I'm tracing through the snmpd agent code (net-snmp 5.5) to study how it
works, but I'm getting stuck at what point the "context_subtrees" pointer
gets filled in. i.e. it's first initialized here,
agent/agent_registry.c: (line 209)
subtree_context_cache *context_subtrees = NULL;
So, we see it's assigned to NULL in the beginning. Code-Stepping (with
cscope) leads me to understand that it's first encountered in this manner
(during initialization/startup),
setup_tree() -> netsnmp_register_null() -> netsnmp_register_null_context()
-> netsnmp_register_null_context() -> netsnmp_register_handler() ->
netsnmp_register_mib() -> netsnmp_subtree_load() ->
netsnmp_subtree_find_first()
In that last function [ netsnmp_subtree_find_first() ], I'm assuming that as
the value of "context_subtrees" would be NULL the first time, it (the
function) should return NULL as well. And here is where my problem starts.
IF "netsnmp_subtree_find_first()" returns NULL, then we end up calling
"netsnmp_register_null_context()" AGAIN, which leads to an infinite calling
loop (as mentioned above) - which obviously doesn't make sense (the code
compiles and runs fine for me).
The way I see it, my 'paradox' can be fixed if "context_subtrees" is
assigned a value (other than NULL) somewhere. But, I can't find it. The ONLY
function that fills it in is "add_subtree()" - but that isn't called from
anywhere during initialization/startup.
I'm going round in circles here. :( Anyone know what I'm missing? Just a
small hint would do.
Getting dizzy,
Abraham V.
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