Hi all，
I wrote my own mib file and added it into the agent . But I can’t get the
right value by MIB Browser. The release version of net-snmp source code is
5.6.1.
The memory allocated in the routine “iifo->get_first_data_point” , which was
used to fill my table data, had been prematurely freed before calling the
handle ” netsnmp_call_next_handler( )” in table iterator routine.
Refer to the mib “nsModuleTable”, I initialized the table module,
registered the handler , defined the iterator access routines such as
“iifo->get_first_data_point”, “iifo->get_first_next_point” and
“iifo->free_loop_context_at_end”. But the value get by tool is wrong. So I
added debug message and found that, the memory, allocated in the routine
“iifo->get_first_data_point”, pointed by the pointer “my_loop_context”, was
freed prematurely by the routine “netsnmp_table_iterator_helper_handler( )”.
So when the routine ” netsnmp_call_next_handler( )” was called, the values
pointed by “my_loop_context” are wrong.
In file “table_iterator.c”, the 750 line code will do free as
follow.
/* free loop context before going on */
if (callback_loop_context &&
iinfo->free_loop_context_at_end) {
(iinfo->free_loop_context_at_end)
(callback_loop_context,
iinfo);
callback_loop_context = NULL;
}
But the handle ” netsnmp_call_next_handler( )” was called in line
854.
/* Finally, we get to call the next handler below us.
Boy, wasn't
all that simple? They better be glad they don't have to
do it! */
if (reqinfo->mode != MODE_GET_STASH) {
DEBUGMSGTL(("table_iterator", "call subhandler for mode:
%s\n",
se_find_label_in_slist("agent_mode", oldmode)));
ret =
netsnmp_call_next_handler(handler, reginfo,
reqinfo, requests);
}
Why the loop context will be freed before calling the handle ”
netsnmp_call_next_handler( )” ? In that case, the mib “nsModuleTable” will
also do not work and get wrong value? Is that a problem?
So I modified the above code, and moved the code which doing free loop
context from line 750 to the line behind the handler”
netsnmp_call_next_handler”. In this case, my mib will work well and MIB
Browser can get right values.But I cannot ensure this modification is right
and do not have any bad influence.
In addition, I download the previous source code, release version is
5.0.11.2, and found different. The free action will be done after calling
the handle ” netsnmp_call_next_handler( )”. In this case, MIB Browser got
the right value too.
Can you help me to check this problem? Thank you!
Best wishes,
wise
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