Eu resolvi adicionando regras ao iptables
sudo sysctl -w net.ipv4.ip_forward=1
iptables -A FORWARD -i <interface without internet> -o <interface with internet> -j ACCEPT
iptables -A FORWARD -i <interface with internet> -o <interface without internet> -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -t nat -A POSTROUTING -o <interface with internet> -j MASQUERADE