Windows [TP4] localhost mitigation

Signed-off-by: John Howard <jhoward@microsoft.com>

opts/opts.go

@@ -14,9 +14,6 @@ import (
 var (
 	alphaRegexp  = regexp.MustCompile(`[a-zA-Z]`)
 	domainRegexp = regexp.MustCompile(`^(:?(:?[a-zA-Z0-9]|(:?[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9]))(:?\.(:?[a-zA-Z0-9]|(:?[a-zA-Z0-9][a-zA-Z0-9\-]*[a-zA-Z0-9])))*)\.?\s*$`)
-	// DefaultHTTPHost Default HTTP Host used if only port is provided to -H flag e.g. docker daemon -H tcp://:8080
-	DefaultHTTPHost = "localhost"
-
 	// DefaultHTTPPort Default HTTP Port used if only the protocol is provided to -H flag e.g. docker daemon -H tcp://
 	// TODO Windows. DefaultHTTPPort is only used on Windows if a -H parameter
 	// is not supplied. A better longer term solution would be to use a named

opts/opts_unix.go

@@ -0,0 +1,6 @@
+// +build !windows
+
+package opts
+
+// DefaultHTTPHost Default HTTP Host used if only port is provided to -H flag e.g. docker daemon -H tcp://:8080
+const DefaultHTTPHost = "localhost"

opts/opts_windows.go

@@ -0,0 +1,56 @@
+package opts
+
+// TODO Windows. Identify bug in GOLang 1.5.1 and/or Windows Server 2016 TP4.
+// @jhowardmsft, @swernli.
+//
+// On Windows, this mitigates a problem with the default options of running
+// a docker client against a local docker daemon on TP4.
+//
+// What was found that if the default host is "localhost", even if the client
+// (and daemon as this is local) is not physically on a network, and the DNS
+// cache is flushed (ipconfig /flushdns), then the client will pause for
+// exactly one second when connecting to the daemon for calls. For example
+// using docker run windowsservercore cmd, the CLI will send a create followed
+// by an attach. You see the delay between the attach finishing and the attach
+// being seen by the daemon.
+//
+// Here's some daemon debug logs with additional debug spew put in. The
+// AfterWriteJSON log is the very last thing the daemon does as part of the
+// create call. The POST /attach is the second CLI call. Notice the second
+// time gap.
+//
+// time="2015-11-06T13:38:37.259627400-08:00" level=debug msg="After createRootfs"
+// time="2015-11-06T13:38:37.263626300-08:00" level=debug msg="After setHostConfig"
+// time="2015-11-06T13:38:37.267631200-08:00" level=debug msg="before createContainerPl...."
+// time="2015-11-06T13:38:37.271629500-08:00" level=debug msg=toDiskLocking....
+// time="2015-11-06T13:38:37.275643200-08:00" level=debug msg="loggin event...."
+// time="2015-11-06T13:38:37.277627600-08:00" level=debug msg="logged event...."
+// time="2015-11-06T13:38:37.279631800-08:00" level=debug msg="In defer func"
+// time="2015-11-06T13:38:37.282628100-08:00" level=debug msg="After daemon.create"
+// time="2015-11-06T13:38:37.286651700-08:00" level=debug msg="return 2"
+// time="2015-11-06T13:38:37.289629500-08:00" level=debug msg="Returned from daemon.ContainerCreate"
+// time="2015-11-06T13:38:37.311629100-08:00" level=debug msg="After WriteJSON"
+// ... 1 second gap here....
+// time="2015-11-06T13:38:38.317866200-08:00" level=debug msg="Calling POST /v1.22/containers/984758282b842f779e805664b2c95d563adc9a979c8a3973e68c807843ee4757/attach"
+// time="2015-11-06T13:38:38.326882500-08:00" level=info msg="POST /v1.22/containers/984758282b842f779e805664b2c95d563adc9a979c8a3973e68c807843ee4757/attach?stderr=1&stdin=1&stdout=1&stream=1"
+//
+// We suspect this is either a bug introduced in GOLang 1.5.1, or that a change
+// in GOLang 1.5.1 (from 1.4.3) is exposing a bug in Windows TP4. In theory,
+// the Windows networking stack is supposed to resolve "localhost" internally,
+// without hitting DNS, or even reading the hosts file (which is why localhost
+// is commented out in the hosts file on Windows).
+//
+// We have validated that working around this using the actual IPv4 localhost
+// address does not cause the delay.
+//
+// This does not occur with the docker client built with 1.4.3 on the same
+// Windows TP4 build, regardless of whether the daemon is built using 1.5.1
+// or 1.4.3. It does not occur on Linux. We also verified we see the same thing
+// on a cross-compiled Windows binary (from Linux).
+//
+// Final note: This is a mitigation, not a 'real' fix. It is still susceptible
+// to the delay in TP4 if a user were to do 'docker run -H=tcp://localhost:2375...'
+// explicitly.
+
+// DefaultHTTPHost Default HTTP Host used if only port is provided to -H flag e.g. docker daemon -H tcp://:8080
+const DefaultHTTPHost = "127.0.0.1"