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+.\"
+.\" $FreeBSD$
+.\"
+.NH
+Future Directions
+.PP
+The jail facility has already been deployed in numerous capacities and
+a few opportunities for improvement have manifested themselves.
+.NH 2
+Improved Virtualisation
+.PP
+As it stands, the jail code provides a strict subset of system resources
+to the jail environment, based on access to processes, files, network
+resources, and privileged services.
+Virtualisation, or making the jail environments appear to be fully
+functional FreeBSD systems, allows maximum application support and the
+ability to offer a wide range of services within a jail environment.
+However, there are a number of limitations on the degree of virtualisation
+in the current code, and removing these limitations will enhance the
+ability to offer services in a jail environment.
+Two areas that deserve greater attention are the virtualisation of
+network resources, and management of scheduling resources.
+.PP
+Currently, a single IP address may be allocated to each jail, and all
+communication from the jail is limited to that IP address.
+In particular, these addresses are IPv4 addresses.
+There has been substantial interest in improving interface virtualisation,
+allowing one or more addresses to be assigned to an interface, and
+removing the requirement that the address be an IPv4 address, allowing
+the use of IPv6.
+Also, access to raw sockets is currently prohibited, as the current
+implementation of raw sockets allows access to raw IP packets associated
+with all interfaces.
+Limiting the scope of the raw socket would allow its safe use within
+a jail, re-enabling support for ping, and other network debugging and
+evaluation tools.
+.PP
+Another area of great interest to the current consumers of the jail code
+is the ability to limit the impact of one jail on the CPU resources
+available for other jails.
+Specifically, this would require that the jail of a process play a rule in
+its scheduling parameters.
+Prior work in the area of lottery scheduling, currently available as
+patches on FreeBSD 2.2.x, might be leveraged to allow some degree of
+partitioning between jail environments \s-2[LOTTERY1] [LOTTERY2]\s+2.
+However, as the current scheduling mechanism is targeted at time
+sharing, and FreeBSD does not currently support real time preemption
+of processes in kernel, complete partitioning is not possible within the
+current framework.
+.NH 2
+Improved Management
+.PP
+Management of jail environments is currently somewhat ad hoc--creating
+and starting jails is a well-documented procedure, but day-to-day
+management of jails, as well as special case procedures such as shutdown,
+are not well analysed and documented.
+The current kernel process management infrastructure does not have the
+ability to manage pools of processes in a jail-centric way.
+For example, it is possible to, within a jail, deliver a signal to all
+processes in a jail, but it is not possibly to atomically target all
+processes within a jail from outside of the jail.
+If the jail code is to effectively limit the behaviour of a jail, the
+ability to shut it down cleanly is paramount.
+Similarly, shutting down a jail cleanly from within is also not well
+defined, the traditional shutdown utilities having been written with
+a host environment in mind.
+This suggests a number of improvements, both in the kernel and in the
+user-land utility set.
+.PP
+First, the ability to address kernel-centric management mechanisms at
+jails is important.
+One way in which this might be done is to assign a unique jail id, not
+unlike a process id or process group id, at jail creation time.
+A new jailkill() syscall would permit the direction of signals to
+specific jailids, allowing for the effective termination of all processes
+in the jail.
+A unique jailid could also supplant the hostname as the unique
+identifier for a jail, allowing the hostname to be changed by the
+processes in the jail without interfering with jail management.
+.PP
+More carefully defining the user-land semantics of a jail during startup
+and shutdown is also important.
+The traditional FreeBSD environment makes use of an init process to
+bring the system up during the boot process, and to assist in shutdown.
+A similar technique might be used for jail, in effect a jailinit,
+formulated to handle the clean startup and shutdown, including calling
+out to jail-local /etc/rc.shutdown, and other useful shutdown functions.
+A jailinit would also present a central location for delivering
+management requests to within a jail from the host environment, allowing
+the host environment to request the shutdown of the jail cleanly, before
+resorting to terminating processes, in the same style as the host
+environment shutting down before killing all processes and halting the
+kernel.
+.PP
+Improvements in the host environment would also assist in improving
+jail management, possibly including automated runtime jail management tools,
+tools to more easily construct the per-jail file system area, and
+include jail shutdown as part of normal system shutdown.
+.PP
+These improvements in the jail framework would improve both raw
+functionality and usability from a management perspective.
+The jail code has raised significant interest in the FreeBSD community,
+and it is hoped that this type of improved functionality will be
+available in upcoming releases of FreeBSD.