Debugging the SNMP manager API

You can debug problems with the SNMP manager API in two ways.

For manager applications, call the snmpSetLogLevel() routine using the following debug levels:

Table 1. SNMP manager API debug levels
Debug level	Description
SNMP_LOG_NONE (0)	No logging
SNMP_LOG_ERROR (1)	Log only errors
SNMP_LOG_TRACE (2)	Trace function upon entry and exit
SNMP_LOG_DUMP(4)	Dump the session object
SNMP_LOG_ALL (7)	Log all levels except SNMP_LOG_INTERNAL
SNMP_LOG_INTERNAL (8)	Log all traces for packet processing

When calling the snmpSetLogLevel() routine, you can use multiple trace levels by specifying either the numerical value of each desired item, or the logical name. For example, for both SNMP_LOG_ERROR (1) and SNMP_LOG_TRACE (2), you can issue one of the following:

snmpSetLogLevel(SNMP_LOG_ERROR + SNMP_LOG_TRACE)
snmpSetLogLevel(3)

Set the SNMP_MGR_LOG_LEVEL debuglevel environment variable to turn on debugging. This environment variable is read when the snmpInitialize() function is called. You can set multiple trace levels by adding the levels that you want to trace.

The SNMP manager API attempts to read the SNMP_MGR_LOG_LEVEL environment variable in the snmpInitialize() function. If your SNMP manager calls the snmpSetLogLevel() function before calling the snmpInitialize() function, all API-generated trace messages in the snmpInitialize() function are logged. If not, logging begins inside the snmpInitialize() function after the environment variable is validated. After the environment variable has been read in the snmpInitialize() function, the value of the environment variable SNMP_MGR_LOG_LEVEL (if set) is used as the log level for your SNMP manager application. After this point, calls to the snmpSetLogLevel() function do not change the log level. You must unset the environment variable for this function to operate correctly.

The SNMP manager API, by default, uses the SYSLOG daemon, and uses the current SYSLOG configuration for the output location. However, by declaring the SNMP_MGR_LOG_FILE environment variable, the SNMP manager can also send the output stream to an individual file (in addition to SYSLOG or another logging function). Use the SNMP_MGR_LOG_FILE environment variable to test your application. If the environment variable is declared, the log messages generated by the SNMP manager API are sent to both the file specified by the environment variable and either SYSLOG or your own logging function.

You can use your own logging function, rather than the SYSLOG default. Using your own logging function has the benefit of providing the log messages from the SNMP manager API, and your application logging. Your logging function overrides the default, SYSLOG logging function, which means that after you have enabled your logging function in the SNMP manager API, log messages are no longer sent to SYSLOG. If you have declared the SNMP_MGR_LOG_FILE environment variable, log messages are sent to both your logging function and to the file specified by the environment variable.

To use your own logging function, your SNMP manager needs to pass the name of the function as a parameter to the SNMP manager API's snmpSetLogFunction() routine. Every message produced by the SNMP manager API is then sent to your logging function, along with the integer that specifies the level of the log message (for example, SNMP_LOG_TRACE). Your function definition must be defined as follows so that the SNMP manager API calls it correctly:

void myLogger(int logLevel, char *logMsg);