GetIfTable function (iphlpapi.h)

The GetIfTable function retrieves the MIB-II interface table.

Syntax

IPHLPAPI_DLL_LINKAGE DWORD GetIfTable(
  [out]     PMIB_IFTABLE pIfTable,
  [in, out] PULONG       pdwSize,
  [in]      BOOL         bOrder
);

Parameters

[out] pIfTable

A pointer to a buffer that receives the interface table as a MIB_IFTABLE structure.

[in, out] pdwSize

On input, specifies the size in bytes of the buffer pointed to by the pIfTable parameter.

On output, if the buffer is not large enough to hold the returned interface table, the function sets this parameter equal to the required buffer size in bytes.

[in] bOrder

A Boolean value that specifies whether the returned interface table should be sorted in ascending order by interface index. If this parameter is TRUE, the table is sorted.

Return value

If the function succeeds, the return value is NO_ERROR.

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

Remarks

The
GetIfTable function enumerates physical interfaces on a local system and returns this information in a MIB_IFTABLE structure. The physical interfaces include the software loopback interface.

The GetIfTable2 and GetIfTable2Ex functions available on Windows Vista and later are an enhanced version of the GetIfTable function that enumerate both the physical and logical interfaces on a local system. Logical interfaces include various WAN Miniport interfaces used for L2TP, PPTP, PPOE, and other tunnel encapsulations.

Interfaces are returned in a MIB_IFTABLE structure in the buffer pointed to by the pIfTable parameter. The MIB_IFTABLE structure contains an interface count and an array of MIB_IFROW structures for each interface.

Note that the returned MIB_IFTABLE structure pointed to by the pIfTable parameter may contain padding for alignment between the dwNumEntries member and the first MIB_IFROW array entry in the table member of the MIB_IFTABLE structure. Padding for alignment may also be present between the MIB_IFROW array entries. Any access to a MIB_IFROW array entry should assume padding may exist.

Examples

The following example retrieves the interface table and prints the number of entries in the table and some data on each entry.

#include <winsock2.h>
#include <ws2tcpip.h>
#pragma comment(lib, "IPHLPAPI.lib")

#include <iphlpapi.h>

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

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

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

int main()
{

    // Declare and initialize variables.

    DWORD dwSize = 0;
    DWORD dwRetVal = 0;

    unsigned int i, j;

    /* variables used for GetIfTable and GetIfEntry */
    MIB_IFTABLE *pIfTable;
    MIB_IFROW *pIfRow;

    // Allocate memory for our pointers.
    pIfTable = (MIB_IFTABLE *) MALLOC(sizeof (MIB_IFTABLE));
    if (pIfTable == NULL) {
        printf("Error allocating memory needed to call GetIfTable\n");
        return 1;
    }
    // Make an initial call to GetIfTable to get the
    // necessary size into dwSize
    dwSize = sizeof (MIB_IFTABLE);
    if (GetIfTable(pIfTable, &dwSize, FALSE) == ERROR_INSUFFICIENT_BUFFER) {
        FREE(pIfTable);
        pIfTable = (MIB_IFTABLE *) MALLOC(dwSize);
        if (pIfTable == NULL) {
            printf("Error allocating memory needed to call GetIfTable\n");
            return 1;
        }
    }
    // Make a second call to GetIfTable to get the actual
    // data we want.
    if ((dwRetVal = GetIfTable(pIfTable, &dwSize, FALSE)) == NO_ERROR) {
        printf("\tNum Entries: %ld\n\n", pIfTable->dwNumEntries);
        for (i = 0; i < pIfTable->dwNumEntries; i++) {
            pIfRow = (MIB_IFROW *) & pIfTable->table[i];
            printf("\tIndex[%d]:\t %ld\n", i, pIfRow->dwIndex);
            printf("\tInterfaceName[%d]:\t %ws", i, pIfRow->wszName);
            printf("\n");
            printf("\tDescription[%d]:\t ", i);
            for (j = 0; j < pIfRow->dwDescrLen; j++)
                printf("%c", pIfRow->bDescr[j]);
            printf("\n");
            printf("\tType[%d]:\t ", i);
            switch (pIfRow->dwType) {
            case IF_TYPE_OTHER:
                printf("Other\n");
                break;
            case IF_TYPE_ETHERNET_CSMACD:
                printf("Ethernet\n");
                break;
            case IF_TYPE_ISO88025_TOKENRING:
                printf("Token Ring\n");
                break;
            case IF_TYPE_PPP:
                printf("PPP\n");
                break;
            case IF_TYPE_SOFTWARE_LOOPBACK:
                printf("Software Lookback\n");
                break;
            case IF_TYPE_ATM:
                printf("ATM\n");
                break;
            case IF_TYPE_IEEE80211:
                printf("IEEE 802.11 Wireless\n");
                break;
            case IF_TYPE_TUNNEL:
                printf("Tunnel type encapsulation\n");
                break;
            case IF_TYPE_IEEE1394:
                printf("IEEE 1394 Firewire\n");
                break;
            default:
                printf("Unknown type %ld\n", pIfRow->dwType);
                break;
            }
            printf("\tMtu[%d]:\t\t %ld\n", i, pIfRow->dwMtu);
            printf("\tSpeed[%d]:\t %ld\n", i, pIfRow->dwSpeed);
            printf("\tPhysical Addr:\t ");
            if (pIfRow->dwPhysAddrLen == 0)
                printf("\n");
            for (j = 0; j < pIfRow->dwPhysAddrLen; j++) {
                if (j == (pIfRow->dwPhysAddrLen - 1))
                    printf("%.2X\n", (int) pIfRow->bPhysAddr[j]);
                else
                    printf("%.2X-", (int) pIfRow->bPhysAddr[j]);
            }
            printf("\tAdmin Status[%d]:\t %ld\n", i, pIfRow->dwAdminStatus);
            printf("\tOper Status[%d]:\t ", i);
            switch (pIfRow->dwOperStatus) {
            case IF_OPER_STATUS_NON_OPERATIONAL:
                printf("Non Operational\n");
                break;
            case IF_OPER_STATUS_UNREACHABLE:
                printf("Unreachable\n");
                break;
            case IF_OPER_STATUS_DISCONNECTED:
                printf("Disconnected\n");
                break;
            case IF_OPER_STATUS_CONNECTING:
                printf("Connecting\n");
                break;
            case IF_OPER_STATUS_CONNECTED:
                printf("Connected\n");
                break;
            case IF_OPER_STATUS_OPERATIONAL:
                printf("Operational\n");
                break;
            default:
                printf("Unknown status %ld\n", pIfRow->dwAdminStatus);
                break;
            }
            printf("\n");
        }
    } else {
        printf("GetIfTable failed with error: \n", dwRetVal);
        if (pIfTable != NULL) {
            FREE(pIfTable);
            pIfTable = NULL;
        }  
        return 1;
        // Here you can use FormatMessage to find out why 
        // it failed.
    }
    if (pIfTable != NULL) {
        FREE(pIfTable);
        pIfTable = NULL;
    }
    return 0;
}

Requirements

See also

GetIfEntry

GetIfEntry2

GetIfTable2

GetIfTable2Ex

GetNumberOfInterfaces

IP Helper Function Reference

MIB_IFROW

MIB_IFTABLE

MIB_IF_ROW2

MIB_IF_TABLE2