I'm using this presentation
https://mum.mikrotik.com/presentations/US12/steve.pdf to do PCC. However, I'm getting stuck at the step where I add mangle rules to mark returning packets from WAN interfaces. In my network, I'm using IPIP tunnels to send data out, but due to the way I'm routing the network, packets will return without any IPIP through the regular ethernet interfaces. Is there a way to still make it work? There will be multiple routers sending packets back on each interface.