Inspect networks before creating new ones

This commit updates the behavior of how the docker provider creates new
docker networks. It looks at each existing network to see if the
requested subnet has already been configured in the docker engine. If
so, Vagrant will use that network rather than creating a new one. This
includes networks not created by Vagrant. Vagrant will not clean up
these networks if created outside of Vagrant.

plugins/providers/docker/action/destroy_network.rb

@@ -27,6 +27,7 @@ module VagrantPlugins
               network_name = "vagrant_network"
             end
 
+            # Only cleans up networks defined by Vagrant
             if machine.provider.driver.existing_network?(network_name) &&
                 !machine.provider.driver.network_used?(network_name)
               env[:ui].info(I18n.t("docker_provider.network_destroy", network_name: network_name))

plugins/providers/docker/action/network.rb

@@ -7,6 +7,7 @@ module VagrantPlugins
         def initialize(app, env)
           @app = app
           @logger = Log4r::Logger.new('vagrant::plugins::docker::network')
+          @@lock = Mutex.new
         end
 
         # @param[Hash] options - options from the network config
@@ -64,7 +65,15 @@ module VagrantPlugins
             cli_opts = generate_create_cli_arguments(options)
 
             if options[:subnet]
+              existing_network = machine.provider.driver.subnet_defined?(options[:subnet])
+              if !existing_network
                 network_name = "vagrant_network_#{options[:subnet]}"
+              else
+                env[:ui].warn(I18n.t("docker_provider.subnet_exists",
+                                     network_name: existing_network,
+                                     subnet: options[:subnet]))
+                network_name = existing_network
+              end
             elsif options[:type] == "dhcp"
               network_name = "vagrant_network"
             else
@@ -72,12 +81,16 @@ module VagrantPlugins
             end
             container_id = machine.id
 
+            @@lock.synchronize do
+              machine.env.lock("docker-network-create", retry: true) do
                 if !machine.provider.driver.existing_network?(network_name)
                   @logger.debug("Creating network #{network_name}")
                   machine.provider.driver.create_network(network_name, cli_opts)
                 else
                   @logger.debug("Network #{network_name} already created")
                 end
+              end
+            end
 
             @logger.debug("Connecting network #{network_name} to container guest #{machine.name}")
             connect_opts = generate_connect_cli_arguments(options)

plugins/providers/docker/driver.rb

@@ -205,7 +205,8 @@ module VagrantPlugins
       # @param [Array]  networks - list of networks to inspect
       # @param [Array]  opts - An array of flags used for listing networks
       def inspect_network(network, opts=nil)
-        command = ['docker', 'network', 'inspect', network].push(*opts)
+        command = ['docker', 'network', 'inspect'] + Array(network)
+        command = command.push(*opts)
         output = execute(*command)
         output
       end
@@ -246,13 +247,35 @@ module VagrantPlugins
       # Docker network helpers
       # ######################
 
+      # @param [String] subnet_string - Subnet to look for
+      def subnet_defined?(subnet_string)
+        all_networks = list_network(["--format={{.Name}}"])
+        all_networks = all_networks.split("\n")
+
+        results = inspect_network(all_networks)
+        begin
+          networks_info = JSON.parse(results)
+          networks_info.each do |network|
+            config = network["IPAM"]["Config"]
+            if (config.size > 0 &&
+                config.first["Subnet"] == subnet_string)
+              @logger.debug("Found existing network #{network["Name"]} already configured with #{subnet_string}")
+              return network["Name"]
+            end
+          end
+        rescue JSON::ParserError => e
+          @logger.warn("Could not properly parse response from `docker network inspect #{all_networks.join(" ")}`")
+        end
+        return nil
+      end
+
       # Looks to see if a docker network has already been defined
       #
       # @param [String] network - name of network to look for
       def existing_network?(network)
-        result = list_network(["--format='{{json .Name}}'"])
+        result = list_network(["--format={{.Name}}"])
         #TODO: we should be more explicit here if we can
-        result.match?(/\"#{network}\"/)
+        result.match?(/#{network}/)
       end
 
       # Returns true or false if network is in use or not.

templates/locales/providers_docker.yml

@@ -70,6 +70,9 @@ en:
     ssh_through_host_vm: |-
       SSH will be proxied through the Docker virtual machine since we're
       not running Docker natively. This is just a notice, and not an error.
+    subnet_exists: |-
+      A network called '%{network_name}' using subnet '%{subnet}' is already in use.
+      Using '%{network_name}' instead of creating a new network...
     synced_folders_changed: |-
       Vagrant has noticed that the synced folder definitions have changed.
       With Docker, these synced folder changes won't take effect until you

test/unit/plugins/providers/docker/action/network_test.rb

@@ -61,6 +61,7 @@ describe VagrantPlugins::DockerProvider::Action::Network do
       allow(driver).to receive(:existing_network?).and_return(false)
       allow(driver).to receive(:create_network).and_return(true)
       allow(driver).to receive(:connect_network).and_return(true)
+      allow(driver).to receive(:subnet_defined?).and_return(nil)
 
       called = false
       app = ->(*args) { called = true }
@@ -76,6 +77,8 @@ describe VagrantPlugins::DockerProvider::Action::Network do
       allow(driver).to receive(:existing_network?).and_return(false)
       allow(driver).to receive(:create_network).and_return(true)
       allow(driver).to receive(:connect_network).and_return(true)
+      allow(driver).to receive(:subnet_defined?).and_return(nil)
+
 
       expect(subject).to receive(:generate_create_cli_arguments).
         with(networks[0][1]).and_return(["--subnet=172.20.0.0/16", "--driver=bridge", "--internal=true"])
@@ -86,6 +89,21 @@ describe VagrantPlugins::DockerProvider::Action::Network do
       expect(subject).to receive(:generate_connect_cli_arguments).
         with(networks[1][1]).and_return([])
 
+      expect(driver).to receive(:create_network).twice
+      expect(driver).to receive(:connect_network).twice
+
+      subject.call(env)
+    end
+
+    it "uses an existing network if a matching subnet is found" do
+      allow(driver).to receive(:host_vm?).and_return(false)
+      allow(driver).to receive(:existing_network?).and_return(true)
+      allow(driver).to receive(:create_network).and_return(true)
+      allow(driver).to receive(:connect_network).and_return(true)
+      allow(driver).to receive(:subnet_defined?).and_return("my_cool_subnet_network")
+
+      expect(driver).not_to receive(:create_network)
+
       subject.call(env)
     end