port forwarding in Linux

Question

I'm dealing with a issue involving port forwarding. I've got part of it working, trying to get the rest.

for now:
I have a serverside machine:
-runs the gearmand daemon on localhost port 4730
-runs the server.php - on ip localhost port 4730
-also runs the portforwarding which is created on the clientside to connect to localhost:4730
-the test server is runs on a machine as user foo@192.168.5.12

on the clientside machine
-runs the client.php - which runs on localhost port 4730
-also runs the ssh port forwarding process as follows
ssh -f -L - N 4730:localhost:4730 foo@192.168.5.12 -p 22
-the client is running on 192.168.5.14

Everything above works... I can run a serverside process, and the clientside workers get the data from the queue on localhost:4730

I'd like to be able to change the ip address of the gearman processes from localhost, to the actual ipaddress of the machine. This of course involves changing the port forwarding from the client to the server
machine.

Answer 1

simple with a systemd-unit which also survives a reboot of the target machine because the command in ExecStart (which is *one* line including the port 22 of the forwarded service, in this case SSH of a internal machine) will fail in that case and the SSH command is executed 60 seconds later

/etc/sysconfig/forwarding contains the IP-address where the forwarding should listen instead 127.0.0.1, done this way because there is a fallback machine, more than one such services and so the systemd-units can be re-used

the result in short is 192.168.0.35:11025 is the forwarded 192.168.1.15:22 192.168.0.0/24 is a different subnet than 192.168.1.0/24, the numbers are generic to not disclose network-configurations, the files below are from a live-machine in all other parts

[root@localhost:~]$ cat /etc/sysconfig/forwarding
LOCAL_ADDRESS=192.168.0.35
________________________________________________

[root@localhost:~]$ cat /etc/systemd/system/forward-fileserver.service
[Unit]
Description=SSH-Forwarding Fileserver
After=network.service openvpn.service hostapd.service network-wlan-bridge.service network-bonding-bridge.service

[Service]
Type=simple
EnvironmentFile=/etc/sysconfig/forwarding
ExecStart=/usr/bin/ssh -i /home/ssh-gateway/.ssh/id_rsa ssh-gateway@192.168.1.15 -N -C
-L${LOCAL_ADDRESS}:11025:127.0.0.1:22
Restart=always
RestartSec=60
TimeoutSec=30
CapabilityBoundingSet=CAP_NET_BIND_SERVICE CAP_DAC_OVERRIDE

[Install]
WantedBy=multi-user.target