[BB #338] Bind transmission to VPN interface

[xixix-ft]

Ref. https://bitbucket.org/pedro311/freshtomato-arm/issues/338/bind-transmission-to-vpn-interface

rs232 created an issue 2024-09-22

Since the router is not to take advantage of PBR there’s a genuine risk that transmission traffic might leak via the WAN IP.. Beside this PBR is only available for openVPN.

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To prevent this, it would be advised to bind transmission to a specific interface. As I’m reading, despite the huge interest, as per today such an option doesn’t exist in the config. Out of the box, this can only be bind to an IP. This would require some extra code to make sure at every firewall call the bind to IP is accurate and aligned to whatever VPN interface is in use (tun11/12/13/wg0/wg1/wg2/etc)

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P.S. It seems like there are some “colourful” options to fix this:

https://askubuntu.com/questions/37412/how-can-i-ensure-transmission-traffic-uses-a-vpn