Docker networking with firewalld

Docker networking

Source: https://stackoverflow.com/questions/40214617/docker-no-route-to-host

# Firewalld settings
1. open all IPs starts with "172" so that all the containers may communicate each other
```shell
$ sudo firewall-cmd --permanent --zone=public --add-rich-rule='rule family=ipv4 source address=172.0.0.0/8 accept'
```

2. make our container able to visit the network outside
```shell
$ sudo firewall-cmd --permanent --zone=public --add-masquerade
```
3. apply the change
```shell
$ sudo firewall-cmd --reload
```