core: exec with the proxy command if specified

lib/vagrant/machine.rb

@@ -281,7 +281,7 @@ module Vagrant
       info[:forward_agent] = @config.ssh.forward_agent
       info[:forward_x11]   = @config.ssh.forward_x11
 
-      # add in provided proxy command config
+      # Add in provided proxy command config
       info[:proxy_command] = @config.ssh.proxy_command if @config.ssh.proxy_command
 
       # Set the private key path. If a specific private key is given in

lib/vagrant/util/ssh.rb

@@ -122,6 +122,10 @@ module Vagrant
             "-o", "ForwardX11Trusted=yes"]
         end
 
+        if ssh_info[:proxy_command]
+          command_options += ["-o", "ProxyCommand=#{ssh_info[:proxy_command]}"]
+        end
+
         # Configurables -- extra_args should always be last due to the way the
         # ssh args parser works. e.g. if the user wants to use the -t option,
         # any shell command(s) she'd like to run on the remote server would

plugins/communicators/ssh/communicator.rb

@@ -209,7 +209,10 @@ module VagrantPlugins
                   :logger  => ssh_logger,
                   :verbose => :debug
                 })
-                connect_opts[:proxy] = Net::SSH::Proxy::Command.new(ssh_info[:proxy_command]) if ssh_info[:proxy_command]
+
+                if ssh_info[:proxy_command]
+                  connect_opts[:proxy] = Net::SSH::Proxy::Command.new(ssh_info[:proxy_command])
+                end
 
                 @logger.info("Attempting to connect to SSH...")
                 @logger.info("  - Host: #{ssh_info[:host]}")

plugins/kernel_v2/config/ssh.rb

@@ -21,6 +21,7 @@ module VagrantPlugins
         @forward_x11   = UNSET_VALUE
         @guest_port    = UNSET_VALUE
         @keep_alive    = UNSET_VALUE
+        @proxy_command = UNSET_VALUE
         @shell         = UNSET_VALUE
 
         @default    = SSHConnectConfig.new
@@ -40,6 +41,7 @@ module VagrantPlugins
         @forward_x11   = false if @forward_x11 == UNSET_VALUE
         @guest_port = nil if @guest_port == UNSET_VALUE
         @keep_alive = false if @keep_alive == UNSET_VALUE
+        @proxy_command = nil if @proxy_command == UNSET_VALUE
         @shell      = nil if @shell == UNSET_VALUE
 
         @default.finalize!