8. n2disk Timeline Module

This module can be used to seamlessly extract traffic from a n2disk timeline using the PF_RING API. n2disk is a traffic recording application producing multiple PCAP files (a per-file limit in duration or size can be used to control the file size), an index per file, and a timeline for keeping all the files in chronological order. Thanks to this module it is possible to query the timeline for specific packets belonging to the whole dump set in a given time interval, matching a specific BPF filter.

8.1. Requirements

Install pfring and n2disk following the instruction at http://packages.ntop.org according to your linux distribution and load the PF_RING kernel module as explained in the Installing from Packages section.

systemctl start pf_ring

8.2. Creating a dump set with n2disk

This module extracts traffic from a n2disk dump set consisting of PCAP files, index files, and a timeline. In order to instruct n2disk to create on-the-fly indexes you should use the -I option. The -A <path> option instead should be used to create a timeline in <path>.

Command line example:

n2disk -i eth1 -o /storage/n2disk/eth1 -I -A /storage/n2disk/eth1/timeline

For additional options please refer to the n2disk Documentation.

8.3. Usage

In order to tell PF_RING that you want to select the timeline module, you should use the “timeline:” prefix followed by the timeline path as interface name. In addition to this, it is mandatory to provide a BPF filter containing at the beginning the time interval using “start” and “end” tokens, followed by the actual packet filter (a subset of the BPF syntax is supported, please refer to the n2disk documentation) as in the example below:

pfcount -i timeline:/storage/n2disk/eth1/timeline -f "start 2016-09-22 8:40:53 and end 2016-09-22 10:43:54 and host"

A specific example pftimeline is also available in the PF_RING examples folder. You can use pftimeline to extract traffic generating a PCAP file with the matching traffic, or to pipe another application for processing the matching traffic directly. Example:

pftimeline -t /storage/n2disk/eth1/timeline -b "2018-07-21 8:40:53" -e "2018-07-21 10:43:54" -f "host" -o - | tshark -i -

8.4. Wireshark support

One of the most common use cases for the timeline module is the Wireshark integration, in fact it is very convenient to run wireshark directly on a n2disk timeline, specifying a BPF filter for extracting a small portion of the whole dump set, and starting the analysis task while the extraction is progressing. In order to do this, you can use the extcap modules we provide for Wireshark as described at https://github.com/ntop/wireshark-ntop