core: run rclone as mount helper - #5594

lib/daemonize/daemon_unix.go

@@ -7,6 +7,7 @@ package daemonize
 
 import (
 	"os"
+	"strings"
 	"syscall"
 
 	"github.com/rclone/rclone/fs"
@@ -29,6 +30,18 @@ func StartDaemon(args []string) (*os.Process, error) {
 		me = os.Args[0]
 	}
 
+	// os.Executable might have resolved symbolic link to the executable
+	// so we run the background process with pre-converted CLI arguments.
+	// Double conversion is still probable but isn't a problem as it should
+	// preserve the converted command line.
+	if len(args) != 0 {
+		args[0] = me
+	}
+
+	if fs.PassDaemonArgsAsEnviron {
+		args, env = argsToEnv(args, env)
+	}
+
 	null, err := os.Open(os.DevNull)
 	if err != nil {
 		return nil, err
@@ -57,3 +70,42 @@ func StartDaemon(args []string) (*os.Process, error) {
 
 	return daemon, nil
 }
+
+// Processed command line flags of mount helper have simple structure:
+// `--flag` or `--flag=value` but never `--flag value` or `-x`
+// so we can easily pass them as environment variables.
+func argsToEnv(origArgs, origEnv []string) (args, env []string) {
+	env = origEnv
+	if len(origArgs) == 0 {
+		return
+	}
+	args = []string{origArgs[0]}
+	for _, arg := range origArgs[1:] {
+		if !strings.HasPrefix(arg, "--") {
+			args = append(args, arg)
+			continue
+		}
+
+		arg = arg[2:]
+		key, val := arg, "true"
+		if idx := strings.Index(arg, "="); idx != -1 {
+			key, val = arg[:idx], arg[idx+1:]
+		}
+
+		name := "RCLONE_" + strings.ToUpper(strings.ReplaceAll(key, "-", "_"))
+
+		pref := name + "="
+		line := name + "=" + val
+		found := false
+		for i, s := range env {
+			if strings.HasPrefix(s, pref) {
+				env[i] = line
+				found = true
+			}
+		}
+		if !found {
+			env = append(env, line)
+		}
+	}
+	return
+}