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![John Heffner](/assets/img/avatar_default.png)
This fixes inappropriately large cwnd growth on sender-limited flows when GSO is enabled, limiting cwnd growth to 64k. Signed-off-by: John Heffner <johnwheffner@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
415 lines
10 KiB
C
415 lines
10 KiB
C
/*
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* Plugable TCP congestion control support and newReno
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* congestion control.
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* Based on ideas from I/O scheduler suport and Web100.
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*
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* Copyright (C) 2005 Stephen Hemminger <shemminger@osdl.org>
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*/
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#include <linux/module.h>
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#include <linux/mm.h>
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#include <linux/types.h>
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#include <linux/list.h>
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#include <net/tcp.h>
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int sysctl_tcp_max_ssthresh = 0;
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static DEFINE_SPINLOCK(tcp_cong_list_lock);
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static LIST_HEAD(tcp_cong_list);
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/* Simple linear search, don't expect many entries! */
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static struct tcp_congestion_ops *tcp_ca_find(const char *name)
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{
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struct tcp_congestion_ops *e;
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list_for_each_entry_rcu(e, &tcp_cong_list, list) {
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if (strcmp(e->name, name) == 0)
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return e;
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}
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return NULL;
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}
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/*
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* Attach new congestion control algorithm to the list
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* of available options.
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*/
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int tcp_register_congestion_control(struct tcp_congestion_ops *ca)
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{
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int ret = 0;
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/* all algorithms must implement ssthresh and cong_avoid ops */
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if (!ca->ssthresh || !ca->cong_avoid) {
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printk(KERN_ERR "TCP %s does not implement required ops\n",
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ca->name);
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return -EINVAL;
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}
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spin_lock(&tcp_cong_list_lock);
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if (tcp_ca_find(ca->name)) {
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printk(KERN_NOTICE "TCP %s already registered\n", ca->name);
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ret = -EEXIST;
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} else {
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list_add_tail_rcu(&ca->list, &tcp_cong_list);
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printk(KERN_INFO "TCP %s registered\n", ca->name);
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}
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spin_unlock(&tcp_cong_list_lock);
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return ret;
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}
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EXPORT_SYMBOL_GPL(tcp_register_congestion_control);
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/*
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* Remove congestion control algorithm, called from
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* the module's remove function. Module ref counts are used
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* to ensure that this can't be done till all sockets using
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* that method are closed.
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*/
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void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
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{
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spin_lock(&tcp_cong_list_lock);
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list_del_rcu(&ca->list);
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spin_unlock(&tcp_cong_list_lock);
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}
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EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
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/* Assign choice of congestion control. */
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void tcp_init_congestion_control(struct sock *sk)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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struct tcp_congestion_ops *ca;
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/* if no choice made yet assign the current value set as default */
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if (icsk->icsk_ca_ops == &tcp_init_congestion_ops) {
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rcu_read_lock();
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list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
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if (try_module_get(ca->owner)) {
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icsk->icsk_ca_ops = ca;
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break;
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}
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/* fallback to next available */
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}
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rcu_read_unlock();
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}
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if (icsk->icsk_ca_ops->init)
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icsk->icsk_ca_ops->init(sk);
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}
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/* Manage refcounts on socket close. */
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void tcp_cleanup_congestion_control(struct sock *sk)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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if (icsk->icsk_ca_ops->release)
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icsk->icsk_ca_ops->release(sk);
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module_put(icsk->icsk_ca_ops->owner);
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}
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/* Used by sysctl to change default congestion control */
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int tcp_set_default_congestion_control(const char *name)
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{
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struct tcp_congestion_ops *ca;
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int ret = -ENOENT;
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spin_lock(&tcp_cong_list_lock);
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ca = tcp_ca_find(name);
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#ifdef CONFIG_KMOD
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if (!ca && capable(CAP_SYS_MODULE)) {
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spin_unlock(&tcp_cong_list_lock);
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request_module("tcp_%s", name);
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spin_lock(&tcp_cong_list_lock);
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ca = tcp_ca_find(name);
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}
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#endif
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if (ca) {
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ca->flags |= TCP_CONG_NON_RESTRICTED; /* default is always allowed */
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list_move(&ca->list, &tcp_cong_list);
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ret = 0;
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}
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spin_unlock(&tcp_cong_list_lock);
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return ret;
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}
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/* Set default value from kernel configuration at bootup */
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static int __init tcp_congestion_default(void)
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{
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return tcp_set_default_congestion_control(CONFIG_DEFAULT_TCP_CONG);
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}
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late_initcall(tcp_congestion_default);
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/* Build string with list of available congestion control values */
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void tcp_get_available_congestion_control(char *buf, size_t maxlen)
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{
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struct tcp_congestion_ops *ca;
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size_t offs = 0;
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rcu_read_lock();
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list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
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offs += snprintf(buf + offs, maxlen - offs,
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"%s%s",
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offs == 0 ? "" : " ", ca->name);
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}
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rcu_read_unlock();
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}
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/* Get current default congestion control */
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void tcp_get_default_congestion_control(char *name)
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{
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struct tcp_congestion_ops *ca;
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/* We will always have reno... */
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BUG_ON(list_empty(&tcp_cong_list));
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rcu_read_lock();
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ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list);
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strncpy(name, ca->name, TCP_CA_NAME_MAX);
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rcu_read_unlock();
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}
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/* Built list of non-restricted congestion control values */
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void tcp_get_allowed_congestion_control(char *buf, size_t maxlen)
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{
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struct tcp_congestion_ops *ca;
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size_t offs = 0;
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*buf = '\0';
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rcu_read_lock();
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list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
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if (!(ca->flags & TCP_CONG_NON_RESTRICTED))
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continue;
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offs += snprintf(buf + offs, maxlen - offs,
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"%s%s",
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offs == 0 ? "" : " ", ca->name);
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}
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rcu_read_unlock();
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}
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/* Change list of non-restricted congestion control */
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int tcp_set_allowed_congestion_control(char *val)
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{
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struct tcp_congestion_ops *ca;
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char *clone, *name;
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int ret = 0;
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clone = kstrdup(val, GFP_USER);
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if (!clone)
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return -ENOMEM;
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spin_lock(&tcp_cong_list_lock);
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/* pass 1 check for bad entries */
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while ((name = strsep(&clone, " ")) && *name) {
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ca = tcp_ca_find(name);
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if (!ca) {
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ret = -ENOENT;
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goto out;
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}
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}
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/* pass 2 clear old values */
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list_for_each_entry_rcu(ca, &tcp_cong_list, list)
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ca->flags &= ~TCP_CONG_NON_RESTRICTED;
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/* pass 3 mark as allowed */
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while ((name = strsep(&val, " ")) && *name) {
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ca = tcp_ca_find(name);
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WARN_ON(!ca);
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if (ca)
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ca->flags |= TCP_CONG_NON_RESTRICTED;
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}
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out:
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spin_unlock(&tcp_cong_list_lock);
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return ret;
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}
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/* Change congestion control for socket */
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int tcp_set_congestion_control(struct sock *sk, const char *name)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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struct tcp_congestion_ops *ca;
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int err = 0;
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rcu_read_lock();
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ca = tcp_ca_find(name);
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/* no change asking for existing value */
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if (ca == icsk->icsk_ca_ops)
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goto out;
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#ifdef CONFIG_KMOD
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/* not found attempt to autoload module */
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if (!ca && capable(CAP_SYS_MODULE)) {
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rcu_read_unlock();
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request_module("tcp_%s", name);
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rcu_read_lock();
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ca = tcp_ca_find(name);
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}
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#endif
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if (!ca)
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err = -ENOENT;
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else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || capable(CAP_NET_ADMIN)))
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err = -EPERM;
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else if (!try_module_get(ca->owner))
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err = -EBUSY;
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else {
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tcp_cleanup_congestion_control(sk);
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icsk->icsk_ca_ops = ca;
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if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init)
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icsk->icsk_ca_ops->init(sk);
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}
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out:
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rcu_read_unlock();
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return err;
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}
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/* RFC2861 Check whether we are limited by application or congestion window
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* This is the inverse of cwnd check in tcp_tso_should_defer
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*/
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int tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight)
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{
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const struct tcp_sock *tp = tcp_sk(sk);
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u32 left;
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if (in_flight >= tp->snd_cwnd)
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return 1;
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left = tp->snd_cwnd - in_flight;
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if (sk_can_gso(sk) &&
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left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd &&
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left * tp->mss_cache < sk->sk_gso_max_size)
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return 1;
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return left <= tcp_max_burst(tp);
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}
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EXPORT_SYMBOL_GPL(tcp_is_cwnd_limited);
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/*
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* Slow start is used when congestion window is less than slow start
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* threshold. This version implements the basic RFC2581 version
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* and optionally supports:
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* RFC3742 Limited Slow Start - growth limited to max_ssthresh
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* RFC3465 Appropriate Byte Counting - growth limited by bytes acknowledged
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*/
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void tcp_slow_start(struct tcp_sock *tp)
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{
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int cnt; /* increase in packets */
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/* RFC3465: ABC Slow start
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* Increase only after a full MSS of bytes is acked
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*
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* TCP sender SHOULD increase cwnd by the number of
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* previously unacknowledged bytes ACKed by each incoming
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* acknowledgment, provided the increase is not more than L
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*/
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if (sysctl_tcp_abc && tp->bytes_acked < tp->mss_cache)
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return;
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if (sysctl_tcp_max_ssthresh > 0 && tp->snd_cwnd > sysctl_tcp_max_ssthresh)
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cnt = sysctl_tcp_max_ssthresh >> 1; /* limited slow start */
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else
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cnt = tp->snd_cwnd; /* exponential increase */
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/* RFC3465: ABC
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* We MAY increase by 2 if discovered delayed ack
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*/
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if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache)
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cnt <<= 1;
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tp->bytes_acked = 0;
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tp->snd_cwnd_cnt += cnt;
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while (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
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tp->snd_cwnd_cnt -= tp->snd_cwnd;
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if (tp->snd_cwnd < tp->snd_cwnd_clamp)
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tp->snd_cwnd++;
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}
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}
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EXPORT_SYMBOL_GPL(tcp_slow_start);
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/*
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* TCP Reno congestion control
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* This is special case used for fallback as well.
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*/
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/* This is Jacobson's slow start and congestion avoidance.
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* SIGCOMM '88, p. 328.
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*/
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void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
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{
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struct tcp_sock *tp = tcp_sk(sk);
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if (!tcp_is_cwnd_limited(sk, in_flight))
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return;
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/* In "safe" area, increase. */
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if (tp->snd_cwnd <= tp->snd_ssthresh)
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tcp_slow_start(tp);
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/* In dangerous area, increase slowly. */
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else if (sysctl_tcp_abc) {
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/* RFC3465: Appropriate Byte Count
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* increase once for each full cwnd acked
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*/
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if (tp->bytes_acked >= tp->snd_cwnd*tp->mss_cache) {
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tp->bytes_acked -= tp->snd_cwnd*tp->mss_cache;
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if (tp->snd_cwnd < tp->snd_cwnd_clamp)
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tp->snd_cwnd++;
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}
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} else {
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/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd */
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if (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
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if (tp->snd_cwnd < tp->snd_cwnd_clamp)
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tp->snd_cwnd++;
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tp->snd_cwnd_cnt = 0;
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} else
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tp->snd_cwnd_cnt++;
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}
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}
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EXPORT_SYMBOL_GPL(tcp_reno_cong_avoid);
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/* Slow start threshold is half the congestion window (min 2) */
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u32 tcp_reno_ssthresh(struct sock *sk)
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{
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const struct tcp_sock *tp = tcp_sk(sk);
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return max(tp->snd_cwnd >> 1U, 2U);
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}
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EXPORT_SYMBOL_GPL(tcp_reno_ssthresh);
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/* Lower bound on congestion window with halving. */
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u32 tcp_reno_min_cwnd(const struct sock *sk)
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{
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const struct tcp_sock *tp = tcp_sk(sk);
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return tp->snd_ssthresh/2;
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}
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EXPORT_SYMBOL_GPL(tcp_reno_min_cwnd);
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struct tcp_congestion_ops tcp_reno = {
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.flags = TCP_CONG_NON_RESTRICTED,
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.name = "reno",
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.owner = THIS_MODULE,
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.ssthresh = tcp_reno_ssthresh,
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.cong_avoid = tcp_reno_cong_avoid,
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.min_cwnd = tcp_reno_min_cwnd,
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};
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/* Initial congestion control used (until SYN)
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* really reno under another name so we can tell difference
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* during tcp_set_default_congestion_control
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*/
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struct tcp_congestion_ops tcp_init_congestion_ops = {
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.name = "",
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.owner = THIS_MODULE,
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.ssthresh = tcp_reno_ssthresh,
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.cong_avoid = tcp_reno_cong_avoid,
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.min_cwnd = tcp_reno_min_cwnd,
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};
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EXPORT_SYMBOL_GPL(tcp_init_congestion_ops);
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