fx setup-firewall

Setup Linux firewall via iptables to allow Fuchsia device and emulator traffic.

This command detects whether iptables is installed,
and if so, will add special rules to allow Fuchsia-specific traffic to
go through the link-local IPv6 network interfaces used by Fuchsia devices
and emulators. If `ufw` (Uncomplicated Firewall) is installed on the system,
we will abort, and recommend the script `fx setup-ufw`.

NOTE: This script uses sudo and will thus ask for your password!

  -n|--dry-run         Just print all steps, don't do any configuration
  -u|--undo            Remove all firewall rules installed by this script