guests/arch: Configure networks in one command

This commit updates the procedure for configuring arch networks to occur
in a single command. Previously, each network was configured
independently. If, for some reason, one of the networks destroyed the
SSH connection, the box would be irrecoverable. This commit does not
alleviate that behavior, but attempts to mitigate it by running all
network-related configuration commands in a single communicator (SSH)
session.

The new procedure looks like this:

1. Upload a temp file to /tmp/vagrant-network-id... for each interface
  on the guest.
2. Compile a commands array (of bash) to execute after all network
  configurations have been uploaded.
3. Concatenate all the commands together in a single communicator
  session.

This was tested against `terrywant/archlinux` using the following Vagrantfile:

```ruby
Vagrant.configure(2) do |config|
  config.vm.box = "terrywang/archlinux"
  config.vm.hostname = "banana-ramama.example.com"

  config.vm.network "private_network", type: "dhcp"

  config.vm.network "private_network", ip: "33.33.33.10"

  config.vm.provision "file", source: "Vagrantfile", destination: "/tmp/vf"
  config.vm.provision "shell", inline: "echo hi"
end
```

plugins/guests/arch/cap/configure_networks.rb

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 require "tempfile"
 
 require_relative "../../../../lib/vagrant/util/template_renderer"
@@ -10,32 +9,45 @@ module VagrantPlugins
         include Vagrant::Util
 
         def self.configure_networks(machine, networks)
-          tempfiles  = []
+          comm = machine.communicate
+
+          commands   = []
           interfaces = []
 
-          machine.communicate.sudo("ip -o -0 addr | grep -v LOOPBACK | awk '{print $2}' | sed 's/://'") do |_, result|
-            interfaces = result.split("\n")
+          # The result will be something like:
+          #   eth0\nenp0s8\nenp0s9
+          comm.sudo("ip -o -0 addr | grep -v LOOPBACK | awk '{print $2}' | sed 's/://'") do |_, stdout|
+            interfaces = stdout.split("\n")
           end
 
           networks.each.with_index do |network, i|
             network[:device] = interfaces[network[:interface]]
 
             entry = TemplateRenderer.render("guests/arch/network_#{network[:type]}",
-              options: network)
+              options: network,
+            )
 
-            remote_path = "/tmp/vagrant-network-#{Time.now.to_i}-#{i}"
+            remote_path = "/tmp/vagrant-network-#{network[:device]}-#{Time.now.to_i}-#{i}"
 
             Tempfile.open("vagrant-arch-configure-networks") do |f|
               f.binmode
               f.write(entry)
               f.fsync
               f.close
-              machine.communicate.upload(f.path, remote_path)
+              comm.upload(f.path, remote_path)
             end
 
-            machine.communicate.sudo("mv #{remote_path} /etc/netctl/#{network[:device]}")
-            machine.communicate.sudo("ip link set #{network[:device]} down && netctl restart #{network[:device]} && netctl enable #{network[:device]}")
+            commands << <<-EOH.gsub(/^ {14}/, '')
+              # Configure #{network[:device]}
+              mv '#{remote_path}' '/etc/netctl/#{network[:device]}'
+              ip link set '#{network[:device]}' down
+              netctl restart '#{network[:device]}'
+              netctl enable '#{network[:device]}'
+            EOH
           end
+
+          # Run all the network modification commands in one communicator call.
+          comm.sudo(commands.join("\n"))
         end
       end
     end

test/unit/plugins/guests/arch/cap/configure_networks_test.rb

@@ -9,16 +9,16 @@ describe "VagrantPlugins::GuestArch::Cap::ConfigureNetworks" do
   end
 
   let(:machine) { double("machine") }
-  let(:communicator) { VagrantTests::DummyCommunicator::Communicator.new(machine) }
+  let(:comm) { VagrantTests::DummyCommunicator::Communicator.new(machine) }
 
   before do
-    allow(machine).to receive(:communicate).and_return(communicator)
-    communicator.stub_command("ip -o -0 addr | grep -v LOOPBACK | awk '{print $2}' | sed 's/://'",
+    allow(machine).to receive(:communicate).and_return(comm)
+    comm.stub_command("ip -o -0 addr | grep -v LOOPBACK | awk '{print $2}' | sed 's/://'",
       stdout: "eth1\neth2")
   end
 
   after do
-    communicator.verify_expectations!
+    comm.verify_expectations!
   end
 
   describe ".configure_networks" do
@@ -40,9 +40,16 @@ describe "VagrantPlugins::GuestArch::Cap::ConfigureNetworks" do
     end
 
     it "creates and starts the networks" do
-      communicator.expect_command("ip link set eth1 down && netctl restart eth1 && netctl enable eth1")
-      communicator.expect_command("ip link set eth2 down && netctl restart eth2 && netctl enable eth2")
       described_class.configure_networks(machine, [network_1, network_2])
+      expect(comm.received_commands[1]).to match(/mv (.+) '\/etc\/netctl\/eth1'/)
+      expect(comm.received_commands[1]).to match(/ip link set 'eth1' down/)
+      expect(comm.received_commands[1]).to match(/netctl restart 'eth1'/)
+      expect(comm.received_commands[1]).to match(/netctl enable 'eth1'/)
+
+      expect(comm.received_commands[1]).to match(/mv (.+) '\/etc\/netctl\/eth2'/)
+      expect(comm.received_commands[1]).to match(/ip link set 'eth2' down/)
+      expect(comm.received_commands[1]).to match(/netctl restart 'eth2'/)
+      expect(comm.received_commands[1]).to match(/netctl enable 'eth2'/)
     end
   end
 end

test/unit/plugins/guests/coreos/cap/docker_test.rb

@@ -0,0 +1,28 @@
+require_relative "../../../../base"
+
+describe "VagrantPlugins::GuestCoreOS::Cap::ChangeHostName" do
+  let(:described_class) do
+    VagrantPlugins::GuestCoreOS::Plugin
+      .components
+      .guest_capabilities[:coreos]
+      .get(:docker_daemon_running)
+  end
+
+  let(:machine) { double("machine") }
+  let(:comm) { VagrantTests::DummyCommunicator::Communicator.new(machine) }
+
+  before do
+    allow(machine).to receive(:communicate).and_return(comm)
+  end
+
+  after do
+    comm.verify_expectations!
+  end
+
+  describe ".docker_daemon_running" do
+    it "checks /run/docker/sock" do
+      described_class.docker_daemon_running(machine)
+      expect(comm.received_commands[0]).to eq("test -S /run/docker.sock")
+    end
+  end
+end