Find first mac address (windows)

get_first_mac_address_windows.cpp

#include "get_first_mac_address_windows.h"

#include <vector>

#include <WinSock2.h>
#include <ws2ipdef.h>
#include <WS2tcpip.h>
#include <iphlpapi.h>



std::optional<std::array<uint8_t, 6>> get_first_mac_address()
{
	const ULONG flags = 
		GAA_FLAG_INCLUDE_GATEWAYS |
		GAA_FLAG_SKIP_DNS_SERVER |
		GAA_FLAG_SKIP_MULTICAST;

	char stack_buffer[8192];
	std::vector<char> heap_buffer;

	auto adapter_0 = reinterpret_cast<PIP_ADAPTER_ADDRESSES>(stack_buffer);
	ULONG buffer_length = sizeof(stack_buffer);

	const auto error_0 = ::GetAdaptersAddresses(
		AF_UNSPEC, flags, nullptr, adapter_0, &buffer_length);
	if (error_0 == ERROR_BUFFER_OVERFLOW && buffer_length > 0)
	{
		heap_buffer.resize(buffer_length);
		adapter_0 = reinterpret_cast<PIP_ADAPTER_ADDRESSES>(&heap_buffer[0]);

		const auto error_1 = ::GetAdaptersAddresses(
			AF_UNSPEC, flags, nullptr, adapter_0, &buffer_length);
		if (error_1 != NO_ERROR)
		{
			return std::nullopt;
		}
	}
	else if (error_0 != NO_ERROR)
	{
		return std::nullopt;
	}

	BYTE* mac = nullptr;
	bool gateway = false;

	for (auto adapter = adapter_0; adapter; adapter = adapter->Next)
	{
		if (adapter->PhysicalAddressLength == 6)
		{
			if (!mac)
			{
				// First Mac address
				mac = adapter->PhysicalAddress;
			}

			if (!gateway && adapter->FirstGatewayAddress)
			{
				// The adapter with the gateway address takes precedence.
				mac = adapter->PhysicalAddress;
				gateway = true;
			}
		}
	}

	if (mac)
	{
		return std::array<uint8_t, 6>{ mac[0], mac[1], mac[2], mac[3], mac[4], mac[5] };
	}

	return std::nullopt;
}

get_first_mac_address_windows.h

#ifndef GET_FIRST_MAC_ADDRESS_WINDOWS__H__
#define GET_FIRST_MAC_ADDRESS_WINDOWS__H__

#include <array>
#include <optional>
#include <utility>


std::optional<std::array<uint8_t, 6>> get_first_mac_address();

#endif