[thirdparty/kernel/stable.git] / net / ipv4 / tcp_cong.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * 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
457c8996	1	// SPDX-License-Identifier: GPL-2.0-only
317a76f9	2	/*
b92022f3	3	* Pluggable TCP congestion control support and newReno
317a76f9	4	* congestion control.
02582e9b	5	* Based on ideas from I/O scheduler support and Web100.
317a76f9 SH	6	*
	7	* Copyright (C) 2005 Stephen Hemminger <shemminger@osdl.org>
	8	*/
	9
afd46503 JP	10	#define pr_fmt(fmt) "TCP: " fmt
afd46503 JP	11
317a76f9 SH	12	#include <linux/module.h>
	13	#include <linux/mm.h>
	14	#include <linux/types.h>
	15	#include <linux/list.h>
5a0e3ad6	16	#include <linux/gfp.h>
c5c6a8ab	17	#include <linux/jhash.h>
317a76f9 SH	18	#include <net/tcp.h>
	19
	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
c5c6a8ab	36	/* Must be called with rcu lock held */
6670e152 SH	37	static struct tcp_congestion_ops tcp_ca_find_autoload(struct net net,
6670e152 SH	38	const char *name)
c5c6a8ab	39	{
6670e152 SH	40	struct tcp_congestion_ops *ca = tcp_ca_find(name);
6670e152 SH	41
c5c6a8ab DB	42	#ifdef CONFIG_MODULES
	43	if (!ca && capable(CAP_NET_ADMIN)) {
	44	rcu_read_unlock();
	45	request_module("tcp_%s", name);
	46	rcu_read_lock();
	47	ca = tcp_ca_find(name);
	48	}
	49	#endif
	50	return ca;
	51	}
	52
	53	/* Simple linear search, not much in here. */
	54	struct tcp_congestion_ops *tcp_ca_find_key(u32 key)
	55	{
	56	struct tcp_congestion_ops *e;
	57
	58	list_for_each_entry_rcu(e, &tcp_cong_list, list) {
	59	if (e->key == key)
	60	return e;
	61	}
	62
	63	return NULL;
	64	}
	65
317a76f9	66	/*
d08df601	67	* Attach new congestion control algorithm to the list
317a76f9 SH	68	* of available options.
	69	*/
	70	int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
	71	{
	72	int ret = 0;
	73
e9799183 FW	74	/* all algorithms must implement these */
	75	if (!ca->ssthresh \|\| !ca->undo_cwnd \|\|
	76	!(ca->cong_avoid \|\| ca->cong_control)) {
afd46503	77	pr_err("%s does not implement required ops\n", ca->name);
317a76f9 SH	78	return -EINVAL;
	79	}
	80
c5c6a8ab DB	81	ca->key = jhash(ca->name, sizeof(ca->name), strlen(ca->name));
c5c6a8ab DB	82
317a76f9	83	spin_lock(&tcp_cong_list_lock);
c5c6a8ab DB	84	if (ca->key == TCP_CA_UNSPEC \|\| tcp_ca_find_key(ca->key)) {
	85	pr_notice("%s already registered or non-unique key\n",
	86	ca->name);
317a76f9 SH	87	ret = -EEXIST;
317a76f9 SH	88	} else {
3d2573f7	89	list_add_tail_rcu(&ca->list, &tcp_cong_list);
db2855ae	90	pr_debug("%s registered\n", ca->name);
317a76f9 SH	91	}
	92	spin_unlock(&tcp_cong_list_lock);
	93
	94	return ret;
	95	}
	96	EXPORT_SYMBOL_GPL(tcp_register_congestion_control);
	97
	98	/*
	99	* Remove congestion control algorithm, called from
	100	* the module's remove function. Module ref counts are used
	101	* to ensure that this can't be done till all sockets using
	102	* that method are closed.
	103	*/
	104	void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
	105	{
	106	spin_lock(&tcp_cong_list_lock);
	107	list_del_rcu(&ca->list);
	108	spin_unlock(&tcp_cong_list_lock);
c5c6a8ab DB	109
	110	/* Wait for outstanding readers to complete before the
	111	* module gets removed entirely.
	112	*
	113	* A try_module_get() should fail by now as our module is
	114	* in "going" state since no refs are held anymore and
	115	* module_exit() handler being called.
	116	*/
	117	synchronize_rcu();
317a76f9 SH	118	}
	119	EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
	120
6670e152	121	u32 tcp_ca_get_key_by_name(struct net net, const char name, bool *ecn_ca)
c5c6a8ab DB	122	{
c5c6a8ab DB	123	const struct tcp_congestion_ops *ca;
c3a8d947	124	u32 key = TCP_CA_UNSPEC;
c5c6a8ab DB	125
	126	might_sleep();
	127
	128	rcu_read_lock();
6670e152	129	ca = tcp_ca_find_autoload(net, name);
c3a8d947 DB	130	if (ca) {
	131	key = ca->key;
	132	*ecn_ca = ca->flags & TCP_CONG_NEEDS_ECN;
	133	}
c5c6a8ab DB	134	rcu_read_unlock();
	135
	136	return key;
	137	}
	138	EXPORT_SYMBOL_GPL(tcp_ca_get_key_by_name);
	139
	140	char tcp_ca_get_name_by_key(u32 key, char buffer)
	141	{
	142	const struct tcp_congestion_ops *ca;
	143	char *ret = NULL;
	144
	145	rcu_read_lock();
	146	ca = tcp_ca_find_key(key);
	147	if (ca)
	148	ret = strncpy(buffer, ca->name,
	149	TCP_CA_NAME_MAX);
	150	rcu_read_unlock();
	151
	152	return ret;
	153	}
	154	EXPORT_SYMBOL_GPL(tcp_ca_get_name_by_key);
	155
317a76f9	156	/* Assign choice of congestion control. */
55d8694f	157	void tcp_assign_congestion_control(struct sock *sk)
317a76f9	158	{
6670e152	159	struct net *net = sock_net(sk);
6687e988	160	struct inet_connection_sock *icsk = inet_csk(sk);
6670e152	161	const struct tcp_congestion_ops *ca;
317a76f9	162
55d8694f	163	rcu_read_lock();
6670e152 SH	164	ca = rcu_dereference(net->ipv4.tcp_congestion_control);
	165	if (unlikely(!try_module_get(ca->owner)))
	166	ca = &tcp_reno;
	167	icsk->icsk_ca_ops = ca;
55d8694f FW	168	rcu_read_unlock();
55d8694f FW	169
6670e152	170	memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
6ac705b1 ED	171	if (ca->flags & TCP_CONG_NEEDS_ECN)
	172	INET_ECN_xmit(sk);
	173	else
	174	INET_ECN_dontxmit(sk);
55d8694f FW	175	}
	176
	177	void tcp_init_congestion_control(struct sock *sk)
	178	{
	179	const struct inet_connection_sock *icsk = inet_csk(sk);
317a76f9	180
44abafc4	181	tcp_sk(sk)->prior_ssthresh = 0;
6687e988 ACM	182	if (icsk->icsk_ca_ops->init)
6687e988 ACM	183	icsk->icsk_ca_ops->init(sk);
6ac705b1 ED	184	if (tcp_ca_needs_ecn(sk))
	185	INET_ECN_xmit(sk);
	186	else
	187	INET_ECN_dontxmit(sk);
317a76f9 SH	188	}
317a76f9 SH	189
ebfa00c5 SD	190	static void tcp_reinit_congestion_control(struct sock *sk,
ebfa00c5 SD	191	const struct tcp_congestion_ops *ca)
29ba4fff DB	192	{
	193	struct inet_connection_sock *icsk = inet_csk(sk);
	194
	195	tcp_cleanup_congestion_control(sk);
	196	icsk->icsk_ca_ops = ca;
9f950415	197	icsk->icsk_ca_setsockopt = 1;
c1201444	198	memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
29ba4fff	199
c1201444	200	if (sk->sk_state != TCP_CLOSE)
6ac705b1	201	tcp_init_congestion_control(sk);
29ba4fff DB	202	}
29ba4fff DB	203
317a76f9	204	/* Manage refcounts on socket close. */
6687e988	205	void tcp_cleanup_congestion_control(struct sock *sk)
317a76f9	206	{
6687e988 ACM	207	struct inet_connection_sock *icsk = inet_csk(sk);
	208
	209	if (icsk->icsk_ca_ops->release)
	210	icsk->icsk_ca_ops->release(sk);
	211	module_put(icsk->icsk_ca_ops->owner);
317a76f9 SH	212	}
	213
	214	/* Used by sysctl to change default congestion control */
6670e152	215	int tcp_set_default_congestion_control(struct net net, const char name)
317a76f9 SH	216	{
317a76f9 SH	217	struct tcp_congestion_ops *ca;
6670e152 SH	218	const struct tcp_congestion_ops *prev;
6670e152 SH	219	int ret;
317a76f9	220
6670e152 SH	221	rcu_read_lock();
	222	ca = tcp_ca_find_autoload(net, name);
	223	if (!ca) {
	224	ret = -ENOENT;
	225	} else if (!try_module_get(ca->owner)) {
	226	ret = -EBUSY;
	227	} else {
	228	prev = xchg(&net->ipv4.tcp_congestion_control, ca);
	229	if (prev)
	230	module_put(prev->owner);
317a76f9	231
6670e152	232	ca->flags \|= TCP_CONG_NON_RESTRICTED;
317a76f9 SH	233	ret = 0;
317a76f9 SH	234	}
6670e152	235	rcu_read_unlock();
317a76f9 SH	236
	237	return ret;
	238	}
	239
b1736a71 SH	240	/* Set default value from kernel configuration at bootup */
	241	static int __init tcp_congestion_default(void)
	242	{
6670e152 SH	243	return tcp_set_default_congestion_control(&init_net,
6670e152 SH	244	CONFIG_DEFAULT_TCP_CONG);
b1736a71 SH	245	}
	246	late_initcall(tcp_congestion_default);
	247
3ff825b2 SH	248	/* Build string with list of available congestion control values */
	249	void tcp_get_available_congestion_control(char *buf, size_t maxlen)
	250	{
	251	struct tcp_congestion_ops *ca;
	252	size_t offs = 0;
	253
	254	rcu_read_lock();
	255	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
	256	offs += snprintf(buf + offs, maxlen - offs,
	257	"%s%s",
	258	offs == 0 ? "" : " ", ca->name);
3ff825b2 SH	259	}
	260	rcu_read_unlock();
	261	}
	262
317a76f9	263	/* Get current default congestion control */
6670e152	264	void tcp_get_default_congestion_control(struct net net, char name)
317a76f9	265	{
6670e152	266	const struct tcp_congestion_ops *ca;
317a76f9 SH	267
317a76f9 SH	268	rcu_read_lock();
6670e152	269	ca = rcu_dereference(net->ipv4.tcp_congestion_control);
317a76f9 SH	270	strncpy(name, ca->name, TCP_CA_NAME_MAX);
	271	rcu_read_unlock();
	272	}
	273
ce7bc3bf SH	274	/* Built list of non-restricted congestion control values */
	275	void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)
	276	{
	277	struct tcp_congestion_ops *ca;
	278	size_t offs = 0;
	279
	280	*buf = '\0';
	281	rcu_read_lock();
	282	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
164891aa	283	if (!(ca->flags & TCP_CONG_NON_RESTRICTED))
ce7bc3bf SH	284	continue;
	285	offs += snprintf(buf + offs, maxlen - offs,
	286	"%s%s",
	287	offs == 0 ? "" : " ", ca->name);
ce7bc3bf SH	288	}
	289	rcu_read_unlock();
	290	}
	291
	292	/* Change list of non-restricted congestion control */
	293	int tcp_set_allowed_congestion_control(char *val)
	294	{
	295	struct tcp_congestion_ops *ca;
c34186ed	296	char saved_clone, clone, *name;
ce7bc3bf SH	297	int ret = 0;
ce7bc3bf SH	298
c34186ed	299	saved_clone = clone = kstrdup(val, GFP_USER);
ce7bc3bf SH	300	if (!clone)
	301	return -ENOMEM;
	302
	303	spin_lock(&tcp_cong_list_lock);
	304	/* pass 1 check for bad entries */
	305	while ((name = strsep(&clone, " ")) && *name) {
	306	ca = tcp_ca_find(name);
	307	if (!ca) {
	308	ret = -ENOENT;
	309	goto out;
	310	}
	311	}
	312
164891aa	313	/* pass 2 clear old values */
ce7bc3bf	314	list_for_each_entry_rcu(ca, &tcp_cong_list, list)
164891aa	315	ca->flags &= ~TCP_CONG_NON_RESTRICTED;
ce7bc3bf SH	316
	317	/* pass 3 mark as allowed */
	318	while ((name = strsep(&val, " ")) && *name) {
	319	ca = tcp_ca_find(name);
	320	WARN_ON(!ca);
	321	if (ca)
164891aa	322	ca->flags \|= TCP_CONG_NON_RESTRICTED;
ce7bc3bf SH	323	}
	324	out:
	325	spin_unlock(&tcp_cong_list_lock);
c34186ed	326	kfree(saved_clone);
ce7bc3bf SH	327
	328	return ret;
	329	}
	330
91b5b21c LB	331	/* Change congestion control for socket. If load is false, then it is the
	332	* responsibility of the caller to call tcp_init_congestion_control or
	333	* tcp_reinit_congestion_control (if the current congestion control was
	334	* already initialized.
	335	*/
ebfa00c5	336	int tcp_set_congestion_control(struct sock sk, const char name, bool load, bool reinit)
5f8ef48d	337	{
6687e988	338	struct inet_connection_sock *icsk = inet_csk(sk);
c5c6a8ab	339	const struct tcp_congestion_ops *ca;
5f8ef48d SH	340	int err = 0;
5f8ef48d SH	341
c5c6a8ab DB	342	if (icsk->icsk_ca_dst_locked)
c5c6a8ab DB	343	return -EPERM;
4d4d3d1e	344
c5c6a8ab	345	rcu_read_lock();
91b5b21c LB	346	if (!load)
	347	ca = tcp_ca_find(name);
	348	else
6670e152 SH	349	ca = tcp_ca_find_autoload(sock_net(sk), name);
6670e152 SH	350
c5c6a8ab	351	/* No change asking for existing value */
9f950415 NC	352	if (ca == icsk->icsk_ca_ops) {
9f950415 NC	353	icsk->icsk_ca_setsockopt = 1;
5f8ef48d	354	goto out;
9f950415	355	}
6670e152	356
91b5b21c	357	if (!ca) {
5f8ef48d	358	err = -ENOENT;
91b5b21c	359	} else if (!load) {
ebfa00c5 SD	360	const struct tcp_congestion_ops *old_ca = icsk->icsk_ca_ops;
	361
	362	if (try_module_get(ca->owner)) {
	363	if (reinit) {
	364	tcp_reinit_congestion_control(sk, ca);
	365	} else {
	366	icsk->icsk_ca_ops = ca;
	367	module_put(old_ca->owner);
	368	}
	369	} else {
91b5b21c	370	err = -EBUSY;
ebfa00c5	371	}
91b5b21c LB	372	} else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) \|\|
91b5b21c LB	373	ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))) {
ce7bc3bf	374	err = -EPERM;
91b5b21c	375	} else if (!try_module_get(ca->owner)) {
5f8ef48d	376	err = -EBUSY;
91b5b21c	377	} else {
29ba4fff	378	tcp_reinit_congestion_control(sk, ca);
91b5b21c	379	}
5f8ef48d SH	380	out:
	381	rcu_read_unlock();
	382	return err;
	383	}
	384
9f9843a7 YC	385	/* Slow start is used when congestion window is no greater than the slow start
	386	* threshold. We base on RFC2581 and also handle stretch ACKs properly.
	387	* We do not implement RFC3465 Appropriate Byte Counting (ABC) per se but
	388	* something better;) a packet is only considered (s)acked in its entirety to
	389	* defend the ACK attacks described in the RFC. Slow start processes a stretch
	390	* ACK of degree N as if N acks of degree 1 are received back to back except
	391	* ABC caps N to 2. Slow start exits when cwnd grows over ssthresh and
	392	* returns the leftover acks to adjust cwnd in congestion avoidance mode.
40efc6fa	393	*/
e73ebb08	394	u32 tcp_slow_start(struct tcp_sock *tp, u32 acked)
40efc6fa	395	{
76174004	396	u32 cwnd = min(tp->snd_cwnd + acked, tp->snd_ssthresh);
a02ba041	397
e73ebb08	398	acked -= cwnd - tp->snd_cwnd;
9f9843a7	399	tp->snd_cwnd = min(cwnd, tp->snd_cwnd_clamp);
e73ebb08 NC	400
e73ebb08 NC	401	return acked;
40efc6fa SH	402	}
	403	EXPORT_SYMBOL_GPL(tcp_slow_start);
	404
814d488c NC	405	/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w),
	406	* for every packet that was ACKed.
	407	*/
e73ebb08	408	void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked)
758ce5c8	409	{
9949afa4 NC	410	/* If credits accumulated at a higher w, apply them gently now. */
	411	if (tp->snd_cwnd_cnt >= w) {
	412	tp->snd_cwnd_cnt = 0;
	413	tp->snd_cwnd++;
	414	}
	415
814d488c	416	tp->snd_cwnd_cnt += acked;
758ce5c8	417	if (tp->snd_cwnd_cnt >= w) {
814d488c NC	418	u32 delta = tp->snd_cwnd_cnt / w;
	419
	420	tp->snd_cwnd_cnt -= delta * w;
	421	tp->snd_cwnd += delta;
758ce5c8	422	}
814d488c	423	tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_cwnd_clamp);
758ce5c8 IJ	424	}
	425	EXPORT_SYMBOL_GPL(tcp_cong_avoid_ai);
	426
317a76f9 SH	427	/*
	428	* TCP Reno congestion control
	429	* This is special case used for fallback as well.
	430	*/
	431	/* This is Jacobson's slow start and congestion avoidance.
	432	* SIGCOMM '88, p. 328.
	433	*/
24901551	434	void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked)
317a76f9	435	{
6687e988 ACM	436	struct tcp_sock *tp = tcp_sk(sk);
6687e988 ACM	437
24901551	438	if (!tcp_is_cwnd_limited(sk))
317a76f9 SH	439	return;
317a76f9 SH	440
7faffa1c	441	/* In "safe" area, increase. */
071d5080	442	if (tcp_in_slow_start(tp)) {
c22bdca9 NC	443	acked = tcp_slow_start(tp, acked);
	444	if (!acked)
	445	return;
	446	}
e905a9ed	447	/* In dangerous area, increase slowly. */
c22bdca9	448	tcp_cong_avoid_ai(tp, tp->snd_cwnd, acked);
317a76f9 SH	449	}
	450	EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
	451
	452	/* Slow start threshold is half the congestion window (min 2) */
6687e988	453	u32 tcp_reno_ssthresh(struct sock *sk)
317a76f9	454	{
6687e988	455	const struct tcp_sock *tp = tcp_sk(sk);
688d1945	456
317a76f9 SH	457	return max(tp->snd_cwnd >> 1U, 2U);
	458	}
	459	EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
	460
e9799183 FW	461	u32 tcp_reno_undo_cwnd(struct sock *sk)
	462	{
	463	const struct tcp_sock *tp = tcp_sk(sk);
	464
4faf7839	465	return max(tp->snd_cwnd, tp->prior_cwnd);
e9799183 FW	466	}
	467	EXPORT_SYMBOL_GPL(tcp_reno_undo_cwnd);
	468
317a76f9	469	struct tcp_congestion_ops tcp_reno = {
164891aa	470	.flags = TCP_CONG_NON_RESTRICTED,
317a76f9 SH	471	.name = "reno",
	472	.owner = THIS_MODULE,
	473	.ssthresh = tcp_reno_ssthresh,
	474	.cong_avoid = tcp_reno_cong_avoid,
e9799183	475	.undo_cwnd = tcp_reno_undo_cwnd,
317a76f9	476	};