If you specify trapsink line in form localhost:<port> it does not bind a
socket because it does not set a source in the piece of code I have linked.
Regarding why it binds to port 161 I don't understand your comment. I know
that destination port will be 162 because that is where the snmptrapd
listens (by default).
If someone can explain the reasoning why is binding happening if trapsink
is on localhost and not if it is on remote and why it always binds on port
161 thus creating a problem I could make a patch that resolves this issue.
V V pet., 24. avg. 2018 ob 19:57 je oseba Bill Fenner <fen...@gmail.com>
napisala:
> On Thu, Aug 23, 2018 at 9:24 AM Martin Frlin <martin.fr...@gmail.com>
> 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 <
>> martin.fr...@gmail.com> 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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