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/*
* 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 const struct tcp_congestion_ops *__tcp_ca_find_autoload(const char *name)
{
const 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 ssthresh and cong_avoid ops */
if (!ca->ssthresh || !(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(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(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 inet_connection_sock *icsk = inet_csk(sk);
struct tcp_congestion_ops *ca;
rcu_read_lock();
list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
if (likely(try_module_get(ca->owner))) {
icsk->icsk_ca_ops = ca;
goto out;
}
/* Fallback to next available. The last really
* guaranteed fallback is Reno from this list.
*/
}
out:
rcu_read_unlock();
/* Clear out private data before diag gets it and
* the ca has not been initialized.
*/
if (ca->get_info)
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);
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;
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(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 ? "" :
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