[TCP]: Document several sysctls.

This adds documentation for tcp_moderate_rcvbuf, tcp_no_metrics_save,
tcp_base_mss, and tcp_mtu_probing.

Signed-off-by: John Heffner <jheffner@psc.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index a0f6842368c37b77b571c5817029adaf45db1769..d3aae1f9b4c1970f5d119be92e54549d19640be3 100644 (file)
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -147,6 +147,11 @@ tcp_available_congestion_control - STRING
        More congestion control algorithms may be available as modules,
        but not loaded.
 
+tcp_base_mss - INTEGER
+       The initial value of search_low to be used by Packetization Layer
+       Path MTU Discovery (MTU probing).  If MTU probing is enabled,
+       this is the inital MSS used by the connection.
+
 tcp_congestion_control - STRING
        Set the congestion control algorithm to be used for new
        connections. The algorithm "reno" is always available, but
@@ -243,6 +248,27 @@ tcp_mem - vector of 3 INTEGERs: min, pressure, max
        Defaults are calculated at boot time from amount of available
        memory.
 
+tcp_moderate_rcvbuf - BOOLEAN
+       If set, TCP performs receive buffer autotuning, attempting to
+       automatically size the buffer (no greater than tcp_rmem[2]) to
+       match the size required by the path for full throughput.  Enabled by
+       default.
+
+tcp_mtu_probing - INTEGER
+       Controls TCP Packetization-Layer Path MTU Discovery.  Takes three
+       values:
+         0 - Disabled
+         1 - Disabled by default, enabled when an ICMP black hole detected
+         2 - Always enabled, use initial MSS of tcp_base_mss.
+
+tcp_no_metrics_save - BOOLEAN
+       By default, TCP saves various connection metrics in the route cache
+       when the connection closes, so that connections established in the
+       near future can use these to set initial conditions.  Usually, this
+       increases overall performance, but may sometimes cause performance
+       degredation.  If set, TCP will not cache metrics on closing
+       connections.
+
 tcp_orphan_retries - INTEGER
        How may times to retry before killing TCP connection, closed
        by our side. Default value 7 corresponds to ~50sec-16min