Sending UDP/514 data magically appears in syslog without rsyslog running

Posted by ale on Super User See other posts from Super User or by ale
Published on 2013-10-29T09:44:53Z Indexed on 2013/10/29 9:59 UTC
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Filed under:

linux

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centos

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udp

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rhel

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syslog

I’m using a programming language without a library to log to rsyslog over UDP. I thought I was going to need to write a library but I discovered something weird.

If I send data on UDP/514 with the port open on the server then the data appears in the server’s syslog. rsyslogd isn’t running so syslog isn’t doing this. Data doesn’t get formatted into a syslog message so rsyslogd really isn’t doing this (only raw text enters syslog). Linux must see the data coming in on this port and know that it should go into /var/log/messages?

If I do the same on another port (e.g. UDP/515) then nothing appears in the log!

What is doing this? Some CentOS feature? The kernel?

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