/// Obtains the best MAC address found on local network interfaces.
/// Generally speaking, an active network interface used on public
/// networks is better than a local network interface.
/// <returns>byte array containing a MAC. null if no MAC can be found.</returns>
public static byte[] GetBestAvailableMac()
{
// Find the best MAC address available.
byte[] bestMacAddr = NotFound;
IPAddress bestInetAddr = IPAddress.Loopback;
// Retrieve the list of available network interfaces.
Dictionary <NetworkInterface, IPAddress> ifaces = new Dictionary <NetworkInterface, IPAddress>();
try
{
foreach (var iface in NetworkInterface.GetAllNetworkInterfaces())
{
// Use the interface with proper INET addresses only.
var addrs = iface.GetIPProperties().UnicastAddresses;
if ((uint)addrs.Count > 0u)
{
var addressInfo = addrs.First();
if (!IPAddress.IsLoopback(addressInfo.Address))
{
ifaces.Add(iface, addressInfo.Address);
}
}
}
}
catch (SocketException e)
{
logger.FailedToRetrieveTheListOfAvailableNetworkInterfaces(e);
}
foreach (var entry in ifaces)
{
NetworkInterface iface = entry.Key;
IPAddress inetAddr = entry.Value;
// todo: netty has a check for whether interface is virtual but it always returns false. There is no equivalent in .NET
byte[] macAddr = iface.GetPhysicalAddress()?.GetAddressBytes();
bool replace = false;
uint res = (uint)CompareAddresses(bestMacAddr, macAddr);
if (res > SharedConstants.TooBigOrNegative) // res < 0
{
// Found a better MAC address.
replace = true;
}
else if (0u >= res)
{
// Two MAC addresses are of pretty much same quality.
res = (uint)CompareAddresses(bestInetAddr, inetAddr);
if (res > SharedConstants.TooBigOrNegative) // res < 0
{
// Found a MAC address with better INET address.
replace = true;
}
else if (0u >= res)
{
// Cannot tell the difference. Choose the longer one.
if ((uint)bestMacAddr.Length < (uint)macAddr.Length)
{
replace = true;
}
}
}
if (replace)
{
bestMacAddr = macAddr;
bestInetAddr = inetAddr;
}
}
if (bestMacAddr == NotFound)
{
return(null);
}
switch (bestMacAddr.Length)
{
case 6: // EUI-48 - convert to EUI-64
var newAddr = new byte[MacAddressLength];
Array.Copy(bestMacAddr, 0, newAddr, 0, 3);
newAddr[3] = 0xFF;
newAddr[4] = 0xFE;
Array.Copy(bestMacAddr, 3, newAddr, 5, 3);
bestMacAddr = newAddr;
break;
default: // Unknown
bestMacAddr = bestMacAddr.Slice(0, Math.Min(bestMacAddr.Length, MacAddressLength));
break;
}
return(bestMacAddr);
}
