*libvirt* iptables rules can be manually managed for a specified network
*libvirt* automatically generates and applies iptables rules
appropriate for each type of network it creates. The rules are controlled by `forward mode` in the configuration of each network. Previously, there was no way for users to disable these automatically generated iptables rules and manually manage the iptables rules. In the current release, the `open` network `forward mode` was added. When specified for a network, *libvirt* does not generate any iptables rules for the network. As a result, iptables rules added outside the scope of *libvirt* are not disrupted and users can manually manage iptables rules.