The French ISP Free provide TV over DSL. Some of the channels could be directly seen on a computer through the RTSP protocol. However it is not something that is working nicely through a home switch that is just behind the FreeBox DSL router like an OpenWRT running box.

Several solution exist on the net however major part of them required static port forwarding linked with configuration of VLC (The recommended client). Here we will see how to allow it without all this strong and static configuration with the help of two kernel module that will track the RTSP connexion, open the correct port in the firewall and routes the packet to the VLC client. These two modules are ip_nat_rtsp et ip_conntrack_rtsp

To process only the kmod-ipt-nathelper-extra package need to be installed on the OpenWRT box. Do either through the web interface or through ssh with the help of opkg. After installation check that the two requiered modules are loaded with the two following commands on the OpenWRT box:

insmod ip_conntrack_rtsp
insmod ip_nat_rtsp

If its answer that insmod: a module named ip_nat_rtsp already exists, it means that the module is already loaded.

Now you just have to launch you preferred player and start watching.