Add shim start for shim creation

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

runtime/v2/shim/util.go

@@ -0,0 +1,141 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package shim
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/containerd/containerd/namespaces"
+	"github.com/pkg/errors"
+)
+
+const shimBinaryFormat = "containerd-shim-%s-%s"
+
+// Command returns the shim command with the provided args and configuration
+func Command(ctx context.Context, runtime, containerdAddress, path string, cmdArgs ...string) (*exec.Cmd, error) {
+	ns, err := namespaces.NamespaceRequired(ctx)
+	if err != nil {
+		return nil, err
+	}
+	self, err := os.Executable()
+	if err != nil {
+		return nil, err
+	}
+	args := []string{
+		"-namespace", ns,
+		"-address", containerdAddress,
+		"-publish-binary", self,
+	}
+	args = append(args, cmdArgs...)
+	name := BinaryName(runtime)
+	if _, err := exec.LookPath(name); err != nil {
+		if eerr, ok := err.(*exec.Error); ok {
+			if eerr.Err == exec.ErrNotFound {
+				return nil, errors.Wrapf(os.ErrNotExist, "runtime %q binary not installed %q", runtime, name)
+			}
+		}
+	}
+	cmd := exec.Command(name, args...)
+	cmd.Dir = path
+	cmd.Env = append(os.Environ(), "GOMAXPROCS=2")
+	cmd.SysProcAttr = getSysProcAttr()
+	return cmd, nil
+}
+
+// BinaryName returns the shim binary name from the runtime name
+func BinaryName(runtime string) string {
+	parts := strings.Split(runtime, ".")
+	// TODO: add validation for runtime
+	return fmt.Sprintf(shimBinaryFormat, parts[len(parts)-2], parts[len(parts)-1])
+}
+
+// AbstractAddress returns an abstract socket address
+func AbstractAddress(ctx context.Context, id string) (string, error) {
+	ns, err := namespaces.NamespaceRequired(ctx)
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(string(filepath.Separator), "containerd-shim", ns, id, "shim.sock"), nil
+}
+
+// Connect to the provided address
+func Connect(address string, d func(string, time.Duration) (net.Conn, error)) (net.Conn, error) {
+	return d(address, 100*time.Second)
+}
+
+// AnonDialer returns a dialer for an abstract socket
+func AnonDialer(address string, timeout time.Duration) (net.Conn, error) {
+	address = strings.TrimPrefix(address, "unix://")
+	return net.DialTimeout("unix", "\x00"+address, timeout)
+}
+
+// NewSocket returns a new socket
+func NewSocket(address string) (*net.UnixListener, error) {
+	if len(address) > 106 {
+		return nil, errors.Errorf("%q: unix socket path too long (> 106)", address)
+	}
+	l, err := net.Listen("unix", "\x00"+address)
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to listen to abstract unix socket %q", address)
+	}
+	return l.(*net.UnixListener), nil
+}
+
+// WritePidFile writes a pid file atomically
+func WritePidFile(path string, pid int) error {
+	path, err := filepath.Abs(path)
+	if err != nil {
+		return err
+	}
+	tempPath := filepath.Join(filepath.Dir(path), fmt.Sprintf(".%s", filepath.Base(path)))
+	f, err := os.OpenFile(tempPath, os.O_RDWR|os.O_CREATE|os.O_EXCL|os.O_SYNC, 0666)
+	if err != nil {
+		return err
+	}
+	_, err = fmt.Fprintf(f, "%d", pid)
+	f.Close()
+	if err != nil {
+		return err
+	}
+	return os.Rename(tempPath, path)
+}
+
+// WriteAddress writes a address file atomically
+func WriteAddress(path, address string) error {
+	path, err := filepath.Abs(path)
+	if err != nil {
+		return err
+	}
+	tempPath := filepath.Join(filepath.Dir(path), fmt.Sprintf(".%s", filepath.Base(path)))
+	f, err := os.OpenFile(tempPath, os.O_RDWR|os.O_CREATE|os.O_EXCL|os.O_SYNC, 0666)
+	if err != nil {
+		return err
+	}
+	_, err = f.WriteString(address)
+	f.Close()
+	if err != nil {
+		return err
+	}
+	return os.Rename(tempPath, path)
+}