通过在Go中调用Windows DLL发送ARP请求不起作用

Question

I'm trying to call a Windows API SendARP from Go to send arp request on Windows, but it always returns 1168, AKA ERROR_NOT_FOUND, description by MSDN on this error code:

Element not found. This error is returned on Windows Vista if the the SrcIp parameter does not specify a source IPv4 address on an interface on the local computer or the INADDR_ANY IP address (an IPv4 address of 0.0.0.0).

but I'm on Windows 7, moreover I do specify a right source IPv4 address. And I see no ARP packet sent in Wireshark. So where is the problem?

package main

import (
    "fmt"
    "syscall"
    "net"
    "unsafe"
)

var (
    iphlp, _   = syscall.LoadLibrary("iphlpapi.dll")
    SendARP, _ = syscall.GetProcAddress(iphlp, "SendARP")
)

func sendARP(src, dst net.IP) {
    //var nargs uintptr = 4
    var len uint = 6
    mac := []byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}
    ret, _, callErr := syscall.Syscall6(
    uintptr(SendARP), 4,
    uintptr(unsafe.Pointer(&dst[0])),
    uintptr(unsafe.Pointer(&src[0])),
    uintptr(unsafe.Pointer(&mac[0])),
    uintptr(unsafe.Pointer(&len)),
    0,
    0)

    if callErr == 0 {
        fmt.Printf("result %v
", int(ret))
    }
}

func main() {
    defer syscall.FreeLibrary(iphlp)

    fmt.Printf("addr: %v
", sendARP)

    dst := net.IPv4(192,168,1,1)
    src := net.IPv4(192,168,1,103)
    sendARP(src, dst)   
}

Answer 1

Please, try this

package main

import (
    "fmt"
    "log"
    "net"
    "syscall"
    "unsafe"
)

var SendARP = syscall.MustLoadDLL("iphlpapi.dll").MustFindProc("SendARP")

func ip4ToUint32(ip net.IP) (uint32, error) {
    ip = ip.To4()
    if ip == nil {
        return 0, fmt.Errorf("ip address %v is not ip4", ip)
    }
    var ret uint32
    for i := 4; i > 0; i-- {
        ret <<= 8
        ret += uint32(ip[i-1])
    }
    return ret, nil
}

func sendARP(ip net.IP) (net.HardwareAddr, error) {
    dst, err := ip4ToUint32(ip)
    if err != nil {
        return nil, err
    }
    mac := []byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}
    n := uint32(len(mac))
    ret, _, _ := SendARP.Call(
        uintptr(dst),
        0,
        uintptr(unsafe.Pointer(&mac[0])),
        uintptr(unsafe.Pointer(&n)))
    if ret != 0 {
        return nil, syscall.Errno(ret)
    }
    return mac, nil
}
func main() {
    ip := net.IPv4(192, 168, 1, 1)
    mac, err := sendARP(ip)
    if err != nil {
        log.Fatalf("could not find MAC for %q: %v", ip, err)
    }
    fmt.Printf("MAC address for %v is %v
", ip, mac)
}

it works for me.

Alex