Registering scalar (single-value) MIB variables

Bind one C getter/setter to one OID that ends in .0. More...

Classes
class	SNMPReadObject
	Registers a scalar read callback with the SNMP agent. More...
class	SNMPWriteObject
	Registers a scalar write callback with the SNMP agent. More...

Macros
#define	SNMPREADFUNC(w, x, y, z, q)   static SNMPReadObject W##w(x, y, z, q);
	Register a read callback for one SNMP scalar at file scope.
#define	SNMPWRITEFUNC(w, x, y, z, q)   static SNMPWriteObject R##w(x, y, z, q);
	Register a write callback for one SNMP scalar at file scope.

Detailed Description

Bind one C getter/setter to one OID that ends in .0.

Use SNMPREADFUNC for a read callback and SNMPWRITEFUNC for a write callback. The return type of the read callback (or the value parameter of the write callback) selects the ASN.1 encoding via the matching ASN_type* tag from SMI type aliases, ASN.1 tags, and SET return codes.

Macro Definition Documentation

SNMPREADFUNC

#define SNMPREADFUNC	(		w,
			x,
			y,
			z,
			q )   static SNMPReadObject W##w(x, y, z, q);

#include <snmp_table.h>

Register a read callback for one SNMP scalar at file scope.

Parameters

w	Base identifier used to name the generated static instance.
x	Dotted-decimal OID string (scalars end in .0).
y	One of the ASN_type* tags (e.g. ASN_typeInteger32).
z	Pointer to the read callback (matching one of GetpIFunc etc.).
q	Community mask, typically READ_COMMUNITY_MASK.

Expands to a file-static SNMPReadObject so the callback is registered before main() runs. Use once per scalar; pair with SNMPWRITEFUNC if the variable is writable.

Example

snmp_typeInteger32 ReadVoltage() { return g_voltage_mv; }
SNMPREADFUNC(VOLTAGE, "1.3.6.1.4.1.8174.10.1.0", ASN_typeInteger32,
             ReadVoltage, READ_COMMUNITY_MASK);

SNMPWRITEFUNC

#define SNMPWRITEFUNC	(		w,
			x,
			y,
			z,
			q )   static SNMPWriteObject R##w(x, y, z, q);

#include <snmp_table.h>

Register a write callback for one SNMP scalar at file scope.

Parameters

w	Base identifier used to name the generated static instance.
x	Dotted-decimal OID string (scalars end in .0).
y	One of the ASN_type* tags (e.g. ASN_typeInteger32).
z	Pointer to the write callback (matching one of PutpIFunc etc.).
q	Community mask, typically WRITE_COMMUNITY_MASK.

Expands to a file-static SNMPWriteObject so the callback is registered before main() runs. The callback is invoked twice for each SET request: first with bTest != 0 for validation, then with bTest == 0 to commit. Return SNMP_SET_OK or SNMP_SET_FAIL.

Example

int WriteOutput(int var, int bTest) {
    if (bTest) return (var == 0 || var == 1) ? SNMP_SET_OK : SNMP_SET_FAIL;
    g_output_on = var;
    return SNMP_SET_OK;
}
SNMPWRITEFUNC(OUTPUT, "1.3.6.1.4.1.8174.10.2.0", ASN_typeInteger32,
              WriteOutput, WRITE_COMMUNITY_MASK);