GetAdaptersInfo

Retrieves detailed information about network adapters installed on the local computer.

Syntax


ULONG GetAdaptersInfo(
  IP_ADAPTER_INFO *pAdapterInfo,
  PULONG          Size
);

Parameters

pAdapterInfo: A pointer to a buffer that receives a IP_ADAPTER_INFO structure. The structure contains information about the adapters. If the buffer is not large enough, the function returns ERROR_BUFFER_OVERFLOW and the value of the Size parameter is updated to the required buffer size.
Size: A pointer to a ULONG variable that specifies the size, in bytes, of the buffer pointed to by pAdapterInfo.

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:

Return Code	Description
`ERROR_BUFFER_OVERFLOW`	The buffer provided is not large enough to hold the adapter information. The `Size` parameter is updated with the required size.
`ERROR_INVALID_PARAMETER`	One or more of the parameters are invalid.
`ERROR_NOT_SUPPORTED`	This function is not supported on the operating system.

Remarks

The GetAdaptersInfo function retrieves information about network adapters, including their IP addresses, MAC addresses, subnet masks, default gateways, and DHCP information.

The function populates a linked list of IP_ADAPTER_INFO structures. Each structure describes a network adapter.

It is recommended to call GetAdaptersInfo twice. The first call should be with a NULL pointer for pAdapterInfo to get the required buffer size. The second call uses the allocated buffer size to retrieve the actual adapter information.

Example


#include <windows.h>
#include <iphlpapi.h>
#include <stdio.h>

#pragma comment(lib, "iphlpapi.lib")

int main() {
    ULONG ulOutBufLen = sizeof(IP_ADAPTER_INFO);
    IP_ADAPTER_INFO *pAdapterInfo = NULL;
    IP_ADAPTER_INFO *pAdapter = NULL;
    DWORD dwRetVal = 0;

    pAdapterInfo = (IP_ADAPTER_INFO *) malloc(sizeof(IP_ADAPTER_INFO));
    if (pAdapterInfo == NULL) {
        printf("Error allocating memory for IP_ADAPTER_INFO\n");
        return 1;
    }

    if (GetAdaptersInfo(pAdapterInfo, &ulOutBufLen) == ERROR_BUFFER_OVERFLOW) {
        free(pAdapterInfo);
        pAdapterInfo = (IP_ADAPTER_INFO *) malloc(ulOutBufLen);
        if (pAdapterInfo == NULL) {
            printf("Error allocating memory for IP_ADAPTER_INFO (resized)\n");
            return 1;
        }
    }

    dwRetVal = GetAdaptersInfo(pAdapterInfo, &ulOutBufLen);

    if (dwRetVal == NO_ERROR) {
        pAdapter = pAdapterInfo;
        while (pAdapter) {
            printf("Adapter Name: %s\n", pAdapter->AdapterName);
            printf("  Description: %s\n", pAdapter->Description);
            printf("  IP Address: %s\n", pAdapter->IpAddressList.IpAddress.String);
            printf("  Subnet Mask: %s\n", pAdapter->IpAddressList.IpMask.String);
            if (pAdapter->GatewayList) {
                printf("  Default Gateway: %s\n", pAdapter->GatewayList->IpAddress.String);
            }
            printf("  MAC Address: ");
            for (int i = 0; i < pAdapter->PhysicalAddressLength; i++) {
                if (i == pAdapter->PhysicalAddressLength - 1)
                    printf("%.2X\n", pAdapter->PhysicalAddress[i]);
                else
                    printf("%.2X-", pAdapter->PhysicalAddress[i]);
            }
            printf("\n");
            pAdapter = pAdapter->Next;
        }
    } else {
        printf("GetAdaptersInfo failed with error: %d\n", dwRetVal);
    }

    if (pAdapterInfo) {
        free(pAdapterInfo);
    }

    return 0;
}

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