Sharing internet use case

[kaihendry]

Which rules do I use for sharing an Internet connection?

• https://wiki.archlinux.org/index.php/Internet_sharing
• https://bbs.archlinux.org/viewtopic.php?pid=1517864#p1517864

Sidenote: To simple flush iptables, one recommends https://github.com/QueuingKoala/netfilter-samples/blob/master/reset-rules/reset-loaded-nf-tables.sh ? Seems crazy.

[QueuingKoala]

The rules-edge-router is probably what you want; this said, if you're sharing Internet from a system that isn't itself connected to your ISP, you're not technically an "edge router", but the example ruleset uses the MASQUERADE target, which will work if you're issued RFC1918 to the system you're sharing through as well.

So everything should just work for you there, once you tune the example for your own networks. Remember that you might need to add additional rules to permit traffic you expect to work, such as SSH access to your own router, for instance.

[kaihendry]

Thank you for the helpful reply!

Hmmm, it's a shame that https://github.com/QueuingKoala/netfilter-samples/blob/master/rules-edge-router/iptables.rules can't be be populated with the right variables for the interfaces so I could just blindly run (idempotently?) iptables-restore with it. There is also the niggly addition of net.ipv4.ip_forward=1 to worry about.

Being able to run the script idempotently is the feature I'm lacking from my own script: http://ix.io/hWV :/ I'm not sure who can help with ip. Though it seems like resetting iptables is pretty damn hard too.