netdev - Re: [net-next-2.6 PATCH v4 3/3] TCPCT part 1c: initial SYN exchange with SYNACK data

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Message-ID: <4AE8527E.4080603@gmail.com>
Date:	Wed, 28 Oct 2009 15:17:34 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	William Allen Simpson <william.allen.simpson@...il.com>
CC:	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [net-next-2.6 PATCH v4 3/3] TCPCT part 1c: initial SYN exchange
 with SYNACK data

William Allen Simpson a écrit :
> 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).  That patch was previously reviewed:
> 
>    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

Sorry this link might be interesting to you, but I found nothing that explains
your patches.

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

Same here....

> 
> 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 and 1 flag byte in tcp_sock.
> 
> Allocations have been rearranged to avoid requiring GFP_ATOMIC, with
> only one unavoidable exception in tcp_create_openreq_child(), where the
> tcp_sock itself is created GFP_ATOMIC.
> 
> 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: sysctl_tcp_cookie_size, socket option
> TCP_COOKIE_TRANSACTIONS, functions
> 
> Signed-off-by: William.Allen.Simpson@...il.com

I tried to find an RFC or document about this stuff and failed.

Before reading implementation code, I like to have english text that describes
the new concept/design.

(BTW I found http://ttcplinux.sourceforge.net/theses/ETTCP.pdf and found it interesting,
I wonder what happened to this)

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