FromCapDump Element Documentation

FromCapDump -- Click element; reads packets from a 'cap' output file

FromCapDump(FILENAME [, KEYWORDS])

Ports: no inputs, 1 output
Processing: agnostic
Drivers: userlevel
Package: analysis (core)

Reads TCP packet descriptors from a file produced by Mark Allman's 'cap' tool and emits the corresponding TCP packets. Here's an example 'cap' file:

   SND 0
   INF - cap v2.13
   SYN > 1046102982.856142 0 0 40 0
   SYN < 1046102982.931832 0 0 40 0
   DAT > 1046102982.931941 1 1 1500 1460
   ACK < 1046102983.156387 1 1 40 0
   DAT > 1046102983.156531 2 2 1500 1460
   ...
   DAT > 1046102996.137294 5068 5000 1500 1460 FIN
   ACK < 1046102996.215164 5068 5000 40 0 FIN

SYN, DAT, and ACK lines have the following fields: packet type, direction, timestamp (in seconds past the epoch), unique packet number, packet sequence number, packet IP length, payload length, and optional flags. The file may be compressed with gzip(1) or bzip2(1); FromCapDump will run zcat(1) or bzcat(1) to uncompress it. FromCapDump reads from the file named FILENAME unless FILENAME is a single dash `-', in which case it reads from the standard input. It will not uncompress the standard input, however. Output packets have timestamp, aggregate, paint, and packet number annotations. The paint annotation is 0 for data packets and 1 for acknowledgements. The first packet number annotation equals the unique packet number; the second equals the packet sequence number. Keyword arguments are:

STOP

Boolean. If true, then FromCapDump will ask the router to stop when it is done reading. Default is false.

ACTIVE

Boolean. If false, then FromCapDump will not emit packets (until the `active' handler is written). Default is true.

ZERO

Boolean. Determines the contents of packet data not set by the dump. If true (the default), this data is zero. If false, it is random garbage.

CHECKSUM

Boolean. If true, then output packets' IP, TCP, and UDP checksums are set. If false (the default), the checksum fields contain random garbage.

SAMPLE

Unsigned real number between 0 and 1. FromCapDump will output each packet with probability SAMPLE. Default is 1. FromCapDump uses fixed-point arithmetic, so the actual sampling probability may differ substantially from the requested sampling probability. Use the sampling_prob handler to find out the actual probability. If MULTIPACKET is true, then the sampling probability applies separately to the multiple packets generated per record.

FLOWID

String, containing a space-separated flow ID (source address, source port, destination address, destination port, and, optionally, protocol). Defines the IP addresses and ports on output packets. If no FLOWID is given, FromCapDump uses 1.0.0.1 1 2.0.0.2 2.

AGGREGATE

Unsigned integer. Defines the aggregate annotation for output packets. Default is 1. Only available in user-level processes.

Packets generated by FromCapDump always have IP version 4 and a correct IP header length. The rest of the packet data is zero or garbage, unless set by the dump. Generated packets will usually have short lengths, but the extra header length annotations are set correctly. FromCapDump is a notifier signal, active when the element is active and the dump contains more packets.

sampling_prob (read-only)

Returns the sampling probability (see the SAMPLE keyword argument).

active (read/write)

Value is a Boolean.

encap (read-only)

Returns 'IP'. Useful for ToDump's USE_ENCAP_FROM option.

filesize (read-only)

Returns the length of the FromCapDump file, in bytes, or "-" if that length cannot be determined.

filepos (read-only)

Returns FromCapDump's position in the file, in bytes.

stop (write-only)

When written, sets `active' to false and stops the driver.

FromIPSummaryDump, ToIPSummaryDump Mark Allman, "Measuring End-to-End Bulk Transfer Capacity", Proc. Internet Measurement Workshop 2001.

Generated by 'click-elem2man' from '../elements/analysis/fromcapdump.hh' on 24/May/2007.