Enable per-UID network routing like iptables

In most if not all Linux distributions, iptables is used for network routing.

IPTables enables routing per UID like so:

sudo ip rule add uidrange 1001-1001 table user_wlp
sudo ip route add default via 192.168.53.14 table user_wlp

This will set the default route for user "wlp", identified by uid 1001 to the IP address 192.168.53.14 (arbitrary example). The routing table name can be chosen freely, it just needs to be defined in the file /etc/iproute2/rt_tables on Linux.

I am not saying that we need IPTables on AIX, but the functionality is very helpful when using multiple interfaces on one LPAR. While some applications are able to chose their outgoing interface (like `curl --interface <ip/interface/hostname>` or `ssh -b <ip/interface/hostname>`, a lot of products are not able to do this: For IHS (IBM Http Server) and WLP (IBM WebSphere Liberty Profile) only the listen address can be specified, but not the outgoing interfaces. This is particularly hard to implement for IBM, as multiple libraries would be affected: DB drivers (datasources), JAX-RS implementations (Apache CXF, Jersey, Resteasy) and others. The better option would therefore be to set the default routing for a specific user/UID, so every application goes the same route when doing outbound communications.

So this request is asking for an implementation similar to the IPTables implementation where I can set the default gateway for a specific UID.