Re: Removing T/TCP and replacing it with something simpler

From: Mike Silbersack (silby_at_silby.com)
Date: 10/21/04

  • Next message: Andre Oppermann: "Re: Removing T/TCP and replacing it with something simpler" 
    Date: Thu, 21 Oct 2004 10:24:08 -0500 (CDT)
To: Andre Oppermann <andre@freebsd.org>

    On Thu, 21 Oct 2004, Andre Oppermann wrote:

    > I want to bring this up for discussion prior to start working on it.
    >
    > I intend to remove T/TCP (transactional TCP) support from our TCP
    > implementation for the following reasons:

    That sounds good.

    > o The client has to enable the option in the TCP SYN request to the server.
    > If the server accepts it, then it returns a unique cookie generated from
    > the IP address of the client and some random seed. On subsequent
    > connections
    > the client will include the cookie in the TCP SYN request and it will
    > send the first chunk of payload in the SYN packet. If the cookie matches

    I think that it would have to be slightly more complex than that for it to
    be secure. Instead of using syncookie/RFC1948-like generation, just
    randomly generate the cookie and store it in the tcp host cache. Then
    steal the concept of NQNFS leases, giving the cookie a limited lifetime,
    after which it must be reissued. I think you'll need to track two cookies
    on the server side, to gracefully handle the cookie transition period...

    Well, I'm sure there are many ways to do it, but I agree that it's
    certainly doable; we have plenty of time to talk about the exact
    implementation. My reason for avoiding the use of syncookies/RFC1948 in
    the implementation is that relying on those pieces of code makes a FreeBSD
    implementation easy, but would make an implementation in other OSes
    potentially difficult.

    > FUD Notice:
    >
    > If you haven't read and/or unstood the link above or TCP/IP Illustrated
    > Volume 3 then please refrain from participating in this discussion!

    Hey, I just looked in section 24.7 in Vol. 1, and it says nothing but good
    things about T/TCP - you must be the one misunderstanding things here! :)

    Mike "Silby" Silbersack
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