449 lines
11 KiB
C
449 lines
11 KiB
C
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/*
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* Pluggable TCP congestion control support and newReno
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* congestion control.
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* Based on ideas from I/O scheduler support 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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#define pr_fmt(fmt) "TCP: " fmt
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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 <linux/gfp.h>
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#include <linux/jhash.h>
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#include <net/tcp.h>
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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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/* Must be called with rcu lock held */
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static const struct tcp_congestion_ops *__tcp_ca_find_autoload(const char *name)
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{
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const struct tcp_congestion_ops *ca = tcp_ca_find(name);
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#ifdef CONFIG_MODULES
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if (!ca && capable(CAP_NET_ADMIN)) {
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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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return ca;
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}
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/* Simple linear search, not much in here. */
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struct tcp_congestion_ops *tcp_ca_find_key(u32 key)
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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 (e->key == key)
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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 || ca->cong_control)) {
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pr_err("%s does not implement required ops\n", ca->name);
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return -EINVAL;
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}
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ca->key = jhash(ca->name, sizeof(ca->name), strlen(ca->name));
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spin_lock(&tcp_cong_list_lock);
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if (ca->key == TCP_CA_UNSPEC || tcp_ca_find_key(ca->key)) {
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pr_notice("%s already registered or non-unique key\n",
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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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pr_debug("%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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/* Wait for outstanding readers to complete before the
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* module gets removed entirely.
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*
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* A try_module_get() should fail by now as our module is
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* in "going" state since no refs are held anymore and
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* module_exit() handler being called.
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*/
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synchronize_rcu();
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}
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EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
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u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca)
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{
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const struct tcp_congestion_ops *ca;
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u32 key = TCP_CA_UNSPEC;
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might_sleep();
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rcu_read_lock();
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ca = __tcp_ca_find_autoload(name);
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if (ca) {
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key = ca->key;
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*ecn_ca = ca->flags & TCP_CONG_NEEDS_ECN;
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}
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rcu_read_unlock();
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return key;
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}
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EXPORT_SYMBOL_GPL(tcp_ca_get_key_by_name);
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char *tcp_ca_get_name_by_key(u32 key, char *buffer)
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{
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const struct tcp_congestion_ops *ca;
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char *ret = NULL;
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rcu_read_lock();
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ca = tcp_ca_find_key(key);
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if (ca)
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ret = strncpy(buffer, ca->name,
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TCP_CA_NAME_MAX);
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rcu_read_unlock();
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return ret;
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}
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EXPORT_SYMBOL_GPL(tcp_ca_get_name_by_key);
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/* Assign choice of congestion control. */
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void tcp_assign_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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rcu_read_lock();
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list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
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if (likely(try_module_get(ca->owner))) {
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icsk->icsk_ca_ops = ca;
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goto out;
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}
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/* Fallback to next available. The last really
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* guaranteed fallback is Reno from this list.
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*/
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}
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out:
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rcu_read_unlock();
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memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
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if (ca->flags & TCP_CONG_NEEDS_ECN)
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INET_ECN_xmit(sk);
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else
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INET_ECN_dontxmit(sk);
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}
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void tcp_init_congestion_control(struct sock *sk)
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{
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const struct inet_connection_sock *icsk = inet_csk(sk);
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tcp_sk(sk)->prior_ssthresh = 0;
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if (icsk->icsk_ca_ops->init)
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icsk->icsk_ca_ops->init(sk);
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if (tcp_ca_needs_ecn(sk))
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INET_ECN_xmit(sk);
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else
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INET_ECN_dontxmit(sk);
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}
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static void tcp_reinit_congestion_control(struct sock *sk,
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const struct tcp_congestion_ops *ca)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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tcp_cleanup_congestion_control(sk);
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icsk->icsk_ca_ops = ca;
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icsk->icsk_ca_setsockopt = 1;
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memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
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if (!((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)))
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tcp_init_congestion_control(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_MODULES
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if (!ca && capable(CAP_NET_ADMIN)) {
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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 *saved_clone, *clone, *name;
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int ret = 0;
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saved_clone = 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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kfree(saved_clone);
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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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const struct tcp_congestion_ops *ca;
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int err = 0;
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if (icsk->icsk_ca_dst_locked)
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return -EPERM;
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rcu_read_lock();
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ca = __tcp_ca_find_autoload(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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icsk->icsk_ca_setsockopt = 1;
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goto out;
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}
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if (!ca)
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err = -ENOENT;
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else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) ||
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ns_capable(sock_net(sk)->user_ns, 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_reinit_congestion_control(sk, ca);
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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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/* Slow start is used when congestion window is no greater than the slow start
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* threshold. We base on RFC2581 and also handle stretch ACKs properly.
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* We do not implement RFC3465 Appropriate Byte Counting (ABC) per se but
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* something better;) a packet is only considered (s)acked in its entirety to
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* defend the ACK attacks described in the RFC. Slow start processes a stretch
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* ACK of degree N as if N acks of degree 1 are received back to back except
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* ABC caps N to 2. Slow start exits when cwnd grows over ssthresh and
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* returns the leftover acks to adjust cwnd in congestion avoidance mode.
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*/
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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);
|
||
|
|
|
||
|
|
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,
|
||
|
|
};
|