openvpn iptables bypass flow

#/bin/bash

server_IP=123.45.67.89

[ -r chnroute.txt ] || curl 'http://ftp.apnic.net/apnic/stats/apnic/delegated-apnic-latest' | grep ipv4 | grep CN | awk -F\| '{ printf("%s/%d\n", $4, 32-log($5)/log(2)) }' > chnroute.txt

sudo iptables -t nat -N SHADOWSOCKS
sudo iptables -t nat -A PREROUTING -s 10.8.0.0/24 -p tcp -j SHADOWSOCKS
sudo iptables -t nat -A PREROUTING -s 10.8.0.0/24 -p udp -j SHADOWSOCKS
sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

sudo iptables -t nat -A SHADOWSOCKS -d $server_IP -j RETURN

sudo iptables -t nat -A SHADOWSOCKS -d 0.0.0.0/8 -j RETURN
sudo iptables -t nat -A SHADOWSOCKS -d 10.0.0.0/8 -j RETURN
sudo iptables -t nat -A SHADOWSOCKS -d 127.0.0.0/8 -j RETURN
sudo iptables -t nat -A SHADOWSOCKS -d 169.254.0.0/16 -j RETURN
sudo iptables -t nat -A SHADOWSOCKS -d 172.16.0.0/12 -j RETURN
sudo iptables -t nat -A SHADOWSOCKS -d 192.168.0.0/16 -j RETURN
sudo iptables -t nat -A SHADOWSOCKS -d 224.0.0.0/4 -j RETURN
sudo iptables -t nat -A SHADOWSOCKS -d 240.0.0.0/4 -j RETURN

sudo ipset create chnroute hash:net
cat chnroute.txt | sudo xargs -I ip ipset add chnroute ip
sudo iptables -t nat -A SHADOWSOCKS -m set --match-set chnroute dst -j RETURN

sudo iptables -t nat -A SHADOWSOCKS -p tcp -j REDIRECT --to-ports 1091
sudo iptables -t nat -A SHADOWSOCKS -p udp -j REDIRECT --to-ports 1091
#1091为ss-redir监听端口