[TCP]: Restrict congestion control choices.

Allow normal users to only choose among a restricted set of congestion
control choices.  The default is reno and what ever has been configured
as default. But the policy can be changed by administrator at any time.

For example, to allow any choice:
    cp /proc/sys/net/ipv4/tcp_available_congestion_control \
       /proc/sys/net/ipv4/tcp_allowed_congestion_control

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

2 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 28a48279654d..0725441621d0 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -427,6 +427,7 @@ enum
         NET_CIPSOV4_RBM_OPTFMT=120,
         NET_CIPSOV4_RBM_STRICTVALID=121,
         NET_TCP_AVAIL_CONG_CONTROL=122,
+        NET_TCP_ALLOWED_CONG_CONTROL=123,
 };
 
 enum {
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 6af4baf5b769..e1a5d29d0a1f 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -625,6 +625,7 @@ enum tcp_ca_event {
 
 struct tcp_congestion_ops {
         struct list_head        list;
+        int     non_restricted;
 
         /* initialize private data (optional) */
         void (*init)(struct sock *sk);
@@ -663,6 +664,8 @@ extern void tcp_cleanup_congestion_control(struct sock *sk);
 extern int tcp_set_default_congestion_control(const char *name);
 extern void tcp_get_default_congestion_control(char *name);
 extern void tcp_get_available_congestion_control(char *buf, size_t len);
+extern void tcp_get_allowed_congestion_control(char *buf, size_t len);
+extern int tcp_set_allowed_congestion_control(char *allowed);
 extern int tcp_set_congestion_control(struct sock *sk, const char *name);
 extern void tcp_slow_start(struct tcp_sock *tp);