[kea-dev] Suggestions for DHCP packets logs

[Francis Dupont]

BTW I am not against to save the packets in binary, i.e., in pcap or
any common/standardized formats that tools like tcpdump or wireshark
handle.

Regards

Francis Dupont <fdupont at isc.org>

> The following are recommendations for implementing the logging of
> DHCP packets.

=> 0. the term logging is not appropriate for the content for packets.
I suggest "dumping".

> 3) flushing of packets logs

=> direct (i.e., write vs fwrite) I/O?

> 4) handle packets logs rotation

=> as you suggest no intermediate process or even library this seems to
be clearly required.

> When logrotate works in copytruncate mode on the packets logs, the following 
> happens while the log is being processed:
> - Kea CPU usage spikes to 100%
> - DHCP packets are being dropped (from the client point of view)

=> for the AFTR which is an one process tool I used a lot of small tricks
to avoid this kind of issue, i.e., never perform a "long" task without
slicing it with the packet handling. Note one can get the same issue
in a multi-process code when a critical lock is handled by a "long"
task...

Regards

Francis.Dupont at fdupont.fr