ctlsock: delete colliding orphaned socket file

Detect and delete an orphaned socket file that collides with
the ctlsock we want to create.

Fixes https://github.com/rfjakob/gocryptfs/issues/776

1 files changed, 35 insertions, 0 deletions

diff --git a/internal/ctlsocksrv/ctlsock_listen.go b/internal/ctlsocksrv/ctlsock_listen.go
index 1db9cbc..94ffca4 100644
--- a/internal/ctlsocksrv/ctlsock_listen.go
+++ b/internal/ctlsocksrv/ctlsock_listen.go
@@ -1,9 +1,44 @@
 package ctlsocksrv
 
 import (
+	"errors"
+	"io/fs"
 	"net"
+	"os"
+	"syscall"
+	"time"
+
+	"github.com/rfjakob/gocryptfs/v2/internal/tlog"
 )
 
+// cleanupOrphanedSocket deletes an orphaned socket file at `path`.
+// The file at `path` will only be deleted if:
+// 1) It is a socket file
+// 2) Connecting to it results in ECONNREFUSED
+func cleanupOrphanedSocket(path string) {
+	fi, err := os.Stat(path)
+	if err != nil {
+		return
+	}
+	if fi.Mode().Type() != fs.ModeSocket {
+		return
+	}
+	conn, err := net.DialTimeout("unix", path, time.Second)
+	if err == nil {
+		// This socket file is still active. Don't delete it.
+		conn.Close()
+		return
+	}
+	if errors.Is(err, syscall.ECONNREFUSED) {
+		tlog.Info.Printf("ctlsock: deleting orphaned socket file %q\n", path)
+		err = os.Remove(path)
+		if err != nil {
+			tlog.Warn.Printf("ctlsock: deleting socket file failed: %v", path)
+		}
+	}
+}
+
 func Listen(path string) (net.Listener, error) {
+	cleanupOrphanedSocket(path)
 	return net.Listen("unix", path)
 }