wintun: do not load dll in init()

This prevents linking to wintun.dll until it's actually needed, which
should improve startup time.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

5 files changed, 21 insertions, 14 deletions

diff --git a/tun/wintun/dll_fromfile_windows.go b/tun/wintun/dll_fromfile_windows.go
index 525812b..f40f8b3 100644
--- a/tun/wintun/dll_fromfile_windows.go
+++ b/tun/wintun/dll_fromfile_windows.go
@@ -20,6 +20,7 @@ type lazyDLL struct {
 	Name   string
 	mu     sync.Mutex
 	module windows.Handle
+	onLoad func(d *lazyDLL)
 }
 
 func (d *lazyDLL) Load() error {
@@ -42,6 +43,9 @@ func (d *lazyDLL) Load() error {
 	}
 
 	atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&d.module)), unsafe.Pointer(module))
+	if d.onLoad != nil {
+		d.onLoad(d)
+	}
 	return nil
 }
 
diff --git a/tun/wintun/dll_fromrsrc_windows.go b/tun/wintun/dll_fromrsrc_windows.go
index e6e393f..d107ba9 100644
--- a/tun/wintun/dll_fromrsrc_windows.go
+++ b/tun/wintun/dll_fromrsrc_windows.go
@@ -23,6 +23,7 @@ type lazyDLL struct {
 	Name   string
 	mu     sync.Mutex
 	module *memmod.Module
+	onLoad func(d *lazyDLL)
 }
 
 func (d *lazyDLL) Load() error {
@@ -50,6 +51,9 @@ func (d *lazyDLL) Load() error {
 	}
 
 	atomic.StorePointer((*unsafe.Pointer)(unsafe.Pointer(&d.module)), unsafe.Pointer(module))
+	if d.onLoad != nil {
+		d.onLoad(d)
+	}
 	return nil
 }
 
diff --git a/tun/wintun/dll_windows.go b/tun/wintun/dll_windows.go
index 9f04f73..dd97bbc 100644
--- a/tun/wintun/dll_windows.go
+++ b/tun/wintun/dll_windows.go
@@ -12,8 +12,8 @@ import (
 	"unsafe"
 )
 
-func newLazyDLL(name string) *lazyDLL {
-	return &lazyDLL{Name: name}
+func newLazyDLL(name string, onLoad func(d *lazyDLL)) *lazyDLL {
+	return &lazyDLL{Name: name, onLoad: onLoad}
 }
 
 func (d *lazyDLL) NewProc(name string) *lazyProc {
diff --git a/tun/wintun/session_windows.go b/tun/wintun/session_windows.go
index 1619e5a..5b24fa5 100644
--- a/tun/wintun/session_windows.go
+++ b/tun/wintun/session_windows.go
@@ -30,12 +30,12 @@ type Packet struct {
 }
 
 var (
-	procWintunAllocateSendPacket   = modwintun.NewProc("WintunAllocateSendPacket").Addr()
+	procWintunAllocateSendPacket   = modwintun.NewProc("WintunAllocateSendPacket")
 	procWintunEndSession           = modwintun.NewProc("WintunEndSession")
 	procWintunGetReadWaitEvent     = modwintun.NewProc("WintunGetReadWaitEvent")
-	procWintunReceivePacket        = modwintun.NewProc("WintunReceivePacket").Addr()
-	procWintunReleaseReceivePacket = modwintun.NewProc("WintunReleaseReceivePacket").Addr()
-	procWintunSendPacket           = modwintun.NewProc("WintunSendPacket").Addr()
+	procWintunReceivePacket        = modwintun.NewProc("WintunReceivePacket")
+	procWintunReleaseReceivePacket = modwintun.NewProc("WintunReleaseReceivePacket")
+	procWintunSendPacket           = modwintun.NewProc("WintunSendPacket")
 	procWintunStartSession         = modwintun.NewProc("WintunStartSession")
 )
 
@@ -62,7 +62,7 @@ func (session Session) ReadWaitEvent() (handle windows.Handle) {
 
 func (session Session) ReceivePacket() (packet []byte, err error) {
 	var packetSize uint32
-	r0, _, e1 := syscall.Syscall(procWintunReceivePacket, 2, session.handle, uintptr(unsafe.Pointer(&packetSize)), 0)
+	r0, _, e1 := syscall.Syscall(procWintunReceivePacket.Addr(), 2, session.handle, uintptr(unsafe.Pointer(&packetSize)), 0)
 	if r0 == 0 {
 		err = e1
 		return
@@ -72,11 +72,11 @@ func (session Session) ReceivePacket() (packet []byte, err error) {
 }
 
 func (session Session) ReleaseReceivePacket(packet []byte) {
-	syscall.Syscall(procWintunReleaseReceivePacket, 2, session.handle, uintptr(unsafe.Pointer(&packet[0])), 0)
+	syscall.Syscall(procWintunReleaseReceivePacket.Addr(), 2, session.handle, uintptr(unsafe.Pointer(&packet[0])), 0)
 }
 
 func (session Session) AllocateSendPacket(packetSize int) (packet []byte, err error) {
-	r0, _, e1 := syscall.Syscall(procWintunAllocateSendPacket, 2, session.handle, uintptr(packetSize), 0)
+	r0, _, e1 := syscall.Syscall(procWintunAllocateSendPacket.Addr(), 2, session.handle, uintptr(packetSize), 0)
 	if r0 == 0 {
 		err = e1
 		return
@@ -86,7 +86,7 @@ func (session Session) AllocateSendPacket(packetSize int) (packet []byte, err er
 }
 
 func (session Session) SendPacket(packet []byte) {
-	syscall.Syscall(procWintunSendPacket, 2, session.handle, uintptr(unsafe.Pointer(&packet[0])), 0)
+	syscall.Syscall(procWintunSendPacket.Addr(), 2, session.handle, uintptr(unsafe.Pointer(&packet[0])), 0)
 }
 
 // unsafeSlice updates the slice slicePtr to be a slice
diff --git a/tun/wintun/wintun_windows.go b/tun/wintun/wintun_windows.go
index e7ba8b6..afbbe76 100644
--- a/tun/wintun/wintun_windows.go
+++ b/tun/wintun/wintun_windows.go
@@ -34,7 +34,7 @@ type Adapter struct {
 }
 
 var (
-	modwintun = newLazyDLL("wintun.dll")
+	modwintun = newLazyDLL("wintun.dll", setupLogger)
 
 	procWintunCreateAdapter           = modwintun.NewProc("WintunCreateAdapter")
 	procWintunDeleteAdapter           = modwintun.NewProc("WintunDeleteAdapter")
@@ -46,11 +46,10 @@ var (
 	procWintunGetAdapterName          = modwintun.NewProc("WintunGetAdapterName")
 	procWintunGetRunningDriverVersion = modwintun.NewProc("WintunGetRunningDriverVersion")
 	procWintunSetAdapterName          = modwintun.NewProc("WintunSetAdapterName")
-	procWintunSetLogger               = modwintun.NewProc("WintunSetLogger")
 )
 
-func init() {
-	syscall.Syscall(procWintunSetLogger.Addr(), 1, windows.NewCallback(func(level loggerLevel, msg *uint16) int {
+func setupLogger(dll *lazyDLL) {
+	syscall.Syscall(dll.NewProc("WintunSetLogger").Addr(), 1, windows.NewCallback(func(level loggerLevel, msg *uint16) int {
 		log.Println("[Wintun]", windows.UTF16PtrToString(msg))
 		return 0
 	}), 0, 0)