GetAdaptersAddresses function (iphlpapi.h)

The GetAdaptersAddresses function retrieves the addresses associated with the adapters on the local computer.

Syntax

IPHLPAPI_DLL_LINKAGE ULONG GetAdaptersAddresses(
  [in]      ULONG                 Family,
  [in]      ULONG                 Flags,
  [in]      PVOID                 Reserved,
  [in, out] PIP_ADAPTER_ADDRESSES AdapterAddresses,
  [in, out] PULONG                SizePointer
);

Parameters

[in] Family

The address family of the addresses to retrieve. This parameter must be one of the following values.

[in] Flags

The type of addresses to retrieve. The possible values are defined in the Iptypes.h header file. Note that the Iptypes.h header file is automatically included in Iphlpapi.h, and should never be used directly.

This parameter is a combination of the following values. If this parameter is zero, then unicast, anycast, and multicast IP addresses will be returned.

[in] Reserved

This parameter is not currently used, but is reserved for future system use. The calling application should pass NULL for this parameter.

[in, out] AdapterAddresses

A pointer to a buffer that contains a linked list of IP_ADAPTER_ADDRESSES structures on successful return.

[in, out] SizePointer

A pointer to a variable that specifies the size of the buffer pointed to by AdapterAddresses.

Return value

If the function succeeds, the return value is ERROR_SUCCESS (defined to the same value as NO_ERROR).

If the function fails, the return value is one of the following error codes.

Remarks

The
GetAdaptersAddresses function can retrieve information for IPv4 and IPv6 addresses.

Addresses are returned as a linked list of IP_ADAPTER_ADDRESSES structures in the buffer pointed to by the AdapterAddresses parameter. The application that calls the GetAdaptersAddresses function must allocate the amount of memory needed to return the IP_ADAPTER_ADDRESSES structures pointed to by the AdapterAddresses parameter. When these returned structures are no longer required, the application should free the memory allocated. This can be accomplished by calling the HeapAlloc function to allocate memory and later calling the HeapFree function to free the allocated memory, as shown in the example code. Other memory allocation and free functions can be used as long as the same family of functions are used for both the allocation and the free function.

GetAdaptersAddresses is implemented only as a synchronous function call. The GetAdaptersAddresses function requires a significant amount of network resources and time to complete since all of the low-level network interface tables must be traversed.

One method that can be used to determine the memory needed to return the IP_ADAPTER_ADDRESSES structures pointed to by the AdapterAddresses parameter is to pass too small a buffer size as indicated in the SizePointer parameter in the first call to the GetAdaptersAddresses function, so the function will fail with ERROR_BUFFER_OVERFLOW. When the return value is ERROR_BUFFER_OVERFLOW, the SizePointer parameter returned points to the required size of the buffer to hold the adapter information. Note that it is possible for the buffer size required for the IP_ADAPTER_ADDRESSES structures pointed to by the AdapterAddresses parameter to change between subsequent calls to the GetAdaptersAddresses function if an adapter address is added or removed. However, this method of using the GetAdaptersAddresses function is strongly discouraged. This method requires calling the GetAdaptersAddresses function multiple times.

The recommended method of calling the GetAdaptersAddresses function is to pre-allocate a 15KB working buffer pointed to by the AdapterAddresses parameter. On typical computers, this dramatically reduces the chances that the GetAdaptersAddresses function returns ERROR_BUFFER_OVERFLOW, which would require calling GetAdaptersAddresses function multiple times. The example code illustrates this method of use.

In versions prior to Windows 10, the order in which adapters appear in the list returned by this function can be controlled from the Network Connections folder: select the Advanced Settings menu item from the Advanced menu. Starting with Windows 10, the order in which adapters appear in the list is determined by the IPv4 or IPv6 route metric.

If the GAA_FLAG_INCLUDE_ALL_INTERFACES is set, then all NDIS adapters will be retrieved even those addresses associated with adapters not bound to an address family specified in the Family parameter. When this flag is not set, then only the addresses that are bound to an adapter enabled for the address family specified in the Family parameter are returned.

The size of the IP_ADAPTER_ADDRESSES structure was changed on Windows XP with Service Pack 1 (SP1) and later. Several additional members were added to this structure. The size of the IP_ADAPTER_ADDRESSES structure was also changed on Windows Vista and later. A number of additional members were added to this structure. The size of the IP_ADAPTER_ADDRESSES structure also changed on Windows Vista with Service Pack 1 (SP1)and later and onWindows Server 2008 and later. One additional member was added to this structure. The Length member of the IP_ADAPTER_ADDRESSES structure returned in the linked list of structures in the buffer pointed to by the AdapterAddresses parameter should be used to determine which version of the IP_ADAPTER_ADDRESSES structure is being used.

The GetIpAddrTable function retrieves the interface–to–IPv4 address mapping table on a local computer and returns this information in an MIB_IPADDRTABLE structure.

On the Platform Software Development Kit (SDK) released for Windows Server 2003 and earlier, the return value for the GetAdaptersAddresses function was defined as a DWORD, rather than a ULONG.

The SOCKET_ADDRESS structure is used in the IP_ADAPTER_ADDRESSES structure pointed to by the AdapterAddresses parameter. On the Microsoft Windows Software Development Kit (SDK) released for Windows Vista and later, the organization of header files has changed and the SOCKET_ADDRESS structure is defined in the Ws2def.h header file which is automatically included by the Winsock2.h header file. On the Platform SDK released for Windows Server 2003 and Windows XP, the SOCKET_ADDRESS structure is declared in the Winsock2.h header file. In order to use the IP_ADAPTER_ADDRESSES structure, the Winsock2.h header file must be included before the Iphlpapi.h header file.

Examples

This example retrieves the IP_ADAPTER_ADDRESSES structure for the adapters associated with the system and prints some members for each adapter interface.

#include <winsock2.h>
#include <iphlpapi.h>
#include <stdio.h>
#include <stdlib.h>

// Link with Iphlpapi.lib
#pragma comment(lib, "IPHLPAPI.lib")

#define WORKING_BUFFER_SIZE 15000
#define MAX_TRIES 3

#define MALLOC(x) HeapAlloc(GetProcessHeap(), 0, (x))
#define FREE(x) HeapFree(GetProcessHeap(), 0, (x))

/* Note: could also use malloc() and free() */

int __cdecl main(int argc, char **argv)
{

    /* Declare and initialize variables */

    DWORD dwRetVal = 0;

    unsigned int i = 0;

    // Set the flags to pass to GetAdaptersAddresses
    ULONG flags = GAA_FLAG_INCLUDE_PREFIX;

    // default to unspecified address family (both)
    ULONG family = AF_UNSPEC;

    LPVOID lpMsgBuf = NULL;

    PIP_ADAPTER_ADDRESSES pAddresses = NULL;
    ULONG outBufLen = 0;
    ULONG Iterations = 0;

    PIP_ADAPTER_ADDRESSES pCurrAddresses = NULL;
    PIP_ADAPTER_UNICAST_ADDRESS pUnicast = NULL;
    PIP_ADAPTER_ANYCAST_ADDRESS pAnycast = NULL;
    PIP_ADAPTER_MULTICAST_ADDRESS pMulticast = NULL;
    IP_ADAPTER_DNS_SERVER_ADDRESS *pDnServer = NULL;
    IP_ADAPTER_PREFIX *pPrefix = NULL;

    if (argc != 2) {
        printf(" Usage: getadapteraddresses family\n");
        printf("        getadapteraddresses 4 (for IPv4)\n");
        printf("        getadapteraddresses 6 (for IPv6)\n");
        printf("        getadapteraddresses A (for both IPv4 and IPv6)\n");
        exit(1);
    }

    if (atoi(argv[1]) == 4)
        family = AF_INET;
    else if (atoi(argv[1]) == 6)
        family = AF_INET6;

    printf("Calling GetAdaptersAddresses function with family = ");
    if (family == AF_INET)
        printf("AF_INET\n");
    if (family == AF_INET6)
        printf("AF_INET6\n");
    if (family == AF_UNSPEC)
        printf("AF_UNSPEC\n\n");

    // Allocate a 15 KB buffer to start with.
    outBufLen = WORKING_BUFFER_SIZE;

    do {

        pAddresses = (IP_ADAPTER_ADDRESSES *) MALLOC(outBufLen);
        if (pAddresses == NULL) {
            printf
                ("Memory allocation failed for IP_ADAPTER_ADDRESSES struct\n");
            exit(1);
        }

        dwRetVal =
            GetAdaptersAddresses(family, flags, NULL, pAddresses, &outBufLen);

        if (dwRetVal == ERROR_BUFFER_OVERFLOW) {
            FREE(pAddresses);
            pAddresses = NULL;
        } else {
            break;
        }

        Iterations++;

    } while ((dwRetVal == ERROR_BUFFER_OVERFLOW) && (Iterations < MAX_TRIES));

    if (dwRetVal == NO_ERROR) {
        // If successful, output some information from the data we received
        pCurrAddresses = pAddresses;
        while (pCurrAddresses) {
            printf("\tLength of the IP_ADAPTER_ADDRESS struct: %ld\n",
                   pCurrAddresses->Length);
            printf("\tIfIndex (IPv4 interface): %u\n", pCurrAddresses->IfIndex);
            printf("\tAdapter name: %s\n", pCurrAddresses->AdapterName);

            pUnicast = pCurrAddresses->FirstUnicastAddress;
            if (pUnicast != NULL) {
                for (i = 0; pUnicast != NULL; i++)
                    pUnicast = pUnicast->Next;
                printf("\tNumber of Unicast Addresses: %d\n", i);
            } else
                printf("\tNo Unicast Addresses\n");

            pAnycast = pCurrAddresses->FirstAnycastAddress;
            if (pAnycast) {
                for (i = 0; pAnycast != NULL; i++)
                    pAnycast = pAnycast->Next;
                printf("\tNumber of Anycast Addresses: %d\n", i);
            } else
                printf("\tNo Anycast Addresses\n");

            pMulticast = pCurrAddresses->FirstMulticastAddress;
            if (pMulticast) {
                for (i = 0; pMulticast != NULL; i++)
                    pMulticast = pMulticast->Next;
                printf("\tNumber of Multicast Addresses: %d\n", i);
            } else
                printf("\tNo Multicast Addresses\n");

            pDnServer = pCurrAddresses->FirstDnsServerAddress;
            if (pDnServer) {
                for (i = 0; pDnServer != NULL; i++)
                    pDnServer = pDnServer->Next;
                printf("\tNumber of DNS Server Addresses: %d\n", i);
            } else
                printf("\tNo DNS Server Addresses\n");

            printf("\tDNS Suffix: %wS\n", pCurrAddresses->DnsSuffix);
            printf("\tDescription: %wS\n", pCurrAddresses->Description);
            printf("\tFriendly name: %wS\n", pCurrAddresses->FriendlyName);

            if (pCurrAddresses->PhysicalAddressLength != 0) {
                printf("\tPhysical address: ");
                for (i = 0; i < (int) pCurrAddresses->PhysicalAddressLength;
                     i++) {
                    if (i == (pCurrAddresses->PhysicalAddressLength - 1))
                        printf("%.2X\n",
                               (int) pCurrAddresses->PhysicalAddress[i]);
                    else
                        printf("%.2X-",
                               (int) pCurrAddresses->PhysicalAddress[i]);
                }
            }
            printf("\tFlags: %ld\n", pCurrAddresses->Flags);
            printf("\tMtu: %lu\n", pCurrAddresses->Mtu);
            printf("\tIfType: %ld\n", pCurrAddresses->IfType);
            printf("\tOperStatus: %ld\n", pCurrAddresses->OperStatus);
            printf("\tIpv6IfIndex (IPv6 interface): %u\n",
                   pCurrAddresses->Ipv6IfIndex);
            printf("\tZoneIndices (hex): ");
            for (i = 0; i < 16; i++)
                printf("%lx ", pCurrAddresses->ZoneIndices[i]);
            printf("\n");

            printf("\tTransmit link speed: %I64u\n", pCurrAddresses->TransmitLinkSpeed);
            printf("\tReceive link speed: %I64u\n", pCurrAddresses->ReceiveLinkSpeed);

            pPrefix = pCurrAddresses->FirstPrefix;
            if (pPrefix) {
                for (i = 0; pPrefix != NULL; i++)
                    pPrefix = pPrefix->Next;
                printf("\tNumber of IP Adapter Prefix entries: %d\n", i);
            } else
                printf("\tNumber of IP Adapter Prefix entries: 0\n");

            printf("\n");

            pCurrAddresses = pCurrAddresses->Next;
        }
    } else {
        printf("Call to GetAdaptersAddresses failed with error: %d\n",
               dwRetVal);
        if (dwRetVal == ERROR_NO_DATA)
            printf("\tNo addresses were found for the requested parameters\n");
        else {

            if (FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
                    FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, 
                    NULL, dwRetVal, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),   
                    // Default language
                    (LPTSTR) & lpMsgBuf, 0, NULL)) {
                printf("\tError: %s", lpMsgBuf);
                LocalFree(lpMsgBuf);
                if (pAddresses)
                    FREE(pAddresses);
                exit(1);
            }
        }
    }

    if (pAddresses) {
        FREE(pAddresses);
    }

    return 0;
}

Requirements

See also

GetIpAddrTable

HeapAlloc

HeapFree

IP Helper Function Reference

IP Helper Start Page

IP_ADAPTER_ADDRESSES

MIB_IPADDRTABLE

SOCKET_ADDRESS

Windows Sockets