[Bro] Bro performance issues

Tomer Teller djteller at gmail.com
Sun Oct 30 02:46:16 PDT 2011

Hey all,

I am testing Bro's performance using tcpreplay for some project of mine.

I am using a packet capture of 680000 packets using different rates to
check for packet loss.

tcpreplay  -i eth0 --mbps=X 680000.pcap (where X = 1000,500,100,10)

I am registered on the new_packet event in order to count packets like so:

global ctr = 0;
event new_packet (c: connection,p: pkt_hdr)
   ctr = ctr + 1;

I write to log every time ctr % 100,000 = 0 to avoid unnecessary I/O to

On the sender side i see that all packet was transmitted successfully as
well as on the receiver side (using tcpdump), i.e. it is not libpcap issue.

Bro on the other hand, doesn't see all 680000, he sees around 540,000.

I also used smaller packet captures (10/30/100 packets), again, bro does
not see all packets.
Note! Packet captures are valid (checksum) HTTP connections that i recorded
for testing.

I tried removing some analyzers using broctl as well as modifying local.bro.
Also followed the Bro performance tuning.

Nothing helps, Bro does not see all the packets.

Any ideas what is the problem?
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