[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>

1 files changed, 26 insertions, 0 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index a0f6842368c3..d3aae1f9b4c1 100644
--- 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