Re: [net-next-2.6 PATCH v4 2/3] TCPCT part 1b: sysctl_tcp_cookie_size, socket option TCP_COOKIE_TRANSACTIONS, functions

[Eric Dumazet <eric.dumazet@gmail.com>]

William Allen Simpson a écrit :
> 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.
> 
> Redefine two TCP header functions to accept TCP header pointer.
> When subtracting, return signed int to allow error checking.
> 
> 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).  The patch was previously reviewed:
> 
>    http://thread.gmane.org/gmane.linux.network/102586
> 
> These functions will also be used in subsequent patches that implement
> additional features.
> 
> Signed-off-by: William.Allen.Simpson@gmail.com
> ---
>  Documentation/networking/ip-sysctl.txt |    8 +++++
>  include/linux/tcp.h                    |   47
> +++++++++++++++++++++++++++++++-
>  include/net/tcp.h                      |    6 +---
>  net/ipv4/sysctl_net_ipv4.c             |    8 +++++
>  net/ipv4/tcp_output.c                  |    8 +++++
>  5 files changed, 71 insertions(+), 6 deletions(-)
> 

+#define TCP_EXTEND_TIMESTAMP	(1 << 4)	/* Initiate 64-bit timestamps */

What is this for ?