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Set up vimage/vnet jail on FreeBSD 8.2

With epair, there are two interfaces created [cci]epair0a[/cci] and [cci]eapir0b[/cci] that are direct connections between each other (like an Ethernet cable). When used with jails using an [cci]ifconfig[/cci] [cci]vnet[/cci] command, one side ([cci]epair0b[/cci] for example) sgoes inside the jail. Since the other side of this virtual direct-connection stays on the outside of the jail, the [cci]epair[/cci] pairs act as an Ethernet tunnel inside/outside the jail. You can use firewall rules either outside the jail or inside the jail to control traffic.

I’m using ezjail-admin with the following patch to /etc/rc.d/jail (taken from the FreeBSD Forums):

[cce lang="diff"]

<               eval ${_setfib} jail ${_flags} -i ${_rootdir} ${_hostname} \
<                       \"${_addrl}\" ${_exec_start} > ${_tmp_jail} 2>&1
>               if [ -z "${_addrl}" ] ; then
>                       eval ${_setfib} jail -i ${_flags} path=${_rootdir} host.hostname=${_hostname} \
>                               command=${_exec_start} > ${_tmp_jail} 2>&1
>               else
>                       eval ${_setfib} jail -i ${_flags} ${_rootdir} ${_hostname} \
>                                 \"${_addrl}\" ${_exec_start} > ${_tmp_jail} 2>&1
>               fi

For example, I have two jails. I create the interfaces like so in [ccie]/etc/rc.conf[/ccie]:


# ezjail with vimage/epair config
cloned_interfaces=”epair0 epair1 bridge0″
ifconfig_bridge0=”name jailbridge addm re0 up”


On the inside of the jail, I just need to set the IP address of the [cci]epair0b[/cci] and [cci]epair1b[/cci] interfaces. I’m using ezjail Here’s a sample [ccie]/usr/local/etc/ezjail/<jail_name>[/ccie], in this case for a subsonic server:


# To specify the start up order of your ezjails, use these lines to
# create a Jail dependency tree. See rcorder(8) for more details.
# PROVIDE: standard_ezjail

# vnet stuff:
export jail_subsonic_flags=”-c vnet name=subsonic”
#export jail_subsonic_exec_prestart0=”ifconfig epair0 create”
#export jail_subsonic_exec_prestart1=”ifconfig epair0a up”

# sometiems rc.conf doesn’t do this:
export jail_subsonic_exec_prestart0=”ifconfig jailbridge addm re0″
export jail_subsonic_exec_prestart1=”ifconfig jailbridge addm epair0a up”
export jail_subsonic_exec_prestart2=”mount_nullfs -o ro /tank/music /usr/jails/subsonic/var/music”
export jail_subsonic_exec_prestart3=”mount_nullfs -o rw /tank/music/Playlists /usr/jails/subsonic/var/playlists”

export jail_subsonic_exec_poststart0=”ifconfig epair0b vnet subsonic”
#export jail_subsonic_exec_poststart1=”jexec subsonic /etc/rc.d/ipfw start”
export jail_subsonic_exec_poststart1=”jexec subsonic ifconfig lo0″
export jail_subsonic_exec_poststart2=”jexec subsonic ifconfig epair0b netmask″
export jail_subsonic_exec_poststart3=”jexec subsonic route add default″
export jail_subsonic_exec_poststop0=”umount /usr/jails/subsonic/var/music”
export jail_subsonic_exec_poststop1=”umount /usr/jails/subsonic/var/playlists”

export jail_subsonic_hostname=”subsonic”
export jail_subsonic_ip=””
export jail_subsonic_rootdir=”/usr/jails/subsonic”
export jail_subsonic_exec_start=”/bin/sh /etc/rc”       # /bin/sh /etc/rc by default
export jail_subsonic_exec_stop=””
export jail_subsonic_mount_enable=”YES”
export jail_subsonic_devfs_enable=”YES”
export jail_subsonic_devfs_ruleset=”devfsrules_jail2″
export jail_subsonic_procfs_enable=”NO”
export jail_subsonic_fdescfs_enable=”NO”
export jail_subsonic_image=””
export jail_subsonic_imagetype=””
export jail_subsonic_attachparams=””
export jail_subsonic_attachblocking=””
export jail_subsonic_forceblocking=””
export jail_subsonic_zfs_datasets=””
export jail_subsonic_cpuset=””
export jail_subsonic_fib=””

Also, don’t forget that you need something like the following within your jail’s [cci]/etc/resolv.conf[/cci]:


I’m using FreeBSD’s IPFW. I have it set up so that it by default passes all packets. I can then control all firewall rules from the host (rather than in the jail). The last line of my host rules is a deny all to implementing the blocking on the host. I leave default rules within the jails (with epair/vnet each jail gets its own firewall rules). I have things set up like:


oif=”re0″       # out interface
jail_brif=”jailbridge”  # jail interface
subsonic_ip=”″ # jail IP
cmd=”/sbin/ipfw -q add ”

$cmd 02000 allow ip from any to any via $oif
$cmd 03300 allow log icmp from $ipdns to $subsonic_ip $ks
$cmd 03310 allow log icmp from $ipdns to $jabber_ip $ks
$cmd 03350 allow log icmp from $subsonic_ip to $ipdns $ks
$cmd 03355 allow log icmp from $jabber_ip to $ipdns $ks
# DNS:
$cmd 03400 allow udp from $subsonic_ip to $ipdns 53 $ks
# subsonic:
$cmd 04500 allow ip from any to $subsonic_ip dst-port 8180 setup $ks
# allow scrobbling (etc):
$cmd 06600 allow log ip from $subsonic_ip to any dst-port 80 setup $ks
$cmd 06700 allow log ip from $subsonic_ip to any dst-port 443 setup $ks
$cmd 65500 deny log ip from any to any

It’s been a while since I set this up, and I’m not sure if the allow all on [cci]$oif[/cci] (command 02000) is really necessary.

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