private void TraceTcpNatContext(NATContext context, TcpFrame frame)
{
if (context == null || frame == null)
{
return;
}
NATContext.StateCode state = NATContext.StateCode.TCP_RST; // 跟踪TCP协议报文状态
if (0 != (frame.Flags & TcpFlags.TCP_SYN))
{
state = NATContext.StateCode.TCP_SYN;
}
else if (0 != (frame.Flags & TcpFlags.TCP_FIN))
{
state = NATContext.StateCode.TCP_FIN;
}
else if (0 != (frame.Flags & TcpFlags.TCP_RST))
{
state = NATContext.StateCode.TCP_RST;
}
else if (0 != (frame.Flags & (TcpFlags.TCP_PSH | TcpFlags.TCP_ACK)))
{
state = NATContext.StateCode.TCP_RECVED;
}
if (context.State != NATContext.StateCode.TCP_FIN &&
context.State != NATContext.StateCode.TCP_RST)
{
context.Restart().State = state;
}
}
public virtual NATContext PrivateInput(IPAddress sources, IPAddress destination, ushort Identification)
{
if (sources == null || destination == null)
{
return(null);
}
this.DoEvents();
long sources_key = Ethernet.GetAddress(sources);
lock (this.m_AddressToContext)
{
lock (this.m_syncobj)
{
this.m_AddressToContext.TryGetValue(sources_key, out NATContext context);
if (context == null && 0 != Identification)
{
context = new NATContext()
{
LocalEP = new IPEndPoint(this.m_nat.m_ethernetAddress, 0),
AgingTimePeriod = new Stopwatch(),
Sources = new IPEndPoint(sources, Identification),
Destination = new IPEndPoint(destination, 0),
State = NATContext.StateCode.TCP_NIL,
};
this.m_AddressToContext[sources_key] = context;
}
return(context?.Restart());
}
}
}
public virtual NATContext PrivateInput(IPEndPoint sources, IPEndPoint destination, bool creational, bool autorestat = true)
{
if (sources == null || destination == null)
{
return(null);
}
else
{
this.DoEvents();
}
long keySourcesContext = EndPointToLongKey(sources);
lock (this.m_AddressToContext)
{
lock (this.m_syncobj)
{
this.m_SourcesToContext.TryGetValue(keySourcesContext, out NATContext context);
if (context == null)
{
if (!creational)
{
return(null);
}
if (this.m_AddressToContext.Count >= IPEndPoint.MaxPort)
{
return(null);
}
int port = NewBindPort(this.ProtocolType);
if (port > IPEndPoint.MinPort && port <= IPEndPoint.MaxPort)
{
IPEndPoint localEP = new IPEndPoint(this.m_nat.m_ethernetAddress, port);
if (localEP != null)
{
context = new NATContext()
{
Sources = sources,
Destination = destination,
LocalEP = localEP,
AgingTimePeriod = new Stopwatch(),
State = NATContext.StateCode.TCP_NIL,
};
this.m_AddressToContext[localEP.Port] = context;
this.m_SourcesToContext[keySourcesContext] = context;
}
}
}
if (!autorestat)
{
return(context);
}
return(RestartContextAgingTime(context));
}
}
}
private bool PrivateIcmpInput(IPFrame packet)
{
IcmpFrame frame = IcmpLayer.ParseFrame(packet, false);
if (frame == null)
{
return(false);
}
NATContext context = this.m_contextsIcmp.PrivateInput(frame.Source, frame.Destination, frame.Identification);
if (context == null)
{
return(false);
}
IcmpFrame convertional = null;
int ttl = frame.Ttl - 1;
if (ttl <= 0)
{
convertional = new IcmpFrame(this.m_ethernetAddress, frame.Source, IPv4Layer.ToArray(packet))
{
Ttl = packet.Ttl,
Type = IcmpType.ICMP_TE,
Code = 0,
Sequence = 0,
Identification = 0,
};
IPFrame replay = CopyFrameHeaderParts(IcmpLayer.ToIPFrame(convertional), packet);
if (replay == null)
{
return(false);
}
return(this.OnPrivateOutput(replay));
}
else
{
convertional = new IcmpFrame(this.m_ethernetAddress, frame.Destination, frame.Payload)
{
Ttl = ttl,
Type = frame.Type,
Code = frame.Code,
Sequence = frame.Sequence,
Identification = frame.Identification /*unchecked((ushort)context.Destination.Port)*/,
};
}
IPFrame ip = CopyFrameHeaderParts(IcmpLayer.ToIPFrame(convertional), packet);
if (ip == null)
{
return(false);
}
return(this.OnPublicOutput(ip));
}
private NATContext RestartContextAgingTime(NATContext context)
{
if (context == null)
{
return(context);
}
if (this.ProtocolType != ProtocolType.Tcp)
{
return(context);
}
if (context.State == NATContext.StateCode.TCP_RECVED || context.State == NATContext.StateCode.TCP_SYN)
{
return(context.Restart());
}
return(context);
}
private bool PublicIcmpNATOutput(NATContext context, IcmpFrame frame, IPFrame packet)
{
if (context == null || frame == null || packet == null)
{
return(false);
}
if (frame.Type != IcmpType.ICMP_ER) // TIME EXCEEDED
{
IPFrame ipAgo = IPv4Layer.ParseFrame(frame.Payload, false);
IcmpFrame icmpAgo = IcmpLayer.ParseFrame(ipAgo, false);
if (icmpAgo == null) // 这是一个伪造的ICMP数据报，正确报文应答必须要包含从本机发向对端主机的ICMP/IP数据报文
{
return(false);
}
ipAgo = CopyFrameHeaderParts(IcmpLayer.ToIPFrame(new IcmpFrame(frame.Source, context.Sources.Address, icmpAgo.Payload) // 重新汇编整个ICMP/IP数据报文
{
Ttl = icmpAgo.Ttl,
Type = icmpAgo.Type,
Code = icmpAgo.Code,
Sequence = icmpAgo.Sequence,
Identification = unchecked ((ushort)context.Sources.Port), // 客户端ICMP协议请求时的凭证编号
}), ipAgo);
frame.Payload = IPv4Layer.ToArray(ipAgo);
}
var convertional = new IcmpFrame(frame.Source, context.Sources.Address, frame.Payload)
{
Ttl = frame.Ttl - 1,
Type = frame.Type,
Code = frame.Code,
Sequence = frame.Sequence,
Identification = frame.Identification,
};
IPFrame ip = CopyFrameHeaderParts(IcmpLayer.ToIPFrame(convertional), packet);
if (ip == null)
{
return(false);
}
return(this.OnPrivateOutput(ip));
}
public virtual int Release(IPAddress sources)
{
long sources_key = Ethernet.GetAddress(sources);
if (sources == null)
{
return(0);
}
NATContext context = null;
lock (this.m_AddressToContext)
{
lock (this.m_syncobj)
{
this.m_AddressToContext.TryRemove(sources_key, out context);
if (context == null)
{
return(0);
}
}
}
context.Dispose();
return(1);
}
public virtual bool PublicInput(IPFrame packet)
{
if (packet == null)
{
return(false);
}
switch (packet.ProtocolType)
{
case ProtocolType.Udp:
{
UdpFrame frame = UdpLayer.ParseFrame(packet, true);
if (frame == null)
{
return(false);
}
NATContext context = this.m_contextsUdp.PublicInput(frame.Source, frame.Destination);
if (context == null)
{
return(false);
}
var convertional = new UdpFrame(frame.Source, context.Sources, frame.Payload)
{
Ttl = frame.Ttl,
};
IPFrame ip = CopyFrameHeaderParts(UdpLayer.ToIPFrame(convertional), packet);
if (ip == null)
{
return(false);
}
return(this.OnPrivateOutput(ip));
}
case ProtocolType.Tcp:
{
TcpFrame frame = TcpLayer.ParseFrame(packet, true);
if (frame == null)
{
return(false);
}
NATContext context = this.m_contextsTcp.PublicInput(frame.Source, frame.Destination);
if (context == null)
{
return(false);
}
else
{
TraceTcpNatContext(context, frame);
}
var convertional = new TcpFrame(frame.Source, context.Sources, frame.Payload)
{
Ttl = frame.Ttl,
AcknowledgeNo = frame.AcknowledgeNo,
Flags = frame.Flags,
SequenceNo = frame.SequenceNo,
WindowSize = frame.WindowSize,
Options = frame.Options,
UrgentPointer = frame.UrgentPointer,
};
IPFrame ip = CopyFrameHeaderParts(TcpLayer.ToIPFrame(convertional), packet);
if (ip == null)
{
return(false);
}
return(this.OnPrivateOutput(ip));
}
case ProtocolType.Icmp:
return(this.PublicIcmpInput(packet));
default:
return(false);
}
}