I currently ssh into a device where I have a bunch of -L and -R port forwards between my client and the device. But this isn't unique to me; everyone else who should ssh into this device needs these ports mapped.
What is the best way to translate the -L/-R ssh syntax into a permanent configuration on the device side? Is it even possible for -R forwards, even if its on the localhost?
You can't place any configuration onto the device side, because by the time you have access to the remote device, the connection has already been established. You can only place configuration options in your local ~/.ssh/config` file.
It would be a terrible security problem if the remote end could configure forwarding; imagine if a malicious administrator arranged for access to your local machine whenever you logged into their server!
On your local system, you can configure the equivalent of -L and -R in your ssh configuration using the LocalForward and RemoteForward configuration options.
If you would normally run something like:
ssh -L 2000:localhost:2000 -L 3000:localhost:3000 -R 2200:localhost:22 myhost.example.com
Then you could place the following in ~/.ssh/config:
Host myhost.example.com
LocalForward 2000 localhost:2000
LocalForward 3000 localhost:3000
RemoteForward 2200 localhost:22
Then whenver you run ssh myhost.example.com, ssh would set up the requested local and remote port forwarding.