[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>

1 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index db428085658..bbcc8deda17 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -351,6 +351,12 @@ tcp_frto - BOOLEAN
         where packet loss is typically due to random radio interference
         rather than intermediate router congestion.
 
+tcp_allowed_congestion_control - STRING
+        Show/set the congestion control choices available to non-privileged
+        processes. The list is a subset of those listed in
+        tcp_available_congestion_control.
+        Default is "reno" and the default setting (tcp_congestion_control).
+
 tcp_available_congestion_control - STRING
         Shows the available congestion control choices that are registered.
         More congestion control algorithms may be available as modules,