NatTypeTester/src/STUN/Enums/NatType.cs

namespace STUN.Enums;

/// <summary>
/// https://tools.ietf.org/html/rfc3489#section-5
/// https://tools.ietf.org/html/rfc3489#section-10.1
/// </summary>
public enum NatType
{
	/// <summary>
	/// Unknown
	/// </summary>
	Unknown,

	/// <summary>
	/// Server is not unsupported for testing NAT type
	/// </summary>
	UnsupportedServer,

	/// <summary>
	/// UDP is always blocked.
	/// </summary>
	UdpBlocked,

	/// <summary>
	/// No NAT, public IP, no firewall.
	/// </summary>
	OpenInternet,

	/// <summary>
	/// No NAT, public IP, but symmetric UDP firewall.
	/// </summary>
	SymmetricUdpFirewall,

	/// <summary>
	/// A full cone NAT is one where all requests from the same internal IP address and port are 
	/// mapped to the same external IP address and port. Furthermore, any external host can send 
	/// a packet to the internal host, by sending a packet to the mapped external address.
	/// </summary>
	FullCone,

	/// <summary>
	/// A restricted cone NAT is one where all requests from the same internal IP address and 
	/// port are mapped to the same external IP address and port. Unlike a full cone NAT, an external
	/// host (with IP address X) can send a packet to the internal host only if the internal host 
	/// had previously sent a packet to IP address X.
	/// </summary>
	RestrictedCone,

	/// <summary>
	/// A port restricted cone NAT is like a restricted cone NAT, but the restriction 
	/// includes port numbers. Specifically, an external host can send a packet, with source IP
	/// address X and source port P, to the internal host only if the internal host had previously 
	/// sent a packet to IP address X and port P.
	/// </summary>
	PortRestrictedCone,

	/// <summary>
	/// A symmetric NAT is one where all requests from the same internal IP address and port, 
	/// to a specific destination IP address and port, are mapped to the same external IP address and
	/// port.  If the same host sends a packet with the same source address and port, but to 
	/// a different destination, a different mapping is used. Furthermore, only the external host that
	/// receives a packet can send a UDP packet back to the internal host.
	/// </summary>
	Symmetric
}