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Libnetmeas

libnetmeas is a library designed we wrote in order to help TCP researchers to automatically log TCP variables such as cwnd, ssthresh, RTT, etc. The library, written in C language using glib, is built upon Web100 library and exports an easy to use API in order to be easily integrated in existing applications.

Requirements

Requirements to use the library are the following:

  • You have to run a web100 patched kernel
  • libweb100 (included in web100 userland utilities) must be installed
  • (Optional) If you want to change the congestion control algorithm you must run kernels > 2.6.12

Instructions to patch and install a web100 kernel can be found at Web100 website.

Library description

Once a working linux web100 kernel has been built you will be able to use the libnetmeas in your applications. In order to use the library it is sufficient to use the following C function:

  gboolean init_tcpstats(const gchar *lport_token, gint sfreq);

This function initializes the tcpstats internal thread which automatically logs all flows which match the lport_token string creating a file tcp_CID_timestamp.txt where CID is the connection ID and timestamp is the UNIX timestamp of the first data logged. lport_token is the local port to listen, a range of ports or a list of ports (for further details see the documentation).

Moreover it is possible to set the congestion control algorithm using the following function:

  void set_congestion_control (gint cong);

Integrating the library in an existing applitation is as easy as calling init_tcpstats() and linking the application to libnetmeas (see library documentation for further details).

Usage Example

We patched iperf in order to automatically log TCP variables. We just modified the Makefile.rules adding libnetmes library:

  LIBS = `pkg-config glib-2.0 --libs` -lweb100 \
         `pkg-config gthread-2.0 --libs` -lnetmes

Moreover we modified Listener.cpp adding the following code in Listener::Run() method:

  char *port;
  port = (char *)malloc (20);
  sprintf(port,"%d",mSettings->mPort);
  init_tcpstats (port,10);

And obviously including the header tcpstats.h in Listener.cpp. Running iperf -s will now automatically generate logfiles for each flow.