Re: Iptables Forwarded traffic

fr@xxxxx a écrit :

- is this possible the new port open by the ftp connection would receive any
ftp order or command, even it is not the order sollicited by the local
computer ?

FTP related connections are data connections which do not transport commands but only data such as directory listings and files. Only the initial control connection on a fixed port (usually 21) transports commands. Basically such commands may say to the other side : "please connect to my port xxx in order to send|receive the data". If loaded, the FTP connection tracking helper module reads the control connection and will consider RELATED only a connection from the remote FTP agent to the port that was specified in the above command. Connections from the same host to other ports will be considered NEW, not RELATED.

- in the case of RTSP protocol which use arbirtrary related port to answer
(like freebox tv), what will happen ?

The behaviour is the same as FTP. The RTSP connection uses a well known fixed port (usually 554) and transport requests from the client to the server saying "please send the UDP data stream to port xxx". If loaded, the RTSP connection tracking helper module reads the RTSP connection and will consider RELATED only UDP packets from the server to the client port that was specified in the request. Note that the RTSP conntrack and NAT helper module is not yet included in the mainline Linux kernel.
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