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Re: Can we extract (agent)IP address for which get/set request is

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parveen yadav

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May 9, 2009, 5:15:06 AM5/9/09

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Wes Hardaker wrote:
>>>>>> On Tue, 05 May 2009 14:27:53 +0530, parveen yadav <parvee...@coraltele.com> said:
>>>>>>
>
> py> I am trying to extract agent IP address for which get/set request is
> py> generated by snmpget in get_first_data_point,get_next_data_point and
> py> table handler. I am table iterator for my table.
>
> No, you can't. Though technically possible some of the time it's
> generally not something that you should be doing. SNMP wasn't designed
> to work that way, and although it's possible it breaks under some
> conditions. EG, if you ever want to run your code as an AgentX subagent
> that information isn't available at all.
>
But i think we can extract request ip in case net-snmp is working as
main agent and we do not need to handle AgentX. But it is hard to find
the storage location. I have tried request structure.
Do i need to look some where else also??

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Wes Hardaker wrote:
<blockquote cite="mid:sdtz3zn...@wes.hardakers.net" type="cite">
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">On Tue, 05 May 2009 14:27:53 +0530, parveen yadav <a class="moz-txt-link-rfc2396E" href="mailto:parvee...@coraltele.com"><parvee...@coraltele.com></a> said:
</pre>
</blockquote>
</blockquote>
</blockquote>
</blockquote>
</blockquote>
<pre wrap="">
py> I am trying to extract agent IP address for which get/set request is
py> generated by snmpget in get_first_data_point,get_next_data_point and
py> table handler. I am table iterator for my table.

No, you can't. Though technically possible some of the time it's
generally not something that you should be doing. SNMP wasn't designed
to work that way, and although it's possible it breaks under some
conditions. EG, if you ever want to run your code as an AgentX subagent
that information isn't available at all.
</pre>
</blockquote>
But i think we can extract request ip in case net-snmp is working as
main agent and we do not need to handle AgentX. But it is hard to find
the storage location. I have tried request structure.<br>
Do i need to look some where else also??<br>
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parveen yadav

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May 12, 2009, 9:07:32 AM5/12/09

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Fulko Hew wrote:
>
> On Tue, May 12, 2009 at 2:23 AM, parveen yadav
> <parvee...@coraltele.com <mailto:parvee...@coraltele.com>> wrote:
>
> Fulko Hew wrote:
>> On Sat, May 9, 2009 at 5:18 AM, parveen yadav
>> <parvee...@coraltele.com <mailto:parvee...@coraltele.com>>
>> wrote:
>>
>> Wes Hardaker wrote:

>>>>>>>> On Tue, 05 May 2009 14:27:53 +0530, parveen yadav <parvee...@coraltele.com> <mailto:parvee...@coraltele.com> said:
>>>>>>>>
>>> py> I am trying to extract agent IP address for which get/set request is
>>> py> generated by snmpget in get_first_data_point,get_next_data_point and
>>> py> table handler. I am table iterator for my table.
>>>
>>> No, you can't. Though technically possible some of the time it's
>>> generally not something that you should be doing. SNMP wasn't designed
>>> to work that way, and although it's possible it breaks under some
>>> conditions. EG, if you ever want to run your code as an AgentX subagent
>>> that information isn't available at all.
>>>
>> But i think we can extract request ip in case net-snmp is
>> working as main agent and we do not need to handle AgentX.
>> But it is hard to find the storage location. I have tried
>> request structure.
>> Do i need to look some where else also??
>>
>>

>> If I understand correctly, then this was something I needed and I
>> recently
>> added to the Perl interface for agents, its available in the upcoming
>> release, but only for IPv4 based requests, and I don't think
>> it'll work
>> for AgentX based agents either.
> thanks for reply
>
> I have traced packet from snmp_read. But there is still confusion
> about Ipaddress of request. Can somebody clear the doubt.
>
>
> Can you be more specific? What are you confused about?
> What language are you using?
>
> If you are using Perl, your agent code would look something like this:
>
> if (!$agent) {
> print "The mandatory Perl agent is not defined in this Net-SNMP
> installation\n";
> return;
> }
> $agent->register('myprog', '1.2.3.4', \&my_snmp_handler);
>
> sub my_snmp_handler {
> my ($handler, $registration_info, $request_info, $requests) = @_;
>
> my $targetIp = inet_ntoa($request_info->getTargetIp());
> for (my $request = $requests; $request; $request = $request->next()) {
> handle_oid($targetIp, $request_info, $request);
> }
> }
>
>
I am using C language agent. There is netsnmp_request_info structure in
agent. In table handler , through requests list handler finds the
request to process.
But there is no method like getTargetIp(). It must be perl specific and
there must be some alternate.
I will try to explore this . This must be looking in request info for Ip.

thanks

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Fulko Hew wrote:
<blockquote
cite="mid:8204a4fe0905120532n1ea...@mail.gmail.com"
type="cite"><br>
<div class="gmail_quote">On Tue, May 12, 2009 at 2:23 AM, parveen
yadav <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:parvee...@coraltele.com">parvee...@coraltele.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div bgcolor="#ffffff" text="#000000">
<div>
<div class="h5">Fulko Hew wrote:<br>
<blockquote type="cite">
<div class="gmail_quote">On Sat, May 9, 2009 at 5:18 AM, parveen
yadav <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:parvee...@coraltele.com" target="_blank">parvee...@coraltele.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">
<div bgcolor="#ffffff" text="#000000">Wes Hardaker wrote:
<blockquote type="cite">

<pre>On Tue, 05 May 2009 14:27:53 +0530, parveen yadav <a
moz-do-not-send="true" href="mailto:parvee...@coraltele.com"

target="_blank"><parvee...@coraltele.com></a> said:
</pre>
</blockquote>
</blockquote>
</blockquote>
</blockquote>
</blockquote>

<pre>py> I am trying to extract agent IP address for which get/set request is

py> generated by snmpget in get_first_data_point,get_next_data_point and
py> table handler. I am table iterator for my table.

Do i need to look some where else also??</div>
</blockquote>
<div> </div>
<div>If I understand correctly, then this was something I needed
and
I recently</div>
<div>added to the Perl interface for agents, its available in the
upcoming</div>
<div>release, but only for IPv4 based requests, and I don't think
it'll work</div>
<div>for AgentX based agents either.</div>
</div>
</blockquote>
</div>
</div>
thanks for reply<br>
<br>
I have traced packet from snmp_read. But there is still confusion about
Ipaddress of request. Can somebody clear the doubt.</div>
</blockquote>
<div><br>
Can you be more specific?  What are you confused about?<br>
What  language are you using?<br>
<br>
If you are using Perl, your agent code would look something like this:<br>
<br>
<span style="font-family: courier new,monospace;">if (!$agent) {</span><br
style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">    print "The
mandatory Perl agent is not defined in this Net-SNMP installation\n"; </span><br
style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">    return;</span><br
style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">}</span><br
style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">$agent->register('myprog',
'1.2.3.4', \&my_snmp_handler); </span><br
style="font-family: courier new,monospace;">
<br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">sub my_snmp_handler
{</span><br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">    my ($handler,
$registration_info, $request_info, $requests) = @_;</span><br
style="font-family: courier new,monospace;">
<br style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">    my $targetIp =
inet_ntoa($request_info->getTargetIp());</span><br
style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">    for (my
$request = $requests; $request; $request = $request->next()) {</span><br
style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">       
handle_oid($targetIp, $request_info, $request);</span><br
style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">    }</span><br
style="font-family: courier new,monospace;">
<span style="font-family: courier new,monospace;">}</span><br
style="font-family: courier new,monospace;">
<br>
</div>
</div>
<br>
</blockquote>
I am using C language agent. There is netsnmp_request_info structure in
agent. In table handler , through requests list handler finds the
request to process. <br>
But there is no method like <span
style="font-family: courier new,monospace;">getTargetIp(). It must be
perl specific and there must be some alternate.<br>
I will try to explore this . This must be looking in request info for
Ip.<br>
<br>
thanks<br>
</span>
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parveen yadav

unread,

May 13, 2009, 4:00:23 AM5/13/09

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Fulko Hew wrote:
>
>
> On Tue, May 12, 2009 at 9:03 AM, parveen yadav

> Correct. getTargetIp() is a function I added to the Perl binding to
> NetSnmp.
> Below is the C code (for that Perl binding)
> I've highlighted the two relevant lines of code.
> When I investigated the Net-SNMP C code, I found that the requestor's IP
> address was in the reqinfo->asp->pdu->transport_data in the standard inet
> structure form. Unfortunately this address in the trasnsport_data
> structure
> is the 'raw' address in whatever protocol it may have arrived in (IPv4
> IPv6, IPX etc.)
> and the actual protocol type was lost (thrown away) at a higher level in
> the calling stack. So all I could do for my Perl/C stuff was assume I
> was receiving the request from an IPv4 address and look at it as such.
>
> To do it correctly would require a change to Net-SNMP so that the address
> is correctly decoded and passed down in the reqinfo structure (where there
> is already a place where it could reside). I was looking for a quick
> and simple change that would meet my needs.
>
> If you want to see my full analysis, I documented it in my change request
> to Net-SNMP for my Perl patch. Refer to this for that information:
>
> https://sourceforge.net/tracker/?func=detail&aid=2709705&group_id=12694&atid=312694
> <https://sourceforge.net/tracker/?func=detail&aid=2709705&group_id=12694&atid=312694>
>
> I hope this helps you!
> Fulko
>
>
> SV *
> narqi_getTargetIp(me)
> SV *me;
> PREINIT:
> netsnmp_agent_request_info *reqinfo;
> struct netsnmp_udp_addr_pair_s *addr_pair;
> struct in_addr *to;
> SV *rarg;
>
> CODE:
> reqinfo = (netsnmp_agent_request_info *) SvIV(SvRV(me));
>
> addr_pair = (struct netsnmp_udp_addr_pair_s *)
> (reqinfo->asp->pdu->transport_data); <-----
> to = (struct in_addr *)
> &(addr_pair->local_addr); <-----
> rarg = newSVpv((unsigned char *)(&to->s_addr),
> sizeof(to->s_addr));
> RETVAL = rarg;
> OUTPUT:
> RETVAL
>
thanks

Using transport _data, I am able to extract source and destination IP in
table handler. I tried to pass request info to to first and next data
point using raw pointer myvoid in iinfo(iterator info). After dong that
i am able to extract required info in these function also. I will test
few more cases before updating net-snmp code.

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cite="mid:8204a4fe0905120945jea...@mail.gmail.com"
type="cite"><br style="font-family: courier new,monospace;">

<div style="font-family: courier new,monospace;" class="gmail_quote">On
Tue, May 12, 2009 at 9:03 AM, parveen yadav <span dir="ltr"><<a

moz-do-not-send="true" href="mailto:parvee...@coraltele.com">parvee...@coraltele.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div bgcolor="#ffffff" text="#000000">
<div>
<div class="h5">Fulko Hew wrote:

<div class="gmail_quote">On Tue, May 12, 2009 at 2:23 AM, parveen
yadav <span dir="ltr"><<a moz-do-not-send="true"

href="mailto:parvee...@coraltele.com" target="_blank">parvee...@coraltele.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote"

style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div bgcolor="#ffffff" text="#000000">
<div>

<div>Fulko Hew wrote:<br>

if (!$agent) {<br>

    print "The

mandatory Perl agent is not defined in this Net-SNMP installation\n"; <br>
    return;<br>
}<br>
$agent->register('myprog',
'1.2.3.4', \&my_snmp_handler); <br>
<br>
sub my_snmp_handler
{<br>

    my ($handler,

$registration_info, $request_info, $requests) = @_;<br>
<br>

    my $targetIp =

inet_ntoa($request_info->getTargetIp());<br>

    for (my

$request = $requests; $request; $request = $request->next()) {<br>

handle_oid($targetIp, $request_info, $request);<br>
    }<br>
}<br>

</div>
</div>

I am using C language agent. There is netsnmp_request_info structure in
agent. In table handler , through requests list handler finds the
request to process. <br>

But there is no method like getTargetIp(). It must be

perl specific and there must be some alternate.<br>
I will try to explore this . This must be looking in request info for
Ip.<br>

</div>
</blockquote>
<div><br>
Correct. getTargetIp() is a function I added to the Perl binding to
NetSnmp.<br>
Below is the C code (for that Perl binding)<br>
I've highlighted the two relevant lines of code.<br>
When I investigated the Net-SNMP C code, I found that the requestor's IP<br>
address was in the reqinfo->asp->pdu->transport_data in the
standard inet<br>
structure form.  Unfortunately this address in the trasnsport_data
structure<br>
is the 'raw' address in whatever protocol it may have arrived in (IPv4
IPv6, IPX etc.)<br>
and the actual protocol type was lost (thrown away) at a higher level in<br>
the calling stack.  So all I could do for my Perl/C stuff was assume I<br>
was receiving the request from an IPv4 address and look at it as such.<br>
<br>
To do it correctly would require a change to Net-SNMP so that the
address<br>
is correctly decoded and passed down in the reqinfo structure (where
there<br>
is already a place where it could reside).  I was looking for a quick<br>
and simple change that would meet my needs.<br>
<br>
If you want to see my full analysis, I documented it in my change
request<br>
to Net-SNMP for my Perl patch.  Refer to this for that information:<br>
<br>
<a moz-do-not-send="true"
href="https://sourceforge.net/tracker/?func=detail&aid=2709705&group_id=12694&atid=312694">https://sourceforge.net/tracker/?func=detail&aid=2709705&group_id=12694&atid=312694</a><br>
<br>
I hope this helps you!<br>
Fulko<br>
<br>
<br>
SV *<br>
narqi_getTargetIp(me)<br>
        SV *me;<br>
    PREINIT:<br>
        netsnmp_agent_request_info *reqinfo;<br>
    struct netsnmp_udp_addr_pair_s *addr_pair;<br>
    struct in_addr *to;<br>
        SV *rarg;<br>
<br>
    CODE:<br>
        reqinfo = (netsnmp_agent_request_info *) SvIV(SvRV(me));<br>
<br>
        addr_pair = (struct netsnmp_udp_addr_pair_s *)
(reqinfo->asp->pdu->transport_data);   <-----<br>
        to = (struct in_addr *)
&(addr_pair->local_addr);                                    
<-----<br>
        rarg = newSVpv((unsigned char *)(&to->s_addr),
sizeof(to->s_addr));<br>
        RETVAL = rarg;<br>
    OUTPUT:<br>
        RETVAL<br>
</div>
</div>
<br>
</blockquote>
thanks<br>
<br>
Using transport _data, I am able to extract source and destination IP
in table handler. I tried to pass request info to to first and next
data point using raw pointer myvoid in iinfo(iterator info). After dong
that i am able to extract required info in these function also. I will
test few more cases before updating net-snmp code.<br>
</body>
</html>

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