Retry SSH on EHOSTUNREACH

This is one of those errors that happens once in awhile that can be
retried.

CHANGELOG.md

@@ -42,6 +42,8 @@
     "localhost" is not available. [GH-1057]
   - Sending a SIGINT (Ctrl-C) very early on when executing `vagrant` no
     longer results in an ugly stack trace.
+  - SSH retries in the face of a `EHOSTUNREACH` error, improving the robustness
+    that SSHing succeeds when booting a machine.
 
 ## 1.0.3 (May 1, 2012)
 

plugins/communicators/ssh/communicator.rb

@@ -151,7 +151,16 @@ module VagrantPlugins
         # Connect to SSH, giving it a few tries
         connection = nil
         begin
-          exceptions = [Errno::ECONNREFUSED, Net::SSH::Disconnect, Timeout::Error]
+          # These are the exceptions that we retry because they represent
+          # errors that are generally fixed from a retry and don't
+          # necessarily represent immediate failure cases.
+          exceptions = [
+            Errno::ECONNREFUSED,
+            Errno::EHOSTUNREACH,
+            Net::SSH::Disconnect,
+            Timeout::Error
+          ]
+
           connection = retryable(:tries => @machine.config.ssh.max_tries, :on => exceptions) do
             Timeout.timeout(@machine.config.ssh.timeout) do
               @logger.info("Attempting to connect to SSH: #{ssh_info[:host]}:#{ssh_info[:port]}")