From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlad Yasevich Subject: Re: How does the linux kernel select the MAC address for TAP devices? Date: Mon, 16 Jun 2014 09:39:29 -0400 Message-ID: <539EF391.2040100@gmail.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit To: Albert Krenz , netdev@vger.kernel.org Return-path: Received: from mail-qa0-f45.google.com ([209.85.216.45]:48422 "EHLO mail-qa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750775AbaFPNjd (ORCPT ); Mon, 16 Jun 2014 09:39:33 -0400 Received: by mail-qa0-f45.google.com with SMTP id v10so7264217qac.4 for ; Mon, 16 Jun 2014 06:39:32 -0700 (PDT) In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On 06/16/2014 04:00 AM, Albert Krenz wrote: > As stated in the email subject: Where does the kernel get the used > MAC-Adress for a newly create TAP device? Are they randomly generated > or does it select one from a fixed pool of reserved MAC-Adresses? > > I have not found any official documentation about the selection of > MAC-addresses for TAP-devices. Most sites like > http://backreference.org/2010/03/26/tuntap-interface-tutorial/ state > that the MAC addresses are auto-generated and can be changed. But they > do not explain the generation rules. > > Does anyone know an official document (preferably from kernel.org) > explaining the MAC selection process? Or is it only explained in the > Source? Yes, it is explained in the source. In particular look at the function tun_net_init(). The default MAC is random. -vlad