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/linux/bundle.go

@@ -20,6 +20,7 @@ package linux
 
 import (
 	"context"
+	"crypto/sha256"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -103,7 +104,7 @@ func ShimLocal(c *Config, exchange *exchange.Exchange) ShimOpt {
 // ShimConnect is a ShimOpt for connecting to an existing remote shim
 func ShimConnect(c *Config, onClose func()) ShimOpt {
 	return func(b *bundle, ns string, ropts *runctypes.RuncOptions) (shim.Config, client.Opt) {
-		return b.shimConfig(ns, c, ropts), client.WithConnect(b.shimAddress(ns), onClose)
+		return b.shimConfig(ns, c, ropts), client.WithConnect(b.decideShimAddress(ns), onClose)
 	}
 }
 
@@ -127,10 +128,32 @@ func (b *bundle) Delete() error {
 	return errors.Wrapf(err, "Failed to remove both bundle and workdir locations: %v", err2)
 }
 
-func (b *bundle) shimAddress(namespace string) string {
+func (b *bundle) legacyShimAddress(namespace string) string {
 	return filepath.Join(string(filepath.Separator), "containerd-shim", namespace, b.id, "shim.sock")
 }
 
+func (b *bundle) shimAddress(namespace string) string {
+	d := sha256.Sum256([]byte(filepath.Join(namespace, b.id)))
+	return filepath.Join(string(filepath.Separator), "containerd-shim", fmt.Sprintf("%x.sock", d))
+}
+
+func (b *bundle) loadAddress() (string, error) {
+	addressPath := filepath.Join(b.path, "address")
+	data, err := ioutil.ReadFile(addressPath)
+	if err != nil {
+		return "", err
+	}
+	return string(data), nil
+}
+
+func (b *bundle) decideShimAddress(namespace string) string {
+	address, err := b.loadAddress()
+	if err != nil {
+		return b.legacyShimAddress(namespace)
+	}
+	return address
+}
+
 func (b *bundle) shimConfig(namespace string, c *Config, runcOptions *runctypes.RuncOptions) shim.Config {
 	var (
 		criuPath      string