1 files changed, 488 insertions, 0 deletions
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
new file mode 100644
index 000000000..d3cae4074
--- /dev/null
+++ b/net/ipv4/tcp_cong.c
@@ -0,0 +1,488 @@
+// 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>
+#include <trace/events/tcp.h>
+
+static DEFINE_SPINLOCK(tcp_cong_list_lock);
+static LIST_HEAD(tcp_cong_list);
+
+/* Simple linear search, don't expect many entries! */
+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;
+}
+
+void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+
+	trace_tcp_cong_state_set(sk, ca_state);
+
+	if (icsk->icsk_ca_ops->set_state)
+		icsk->icsk_ca_ops->set_state(sk, ca_state);
+	icsk->icsk_ca_state = ca_state;
+}
+
+/* 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;
+}
+
+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;
+}
+
+/* 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(!bpf_try_module_get(ca, 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)
+{
+	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);
+	icsk->icsk_ca_initialized = 1;
+}
+
+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 (ca->flags & TCP_CONG_NEEDS_ECN)
+		INET_ECN_xmit(sk);
+	else
+		INET_ECN_dontxmit(sk);
+
+	if (!((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)))
+		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);
+	bpf_module_put(icsk->icsk_ca_ops, 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 (!bpf_try_module_get(ca, ca->owner)) {
+		ret = -EBUSY;
+	} else if (!net_eq(net, &init_net) &&
+			!(ca->flags & TCP_CONG_NON_RESTRICTED)) {
+		/* Only init netns can set default to a restricted algorithm */
+		ret = -EPERM;
+	} else {
+		prev = xchg(&net->ipv4.tcp_congestion_control, ca);
+		if (prev)
+			bpf_module_put(prev, 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);
+
+		if (WARN_ON_ONCE(offs >= maxlen))
+			break;
+	}
+	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);
+
+		if (WARN_ON_ONCE(offs >= maxlen))
+			break;
+	}
+	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 cap_net_admin)
+{
+	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 (!((ca->flags & TCP_CONG_NON_RESTRICTED) || cap_net_admin))
+		err = -EPERM;
+	else if (!bpf_try_module_get(ca, 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(tcp_snd_cwnd(tp) + acked, tp->snd_ssthresh);
+
+	acked -= cwnd - tcp_snd_cwnd(tp);
+	tcp_snd_cwnd_set(tp, 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;
+		tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + 1);
+	}
+
+	tp->snd_cwnd_cnt += acked;
+	if (tp->snd_cwnd_cnt >= w) {
+		u32 delta = tp->snd_cwnd_cnt / w;
+
+		tp->snd_cwnd_cnt -= delta * w;
+		tcp_snd_cwnd_set(tp, tcp_snd_cwnd(tp) + delta);
+	}
+	tcp_snd_cwnd_set(tp, min(tcp_snd_cwnd(tp), 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, tcp_snd_cwnd(tp), 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(tcp_snd_cwnd(tp) >> 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(tcp_snd_cwnd(tp), 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,
+};