Define sysctl (tcp_cookie_size) to turn on and off the cookie option
default globally, instead of a compiled configuration option.

Define per socket option (TCP_COOKIE_TRANSACTIONS) for setting constant
data values, retrieving variable cookie values, and other facilities.

Move inline tcp_clear_options() unchanged from net/tcp.h to linux/tcp.h,
near its corresponding struct tcp_options_received (prior to changes).

This is a straightforward re-implementation of an earlier (year-old)
patch that no longer applies cleanly, with permission of the original
author (Adam Langley):

    http://thread.gmane.org/gmane.linux.network/102586

These functions will also be used in subsequent patches that implement
additional features.

Requires:
   net: TCP_MSS_DEFAULT, TCP_MSS_DESIRED

Signed-off-by: William.Allen.Simpson@gmail.com
---
  Documentation/networking/ip-sysctl.txt |    8 +++++++
  include/linux/tcp.h                    |   33 +++++++++++++++++++++++++++++++-
  include/net/tcp.h                      |    6 +----
  net/ipv4/sysctl_net_ipv4.c             |    8 +++++++
  net/ipv4/tcp_output.c                  |    3 ++
  5 files changed, 52 insertions(+), 6 deletions(-)