Use netssh builtin keep alive functionality

plugins/communicators/ssh/communicator.rb

@@ -456,6 +456,11 @@ module VagrantPlugins
                   connect_opts[:remote_user] = ssh_info[:remote_user]
                 end
 
+                if @machine.config.ssh.keep_alive
+                  connect_opts[:keepalive] = true
+                  connect_opts[:keepalive_interval] = 5
+                end
+
                 @logger.info("Attempting to connect to SSH...")
                 @logger.info("  - Host: #{ssh_info[:host]}")
                 @logger.info("  - Port: #{ssh_info[:port]}")
@@ -683,21 +688,6 @@ module VagrantPlugins
         end
 
         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
           begin
             channel.wait
@@ -711,9 +701,6 @@ module VagrantPlugins
           rescue Net::SSH::Disconnect
             raise Vagrant::Errors::SSHDisconnected
           end
-        ensure
-          # Kill the keep-alive thread
-          keep_alive.kill if keep_alive
         end
 
         # If we're in a PTY, we now finally parse the output

test/unit/plugins/communicators/ssh/communicator_test.rb

@@ -669,6 +669,32 @@ describe VagrantPlugins::CommunicatorSSH::Communicator do
         ).and_return(true)
         communicator.send(:connect)
       end
+
+      context "keep ssh connection alive" do
+        let(:ssh) do
+          double("ssh",
+            timeout: 1,
+            host: nil,
+            port: 5986,
+            guest_port: 5986,
+            pty: false,
+            keep_alive: true,
+            insert_key: insert_ssh_key,
+            export_command_template: export_command_template,
+            shell: 'bash -l'
+          )
+        end
+
+        it "sets keepalive settings" do
+          expect(Net::SSH).to receive(:start).with(
+            nil, nil, hash_including(
+              keepalive: true,
+              keepalive_interval: 5
+            )
+          ).and_return(true)
+          communicator.send(:connect)
+        end
+      end
     end
 
     context "with keys_only disabled and verify_host_key enabled" do