tcp: Remove TCPCT

TCPCT uses option-number 253, reserved for experimental use and should
not be used in production environments.
Further, TCPCT does not fully implement RFC 6013.

As a nice side-effect, removing TCPCT increases TCP's performance for
very short flows:

Doing an apache-benchmark with -c 100 -n 100000, sending HTTP-requests
for files of 1KB size.

before this patch:
	average (among 7 runs) of 20845.5 Requests/Second
after:
	average (among 7 runs) of 21403.6 Requests/Second

Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 0 insertions, 8 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 18a24c405ac0..17953e2bc3e9 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -175,14 +175,6 @@ tcp_congestion_control - STRING
         is inherited.
         [see setsockopt(listenfd, SOL_TCP, TCP_CONGESTION, "name" ...) ]
 
-tcp_cookie_size - INTEGER
-        Default size of TCP Cookie Transactions (TCPCT) option, that may be
-        overridden on a per socket basis by the TCPCT socket option.
-        Values greater than the maximum (16) are interpreted as the maximum.
-        Values greater than zero and less than the minimum (8) are interpreted
-        as the minimum.  Odd values are interpreted as the next even value.
-        Default: 0 (off).
-
 tcp_dsack - BOOLEAN
         Allows TCP to send "duplicate" SACKs.