FreeBSD Jail Access Private Network Via NAT and PF

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In FreeBSD, a jail is a form of virtualization that allows you to partition a FreeBSD system into smaller, self-contained environments. Each jail has its own network stack, file system, and processes, making it an ideal solution for building isolated and secure environments. In some cases, you may need to allow the jail to access resources on the private network. This can be accomplished using NAT and PF.

Here’s how you can configure NAT and PF to allow a FreeBSD jail to access resources on the private network:

  1. Enable IP forwarding by adding the following line to /etc/sysctl.conf:
    net.inet.ip.forwarding=1

    You can apply this change by running sysctl -w net.inet.ip.forwarding=1.

  2. Create a bridge interface by adding the following lines to /etc/rc.conf:
    cloned_interfaces="bridge0"
    ifconfig_bridge0="addm em0 addm tap0 up"

    This assumes that em0 is your physical interface and tap0 is your jail interface. Replace these with the appropriate interface names for your system.

  3. Install and configure PF by adding the following lines to /etc/pf.conf:
    nat on em0 from bridge0:network to any -> em0
    pass from { lo0, em0 } to { lo0, em0 }
    pass from bridge0:network to any

    This configures NAT to allow the jail to access resources on the private network, and enables traffic between the jail, the host system, and the private network.

  4. Start the bridge interface and PF by running the following commands:
    service netif start bridge0
    service pf start

    These commands will start the bridge interface and PF, and apply the changes you made to the configuration files.

  5. Start the jail with the appropriate IP address, netmask, and default gateway. For example:
    jail -c vnet name=myjail \
    persist \
    vnet.interface=epair0b \
    vnet.private.bridge=bridge0 \
    vnet.public.0.ip4.addr=192.168.1.10 \
    vnet.public.0.ip4.netmask=255.255.255.0 \
    vnet.public.0.gateway=192.168.1.1 \
    allow.raw_sockets

    This assumes that epair0b is the virtual interface for the jail. Replace this with the appropriate interface name for your system.

That’s it! With these configuration changes, your jail should be able to access resources on the private network via NAT and PF.

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