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Solaris System Management Agent Developer's Guide

Migrating Solstice Enterprise Agent Subagents to SMA

The SMA does not provide a comprehensive tool to migrate a Solstice Enterprise Agents subagent to an SMA module. A Solstice Enterprise Agents subagent uses two types of API functions. One type of API function is used for interaction with the master agent, and the other type is used for custom implementation. The functions for interaction with the master agent are common among all subagents. No tool is available that can separate the two types of functions, and put only the custom implementation code automatically into the corresponding place in the mib2c-generated code.

The simplest way to migrate a Solstice Enterprise Agents subagent is first to use the MIB tools of each environment to create code templates for each environment.

The following table compares aspects of the SMA mib2c tool and the Solstice Enterprise Agents mibcodegen tool. This comparison might help you to understand the code templates that each tool produces.

Table 10–1 Comparison of MIB Tools in SMA and Solstice Enterprise Agents Software

 

SMA mib2c tool

Solstice Enterprise Agents mibcodegen tool

Scope of action on MIB 

mib2c is run against individual nodes in a MIB, such as a subtree that contains scalars or a table. Running mib2c against individual tables rather than a parent subtree or group is advantageous. You can generate code templates that are customized according to the way you plan to implement each table in SMA. For example, you can generate templates for a table differently if the table is internal or external to the agent.

mibcodegen is run against the whole MIB.

Code generated 

mib2c generates code for the implementation of a module that can be used in SNMP agent or AgentX subagent frameworks. Well-defined APIs are used to expose the functionality.

mibcodegen generates code to make the output represent a standalone subagent. SNMP is used to communicate between the master agent and the subagent.

demo_module_12 Code Example for Solstice Enterprise Agents Subagent Migration

The demo_module_12 demonstrates how to implement a Solstice Enterprise Agents subagent as an SMA module.

The demo_module_12 code example is by default located in the directory /usr/demo/sma_snmp/demo_module_12. The README_demo_module_12 file within that directory contains instructions that describe how to perform the following tasks:

You should perform the procedures in demo_module_12 to produce the templates that are analyzed in the following section.

Analysis of the demo_module_12 Solstice Enterprise Agents Templates

The mibcodgen tool produced several files. The following table describes and analyzes the files.

Table 10–2 Comparison of Solstice Enterprise Agents Templates to SMA Templates

Template File Name 

Content 

Comparison to SMA Templates 

example_tree.c

Contains the type or storage definition for the MIB information. 

Only the OID and column definitions contained in this file are also used in templates generated by mib2c. The agent or AgentX frameworks handle the rest for you.

example_stub.h

Contains extern function definitions for all get, set, and free functions that implement the variables in the MIB.

For each SNMP group, mib2c generates an include file that defines externs for similar functions for both scalars and tables.

example_stub.c

Contains all get, set, and free functions that implement the scalar variables in the MIB.

For each SNMP group, mib2c generates a source code file. The file implements code for similar functions for the data types that the group contains, scalars, or tables.

mib2c also generates the registration code that is invoked at initialization time. The registration code makes the agent aware of the OIDs that are supported. The registration code also identifies the get and set functions.

example_rwTableEntry.c

Contains all get, set, and free functions that implement the column variables for rwTableEntry in the MIB.

An equivalent file, tableType.c in the example, is generated by mib2c with one of the table configuration options. The mib2c-generated file contains similar functions but uses very different index handling.

mibcodegen generates a get method that is passed a parameter to indicate whether to perform a get or getnext request.

With mib2c, however, the index handling is performed prior to invoking the get method to handle a getnext request. A get_first method is exposed to the SMA agent so that the agent can find the first item in a table. A get_next method handles getting the next row in the table. When the correct row is found, the get or set method is called with the column to manipulate. This process applies to getting the correct row for get, getnext, or set functions when the data is external to the agent. If the data is held by the SMA master agent, table registration involves populating the table. After the table is populated, requests to the table would be handled directly by the SMA master agent.

example_trap.c

Contains trap definitions. 

mib2c does not generate equivalent code. Traps can be generated by calling send_enterprise_trap_vars().

example_appl.c

Contains code to support subagent. 

mib2c does not generate equivalent code because such code is not needed. The SMA agent or AgentX framework handles the overhead and invokes the code through API functions.

Modifying the SMA Instrumentation Code

After you generate and analyze the templates, the task then is to extract the core SNMP get, getnext, and set processing out of the Solstice Enterprise Agents subagent code, and move it to the get and set handler and get_first/get_next methods defined in the SMA module approach.

The index handling is removed from each get and set function in Solstice Enterprise Agents code to be handled by the SMA. Special methods are used for tables. Context fields are used to store the current index information so that advancing in the table is relatively simple.