[syslog-ng] [EXTERNAL] Re: Syslog-ng don't Listening UDP packets PORT(514) - Problem History

Fri Nov 8 20:07:50 UTC 2019

One must remember that packet loss using UDP is normal. To check to see if you are experiencing any lost packets issue this command:

netstat -su

Look at the value for 'receive buffer errors'. This is a cumulative count of lost UDP packets. Normally, this number should be zero. If the number is greater than zero, then you are losing UDP packets.

I have found that adding this to your syslog-ng config file on the 'source' statement is helpful:
so-reuseport(1) so_rcvbuf(80000000)

Also, increasing these values in 'sysctl' is also helpful
net.core.rmem_max
net.core.rmem_default
net.ipv4.udp_mem

Bryan Klimek
Mayo Clinic

From: syslog-ng [mailto:syslog-ng-bounces at lists.balabit.hu] On Behalf Of William Luiz Ribeiro Vasconcelos Da Silva
Sent: Friday, November 08, 2019 10:47 AM
To: Syslog-ng users' and developers' mailing list
Subject: [EXTERNAL] Re: [syslog-ng] Syslog-ng don't Listening UDP packets PORT(514) - Problem History

Hello Again,

The anwser of command is this:

netstat -anu |grep 514
udp        0      0 10.46.105.34:514        0.0.0.0:*

Only one line as expected.

When I try to start the syslog-ng using the command, I see the following error:

"[2019-11-08T13:37:32.326014] WARNING: Your configuration file uses an obsoleted keyword, please update your configuration; keyword='use_rcptid', change='This has been deprecated, try use_uniqid() instead', location='/etc/syslog-ng/syslog-ng.conf:24:4'
[2019-11-08T13:37:32.326240] Module loaded and initialized successfully; module='system-source'
[2019-11-08T13:37:32.326505] Module loaded and initialized successfully; module='sdjournal'
[2019-11-08T13:37:32.327037] Module loaded and initialized successfully; module='kvformat'
[2019-11-08T13:37:32.327073] Finishing include; content='block parser iptables-parser() at /usr/share/syslog-ng/include/scl/iptables/iptables.conf:23', depth='3'
[2019-11-08T13:37:32.327479] Module loaded and initialized successfully; module='csvparser'
[2019-11-08T13:37:32.327591] Finishing include; content='block parser sudo-parser() at /usr/share/syslog-ng/include/scl/sudo/sudo.conf:23', depth='3'
[2019-11-08T13:37:32.327669] Finishing include; content='parser generator app-parser', depth='2'
[2019-11-08T13:37:32.327709] Finishing include; content='source generator system', depth='1'
[2019-11-08T13:37:32.328122] Module loaded and initialized successfully; module='afsocket'
[2019-11-08T13:37:32.328504] Module loaded and initialized successfully; module='affile'
[2019-11-08T13:37:32.329762] Processing @include statement; filename='/etc/syslog-ng/conf.d/*.conf', include-path='/etc/syslog-ng:/usr/share/syslog-ng/include'
[2019-11-08T13:37:32.329836] Error creating persistent state file; filename='/var/lib/syslog-ng/syslog-ng.persist-', error='Permission denied (13)'"

Could this be the reason for not capturing UDP packets?

Tks,

William Luiz
________________________________
De: syslog-ng <syslog-ng-bounces at lists.balabit.hu> em nome de Zoltan Pallagi (zpallagi) <Zoltan.Pallagi at oneidentity.com>
Enviado: sexta-feira, 8 de novembro de 2019 13:31
Para: Syslog-ng users' and developers' mailing list <syslog-ng at lists.balabit.hu>
Assunto: Re: [syslog-ng] Syslog-ng don't Listening UDP packets PORT(514) - Problem History

Hi,

The most likely reason that another application also listens on this IP:port pair (it is possible in case of UDP and in that case the packet will be captured by the app started later)
Check the output of netstat -anu |grep 514 when syslog-ng does not capture the udp packets. You should see only one line here.

In other case, you should check the debug log of syslog-ng (syslog-ng -Fevd) perhaps there is some useful information.
________________________________
Feladó: syslog-ng <syslog-ng-bounces at lists.balabit.hu>, meghatalmazó: William Luiz Ribeiro Vasconcelos Da Silva <wsilva_ericsson at timbrasil.com.br>
Elküldve: 2019. november 8., péntek 16:28
Címzett: syslog-ng at lists.balabit.hu <syslog-ng at lists.balabit.hu>
Tárgy: [syslog-ng] Syslog-ng don't Listening UDP packets PORT(514) - Problem History

CAUTION: This email originated from outside of the organization. Do not follow guidance, click links, or open attachments unless you recognize the sender and know the content is safe.

Good Morning,

  Yesterday, we performed the first test of syslog-ng 3.24 OSE on a RHEL 7.6 VM in our customer's production environment.

  And we identified a very strange behavior.

  We saw through tcpdump that packets were being received by the network card but were not captured by syslog-ng.

  We have a UDP packet send simulator, and when I was pointing my simulator to another IP on the same machine(the users' connection IP), syslog-ng does the capping and consequently the treatment we put into the syslog-ng.conf file.

  What kind of TROUBLESHOOTING we can do in order to identify the reason for syslog-ng to capture packets on the users' connection IP, but for the application connection IP, it doesn't identify anything.

  It is informed by the client at the beginning of our project that syslog should always capture all UDP packets received by the application IP.

  This is the configuration of the "source" we have on this machine in our client's productive environment.

source s_model {
   #udp(port(514));
   udp(ip(10.46.105.34) port(514));
   # udp();
   #network(transport("udp"));
   #network(
   #   ip("10.46.105.34")
   #   transport("udp")
   #);
};

Tks,

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