[snmp] Problem with the snmpv3 context

[Josh Bers]

Tim and Birgit,

I hope to get some debug output to send you soon on this issue.

Tim, I'm not sure how it could be a UDP issue since the behavior changes for
SNMPv1 (it works fine).

Josh

> I dimly remember hearing that different UDP implementations throw  
> different
> exceptions when an intermediate router sends an 'unreachable' or the  
> local
> system reports 'no-route-to-host'. I'll ask the folks who reported  
> the problem what
> they did.
>

> -----Original Message-----
> From: snmp-bounces at snmp.westhawk.co.uk 
> [mailto:snmp-bounces at snmp.westhawk.co.uk] On Behalf Of Tim Panton
> Sent: Monday, March 26, 2007 4:37 AM
> To: List for discussion of the Westhawk SNMP stack
> Subject: Re: [snmp] Problem with the snmpv3 context
> 
> 
> 
> On 23 Mar 2007, at 21:16, Josh Bers wrote:
> 
> > I am seeing a problem while using version 5.1 of the stack 
> (running on 
> > linux, java 1.4.2_12) talking to an SNMP agent with version 3 with
> > privacy
> > and authentication turned on.
> >
> > The scenario is the following:
> >
> > The program repeatedly attempts to contact an agent that is
> > unreachable
> > (network cable unplugged). After a long period of time (>3 
> minutes)  
> > the
> > network cable is plugged back in.
> >
> > The stack behavior is:
> >
> > While disconnected, we see messages about USMDiscovery Bean 
> timing out 
> > trying to connect to the agent. The stack dump show 2 receivers
> > associated
> > with the disconnected target IP address (?) These timeouts are  
> > repeated for
> > each attempt (timeouts take ~20 seconds). When the cable is  
> > reconnected, the
> > 2 receiver threads suddenly die. No more USMDiscoveryBean timeouts  
> > are seen,
> > however, no every PDU that is sent times out waiting for a 
> response  
> > (makes
> > sense given that the receiver has died).
> >
> > Anyone else seen this? Know why? Any workaround? Swapping 
> to Version 1 
> > context solves the problem (but this is not desireable).
> >
> > Theory:
> > USMDiscovery Creates its own v3 context (not sure why it can't
> > reuse the one
> > created for the original PDU??) Somehow when it kills this context  
> > it kills
> > the context (or at least the receiver thread) of the PDU's 
> context...
> > (notify issue?)...
> 
> Ah, Interesting.
> 
> Do you have an ethereal trace of the packets - including ICMP 
> ? Combined with a debug log we should be able to find the problem  
> pretty fast.
> (other pressures permitting :-) )
> 
> I dimly remember hearing that different UDP implementations throw  
> different
> exceptions when an intermediate router sends an 'unreachable' or the  
> local
> system reports 'no-route-to-host'. I'll ask the folks who reported  
> the problem what
> they did.
> 
> Tim.
> 
> 
> 
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