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Pcap Savefile Apps

PcapReader and PcapWriter Apps (apps.pcap.pcap)

The PcapReader and PcapWriter apps can be used to inject and log raw packet data into and out of the app network using the Libpcap File Format. PcapReaderreads raw packets from a PCAP file and transmits them on its output port while PcapWriter writes packets received on its input port to a PCAP file.

DIAGRAM: PcapReader and PcapWriter
+------------+                          +------------+
|            |                          |            |
| PcapReader *---> output    input ---->* PcapWriter |
|            |                          |            |
+------------+                          +------------+

Configuration

Both PcapReader and PcapWriter expect a filename string as their configuration arguments to read from and write to respectively. PcapWriter will alternatively accept an array as its configuration argument, with the first element being the filename and the second element being a mode argument to io.open.

Tap (apps.pcap.tap)

The Tap app is a simple in-band packet tap that writes packets that it sees to a pcap savefile. It can optionally only write packets that pass a pcap filter, and optionally subsample so it can write only every /n/th packet.

DIAGRAM: pcaptap
           +-------------------+
   input   |                   |   output
      ---->* apps.pcap.tap.Tap *---->
           |                   |
           +-------------------+

Configuration

The Tap app accepts a table as its configuration argument. The following keys are defined:

— Key filename

Required. The name of the file to which to write the packets.

— Key mode

Optional. Either "truncate" or "append", indicating whether the savefile will be truncated (the default) or appended to.

— Key filter

Optional. A pflang filter expression to select packets for tapping. Only packets that pass this filter will be sampled for the packet tap.

— Key sample

Optional. A sampling period. Defaults to 1, indicating that every packet seen by the tap and passing the optional filter string will be written. Setting this value to 2 will capture every second packet, and so on.