iptables -A FORWARD -i nm-net -j ACCEPT; iptables ...
# general
b
iptables -A FORWARD -i nm-net -j ACCEPT; iptables -t nat -A POSTROUTING -o nm-net -j MASQUERADE; iptables -A FORWARD -i nm-net -j ACCEPT; iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE