Managing Network Adapters Using GetAdaptersInfo

Article
01/07/2021

The GetAdaptersInfo function fills a pointer to an IP_ADAPTER_INFO structure with information about the network adapters associated with the system.

To use GetAdaptersInfo

Declare a pointer to an IP_ADAPTER_INFO variable called pAdapterInfo, and a ULONG variable called ulOutBufLen. These variables are passed as parameters to the GetAdaptersInfo function. Also create a DWORD variable called dwRetVal (for error checking).
```
IP_ADAPTER_INFO  *pAdapterInfo;
ULONG            ulOutBufLen;
DWORD            dwRetVal;
```

Allocate memory for the structures.

pAdapterInfo = (IP_ADAPTER_INFO *) malloc( sizeof(IP_ADAPTER_INFO) );
ulOutBufLen = sizeof(IP_ADAPTER_INFO);

Make an initial call to GetAdaptersInfo to get the size needed into the ulOutBufLen variable.

Note

This call to the function is meant to fail, and is used to ensure that the ulOutBufLen variable specifies a size sufficient for holding all the information returned to pAdapterInfo. This is a common programming model for data structures and functions of this type.
```
if (GetAdaptersInfo( pAdapterInfo, &ulOutBufLen) != ERROR_SUCCESS) {
    free (pAdapterInfo);
    pAdapterInfo = (IP_ADAPTER_INFO *) malloc ( ulOutBufLen );
}
```
Make a second call to GetAdaptersInfo, passing pAdapterInfo and ulOutBufLen as parameters and doing general error checking. Return its value to the DWORD variable dwRetVal (for more extensive error checking).
```
if ((dwRetVal = GetAdaptersInfo( pAdapterInfo, &ulOutBufLen)) != ERROR_SUCCESS) {
    printf("GetAdaptersInfo call failed with %d\n", dwRetVal);
}
```

If the call was successful, access some of the data in the pAdapterInfo structure.

PIP_ADAPTER_INFO pAdapter = pAdapterInfo;
while (pAdapter) {
    printf("Adapter Name: %s\n", pAdapter->AdapterName);
    printf("Adapter Desc: %s\n", pAdapter->Description);
    printf("\tAdapter Addr: \t");
    for (UINT i = 0; i < pAdapter->AddressLength; i++) {
        if (i == (pAdapter->AddressLength - 1))
            printf("%.2X\n",(int)pAdapter->Address[i]);
        else
            printf("%.2X-",(int)pAdapter->Address[i]);
    }
    printf("IP Address: %s\n", pAdapter->IpAddressList.IpAddress.String);
    printf("IP Mask: %s\n", pAdapter->IpAddressList.IpMask.String);
    printf("\tGateway: \t%s\n", pAdapter->GatewayList.IpAddress.String);
    printf("\t***\n");
    if (pAdapter->DhcpEnabled) {
        printf("\tDHCP Enabled: Yes\n");
        printf("\t\tDHCP Server: \t%s\n", pAdapter->DhcpServer.IpAddress.String);
    }
    else
      printf("\tDHCP Enabled: No\n");

  pAdapter = pAdapter->Next;
}

Free any memory allocated for the pAdapterInfo structure.
```
if (pAdapterInfo)
        free(pAdapterInfo);
```

Next Step: Managing Interfaces Using GetInterfaceInfo

Previous Step: Retrieving Information Using GetNetworkParams

Share via

Managing Network Adapters Using GetAdaptersInfo

Feedback

Additional resources