autossh: impossible to provide tunneled service to local network

autossh: impossible to provide tunneled service to local network

Maintainer: @neheb
Environment: ath79/generic OpenWrt 23.05.0 r23497-6637af95aa / LuCI openwrt-23.05 branch git-24.086.45142-09d5a38

Description:
This forwarding mechanism:
https://github.com/openwrt/packages/blob/master/net/autossh/files/autossh.init#L37

			forwarding="-L ${localport}:${remotehost}:${remoteport}"

Makes it impossible to use autossh to provide a tunneled service to the local network (for example; or anything other than localhost) because the ${localhost} argument is not used in local forwarding (and so it defaults to literal localhost).

It should be:

			forwarding="-L ${localhost}:${localport}:${remotehost}:${remoteport}"

This enables forward like: -L 192.168.0.1:80:127.0.0.1:80 ...to provide LAN access to a HTTP service provided locally on remote host (and not over the internet).

The remote line should probably also be changed, but it is not required for my use case.

Start in net/autossh/files/autossh.init at the forwarding assignment around line 37 and inspect how the localhost argument is used for local forwarding. Confirm that the generated forwarding option can bind the requested local network address, such as 192.168.0.1, while preserving the remote host and port values.