netdev - [net-next-2.6 PATCH v6 4/7 RFC] TCPCT part 1d: define TCP cookie option, extend existing struct's

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Date:	Thu, 12 Nov 2009 23:53:48 -0500
From:	William Allen Simpson <william.allen.simpson@...il.com>
To:	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: [net-next-2.6 PATCH v6 4/7 RFC] TCPCT part 1d: define TCP cookie
 option, extend existing struct's

Data structures are carefully composed to require minimal additions.
For example, the struct tcp_options_received cookie_plus variable fits
between existing 16-bit and 8-bit variables, requiring no additional
space (taking alignment into consideration).  There are no additions to
tcp_request_sock, and only 1 pointer in tcp_sock.

This is a significantly revised 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

The principle difference is using a TCP option to carry the cookie nonce,
instead of a user configured offset in the data.  This is more flexible and
less subject to user configuration error.  Such a cookie option has been
suggested for many years, and is also useful without SYN data, allowing
several related concepts to use the same extension option.

    "Re: SYN floods (was: does history repeat itself?)", September 9, 1996.
    http://www.merit.net/mail.archives/nanog/1996-09/msg00235.html

    "Re: what a new TCP header might look like", May 12, 1998.
    ftp://ftp.isi.edu/end2end/end2end-interest-1998.mail

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

Requires:
   TCPCT part 1a: add request_values parameter for sending SYNACK
   TCPCT part 1b: generate Responder Cookie
   TCPCT part 1c: sysctl_tcp_cookie_size, socket option TCP_COOKIE_TRANSACTIONS

Signed-off-by: William.Allen.Simpson@...il.com
---
  include/linux/tcp.h |   29 ++++++++++++++++----
  include/net/tcp.h   |   72 +++++++++++++++++++++++++++++++++++++++++++++++++++
  2 files changed, 95 insertions(+), 6 deletions(-)

View attachment "TCPCT+1d6.patch" of type "text/plain" (6049 bytes)