get-dns-namespaces.py

import ctypes  
import ctypes.wintypes as wintypes  
  
# Load the IP Helper library  
IPHLPAPI = ctypes.WinDLL('Iphlpapi.dll')  
  
# Based on the following documentation:
# https://learn.microsoft.com/en-us/windows/win32/api/iphlpapi/nf-iphlpapi-getadaptersaddresses
# https://learn.microsoft.com/en-us/windows/win32/api/iptypes/ns-iptypes-ip_adapter_addresses_lh
# https://learn.microsoft.com/en-us/windows/win32/api/iptypes/ns-iptypes-ip_adapter_dns_server_address_xp
# https://learn.microsoft.com/en-us/windows/win32/debug/system-error-codes--0-499-

# Constants  
AF_UNSPEC = 0  
ERROR_SUCCESS = 0  
GAA_FLAG_INCLUDE_PREFIX = 0x00000010  
AF_INET = 2  
AF_INET6 = 23  
IF_TYPE_SOFTWARE_LOOPBACK = 24  
  
# Define necessary structures  
class SOCKADDR(ctypes.Structure):  
    _fields_ = [  
        ("sa_family", wintypes.USHORT),  
        ("sa_data", ctypes.c_ubyte * 14)  
    ]  
  
class SOCKET_ADDRESS(ctypes.Structure):  
    _fields_ = [  
        ("lpSockaddr", ctypes.POINTER(SOCKADDR)),  
        ("iSockaddrLength", wintypes.INT)  
    ]  
  
class IP_ADAPTER_DNS_SERVER_ADDRESS(ctypes.Structure):  
    pass  # Forward declaration  
  
IP_ADAPTER_DNS_SERVER_ADDRESS._fields_ = [  
    ("Length", wintypes.ULONG),  
    ("Reserved", wintypes.DWORD),  
    ("Next", ctypes.POINTER(IP_ADAPTER_DNS_SERVER_ADDRESS)),  
    ("Address", SOCKET_ADDRESS)  
]  
  
class IP_ADAPTER_ADDRESSES(ctypes.Structure):  
    pass  # Forward declaration  
  
IP_ADAPTER_ADDRESSES._fields_ = [  
    ("Length", wintypes.ULONG),  
    ("IfIndex", wintypes.DWORD),  
    ("Next", ctypes.POINTER(IP_ADAPTER_ADDRESSES)),  
    ("AdapterName", ctypes.c_char_p),  
    ("FirstUnicastAddress", ctypes.POINTER(SOCKET_ADDRESS)),  
    ("FirstAnycastAddress", ctypes.POINTER(SOCKET_ADDRESS)),  
    ("FirstMulticastAddress", ctypes.POINTER(SOCKET_ADDRESS)),  
    ("FirstDnsServerAddress", ctypes.POINTER(IP_ADAPTER_DNS_SERVER_ADDRESS)),  
    ("DnsSuffix", wintypes.LPWSTR),  
    ("Description", wintypes.LPWSTR),  
    ("FriendlyName", wintypes.LPWSTR),  
    ("PhysicalAddress", ctypes.c_ubyte * 8),  
    ("PhysicalAddressLength", wintypes.ULONG),  
    ("Flags", wintypes.ULONG),  
    ("Mtu", wintypes.ULONG),  
    ("IfType", wintypes.ULONG),  
    ("OperStatus", ctypes.c_uint), 
    # Remaining types removed for brevity.
]  
  
def format_ipv4(sockaddr_in):  
    return ".".join(map(str, sockaddr_in.sa_data[2:6]))  
  
def format_ipv6(sockaddr_in6):  
    parts = [sockaddr_in6.sa_data[i] << 8 | sockaddr_in6.sa_data[i+1] for i in range(0, 14, 2)]  
    return ":".join(f"{part:04x}" for part in parts)  
  
def get_dns_servers():  
    buffer_size = ctypes.c_ulong(15000)  
    while True:  
        buffer = ctypes.create_string_buffer(buffer_size.value)  
          
        ret_val = IPHLPAPI.GetAdaptersAddresses(  
            AF_UNSPEC, GAA_FLAG_INCLUDE_PREFIX, None, buffer, ctypes.byref(buffer_size)  
        )  
          
        if ret_val == ERROR_SUCCESS:  
            break  
        elif ret_val != 0x6F:  # ERROR_BUFFER_OVERFLOW  
            print(f"Error retrieving adapter information: {ret_val}")  
            return  
      
    adapter_addresses = ctypes.cast(buffer, ctypes.POINTER(IP_ADAPTER_ADDRESSES))  
      
    current_adapter = adapter_addresses  
    while current_adapter:  

        friendly_name = ctypes.wstring_at(current_adapter.contents.FriendlyName)  
        oper_status = current_adapter.contents.OperStatus  
        oper_status_str = "Operational" if oper_status == 1 else "Non-Operational"  
        print(f"Adapter: {friendly_name}, Status: {oper_status_str}")  

        # Exclude loopback adapters.
        if current_adapter.contents.IfType == IF_TYPE_SOFTWARE_LOOPBACK: 
            current_adapter = current_adapter.contents.Next  
            print("Skipping loopback adapter")
            continue

        current_dns_server = current_adapter.contents.FirstDnsServerAddress  
        while current_dns_server:  
            sockaddr = current_dns_server.contents.Address.lpSockaddr  
            sockaddr_family = sockaddr.contents.sa_family  
                
            ip = None  
            if sockaddr_family == AF_INET:  # IPv4  
                ip = format_ipv4(sockaddr.contents)  
            elif sockaddr_family == AF_INET6:  # IPv6  
                ip = format_ipv6(sockaddr.contents)  
                
            if ip:  
                print(f"DNS Server: {ip}")  
                
            current_dns_server = current_dns_server.contents.Next  
  
        current_adapter = current_adapter.contents.Next  
  
get_dns_servers()  

"""
Output:

Adapter: Ethernet 4, Status: Operational
DNS Server: 10.122.0.2
Adapter: Loopback Pseudo-Interface 1, Status: Operational
Skipping loopback adapter
"""