[Bro] ip_bytes and pkts not set in conn.log for cropped UDP packets

[david at woist.net]

Hi all,

We use bro-2.4.1 to analyze pcap traces with cropped payload.
This works fine for TCP and ICMP packets, however orig_pkts,  
orig_ip_bytes, resp_pkts and resp_ip_bytes are all set to "0" in  
conn.log for the connections with cropped UDP packets (such as DNS  
packets with a snaplen of 42).
That is, we end up with a conn.log entry stating that no packets were  
observed for the corresponding connection.
I assume this is because no application analyzer is started.

How can we still get these fields updated?

(-C does not help and orig_bytes as well as resp_bytes are set  
correctly, also I noted that the event udp_contents is triggered for  
the packets).

Many thanks!
David