A patch to support predictable network interface names like enp0s25 on Ubuntu 16.04 with Vagrant 1.8.1

vagrant-1.8.1-xenial.patch

diff -ruN vagrant-1.8.1.orig/plugins/guests/debian/cap/configure_networks.rb vagrant-1.8.1/plugins/guests/debian/cap/configure_networks.rb
--- vagrant-1.8.1.orig/plugins/guests/debian/cap/configure_networks.rb	2015-12-25 06:30:19.000000000 +0900
+++ vagrant-1.8.1/plugins/guests/debian/cap/configure_networks.rb	2016-04-24 03:22:08.000000000 +0900
@@ -1,3 +1,4 @@
+require 'log4r'
 require 'set'
 require 'tempfile'
 
@@ -9,8 +10,22 @@
       class ConfigureNetworks
         include Vagrant::Util
 
+        @logger = Log4r::Logger.new("vagrant::plugins::guest")
+
         def self.configure_networks(machine, networks)
           machine.communicate.tap do |comm|
+            main_interface = ''
+            comm.execute(%q!ip route | awk '$1=="default"{print $NF;exit}'!) do |type, data|
+              main_interface = data.chomp if type == :stdout
+            end
+            @logger.debug("debian configure_networks. main_interface=#{main_interface.inspect}")
+            available_interfaces = []
+            comm.execute("ls /sys/class/net | grep -v -E '^(lo$|docker|lx[cd])|veth'") do |type, data|
+              available_interfaces = data.chomp.split("\n") if type == :stdout
+            end
+            available_interfaces.delete(main_interface)
+            @logger.debug("debian configure_networks. available_interfaces=#{available_interfaces.inspect}")
+
             # First, remove any previous network modifications
             # from the interface file.
             comm.sudo("sed -e '/^#VAGRANT-BEGIN/,$ d' /etc/network/interfaces > /tmp/vagrant-network-interfaces.pre")
@@ -21,11 +36,15 @@
             # later.
             interfaces = Set.new
             entries = []
-            networks.each do |network|
-              interfaces.add(network[:interface])
+            networks.each_with_index do |network, i|
+              interface = available_interfaces[i]
+              interfaces.add(interface)
+              network[:interface] = interface
               entry = TemplateRenderer.render("guests/debian/network_#{network[:type]}",
-                                              options: network)
+                                              options: network,
+                                              main_interface: main_interface)
 
+              @logger.debug("debian configure_networks. updated entry \##{i}:\n#{entry}")
               entries << entry
             end
 
@@ -37,22 +56,25 @@
             temp.close
 
             comm.upload(temp.path, "/tmp/vagrant-network-entry")
+            @logger.debug("debian configure_networks. uploaded /tmp/vagrant-network-entry")
 
             # Bring down all the interfaces we're reconfiguring. By bringing down
-            # each specifically, we avoid reconfiguring eth0 (the NAT interface) so
+            # each specifically, we avoid reconfiguring main_interface (ex. eth0) (the NAT interface) so
             # SSH never dies.
             interfaces.each do |interface|
-              comm.sudo("/sbin/ifdown eth#{interface} 2> /dev/null")
-              comm.sudo("/sbin/ip addr flush dev eth#{interface} 2> /dev/null")
+              comm.sudo("if [ `/bin/cat /sys/class/net/#{interface}/operstate` = up ]; then /sbin/ifdown #{interface} 2> /dev/null; fi")
+              comm.sudo("/sbin/ip addr flush dev #{interface} 2> /dev/null")
             end
+            @logger.debug("debian configure_networks. brought down all the network interfaces.")
 
             comm.sudo('cat /tmp/vagrant-network-interfaces.pre /tmp/vagrant-network-entry /tmp/vagrant-network-interfaces.post > /etc/network/interfaces')
             comm.sudo('rm -f /tmp/vagrant-network-interfaces.pre /tmp/vagrant-network-entry /tmp/vagrant-network-interfaces.post')
 
             # Bring back up each network interface, reconfigured
             interfaces.each do |interface|
-              comm.sudo("/sbin/ifup eth#{interface}")
+              comm.sudo("/sbin/ifup #{interface}")
             end
+            @logger.debug("debian configure_networks. brought back up all the network interfaces.")
           end
         end
       end
diff -ruN vagrant-1.8.1.orig/plugins/guests/ubuntu/cap/change_host_name.rb vagrant-1.8.1/plugins/guests/ubuntu/cap/change_host_name.rb
--- vagrant-1.8.1.orig/plugins/guests/ubuntu/cap/change_host_name.rb	2015-12-25 06:30:19.000000000 +0900
+++ vagrant-1.8.1/plugins/guests/ubuntu/cap/change_host_name.rb	2016-04-24 03:21:13.000000000 +0900
@@ -6,6 +6,23 @@
           super
         end
 
+        def initialize(machine, new_hostname)
+          super
+          @logger = Log4r::Logger.new("vagrant::plugins::guest")
+        end
+
+        def get_current_hostname
+          return super unless systemd?
+
+          hostname = ""
+          sudo "hostnamectl --static status" do |type, data|
+            hostname = data.chomp if type == :stdout && hostname.empty?
+          end
+          @logger.debug("ubuntu get_current_hostname got hostname=#{hostname} by hostnamectl.")
+
+          hostname
+        end
+
         def update_etc_hostname
           return super unless systemd?
           sudo("hostnamectl set-hostname '#{short_hostname}'")
diff -ruN vagrant-1.8.1.orig/templates/guests/debian/network_dhcp.erb vagrant-1.8.1/templates/guests/debian/network_dhcp.erb
--- vagrant-1.8.1.orig/templates/guests/debian/network_dhcp.erb	2015-12-25 06:30:19.000000000 +0900
+++ vagrant-1.8.1/templates/guests/debian/network_dhcp.erb	2016-04-23 22:46:12.000000000 +0900
@@ -1,13 +1,13 @@
 #VAGRANT-BEGIN
 # The contents below are automatically generated by Vagrant. Do not modify.
-auto eth<%= options[:interface] %>
-iface eth<%= options[:interface] %> inet dhcp
+auto <%= options[:interface] %>
+iface <%= options[:interface] %> inet dhcp
 <% if !options[:use_dhcp_assigned_default_route] %>
     post-up route del default dev $IFACE || true
 <% else %>
     # We need to disable eth0, see GH-2648
-    post-up route del default dev eth0 || true
+    post-up route del default dev <%= main_interface %> || true
     post-up dhclient $IFACE
-    pre-down route add default dev eth0
+    pre-down route add default dev <%= main_interface %>
 <% end %>
 #VAGRANT-END
diff -ruN vagrant-1.8.1.orig/templates/guests/debian/network_static.erb vagrant-1.8.1/templates/guests/debian/network_static.erb
--- vagrant-1.8.1.orig/templates/guests/debian/network_static.erb	2015-12-25 06:30:19.000000000 +0900
+++ vagrant-1.8.1/templates/guests/debian/network_static.erb	2016-04-23 22:45:46.000000000 +0900
@@ -1,7 +1,7 @@
 #VAGRANT-BEGIN
 # The contents below are automatically generated by Vagrant. Do not modify.
-auto eth<%= options[:interface] %>
-iface eth<%= options[:interface] %> inet static
+auto <%= options[:interface] %>
+iface <%= options[:interface] %> inet static
       address <%= options[:ip] %>
       netmask <%= options[:netmask] %>
 <% if options[:gateway] %>
diff -ruN vagrant-1.8.1.orig/templates/guests/debian/network_static6.erb vagrant-1.8.1/templates/guests/debian/network_static6.erb
--- vagrant-1.8.1.orig/templates/guests/debian/network_static6.erb	2015-12-25 06:30:19.000000000 +0900
+++ vagrant-1.8.1/templates/guests/debian/network_static6.erb	2016-04-23 22:45:37.000000000 +0900
@@ -1,7 +1,7 @@
 #VAGRANT-BEGIN
 # The contents below are automatically generated by Vagrant. Do not modify.
-auto eth<%= options[:interface] %>
-iface eth<%= options[:interface] %> inet6 static
+auto <%= options[:interface] %>
+iface <%= options[:interface] %> inet6 static
       address <%= options[:ip] %>
       netmask <%= options[:netmask] %>
 <% if options[:gateway] %>

For a patch to vagrant master, please refer to
hashicorp/vagrant#7253

How to apply this patch:

cd  /opt/vagrant/embedded/gems/gems/vagrant-1.8.1
sudo patch -p1 < ${path_to_this_patch_file}

I updated this patch to ignore network interfaces whose name matches the regex ^lxd and ^veth too.
See hashicorp/vagrant#7253 (comment)