Hi...I've started to develop xdmcp module, or ip_nat_xdmcp and ip_conntrack_xdmcp..
But It's my first time to develop this, I have so many questions...
I'd searched all the documents in the online world...
I've get many things from that, but I still have many questions..
I wish this mail doesn't bother you...
I read ip_conntrack_ftp(irc), ip_nat_ftp(irc) source files...
But I don't know what exact mechanism is.... there is not enough explanation.... T.T
I think the mechanism is shown below...
If I am wrong, please let me know that...
I think.....
First of all, conntrack module is for the relationship of the packet or datagram...
ie. A and B are related packet of C
Briefly second, nat module is literal NAT module, it translate network address...
But, I don't know how to two different, seperate modules connected...
I think it maybe from init function...
I can't distinguish the meaning of the ip_conntrack_helper or ip_nat_helper...
What is ip_(*)_helper.tuple.src.u.tcp.port?
It is literal source port number? If data come from client to server, the
client tcp port? and If data come from server to client, the server tcp port? hard to
understand...
or src port is absolutely client port in every case?
what is ip_(*)_helper.tuple.dst.protonum?
This is same question like above...
and mask?
I think upper my explanation is wrong...
Because I've wander from this meaning to that meaning, very depressed...
I'd explain how to xdmcp masq module works..
If anybody can help me, do not hesitate to contact me...
First of all, client send xdmcp(UDP port 177) message.
The server responds this message, and send respond message to client.
Then client send xdmcp message including ip and display number. Then masq must change
this ip and display number in xdmcp header(=udp data)
Server after receiving this message, trys to new connect to client with ip and
port(=6000+display no)(tcp connection). And many connections..
ie.If display no=1, client 10023port to connect server 6001, client 10043 port connect
server 6002....
Its mechanism is somewhat like the ftp active mode...
I think it is very similar ftp module, but hard to implements it really....
And there are somewhat subtle problem...time out...
Because there are many tcp connections, and there is maybe no data in some connection,
I must forcely refresh the time....of related connection...
Please let me know the exact meaning src and dst of ip_conntract..
Thanks for reading ...
Have a nice day today....
