So, I have a particular situation: I have a Marantz AVR that doesn't have WiFi, and a raspberry pi 3 with wifi running raspbian right next to it. I tried looking for solutions, but they all create a second NAT, therefore blocking AirPlay, which is what I need. Does anyone have a solution that allows the device to be connected directly to the network?
It's not not possible to bridge a WLAN station (client) directly to LAN, because the default mode on WLAN is 3-address, which means there's no room for the extra MAC address needed to distinguish the WLAN station (RaspPi) from anything else behind the bridge (Marantz).
It's possible to bridge a WLAN access point, however.
It's also possible to bridge a WLAN in 4-address mode, but all of your WLAN stations must be capable of using that mode.
iw set 4addr.