System Repository and Publishers

Introduction: 

Linked images, and zones in particular, must keep certain packages

in sync with the global zone in order to be functional. The global zone will

constrain packages within the non-global zones and configure special publishers

in the non-global zone (NGZ). These publishers (henceforth called system

publishers) are special because the non-global zone cannot make certain kinds of

modifications to them. Among the forbidden operations for the non-global zone on

the system publishers are deleting, disabling, removing or replacing origins

provided by the system repository, and any other operations which might prevent

the solver from meeting the constraints imposed by the constraint package. The

global zone must provide the means for the non-global zone to configure itself

with system publishers by providing information like origins. The global zone

also has to provide a connection to the system publishers' repositories which is

available even in a scratch zone.

The Data path:

The pkg client in the NGZ uses the system repository in the global zone as a

proxy to the system publishers.  To ensure that a communication path between the

pkg client in the NGZ and the system repository in the global zone always

exists, the zone proxy client and the zone proxy daemon were created.

The zone proxy client runs in the NGZ. When started, it creates a socket which

listens on an inet port on 127.0.0.1 in the NGZ. It passes the file descriptor

for this socket to the zone proxy daemon in the global zone via a door call. The

zone proxy daemon listens for connections on the file descriptor. When zone

proxy daemon receives a connection, it proxies the connection to the system

depot.  The system depot is an Apache instance running in the global zone which

provides connectivity to and configuration of publishers.

The system depot acts as a proxy for the http and https repositories for

the publishers it provides.  When proxying to https repositories, it uses the

keys and certificates in the global zone to identify itself and verify the

server's identity.  It also provides a http interface to the file repositories

for the publishers it provides as well as serving publisher and image

configuration via the syspub/0 response.

Configuration:

The syspub/0 response is a p5s file.  The p5s file contains publisher

configuration and image configuration.  Currently, the only image configuration

it contains is the publisher search order for the provided publishers, but other

information may be added to the response as needed.  In addition to the basic

collection of publisher information, the p5s file also contains a list of urls

which the pkg client should proxy to via the system depot instead of contacting

them directly.  When creating a p5s file, the urls for origins and mirrors can

be transformed.  HTTPS urls are transformed to HTTP urls since the system depot

will be doing the SSL communication, not the pkg client.  File urls are

transformed into HTTP urls with a special format.  The urls contain the special

token "<sysrepo>" which the p5s parser knows to replace with the url of the zone

proxy client.  The rest of the url contains the prefix of the publisher, then

the sha1 hash of the global zone path to the file repository.

The information for the syspub/0 response comes from the global zone's image's

configuration.  The pkg/sysrepo service is responsible transforming the image

configuration into an Apache configuration file and causing the system depot to

reread its configuration.  The global zone pkg client restarts the pkg/sysrepo

servvice whenever the image's publisher configuration changes.