horten the unix socket path for shim

Use sha256 hash to shorten the unix socket path to satisfy the
length limitation of abstract socket path

This commit also backports the feature storing address path to
a file from v2 to keep compatibility

Fixes #3032

Signed-off-by: Eric Lin <linxiulei@gmail.com>

runtime/v1/shim/client/client.go

@@ -20,10 +20,12 @@ package client
 
 import (
 	"context"
+	"fmt"
 	"io"
 	"net"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"strings"
 	"sync"
 	"syscall"
@@ -107,6 +109,10 @@ func WithStart(binary, address, daemonAddress, cgroup string, debug bool, exitHa
 			"address": address,
 			"debug":   debug,
 		}).Infof("shim %s started", binary)
+
+		if err := writeAddress(filepath.Join(config.Path, "address"), address); err != nil {
+			return nil, nil, err
+		}
 		// set shim in cgroup if it is provided
 		if cgroup != "" {
 			if err := setCgroup(cgroup, cmd); err != nil {
@@ -166,6 +172,25 @@ func newCommand(binary, daemonAddress string, debug bool, config shim.Config, so
 	return cmd, nil
 }
 
+// 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)
+}
+
 func newSocket(address string) (*net.UnixListener, error) {
 	if len(address) > 106 {
 		return nil, errors.Errorf("%q: unix socket path too long (> 106)", address)