Route http traffic to a Macbook running Charles Web proxy

Hi all,

I'm doing some web development on a Freeview Play set top box (stb) and am trying to redirect the traffic to my Macbook which is on the same network. I have Charles Web proxy running on the Mac listening on port 8888. The goal being that I can redirect http requests from the stb to local versions on my Mac via the Charles "Map Local" feature.

I'm using a GL-MT300N, the STB is connected to the one LAN port and the Mac is connected via Wifi. As a side note, the GL-MT300N is connected to the internet via an Amazon Eero, which in turn is connected to a modem / router via the WAN port.

I've tried various combinations of IPTABLES PREROUTING / POSTROUTING and FORWARD and also tried using the uci config option but am not getting anywhere. The web apps on the STB won't load when I have iptables or a config rule switched on. Here's an example of what I've tried:


iptables -t nat -A PREROUTING -i br-lan -p tcp --dport 80 -j DNAT --to $PROXY_IP:$PROXY_PORT
iptables -t nat -A POSTROUTING -o br-lan -s $LAN_NET -d $PROXY_IP -j MASQUERADE
iptables -A FORWARD -s $LAN_NET -d $PROXY_IP -i br-lan -o br-lan -p tcp --dport $PROXY_PORT -j ACCEPT

Any suggestions on what to try would be most welcome!