Re: question about linux tcp request queue handling

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The 4.4BSD-Lite code described in Stevens is long outdated.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?