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Re: question about linux tcp request queue handling

To: "Andi Kleen" <ak@xxxxxxx>
Subject: Re: question about linux tcp request queue handling
From: "Paul Albrecht" <palbrecht@xxxxxxxxx>
Date: Tue, 8 Jul 2003 12:23:37 -0700
Cc: niv@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, "netdev" <netdev@xxxxxxxxxxx>
References: <3F08858E.8000907@us.ibm.com.suse.lists.linux.kernel><001a01c3441c$6fe111a0$6801a8c0@oemcomputer.suse.lists.linux.kernel><3F08B7E2.7040208@us.ibm.com.suse.lists.linux.kernel><000d01c3444f$e6439600$6801a8c0@oemcomputer.suse.lists.linux.kernel><3F090A4F.10004@us.ibm.com.suse.lists.linux.kernel><001401c344df$ccbc63c0$6801a8c0@oemcomputer.suse.lists.linux.kernel> <p73fzliqa91.fsf@oldwotan.suse.de>
Sender: netdev-bounce@xxxxxxxxxxx
Andi Kleen writes:

>
> The 4.4BSD-Lite code described in Stevens is long outdated. All modern
> BSDs (and probably most other Unixes too) do it in a similar way to what
> Nivedita described. The keywords are "syn flood attack" and "DoS".
>

I have attached a copy of tcpdump output for two linux systems connected
over ether replaying the scenario for incoming request queue handling given
in Stevens's TCP/IP Illustrated Volume 1: The Protocols.  What I don't
understand about the third handshake is if the server is going to send the
syn/ack in response the client's initial syn then why does server repeatly
ignore the subsequent ack from the client?

Attachment: trace.txt
Description: Text document

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