Send SSH keep-alive packets [GH-516]

CHANGELOG.md

@@ -45,6 +45,8 @@ IMPROVEMENTS:
   - Detect PuTTY Link SSH client on Windows and show an error. [GH-1518]
   - `vagrant ssh` in Cygwin won't output DOS path file warnings.
   - Add `--rtcuseutc on` as a sane default for VirtualBox. [GH-912]
+  - SSH will send keep-alive packets every 5 seconds by default to
+    keep connections alive. Can be disabled with `config.ssh.keep_alive`. [GH-516]
 
 BUG FIXES:
 

config/default.rb

@@ -3,6 +3,7 @@ Vagrant.configure("2") do |config|
 
   config.ssh.username = "vagrant"
   config.ssh.guest_port = 22
+  config.ssh.keep_alive = true
   config.ssh.max_tries = 100
   config.ssh.timeout = 30
   config.ssh.forward_agent = false

plugins/communicators/ssh/communicator.rb

@@ -295,8 +295,28 @@ module VagrantPlugins
           end
         end
 
-        # Wait for the channel to complete
-        channel.wait
+        begin
+          keep_alive = nil
+
+          if @machine.config.ssh.keep_alive
+            # Begin sending keep-alive packets while we wait for the script
+            # to complete. This avoids connections closing on long-running
+            # scripts.
+            keep_alive = Thread.new do
+              loop do
+                sleep 5
+                @logger.debug("Sending SSH keep-alive...")
+                connection.send_global_request("keep-alive@openssh.com")
+              end
+            end
+          end
+
+          # Wait for the channel to complete
+          channel.wait
+        ensure
+          # Kill the keep-alive thread
+          keep_alive.kill if keep_alive
+        end
 
         # Return the final exit status
         return exit_status

plugins/kernel_v2/config/ssh.rb

@@ -7,6 +7,7 @@ module VagrantPlugins
       attr_accessor :forward_x11
       attr_accessor :guest_port
       attr_accessor :host
+      attr_accessor :keep_alive
       attr_accessor :max_tries
       attr_accessor :port
       attr_accessor :private_key_path
@@ -19,6 +20,7 @@ module VagrantPlugins
         @forward_x11      = UNSET_VALUE
         @guest_port       = UNSET_VALUE
         @host             = UNSET_VALUE
+        @keep_alive       = UNSET_VALUE
         @max_tries        = UNSET_VALUE
         @port             = UNSET_VALUE
         @private_key_path = UNSET_VALUE
@@ -32,6 +34,7 @@ module VagrantPlugins
         @forward_x11      = false if @forward_x11 == UNSET_VALUE
         @guest_port       = nil if @guest_port == UNSET_VALUE
         @host             = nil if @host == UNSET_VALUE
+        @keep_alive       = false if @keep_alive == UNSET_VALUE
         @max_tries        = nil if @max_tries == UNSET_VALUE
         @port             = nil if @port == UNSET_VALUE
         @private_key_path = nil if @private_key_path == UNSET_VALUE