getDNSInfo.go

getDNSInfo.go

// +build windows

package main

import (
	"bytes"
	"fmt"
	"syscall"
	"unsafe"
)

const (
	MAX_HOSTNAME_LEN    = 128
	MAX_DOMAIN_NAME_LEN = 128
	MAX_SCOPE_ID_LEN    = 256
)

// https://docs.microsoft.com/en-us/windows/win32/api/iptypes/ns-iptypes-ip_addr_string
type ipAddressString struct {
	next    *ipAddressString
	address [16]byte
	mask    [16]byte
	context uint32
}

// https://docs.microsoft.com/en-us/windows/win32/api/iptypes/ns-iptypes-fixed_info_w2ksp1
type fixedInfo struct {
	hostName         [MAX_HOSTNAME_LEN + 4]byte
	domainName       [MAX_DOMAIN_NAME_LEN + 4]byte
	currentDNSServer *ipAddressString
	dnsServerList    ipAddressString
	nodeType         uint16
	scopeID          [MAX_SCOPE_ID_LEN + 4]byte
	enableRouting    uint16
	enableProxy      uint16
	enableDNS        uint16
}

var (
	getNetworkParams = syscall.NewLazyDLL("Iphlpapi.dll").NewProc("GetNetworkParams")
)

func p(desc string, obj []byte) {
	fmt.Println(desc, ":", sliceToString(obj))
}

func sliceToString(slice []byte) string {
	n := bytes.IndexByte(slice, 0)
	return string(slice[:n])
}

func getDNSInfo() {
	err := getNetworkParams.Find()
	if err != nil {
		fmt.Println("err:", err)
		return
	}

	netInfo := [2]fixedInfo{}
	size := unsafe.Sizeof(netInfo)

	result, _, err := getNetworkParams.Call(uintptr(unsafe.Pointer(&netInfo[0])), uintptr(unsafe.Pointer(&size)))
	if result != 0 {
		fmt.Println("err:", err)
		return
	}

	fmt.Printf("raw: %T %v\n\n", netInfo[0], netInfo[0])

	p("hostName    ", netInfo[0].hostName[:])
	p("domainName  ", netInfo[0].domainName[:])
	p("dns1 address", netInfo[0].dnsServerList.address[:])
	p("dns1 netmask", netInfo[0].dnsServerList.mask[:])
	fmt.Println("dns1 context :", netInfo[0].dnsServerList.context)

	nextDNS := netInfo[0].dnsServerList.next
	if nextDNS != nil {
		p("dns2 address", nextDNS.address[:])
	}
}

func main() {
	getDNSInfo()
}