Re: SNMPD v5.8 Error opening specified endpoint

On Thu, Aug 23, 2018 at 9:24 AM Martin Frlin <[email protected]> wrote:

> Ok, additional information.
> Compare this line in v5.8:
> https://sourceforge.net/p/net-snmp/code/ci/master/tree/agent/agent_trap.c#l358
> with this line
> https://sourceforge.net/p/net-snmp/code/ci/v5.7.3/tree/agent/agent_trap.c#l251
>
> You will see that v5.7 does not set a source. And because it does not set
> a source it does not bind.
>
> But maybe we want to bind? (Source says we want to reduce open ports but I
> don't understand this)
>
> Ok, but why bind on port 161? If understand correctly we want to SEND
> traps. So we should bind localhost:<random high level port> ->
> localhost:162 (address of our snmptrapd), but this does not happen.
> Instead we get (note that netsnmp prints to->from):
> netsnmp_udpbase: binding socket: 9 to UDP: [0.0.0.0]:0->[127.0.0.1]:161
> netsnmp_udpbase: socket 9 bound to UDP: [127.0.0.1]:162->[127.0.0.1]:161
>
> So why is socket bound on port 161 instead of some random high level port?
> I didn't find where in code port 161 is set.
>

It comes from the code that parses transport specifications.  But it's
assuming that it's parsing a destination, not a source.  Even if you told
that code that you were doing the lookup in the context of a trap, it would
use 162.

So I think the solution is that either port is unbound or random high level
> port is chosen for binding.
>
> I've also tried to set
> clientaddr 127.0.0.1:<some high level port>
> clientaddrUsesPort yes
> because documentation says this will be used for clients but it also does
> not work.
>

Can you try adding "-s 127.0.0.1:<some high level port>" to your trapsink
line instead?  You can also try ":0".

I found a few bugs in the clientaddr changes before 5.8 went out, but I
don't use trapsink so didn't notice this one.  There are a bunch of hacks
in the clientaddr support that would clearly have been better to push into
the transport parsing instead.

  Bill


> V V čet., 23. avg. 2018 ob 11:47 je oseba Martin Frlin <
> [email protected]> napisala:
>
>> If you have line:
>> trapsink     localhost public
>> in your config v5.8 fails to start. Meanwhile v5.3 starts with no
>> problems.
>>
>> Am I missing something or is this a bug?.
>>
>> This output was generated using exactly the same config
>> v5.8
>> # snmpd -Dnetsnmp_udpbase -Lo -f
>> registered debug token netsnmp_udpbase, 1
>> Log handling defined - disabling stderr
>> netsnmp_udpbase: open remote UDP: [127.0.0.1]:162->[0.0.0.0]:0
>> netsnmp_udpbase: binding socket: 9 to UDP: [0.0.0.0]:0->[127.0.0.1]:161
>> netsnmp_udpbase: socket 9 bound to UDP: [127.0.0.1]:162->[127.0.0.1]:161
>> Turning on AgentX master support.
>> netsnmp_udpbase: open local UDP: [127.0.0.1]:161->[0.0.0.0]:0
>> netsnmp_udpbase: set IP_PKTINFO
>> netsnmp_udpbase: binding socket: 8 to UDP: [0.0.0.0]:0->[127.0.0.1]:161
>> netsnmp_udpbase: failed to bind for clientaddr: 98 Address already in use
>> Error opening specified endpoint "udp:127.0.0.1:161"
>> Server Exiting with code 1
>>
>>
>> v5.3
>> # snmpd -Dnetsnmp_udpbase -Lo -f
>> registered debug token netsnmp_udpbase, 1
>> Log handling defined - disabling stderr
>> netsnmp_udpbase: open remote UDP: [127.0.0.1]:162->[0.0.0.0]:0
>> netsnmp_udpbase: client open UDP: [127.0.0.1]:162->[0.0.0.0]:0
>> Turning on AgentX master support.
>> netsnmp_udpbase: open local UDP: [127.0.0.1]:161->[0.0.0.0]:0
>> netsnmp_udpbase: set IP_PKTINFO
>>
>
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