How can I add iptables rules that persist across reboots? I want to add an iptables rule on my Android phone. I used:

iptables -t nat -A PREROUTING -p 6 -d 192.168.66.1 --dport 80 -j DNAT --to 192.168.66.1:808


...as root. This rule can be checked in adb shell, and I can see that it was added: 

# iptables -t nat -nL
chain PREROUTING (policy ACCEPT)
prot   opt    source       destination    idletimer_nat_PREROUTING  
all    --     0.0.0.0/0    0.0.0.0/0      DNAT       
tcp    --     0.0.0.0/0    192.168.66.1   tcp dpt:80 to:192.168.66.1:8080


I want this rule to persist after a reboot, so I added an iptabless file in /etc/sysconfig with these contents:

-t nat -A PREROUTING -p 6 -d 192.168.66.1 --dport 80 -j DNAT --to 192.168.66.1:8080


However, when I reboot my phone, no rule is added.

Does Android support the /etc/sysconfig/iptables path? I got this path from a PC Linux installation ( I tested /etc/iptables/rules.v4 as well, it also did not work).

At the same time, I also don't know whether its content is right.

Additionally, I cannot root my testing phone in the future. Is it possible to add persistent iptables rules on an unrooted phone?
Running scripts at boot (init) as you are trying to do is only supported if the kernel supports it.

If you are using a stock kernel, you may need to install a custom kernel that includes init support.

There are also apps that start with Android and automatically apply firewall/iptables rules, however keep in mind these require root access.

It is not possible to modify iptables rules without root access. However, you can use a VPN connection to route network traffic which works on any Android 4.0+ device without root access.