Dynamic loadable module not working with compiled smpd V7.5.3

Jose Tornero <[email protected]> Fri, 5 Jul 2024 12:47:44 +0000
Newsgroups gmane.network.net-snmp.user
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Hello

I have a weird situation with a compiled snmpd V7.5.3 and not able to find =
out what's going on.

I have a linux system. At first instance I used the "official" snmpd (sudo =
apt-get install snmpd ... ) and added a reduced set of OIDs from an own MIB=
 (with several scalar OIDs) in a dynamic loadable module following the step=
s of the corresponding tutorial. It worked fine. So far so good.

Next, I had to add more OIDs that belonged to a table. I followed the corre=
sponding steps to add the table and got it working. In this case, the funct=
ionality for that table was added as a subagent. So at this moment everythi=
ng was fine. But I realized that one OID from the table was an OCTET STRING=
 which size was 65536 and in my case it only worked up to 1472 bytes. I inv=
estigated a little and I realized I had to recompile snmpd with that change=
.

I recompiled. The OID with big size worked perfectly well, with a big strin=
g (around 50000 bytes). But unfortunately (here comes the problem) the init=
ial scalar OIDs added by means of the dynamic loadable module didn't work: =
the response for a command snmpget is always "No Such Object available on t=
his agent at this OID".

More investigation and debugging. I see the following:


  1.  Function dlmod_load_module  is called (dlmod.c)
  2.  Inside that function, function dl_init is called in turn
  3.  From my dynamic loadable module, the function init_... is called (I c=
hecked it adding it a return value and capturing it in function dlmod_load_=
module and showing by means of DEBUGMSGTL)  but I don't see the log at the =
beginning of function init_... (I use "DEBUGMSGTL"). So this leads me to su=
spect there is some problem. I have investigated a lot but with no results =
...

Any ideas?

Thank you very much.
Jose.




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<p class=3D"MsoNormal"><span style=3D"font-size:10.0pt;font-family:&quot;Ar=
ial&quot;,sans-serif">Hello<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-size:10.0pt;font-family:&quot;Ar=
ial&quot;,sans-serif"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif">I have a weird situation with a compil=
ed snmpd V7.5.3 and not able to find out what&#8217;s going on. &nbsp;<o:p>=
</o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif">I have a linux system. At first instan=
ce I used the &#8220;official&#8221; snmpd (sudo apt-get install snmpd &#82=
30; ) and added a reduced set of OIDs from an own MIB (with several
 scalar OIDs) in a dynamic loadable module following the steps of the corre=
sponding tutorial. It worked fine. So far so good.
<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif">Next, I had to add more OIDs that belo=
nged to a table. I followed the corresponding steps to add the table and go=
t it working. In this case, the functionality for
 that table was added as a subagent. So at this moment everything was fine.=
 But I realized that one OID from the table was an OCTET STRING which size =
was 65536 and in my case it only worked up to 1472 bytes. I investigated a =
little and I realized I had to recompile
 snmpd with that change. <o:p></o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif">I recompiled. The OID with big size wo=
rked perfectly well, with a big string (around 50000 bytes). But unfortunat=
ely (here comes the problem) the initial scalar
 OIDs added by means of the dynamic loadable module didn&#8217;t work: the =
response for a command snmpget is always &#8220;No Such Object available on=
 this agent at this OID&#8221;.
<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif">More investigation and debugging. I se=
e the following:<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif"><o:p>&nbsp;</o:p></span></p>
<ol style=3D"margin-top:0cm" start=3D"1" type=3D"1">
<li class=3D"MsoListParagraph" style=3D"margin-left:0cm;mso-list:l0 level1 =
lfo1"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-family:&quot;Aria=
l&quot;,sans-serif">Function dlmod_load_module &nbsp;is called (dlmod.c)<o:=
p></o:p></span></li><li class=3D"MsoListParagraph" style=3D"margin-left:0cm=
;mso-list:l0 level1 lfo1"><span lang=3D"EN-US" style=3D"font-size:10.0pt;fo=
nt-family:&quot;Arial&quot;,sans-serif">Inside that function, function dl_i=
nit is called in turn<o:p></o:p></span></li><li class=3D"MsoListParagraph" =
style=3D"margin-left:0cm;mso-list:l0 level1 lfo1"><span lang=3D"EN-US" styl=
e=3D"font-size:10.0pt;font-family:&quot;Arial&quot;,sans-serif">From my dyn=
amic loadable module, the function init_... is called (I checked it adding =
it a return value and
 capturing it in function dlmod_load_module and showing by means of DEBUGMS=
GTL) &nbsp;but I don&#8217;t see the log at the beginning of function init_=
... (I use &#8220;DEBUGMSGTL&#8221;). So this leads me to suspect there is =
some problem. I have investigated a lot but with no results
 &#8230; <o:p></o:p></span></li></ol>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif">Any ideas?
<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif">Thank you very much.<o:p></o:p></span>=
</p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif">Jose.
<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span lang=3D"EN-US" style=3D"font-size:10.0pt;font-=
family:&quot;Arial&quot;,sans-serif"><o:p>&nbsp;</o:p></span></p>
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