tcp: Namespace-ify sysctl_tcp_default_congestion_control

Make default TCP default congestion control to a per namespace
value. This changes default congestion control to a pointer to congestion ops
(rather than implicit as first element of available lsit).

The congestion control setting of new namespaces is inherited
from the current setting of the root namespace.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 0 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 1eac84b8044e..c6bc0c4d19c6 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2430,6 +2430,8 @@ static void __net_exit tcp_sk_exit(struct net *net)
 {
         int cpu;
 
+        module_put(net->ipv4.tcp_congestion_control->owner);
+
         for_each_possible_cpu(cpu)
                 inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.tcp_sk, cpu));
         free_percpu(net->ipv4.tcp_sk);
@@ -2522,6 +2524,13 @@ static int __net_init tcp_sk_init(struct net *net)
         net->ipv4.sysctl_tcp_fastopen_blackhole_timeout = 60 * 60;
         atomic_set(&net->ipv4.tfo_active_disable_times, 0);
 
+        /* Reno is always built in */
+        if (!net_eq(net, &init_net) &&
+            try_module_get(init_net.ipv4.tcp_congestion_control->owner))
+                net->ipv4.tcp_congestion_control = init_net.ipv4.tcp_congestion_control;
+        else
+                net->ipv4.tcp_congestion_control = &tcp_reno;
+
         return 0;
 fail:
         tcp_sk_exit(net);