How to bridge wlan0 to eth0 without a static ip?

Question

I'm having internet issues in my dorm and I can solve them by bridging the dorm's WiFi (wlan0) to ethernet (eth0). I've read a lot of tutorials online, but most of them are outdated or not applicable in my case.

Because I don't own the network I can't get myself a static IP for the pi and there is also a login portal that I have to go through every time to connect.

I've read that it's not possible to have a real bridge between wlan0 and eth0 because of hardware limitations, but I just need to be able to plug in an ethernet cable into my pi and have it connect to the network via the pi's WiFi.

How would I go about doing this given the limitations I have (non-static IP and the login portal)? The networks don't have to be on the same subnet.

Thanks!

Answer 1

You are right when saying it's not possible to add an interface for a WiFi client connection to a bridge. But there are some possibilities to workaround this. The most general solution is proxy arp. It is not a real bridge but it behaves like a bridge. The connected clients seem to get part of the local network and can use all its resources including a DHCP server. So they will get an ip address from the network. The disadvantage is that you need some helper programs that makes setup not as easy as configuring a bridge. How to use it you can look at Workaround for a wifi bridge on a Raspberry Pi with proxy arp.