[Bro] Problem with connections in S1 and SF state

Sven Dreyer sven at dreyer-net.de
Thu Nov 19 08:21:57 PST 2015

Justin, thanks for the hint. I should indeed have checked the history field.

But even for connections that do not start with d or D in the history 
field, I see the same behaviour. Source and destination is still twisted:

1447675087.121817    CjRCD61gNErucciPb8    87.144.16.xxx 50993 
192.168.100.yyy    26577    tcp    ssl    83.596659 1432    2619    S1 
   F    T    0    ShADad    18    2164    15 3231    (empty)

Bro is configured to listen to a bridge interface (br0). But I also have 
running a dumpcap process writing all packets to pcap files. 
Interestingly, if I feed the corresponding pcap file to bro (bro -r 
file.pcap), I get source and destination in the right order:

1447675087.121817    C2AvJf3WgcdiBlYfS4    192.168.100.yyy 26577 
87.144.16.xxx    50993    tcp    ssl    83.596659 1432    2619    S1 
-    -    0    ShADad    18    2164    15 3231    (empty)

Does anybody have an explanation for this?


Am 17.11.2015 um 21:53 schrieb Azoff, Justin S:
> You should really be looking at the history field:
> history: string &log &optional
> Records the state history of connections as a string of letters. The meaning of those letters is:
> Letter	Meaning
> s	a SYN w/o the ACK bit set
> h	a SYN+ACK (“handshake”)
> a	a pure ACK
> d	packet with payload (“data”)
> f	packet with FIN bit set
> r	packet with RST bit set
> c	packet with a bad checksum
> i	inconsistent packet (e.g. SYN+RST bits both set)
> If the event comes from the originator, the letter is in upper-case; if it comes from the responder, it’s in lower-case. Multiple packets of the same type will only be noted once (e.g. we only record one “d” in each direction, regardless of how many data packets were seen.)
> So any connection that starts with D or d means bro missed the initial syn handshake (Sh)

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