#!/bin/bash

iprt=$1
oprt=$2
oipa=$3

#echo 1 > /proc/sys/net/ipv4/ip_forward
#iptables -F
#iptables -t nat -F
iptables -t nat -A PREROUTING -p tcp --dport $iprt -j DNAT --to-destination $oipa:$oprt
#sudo iptables -t nat -A POSTROUTING -j MASQUERADE
#sudo iptables -t nat -L -n -v
#sudo iptables-persistent

sudo sysctl -w net.ipv4.ip_forward=1
sudo nft add table ip nat
sudo nft add chain ip nat prerouting { type nat hook prerouting priority -100 \; }
sudo nft add chain ip nat postrouting { type nat hook postrouting priority 100 \; }
sudo nft add rule ip nat prerouting tcp dport $iprt dnat to $oipa:$oprt
sudo nft add rule ip nat postrouting ip daddr $oipa masquerade
sudo nft list ruleset | sudo tee /etc/nftables/port-forwarding.nft