From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx1-b.sourceforge.net ([10.3.1.91] helo=mail.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1EZeuZ-0005bb-Sw for user-mode-linux-devel@lists.sourceforge.net; Tue, 08 Nov 2005 17:38:03 -0800 Received: from smtp007.mail.ukl.yahoo.com ([217.12.11.96]) by mail.sourceforge.net with smtp (Exim 4.44) id 1EZeuY-0005Nf-Dq for user-mode-linux-devel@lists.sourceforge.net; Tue, 08 Nov 2005 17:38:04 -0800 From: Blaisorblade Subject: Re: [uml-devel] Test for ethernet broadcast address? References: <200511081913.14657.rob@landley.net> In-Reply-To: <200511081913.14657.rob@landley.net> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200511090244.52916.blaisorblade@yahoo.it> Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Wed, 9 Nov 2005 02:44:52 +0100 To: user-mode-linux-devel@lists.sourceforge.net Cc: Rob Landley On Wednesday 09 November 2005 02:13, Rob Landley wrote: > So I'm trying to play with ifenslave under UML, and my naieve attempt to go > > ./linux LD_ASSUME_KERNEL=2.4.1 eth0=daemon,11:11:11:11:11:11 \ > eth1=daemon,22:22:22:22:22:22 rootfstype=hostfs rw init=/bin/sh > > Led to unexpected results that eth0 had a mac addr of 00:00:00:00:00:00. > Eventually, I tracked it down to this test in arch/um/drivers/net_kern.c: > if(addr[0] & 1){ > printk(KERN_ERR > "Attempt to assign a broadcast ethernet address to a " > "device disallowed\n"); > return(0); > } > > My question is: where's the spec for what is and isn't a broadcast address? Don't know what Jeff means, but he and UML consistently says "first byte odd <-> broadcast". That's even coded above. Don't ask me what exaclty he means. ^H^H^H^H Ouch, I have the vice to understand things. So I went to the RFC, I spent enough time on them, and I understood they're not the Ethernet specification (the real spec is the DIX one, and later IEEE ones). They're way too short! But quoting from your link to ethereal's wiki: "A destination MAC address of ff:ff:ff:ff:ff:ff indicates a Broadcast, meaning the packet is sent from one host to any other on that network. <<<<<<<<<<<<<<<<<<<<< A destination MAC address where the low-order bit of the first byte is set <<<<<<<<<<<<<<<<<<<<< indicats a Multicast, meaning the packet is sent from one host to all hosts on the network interested in packets sent to that MAC address. A number of multicast addresses have been assigned; see Ethernet numbers at the IANA, Michael A. Patton's list of multicast addresses, and Ethereal's list of Ethernet vendor codes and well-known MAC addresses, from the Ethereal source distribution, for assigned multicast addresses." So. UML is not exact technically, but it's enough for our purposes. Don't know whether it may make sense to assign a multicast address to an iface, but I guess it's more complicate. Anyway, complete references and patches (or indications about what to code) are always welcome. -- Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!". Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894) http://www.user-mode-linux.org/~blaisorblade ___________________________________ Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB http://mail.yahoo.it ------------------------------------------------------- SF.Net email is sponsored by: Tame your development challenges with Apache's Geronimo App Server. Download it for free - -and be entered to win a 42" plasma tv or your very own Sony(tm)PSP. Click here to play: http://sourceforge.net/geronimo.php _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel