OSF DCE Application Development Guide--Core Components

DCE Host Services
manage them. This also allows for scalability because it is impractical to manage a large
system by logging into all its hosts.
The features of dced are greatly enhanced when used remotely. Of course, an
administrator can use dced to locally manage a host’s services, but dced’s real power is
in remotely managing system and application server configurations, key tables, server
startup, login configurations, and cell information.
Security becomes a major issue when it comes to remote services. With the power of
dced’s services and dcecp, it is important that only authorized principals can use them.
The dced program controls access to its various objects by using ACLs. Server keys are
security-sensitive data that must be seldom transmitted over the network. All key table
data is encrypted when it is transmitted for secure remote key table management.
Finally, the remote capabilities of dced give you real-time status of processes and
services in DCE.
2.3 Managing a Host’s Endpoint Map
Each DCE host has an endpoint map that contains a mapping of servers to endpoints.
Each endpoint map server entry is associated with an array of services (interfaces)
provided by the server, and each service is associated with an array of objects supported
by the service.
When a typical server calls the dce_server_register() routine, the RPC runtime
generates the endpoints on which the server will listen for calls and then uses dced’s
endpoint mapper service of the local host to register the endpoints. Later, when a typical
client makes a remote procedure call, its RPC runtime uses the server host’s endpoint
mapper service to find the server. When the typical server shuts down, it calls the
dce_server_unregister( ) routine to remove its endpoints from the endpoint map so that
clients do not later try to bind to it.
Applications can also use the lower-level rpc_ep_register( ) and associated RPC
routines. Since the endpoint map is essential for RPCs to work, endpoints are fully
described in Chapter 12 and the endpoint map structure is described with respect to
routing of RPCs in Chapter 16.
The endpoint map is for the most part maintained automatically by dced. For example, it
periodically removes ‘‘stale’’ endpoints so that the RPC runtime will not try to complete
a binding for a client to a server that is no longer running. However, administrative
applications may find it necessary to peruse a remote endpoint map and even remove
specific endpoints from a local host’s endpoint map.
To read the elements of a remote endpoint map, applications use a loop with the set of
routines rpc_mgmt_ep_elt_inq_begin( ), rpc_mgmt_ep_elt_inq_next( ), and
rpc_mgmt_ep_elt_inq_done( ). The inquiry can return all elements until the list is
exausted, or the inquiry can be restricted to return elements for the following:
• Elements matching an interface identifier (UUID and version number)
• Elements matching an object UUID
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