Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 2 Jul 2002 02:45:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 2 Jul 2002 02:45:35 -0400 Received: from mail.zmailer.org ([62.240.94.4]:31945 "EHLO mail.zmailer.org") by vger.kernel.org with ESMTP id ; Tue, 2 Jul 2002 02:45:35 -0400 Date: Tue, 2 Jul 2002 09:48:02 +0300 From: Matti Aarnio To: Dax Kelson Cc: linux-kernel@vger.kernel.org Subject: Re: Is ff:00:00:00:00:00 a broadcast frame? Message-ID: <20020702094802.Y28720@mea-ext.zmailer.org> References: <1025566031.5129.179.camel@porthos> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1025566031.5129.179.camel@porthos>; from dax@GuruLabs.com on Mon, Jul 01, 2002 at 05:27:11PM -0600 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3051 Lines: 76 On Mon, Jul 01, 2002 at 05:27:11PM -0600, Dax Kelson wrote: > In the "earlier" 2.4 kernels (those that shipped/errata with RHL 7.1 > ~2.4.6), an ethernet frame destined to ff:00:00:00:00:00 were not > processed and passed up the stack. > > Now, with "current" 2.4 kernels (RHL 7.2 errata, and RHL 7.3 > 2.4.9-2.4.18), the same frame IS processed and passed up the stack. That IEEE 802 MAC address is NOT a broadcast address. Broadcast would be one with all bits set: ff:ff:ff:ff:ff:ff The above mentioned MAC address is a multicast frame, because bit 0x01 in the first octet is set. (All broadcast-frames are also multicast.) > The hardware is identical, the NICs are 3c905C. > > Is this an intentional optimization/bug? > > Here is an ARP request encapsulated in a "bogus" ethernet frame (look at > the layer 2 destination). A RHL 7.3 (2.4.18) system will respond (see > Frame 2 below) to this frame, an older RHL 7.1 (2.4.6) system will not > respond. Neither should respond. IPv4 ARP is defined using only broadcast frames. > Frame 1 (42 on wire, 42 captured) > Arrival Time: Jul 1, 2002 17:16:35.565996000 > Time delta from previous packet: 1.009672000 seconds > Time relative to first packet: 1.009833000 seconds > Frame Number: 3 > Packet Length: 42 bytes > Capture Length: 42 bytes > Ethernet II > Destination: ff:00:00:00:00:00 (ff:00:00:00:00:00) > Source: ff:00:00:00:00:00 (ff:00:00:00:00:00) > Type: ARP (0x0806) > Address Resolution Protocol (request) > Hardware type: Ethernet (0x0001) > Protocol type: IP (0x0800) > Hardware size: 6 > Protocol size: 4 > Opcode: request (0x0001) > Sender MAC address: 00:01:03:de:56:a4 (00:01:03:de:56:a4) > Sender IP address: 10.100.0.8 (10.100.0.8) > Target MAC address: 00:00:00:00:00:00 (00:00:00:00:00:00) > Target IP address: 10.100.0.10 (10.100.0.10) > > Frame 2 (60 on wire, 60 captured) > Arrival Time: Jul 1, 2002 17:16:35.566146000 > Time delta from previous packet: 0.000150000 seconds > Time relative to first packet: 1.009983000 seconds > Frame Number: 4 > Packet Length: 60 bytes > Capture Length: 60 bytes > Ethernet II > Destination: 00:01:03:de:56:a4 (00:01:03:de:56:a4) > Source: 00:01:03:de:57:37 (00:01:03:de:57:37) > Type: ARP (0x0806) > Trailer: 00000000000000000000000000000000... > Address Resolution Protocol (reply) > Hardware type: Ethernet (0x0001) > Protocol type: IP (0x0800) > Hardware size: 6 > Protocol size: 4 > Opcode: reply (0x0002) > Sender MAC address: 00:01:03:de:57:37 (00:01:03:de:57:37) > Sender IP address: 10.100.0.10 (10.100.0.10) > Target MAC address: 00:01:03:de:56:a4 (00:01:03:de:56:a4) > Target IP address: 10.100.0.8 (10.100.0.8) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/