# enable IP forwarding
sudo sysctl -w net.inet.ip.forwarding=1
# enable PF firewall
sudo pfctl -e
# Option 1: add NAT rule after en4 is up (USB armory already plugged and started)
echo "nat on en0 from en4:network to any -> (en0)" | sudo pfctl -f -
# Option 2: add NAT rule before USB armory is plugged, requires specifying its network
echo "nat on en0 from 10.0.0.0/8 to any -> (en0)" | sudo pfctl -f -