How to configure Centos 7 firewallD to allow docker containers free access to the host's network ports?

Question

I have docker installed on CentOS 7 and I am running firewallD.

From inside my container, going to the host (default 172.17.42.1)

With firewall on

container# nc -v  172.17.42.1  4243
nc: connect to 172.17.42.1 port 4243 (tcp) failed: No route to host

with firewall shutdown

container# nc -v  172.17.42.1  4243
Connection to 172.17.42.1 4243 port [tcp/*] succeeded!

I've read the docs on firewalld and I don't fully understand them. Is there a way to simply allow everything in a docker container (I guess on the docker0 adapter) unrestricted access to the host?

Answer 1

Maybe better than earlier answer;

firewall-cmd --permanent --zone=trusted --change-interface=docker0
firewall-cmd --permanent --zone=trusted --add-port=4243/tcp
firewall-cmd --reload

Answer 2

Theses commands did the trick:

firewall-cmd --permanent --zone=trusted --add-interface=docker0
firewall-cmd --permanent --zone=trusted --add-port=4243/tcp