#!/bin/bash
##  rndmac -- Randomize network interface MAC addresses
##
##  Only the second half of the MAC address is randomized.
##  The OUI half is left the same. 

#  Get interface names
if ! echo :$PATH: | grep -q ":/sbin:"; then   # $PATH has /sbin?
  PATH=$PATH:/sbin;
fi
IFs=$(ip -o link show | awk -F':' '{print $2}' )

#  Generate random addresses, set them, and display some output
if sudo service network-manager stop; then
 for nic in $IFs; do
  if test $nic != "lo"; then  # exclude local interface
    macb4=$(cat /sys/class/net/$nic/address)
    randmac=$(openssl rand -hex 1):$(openssl rand -hex 1):$(openssl rand -hex 1)
    fullnewmac=$(cat /sys/class/net/$nic/address | cut -c -9)$randmac
    sudo ifconfig $nic down && \
      sudo ifconfig $nic hw ether $fullnewmac && \
      sudo ifconfig $nic up && \
    macafter=$(cat /sys/class/net/$nic/address)
    #  Output
    echo "$nic"
    echo "Previous MAC:  $macb4"
    echo "Current MAC:   $macafter"
  fi
 done
 sudo service network-manager start
fi