Antw: Problems registering AgentX (in C)
"Ulrich Windl" <[email protected]>
| Newsgroups | gmane.network.net-snmp.user |
|---|---|
| Message-ID | <[email protected]> |
Hi again!
Even after adding "snmp_set_do_debugging(1);" at the beginning of my program, I have no real clue; the last lines I get are these:
---
trace: snmp_sess_select_info(): snmp_api.c, 5862:
sess_select: for all sessions: 5 3
sess_select: next alarm 0.-1020349360 sec
sess_select: blocking:no session requests or alarms.
---
I'm wondering: How does main() automatically process the options in the tutorial ("% ./mysubagent -f -Lo -x tcp:localhost:1705")? The example-daemon.c has no special commands for that.
I found one problem: I missed to add 'init_snmp("testagent");', but even then it didn't work.
Found the most important problem: Once I put the local config file (testagent.conf) into /etc/snmp, the agent became much more alive!
So the final question is: Is there a way to tell your subagent to locate the config file in the current directory? If you need to put it into /etc/snmp, you need root rights for development, and having a local, non-priviledged snmp Daemon for testing makes no sense.
Regards,
Ulrich
>>> "Ulrich Windl" <[email protected]> schrieb am 12.08.2015 um
12:01 in Nachricht <[email protected]>:
> 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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