Running a Single Application Through a VPN

[QasimK]

Comment on Running a Single Application Through a VPN.

[Yureien]

Hey, I used this to run an app through a VPN, but that app requires access to an SQL server on the host running on localhost with port 5432. How do I access this?

[QasimK]

Hi @fadedcoder. That's a great question, and one that I hint at at the bottom of the article ("Aside: Local listening Apps). However, there are multiple solutions to this. The most reliable might involve setting up a private network for the network namespace like 10.0.3.0/24, and then accessing the host via 10.0.3.1. This is closer to what LXC or Docker can do with their containers.

A more hacky solution mentioned in the article is socat, which can connect arbitrary sockets (UDP, TCP, UNIX sockets) together. This is what I do because it ensures there is absolutely no other connection between the network namespace and the host.

While you may need to play around with it, doing something like

sudo /usr/bin/socat tcp-connect:127.0.0.1:5432,nofork exec:'ip netns exec NETNS socat STDIO tcp-listen\:127.0.0.1\:5432',fork,reuseaddr

This will create a listening socket on port 5432 inside the network namespace, which connects to port 5432 on the host.

I can't help you beyond this!

[Yureien]

I get a

2019/05/24 22:12:15 socat[1406] E parseopts(): option "nofork" not supported with this address type

when doing the socat one. Any help for that?

[QasimK]

Hey, I would suggest playing around with the command (maybe get rid of nofork from it?), and searching online for tutorials or examples of socat!