In what situation , "SNMPERR_SUCCESS" error is thrown

Question

0.00/5 (No votes)

See more:

Can anyone please help in knowing when will we get the SNMPERR_SUCCESS error.
From the description of snmp_api.h, I see this is the non-pdu success code.
What does that mean.?

I have a scenario where I am trying to open a snmp session.
In return, it is going to catch block of my code saying failed to open snmp session with error code (0,0).

I understood that (0,0) means SNMPERR_SUCCESS. But I want to know what could be the problem. if it means a success code. why is it in error list.

Please correct me if I have mistaken. and help me to analyse further

Thanks in advance.

Posted 30-Oct-15 0:12am

Member 12018498

Add a Solution

Comments

Andy Lanng 30-Oct-15 7:46am

Wow - that takes me back :)

SNMPERR_SUCCESS is letting you know the return code. In this case they used the misnomer SNMPERR as the prefix for the return code. If it is non-zeo then an error of some sort occurred. if it is zero then it's fine and you get the SNMPERR_SUCCESS.

It means "all went as expected". It's a good thing ^_^

Member 12018498 30-Oct-15 7:55am

Thank you Andy..But the snmp session was not started .
From the below description... snmp_open will return null if some error occurs.
/*
* netsnmp_session *snmp_open(session)
* netsnmp_session *session;
*
* Sets up the session with the snmp_session information provided
* by the user. Then opens and binds the necessary UDP port.
* A handle to the created session is returned (this is different than
* the pointer passed to snmp_open()). On any error, NULL is returned
* and snmp_errno is set to the appropriate error code.
*/
netsnmp_session *snmp_open(netsnmp_session *);
............................................................
So i wrote a check if its null throw the error. Its quite clear that it was null.
Can you please suggest something

Andy Lanng 30-Oct-15 7:59am

pfff. I had to really strain to remember that much. Jochen has posted a solution version of my comment to I assume he is more knowledgeable than me as of right now.

(I've forgotten more than I know, but that nothing about my current level of knowledge ^_^)

Member 12018498 30-Oct-15 8:03am

Ok no problem :) . Thanks again for helping to understand.

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Jochen Arndt · Answer 1 · 2015-10-30T01:44:00

Solution 1

It is just the success return value. It is part of the error definition list to have also a value indicating that no error occured.

Your code should not interpret that value as error.

[UPDATE]
From comments it has become clear that the failing function is snmp_open:

struct snmp_session * snmp_open ( struct snmp_session *);

This function does not return a SNMP_ERR* code but a pointer. When this fails, NULL is returned and the error code can be retrieved:

struct snmp_session session;
struct snmp_session *handle;

snmp_sess_init(&session);
// Set session parameters here
handle = snmp_open(&session);
if (NULL == handle)
{
    // handle error here
    int liberr, syserr,
    char *errstr;
    snmp_error(&session, &liberr, &syserr, &errstr);
    printf("SNMP open error %s.\n", errstr);
    free(errstr);
}

Posted 30-Oct-15 1:44am

Jochen Arndt

Updated 30-Oct-15 2:31am

v2

Comments

Member 12018498 30-Oct-15 7:58am

Thank you Jochen.Does that mean there is some other problem with null value returned from snmp_open?. Please see the above comment

Jochen Arndt 30-Oct-15 8:08am

The return value of snmp_open() is a pointer to a netsnmp_session and not a SNMP_ERR_* code!

Functions returning pointers usually return NULL upon errors. Then the corresponding error code can be accessed by a function (old: snmp_get_errno, new: snmp_error) or global variable (old: snmp_errno, new: snmperr).

See also the snmp_open man page (http://linux.die.net/man/3/snmp_open).

Member 12018498 30-Oct-15 8:45am

The error code I got was SNMPERR_SUCCESS. I accessed the error code and the result I got is (0,0). which means everything is fine. go ahead. But if its returned null, there must be some problem rite?

part of code---
............................................................
struct snmp_session session;( snmp_session present in snmp_api.h.)
openSession = NetSnmp::getInstance().snmp_sess_open(&session);
if (NULL == openSession) {
int liberr=0, syserr=0;
char *errstr=NULL;
NetSnmp::getInstance().snmp_error(&session, &liberr, &syserr, &errstr);

std::string error(errstr);
::free(errstr);
cout<<"Failed to open snmp session to %s, error: %s (%d,%d)", port,errstr, liberr, syserr";
close();
}

And the output is: "Failed to open snmp session to 127.0.0.1:xxxx, error: (0,0)"

.............................................................
hence I was confused, that error code says everything is fine, but still null is returned .

Jochen Arndt 30-Oct-15 8:56am

Here you call snmp_sess_open() and not snmp_open().

Than you should call snmp_sess_error() upon failures and not snmp_error().

See http://linux.die.net/man/3/snmp_sess_open.

Member 12018498 30-Oct-15 9:06am

I am really thankful for your time Jochen. Thank you so much.
went through the link suggested by you. and i see the below line
"For errors returned by snmp_sess_open(), use the corresponding function snmp_error() instead of snmp_sess_error(). " So I think that it should not be the problem.

Jochen Arndt 30-Oct-15 9:20am

Hmm. You are right. So it seems that both functions can be used. But the documentation is inconsistent here.

Just another question:
Which SNMP implementation are you using on which platform and OS?
It may be that you are using a different implementation that behaves differently. So you should always check the documentation for the used implementation. With Linux, just enter for example "man 3 snmp_sess_open" on a shell prompt.

Member 12018498 30-Oct-15 9:32am

NET-SNMP version: 5.4.2.1 on Unix platform.

Jochen Arndt 30-Oct-15 9:41am

The man page at http://www.net-snmp.org/docs/man/snmp_sess_api.html is similar to the one from my link.

Do you still get a NULL pointer but no error code?
Than only an inspection of the NET-SNMP source code may show when this can occur.

Note also that version 5.4.2.1 is out of support and may contain bugs that has been fixed with newer versions.

Member 12018498 2-Nov-15 4:36am

Thank you Jochen for the suggestion. I went through the source code of snmp_api.
I found out when will we get SNMPERR_SUCCESS.
Below is the part of code
....................................................
if (slp->session->securityEngineIDLen == 0) {
DEBUGMSGTL(("snmp_api","unable to determine remote engine ID\n"));
snmp_sess_close(slp);
return NULL;
}
in_session->s_snmp_errno = SNMPERR_SUCCESS;
....................................................

As I am new, I dont know much about what is engineId . So trying to figure out.

Thanks again. Have a good day

Jochen Arndt 2-Nov-15 4:42am

You won't get SNMPERR_SUCCESS when the IF condition fails because the function returns NULL before the error code is cleared (it is hopefully set to some code before). You should check if the functions returns NULL afterwards without changing the error code.