How to make a different route for a separate application?

Question

linux

Good afternoon.
Ubuntu. Several outgoing vpn connections are up.
It is necessary that a certain application make all its connections through the desired vpn connection. Where the application goes is not known in advance.
Where to dig?

Answer 1

you need linux network namespace
blog.scottlowe.org/2013/09/04/introducing-linux-ne...
https://www.opennet.ru/tips/2683_linux_namespace_g...

Answer 2

In its container...

Answer 3

You can try to mark packets according to the owner criterion and apply different routing tables for them.
I tried it myself for a very long time, it seemed to work. There is a little on the link tiebing.blogspot.ru/2015/12/linux-routing-based-on... well, in the search for iptables mark and ip route mark
The problem is in determining the correct owner, in some cases you can do it by uid, in in some cases, you need to write a script that adds and removes pid in chains