/// <summary>
/// Creates and adds a new connection mapping to the NAT.
/// </summary>
/// <param name="networkPort">The network interface number of the inside node.</param>
/// <param name="insideNode">The inside node.</param>
/// <param name="outsideNode">The outside node.</param>
/// <param name="connection">The <see cref="NatConnection{TPacket, TNode}"/> that is created.</param>
private void CreateMapping(int networkPort, TNode insideNode, TNode outsideNode, out NatConnection <TPacket, TNode> connection)
{
// Get the node which the outside node will see as the source. E.g. the NAT with a new TCP port
var natNode = CreateMasqueradeNode(OutsideFacingAddress, Port_Drop, PaxConfig.deviceMap[Port_Outside].MacAddress);
// Create connection object
connection = new NatConnection <TPacket, TNode>(insideNode, outsideNode, natNode, GetInitialStateForNewConnection());
// Add to NAT_MapToOutside
var toOutsideKey = new ConnectionKey(insideNode, outsideNode);
NAT_MapToOutside[toOutsideKey] = connection;
// Add to NAT_MapToInside
var toInsideKey = new ConnectionKey(outsideNode, natNode);
NAT_MapToInside[toInsideKey] = connection;
#if DEBUG
Console.WriteLine("Added mapping");
Console.WriteLine("Inside: {0}", insideNode);
Console.WriteLine("Outside: {0}", outsideNode);
Console.WriteLine("Nat: {0}", natNode);
PrintMappings();
#endif
}
/// <summary>
/// Rewrite packets coming from the Outside and forward on the relevant Inside network port.
/// </summary>
/// <param name="packet">The incoming packet.</param>
private ForwardingDecision OutsideToInside(TEncapsulation packet)
{
// Retrieve the mapping. If a mapping doesn't exist, then it means that we're not
// aware of a session to which the packet belongs: so drop the packet.
var key = new ConnectionKey(packet.GetSourceNode(), packet.GetDestinationNode());
NatConnection <TPacket, TNode> connection;
if (NAT_MapToInside.TryGetValue(key, out connection))
{
var destination = connection.InsideNode;
// Update any connection state, including resetting the inactivity timer
connection.ReceivedPacket(packet, packetFromInside: false);
// Rewrite the packet destination
packet.SetDestination(destination);
// Update checksums
packet.UpdateChecksums();
// Forward on the mapped network port
return(new ForwardingDecision.SinglePortForward(destination.InterfaceNumber));
}
else
{
return(Drop);
}
}
/// <summary>
/// Rewrite packets coming from the Inside and forward on the Outside network port.
/// </summary>
/// <param name="packet">The outgoing packet.</param>
private ForwardingDecision InsideToOutside(TEncapsulation packet, int incomingInterfaceNumber)
{
// Get the mapping key, providing the interface numbers and mac in case we need to add a mapping
packet.LinkPacket.DestinationHwAddress = NextOutsideHopMacAddress; // Change MAC to reflect actual destination
TNode insideNode = packet.GetSourceNode(incomingInterfaceNumber),
outsideNode = packet.GetDestinationNode(Port_Outside);
var out_key = new ConnectionKey(insideNode, outsideNode);
NatConnection <TPacket, TNode> connection;
bool mappingExists = NAT_MapToOutside.TryGetValue(out_key, out connection);
if (!mappingExists)
{
if (packet.SignalsStartOfConnection())
{
// If new connection, then add a mapping
CreateMapping(incomingInterfaceNumber, insideNode, outsideNode, out connection);
}
else
{
// Not a new connection and no existing connection, so drop.
return(Drop);
}
}
// Update any connection state, including resetting the inactivity timer
connection.ReceivedPacket(packet, packetFromInside: true);
// Rewrite the packet to appear to originate from the NAT
packet.SetSource(connection.NatNode);
// Update checksums
packet.UpdateChecksums();
// Forward on the mapped network port
return(new ForwardingDecision.SinglePortForward(connection.OutsideNode.InterfaceNumber));
}