[Bro] wrong size computation

Vincenzo Falletta falletta at ftw.at
Mon Nov 28 10:34:54 PST 2005

Hi folks,
As regards the way bro deals with the number of bytes transferred for
each connection, it seems that bro DOES NOT keep a variable in which
incrementally stores the sum of each packet size for all the packets
involved in that very connection, but instead does a certain computation
 (i wonder how...) involving only the first and the last packet in the
connection... Am I correct?
I'm asking this question because I've found something very strange.
In bro's conn.log file there are lines like this:

Dec  1 00:22:53 1.058870 A B http 49331 80 tcp 886477697 ? RSTOS0 L

(yes it's correct, 800MB in 1 second) but if I look at the trace, this
is what I see:

     A              B
   49331  -->    80 (SYN)        Seq=0,Ack=0
   49331  <--    80 (ACK)        Seq=0,Ack=0
   49331  -->    80 (RST)        Seq=0,Ack=188164531

(Only 3 packets transferred...)

Of course there's some bug in these hosts, but bro should not be
misleaded in computing the amount of bytes transferred inside a
connection. Could someone explain me what's happening here?

Best regards,


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