From owner-freebsd-net Mon May 6 22: 9:23 2002 Delivered-To: freebsd-net@freebsd.org Received: from patrocles.silby.com (d118.as9.nwbl0.wi.voyager.net [169.207.132.246]) by hub.freebsd.org (Postfix) with ESMTP id 0C75337B404 for ; Mon, 6 May 2002 22:09:19 -0700 (PDT) Received: from patrocles.silby.com (localhost [127.0.0.1]) by patrocles.silby.com (8.12.3/8.12.3) with ESMTP id g475AHUm063582; Tue, 7 May 2002 00:10:17 -0500 (CDT) (envelope-from silby@silby.com) Received: from localhost (silby@localhost) by patrocles.silby.com (8.12.3/8.12.3/Submit) with ESMTP id g475AAlF063579; Tue, 7 May 2002 00:10:12 -0500 (CDT) X-Authentication-Warning: patrocles.silby.com: silby owned process doing -bs Date: Tue, 7 May 2002 00:10:09 -0500 (CDT) From: Mike Silbersack To: Garrett Wollman Cc: net@freebsd.org Subject: Re: Junior network hacker tasks... In-Reply-To: <200205062253.g46MrWiY071722@khavrinen.lcs.mit.edu> Message-ID: <20020507000816.L62342-100000@patrocles.silby.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org On Mon, 6 May 2002, Garrett Wollman wrote: > < 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