From owner-freebsd-net@FreeBSD.ORG Wed Jan 1 20:03:06 2014 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 7D28584F for ; Wed, 1 Jan 2014 20:03:06 +0000 (UTC) Received: from h2.funkthat.com (gate2.funkthat.com [208.87.223.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 401461120 for ; Wed, 1 Jan 2014 20:03:05 +0000 (UTC) Received: from h2.funkthat.com (localhost [127.0.0.1]) by h2.funkthat.com (8.14.3/8.14.3) with ESMTP id s01K342n002845 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 1 Jan 2014 12:03:05 -0800 (PST) (envelope-from jmg@h2.funkthat.com) Received: (from jmg@localhost) by h2.funkthat.com (8.14.3/8.14.3/Submit) id s01K347f002844; Wed, 1 Jan 2014 12:03:04 -0800 (PST) (envelope-from jmg) Date: Wed, 1 Jan 2014 12:03:04 -0800 From: John-Mark Gurney To: Peter Jeremy Subject: Re: IPv4 Multicast MAC Address issues Message-ID: <20140101200303.GS99167@funkthat.com> Mail-Followup-To: Peter Jeremy , freebsd-net@freebsd.org References: <20140101085721.GA34334@server.rulingia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140101085721.GA34334@server.rulingia.com> User-Agent: Mutt/1.4.2.3i X-Operating-System: FreeBSD 7.2-RELEASE i386 X-PGP-Fingerprint: 54BA 873B 6515 3F10 9E88 9322 9CB1 8F74 6D3F A396 X-Files: The truth is out there X-URL: http://resnet.uoregon.edu/~gurney_j/ X-Resume: http://resnet.uoregon.edu/~gurney_j/resume.html X-to-the-FBI-CIA-and-NSA: HI! HOW YA DOIN? can i haz chizburger? X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.2 (h2.funkthat.com [127.0.0.1]); Wed, 01 Jan 2014 12:03:05 -0800 (PST) Cc: freebsd-net@freebsd.org X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 01 Jan 2014 20:03:06 -0000 Peter Jeremy wrote this message on Wed, Jan 01, 2014 at 19:57 +1100: > I'm trying to use multicast on my home network for the first time and > have found an apparent anomoly in the destination MAC address. > > My reading of RFC1112 section 6.4 is that the the destination MAC > address uses the low 23 bits of the destination (multicast) IP > address. This is what Linux and Windows do and ifmcstat(8) on > FreeBSD shows that as the multicast MAC filter. Unfortunately, it > seems that (at least on FreeBSD-10), the destination MAC address > uses the low 23 bits of the IP address of my default route. > > I am not doing any special multicast-related configuration on any > of the hosts and have been using ping(8) to generate multicast > packets. > > Does FreeBSD need special configuration to support multicast or is this > a bug? This is probably a bug, and I have confirmed this on: FreeBSD carbon.funkthat.com 11.0-CURRENT FreeBSD 11.0-CURRENT #4 r256870:258399M: Wed Nov 20 12:33:22 PST 2013 jmg@carbon.funkthat.com:/usr/src/sys/amd64/compile/lockprof amd64 [jmg@carbon ~]$ echo foobar | nc -u 239.100.100.100 3845 sldkfjsdlfkj # tcpdump -i re0 -n -e port 3845 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on re0, link-type EN10MB (Ethernet), capture size 65535 bytes capability mode sandbox enabled 11:59:03.998008 xx:xx:xx:xx:xx:xx > 01:00:5e:28:00:0e, ethertype IPv4 (0x0800), length 49: 192.168.0.21.15921 > 239.100.100.100.3845: UDP, length 7 -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."