synced_folders/rsync: SSH control for faster rsync

plugins/synced_folders/rsync/command/rsync_auto.rb

@@ -185,7 +185,10 @@ def callback(paths, modified, added, removed)
 
               ssh_info = opts[:machine].ssh_info
               begin
+                start = Time.now
                 RsyncHelper.rsync_single(opts[:machine], ssh_info, opts[:opts])
+                finish = Time.now
+                @logger.info("Time spent in rsync: #{finish-start} (in seconds)")
               rescue Vagrant::Errors::MachineGuestNotReady
                 # Error communicating to the machine, probably a reload or
                 # halt is happening. Just notify the user but don't fail out.

plugins/synced_folders/rsync/helper.rb

@@ -66,9 +66,17 @@ def self.rsync_single(machine, ssh_info, opts)
           proxy_command = "-o ProxyCommand='#{ssh_info[:proxy_command]}' "
         end
 
+        # Create the path for the control sockets. We used to do this
+        # in the machine data dir but this can result in paths that are
+        # too long for unix domain sockets.
+        controlpath = File.join(Dir.tmpdir, "ssh.#{rand(1000)}")
+
         rsh = [
           "ssh -p #{ssh_info[:port]} " +
           proxy_command +
+          "-o ControlMaster=auto " +
+          "-o ControlPath=#{controlpath} " +
+          "-o ControlPersist=10m " +
           "-o StrictHostKeyChecking=no " +
           "-o IdentitiesOnly=true " +
           "-o UserKnownHostsFile=/dev/null",