NatTypeTester/STUN/Utils/AttributeExtensions.cs

using STUN.Enums;
using STUN.Messages;
using STUN.Messages.StunAttributeValues;
using System;
using System.Linq;
using System.Net;

namespace STUN.Utils;

public static class AttributeExtensions
{
	public static StunAttribute BuildChangeRequest(bool changeIp, bool changePort)
	{
		return new StunAttribute
		{
			Type = AttributeType.ChangeRequest,
			Length = 4,
			Value = new ChangeRequestStunAttributeValue { ChangeIp = changeIp, ChangePort = changePort }
		};
	}

	public static StunAttribute BuildMapping(IpFamily family, IPAddress ip, ushort port)
	{
		var length = family switch
		{
			IpFamily.IPv4 => 4,
			IpFamily.IPv6 => 16,
			_ => throw new ArgumentOutOfRangeException(nameof(family), family, null)
		};
		return new StunAttribute
		{
			Type = AttributeType.MappedAddress,
			Length = (ushort)(4 + length),
			Value = new MappedAddressStunAttributeValue
			{
				Family = family,
				Address = ip,
				Port = port
			}
		};
	}

	public static StunAttribute BuildChangeAddress(IpFamily family, IPAddress ip, ushort port)
	{
		var length = family switch
		{
			IpFamily.IPv4 => 4,
			IpFamily.IPv6 => 16,
			_ => throw new ArgumentOutOfRangeException(nameof(family), family, null)
		};
		return new StunAttribute
		{
			Type = AttributeType.ChangedAddress,
			Length = (ushort)(4 + length),
			Value = new ChangedAddressStunAttributeValue
			{
				Family = family,
				Address = ip,
				Port = port
			}
		};
	}

	public static IPEndPoint? GetMappedAddressAttribute(this StunMessage5389 response)
	{
		var mappedAddressAttribute = response.Attributes.FirstOrDefault(t => t.Type == AttributeType.MappedAddress);

		if (mappedAddressAttribute is null)
		{
			return null;
		}

		var mapped = (MappedAddressStunAttributeValue)mappedAddressAttribute.Value;
		return new IPEndPoint(mapped.Address!, mapped.Port);
	}

	public static IPEndPoint? GetChangedAddressAttribute(this StunMessage5389 response)
	{
		var changedAddressAttribute = response.Attributes.FirstOrDefault(t => t.Type == AttributeType.ChangedAddress);

		if (changedAddressAttribute is null)
		{
			return null;
		}

		var address = (ChangedAddressStunAttributeValue)changedAddressAttribute.Value;
		return new IPEndPoint(address.Address!, address.Port);
	}

	public static IPEndPoint? GetXorMappedAddressAttribute(this StunMessage5389 response)
	{
		var mappedAddressAttribute =
			response.Attributes.FirstOrDefault(t => t.Type == AttributeType.XorMappedAddress) ??
			response.Attributes.FirstOrDefault(t => t.Type == AttributeType.MappedAddress);

		if (mappedAddressAttribute is null)
		{
			return null;
		}

		var mapped = (AddressStunAttributeValue)mappedAddressAttribute.Value;
		return new IPEndPoint(mapped.Address!, mapped.Port);
	}

	public static IPEndPoint? GetOtherAddressAttribute(this StunMessage5389 response)
	{
		var addressAttribute =
			response.Attributes.FirstOrDefault(t => t.Type == AttributeType.OtherAddress) ??
			response.Attributes.FirstOrDefault(t => t.Type == AttributeType.ChangedAddress);

		if (addressAttribute is null)
		{
			return null;
		}

		var address = (AddressStunAttributeValue)addressAttribute.Value;
		return new IPEndPoint(address.Address!, address.Port);
	}
}