[TCP]: Allow autoloading of congestion control via setsockopt.

If user has permision to load modules, then autoload then attempt
autoload of TCP congestion module.

Signed-off-by: Stephen Hemminger <shemminger@osdl.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 343d619..5ca7723 100644 (file)
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -113,7 +113,7 @@ int tcp_set_default_congestion_control(const char *name)
        spin_lock(&tcp_cong_list_lock);
        ca = tcp_ca_find(name);
 #ifdef CONFIG_KMOD
-       if (!ca) {
+       if (!ca && capable(CAP_SYS_MODULE)) {
                spin_unlock(&tcp_cong_list_lock);
 
                request_module("tcp_%s", name);
@@ -236,9 +236,19 @@ 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;
 
+#ifdef CONFIG_KMOD
+       /* not found attempt to autoload module */
+       if (!ca && capable(CAP_SYS_MODULE)) {
+               rcu_read_unlock();
+               request_module("tcp_%s", name);
+               rcu_read_lock();
+               ca = tcp_ca_find(name);
+       }
+#endif
        if (!ca)
                err = -ENOENT;