Calling NotifyIpInterfaceChange from Go caused Access Violation exceptions - windows

Question

This is the first time I have had to make calls to native libraries from Go.
I am trying to setup event hooks with the windows libraries to listen for network interface changes, so far I have been successful with setting up a listener with NotifyAddrChange.
Now I am trying with NotifyIpInterfaceChange with the following code
package main
import (
"golang.org/x/sys/windows"
"log"
"syscall"
"unsafe"
)
var (
modiphlpapi = windows.NewLazySystemDLL("iphlpapi.dll")
procNotifyIpInterfaceChange = modiphlpapi.NewProc("NotifyIpInterfaceChange")
)
type context struct{}
func main() {
log.Printf("Loaded [iphlpapi.dll] at {%#v}", modiphlpapi.Handle())
log.Printf("Found [NotifyIpInterfaceChange] at {%#v}", procNotifyIpInterfaceChange.Addr())
context := &context{}
interfaceChange := windows.Handle(0)
ret, _, errNum := procNotifyIpInterfaceChange.Call(syscall.AF_UNSPEC, syscall.NewCallback(callback), uintptr(unsafe.Pointer(context)), 0, uintptr(interfaceChange))
log.Printf("%#v %#v", ret, errNum)
}
func callback(callerContext, row, notificationType uintptr) uintptr {
log.Printf("callback invoked by Windows API (%#v %#v %#v)", callerContext, row, notificationType)
return 0
}
The code compiles fine and starts up without any issue, the problem happens once the function is invoke, then I get the following exception
D:\>event-listen_type2.exe
2017/06/22 22:12:39 Loaded [iphlpapi.dll] at {0x7ffac96f0000}
2017/06/22 22:12:39 Found [NotifyIpInterfaceChange] at {0x7ffac96f7e20}
Exception 0xc0000005 0x1 0x0 0x7ffac96f7edb
PC=0x7ffac96f7edb
syscall.Syscall6(0x7ffac96f7e20, 0x5, 0x0, 0x454170, 0x54d360, 0x0, 0x0, 0x0, 0xc042015350, 0xc042015300, ...)
/usr/local/Cellar/go/1.8.3/libexec/src/runtime/syscall_windows.go:174 +0x6b
github.com/LiamHaworth/windows-network-events/vendor/golang.org/x/sys/windows.(*Proc).Call(0xc04203a620, 0xc042050300, 0x5, 0x5, 0x30, 0x4b12e0, 0x1, 0xc042050300)
/Users/liam/git/go_path/src/github.com/LiamHaworth/windows-network-events/vendor/golang.org/x/sys/windows/dll_windows.go:139 +0x5c1
github.com/LiamHaworth/windows-network-events/vendor/golang.org/x/sys/windows.(*LazyProc).Call(0xc042050270, 0xc042050300, 0x5, 0x5, 0x1, 0xc04201a000, 0xc04202df78, 0x4043a3)
/Users/liam/git/go_path/src/github.com/LiamHaworth/windows-network-events/vendor/golang.org/x/sys/windows/dll_windows.go:309 +0x66
main.main()
/Users/liam/git/go_path/src/github.com/LiamHaworth/windows-network-events/main_windows.go:25 +0x229
rax 0x0
rbx 0xc3f10
rcx 0x1fb5cd87abfd0000
rdi 0x0
rsi 0x454170
rbp 0xc04202dc00
rsp 0x8fdf0
r8 0x8fb78
r9 0x7ffac96fb4c0
r10 0x0
r11 0x8fcf0
r12 0x0
r13 0xffffffee
r14 0x0
r15 0xaa
rip 0x7ffac96f7edb
rflags 0x10246
cs 0x33
fs 0x53
gs 0x2b
From some googling I know that exception type 0xc0000005 is a access violation thrown by the CPU when a program tries to access memory not allocated to it but looking through my code I can't tell where that is happening. All pointers passed are for items in the application.
Any help here would be magnificent.

Answer 1

According to documentation, the latest parameter of NotifyIpInterfaceChange is both in/out and need to be a pointer to HANDLE. Change the system call to:
ret, _, errNum := procNotifyIpInterfaceChange.Call(syscall.AF_UNSPEC,
syscall.NewCallback(callback),
uintptr(unsafe.Pointer(context)),
0,
uintptr(unsafe.Pointer(&interfaceChange))) //this must be pointer
EDIT:
As mentioned in the comment and this go-nuts discussion, for multi-threaded callback, import "C" need to be added, even if we don't use cgo.