[Bro] Stand-alone cluster problems

Tyler T. Schoenke Tyler.Schoenke at colorado.edu
Tue Jun 9 09:57:02 PDT 2009


Just wondering if anyone has run into this problem.  I'm running Robin's 
1.4 cluster code on a stand-alone AMD dual-core machine that is 
monitoring a 200 Mbit connection.  I've been running this setup for a 
couple months, and it has been working well.

I noticed that Bro seemed to be missing some packets, and Seth told me 
to look for DroppedPackets in the notice.log.  From what I recall, I was 
dropping upwards of 90% of the packets after filtering.  The strange 
thing was the primary bro process CPU usage seemed to be low (20-30%), 
even though it was dropping most of the packets.  I would have expected 
CPU to be high in trying to keep up.  Is there some throttling mechanism 
to prevent the CPU from being maxed out?

I turned on some restrict filters to bring the DroppedPackets down.  I 
turned off various things like HTTP, HTTPS, DNS, IMAP, SMTP, and a few 
others.  After that, the ratio of (packets dropped after filtering) to 
received was less than one percent.

So that is the history and here is my problem.  When I start the 
cluster, the above mentioned ratio will be less than 1%.  It remains 
less than 1% for several days to a week.  For no explicable reason, it 
will jump up as high as 99% and stay stuck there.   This has happened 
twice in the last couple weeks.  Whatever caused this problem also 
caused the logs to stop being rotated.  They are showing a timestamp of 
June 7th (MST).  When I run a cluster status, it shows the cluster is 
running, and I can see both bro-1.4-robin processes running, but their 
CPU usage has dropped down to 0.00%.  I think the CPU usage for one of 
those processes had typically been around 16-20% when the dropped ratio 
was less than 1%.

Restarting the cluster should clear the problem again for a few days. 
Is there any other troubleshooting I can do before restarting to 
determine the cause of the problem?

Below are a few lines showing the high ratio of dropped packets.  These 
are some of the last lines logged, so based on the timestamps, 
everything stopped around 01:48 6/8/09 GMT.

1244425212.229043:DroppedPackets:NOTICE_FILE:bro::::::::::317741 packets 
dropped after filtering, 387325 received, 1117174 on link::@26-c775-10c8ed
1244425222.229050:DroppedPackets:NOTICE_FILE:bro::::::::::16000 packets 
dropped after filtering, 68358 received, 192124 on link::@26-c775-10c91b
1244425236.737126:DroppedPackets:NOTICE_FILE:bro::::::::::311615 packets 
dropped after filtering, 341963 received, 979510 on link::@26-c775-10c939
1244425247.488693:DroppedPackets:NOTICE_FILE:bro::::::::::79770 packets 
dropped after filtering, 172843 received, 477468 on link::@26-c775-10c981
1244425261.942659:DroppedPackets:NOTICE_FILE:bro::::::::::315110 packets 
dropped after filtering, 315358 received, 878859 on link::@26-c775-10c987
packets dropped after filtering, 10878305 received, 31316595 on 

Here are some earlier logs showing what the ratio normally looks like.

1243649373.579172:DroppedPackets:NOTICE_FILE:bro::::::::::1752 packets 
dropped after filtering, 333996 received, 612544 on link::@88-1bd3-bd5af
1243649383.579295:DroppedPackets:NOTICE_FILE:bro::::::::::1333 packets 
dropped after filtering, 342521 received, 627890 on link::@88-1bd3-bd5c2
1243649393.579339:DroppedPackets:NOTICE_FILE:bro::::::::::920 packets 
dropped after filtering, 326511 received, 605614 on link::@88-1bd3-bd5d1
1243649403.579424:DroppedPackets:NOTICE_FILE:bro::::::::::1336 packets 
dropped after filtering, 318679 received, 615016 on link::@88-1bd3-bd5ec


Tyler Schoenke
IT Security Office
University of Colorado - Boulder

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