Red Hat DIRECTORY SERVER 7.1 - PLUG-IN PROGRAMMERS Manual page 34

Types of Directory Server Plug-ins
Types of Directory Server Plug-ins
You can write the following types of plug-ins for the Directory Server:
• Pre-operation/data validation. The server calls a pre-operation/data
validation plug-in function before performing an LDAP operation.
The main purpose of this type of plug-in is to validate data before the data is
added to the directory or before it is used in an operation.
• Post-operation/data notification. The server calls a post-operation/data
notification plug-in function after performing an LDAP operation.
The main purpose of this type of plug-in is to invoke a function after a
particular operation is executed. For example, you can write a plug-in that
sends email to users if their entries are modified.
• Entry storage and entry fetch. The server calls an entry storage plug-in
function right before writing data to the database backend. The server calls
entry fetch plug-in functions after retrieving an entry from the database
backend.
For example, you can create an entry storage plug-in that encrypts an entry
before it is saved to the database and an entry fetch plug-in that decrypts an
entry after it is read from the database.
• Extended operation. The server calls an extended operation plug-in function
when the client requests an operation by OID. Extended operations are
defined in LDAP v3 and are described in more detail in chapter 10, "Writing
Extended Operation Plug-ins."
• Syntax. The server calls a syntax plug-in function when getting a list of
possible candidates for a search. The server also calls these functions when
adding or deleting values from certain attribute indexes.
Syntax plug-in functions can define the comparison operations used in
searches. For example, you could use a syntax plug-in function to define how
the "equals" comparison works for case-insensitive strings.
• Matching rule. The server calls matching rule plug-in functions when the
client sends a search request with an extensible matching search filter. You
can also write matching rule plug-in functions that the server calls when
indexing attributes for the backend database.
Figure 1-2 illustrates how some of these different plug-in types fit into the
Directory Server architecture.
34 Red Hat Directory Server Plug-in Programmer's Guide • May 2005