Linux routing issues with tun0

Question

I am attempting to get hanstunnel (IP over ICMP) to work on my VPS

I have:

• Ubuntu 16 VPS with:
  • ens3 a.b.c.d (external ip)
  • tun0 10.0.0.1
• Ubuntu 16 VirtualBox with:
  • enp0s3 192.168.1.1
  • tun0 10.0.0.100

VPS is running:

#!/bin/bash
sudo sysctl net.ipv4.icmp_echo_ignore_all=1
sysctl -w net.ipv4.ip_forward=1
sudo hans -r -s 10.0.0.1 -u hans -p supersecurepassword -d tun0

VM is running:

#!/bin/bash
sudo hans -r -c a.b.c.d -p supersecurepassword

I can:

• ping a.b.c.d from vm (using VPS's external address)
• connect hans (both client and server agree they are connected)

Doesnt work:

• ping VPS(10.0.0.1) from VM(10.0.0.100) tcpdump on VPS says ping is being recieved and responded to but VM never gets responce
• ping VM(10.0.0.100) from VPS(10.0.0.1) tcpdump on VPS says ping is being sent but VM never receives anything

route -v on both devices has the following entry:

10.0.0.0        *               255.255.255.0   U     0      0        0 tun0

I am fairly certain the issue is on the VPS and could have something to do with how traffic on tun0 is being handled. This could be an issue with iptables (of which I am a complete novice).

I am looking for advice on how to further troubleshoot this issue and/or thoughts on what may be wrong with my setup.