Ok, so you have Docker in place. There are two courses of action.
Let Docker maintain its own rules in the DOCKER chain (opening the mapped ports to the world). For that, you need to tweak your rules so it does not interfere with the DOCKER, DOCKER-ISOLATION chains nor the nat table (and possibly mangle?) maintained by the Docker daemon, and keep a reference of those chains into the FORWARD chain.
Note. We have to avoid wiping out the entire table because the iptables-restore command will conflict with the Docker daemon: you would have to restart it after you apply your own firewall rules, with the unpleasant effect of stopping all the containers.
The main table automatically maintained by Docker
Chain INPUT (policy ACCEPT) target prot opt source destination Chain FORWARD (policy ACCEPT) target prot opt source destination DOCKER-ISOLATION all -- anywhere anywhere DOCKER all -- anywhere anywhere ACCEPT all -- anywhere anywhere ctstate RELATED,ESTABLISHED ACCEPT all -- anywhere anywhere ACCEPT all -- anywhere anywhere Chain OUTPUT (policy ACCEPT) target prot opt source destination Chain DOCKER (1 references) target prot opt source destination Chain DOCKER-ISOLATION (1 references) target prot opt source destination RETURN all -- anywhere anywhere
The nat table automatically maintained by Docker
Chain PREROUTING (policy ACCEPT) target prot opt source destination DOCKER all -- anywhere anywhere ADDRTYPE match dst-type LOCAL Chain INPUT (policy ACCEPT) target prot opt source destination Chain OUTPUT (policy ACCEPT) target prot opt source destination DOCKER all -- anywhere !127.0.0.0/8 ADDRTYPE match dst-type LOCAL Chain POSTROUTING (policy ACCEPT) target prot opt source destination MASQUERADE all -- 172.17.0.0/16 anywhere Chain DOCKER (2 references) target prot opt source destination RETURN all -- anywhere anywhere
The workaround
# let Docker do its job iptables -A FORWARD -j DOCKER-ISOLATION iptables -A FORWARD -o docker0 -j DOCKER iptables -A FORWARD -o docker0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT iptables -A FORWARD -i docker0 -j ACCEPT #iptables -A FORWARD -i docker0 ! -o docker0 -j ACCEPT #iptables -A FORWARD -i docker0 -o docker0 -j ACCEPT
read about preventing it from managing its rules and take over the shit
vi /etc/default/docker DOCKER_OPTS=--iptables=false ps auxww | grep dockerd systemctl restart docker ps auxww | grep dockerd
so you can now play with your own rules but you need to take care of what dockerd needs
-A FORWARD -i docker0 -o INTERFACE -j ACCEPT -A FORWARD -i INTERFACE -o docker0 -j ACCEPT -A FORWARD -p tcp -m state --state NEW --dport 80 -j ACCEPT -A FORWARD -p tcp -m state --state NEW --dport 443 -j ACCEPT
preferably open only the ports you’ve reverse-proxied already
draft
Also allow the containers to access internet using NAT
sysctl net.ipv4.conf.all.forwarding sysctl net.ipv4.conf.all.forwarding=1 vi /etc/iptables.rules *nat __TODO__ COMMIT
To clean up your rules (esp. in the DOCKER chain that we do not want to flush),
iptables -L DOCKER -n | grep ^REJECT | awk '{print $4}' | uniq
for ip in `iptables -L DOCKER -n | grep ^REJECT | awk '{print $4}' | uniq`; do echo -n $ip...; iptables -D DOCKER -s $ip -j REJECT && echo done; done; unset ip
iptables -L DOCKER -n | grep ^REJECT | awk '{print $4}' | uniq
iptables -L DOCKER -n | grep ^RETURN | awk '{print $4}' | uniq
for ip in `iptables -L DOCKER -n | grep ^RETURN | awk '{print $4}' | uniq`; do echo -n $ip...; iptables -D DOCKER -s $ip -j RETURN && echo done; done; unset ip
iptables -L DOCKER -n | grep ^RETURN | awk '{print $4}' | uniq
iptables -L DOCKER -n | grep ^DROP | awk '{print $4}' | uniq
for ip in `iptables -L DOCKER -n | grep ^DROP | awk '{print $4}' | uniq`; do echo -n $ip...; iptables -D DOCKER -s $ip -j DROP && echo done; done
iptables -L DOCKER -n | grep ^DROP | awk '{print $4}' | uniq
So in the end if you got only one container running with e.g. ports 25 143 597 up,
Chain DOCKER (1 references) target prot opt source destination ACCEPT tcp -- 0.0.0.0/0 172.17.0.X tcp dpt:587 ACCEPT tcp -- 0.0.0.0/0 172.17.0.X tcp dpt:143 ACCEPT tcp -- 0.0.0.0/0 172.17.0.X tcp dpt:25
Understanding Docker Networking Drivers and their use cases https://blog.docker.com/2016/12/understanding-docker-networking-drivers-use-cases/