Add container attach support.

Signed-off-by: Lantao Liu <lantaol@google.com>

pkg/server/helpers.go

@@ -19,12 +19,10 @@ package server
 import (
 	"encoding/json"
 	"fmt"
-	"io"
 	"os"
 	"path/filepath"
 	"strconv"
 	"strings"
-	"syscall"
 
 	"github.com/containerd/containerd/content"
 	"github.com/containerd/containerd/errdefs"
@@ -157,37 +155,6 @@ func getSandboxDevShm(sandboxRootDir string) string {
 	return filepath.Join(sandboxRootDir, "shm")
 }
 
-// prepareStreamingPipes prepares stream named pipe for container. returns nil
-// streaming handler if corresponding stream path is empty.
-func (c *criContainerdService) prepareStreamingPipes(ctx context.Context, stdin, stdout, stderr string) (
-	i io.WriteCloser, o io.ReadCloser, e io.ReadCloser, retErr error) {
-	pipes := map[string]io.ReadWriteCloser{}
-	for t, stream := range map[string]struct {
-		path string
-		flag int
-	}{
-		"stdin":  {stdin, syscall.O_WRONLY | syscall.O_CREAT | syscall.O_NONBLOCK},
-		"stdout": {stdout, syscall.O_RDONLY | syscall.O_CREAT | syscall.O_NONBLOCK},
-		"stderr": {stderr, syscall.O_RDONLY | syscall.O_CREAT | syscall.O_NONBLOCK},
-	} {
-		if stream.path == "" {
-			continue
-		}
-		s, err := c.os.OpenFifo(ctx, stream.path, stream.flag, 0700)
-		if err != nil {
-			return nil, nil, nil, fmt.Errorf("failed to open named pipe %q: %v",
-				stream.path, err)
-		}
-		defer func(cl io.Closer) {
-			if retErr != nil {
-				cl.Close()
-			}
-		}(s)
-		pipes[t] = s
-	}
-	return pipes["stdin"], pipes["stdout"], pipes["stderr"], nil
-}
-
 // getNetworkNamespace returns the network namespace of a process.
 func getNetworkNamespace(pid uint32) string {
 	return fmt.Sprintf(netNSFormat, pid)