[stunnel-users] CPU 100%

Eric Eberhard flash at vicsmba.com
Thu Oct 18 01:56:00 CEST 2018

Long ago I had a server with a bad network card.  Every once in a while it
would spew uncontrollable bytes onto the network.  If you open a stunnel
connection and it does that this could very well be the problem.  If it
cheap, try changing the network card.  If not, you should be able to look in
your firewall/router and it will tell you who is sending what bytes to
whomever.  See if that machine is indeed streaming the bytes in massive
quantities.  If not, I would suspect your stunnel is getting stuck in it's
own loop.  There are a million reasons this can happen (well a few less than
a million) - such as maybe a bad library in the FreeBSD or a bad choice in
the Makefile - such as doing threads or something in a way your O/S does not
like (I use threads=fork or whatever it is, instead of actual threading).
You might tinker with some of the options that make the stunnel build and
try different ones.  Especially if stunnel was compiled on a different
version of the O/S - could be differences in bytes in things and who knows


That is all I can suggest beyond setting the debug level to 7 (I think is
highest) and then watching the log file.




From: stunnel-users [mailto:stunnel-users-bounces at stunnel.org] On Behalf Of
Murrey, Brian J.
Sent: Wednesday, October 17, 2018 10:57 AM
To: stunnel-users at stunnel.org
Subject: [stunnel-users] CPU 100%


We are running stunnel 5.49 on FreeBSD 11.2 and we're running into a problem
once in a while. 


CPU pegs at 100% when we get an stunnel connection from one of our external

This affects 100% of all cores and we can't even log in to console.


To mitigate this temporarily, we have a script running in the background to
watch when stunnel begins to spike and restarts the daemon.


It doesn't happen 100% of the time, and so far I have been unable to
distinguish what makes the connection do this to the CPU. 


Have any of you run in to this issue? 






Brian Murrey
System Engineer II, IT Infrastructure



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