_SYMBOL_GPL(tcp_cong_avoid_ai);
	425
317a76f9 SH	426	/*
	427	* TCP Reno congestion control
	428	* This is special case used for fallback as well.
	429	*/
	430	/* This is Jacobson's slow start and congestion avoidance.
	431	* SIGCOMM '88, p. 328.
	432	*/
24901551	433	void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
317a76f9	434	{
6687e988 ACM	435	struct tcp_sock *tp = tcp_sk(sk);
6687e988 ACM	436
24901551	437	if (!tcp_is_cwnd_limited(sk))
317a76f9 SH	438	return;
317a76f9 SH	439
7faffa1c	440	/* In "safe" area, increase. */
071d5080	441	if (tcp_in_slow_start(tp)) {
c22bdca9 NC	442	acked = tcp_slow_start(tp, acked);
	443	if (!acked)
	444	return;
	445	}
e905a9ed	446	/* In dangerous area, increase slowly. */
c22bdca9	447	tcp_cong_avoid_ai(tp, tp->snd_cwnd, acked);
317a76f9 SH	448	}
	449	EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
	450
	451	/* Slow start threshold is half the congestion window (min 2) */
6687e988	452	u32 tcp_reno_ssthresh(struct sock *sk)
317a76f9	453	{
6687e988	454	const struct tcp_sock *tp = tcp_sk(sk);
688d1945	455
317a76f9 SH	456	return max(tp->snd_cwnd >> 1U, 2U);
	457	}
	458	EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
	459
e9799183 FW	460	u32 tcp_reno_undo_cwnd(struct sock *sk)
	461	{
	462	const struct tcp_sock *tp = tcp_sk(sk);
	463
4faf7839	464	return max(tp->snd_cwnd, tp->prior_cwnd);
e9799183 FW	465	}
	466	EXPORT_SYMBOL_GPL(tcp_reno_undo_cwnd);
	467
317a76f9	468	struct tcp_congestion_ops tcp_reno = {
164891aa	469	.flags = TCP_CONG_NON_RESTRICTED,
317a76f9 SH	470	.name = "reno",
	471	.owner = THIS_MODULE,
	472	.ssthresh = tcp_reno_ssthresh,
	473	.cong_avoid = tcp_reno_cong_avoid,
e9799183	474	.undo_cwnd = tcp_reno_undo_cwnd,
317a76f9	475	};