Messages in this thread | | | Date | Mon, 7 Jul 2003 21:14:48 -0700 | From | "Paul Albrecht" <> | Subject | Re: question about linux tcp request queue handling |
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Andi Kleen writes:
> > The 4.4BSD-Lite code described in Stevens is long outdated. >
I was referring to volume one subtitled: "The Protocols." It doesn't describe implementation and the examples are not limited to bsd-lite.
> >All modern BSDs (and probably most other Unixes too) do it in a similar way to what > Nivedita described. >
Linux doesn't operate in the manner Nivedita describes ... the tcp layer on the server side moves to the syn_recd state, but doesn't accept the ack back from client. Instead it times out and sends its syn/ack back to the client and again ignores the client's ack, ... Eventually, either there's room on backlog queue and the server side moves to the established state or the server side stops resending the its syn/ack. This doesn't seem to make much sense. If the tcp layer can send the syn/ack it seems like it should probably respond to the client's ack.
> >The keywords are "syn flood attack" and "DoS". >
I'd be interested in a more specific reference detailing the changes required to the listen syscall as a consequence of the changes required for avoidance of syn flood attacks. Thanks.
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