Template:FAQ:Coding 02
That's typically the hardest bit of implementing a new MIB module,
and is the one thing that 'mib2c' can't help with.
It very much depends on the MIB variable concerned (and often
the underlying operating system as well).
Relatively few MIB modules are completely self-contained, with all the information held internally within the agent, and all updates being done via SNMP requests. Such MIB modules can be implemented fairly easily.
More commonly, the agent needs to provide an SNMP-based interface to
information held elsewhere, perhaps in the operating system kernel or
some other application. Handling this is much more complex - since
a lot depends on what mechanisms are provided for retrieving (and
possibly updating) this information. The mib2c tool can generate code
for processing SNMP requests, based on some internal cache of management
information, but it cannot help with populating this cache with the
underlying data. That is up to the MIB implementer.
See the existing MIB modules in the Net-SNMP source tree for various
examples of assorted approaches to this task.
