1 files changed, 36 insertions, 40 deletions

diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 2f26124fd160..bc6c02f16243 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -33,9 +33,11 @@ static struct tcp_congestion_ops *tcp_ca_find(const char *name)
 }
 
 /* Must be called with rcu lock held */
-static const struct tcp_congestion_ops *__tcp_ca_find_autoload(const char *name)
+static struct tcp_congestion_ops *tcp_ca_find_autoload(struct net *net,
+						       const char *name)
 {
-	const struct tcp_congestion_ops *ca = tcp_ca_find(name);
+	struct tcp_congestion_ops *ca = tcp_ca_find(name);
+
 #ifdef CONFIG_MODULES
 	if (!ca && capable(CAP_NET_ADMIN)) {
 		rcu_read_unlock();
@@ -115,7 +117,7 @@ void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
 }
 EXPORT_SYMBOL_GPL(tcp_unregister_congestion_control);
 
-u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca)
+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;
@@ -123,7 +125,7 @@ u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca)
 	might_sleep();
 
 	rcu_read_lock();
-	ca = __tcp_ca_find_autoload(name);
+	ca = tcp_ca_find_autoload(net, name);
 	if (ca) {
 		key = ca->key;
 		*ecn_ca = ca->flags & TCP_CONG_NEEDS_ECN;
@@ -153,23 +155,18 @@ 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);
-	struct tcp_congestion_ops *ca;
+	const struct tcp_congestion_ops *ca;
 
 	rcu_read_lock();
-	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
-		if (likely(try_module_get(ca->owner))) {
-			icsk->icsk_ca_ops = ca;
-			goto out;
-		}
-		/* Fallback to next available. The last really
-		 * guaranteed fallback is Reno from this list.
-		 */
-	}
-out:
+	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));
 
+	memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
 	if (ca->flags & TCP_CONG_NEEDS_ECN)
 		INET_ECN_xmit(sk);
 	else
@@ -214,29 +211,27 @@ void tcp_cleanup_congestion_control(struct sock *sk)
 }
 
 /* Used by sysctl to change default congestion control */
-int tcp_set_default_congestion_control(const char *name)
+int tcp_set_default_congestion_control(struct net *net, 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);
+	const struct tcp_congestion_ops *prev;
+	int ret;
 
-		request_module("tcp_%s", name);
-		spin_lock(&tcp_cong_list_lock);
-		ca = tcp_ca_find(name);
-	}
-#endif
+	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);
 
-	if (ca) {
-		ca->flags |= TCP_CONG_NON_RESTRICTED;	/* default is always allowed */
-		list_move(&ca->list, &tcp_cong_list);
+		ca->flags |= TCP_CONG_NON_RESTRICTED;
 		ret = 0;
 	}
-	spin_unlock(&tcp_cong_list_lock);
+	rcu_read_unlock();
 
 	return ret;
 }
@@ -244,7 +239,8 @@ int tcp_set_default_congestion_control(const char *name)
 /* 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);
+	return tcp_set_default_congestion_control(&init_net,
+						  CONFIG_DEFAULT_TCP_CONG);
 }
 late_initcall(tcp_congestion_default);
 
@@ -264,14 +260,12 @@ void tcp_get_available_congestion_control(char *buf, size_t maxlen)
 }
 
 /* Get current default congestion control */
-void tcp_get_default_congestion_control(char *name)
+void tcp_get_default_congestion_control(struct net *net, char *name)
 {
-	struct tcp_congestion_ops *ca;
-	/* We will always have reno... */
-	BUG_ON(list_empty(&tcp_cong_list));
+	const struct tcp_congestion_ops *ca;
 
 	rcu_read_lock();
-	ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list);
+	ca = rcu_dereference(net->ipv4.tcp_congestion_control);
 	strncpy(name, ca->name, TCP_CA_NAME_MAX);
 	rcu_read_unlock();
 }
@@ -351,12 +345,14 @@ int tcp_set_congestion_control(struct sock *sk, const char *name, bool load, boo
 	if (!load)
 		ca = tcp_ca_find(name);
 	else
-		ca = __tcp_ca_find_autoload(name);
+		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) {