v4.19.13 snapshot.
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
new file mode 100644
index 0000000..bc6c02f
--- /dev/null
+++ b/net/ipv4/tcp_cong.c
@@ -0,0 +1,475 @@
+/*
+ * 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 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;
+}
+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 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(!try_module_get(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)
+{
+ const 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);
+}
+
+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 (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(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 (!try_module_get(ca->owner)) {
+ ret = -EBUSY;
+ } else {
+ prev = xchg(&net->ipv4.tcp_congestion_control, ca);
+ if (prev)
+ module_put(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);
+ }
+ 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);
+ }
+ 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 reinit)
+{
+ 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 (!load) {
+ const struct tcp_congestion_ops *old_ca = icsk->icsk_ca_ops;
+
+ if (try_module_get(ca->owner)) {
+ if (reinit) {
+ tcp_reinit_congestion_control(sk, ca);
+ } else {
+ icsk->icsk_ca_ops = ca;
+ module_put(old_ca->owner);
+ }
+ } else {
+ err = -EBUSY;
+ }
+ } else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) ||
+ ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))) {
+ err = -EPERM;
+ } else if (!try_module_get(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(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);
+
+u32 tcp_reno_undo_cwnd(struct sock *sk)
+{
+ const struct tcp_sock *tp = tcp_sk(sk);
+
+ return max(tp->snd_cwnd, 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,
+};