From owner-freebsd-questions@FreeBSD.ORG  Tue Jan  6 22:38:28 2009
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 643EC1065672
	for <freebsd-questions@freebsd.org>;
	Tue,  6 Jan 2009 22:38:28 +0000 (UTC)
	(envelope-from psteele@maxiscale.com)
Received: from arcturus.maxiscale.com (arcturus.maxiscale.com [76.231.178.136])
	by mx1.freebsd.org (Postfix) with ESMTP id 40CD18FC12
	for <freebsd-questions@freebsd.org>;
	Tue,  6 Jan 2009 22:38:27 +0000 (UTC)
	(envelope-from psteele@maxiscale.com)
X-ASG-Debug-ID: 1231281506-0c2500000000-jLrpzn
X-Barracuda-URL: http://10.100.1.25:8000/cgi-bin/mark.cgi
Received: from polaris.maxiscale.com (localhost [127.0.0.1])
	by arcturus.maxiscale.com (Spam Firewall) with ESMTP id 71EDD35E96
	for <freebsd-questions@freebsd.org>;
	Tue,  6 Jan 2009 14:38:26 -0800 (PST)
Received: from polaris.maxiscale.com (polaris.maxiscale.com [10.100.1.24]) by
	arcturus.maxiscale.com with ESMTP id 3k649DxOGaJF4qEc for
	<freebsd-questions@freebsd.org>;
	Tue, 06 Jan 2009 14:38:26 -0800 (PST)
X-ASG-Whitelist: Client
X-MimeOLE: Produced By Microsoft Exchange V6.5
Content-class: urn:content-classes:message
MIME-Version: 1.0
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
X-ASG-Orig-Subj: RE: Do UDP broadcasts work in FreeBSD?
Date: Tue, 6 Jan 2009 14:38:24 -0800
Message-ID: <2ACA3DE8F9758A48B8BE2C7A847F91F2479E56@polaris.maxiscale.com>
In-Reply-To: <2ACA3DE8F9758A48B8BE2C7A847F91F2479E3F@polaris.maxiscale.com>
X-MS-Has-Attach: 
X-MS-TNEF-Correlator: 
Thread-Topic: Do UDP broadcasts work in FreeBSD?
Thread-Index: AclwPgGFrFG1/uUgSByWkr1Zmb9a1QAA+aMQAAK/5aA=
References: <2ACA3DE8F9758A48B8BE2C7A847F91F2479DF3@polaris.maxiscale.com><69A0F543-74D4-4D38-A0A5-A0EDE87A3DBB@mac.com>
	<2ACA3DE8F9758A48B8BE2C7A847F91F2479E3F@polaris.maxiscale.com>
From: "Peter Steele" <psteele@maxiscale.com>
To: <freebsd-questions@freebsd.org>
X-Barracuda-Connect: polaris.maxiscale.com[10.100.1.24]
X-Barracuda-Start-Time: 1231281506
X-Barracuda-Virus-Scanned: by Barracuda Spam Firewall at maxiscale.com
Subject: RE: Do UDP broadcasts work in FreeBSD?
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 06 Jan 2009 22:38:28 -0000

> I've already looked at the ISC DHCP source code. They use raw sockets
to
> send their broadcasts, which seems to us to be a convoluted way of
> sending a simple broadcast. I've seen examples of DHCP client/server
> code written in Java using standard UDP. Unfortunately, our own system
> is already largely implemented in Java/Python, so we'll need to
provide
> a JNI interface to support raw sockets. Alternatively we may patch the
> kernel to fix the bug at its source.

Another option we're considering is to use the firewall to detect
broadcasts and rewrite the MAC addresses in the outgoing packets. In
looking at tcpdump output of broadcasts, the IP address is set to
255.255.255.255 and the MAC address is set to the MAC address of the
gateway. On Linux boxes the MAC address is ff:ff:ff:ff:ff:ff, and that's
the only significant difference in the packet. We thought we might be
able to come up with a firewall rule to detect broadcasts and change the
MAC address to the same as what Linux uses. I'm still in the process of
researching this, but if someone can tell me this is impossible, I'll
move on.