From b962d7d791bb13830d62d7ae326780b413463971 Mon Sep 17 00:00:00 2001
From: Brady OBrien <brady.obrien128@gmail.com>
Date: Thu, 17 May 2018 17:58:54 -0500
Subject: [PATCH] Add FreeBSD support
Signed-off-by: Brady OBrien <brady.obrien128@gmail.com>
---
rwcancel/fdset_default.go | 24 +
rwcancel/fdset_freebsd.go | 22 +
rwcancel/{rwcancel_unix.go => rwcancel.go} | 26 +-
.../{select_darwin.go => select_default.go} | 2 +
tun_freebsd.go | 507 ++++++++++++++++++
tun_freebsd_386.go | 18 +
tun_freebsd_amd64.go | 18 +
uapi_freebsd.go | 195 +++++++
8 files changed, 792 insertions(+), 20 deletions(-)
create mode 100644 rwcancel/fdset_default.go
create mode 100644 rwcancel/fdset_freebsd.go
rename rwcancel/{rwcancel_unix.go => rwcancel.go} (88%)
rename rwcancel/{select_darwin.go => select_default.go} (94%)
create mode 100644 tun_freebsd.go
create mode 100644 tun_freebsd_386.go
create mode 100644 tun_freebsd_amd64.go
create mode 100644 uapi_freebsd.go
diff --git a/rwcancel/fdset_default.go b/rwcancel/fdset_default.go
new file mode 100644
index 0000000..06e2695
--- /dev/null
+++ b/rwcancel/fdset_default.go
@@ -0,0 +1,24 @@
+// +build !freebsd
+
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+package rwcancel
+
+import "golang.org/x/sys/unix"
+
+type fdSet struct {
+ fdset unix.FdSet
+}
+
+func (fdset *fdSet) set(i int) {
+ bits := 32 << (^uint(0) >> 63)
+ fdset.fdset.Bits[i/bits] |= 1 << uint(i%bits)
+}
+
+func (fdset *fdSet) check(i int) bool {
+ bits := 32 << (^uint(0) >> 63)
+ return (fdset.fdset.Bits[i/bits] & (1 << uint(i%bits))) != 0
+}
diff --git a/rwcancel/fdset_freebsd.go b/rwcancel/fdset_freebsd.go
new file mode 100644
index 0000000..39a7a4e
--- /dev/null
+++ b/rwcancel/fdset_freebsd.go
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+package rwcancel
+
+import "golang.org/x/sys/unix"
+
+type fdSet struct {
+ fdset unix.FdSet
+}
+
+func (fdset *fdSet) set(i int) {
+ bits := 32 << (^uint(0) >> 63)
+ fdset.fdset.X__fds_bits[i/bits] |= 1 << uint(i%bits)
+}
+
+func (fdset *fdSet) check(i int) bool {
+ bits := 32 << (^uint(0) >> 63)
+ return (fdset.fdset.X__fds_bits[i/bits] & (1 << uint(i%bits))) != 0
+}
diff --git a/rwcancel/rwcancel_unix.go b/rwcancel/rwcancel.go
similarity index 88%
rename from rwcancel/rwcancel_unix.go
rename to rwcancel/rwcancel.go
index 739a8c3..aac743a 100644
--- a/rwcancel/rwcancel_unix.go
+++ b/rwcancel/rwcancel.go
@@ -12,26 +12,6 @@ import (
"syscall"
)
-type RWCancel struct {
- fd int
- closingReader *os.File
- closingWriter *os.File
-}
-
-type fdSet struct {
- fdset unix.FdSet
-}
-
-func (fdset *fdSet) set(i int) {
- bits := 32 << (^uint(0) >> 63)
- fdset.fdset.Bits[i/bits] |= 1 << uint(i%bits)
-}
-
-func (fdset *fdSet) check(i int) bool {
- bits := 32 << (^uint(0) >> 63)
- return (fdset.fdset.Bits[i/bits] & (1 << uint(i%bits))) != 0
-}
-
func max(a, b int) int {
if a > b {
return a
@@ -39,6 +19,12 @@ func max(a, b int) int {
return b
}
+type RWCancel struct {
+ fd int
+ closingReader *os.File
+ closingWriter *os.File
+}
+
func NewRWCancel(fd int) (*RWCancel, error) {
err := unix.SetNonblock(fd, true)
if err != nil {
diff --git a/rwcancel/select_darwin.go b/rwcancel/select_default.go
similarity index 94%
rename from rwcancel/select_darwin.go
rename to rwcancel/select_default.go
index d14edc8..302a618 100644
--- a/rwcancel/select_darwin.go
+++ b/rwcancel/select_default.go
@@ -3,6 +3,8 @@
* Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*/
+// +build !linux
+
package rwcancel
import "golang.org/x/sys/unix"
diff --git a/tun_freebsd.go b/tun_freebsd.go
new file mode 100644
index 0000000..e83b8ef
--- /dev/null
+++ b/tun_freebsd.go
@@ -0,0 +1,507 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+package main
+
+import (
+ "./rwcancel"
+ "bytes"
+ "errors"
+ "fmt"
+ "golang.org/x/net/ipv6"
+ "golang.org/x/sys/unix"
+ "io/ioutil"
+ "net"
+ "os"
+ "path/filepath"
+ "time"
+ "unsafe"
+)
+
+// _TUNSIFHEAD, value derived from sys/net/{if_tun,ioccom}.h
+// const _TUNSIFHEAD = ((0x80000000) | (((4) & ((1 << 13) - 1) ) << 16) | (uint32(byte('t')) << 8) | (96))
+const _TUNSIFHEAD = 0x80047460
+const _TUNSIFMODE = 0x8004745e
+const _TUNSIFPID = 0x2000745f
+
+// Iface status string max len
+const _IFSTATMAX = 800
+
+// Structure for iface mtu get/set ioctls
+type ifreq_mtu struct {
+ Name [_IFNAMESIZ]byte
+ MTU uint32
+ Pad0 [12]byte
+}
+
+// Structure for interface status request ioctl
+type ifstat struct {
+ IfsName [_IFNAMESIZ]byte
+ Ascii [_IFSTATMAX]byte
+}
+
+// NativeTun is a hack to work around the first 4 bytes "packet
+// information" because there doesn't seem to be an IFF_NO_PI for darwin.
+type NativeTun struct {
+ name string
+ fd *os.File
+ rwcancel *rwcancel.RWCancel
+ mtu int
+ events chan TUNEvent
+ errors chan error
+ statusListenersShutdown chan struct{}
+}
+
+// Figure out the interface name for an open tun device file descriptor
+func TunIfaceName(f *os.File) (string, error) {
+ //Terrible hack to make up for freebsd not having a TUNGIFNAME
+
+ fd := f.Fd()
+ //First, make sure the tun pid matches this proc's pid
+
+ _, _, errno := unix.Syscall(
+ unix.SYS_IOCTL,
+ uintptr(fd),
+ uintptr(_TUNSIFPID),
+ uintptr(0),
+ )
+
+ if errno != 0 {
+ return "", fmt.Errorf("Failed to set tun device PID: %s", errno.Error())
+ }
+
+ // Open iface control socket
+
+ confd, err := unix.Socket(
+ unix.AF_INET,
+ unix.SOCK_DGRAM,
+ 0,
+ )
+
+ defer unix.Close(confd)
+
+ if err != nil {
+ return "", err
+ }
+
+ procPid := os.Getpid()
+
+ //Try to find interface with matching PID
+ for i := 1; ; i++ {
+ iface, _ := net.InterfaceByIndex(i)
+ if err != nil || iface == nil {
+ break
+ }
+
+ // Structs for getting data in and out of SIOCGIFSTATUS ioctl
+ var ifstatus ifstat
+ ifname := iface.Name
+ copy(ifstatus.IfsName[:], ifname)
+
+ // Make the syscall to get the status string
+ _, _, errno := unix.Syscall(
+ unix.SYS_IOCTL,
+ uintptr(confd),
+ uintptr(unix.SIOCGIFSTATUS),
+ uintptr(unsafe.Pointer(&ifstatus)),
+ )
+
+ if errno != 0 {
+ continue
+ }
+
+ nullStr := ifstatus.Ascii[:]
+ i := bytes.IndexByte(nullStr, 0)
+ if i < 1 {
+ continue
+ }
+ if i != -1 {
+ nullStr = nullStr[:i]
+ }
+ statStr := string(nullStr)
+ var pidNum int = 0
+
+ // Finally get the owning PID
+ // Format string taken from sys/net/if_tun.c
+ _, err := fmt.Sscanf(statStr, "\tOpened by PID %d\n", &pidNum)
+ if err != nil {
+ return "", err
+ }
+
+ if pidNum == procPid {
+ return ifname, nil
+ }
+
+ }
+
+ return "", nil
+}
+
+// Destroy a named system interface
+func DestroyIface(name string) error {
+ // open control socket
+ var fd int
+
+ fd, err := unix.Socket(
+ unix.AF_INET,
+ unix.SOCK_DGRAM,
+ 0,
+ )
+
+ if err != nil {
+ return err
+ }
+
+ defer unix.Close(fd)
+
+ // do ioctl call
+
+ var ifr [32]byte
+ copy(ifr[:], name)
+ _, _, errno := unix.Syscall(
+ unix.SYS_IOCTL,
+ uintptr(fd),
+ uintptr(unix.SIOCIFDESTROY),
+ uintptr(unsafe.Pointer(&ifr[0])),
+ )
+
+ if errno != 0 {
+ return fmt.Errorf("Failed to destroy interface %s: %s", name, errno.Error())
+ }
+
+ return nil
+}
+
+func CreateTUN(name string) (TUNDevice, error) {
+ if len(name) > _IFNAMESIZ-1 {
+ return nil, errors.New("Interface name too long")
+ }
+
+ // See if interface already exists
+ iface, _ := net.InterfaceByName(name)
+ if iface != nil {
+ return nil, fmt.Errorf("Interface %s already exists", name)
+ }
+
+ tunfile, err := os.OpenFile("/dev/tun", unix.O_RDWR, 0)
+
+ if err != nil {
+ return nil, err
+ }
+
+ nameif, err := TunIfaceName(tunfile)
+
+ if err != nil {
+ tunfile.Close()
+ return nil, err
+ }
+
+ tunfd := tunfile.Fd()
+
+ // Enable ifhead mode, otherwise tun will complain if it gets a non-AF_INET packet
+ ifheadmode := 1
+ _, _, errno := unix.Syscall(
+ unix.SYS_IOCTL,
+ uintptr(tunfd),
+ uintptr(_TUNSIFHEAD),
+ uintptr(unsafe.Pointer(&ifheadmode)),
+ )
+
+ if errno != 0 {
+ return nil, fmt.Errorf("Error %s", errno.Error())
+ }
+
+ /* Set TUN iface to broadcast mode. TUN inferfaces on freebsd come up
+ * point to point by default */
+ ifmodemode := unix.IFF_BROADCAST
+ _, _, errno = unix.Syscall(
+ unix.SYS_IOCTL,
+ uintptr(tunfd),
+ uintptr(_TUNSIFMODE),
+ uintptr(unsafe.Pointer(&ifmodemode)),
+ )
+
+ if errno != 0 {
+ return nil, fmt.Errorf("Error %s", errno.Error())
+ }
+
+ // Rename tun interface
+ // Open control socket
+ ctfd, err := unix.Socket(
+ unix.AF_INET,
+ unix.SOCK_DGRAM,
+ 0,
+ )
+
+ if err != nil {
+ return nil, err
+ }
+
+ defer unix.Close(ctfd)
+
+ // set up struct for iface rename
+ var newnp [_IFNAMESIZ]byte
+ copy(newnp[:], name)
+
+ var ifr ifreq_ptr
+ copy(ifr.Name[:], nameif)
+ ifr.Data = uintptr(unsafe.Pointer(&newnp[0]))
+
+ //do actual ioctl to rename iface
+ _, _, errno = unix.Syscall(
+ unix.SYS_IOCTL,
+ uintptr(ctfd),
+ uintptr(unix.SIOCSIFNAME),
+ uintptr(unsafe.Pointer(&ifr)),
+ )
+ if errno != 0 {
+ tunfile.Close()
+ DestroyIface(name)
+ return nil, fmt.Errorf("Failed to rename %s to %s: %s", nameif, name, errno.Error())
+ }
+
+ tun, err := CreateTUNFromFile(tunfile)
+
+ if err != nil {
+ return nil, err
+ }
+
+ if err == nil && name == "tun" {
+ fname := os.Getenv("WG_FREEBSD_TUN_NAME_FILE")
+ if fname != "" {
+ os.MkdirAll(filepath.Dir(fname), 0700)
+ ioutil.WriteFile(fname, []byte(tun.(*NativeTun).name+"\n"), 0400)
+ }
+ }
+
+ return tun, err
+}
+
+func CreateTUNFromFile(file *os.File) (TUNDevice, error) {
+
+ tun := &NativeTun{
+ fd: file,
+ mtu: 1500,
+ events: make(chan TUNEvent, 10),
+ errors: make(chan error, 1),
+ statusListenersShutdown: make(chan struct{}),
+ }
+
+ _, err := tun.Name()
+
+ if err != nil {
+ tun.fd.Close()
+ return nil, err
+ }
+
+ tun.rwcancel, err = rwcancel.NewRWCancel(int(file.Fd()))
+ if err != nil {
+ tun.fd.Close()
+ return nil, err
+ }
+
+ // TODO: Fix this very naive implementation
+ go func(tun *NativeTun) {
+ var (
+ statusUp bool
+ statusMTU int
+ )
+
+ for {
+ intr, err := net.InterfaceByName(tun.name)
+ if err != nil {
+ tun.errors <- err
+ return
+ }
+
+ // Up / Down event
+ up := (intr.Flags & net.FlagUp) != 0
+ if up != statusUp && up {
+ tun.events <- TUNEventUp
+ }
+ if up != statusUp && !up {
+ tun.events <- TUNEventDown
+ }
+ statusUp = up
+
+ // MTU changes
+ if intr.MTU != statusMTU {
+ tun.events <- TUNEventMTUUpdate
+ }
+ statusMTU = intr.MTU
+
+ select {
+ case <-time.After(time.Second / 10):
+ case <-tun.statusListenersShutdown:
+ return
+ }
+ }
+ }(tun)
+
+ // set default MTU
+ err = tun.setMTU(DefaultMTU)
+ if err != nil {
+ tun.Close()
+ return nil, err
+ }
+
+ return tun, nil
+}
+
+func (tun *NativeTun) Name() (string, error) {
+ name, err := TunIfaceName(tun.fd)
+ if err != nil {
+ return "", err
+ }
+ tun.name = name
+ return name, nil
+}
+
+func (tun *NativeTun) File() *os.File {
+ return tun.fd
+}
+
+func (tun *NativeTun) Events() chan TUNEvent {
+ return tun.events
+}
+
+func (tun *NativeTun) doRead(buff []byte, offset int) (int, error) {
+ select {
+ case err := <-tun.errors:
+ return 0, err
+ default:
+ buff := buff[offset-4:]
+ n, err := tun.fd.Read(buff[:])
+ if n < 4 {
+ return 0, err
+ }
+ return n - 4, err
+ }
+}
+
+func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
+ for {
+ n, err := tun.doRead(buff, offset)
+ if err == nil || !rwcancel.ErrorIsEAGAIN(err) {
+ return n, err
+ }
+ if !tun.rwcancel.ReadyRead() {
+ return 0, errors.New("tun device closed")
+ }
+ }
+}
+
+func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
+
+ // reserve space for header
+
+ buff = buff[offset-4:]
+
+ // add packet information header
+
+ buff[0] = 0x00
+ buff[1] = 0x00
+ buff[2] = 0x00
+
+ if buff[4]>>4 == ipv6.Version {
+ buff[3] = unix.AF_INET6
+ } else {
+ buff[3] = unix.AF_INET
+ }
+
+ // write
+
+ return tun.fd.Write(buff)
+}
+
+func (tun *NativeTun) Close() error {
+ close(tun.statusListenersShutdown)
+ err1 := tun.rwcancel.Cancel()
+ err2 := tun.fd.Close()
+ err3 := DestroyIface(tun.name)
+ close(tun.events)
+ if err1 != nil {
+ return err1
+ }
+ if err2 != nil {
+ return err2
+ }
+ return err3
+}
+
+func (tun *NativeTun) setMTU(n int) error {
+ // open datagram socket
+
+ var fd int
+
+ fd, err := unix.Socket(
+ unix.AF_INET,
+ unix.SOCK_DGRAM,
+ 0,
+ )
+
+ if err != nil {
+ return err
+ }
+
+ defer unix.Close(fd)
+
+ // do ioctl call
+
+ var ifr ifreq_mtu
+ copy(ifr.Name[:], tun.name)
+ ifr.MTU = uint32(n)
+
+ _, _, errno := unix.Syscall(
+ unix.SYS_IOCTL,
+ uintptr(fd),
+ uintptr(unix.SIOCSIFMTU),
+ uintptr(unsafe.Pointer(&ifr)),
+ )
+
+ if errno != 0 {
+ return fmt.Errorf("Failed to set MTU on %s", tun.name)
+ }
+
+ return nil
+}
+
+func (tun *NativeTun) MTU() (int, error) {
+ // open datagram socket
+
+ fd, err := unix.Socket(
+ unix.AF_INET,
+ unix.SOCK_DGRAM,
+ 0,
+ )
+
+ if err != nil {
+ return 0, err
+ }
+
+ defer unix.Close(fd)
+
+ // do ioctl call
+ var ifr ifreq_mtu
+ copy(ifr.Name[:], tun.name)
+
+ _, _, errno := unix.Syscall(
+ unix.SYS_IOCTL,
+ uintptr(fd),
+ uintptr(unix.SIOCGIFMTU),
+ uintptr(unsafe.Pointer(&ifr)),
+ )
+ if errno != 0 {
+ return 0, fmt.Errorf("Failed to get MTU on %s", tun.name)
+ }
+
+ // convert result to signed 32-bit int
+ mtu := ifr.MTU
+ if mtu >= (1 << 31) {
+ return int(mtu-(1<<31)) - (1 << 31), nil
+ }
+ return int(mtu), nil
+
+}
diff --git a/tun_freebsd_386.go b/tun_freebsd_386.go
new file mode 100644
index 0000000..13e9d95
--- /dev/null
+++ b/tun_freebsd_386.go
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+/* Types to deal with FreeBSD fdiogname ioctl for determining tun device name */
+
+package main
+
+// Iface name max len
+const _IFNAMESIZ = 16
+
+// structure for iface requests with a pointer
+type ifreq_ptr struct {
+ Name [_IFNAMESIZ]byte
+ Data uintptr
+ Pad0 [20]byte
+}
diff --git a/tun_freebsd_amd64.go b/tun_freebsd_amd64.go
new file mode 100644
index 0000000..6b08caf
--- /dev/null
+++ b/tun_freebsd_amd64.go
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+/* Types to deal with FreeBSD fdiogname ioctl for determining tun device name */
+
+package main
+
+// Iface name max len
+const _IFNAMESIZ = 16
+
+// structure for iface requests with a pointer
+type ifreq_ptr struct {
+ Name [_IFNAMESIZ]byte
+ Data uintptr
+ Pad0 [16]byte
+}
diff --git a/uapi_freebsd.go b/uapi_freebsd.go
new file mode 100644
index 0000000..6a8fe8d
--- /dev/null
+++ b/uapi_freebsd.go
@@ -0,0 +1,195 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+package main
+
+import (
+ "errors"
+ "fmt"
+ "golang.org/x/sys/unix"
+ "net"
+ "os"
+ "path"
+)
+
+const (
+ ipcErrorIO = -int64(unix.EIO)
+ ipcErrorProtocol = -int64(unix.EPROTO)
+ ipcErrorInvalid = -int64(unix.EINVAL)
+ ipcErrorPortInUse = -int64(unix.EADDRINUSE)
+ socketDirectory = "/var/run/wireguard"
+ socketName = "%s.sock"
+)
+
+type UAPIListener struct {
+ listener net.Listener // unix socket listener
+ connNew chan net.Conn
+ connErr chan error
+ kqueueFd int
+ keventFd int
+}
+
+func (l *UAPIListener) Accept() (net.Conn, error) {
+ for {
+ select {
+ case conn := <-l.connNew:
+ return conn, nil
+
+ case err := <-l.connErr:
+ return nil, err
+ }
+ }
+}
+
+func (l *UAPIListener) Close() error {
+ err1 := unix.Close(l.kqueueFd)
+ err2 := unix.Close(l.keventFd)
+ err3 := l.listener.Close()
+ if err1 != nil {
+ return err1
+ }
+ if err2 != nil {
+ return err2
+ }
+ return err3
+}
+
+func (l *UAPIListener) Addr() net.Addr {
+ return l.listener.Addr()
+}
+
+func UAPIListen(name string, file *os.File) (net.Listener, error) {
+
+ // wrap file in listener
+
+ listener, err := net.FileListener(file)
+ if err != nil {
+ return nil, err
+ }
+
+ uapi := &UAPIListener{
+ listener: listener,
+ connNew: make(chan net.Conn, 1),
+ connErr: make(chan error, 1),
+ }
+
+ if unixListener, ok := listener.(*net.UnixListener); ok {
+ unixListener.SetUnlinkOnClose(true)
+ }
+
+ socketPath := path.Join(
+ socketDirectory,
+ fmt.Sprintf(socketName, name),
+ )
+
+ // watch for deletion of socket
+
+ uapi.kqueueFd, err = unix.Kqueue()
+ if err != nil {
+ return nil, err
+ }
+ // TODO: Double check socket deletion logic port from MacOS
+ uapi.keventFd, err = unix.Open(socketDirectory, unix.O_RDONLY, 0)
+ if err != nil {
+ unix.Close(uapi.kqueueFd)
+ return nil, err
+ }
+
+ go func(l *UAPIListener) {
+ event := unix.Kevent_t{
+ Ident: uint64(uapi.keventFd),
+ Filter: unix.EVFILT_VNODE,
+ Flags: unix.EV_ADD | unix.EV_ENABLE | unix.EV_ONESHOT,
+ Fflags: unix.NOTE_WRITE,
+ }
+ events := make([]unix.Kevent_t, 1)
+ n := 1
+ var kerr error
+ for {
+ // start with lstat to avoid race condition
+ if _, err := os.Lstat(socketPath); os.IsNotExist(err) {
+ l.connErr <- err
+ return
+ }
+ if kerr != nil || n != 1 {
+ if kerr != nil {
+ l.connErr <- kerr
+ } else {
+ l.connErr <- errors.New("kqueue returned empty")
+ }
+ return
+ }
+ n, kerr = unix.Kevent(uapi.kqueueFd, []unix.Kevent_t{event}, events, nil)
+ }
+ }(uapi)
+
+ // watch for new connections
+
+ go func(l *UAPIListener) {
+ for {
+ conn, err := l.listener.Accept()
+ if err != nil {
+ l.connErr <- err
+ break
+ }
+ l.connNew <- conn
+ }
+ }(uapi)
+
+ return uapi, nil
+}
+
+func UAPIOpen(name string) (*os.File, error) {
+
+ // check if path exist
+
+ err := os.MkdirAll(socketDirectory, 0700)
+ if err != nil && !os.IsExist(err) {
+ return nil, err
+ }
+
+ // open UNIX socket
+
+ socketPath := path.Join(
+ socketDirectory,
+ fmt.Sprintf(socketName, name),
+ )
+
+ addr, err := net.ResolveUnixAddr("unix", socketPath)
+ if err != nil {
+ return nil, err
+ }
+
+ listener, err := func() (*net.UnixListener, error) {
+
+ // initial connection attempt
+
+ listener, err := net.ListenUnix("unix", addr)
+ if err == nil {
+ return listener, nil
+ }
+
+ // check if socket already active
+
+ _, err = net.Dial("unix", socketPath)
+ if err == nil {
+ return nil, errors.New("unix socket in use")
+ }
+
+ // cleanup & attempt again
+
+ err = os.Remove(socketPath)
+ if err != nil {
+ return nil, err
+ }
+ return net.ListenUnix("unix", addr)
+ }()
+
+ if err != nil {
+ return nil, err
+ }
+
+ return listener.File()
+}