App-Route-Jail | force application-specific routing | Router library

I got two network interfaces (ethernet and wlan). Now I found a little script on github (https://github.com/Intika-Linux-Firewall/App-Route-Jail) which seems to allow me to route specific applications through the none default gateway to loadbalance the traffic a little bit.

The script is using the following call: setsockopt(sd, SOL_SOCKET, SO_MARK, &mark, sizeof(mark));

As I found out via an strace I got: '-1 EPERM Permission denied' (as show on http://man7.org/linux/man-pages/man7/capabilities.7.html this command needs cap_net_admin rights) The tool works when I use "sudo" infront of the command the socket is created with the none default gateway and works like intended (e.g. wget a file)

Example: MARK=10 LD_PRELOAD=./mark.so wget -qO- ifconfig.me uses the default gateway (so not what I wanted) sudo MARK=10 LD_PRELOAD=./mark.so wget -qO- ifconfig.me returns the IP of the none default gateway (what I want but without using sudo)

Some things I found on the internet and tried:

• Setting File Capabilities (setcap cap_net_admin+eip) (still requires root somehow)
• Using SUID Bit (chmod u+s) (no change at all)

I expect the command to run without root privileges, so every application can use the none default gateway, but currently I need to use sudo to gain enough permissions to run the command on the correct interface. What am I missing to archive my goals?