[TCP]: Congestion control initialization.

Change to defer congestion control initialization.

If setsockopt() was used to change TCP_CONGESTION before
connection is established, then protocols that use sequence numbers
to keep track of one RTT interval (vegas, illinois, ...) get confused.

Change the init hook to be called after handshake.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 5c8caf4a1244404631e162c0d93e1f2e28e77f73..34ae3f13483a6e37b65402e3318bd635b716e460 100644 (file)
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -77,18 +77,19 @@ void tcp_init_congestion_control(struct sock *sk)
        struct inet_connection_sock *icsk = inet_csk(sk);
        struct tcp_congestion_ops *ca;
 
-       if (icsk->icsk_ca_ops != &tcp_init_congestion_ops)
-               return;
+       /* 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;
+                       }
 
-       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();
        }
-       rcu_read_unlock();
 
        if (icsk->icsk_ca_ops->init)
                icsk->icsk_ca_ops->init(sk);
@@ -236,6 +237,7 @@ int tcp_set_congestion_control(struct sock *sk, const char *name)
 
        rcu_read_lock();
        ca = tcp_ca_find(name);
+
        /* no change asking for existing value */
        if (ca == icsk->icsk_ca_ops)
                goto out;
@@ -261,7 +263,8 @@ int tcp_set_congestion_control(struct sock *sk, const char *name)
        else {
                tcp_cleanup_congestion_control(sk);
                icsk->icsk_ca_ops = ca;
-               if (icsk->icsk_ca_ops->init)
+
+               if (sk->sk_state != TCP_CLOSE && icsk->icsk_ca_ops->init)
                        icsk->icsk_ca_ops->init(sk);
        }
  out: