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));
}
protected virtual bool PublicIcmpInput(IPFrame packet)
{
IcmpFrame frame = IcmpLayer.ParseFrame(packet, true); // NDIS5/6内核层已检查过所以无需要重复计算ICMP报文CHECKSUM
if (frame == null)
{
return(false);
}
bool success = false; // 不知道这样的数据报文应该发向那个主机时广播到还允许NAT穿透ICMP报文的多个主机（但仅限对于ICMP/NAT）
foreach (NATContext secondary in this.m_contextsIcmp.GetAllContext()) // 稳定可靠NAT不丢帧（但可能造成虚拟NAT层压力过载）
{
success |= this.PublicIcmpNATOutput(secondary, frame, packet);
}
return(success);
}
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));
}
