Use arp to grab container ip instead of dig (it seems to be more reliable)

References: #31

example/Vagrantfile

@@ -24,7 +24,6 @@ Vagrant.configure("2") do |config|
   config.vm.synced_folder cache_dir, "/var/cache/apt/archives"
 
   config.vm.provider :lxc do |lxc|
-    lxc.lxc_dhcp_ip = '10.0.254.1' if ENV['USER'] == 'vagrant'
     lxc.start_opts << 'lxc.cgroup.memory.limit_in_bytes=400M'
     lxc.start_opts << 'lxc.cgroup.memory.memsw.limit_in_bytes=500M'
   end

lib/vagrant-lxc/config.rb

@@ -6,15 +6,8 @@ module Vagrant
       # @return [Array]
       attr_reader :start_opts
 
-      # The ip set for the built in LXC dhcp server (defaults to configured ip
-      # at /etc/default/lxc or 10.0.3.1)
-      #
-      # @return [String]
-      attr_accessor :lxc_dhcp_ip
-
       def initialize
         @start_opts  = []
-        @lxc_dhcp_ip = '10.0.3.1'
       end
     end
   end

lib/vagrant-lxc/container.rb

@@ -9,6 +9,9 @@ require "vagrant-lxc/errors"
 module Vagrant
   module LXC
     class Container
+      # Root folder where containers are stored
+      CONTAINERS_PATH = '/var/lib/lxc'
+
       # Include this so we can use `Subprocess` more easily.
       include Vagrant::Util::Retryable
 
@@ -16,8 +19,6 @@ module Vagrant
       # a name.
       class NotFound < StandardError; end
 
-      CONTAINERS_PATH = '/var/lib/lxc'
-
       attr_reader :name
 
       def initialize(name)
@@ -29,6 +30,14 @@ module Vagrant
         raise NotFound if @name && ! lxc(:ls).split("\n").include?(@name)
       end
 
+      def base_path
+        Pathname.new("#{CONTAINERS_PATH}/#{@name}")
+      end
+
+      def rootfs_path
+        Pathname.new("#{base_path}/rootfs")
+      end
+
       def create(metadata = {})
         # FIXME: Ruby 1.8 users dont have SecureRandom
         @logger.debug('Creating container using lxc-create...')
@@ -52,10 +61,6 @@ module Vagrant
         @name
       end
 
-      def rootfs_path
-        Pathname.new("#{CONTAINERS_PATH}/#{@name}/rootfs")
-      end
-
       def share_folders(folders, config)
         folders.each do |folder|
           guestpath = rootfs_path.join(folder[:guestpath].gsub(/^\//, ''))
@@ -109,15 +114,18 @@ module Vagrant
         end
       end
 
-      def dhcp_ip(server_ip)
+      def assigned_ip
+        unless File.read(base_path.join('config')) =~ /^lxc\.network\.hwaddr\s*=\s*([a-z0-9:]+)\s*$/
+          raise 'Unknown Container MAC Address'
+        end
+        mac_addr = $1
+
+        #`ip neigh flush all > /dev/null`
+
         ip = ''
-        # Right after creation lxc reports the container as running
-        # before DNS is returning the right IP, so have to wait for a while
+        # See: http://programminglinuxblog.blogspot.com.br/2007/11/detecting-ip-address-from-mac-address.html
         retryable(:on => LXC::Errors::ExecuteError, :tries => 10, :sleep => 3) do
-          # By default LXC supplies a dns server on 10.0.3.1 so we request the IP
-          # of our target from there.
-          # Tks to: https://github.com/neerolyte/vagueant/blob/master/bin/vagueant#L340
-          r = (raw 'dig', @name, "@#{server_ip}", '+short')
+          r = (raw 'arp', '-n')
 
           # If the command was a failure then raise an exception that is nicely
           # handled by Vagrant.
@@ -125,14 +133,15 @@ module Vagrant
             if @interrupted
               @logger.info("Exit code != 0, but interrupted. Ignoring.")
             else
-              raise LXC::Errors::ExecuteError, :command => ['dig', @name, "@#{server_ip}", '+short'].inspect
+              raise LXC::Errors::ExecuteError, :command => ['arp', '-n'].inspect
             end
           end
 
-          ip = r.stdout.gsub("\r\n", "\n").strip
-          if ip.empty?
+
+          unless r.stdout.gsub("\r\n", "\n").strip =~ /^([0-9.]+).+#{Regexp.escape mac_addr}/
             raise LXC::Errors::ExecuteError, 'Unable to identify container ip'
           end
+          ip = $1.to_s
 
           # Sometimes lxc reports the container as running before DNS is returning
           # the right IP, so have to try a couple of times sometimes.

lib/vagrant-lxc/provider.rb

@@ -52,7 +52,7 @@ module Vagrant
         return nil if state == :not_created
 
         {
-          :host => @container.dhcp_ip(@machine.provider_config.lxc_dhcp_ip),
+          :host => @container.assigned_ip,
           :port => 22 # @driver.ssh_port(@machine.config.ssh.guest_port)
         }
       end

spec/fixtures/sample-arp-output

@@ -0,0 +1,4 @@
+Address                  HWtype  HWaddress           Flags Mask            Iface
+120.0.3.30               ether   10:16:3e:c8:f9:b7   C                     lxcbr0
+10.0.3.30                ether   00:16:3e:64:d6:74   C                     lxcbr0
+192.168.25.1             ether   2c:e4:12:95:90:45   C                     wlan0

spec/fixtures/sample-config

@@ -0,0 +1,47 @@
+lxc.network.type=veth
+lxc.network.link=lxcbr0
+lxc.network.flags=up
+lxc.network.hwaddr = 00:16:3e:64:d6:74
+lxc.rootfs = /var/lib/lxc/a91df47bfc6e/rootfs
+lxc.utsname = a91df47bfc6e
+
+lxc.devttydir = lxc
+lxc.tty = 4
+lxc.pts = 1024
+lxc.mount  = /var/lib/lxc/a91df47bfc6e/fstab
+lxc.arch = amd64
+lxc.cap.drop = sys_module mac_admin mac_override
+lxc.pivotdir = lxc_putold
+
+# uncomment the next line to run the container unconfined:
+#lxc.aa_profile = unconfined
+
+lxc.cgroup.devices.deny = a
+# Allow any mknod (but not using the node)
+lxc.cgroup.devices.allow = c *:* m
+lxc.cgroup.devices.allow = b *:* m
+# /dev/null and zero
+lxc.cgroup.devices.allow = c 1:3 rwm
+lxc.cgroup.devices.allow = c 1:5 rwm
+# consoles
+lxc.cgroup.devices.allow = c 5:1 rwm
+lxc.cgroup.devices.allow = c 5:0 rwm
+#lxc.cgroup.devices.allow = c 4:0 rwm
+#lxc.cgroup.devices.allow = c 4:1 rwm
+# /dev/{,u}random
+lxc.cgroup.devices.allow = c 1:9 rwm
+lxc.cgroup.devices.allow = c 1:8 rwm
+lxc.cgroup.devices.allow = c 136:* rwm
+lxc.cgroup.devices.allow = c 5:2 rwm
+# rtc
+lxc.cgroup.devices.allow = c 254:0 rwm
+#fuse
+lxc.cgroup.devices.allow = c 10:229 rwm
+#tun
+lxc.cgroup.devices.allow = c 10:200 rwm
+#full
+lxc.cgroup.devices.allow = c 1:7 rwm
+#hpet
+lxc.cgroup.devices.allow = c 10:228 rwm
+#kvm
+lxc.cgroup.devices.allow = c 10:232 rwm

spec/unit/container_spec.rb

@@ -4,7 +4,6 @@ require "vendored_vagrant"
 require 'vagrant-lxc/container'
 
 describe Vagrant::LXC::Container do
-  # Default subject and container name for specs
   let(:name) { nil }
   subject { described_class.new(name) }
 
@@ -181,20 +180,23 @@ describe Vagrant::LXC::Container do
     end
   end
 
-  describe 'dhcp ip' do
-    let(:name)      { 'random-container-name' }
-    let(:ip)        { "10.0.4.123" }
-    let(:server_ip) { "10.0.4.1" }
+  describe 'assigned ip' do
+    # This ip is set on the sample-arp-output based on mac address from sample-config
+    let(:ip)                 { "10.0.3.30" }
+    let(:conf_file_contents) { File.read('spec/fixtures/sample-config') }
+    let(:name)               { 'random-container-name' }
 
     before do
+      @arp_output = File.read('spec/fixtures/sample-arp-output')
       subject.stub(:raw) {
-        mock(stdout: "#{ip}\n", exit_code: 0)
+        mock(stdout: "#{@arp_output}\n", exit_code: 0)
       }
+      File.stub(read: conf_file_contents)
     end
 
-    it 'digs the container ip from lxc dns server' do
-      subject.dhcp_ip(server_ip).should == ip
-      subject.should have_received(:raw).with('dig', name, "@#{server_ip}", '+short')
+    it 'gets parsed from `arp` based on lxc mac address' do
+      subject.assigned_ip.should == ip
+      subject.should have_received(:raw).with('arp', '-n')
     end
   end
 end