Add new file

debian:stretch/Dockerfile

+FROM debian:stretch
+
+RUN apt-get update && apt-get -y install host telnet netcat procps net-tools iptables tcpdump && apt-get clean && rm -rf /var/cache/apt/archives /var/lib/apt/lists
+
+EXPOSE 3000 4000 5000 6000
+
+ADD netfilter_gw1.sh /netfilter.sh
+
+CMD [ "/netfilter.sh" ]