From cbb13ba8d29c65dd5661be449c56563edcb7f5a1 Mon Sep 17 00:00:00 2001
From: Glonee <glonee@foxmail.com>
Date: Thu, 16 Nov 2023 22:05:35 +0800
Subject: [PATCH] fuse: parse socket control message using the standard library

make mount procedure cleaner by using standard library
to parse socker control message

Change-Id: Ic52f5a0e2ddda40e680e341e35fb9b4158ba3324
---
 fuse/mount.go        | 48 ++++++++++++++++++++++++++++++++++++++++++++
 fuse/mount_darwin.go | 28 --------------------------
 fuse/mount_linux.go  | 28 --------------------------
 3 files changed, 48 insertions(+), 56 deletions(-)
 create mode 100644 fuse/mount.go

diff --git a/fuse/mount.go b/fuse/mount.go
new file mode 100644
index 000000000..874d9c459
--- /dev/null
+++ b/fuse/mount.go
@@ -0,0 +1,48 @@
+package fuse
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"syscall"
+)
+
+func getConnection(local *os.File) (int, error) {
+	conn, err := net.FileConn(local)
+	if err != nil {
+		return 0, err
+	}
+	defer conn.Close()
+	unixConn := conn.(*net.UnixConn)
+
+	var data [4]byte
+	control := make([]byte, 4*256)
+
+	_, oobn, _, _, err := unixConn.ReadMsgUnix(data[:], control[:])
+	if err != nil {
+		return 0, err
+	}
+
+	messages, err := syscall.ParseSocketControlMessage(control[:oobn])
+	if err != nil {
+		return 0, err
+	}
+	if len(messages) != 1 {
+		return 0, fmt.Errorf("getConnection: expect 1 control message, got %#v", messages)
+	}
+	message := messages[0]
+
+	fds, err := syscall.ParseUnixRights(&message)
+	if err != nil {
+		return 0, err
+	}
+	if len(fds) != 1 {
+		return 0, fmt.Errorf("getConnection: expect 1 fd, got %#v", fds)
+	}
+	fd := fds[0]
+
+	if fd < 0 {
+		return 0, fmt.Errorf("getConnection: fd < 0: %d", fd)
+	}
+	return fd, nil
+}
diff --git a/fuse/mount_darwin.go b/fuse/mount_darwin.go
index 1112799bb..cabdaa29c 100644
--- a/fuse/mount_darwin.go
+++ b/fuse/mount_darwin.go
@@ -11,7 +11,6 @@ import (
 	"os/exec"
 	"strings"
 	"syscall"
-	"unsafe"
 )
 
 func unixgramSocketpair() (l, r *os.File, err error) {
@@ -90,33 +89,6 @@ func unmount(dir string, opts *MountOptions) error {
 	return syscall.Unmount(dir, 0)
 }
 
-func getConnection(local *os.File) (int, error) {
-	var data [4]byte
-	control := make([]byte, 4*256)
-
-	// n, oobn, recvflags, from, errno  - todo: error checking.
-	_, oobn, _, _,
-		err := syscall.Recvmsg(
-		int(local.Fd()), data[:], control[:], 0)
-	if err != nil {
-		return 0, err
-	}
-
-	message := *(*syscall.Cmsghdr)(unsafe.Pointer(&control[0]))
-	fd := *(*int32)(unsafe.Pointer(uintptr(unsafe.Pointer(&control[0])) + syscall.SizeofCmsghdr))
-
-	if message.Type != syscall.SCM_RIGHTS {
-		return 0, fmt.Errorf("getConnection: recvmsg returned wrong control type: %d", message.Type)
-	}
-	if oobn <= syscall.SizeofCmsghdr {
-		return 0, fmt.Errorf("getConnection: too short control message. Length: %d", oobn)
-	}
-	if fd < 0 {
-		return 0, fmt.Errorf("getConnection: fd < 0: %d", fd)
-	}
-	return int(fd), nil
-}
-
 func fusermountBinary() (string, error) {
 	binPaths := []string{
 		"/Library/Filesystems/macfuse.fs/Contents/Resources/mount_macfuse",
diff --git a/fuse/mount_linux.go b/fuse/mount_linux.go
index c6abf035e..96111d3b7 100644
--- a/fuse/mount_linux.go
+++ b/fuse/mount_linux.go
@@ -12,7 +12,6 @@ import (
 	"path"
 	"strings"
 	"syscall"
-	"unsafe"
 )
 
 func unixgramSocketpair() (l, r *os.File, err error) {
@@ -203,33 +202,6 @@ func unmount(mountPoint string, opts *MountOptions) (err error) {
 	return err
 }
 
-func getConnection(local *os.File) (int, error) {
-	var data [4]byte
-	control := make([]byte, 4*256)
-
-	// n, oobn, recvflags, from, errno  - todo: error checking.
-	_, oobn, _, _,
-		err := syscall.Recvmsg(
-		int(local.Fd()), data[:], control[:], 0)
-	if err != nil {
-		return 0, err
-	}
-
-	message := *(*syscall.Cmsghdr)(unsafe.Pointer(&control[0]))
-	fd := *(*int32)(unsafe.Pointer(uintptr(unsafe.Pointer(&control[0])) + syscall.SizeofCmsghdr))
-
-	if message.Type != 1 {
-		return 0, fmt.Errorf("getConnection: recvmsg returned wrong control type: %d", message.Type)
-	}
-	if oobn <= syscall.SizeofCmsghdr {
-		return 0, fmt.Errorf("getConnection: too short control message. Length: %d", oobn)
-	}
-	if fd < 0 {
-		return 0, fmt.Errorf("getConnection: fd < 0: %d", fd)
-	}
-	return int(fd), nil
-}
-
 // lookPathFallback - search binary in PATH and, if that fails,
 // in fallbackDir. This is useful if PATH is possible empty.
 func lookPathFallback(file string, fallbackDir string) (string, error) {