Date: Tue, 7 May 2002 00:10:09 -0500 (CDT) From: Mike Silbersack <silby@silby.com> To: Garrett Wollman <wollman@khavrinen.lcs.mit.edu> Cc: net@freebsd.org Subject: Re: Junior network hacker tasks... Message-ID: <20020507000816.L62342-100000@patrocles.silby.com> In-Reply-To: <200205062253.g46MrWiY071722@khavrinen.lcs.mit.edu>
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On Mon, 6 May 2002, Garrett Wollman wrote: > <<On Mon, 6 May 2002 17:26:20 -0500 (CDT), Mike Silbersack <silby@silby.com> said: > > > Is doing this wise? I have this nagging feeling that randomizing (or > > zeroing on each new connection) the timestamp would degrade its usefulness > > for PAWS checks and the like. (Don't ask me how, I haven't thought it > > through fully.) > > I don't think so, because the timestamps, as currently specified, are > only meaningful within the context of a single connection. See > sections 1.2, 4.3, and 4.2 of RFC 1323. The PAWS mechanism requires > only that timestamps used by each connection be monotone increasing > with respect to Sequence Number Arithmetic. RFC 1323 does require > (section 4.2.2) that the clock be between 1 ms and 1 s in period, > which I think we already violate on some platforms, although not > seriously; there probably should be a pre-computed (global) scaling > factor as well. > > -GAWollman I looked over both our and Linux's tcp stack to double-check, and it appears that my memory was faulty. You are correct, no PAWS checks are done during TIME_WAIT recycling. Initializing to zero is probably the best idea; getting fancy with random starts doesn't really help anything. Mike "Silby" Silbersack To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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