cmd/serve: add serve docker command (#5415)

Fixes #4750

Co-authored-by: Ivan Andreev <ivandeex@gmail.com>

cmd/serve/docker/serve.go

@@ -0,0 +1,100 @@
+package docker
+
+import (
+	"context"
+	"crypto/tls"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"os"
+	"path/filepath"
+	"runtime"
+
+	"github.com/rclone/rclone/fs"
+	"github.com/rclone/rclone/lib/atexit"
+)
+
+// Server connects plugin with docker daemon by protocol
+type Server http.Server
+
+// NewServer creates new docker plugin server
+func NewServer(drv *Driver) *Server {
+	return &Server{Handler: newRouter(drv)}
+}
+
+// Shutdown the server
+func (s *Server) Shutdown(ctx context.Context) error {
+	hs := (*http.Server)(s)
+	return hs.Shutdown(ctx)
+}
+
+func (s *Server) serve(listener net.Listener, addr, tempFile string) error {
+	if tempFile != "" {
+		atexit.Register(func() {
+			// remove spec file or self-created unix socket
+			fs.Debugf(nil, "Removing stale file %s", tempFile)
+			_ = os.Remove(tempFile)
+		})
+	}
+	hs := (*http.Server)(s)
+	return hs.Serve(listener)
+}
+
+// ServeUnix makes the handler to listen for requests in a unix socket.
+// It also creates the socket file in the right directory for docker to read.
+func (s *Server) ServeUnix(path string, gid int) error {
+	listener, socketPath, err := newUnixListener(path, gid)
+	if err != nil {
+		return err
+	}
+	if socketPath != "" {
+		path = socketPath
+		fs.Infof(nil, "Serving unix socket: %s", path)
+	} else {
+		fs.Infof(nil, "Serving systemd socket")
+	}
+	return s.serve(listener, path, socketPath)
+}
+
+// ServeTCP makes the handler listen for request on a given TCP address.
+// It also writes the spec file in the right directory for docker to read.
+func (s *Server) ServeTCP(addr, specDir string, tlsConfig *tls.Config, noSpec bool) error {
+	listener, err := net.Listen("tcp", addr)
+	if err != nil {
+		return err
+	}
+	if tlsConfig != nil {
+		tlsConfig.NextProtos = []string{"http/1.1"}
+		listener = tls.NewListener(listener, tlsConfig)
+	}
+	addr = listener.Addr().String()
+	specFile := ""
+	if !noSpec {
+		specFile, err = writeSpecFile(addr, "tcp", specDir)
+		if err != nil {
+			return err
+		}
+	}
+	fs.Infof(nil, "Serving TCP socket: %s", addr)
+	return s.serve(listener, addr, specFile)
+}
+
+func writeSpecFile(addr, proto, specDir string) (string, error) {
+	if specDir == "" && runtime.GOOS == "windows" {
+		specDir = os.TempDir()
+	}
+	if specDir == "" {
+		specDir = defSpecDir
+	}
+	if err := os.MkdirAll(specDir, 0755); err != nil {
+		return "", err
+	}
+	specFile := filepath.Join(specDir, "rclone.spec")
+	url := fmt.Sprintf("%s://%s", proto, addr)
+	if err := ioutil.WriteFile(specFile, []byte(url), 0644); err != nil {
+		return "", err
+	}
+	fs.Debugf(nil, "Plugin spec has been written to %s", specFile)
+	return specFile, nil
+}