Ubuntu Fan Updates for Trusty and Vivid

[Andy Whitcroft]

We would like to update the Ubuntu Fan functionality in 15.04, and
enable that same functionality in 14.04 LTS for the next point release
(August 6th 2015).  While discussing this with the SRU team it was felt
that the changes required would be greater than that normally justified
under an SRU and further authorisation from the Tech Board should be
sought.

The Ubuntu Fan driver is an IPv4 address multiplication mechanism.  It
allows a group of host machines to participate in an expanded address
space with hundreds (potentially thousands) of directly addressable
addresses per host.  These are intended to allow direct communication
between individual host containers and virtual machines.

The 15.04 kernel already carries a technology preview of the Ubuntu Fan
driver, and 15.04 contains minimal userspace support to allow simple
creation of a single Fan address range.  The proposed changes eliminate
a limitation of one Fan address range per local IP address.  They also
bring a new utility interface to abstract creation of these Fan address
ranges insulating the consumer from the underlying implementation.  (The
Fan is an abstract concept and while currently implemented using IPIP
tunnels it may be appropriate in the future to change, for example, the
encapsulation to suit different cloud substrates.)  We believe it is
necessary to SRU these changes into 14.04 LTS as the functionality they
represent is particularly valuable in container hosts which typically
run stable releases.  It also represents a bridging technology until
IPv6 technology is ubiquitously available, and so is particularly
valuable in the near term.

As the 14.04 LTS point release will contain the 15.04 LTS backport
kernel we propose to apply the Ubuntu Fan changes currently in Wily to
the 15.04 kernel, and thereby the 15.04 LTS backport kernel in 14.04
LTS.  We also propose to apply the corresponding changes for the
iproute2 package in lock step in both 15.04 and 14.04 LTS.  Finally we
propose to update the ubuntu-fan package in 15.04 and introduce it in
14.04 LTS.  It should be noted that we will have to SRU the existing
changes to iproute2 from 15.04 into 14.04 LTS to handle the existing
Ubuntu Fan functionality in the kernel planned for the upcoming point
release.  We do not intend to update 14.10 as it is within weeks of end
of life.

With these in place we end up with harmonised Ubuntu FAN support in
14.04 and later.  We also insulate the consumers of this functionality
from later changes as this feature further develops moving forward
towards 16.04 LTS.

These changes should present a reasonably low risk overall.  The feature
we are modifying was a never announced technology preview.  (The
announced test images for this utilised the proposed updated versions
and interfaces.)  The kernel updates apply to an isolated driver
component only activated when Fan address ranges are configured.  The
iproute2 changes introduce new interfaces specifiers which would not
normally exist.  The ubuntu-fan package is benign when installed until
configured.

Packages with these changes applied can be found in the PPA below:

    ppa:apw/ubuntu/charmers-sru

We are requesting permission to SRU these packages into Ubuntu in time
for the upcoming 14.04 LTS point release in August.  Thank you in
advance for considering this request.

-apw