RFC: New FreeBSD support model

[Gavin Atkinson]

Hi all,

Over the past year or so, many discussions have been had both internally 
and with vendors about the current FreeBSD support model, and how it could 
be improved to better suit the (often conflicting) needs of downstream 
vendors.

Below is our current draft of the new support model.  I'm sending this to 
you as you represent a good cross-section of different downstream users of 
FreeBSD.  We're aiming to make these changes soon, and are interested in 
knowing what else a consumer of FreeBSD, like your company, might need to 
know in order to have a smoother transition.  Michael, I'm including you 
for any insight you may wish to offer from your recent efforts in 
researching FreeBSD sysadmin-y things.

Thanks,

Gavin


Changes to the FreeBSD Support Model
-----------------------------------------------------------------------

Over the past several months, the teams responsible for supporting the
FreeBSD operating system discussed the current support model, and how
that model can be improved to provide better support for FreeBSD users
and consumers.

The changes below greatly improve FreeBSD support, reduce turnaround time 
for Errata Notices and Security Advisories, provide consistency between 
binary package sets and the underlying FreeBSD base system version, and 
reduce the amount of time before new features are included in the official 
FreeBSD binary package sets.


Changes Proposed in a New FreeBSD Support Model
-----------------------------------------------------------------------

The proposed changes include:

- Moving from a point release-based support model to a set of releases
  from a branch with a guaranteed support lifetime.

- Resolving our arbitrary (and unofficial) 5-year branch lifetime 
  guarantee.  The support policy is that the stable/X branch will be 
  supported for 5 years (minimum) from the point X.0-RELEASE is released.  
  We now guarantee a 5-year lifetime on the branch, regardless of how many 
  releases are built from the branch. Additionally, a "last minute" 
  release from the stable/X branch does not constitute expanding the support 
  lifetime for the branch as a whole for an additional two years.

- The Security Officer or Ports Management Team may extend support for any 
  individual numbered release or branch at their discretion, in 
  exceptional cases.

- A new stable/ branch release will not occur before two years after the 
  X.0-RELEASE from the prior branch.  This limits the number of 
  simultaneous supported branches, which will greatly reduce the overall 
  number of branches that must be maintained and build-tested for 
  Security Advisories and Errata Notices, reducing turnaround time.

- Each new release from the stable/X branch deprecates the previous 
  release on the branch, providing a three-month window within which 
  consumers are urged to upgrade to the latest release.  During this 
  three-month window, Security Advisories and Errata Notices will still 
  be issued for the previous release, as necessary.


How These Changes Benefit FreeBSD Consumers
-----------------------------------------------------------------------

These changes to the FreeBSD support policy will reduce turnaround time  
for security advisories and errata notices, provide binary package sets 
that are more closely aligned with the latest FreeBSD release from a given 
branch, and clearly define the minimum length of time that a branch will 
receive support.


When The New FreeBSD Support Policy Will Become Effective
-----------------------------------------------------------------------

These changes are planned to become effective with FreeBSD 11.0-RELEASE,
which is still a number of months away.

FreeBSD releases from earlier branches will continue to be supported in 
accordance with the policy that was in effect at the time they were 
released.


Deficiencies in the Current FreeBSD Support Model
-----------------------------------------------------------------------

- The FreeBSD support model is release-based, versus branch-based. 
  Specifically, we determine if a FreeBSD release will be a normal- or an 
  extended-support release in the final phases of the release cycle, while 
  in reality we have no way to determine how successful the release is 
  until weeks or months later.

- We do not clearly define how long the stable/X branch will be supported 
  after its creation.  Since FreeBSD 5.x, we have historically supported a 
  stable/X branch for a minimum of five years after the X.0-RELEASE is 
  available.  The length of time is not a defined policy, which can make 
  it difficult to decide which branch to track.

- The current support model prevents building third-party binary packages 
  for the most recent release from a stable/ branch because we must 
  provide packages that can be run on the oldest supported release from 
  the branch.

- Ports maintainers must support the oldest supported release on the 
  branch within the Ports Collection. This adds significant complexity to 
  the tree in general, but also prevents enabling new features by default.  
  An example is the upgrade to WITH_NEW_XORG where these features depend
  on changes to the base system that are only available in X.Z-RELEASE.

- The support model can overlap in non-intuitive ways, making it difficult 
  to decide when evaluating FreeBSD features versus support timeframe from 
  any given branch.  When changes to the support model were initially 
  being discussed, the FreeBSD supported releases were:
  - 8.4-RELEASE: June 30, 2015
  - 9.1-RELEASE: December 31, 2014
  - 9.2-RELEASE: September 30, 2014

  (Note that in this case support for the newer 9.2 release ends before 
  support for FreeBSD 9.1.)

- A new release from a branch automatically extends the support lifetime 
  by two years, minimum.  If X.Y-RELEASE was initially planned to be the 
  final release from the stable/X branch, it is an extended-support 
  release by definition.  If it is necessary to follow X.Y-RELEASE with 
  X.Z-RELEASE for any reason, we would have two concurrent 
  extended-support releases from the same branch in sequence. This has a 
  serious impact on the quality of an update when there are multiple 
  supported releases on a branch. The problem becomes worse when the 
  oldest supported release on the branch has a longer support lifetime 
  than the newest release on the branch.


Key Items Considered in Changes to the FreeBSD Support Model
-----------------------------------------------------------------------

Some of the things that should be included in a new FreeBSD support
model include:

- Guaranteeing, and explicitly stating, the support lifetime of the 
  stable/X branch as a whole, versus independently determining the 
  support lifetime of the individual releases from the stable/X branch.
- Providing package sets that are compatible with the latest release from 
  the branch, ensuring that new features introduced into the FreeBSD base 
  system can be enabled by default in binary package builds.
- Security Advisories and Errata Notices should be more aligned between 
  src/ and ports/.  There is an endless list of edge cases with this 
  particular point, but consider a situation where a critical security 
  vulnerability is discovered, and the underlying code has changed between 
  X.Y-RELEASE and X.Z-RELEASE.  In addition to the possibility of 
  regression in one (or both) of the supported releases due to subtle 
  changes in the security fix, it introduces potential delay in providing 
  the security fix as the number of supported releases increases.  Each 
  supported release adds to the amount of time it takes for:

  - 1) patching the vulnerability,
  - 2) testing the patch,
  - 3) verifying the patch is correct, and
  - 4) building the freebsd-update(8) binary update bits.

  If a problem is discovered at any time during step (4), procedure resets 
  to step (1).  (It should be stressed that this is not due to lack of 
  hardware, but the order in which the various steps of issuing Security 
  Advisories and Errata Notices must occur.)

- Providing a support model that is easier more predictable and easier to 
  follow.