net-snmp-coders

Getbulk maximum message size

[Del B. Gabriel-A. <gab...@mo...>]

I am using Net-SNMP 5.3.0.1, and I am having problems with the size of =
the packets returned by getbulk.=20
=20
According to RFC 3416 (section 4.2.3):=20
=20
"   (1)   If the size of the message encapsulating the Response-PDU
          containing the requested number of variable bindings would be
          greater than either a local constraint or the maximum message
          size of the originator, then the response is generated with a
          lesser number of variable bindings. "
=20
However, it seems that when the msgMaxSize of the originator is =
exceeded, Net-SNMP agent doesn't respond at all (timeout is seen in the =
command generator). The checking of the packet size is done right before =
sending it (in _sess_async_send), so I guess it is not that easy to go =
back and remove varbinds at that point (even more is the packet is =
already encrypted).=20
=20
Is this functionality implemented in any other Net-SNMP version? Any =
ideas about where this should be implemented?

Thanks,
Gabriel

-- Gabriel Sebasti=E1n del Blanco=20
-- Motorola Software Group

Re: Getbulk maximum message size

[Robert S. <rs...@fr...>]

On Wed, 4 Jul 2007 11:24:06 -0400 Del wrote:
DBGA> I am using Net-SNMP 5.3.0.1, and I am having problems with the size of the packets returned by getbulk. 
DBGA>  [...]
DBGA> However, it seems that when the msgMaxSize of the originator is exceeded, Net-SNMP agent doesn't respond at all

Eeek. That's not good. Please file a bug report.

DBGA> Is this functionality implemented in any other Net-SNMP version? Any ideas about where this should be implemented?

Could you try 5.4.1.rc1? 

Re: Getbulk maximum message size

[Wes H. <har...@us...>]

>>>>> "RS" == Robert Story <rs...@fr...> writes:
DBGA> However, it seems that when the msgMaxSize of the originator is
DBGA> exceeded, Net-SNMP agent doesn't respond at all

RS> Eeek. That's not good. Please file a bug report.

Unfortunately, I believe the fix is not easy at all.  It'll require some
rework by the agent, but the agent doesn't do the packet building.  The
library does and it has no notion about how to remove packets from the
end of the varbind list to bring it back in range.  A per-packet
callback function that can be set by the agent or something will
probably be needed...
-- 
Wes Hardaker
Sparta, Inc.

RE: Getbulk maximum message size

[Del B. Gabriel-A. <gab...@mo...>]

Thanks for the responses. I will submit a defect report, and try to
implement the fix in the mean time.

Regards,
Gabriel

-----Original Message-----
From: Wes Hardaker [mailto:har...@us...]=20
Sent: Thursday, July 05, 2007 11:56 AM
To: Robert Story
Cc: Del Blanco Gabriel-AGD019; net...@li...
Subject: Re: Getbulk maximum message size

>>>>> "RS" =3D=3D Robert Story <rs...@fr...> writes:
DBGA> However, it seems that when the msgMaxSize of the originator is=20
DBGA> exceeded, Net-SNMP agent doesn't respond at all

RS> Eeek. That's not good. Please file a bug report.

Unfortunately, I believe the fix is not easy at all.  It'll require some
rework by the agent, but the agent doesn't do the packet building.  The
library does and it has no notion about how to remove packets from the
end of the varbind list to bring it back in range.  A per-packet
callback function that can be set by the agent or something will
probably be needed...
--
Wes Hardaker
Sparta, Inc.