From owner-freebsd-net Mon Apr 16 7:37:31 2001 Delivered-To: freebsd-net@freebsd.org Received: from homer.softweyr.com (bsdconspiracy.net [208.187.122.220]) by hub.freebsd.org (Postfix) with ESMTP id 248BD37B43F; Mon, 16 Apr 2001 07:37:25 -0700 (PDT) (envelope-from wes@softweyr.com) Received: from [127.0.0.1] (helo=softweyr.com ident=67b8f9b839749317407b58ec008f73e6) by homer.softweyr.com with esmtp (Exim 3.16 #1) id 14pA7d-0000Vq-00; Mon, 16 Apr 2001 08:36:58 -0600 Message-ID: <3ADB0389.5D236D88@softweyr.com> Date: Mon, 16 Apr 2001 08:36:57 -0600 From: Wes Peters Organization: Softweyr LLC X-Mailer: Mozilla 4.75 [en] (X11; U; Linux 2.2.12 i386) X-Accept-Language: en MIME-Version: 1.0 To: Kris Kennaway Cc: freebsd-security@FreeBSD.ORG, net@FreeBSD.org Subject: Re: non-random IP IDs References: <001f01c0c30b$805b0840$d2e2fdce@netrex.com> <20010416020311.A1292@xor.obsecurity.org> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org Kris Kennaway wrote: > > On Thu, Apr 12, 2001 at 12:40:32AM -0500, Mike Silbersack wrote: > > > Each IP packet sent has with it a 16-bit ID. The numbers must remain > > unique over a short period of time so fragmentation can work properly. As > > such, everything except recent openbsds simple increments the id by 1 for > > each packet sent out. > > > > As a result, you can tell the number of packets sent on an idle host by > > seeing the difference in id numbers for the packets it sends back to you. > > It's not really that important of an issue, don't worry about it. > > Here's a patch ported from OpenBSD which randomizes this (supposedly > such that it respects the constraint of not wrapping within the > prescribed time period). I should wrap it in a sysctl, I guess. > > http://www.freebsd.org/~kris/ipid.patch > > Comments? Looks clean. The only comment I can find is: Why not have ip_randomid() return the ID in network byte order? It would save several HTONS macros trailing the ip_randomid() calls. -- "Where am I, and what am I doing in this handbasket?" Wes Peters Softweyr LLC wes@softweyr.com http://softweyr.com/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message