1 files changed, 425 insertions, 0 deletions
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
new file mode 100644
index 00000000..272a8459
--- /dev/null
+++ b/net/ipv4/tcp_cong.c
@@ -0,0 +1,425 @@
+/*
+ * Plugable TCP congestion control support and newReno
+ * congestion control.
+ * Based on ideas from I/O scheduler suport 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 <net/tcp.h>
+
+int sysctl_tcp_max_ssthresh = 0;
+
+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;
+}
+
+/*
+ * 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) {
+		pr_err("%s does not implement required ops\n", ca->name);
+		return -EINVAL;
+	}
+
+	spin_lock(&tcp_cong_list_lock);
+	if (tcp_ca_find(ca->name)) {
+		pr_notice("%s already registered\n", ca->name);
+		ret = -EEXIST;
+	} else {
+		list_add_tail_rcu(&ca->list, &tcp_cong_list);
+		pr_info("%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);
+}
+EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
+
+/* Assign choice of congestion control. */
+void tcp_init_congestion_control(struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct tcp_congestion_ops *ca;
+
+	/* if no choice made yet assign the current value set as default */
+	if (icsk->icsk_ca_ops == &tcp_init_congestion_ops) {
+		rcu_read_lock();
+		list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
+			if (try_module_get(ca->owner)) {
+				icsk->icsk_ca_ops = ca;
+				break;
+			}
+
+			/* fallback to next available */
+		}
+		rcu_read_unlock();
+	}
+
+	if (icsk->icsk_ca_ops->init)
+		icsk->icsk_ca_ops->init(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 ? "" : " ", 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 */
+int tcp_set_congestion_control(struct sock *sk, const char *name)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+	struct tcp_congestion_ops *ca;
+	int err = 0;
+
+	rcu_read_lock();
+	ca = tcp_ca_find(name);
+
+	/* no change asking for existing value */
+	if (ca == icsk->icsk_ca_ops)
+		goto out;
+
+#ifdef CONFIG_MODULES
+	/* not found attempt to autoload module */
+	if (!ca && capable(CAP_NET_ADMIN)) {
+		rcu_read_unlock();
+		request_module("tcp_%s", name);
+		rcu_read_lock();
+		ca = tcp_ca_find(name);
+	}
+#endif
+	if (!ca)
+		err = -ENOENT;
+
+	else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || capable(CAP_NET_ADMIN)))
+		err = -EPERM;
+
+	else if (!try_module_get(ca->owner))
+		err = -EBUSY;
+
+	else {
+		tcp_cleanup_congestion_control(sk);
+		icsk->icsk_ca_ops = ca;
+
+		if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init)
+			icsk->icsk_ca_ops->init(sk);
+	}
+ out:
+	rcu_read_unlock();
+	return err;
+}
+
+/* RFC2861 Check whether we are limited by application or congestion window
+ * This is the inverse of cwnd check in tcp_tso_should_defer
+ */
+int tcp_is_cwnd_limited(const struct sock *sk, u32 in_flight)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	u32 left;
+
+	if (in_flight >= tp->snd_cwnd)
+		return 1;
+
+	left = tp->snd_cwnd - in_flight;
+	if (sk_can_gso(sk) &&
+	    left * sysctl_tcp_tso_win_divisor < tp->snd_cwnd &&
+	    left * tp->mss_cache < sk->sk_gso_max_size)
+		return 1;
+	return left <= tcp_max_tso_deferred_mss(tp);
+}
+EXPORT_SYMBOL_GPL(tcp_is_cwnd_limited);
+
+/*
+ * Slow start is used when congestion window is less than slow start
+ * threshold. This version implements the basic RFC2581 version
+ * and optionally supports:
+ * 	RFC3742 Limited Slow Start  	  - growth limited to max_ssthresh
+ *	RFC3465 Appropriate Byte Counting - growth limited by bytes acknowledged
+ */
+void tcp_slow_start(struct tcp_sock *tp)
+{
+	int cnt; /* increase in packets */
+
+	/* RFC3465: ABC Slow start
+	 * Increase only after a full MSS of bytes is acked
+	 *
+	 * TCP sender SHOULD increase cwnd by the number of
+	 * previously unacknowledged bytes ACKed by each incoming
+	 * acknowledgment, provided the increase is not more than L
+	 */
+	if (sysctl_tcp_abc && tp->bytes_acked < tp->mss_cache)
+		return;
+
+	if (sysctl_tcp_max_ssthresh > 0 && tp->snd_cwnd > sysctl_tcp_max_ssthresh)
+		cnt = sysctl_tcp_max_ssthresh >> 1;	/* limited slow start */
+	else
+		cnt = tp->snd_cwnd;			/* exponential increase */
+
+	/* RFC3465: ABC
+	 * We MAY increase by 2 if discovered delayed ack
+	 */
+	if (sysctl_tcp_abc > 1 && tp->bytes_acked >= 2*tp->mss_cache)
+		cnt <<= 1;
+	tp->bytes_acked = 0;
+
+	tp->snd_cwnd_cnt += cnt;
+	while (tp->snd_cwnd_cnt >= tp->snd_cwnd) {
+		tp->snd_cwnd_cnt -= tp->snd_cwnd;
+		if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+			tp->snd_cwnd++;
+	}
+}
+EXPORT_SYMBOL_GPL(tcp_slow_start);
+
+/* In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd (or alternative w) */
+void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w)
+{
+	if (tp->snd_cwnd_cnt >= w) {
+		if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+			tp->snd_cwnd++;
+		tp->snd_cwnd_cnt = 0;
+	} else {
+		tp->snd_cwnd_cnt++;
+	}
+}
+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 in_flight)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	if (!tcp_is_cwnd_limited(sk, in_flight))
+		return;
+
+	/* In "safe" area, increase. */
+	if (tp->snd_cwnd <= tp->snd_ssthresh)
+		tcp_slow_start(tp);
+
+	/* In dangerous area, increase slowly. */
+	else if (sysctl_tcp_abc) {
+		/* RFC3465: Appropriate Byte Count
+		 * increase once for each full cwnd acked
+		 */
+		if (tp->bytes_acked >= tp->snd_cwnd*tp->mss_cache) {
+			tp->bytes_acked -= tp->snd_cwnd*tp->mss_cache;
+			if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+				tp->snd_cwnd++;
+		}
+	} else {
+		tcp_cong_avoid_ai(tp, tp->snd_cwnd);
+	}
+}
+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);
+
+/* Lower bound on congestion window with halving. */
+u32 tcp_reno_min_cwnd(const struct sock *sk)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	return tp->snd_ssthresh/2;
+}
+EXPORT_SYMBOL_GPL(tcp_reno_min_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,
+	.min_cwnd	= tcp_reno_min_cwnd,
+};
+
+/* Initial congestion control used (until SYN)
+ * really reno under another name so we can tell difference
+ * during tcp_set_default_congestion_control
+ */
+struct tcp_congestion_ops tcp_init_congestion_ops  = {
+	.name		= "",
+	.owner		= THIS_MODULE,
+	.ssthresh	= tcp_reno_ssthresh,
+	.cong_avoid	= tcp_reno_cong_avoid,
+	.min_cwnd	= tcp_reno_min_cwnd,
+};
+EXPORT_SYMBOL_GPL(tcp_init_congestion_ops);