Hi!
I got absolute zero replies to my message, so I created an isolated test case
in the mean-time. The test case looks like this:
static volatile int stop_requests = 0; /* count stop requests */
/* main */
int main(int argc, char *argv[])
{
int result = 0;
/*BEGIN SNMP*/
/* prepare for AgentX subagent */
if ( netsnmp_ds_set_boolean(NETSNMP_DS_APPLICATION_ID,
NETSNMP_DS_AGENT_ROLE, 1)
!= SNMPERR_SUCCESS )
{
result = 2;
}
SOCK_STARTUP; /* initialize TCP/IP, if necessary */
init_agent("testagent"); /* initialize the agent library */
init_IOTWatchMIB(); /* initialize MIB module */
while ( stop_requests == 0 ) {
agent_check_and_process(1); /* 0 == don't block */
}
/* at shutdown time */
snmp_shutdown("testagent");
SOCK_CLEANUP;
/*END SNMP*/
quit: return(result);
}
When running the testagent with ltrace, I see the handlers are registered, and
the test agent waits for data:
---
SNMP> ltrace ./testagent
__libc_start_main(0x400f40, 1, 0x7ffc0e2bb4e8, 0x4011b0, 0x4011a0 <unfinished
...>
netsnmp_ds_set_boolean(1, 1, 1, 0, 0x7fd165f0f320) = 0
init_agent(0x4012a4, 0x7fd1663d1f40, 0, 1, 0x7fd165f0f320) = 0
snmp_get_do_debugging(1, 1, 0, 1, 0x2965736c61667c) = 0
netsnmp_create_handler_registration(0x40134d, 0x401040, 0x602120, 13, 1) =
0x6071a0
netsnmp_register_scalar(0x6071a0, 0x602188, 0, 1, 1000) = 0
netsnmp_create_handler_registration(0x40135f, 0x400fd0, 0x6020a0, 13, 1) =
0x607d40
netsnmp_register_scalar(0x607d40, 0x602108, 0, 2, 1000) = 0
agent_check_and_process(1, 0x7fd166a33049, 0, 0, 0x608050
---
However If I query the OIDs registered, no data are returned ("There is no such
variable name in this MIB.")
The init Module looks like this:
/** Initializes the IOTWatchMIB module */
void
init_IOTWatchMIB(void)
{
static oid giveItABetterName_oid[] =
{ 1, 3, 6, 1, 4, 1, 8072, 9999, 9999, 1000, 1, 1, 1 };
static oid giveThisANameToo_oid[] =
{ 1, 3, 6, 1, 4, 1, 8072, 9999, 9999, 1000, 1, 1, 2 };
DEBUGMSGTL(("IOTWatchMIB", "Initializing\n"));
netsnmp_register_scalar(netsnmp_create_handler_registration
("giveItABetterName", handle_giveItABetterName,
giveItABetterName_oid,
OID_LENGTH(giveItABetterName_oid),
HANDLER_CAN_RONLY));
netsnmp_register_scalar(netsnmp_create_handler_registration
("giveThisANameToo", handle_giveThisANameToo,
giveThisANameToo_oid,
OID_LENGTH(giveThisANameToo_oid),
HANDLER_CAN_RONLY));
}
(The handlers both should cause an abort if called (to help debugging)):
switch (reqinfo->mode) {
case MODE_GET:
snmp_set_var_typed_value(requests->requestvb, ASN_INTEGER,
(u_char *) 0 /* XXX: a pointer to the scalar's
data */
, 1 /* XXX: the length of the data in bytes */
);
break;
I have absolutely no idea how to debug this. While debugging I'm running snmpd
in user mode as suggested in the tutorial:
/usr/sbin/snmpd -f -Lo -C --rwcommunity=public --master=agentx \
--agentXSocket=tcp:localhost:1705 udp:1161 -Dagentx
I fail to see where my testagent connects to the SNMP socket, nor do I see that
my config file is opened. The select() is on a pipe, but I cannot see any other
process in strace:
---
2819 munmap(0x7f84066bd000, 4096) = 0
2819 gettimeofday({1439373523, 620867}, NULL) = 0
2819 pipe([3, 4]) = 0
2819 gettimeofday({1439373523, 621388}, NULL) = 0
2819 pipe([5, 6]) = 0
2819 select(6, [3 5], NULL, NULL, NULL) = ? ERESTARTNOHAND (To be restarted)
2819 --- SIGINT (Interrupt) @ 0 (0) ---
2819 +++ killed by SIGINT +++
---
Any ideas?
Regards,
Ulrich
>>> Ulrich Windl schrieb am 05.08.2015 um 10:42 in Nachricht <55C1CC7D.CAD :
>>> 161 :
60728>:
> Hello!
>
> I had reported problems with registering an AgentX subagent in Perl (no
> error, but doesn't work). Finally I found the bug that prevented it from
> working.
>
> Now I have a C program that uses multiple threads to retrieve and monitor
> some values. I tried to make this program an AgentX subagent by adding the
> code from the C coding example. Unfortunately the same things as in Perl
> happen: The agent does not connect, and there is no error. When trying to
> access any of the registered OIDs, an error is returned. None of the handlers
> is ever called.
>
> What I'd like to have eventually is that one thread takes care of all the
> SNMP handling.
>
> From the example I guess that the API is too high-level (init_agent()): It's
> hard to see which steps are actually executed, and what the results of these
> steps are.
>
> What could the problem be, and how could I debug it?
>
> The essential code fragemnt looks like this:
> /*BEGIN SNMP*/
> /* prepare for AgentX subagent */
> if ( netsnmp_ds_set_boolean(NETSNMP_DS_APPLICATION_ID,
> NETSNMP_DS_AGENT_ROLE, 1)
> != SNMPERR_SUCCESS )
> {
> /* report problem */
> }
> SOCK_STARTUP; /* initialize TCP/IP, if necessary
> */
> init_agent("iotwatch"); /* initialize the agent library */
> init_IOTWatchMIB(); /* initialize MIB module */
> while ( stop_requests == 0 ) {
> agent_check_and_process(1); /* 0 == don't block */
> }
>
> /* at shutdown time */
> snmp_shutdown("iotwatch");
> SOCK_CLEANUP;
> /*END SNMP*/
>
> Regards,
> Ulrich
>
>
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