Signed-off-by: Manuel Franceschini <livew...@google.com> --- This is a first draft. Please let me know if the overall structure is ok and if you think there is some important sections missing.
Thanks, Manuel. doc/design-2.3.rst | 82 +++++++++++++++++++++++++++++++++++++++++++++++++++- 1 files changed, 81 insertions(+), 1 deletions(-) diff --git a/doc/design-2.3.rst b/doc/design-2.3.rst index efd8bf2..482b624 100644 --- a/doc/design-2.3.rst +++ b/doc/design-2.3.rst @@ -15,11 +15,91 @@ As for 2.1 and 2.2 we divide the 2.3 design into three areas: - core changes, which affect the master daemon/job queue/locking or all/most logical units - logical unit/feature changes -- external interface changes (eg. command line, os api, hooks, ...) +- external interface changes (e.g. command line, os api, hooks, ...) Core changes ------------ +IPv6 support +~~~~~~~~~~~~ + +Current state and shortcomings +++++++++++++++++++++++++++++++ + +Currently Ganeti does not support IPv6. This is true for nodes as well +as instances. Due to the fact that IPv4 exhaustion is threateningly near +the need of using IPv6 is increasing, especially given that bigger and +bigger clusters are supported. + +Supported IPv6 setup +++++++++++++++++++++ + +In Ganeti 2.3 we introduce additionally to the ordinary pure IPv4 +setup a hybrid IPv6/IPv4 mode. The latter works as follows: + +- all nodes in a cluster have a primary IPv6 address +- the master has a IPv6 address +- all nodes **must** have a secondary IPv4 address + +The reason for this hybrid setup is that key components that Ganeti +depends on do not or only partially support IPv6. More precisely, Xen +does not support instance migration via IPv6 in version 3.4 and 4.0. +Similarly, KVM does not support instance migration nor VNC access for +IPv6 at the time of this writing. + +This led to the decision of not supporting pure IPv6 Ganeti clusters, as +very important cluster operations would not have been possible. Using +IPv4 as secondary address does not affect any of the goals +of the IPv6 support: since secondary addresses do not need to be +publicly accessible, they need not be globally unique. In other words, +one can practically use private IPv4 secondary addresses just for +intra-cluster communication without propagating them across layer 3 +boundaries. + +netutils: Utilities for handling common network tasks ++++++++++++++++++++++++++++++++++++++++++++++++++++++ + +Currently common util functions are kept in the utils modules. Since +this module grows bigger and bigger network-related functions are moved +to a separate module named *netutils*. Additionally all these utilities +will be IPv6-enabled. + +Cluster initialization +++++++++++++++++++++++ + +As mentioned above there will be two different setups in terms of IP +addressing: pure IPv4 and hybrid IPv6/IPv4 address. To choose that a +new cluster init parameter *--primary-ip-version* is introduced. This is +needed as a given name can resolve to both an IPv4 and IPv6 address on a +dual-stack host effectively making it impossible to infer that bit. + +Once a cluster is initialized and the primary IP version chosen all +nodes that join have to conform to that setup. In the case of our +IPv6/IPv4 setup all nodes *must* have a secondary IPv4 address. + +Furthermore we store the primary IP version in ssconf which is consulted +every time a daemon starts to determine the default bind address (either +*0.0.0.0* or *::*. In a IPv6/IPv4 setup we need to bind the Ganeti +daemon listening on network sockets to the IPv6 address. + + +Node addition ++++++++++++++ + +When adding a new node to a IPv6/IPv4 cluster it must have a IPv6 +address to be used as primary and a IPv4 address used as secondary. As +explained above, every time a daemon is started we use the cluster +primary IP version to determine to which any address to bind to. The +only exception to this is when a node is added to the cluster. In this +case there is no ssconf available when noded is started and therefore +the correct address needs to be passed to it. + +Name resolution ++++++++++++++++ + +Since the gethostbyname*() functions do not support IPv6 name resolution +will be done by using the recommended getaddrinfo(). + Feature changes --------------- -- 1.7.1
