communicator/ssh: make TCP keep-alive period shorter [GH-1232]

CHANGELOG.md

@@ -24,6 +24,7 @@ BUG FIXES:
       SSH. [GH-1445]
   * core: Fix crash that could happen with a well timed double Ctrl-C.
       [GH-1328] [GH-1314]
+  * core: SSH TCP keepalive period is now 5 seconds (shorter). [GH-1232]
   * builder/amazon-chroot: Can properly build HVM images now. [GH-1360]
   * builder/amazon-chroot: Fix crash in root device check. [GH-1360]
   * builder/amazon-instance: Fix deprecation warning for `ec2-bundle-vol`

communicator/ssh/connect.go

@@ -17,6 +17,7 @@ func ConnectFunc(network, addr string) func() (net.Conn, error) {
 
 		if tcpConn, ok := c.(*net.TCPConn); ok {
 			tcpConn.SetKeepAlive(true)
+			tcpConn.SetKeepAlivePeriod(5 * time.Second)
 		}
 
 		return c, nil