@@ -9,6 +9,7 @@ import (

 	"fmt"

 	"io"

 	"io/ioutil"

+	"net/http"

 	"net/url"

 	"os"

 	"path"

@@ -254,8 +255,21 @@ func calcCopyInfo(b *Builder, cmdName string, cInfos *[]*copyInfo, origPath stri

 		fmt.Fprintf(b.OutStream, "\n")

 		tmpFile.Close()

-		// Remove the mtime of the newly created tmp file

-		if err := system.UtimesNano(tmpFileName, make([]syscall.Timespec, 2)); err != nil {

+		// Set the mtime to the Last-Modified header value if present

+		// Otherwise just remove atime and mtime

+		times := make([]syscall.Timespec, 2)

+

+		lastMod := resp.Header.Get("Last-Modified")

+		if lastMod != "" {

+			mTime, err := http.ParseTime(lastMod)

+			// If we can't parse it then just let it default to 'zero'

+			// otherwise use the parsed time value

+			if err == nil {

+				times[1] = syscall.NsecToTimespec(mTime.UnixNano())

+			}

+		}

+

+		if err := system.UtimesNano(tmpFileName, times); err != nil {

 			return err

 		}

@@ -376,7 +376,11 @@ destination container.

 All new files and directories are created with a UID and GID of 0.

 In the case where `<src>` is a remote file URL, the destination will

-have permissions of 600.

+have permissions of 600. If the remote file being retrieved has an HTTP

+`Last-Modified` header, the timestamp from that header will be used

+to set the `mtime` on the destination file. Then, like any other file

+processed during an `ADD`, `mtime` will be included in the determination

+of whether or not the file has changed and the cache should be updated.

 > **Note**:

 > If you build by passing a `Dockerfile` through STDIN (`docker

@@ -7,9 +7,11 @@ import (

 	"io/ioutil"

 	"os"

 	"os/exec"

+	"path"

 	"path/filepath"

 	"regexp"

 	"strings"

+	"syscall"

 	"testing"

 	"time"

@@ -2214,6 +2216,64 @@ func TestBuildADDRemoteFileWithoutCache(t *testing.T) {

 	logDone("build - add remote file without cache")

 }

+func TestBuildADDRemoteFileMTime(t *testing.T) {

+	name := "testbuildaddremotefilemtime"

+	defer deleteImages(name)

+

+	server, err := fakeStorage(map[string]string{"baz": "hello"})

+	if err != nil {

+		t.Fatal(err)

+	}

+	defer server.Close()

+

+	ctx, err := fakeContext(fmt.Sprintf(`FROM scratch

+        MAINTAINER dockerio

+        ADD %s/baz /usr/lib/baz/quux`, server.URL), nil)

+	if err != nil {

+		t.Fatal(err)

+	}

+	defer ctx.Close()

+

+	id1, err := buildImageFromContext(name, ctx, true)

+	if err != nil {

+		t.Fatal(err)

+	}

+

+	id2, err := buildImageFromContext(name, ctx, true)

+	if err != nil {

+		t.Fatal(err)

+	}

+	if id1 != id2 {

+		t.Fatal("The cache should have been used but wasn't - #1")

+	}

+

+	// Now set baz's times to anything else and redo the build

+	// This time the cache should not be used

+	bazPath := path.Join(server.FakeContext.Dir, "baz")

+	err = syscall.UtimesNano(bazPath, make([]syscall.Timespec, 2))

+	if err != nil {

+		t.Fatalf("Error setting mtime on %q: %v", bazPath, err)

+	}

+

+	id3, err := buildImageFromContext(name, ctx, true)

+	if err != nil {

+		t.Fatal(err)

+	}

+	if id1 == id3 {

+		t.Fatal("The cache should not have been used but was")

+	}

+

+	// And for good measure do it again and make sure cache is used this time

+	id4, err := buildImageFromContext(name, ctx, true)

+	if err != nil {

+		t.Fatal(err)

+	}

+	if id3 != id4 {

+		t.Fatal("The cache should have been used but wasn't - #2")

+	}

+	logDone("build - add remote file testing mtime")

+}

+

 func TestBuildADDLocalAndRemoteFilesWithCache(t *testing.T) {

 	name := "testbuildaddlocalandremotefilewithcache"

 	defer deleteImages(name)