--net=slirp4netns:port_handler=slirp4netns
See https://github.com/containers/podman/discussions/10472#discu...
Shouldn't it also be possible to detect the source IP address if you use socket activation? (I haven't tried it out, though).
Regarding the other idea: I've now tested it and verified that it works. The remote address is available when running a socket-activated container with rootless Podman.