Add code to handle CRI attach

A goroutine is started to forward terminal resize requests
from the resize channel. Also, data is copied back/forth
between stdin, stdout, stderr streams and the attach socket
for the container.

Signed-off-by: Mrunal Patel <mpatel@redhat.com>

server/container_attach.go

@@ -1,11 +1,111 @@
 package server
 
 import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net"
+	"os"
+	"path/filepath"
+	"syscall"
+
+	"github.com/Sirupsen/logrus"
+	"github.com/kubernetes-incubator/cri-o/oci"
 	"golang.org/x/net/context"
 	pb "k8s.io/kubernetes/pkg/kubelet/api/v1alpha1/runtime"
+	kubecontainer "k8s.io/kubernetes/pkg/kubelet/container"
+	"k8s.io/kubernetes/pkg/util/term"
 )
 
 // Attach prepares a streaming endpoint to attach to a running container.
 func (s *Server) Attach(ctx context.Context, req *pb.AttachRequest) (*pb.AttachResponse, error) {
-	return nil, nil
+	logrus.Debugf("AttachRequest %+v", req)
+
+	resp, err := s.GetAttach(req)
+	if err != nil {
+		return nil, fmt.Errorf("unable to prepare attach endpoint")
+	}
+
+	return resp, nil
+}
+
+// Attach endpoint for streaming.Runtime
+func (ss streamService) Attach(containerID string, inputStream io.Reader, outputStream, errorStream io.WriteCloser, tty bool, resize <-chan term.Size) error {
+	c := ss.runtimeServer.GetContainer(containerID)
+
+	if c == nil {
+		return fmt.Errorf("could not find container %q", containerID)
+	}
+
+	if err := ss.runtimeServer.runtime.UpdateStatus(c); err != nil {
+		return err
+	}
+
+	cState := ss.runtimeServer.runtime.ContainerStatus(c)
+	if !(cState.Status == oci.ContainerStateRunning || cState.Status == oci.ContainerStateCreated) {
+		return fmt.Errorf("container is not created or running")
+	}
+
+	controlPath := filepath.Join(c.BundlePath(), "ctl")
+	controlFile, err := os.OpenFile(controlPath, syscall.O_WRONLY, 0)
+	if err != nil {
+		return fmt.Errorf("failed to open container ctl file: %v", err)
+	}
+
+	kubecontainer.HandleResizing(resize, func(size term.Size) {
+		logrus.Infof("Got a resize event: %+v", size)
+		_, err := fmt.Fprintf(controlFile, "%d %d %d\n", 1, size.Height, size.Width)
+		if err != nil {
+			logrus.Infof("Failed to write to control file to resize terminal: %v", err)
+		}
+	})
+
+	attachSocketPath := filepath.Join("/var/run/crio", c.ID(), "attach")
+	conn, err := net.Dial("unix", attachSocketPath)
+	if err != nil {
+		return fmt.Errorf("failed to connect to container %s attach socket: %v", c.ID(), err)
+	}
+	defer conn.Close()
+
+	receiveStdout := make(chan error)
+	if outputStream != nil || errorStream != nil {
+		go func() {
+			receiveStdout <- redirectResponseToOutputStream(tty, outputStream, errorStream, conn)
+		}()
+	}
+
+	stdinDone := make(chan struct{})
+	go func() {
+		if inputStream != nil {
+			io.Copy(conn, inputStream)
+		}
+		close(stdinDone)
+	}()
+
+	select {
+	case err := <-receiveStdout:
+		return err
+	case <-stdinDone:
+		if outputStream != nil || errorStream != nil {
+			return <-receiveStdout
+		}
+	}
+
+	return nil
+}
+
+func redirectResponseToOutputStream(tty bool, outputStream, errorStream io.Writer, conn io.Reader) error {
+	if outputStream == nil {
+		outputStream = ioutil.Discard
+	}
+	if errorStream == nil {
+		// errorStream = ioutil.Discard
+	}
+	var err error
+	if tty {
+		_, err = io.Copy(outputStream, conn)
+	} else {
+		// TODO
+	}
+	return err
 }