Network Requirements

Here’s the scenario. You’ve installed Bastille at home or in the cloud and want to get started putting applications in secure little containers, but how do I get these containers on the network?

Bastille tries to be flexible about how to network containerized applications. Three methods are described here. Consider each options when deciding which design work best for your needs. One of the methods works better in the cloud while the others are simpler if used in local area networks.

Note: if you are running in the cloud and only have a single public IP you may want the Public Network option. See below.

Local Area Network

I will cover the local area network (LAN) method first. This method is simpler to get going and works well in a home network (or similar) where adding alias IP addresses is no problem.

Shared Interface (IP alias)

In FreeBSD network interfaces have different names, but look something like em0, bge0, re0, etc. On a virtual machine it may be vtnet0. You get the idea…

Bastille allows you to define the interface you want the IP attached to when you create it. An example:

bastille create alcatraz 13.1-RELEASE 192.168.1.50 em0

When the alcatraz container is started it will add 192.168.1.50 as an IP alias to the em0 interface. It will then simply be another member of the hosts network. Other networked systems (firewall permitting) should be able to reach services at that address.

This method is the simplest. All you need to know is the name of your network interface and a free IP on your current network.

Bastille tries to verify that the interface name you provide it is a valid interface. It also checks for a valid syntax IP4 or IP6 address.

Virtual Network (VNET)

(Added in 0.6.x) VNET is supported on FreeBSD 12+ only.

Virtual Network (VNET) creates a private network interface for a container. This includes a unique hardware address. This is required for VPN, DHCP, and similar containers.

To create a VNET based container use the -V option, an IP/netmask and external interface.

bastille create -V azkaban 13.1-RELEASE 192.168.1.50/24 em0

Bastille will automagically create the bridge interface and connect / disconnect containers as they are started and stopped. A new interface will be created on the host matching the pattern interface0bridge. In the example here, em0bridge.

The em0 interface will be attached to the bridge along with the unique container interfaces as they are started and stopped. These interface names match the pattern eXb_bastilleX. Internally to the containers these interfaces are presented as vnet0.

VNET also requires a custom devfs ruleset. Create the file as needed on the host system:

## /etc/devfs.rules (NOT .conf)

[bastille_vnet=13]
add path 'bpf*' unhide

Lastly, you may want to consider these three sysctl values:

net.link.bridge.pfil_bridge=0
net.link.bridge.pfil_onlyip=0
net.link.bridge.pfil_member=0

Regarding Routes

Bastille will attempt to auto-detect the default route from the host system and assign it to the VNET container. This auto-detection may not always be accurate for your needs for the particular container. In this case you’ll need to add a default route manually or define the preferred default route in the bastille.conf.

bastille sysrc TARGET defaultrouter=aa.bb.cc.dd
bastille service TARGET routing restart

To define a default route / gateway for all VNET containers define the value in bastille.conf:

bastille_network_gateway=aa.bb.cc.dd

This config change will apply the defined gateway to any new containers. Existing containers will need to be manually updated.

Virtual Network (VNET) on External Bridge

To create a VNET based container and attach it to an external, already existing bridge, use the -B option, an IP/netmask and external bridge.

bastille create -B azkaban 13.1-RELEASE 192.168.1.50/24 bridge0

Bastille will automagically create the interface, attach it to the specified bridge and connect / disconnect containers as they are started and stopped. The bridge needs to be created/enabled before creating and starting the jail.

Public Network

In this section I’ll describe how to network containers in a public network such as a cloud hosting provider (AWS, digital ocean, vultr, etc)

In the public cloud you don’t often have access to multiple private IP addresses for your virtual machines. This means if you want to create multiple containers and assign them all IP addresses, you’ll need to create a new network.

loopback (bastille0)

What I recommend is creating a cloned loopback interface (bastille0) and assigning all the containers private (rfc1918) addresses on that interface. The setup I develop on and use Bastille day-to-day uses the 10.0.0.0/8 address range. I have the ability to use whatever address I want within that range because I’ve created my own private network. The host system then acts as the firewall, permitting and denying traffic as needed.

I find this setup the most flexible across all types of networks. It can be used in public and private networks just the same and it allows me to keep containers off the network until I allow access.

Having said all that here are instructions I used to configure the network with a private loopback interface and system firewall. The system firewall NATs traffic out of containers and can selectively redirect traffic into containers based on connection ports (ie; 80, 443, etc.)

First, create the loopback interface:

ishmael ~ # sysrc cloned_interfaces+=lo1
ishmael ~ # sysrc ifconfig_lo1_name="bastille0"
ishmael ~ # service netif cloneup

Second, enable the firewall:

ishmael ~ # sysrc pf_enable="YES"

Create the firewall rules:

/etc/pf.conf

ext_if="vtnet0"

set block-policy return
scrub in on $ext_if all fragment reassemble
set skip on lo

table <jails> persist
nat on $ext_if from <jails> to any -> ($ext_if:0)
rdr-anchor "rdr/*"

block in all
pass out quick keep state
antispoof for $ext_if inet
pass in inet proto tcp from any to any port ssh flags S/SA modulate state
  • Make sure to change the ext_if variable to match your host system interface.
  • Make sure to include the last line (port ssh) or you’ll end up locked out.

Note: if you have an existing firewall, the key lines for in/out traffic to containers are:

nat on $ext_if from <jails> to any -> ($ext_if)

The nat routes traffic from the loopback interface to the external interface for outbound access.

rdr-anchor "rdr/*"

The rdr-anchor “rdr/*” enables dynamic rdr rules to be setup using the bastille rdr command at runtime - eg.

bastille rdr <jail> tcp 2001 22 # Redirects tcp port 2001 on host to 22 on jail
bastille rdr <jail> udp 2053 53 # Same for udp
bastille rdr <jail> list        # List dynamic rdr rules
bastille rdr <jail> clear       # Clear dynamic rdr rules

Note that if you are redirecting ports where the host is also listening (eg. ssh) you should make sure that the host service is not listening on the cloned interface - eg. for ssh set sshd_flags in rc.conf

sshd_flags=”-o ListenAddress=<hostname>”

Finally, start up the firewall:

ishmael ~ # service pf restart

At this point you’ll likely be disconnected from the host. Reconnect the ssh session and continue.

This step only needs to be done once in order to prepare the host.