Redirect secondary network interface traffic along with port forwarding to tun0 (OpenVPN) using iptables [closed] - iptables

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I have a NAS server which I should do port forwarding for it in order to make its services accessible from internet. However my ISP is blocking ports, so I've managed to buy myself a cheap Ubuntu VPS to run an OpenVPN server there and then somehow redirect the whole NAS traffic and the required ports to there.
My setup is as the following:
+--------------------------------+
| Raspi |
(192.168.0.101/24)| |(192.168.1.1/24)
(192.168.0.1/24) AP<>=================={wlan0 eth0}================<>NAS (192.168.1.102/24)
| \ / |
| +----------------------+ |
| | iptables and | |
| | routing engine | |
| +-----------+----------+ |
| | |
| {tun0} |
| 10.8.0.6 |
+--------------------------------+
The VPS side is configured correctly I guess, as I am able to SSH into my Raspberry Pi using my VPS IP. That's what I've done there in order to make it work:
iptables -t nat -A PREROUTING -d A.B.C.D -p tcp --dport 22 -j DNAT --to-dest 10.8.0.6:22
iptables -t nat -A POSTROUTING -d 10.8.0.6 -p tcp --dport 22 -j SNAT --to-source 10.8.0.1
My OpenVPN server config:
port X
proto udp
dev tun
ca ca.crt
cert server.crt
key server.key
dh dh2048.pem
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
client-config-dir ccd
push "redirect-gateway def1 bypass-dhcp"
push "dhcp-option DNS 208.67.222.222"
push "dhcp-option DNS 208.67.220.220"
keepalive 10 120
comp-lzo
user nobody
group nogroup
persist-key
persist-tun
status openvpn-status.log
verb 3
I have also done:
sysctl -w net.ipv4.ip_forward=1
and put DEFAULT_FORWARD_POLICY="ACCEPT" in /etc/default/ufw and also added
# START OPENVPN RULES
# NAT table rules
*nat
:POSTROUTING ACCEPT [0:0]
# Allow traffic from OpenVPN client to eth0
-A POSTROUTING -s 10.8.0.0/8 -o eth0 -j MASQUERADE
COMMIT
# END OPENVPN RULES
to
/etc/ufw/before.rules
OpenVPN client config:
client
dev tun
proto udp
remote A.B.C.D X
resolv-retry infinite
nobind
user nobody
group nogroup
persist-key
persist-tun
ns-cert-type server
comp-lzo
verb 3
<ca>
XXX
</ca>
<cert>
YYY
</cert>
<key>
ZZZ
</key>
How do I redirect eth0 traffic to tun0 and forward ports Y and Z through the tunnel?
I just know that for the other ports I should reconfigure my VPS accordingly as I did for port 22.

Answer 1

I've managed to redirect the traffic on my Raspi with the following command:
iptables -t nat -A POSTROUTING -s 192.168.1.0/24 -o tun0 -j MASQUERADE
When I traceroute out of my NAS it goes through the tunnel. Now I only need to forward ports in this tunnel.
UPDATE (solving the whole project):
I finally found the correct port forwarding commands after hours of searching. I've ran the following commands on my Raspi:
iptables -t nat -I PREROUTING -p tcp -i tun0 -d 10.8.0.6 --dport <port> -j DNAT --to 192.168.1.102:<port>
iptables -I FORWARD -p tcp -i tun0 -d 192.168.1.102 --dport <port> -j ACCEPT
And also these commands on my VPS as I've done at first for port 22 at the beginning of this thread:
iptables -t nat -A PREROUTING -d 217.160.14.45 -p tcp --dport <port> -j DNAT --to-dest 10.8.0.6:<port>
iptables -t nat -A POSTROUTING -d 10.8.0.6 -p tcp --dport <port> -j SNAT --to-source 10.8.0.1
So now I've bypassed the firewall of my ISP and I am able to access my NAS and its services using port forwarding on the VPS side. You can use this as a tutorial :)