generate random mac address for xen or qemu

random_mac.py

#!/usr/bin/env python

import sys
import random

# this function is directly from xend/server/netif.py and is thus
# available under the LGPL,
# Copyright 2004, 2005 Mike Wray <mike.wray@hp.com>
# Copyright 2005 XenSource Ltd
def randomMAC(type="xen"):
    """Generate a random MAC address.

    00-16-3E allocated to xensource
    52-54-00 used by qemu/kvm

    The OUI list is available at http://standards.ieee.org/regauth/oui/oui.txt.

    The remaining 3 fields are random, with the first bit of the first
    random field set 0.

    >>> randomMAC().startswith("00:16:3E")
    True
    >>> randomMAC("foobar").startswith("00:16:3E")
    True
    >>> randomMAC("xen").startswith("00:16:3E")
    True
    >>> randomMAC("qemu").startswith("52:54:00")
    True

    @return: MAC address string
    """
    ouis = { 'xen': [ 0x00, 0x16, 0x3E ], 'qemu': [ 0x52, 0x54, 0x00 ] }

    try:
        oui = ouis[type]
    except KeyError:
        oui = ouis['xen']

    mac = oui + [
            random.randint(0x00, 0xff),
            random.randint(0x00, 0xff),
            random.randint(0x00, 0xff)]
    return ':'.join(map(lambda x: "%02x" % x, mac))

if __name__ == "__main__":
    print randomMAC("xen" if len(sys.argv) < 2 else sys.argv[1])