Return all Windows routes (IPv4 only) from iphlpapi

def GetIpForwardTable():
    """Return all Windows routes (IPv4 only) from iphlpapi"""
    # We get the size first
    size = ULONG()
    res = _GetIpForwardTable(None, byref(size), False)
    if res != 0x7a:  # ERROR_INSUFFICIENT_BUFFER -> populate size
        raise RuntimeError("Error getting structure length (%d)" % res)
    # Now let's build our buffer
    pointer_type = PMIB_IPFORWARDTABLE
    buffer = create_string_buffer(size.value)
    pIpForwardTable = ctypes.cast(buffer, pointer_type)
    # And call GetAdaptersAddresses
    res = _GetIpForwardTable(pIpForwardTable, byref(size), True)
    if res != NO_ERROR:
        raise RuntimeError("Error retrieving table (%d)" % res)
    results = []
    for i in range(pIpForwardTable.contents.NumEntries):
        results.append(_struct_to_dict(pIpForwardTable.contents.Table[i]))
    del(pIpForwardTable)
    return results