pve-firewall/debian/README

Experimental software, only used for testing!
=============================================


Quick Intro
===========

VM firewall rules are read from:

 /etc/pve/firewall/<VMID>.fw

Cluster wide rules and security group are read from:
 
 /etc/pve/firewall/cluster.fw

Host firewall rules are read from:

  /etc/pve/local/host.fw

You can find examples in the example/ dir


Use the following command to mange the firewall:

To test the firewall configuration:

./pvefw compile

To start or update the firewall:

./pvefw start

To update the firewall rules (the firewall is not started if it
is not already running):

./pvefw update

To stop the firewall:

./pvefw stop


Implementation details
======================

We write iptables rules directly, an generate the following chains 
as entry points in the 'forward' table:

PVEFW-INPUT
PVEFW-OUTPUT
PVEFW-FORWARD

We do not touch other (user defined) chains.

Each VM can have its own firewall definition file in 

/etc/pve/firewall/<VMID>.fw

That file has a section [RULES] to define firewall rules.

Format is: TYPE ACTION IFACE SOURCE DEST PROTO D-PORT S-PORT

* TYPE: IN|OUT|GROUP 
* ACTION: action or macro
* IFACE: vm network interface (net0 - net5), or '-' for all interfaces
* SOURCE: source IP address, or '-' for any source
* DEST: dest IP address, or '-' for any destination address
* PROTO: see /etc/protocols
* D-PORT: destination port
* S-PORT: source port

A rule for inbound traffic looks like this:

IN SSH(ACCEPT) net0

Outbound rules looks like:

OUT SSH(ACCEPT)

Problems
===================

There are a number of restrictions when using iptables to filter
bridged traffic. The physdev match feature does not work correctly
when traffic is routed from host to bridge:

  * when a packet being sent through a bridge entered the firewall on 
    another interface and was being forwarded to the bridge.

  * when a packet originating on the firewall itself is being sent through 
    a bridge.

We use a second bridge for each interface to avoid above problem.

eth0-->vmbr0<--tapXiY (non firewalled tap)
            <--linkXiY-->linkXiYp-->fwbrXiY-->tapXiY (firewalled tap)