Get Internet connected Interface information - Visual C++

get_internet_connected_inferface_info.cc

#include <winsock2.h>
#include <iphlpapi.h>
#include <stdio.h>
#include <stdlib.h>
#pragma comment(lib, "IPHLPAPI.lib")

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

int __cdecl main() {

	PIP_ADAPTER_INFO pAdapterInfo;
	PIP_ADAPTER_INFO pAdapter = NULL;
	DWORD dwRetVal = 0;
	UINT i;

	struct tm newtime;
	char buffer[32];
	errno_t error;

	unsigned long  ifIndex_;

	if (GetBestInterface(0, &ifIndex_) != NO_ERROR) {
		ifIndex_ = -1;
	}

	ULONG ulOutBufLen = sizeof(IP_ADAPTER_INFO);
	pAdapterInfo = (IP_ADAPTER_INFO *) MALLOC(sizeof(IP_ADAPTER_INFO));
	if (pAdapterInfo == NULL) {
		return NULL;
	}

	if (GetAdaptersInfo(pAdapterInfo, &ulOutBufLen) == ERROR_BUFFER_OVERFLOW) {
		FREE(pAdapterInfo);
		pAdapterInfo = (IP_ADAPTER_INFO *) MALLOC(ulOutBufLen);
		if (pAdapterInfo == NULL) {
			return NULL;
		}
	}
	ifIndex_ = -1;

	if ((dwRetVal = GetAdaptersInfo(pAdapterInfo, &ulOutBufLen)) == NO_ERROR) {
		pAdapter = pAdapterInfo;
		while (pAdapter) {
			if (
				(ifIndex_ == -1 && pAdapter->Type != MIB_IF_TYPE_ETHERNET) && // when no best interface and ethernet
				ifIndex_ != pAdapter->Index // when there is best interface
			) {
				pAdapter = pAdapter->Next;
				continue;
			}
			
			printf("\tAdapter Name: \t%s\n", pAdapter->AdapterName);
			printf("\tAdapter Desc: \t%s\n", pAdapter->Description);
			printf("\tAdapter Addr: \t");
			for (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("\tIP Address: \t%s\n",
				pAdapter->IpAddressList.IpAddress.String);
			printf("\tIP Mask: \t%s\n", pAdapter->IpAddressList.IpMask.String);

			printf("\tGateway: \t%s\n", pAdapter->GatewayList.IpAddress.String);
			printf("\t***\n");

			pAdapter = pAdapter->Next;
			printf("\n");
			break;
		}
	}
	if (pAdapterInfo)
		FREE(pAdapterInfo);

	return 0;
}

// GetBestInterface 
// https://msdn.microsoft.com/ko-kr/library/windows/desktop/aa365920(v=vs.85).aspx

// GetAdaptersInfo
// https://msdn.microsoft.com/en-us/library/windows/desktop/aa365917(v=vs.85).aspx