Set HTTP upgrade headers when hijacking connection

Signed-off-by: Jean-Tiare Le Bigot <jt@yadutaf.fr>

api/client/hijack.go

@@ -135,6 +135,8 @@ func (cli *DockerCli) hijack(method, path string, setRawTerminal bool, in io.Rea
 	}
 	req.Header.Set("User-Agent", "Docker-Client/"+dockerversion.VERSION)
 	req.Header.Set("Content-Type", "plain/text")
+	req.Header.Set("Connection", "Upgrade")
+	req.Header.Set("Upgrade", "tcp")
 	req.Host = cli.addr
 
 	dial, err := cli.dial()

api/server/server.go

@@ -887,7 +887,7 @@ func postContainersAttach(eng *engine.Engine, version version.Version, w http.Re
 
 	var errStream io.Writer
 
-	fmt.Fprintf(outStream, "HTTP/1.1 200 OK\r\nContent-Type: application/vnd.docker.raw-stream\r\n\r\n")
+	fmt.Fprintf(outStream, "HTTP/1.1 101 UPGRADED\r\nContent-Type: application/vnd.docker.raw-stream\r\nConnection: Upgrade\r\nUpgrade: tcp\r\n\r\n")
 
 	if c.GetSubEnv("Config") != nil && !c.GetSubEnv("Config").GetBool("Tty") && version.GreaterThanOrEqualTo("1.6") {
 		errStream = stdcopy.NewStdWriter(outStream, stdcopy.Stderr)
@@ -1137,7 +1137,7 @@ func postContainerExecStart(eng *engine.Engine, version version.Version, w http.
 
 		var errStream io.Writer
 
-		fmt.Fprintf(outStream, "HTTP/1.1 200 OK\r\nContent-Type: application/vnd.docker.raw-stream\r\n\r\n")
+		fmt.Fprintf(outStream, "HTTP/1.1 101 UPGRADED\r\nContent-Type: application/vnd.docker.raw-stream\r\nConnection: Upgrade\r\nUpgrade: tcp\r\n\r\n")
 		if !job.GetenvBool("Tty") && version.GreaterThanOrEqualTo("1.6") {
 			errStream = stdcopy.NewStdWriter(outStream, stdcopy.Stderr)
 			outStream = stdcopy.NewStdWriter(outStream, stdcopy.Stdout)