[Bro-Dev] timer delays between different events for same connection

Aashish Sharma asharma at lbl.gov
Thu Apr 12 21:30:12 PDT 2018

So I am seeing some weird stuff in my sample pcap of scanners. May be too
obvious and I am just not seeing why/how of it. 

Here is the issue : ( I have time in human format for easier read): 

SO I just pick one session from conn.log  and this is the connection in
question: (there are many more like this): 

$ fgrep CspAa42NoEGEaXK4ci conn.log  | cf
Apr 12 05:37:42 CspAa42NoEGEaXK4ci 45107    23      tcp     -       -       -       -       S0      F       T       0       S       1       40      0       0       -

Now as part of debugging I have dumped network_time for various events which
process this connection: 

Apr 12 05:37:42 new_connection  CspAa42NoEGEaXK4ci
Apr 12 06:13:48 connection_attempt  CspAa42NoEGEaXK4ci
Apr 12 06:13:48 connection_state_remove  CspAa42NoEGEaXK4ci

Now my understanding is there are various timers involved upon whose expirations
bro infers events such as connection_attempt,  connection_reset etc etc. Timers
such as tcp_attempt_delay, tcp_SYN_timeout, tcp_close_delay amongst others. But
all these timers are generally 5 seconds. 

Q. Why would connection_attempt event kick in after 36 minutes and 6 seconds ? (
06:13:48 - 05:37:42 ) ? 

I have a pcap to share if anyone is interested and replicate on their end.


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