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Overview to GIMS Capture Daemon

There are two basic components to the capture node software: capture-daemon, and The proxy handles all XML/RPC communication with the GIMS AM and UI, and manages starting any necessary capture processes and resulting capture files.

Below, specific description of how to install and get the capture daemon proxy running are given.


The capture daemon can be run as a standalone process, but is normally started up by the capd_proxy. capd_proxy should run in an unprivileged mode, thus capture-daemon should be installed as setuid root (or a privileged user that has appropriate access to network devices via libpcap) in order for it to have appropriate permissions to open capture devices, etc. It can be installed anywhere, but should be put on a file system with reasonable enough space for temporary measurement files to reside.

The present capabilities of the capture daemon with respect to packet transformations are:

  • prefix-preserving IP address anonymization
  • sampling (1-in-N or uniform probabilistic sampling)
  • aggregation into either simple byte/packet counts, or flow-records. By default, no aggregation is done and you'll get libpcap files with raw packet headers.

Separate capture-daemon processes will be started by capd_proxy for each active experiment. While there is some overhead involved with having multiple capture processes running at the same time, this architecture simplifies the problem of demultiplexing the appropriate packets for a given experiment. It also provides a level of isolation among experiments, and enables a separate O&M capture process to be running alongside any active experiment process (e.g., in order to capture *all* traffic on the wire).

The only software dependency for the basic functionality of capture-daemon is a working libpcap library.

For flow aggregation in IPFIX records, libyaf and libfixbuf are required. They are available at These tools should be compiled and installed prior to compiling the capture-daemon code. They have their own set of prerequisites, notably glib 2.6.4 or better. See the yaf/fixbuf documentation for more details.

From inside the capture-daemon subdirectory, configure and make, then sudo make install. (Make install just changes the capture-daemon binary to be suid root so that it can have permissions to set a net device in promiscuous mode. Alternatively, run as root.)

Requires python 2.6.

The capd_proxy handles all XML/RPC functions for configuring, starting, and stopping experiments. There are also interfaces for testing storage capabilities for an experiment, and for gathering information on running experiments.

Presently, storage functionality is included for:

  • sftp
  • Amazon S3

All storage functionality resides in It is designed in a fashion to allow addition of new storage repositories relatively easy.

From the capture daemon proxy, a separate process is started up to handle each storage type (s3, ssh, and local storage). This storage process handles checking for new files that can be uploaded, and also annotates the existing metadata for raw capture files prior to upload. Each individual file transfer is handled in a transient (Python) thread in order to avoid blocking the entire process on a single transfer. (Note that some work is yet to be done on ensuring the propagation of errors from storage uploads to the UI (and experimenters).) Storage functionality is almost entirely housed in the module.

The software dependencies for capd_proxy are related to the storage capabilities: the boto Python library is required for s3, and paramiko and pyCrypto are required for ssh. Each of these libraries can be quite easily installed (see depend subdirectory), but capd_proxy will successfully start up even if they are not present (you simply won't have the affected storage capabilities). (On debian linuxes, just do: apt-get install python-paramiko python-crypto python-boto.)

There are a few options to start up (python -h will show them). If capture-daemon is suid root or is running as root, you should simply be able to say "python" to get started. The output logging will immediately show what storage capabilities have been found (via installed python libraries). A simple script ( is supplied to do a basic startup of the proxy. This will cause the proxy to listen on any locally configured IP address and port 8001.