RTM_ROUTE_INFO

using System;
using System.Runtime.InteropServices;

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct RTM_PREF_INFO
{
    public uint Metric;
    public uint Preference;
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct RTM_NEXTHOP_LIST
{
    public ushort NumNextHops;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 1)] public IntPtr[] NextHops;
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct RTM_ROUTE_INFO
{
    public IntPtr DestHandle;
    public IntPtr RouteOwner;
    public IntPtr Neighbour;
    public byte State;
    public byte Flags1;
    public ushort Flags;
    public RTM_PREF_INFO PrefInfo;
    public uint BelongsToViews;
    public IntPtr EntitySpecificInfo;
    public RTM_NEXTHOP_LIST NextHopsList;
}

Imports System.Runtime.InteropServices

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Unicode)>
Public Structure RTM_PREF_INFO
    Public Metric As UInteger
    Public Preference As UInteger
End Structure

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Unicode)>
Public Structure RTM_NEXTHOP_LIST
    Public NumNextHops As UShort
    <MarshalAs(UnmanagedType.ByValArray, SizeConst:=1)> Public NextHops() As IntPtr
End Structure

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Unicode)>
Public Structure RTM_ROUTE_INFO
    Public DestHandle As IntPtr
    Public RouteOwner As IntPtr
    Public Neighbour As IntPtr
    Public State As Byte
    Public Flags1 As Byte
    Public Flags As UShort
    Public PrefInfo As RTM_PREF_INFO
    Public BelongsToViews As UInteger
    Public EntitySpecificInfo As IntPtr
    Public NextHopsList As RTM_NEXTHOP_LIST
End Structure

import ctypes
from ctypes import wintypes

class RTM_PREF_INFO(ctypes.Structure):
    _fields_ = [
        ("Metric", wintypes.DWORD),
        ("Preference", wintypes.DWORD),
    ]

class RTM_NEXTHOP_LIST(ctypes.Structure):
    _fields_ = [
        ("NumNextHops", ctypes.c_ushort),
        ("NextHops", ctypes.c_ssize_t * 1),
    ]

class RTM_ROUTE_INFO(ctypes.Structure):
    _fields_ = [
        ("DestHandle", ctypes.c_ssize_t),
        ("RouteOwner", ctypes.c_ssize_t),
        ("Neighbour", ctypes.c_ssize_t),
        ("State", ctypes.c_ubyte),
        ("Flags1", ctypes.c_ubyte),
        ("Flags", ctypes.c_ushort),
        ("PrefInfo", RTM_PREF_INFO),
        ("BelongsToViews", wintypes.DWORD),
        ("EntitySpecificInfo", ctypes.c_void_p),
        ("NextHopsList", RTM_NEXTHOP_LIST),
    ]

#[repr(C)]
pub struct RTM_PREF_INFO {
    pub Metric: u32,
    pub Preference: u32,
}

#[repr(C)]
pub struct RTM_NEXTHOP_LIST {
    pub NumNextHops: u16,
    pub NextHops: [isize; 1],
}

#[repr(C)]
pub struct RTM_ROUTE_INFO {
    pub DestHandle: isize,
    pub RouteOwner: isize,
    pub Neighbour: isize,
    pub State: u8,
    pub Flags1: u8,
    pub Flags: u16,
    pub PrefInfo: RTM_PREF_INFO,
    pub BelongsToViews: u32,
    pub EntitySpecificInfo: *mut core::ffi::c_void,
    pub NextHopsList: RTM_NEXTHOP_LIST,
}

import "golang.org/x/sys/windows"

type RTM_PREF_INFO struct {
	Metric uint32
	Preference uint32
}

type RTM_NEXTHOP_LIST struct {
	NumNextHops uint16
	NextHops [1]uintptr
}

type RTM_ROUTE_INFO struct {
	DestHandle uintptr
	RouteOwner uintptr
	Neighbour uintptr
	State byte
	Flags1 byte
	Flags uint16
	PrefInfo RTM_PREF_INFO
	BelongsToViews uint32
	EntitySpecificInfo uintptr
	NextHopsList RTM_NEXTHOP_LIST
}

type
  RTM_PREF_INFO = record
    Metric: DWORD;
    Preference: DWORD;
  end;

  RTM_NEXTHOP_LIST = record
    NumNextHops: Word;
    NextHops: array[0..0] of NativeInt;
  end;

  RTM_ROUTE_INFO = record
    DestHandle: NativeInt;
    RouteOwner: NativeInt;
    Neighbour: NativeInt;
    State: Byte;
    Flags1: Byte;
    Flags: Word;
    PrefInfo: RTM_PREF_INFO;
    BelongsToViews: DWORD;
    EntitySpecificInfo: Pointer;
    NextHopsList: RTM_NEXTHOP_LIST;
  end;

const RTM_PREF_INFO = extern struct {
    Metric: u32,
    Preference: u32,
};

const RTM_NEXTHOP_LIST = extern struct {
    NumNextHops: u16,
    NextHops: [1]isize,
};

const RTM_ROUTE_INFO = extern struct {
    DestHandle: isize,
    RouteOwner: isize,
    Neighbour: isize,
    State: u8,
    Flags1: u8,
    Flags: u16,
    PrefInfo: RTM_PREF_INFO,
    BelongsToViews: u32,
    EntitySpecificInfo: ?*anyopaque,
    NextHopsList: RTM_NEXTHOP_LIST,
};

type
  RTM_PREF_INFO {.bycopy.} = object
    Metric: uint32
    Preference: uint32

  RTM_NEXTHOP_LIST {.bycopy.} = object
    NumNextHops: uint16
    NextHops: array[1, int]

  RTM_ROUTE_INFO {.bycopy.} = object
    DestHandle: int
    RouteOwner: int
    Neighbour: int
    State: uint8
    Flags1: uint8
    Flags: uint16
    PrefInfo: RTM_PREF_INFO
    BelongsToViews: uint32
    EntitySpecificInfo: pointer
    NextHopsList: RTM_NEXTHOP_LIST

struct RTM_PREF_INFO
{
    uint Metric;
    uint Preference;
}

struct RTM_NEXTHOP_LIST
{
    ushort NumNextHops;
    ptrdiff_t[1] NextHops;
}

struct RTM_ROUTE_INFO
{
    ptrdiff_t DestHandle;
    ptrdiff_t RouteOwner;
    ptrdiff_t Neighbour;
    ubyte State;
    ubyte Flags1;
    ushort Flags;
    RTM_PREF_INFO PrefInfo;
    uint BelongsToViews;
    void* EntitySpecificInfo;
    RTM_NEXTHOP_LIST NextHopsList;
}