/// <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>
/// Remove connections that have timed out or are closed.
/// </summary>
public void GarbageCollectConnections()
{
bool removedAny = false;
DateTime now = DateTime.Now;
foreach (var pair in NAT_MapToInside)
{
NatConnection <TPacket, TNode> connection = pair.Value;
bool removeEntry = false;
if (now - connection.LastUsed > InactivityTimeout)
{
removeEntry = true;
#if DEBUG
Console.WriteLine("Removing inactive connection (LastUsed {0}, Diff {1}, InactivityTimeout {2})",
connection.LastUsed.ToShortTimeString(),
(now - connection.LastUsed).ToString(),
InactivityTimeout);
#endif
}
else if (connection.State.CanBeClosed)
{
removeEntry = true;
#if DEBUG
Console.WriteLine("Removing closed connection (LastUsed {0}, Diff {1}, InactivityTimeout {2})",
connection.LastUsed.ToShortTimeString(),
(now - connection.LastUsed).ToString(),
InactivityTimeout);
#endif
}
if (removeEntry)
{
// Remove this connection from both lookups
NAT_MapToInside.Remove(pair);
NAT_MapToOutside.Remove(new ConnectionKey(connection.InsideNode, connection.OutsideNode));
#if DEBUG
removedAny = true;
#endif
}
}
#if DEBUG
if (removedAny)
{
PrintMappings();
}
#endif
// FIXME - currently O(n); improve performance for sparse traffic.
// Could use a regularly invoked GC, and keep the connections in one of two pools:
// - For connections with lower traffic, keep a double-LL of MRU, moving the connection to the head when used,
// and start at the LRU end when iterating. Needs to be concurrent.
// Cost is per packet, and maintains an ordering, meaning we only need to check those that have expired plus one extra.
// - For connections with higher traffic, it would be less expensive to leave unsorted and iterate in O(n).
// However, this would add complexity in terms of tracking which pool each connection should be in.
}
