Move sys to pkg/sys

Signed-off-by: Derek McGowan <derek@mcg.dev>

pkg/sys/socket_unix.go

@@ -0,0 +1,80 @@
+//go:build !windows
+
+/*
+   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 sys
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"path/filepath"
+
+	"golang.org/x/sys/unix"
+)
+
+// CreateUnixSocket creates a unix socket and returns the listener
+func CreateUnixSocket(path string) (net.Listener, error) {
+	// BSDs have a 104 limit
+	if len(path) > 104 {
+		return nil, fmt.Errorf("%q: unix socket path too long (> 104)", path)
+	}
+	if err := os.MkdirAll(filepath.Dir(path), 0660); err != nil {
+		return nil, err
+	}
+	if err := unix.Unlink(path); err != nil && !os.IsNotExist(err) {
+		return nil, err
+	}
+	return net.Listen("unix", path)
+}
+
+// GetLocalListener returns a listener out of a unix socket.
+func GetLocalListener(path string, uid, gid int) (net.Listener, error) {
+	// Ensure parent directory is created
+	if err := mkdirAs(filepath.Dir(path), uid, gid); err != nil {
+		return nil, err
+	}
+
+	l, err := CreateUnixSocket(path)
+	if err != nil {
+		return l, err
+	}
+
+	if err := os.Chmod(path, 0660); err != nil {
+		l.Close()
+		return nil, err
+	}
+
+	if err := os.Chown(path, uid, gid); err != nil {
+		l.Close()
+		return nil, err
+	}
+
+	return l, nil
+}
+
+func mkdirAs(path string, uid, gid int) error {
+	if _, err := os.Stat(path); !os.IsNotExist(err) {
+		return err
+	}
+
+	if err := os.MkdirAll(path, 0770); err != nil {
+		return err
+	}
+
+	return os.Chown(path, uid, gid)
+}