// Seen from inside
private NATEntry CreateTranslationEntry(IPAddress ipaSource, IPAddress ipaDestination, int iSourcePort, int iDestinationPort, IP.IPProtocol iIPProtocol)
{
int iTranslatedSourcePort = 0;
NATEntry eNatEntry;
lock (lExternalRange)
{
foreach (IPAddress ipa in lExternalAddressPool)
{
if (iIPProtocol == IP.IPProtocol.UDP || iIPProtocol == IP.IPProtocol.TCP)
{
iTranslatedSourcePort = iRangeStartPort;
}
do
{
if (GetReTranslationEntry(ipa, ipaDestination, iTranslatedSourcePort, iDestinationPort, iIPProtocol) == null)
{
eNatEntry = new NATEntry(iIPProtocol, ipaSource, ipa, ipaDestination, iSourcePort, iTranslatedSourcePort, iDestinationPort);
eNatEntry.TTL = iNATTimer;
lock (lNATDatabase)
{
lNATDatabase.Add(eNatEntry);
}
InvokeExternalAsync(NATEntryCreated, new NATEventArgs(eNatEntry));
return(eNatEntry);
}
iTranslatedSourcePort++;
}while ((iIPProtocol == IP.IPProtocol.UDP || iIPProtocol == IP.IPProtocol.TCP) && iRangeStartPort < iRangeEndPort);
}
}
throw new Exception("A NAT entry could not be created cause the pools are exhausted. (Source: " + ipaSource + "/" + iSourcePort + ", Destination: " + ipaDestination + "/" + iDestinationPort + ", Protocol: " + iIPProtocol.ToString());
}
private void HandleFromInternal(Frame fInputFrame, int iSourcePort, int iDestinationPort, IP.IPFrame ipFrame, TCP.TCPFrame tcpFrame, UDP.UDPFrame udpFrame)
{
NATEntry neEntry = GetTranslationEntry(ipFrame.SourceAddress, ipFrame.DestinationAddress, iSourcePort, iDestinationPort, ipFrame.Protocol);
if (neEntry == null)
{
neEntry = CreateTranslationEntry(ipFrame.SourceAddress, ipFrame.DestinationAddress, iSourcePort, iDestinationPort, ipFrame.Protocol);
}
ipFrame.SourceAddress = neEntry.TranslatedSourceAddress;
if (tcpFrame != null)
{
tcpFrame.SourcePort = neEntry.TranslatedSourcePort;
tcpFrame.Checksum = tcpFrame.CalculateChecksum(ipFrame.GetPseudoHeader());
CheckForTCPFinish(tcpFrame, neEntry);
}
else if (udpFrame != null)
{
udpFrame.SourcePort = neEntry.TranslatedSourcePort;
udpFrame.Checksum = udpFrame.CalculateChecksum(ipFrame.GetPseudoHeader());
}
NotifyNextExternal(ipFrame);
}
private void HandleFromExternal(Frame fInputFrame, int iSourcePort, int iDestinationPort, IP.IPFrame ipFrame, TCP.TCPFrame tcpFrame, UDP.UDPFrame udpFrame)
{
NATEntry neEntry = GetReTranslationEntry(ipFrame.DestinationAddress, ipFrame.SourceAddress, iDestinationPort, iSourcePort, ipFrame.Protocol);
if (neEntry != null)
{
ipFrame.DestinationAddress = neEntry.OriginalSourceAddress;
if (tcpFrame != null)
{
tcpFrame.DestinationPort = neEntry.OriginalSourcePort;
tcpFrame.Checksum = tcpFrame.CalculateChecksum(ipFrame.GetPseudoHeader());
CheckForTCPFinish(tcpFrame, neEntry);
}
else if (udpFrame != null)
{
udpFrame.DestinationPort = neEntry.OriginalSourcePort;
udpFrame.Checksum = udpFrame.CalculateChecksum(ipFrame.GetPseudoHeader());
}
NotifyNextInternal(ipFrame);
}
else
{
PushDroppedFrame(fInputFrame);
if (bThrowOnNonNATFrame)
{
throw new Exception("The external frame was discarded because there was no corresponding translation entry in the database. (Source: " + ipFrame.SourceAddress + "/" + iSourcePort + ", Destination: " + ipFrame.DestinationAddress + "/" + iDestinationPort + ", Protocol: " + ipFrame.Protocol.ToString());
}
}
}
/// <summary>
/// Compares an object to this object
/// </summary>
/// <param name="obj">The object to compare to this object</param>
/// <returns>A bool indicating whether this object equals the given object</returns>
public override bool Equals(object obj)
{
if (obj is NATEntry)
{
NATEntry e = (NATEntry)obj;
return(e.iDestinationPort == this.iDestinationPort &&
e.iOriginalSourcePort == this.iOriginalSourcePort &&
e.ipaDestination == this.ipaDestination &&
e.ipaOriginalSource == this.ipaOriginalSource &&
e.ipaTranslatedSource == this.ipaTranslatedSource &&
e.ipProtocol == this.ipProtocol &&
e.iTranslatedSourcePort == this.iTranslatedSourcePort);
}
else
{
return(false);
}
}
private void CheckForTCPFinish(TCP.TCPFrame tcpFrame, NATEntry neEntry)
{
if (tcpFrame.FinishFlagSet) //TCP finish flag checking
{
if (neEntry.IsTCPTeardown)
{
neEntry.IsTCPFinished = true;
}
else
{
neEntry.IsTCPTeardown = true;
}
}
if (neEntry.IsTCPFinished && tcpFrame.AcknowledgementFlagSet) // Deactivate when finished
{
lock (lNATDatabase)
{
lNATDatabase.Remove(neEntry);
InvokeExternalAsync(NATEntryRemoved, new NATEventArgs(neEntry));
}
}
}
/// <summary>
/// Creates a new instance of this class
/// </summary>
/// <param name="neEntry">The entry to associate with this event</param>
public NATEventArgs(NATEntry neEntry)
{
this.neEntry = neEntry;
}
