topic Re: UDP input acceptFrom overriding the catchall in Getting Data In

UDP input acceptFrom overriding the catchall

hiersdd — Thu, 28 Sep 2023 15:47:19 GMT

I have a generic catchall for syslog traffic that is breaking when i try and use an acceptFrom for a subnet.

--- Generic Catchall ----

[udp://514]

connection_host = ip

index = syslog

sourcetype = syslog

The catch all functions correctly when using a single specific IP going to specified index :

[udp://192.168.1.1:514]

host = srv-lb-2

connection_host = none

index = a10

sourcetype = syslog

But if I try and add a new UDP input to capture a full /24 to shove it in a separate index, that overrides/disables the generic input from the first one. I do see messages in the checkpoint index however the [udp://514] from the first block stops.

[udp://514]

acceptFrom = 192.168.2.0/24

connection_host = ip

index = checkpoint

sourcetype = syslog

Anyone know how to do this in a way that works please??

Thanks!

Re: UDP input acceptFrom overriding the catchall

gcusello — Thu, 28 Sep 2023 16:15:27 GMT

Hi @hiersdd,

are you working by GUI or conf files?

by GUI it isn't possible to configure two inputs with the same protocol and port.

If you need to configure more inputs using the same protocol and port but having different sources, you have to do this only by conf file.

Ciao.

Giuseppe

Re: UDP input acceptFrom overriding the catchall

hiersdd — Thu, 28 Sep 2023 19:37:57 GMT

Nope, I am using inputs.conf.

Re: UDP input acceptFrom overriding the catchall

gcusello — Fri, 29 Sep 2023 06:34:13 GMT

Hi @hiersdd,

my first hint is to use a syslogs server like rsyslog or syslog-ng so it receives syslogs also when Splunk is down.

You could also use the SC4S (https://splunkbase.splunk.com/app/4740) that's a syslog-ng and a Universal forwarder.

In this way you can easily manage inputs.

Anyway, did you tried to use an inpul like the following?

[udp://192.168.2.*:514] connection_host = ip index = checkpoint sourcetype = syslog

Ciao.

Giuseppe

Re: UDP input acceptFrom overriding the catchall

hiersdd — Tue, 24 Oct 2023 01:34:44 GMT

Thanks for the suggestion, I do admit and agree that the easiest and best option at this point is to just take the syslog-ng route but I was trying to figure out how to do this natively Splunk if possible. It does not seem like the IP wildcard works in a TCP/UDP stanza, at least not in my 9.X UF:

ie this did not work:

[udp://192.168.2.*:514]
connection_host = ip
index = checkpoint
sourcetype = syslog

Additionally, I think I have figured out that the problem with using the acceptFrom as I originally showed was that Splunk will only process the first stanza of any particular PORT so there can't be a "fall back to the catchall" type logic if you are only using [udp://514] or [tcp://514]. You CAN have a generic port stanza and an IP specific stanza and that arrangement will be honored ie:

[udp://192.168.1.1:514]

index=singularDeviceIndex

[udp://514]

index=catchallDeviceIndex

But I can't figure out how to make this work (or it just can't be done):

[udp://514]

acceptFrom=192.168.1.0/24

index=WhateversInThatSubnetOnly

[udp://514]

index=AnythingAndEverythingElse