Here are three scripts demonstrating Maxwell's scripting capability.

#1 Initiate a DHCP impairment.

#2 initiate a user configured IPv4 fragmentation impairment on only UDP packets.

#3 Enable jitter on all frames.

#1  Initiate a DHCP Impairment

#!/bin/bash

# This file illustrates one way to control impairments from a shell script.
# The specific example in this script initiates a DHCP impairment.

# If the standard impairment server program (stdiserver) is not already running
# with the desired plugin, if any, then the first step is to start the standard
# impairment server with the desired plugin.
# We'll assume any already running stdiserver process is not loaded with the
# desired plugin, so we first kill any previously running stdiserver process.

pkill stdiserver
sleep 1 # Wait a second for the process to exit.

# Since this is an example that performs an impairment to DHCP packets, we must
# use the TCP/IP impairment plugin. We must specify the entire path to the
# plugin file and redirect the standard file descriptors in order to place the
# server in the background.

stdiserver -L /usr/local/lib/iwl/ip_plugins/tcpip_plugin.so \
        < /dev/null > /dev/null 2>&1 &
sleep 1 # Wait a second for the process to finish initializing.

# The following is not strictly needed, but is used here to display the
# description of the control fields for the plugin. The meaning of its
# output can be determined by studying the standard_impairment_apis.pdf
# document and reading the help in the nstdigui.py GUI control application.
# It should provide an understanding on how to change the arguments passed to
# the setplugin commands below so as to customize them.

getpluginmeta

# For flow 0 (whose default match criteria matches all packets) we want to
# set both interfaces (0 and 1) to perform the following impairment:
# Under IPv4 tests (also known as protocol group 050) select the DHCP
# impairment set of tests (set number 15), and test 18 within that set.
# That test sets the server host name and boot file name to non-null terminated
# values inside the DHCP client response.
# The following two commands start the requested impairment:

setplugin 0 0 on init button 0 num 0 15 num 1 18
setplugin 0 1 on init button 0 num 0 15 num 1 18

# Print the plugin settings to insure we set them to our desired values:

getplugin 0 0
getplugin 0 1

# This runs the impairment for an hour (or until the break key is pressed) by
# putting this script to sleep and then killing the server process just before
# the script exits. There are of course many other possible ways to handle the
# situation, such as issuing commands to clear any flow matches and impairments
# that have been set and keep stdiserver running so as to allow traffic to flow
# through Maxwell even after this script exits.

sleep 3600
pkill stdiserver

==============================================================
#!/bin/bash

# This file illustrates one way to control impairments from a shell script.
# The specific example in this script initiates a user configured IPv4
# fragmentation impairment on only UDP packets.

# If the standard impairment server program (stdiserver) is not already running
# with the desired plugin, if any, then the first step is to start the standard
# impairment server with the desired plugin.
# We'll assume any already running stdiserver process is not loaded with the
# desired plugin, so we first kill any previously running stdiserver process.

pkill stdiserver
sleep 1 # Wait a second for the process to exit.

# Since this is an example that performs an IPv4 impairment to datagrams, we
# must use the TCP/IP impairment plugin. We must specify the entire path to the
# plugin file and redirect the standard file descriptors in order to place the
# server in the background.

stdiserver -L /usr/local/lib/iwl/ip_plugins/tcpip_plugin.so \
        < /dev/null > /dev/null 2>&1 &
sleep 1 # Wait a second for the process to finish initializing.

# The following is not strictly needed, but is used here to display the
# description of the control fields for the plugin. The meaning of its
# output can be determined by studying the standard_impairment_apis.pdf
# document and reading the help in the nstdigui.py GUI control application.
# It should provide an understanding on how to change the arguments passed to
# the setplugin commands below so as to customize them.

getpluginmeta

# For flow 0 we want to fragment only in one direction so we set just one
# interface (0) to perform the following impairment:
# Under IPv4 tests (known as protocol group 050 in the docs or radio button 0
# in the plugin control metadata) we select the Fragment impairment set of
# tests (set number 10), and test 23 within that set. That test provides a way
# for a user to customize the fragmentation.
# This example customization sets each fragment to contain 16 bytes with 8 byte
# overlap and sends the fragments in reverse order.
# The following command selects and starts the requested impairment:

setplugin 0 0 on init button 0 num 0 10 num 1 23 num 2 16 num 3 8 num 4 0

# Print the plugin settings to insure we set them to our desired values:

getplugin 0 0

# This is where we set flow 0, interface 0 so the fragmentation is applied only
# to UDP datagrams flowing into interface 0:

setmatch 0 0 IPv4 Proto 17 0xff

# Print the match setting to insure we set them to our desirec values:

getmatch 0 0

# This runs the impairment for an hour (or until the break key is pressed) by
# putting this script to sleep and then killing the server process just before
# the script exits. There are of course many other possible ways to handle the
# situation, such as issuing commands to clear any flow matches and impairments
# that have been set and keep stdiserver running so as to allow traffic to flow
# through Maxwell even after this script exits.

sleep 3600
pkill stdiserver


=================================================================================

#!/bin/bash

# This file illustrates one way to control impairments from a shell script.
# The specific example in this script enables jitter on all frames.

# If the standard impairment server program (stdiserver) is not already running
# then the first step is to start the standard impairment server. (We do not
# need to load a plugin since jitter impairments are standard impairments
# already built into the server.)
# We'll assume any already running stdiserver process is in an unkown state
# and it is simpler to kill and restart it in a known state.

pkill stdiserver
sleep 1 # Wait a second for the process to exit.

# This example needs no plugins. So when we start the server we only need to
# redirect the standard file descriptors in order to place the server in the
# background.

stdiserver < /dev/null > /dev/null 2>&1 &
sleep 1 # Wait a second for the process to finish initializing.

# Please read /usr/local/iwl/docs/standard_impairment_apis.pdf
# for more information on the following commands.

# We set the packets traveling from interface 0 to interface 1 to be delayed
# (jittered) a random amount of time between 0 and 0.1 seconds. Any value
# between 0 and 0.1 seconds is equally probable.
# Packets traveling from interface 1 to interface 0 will be delayed (jittered)
# a random amount of time from 0 to about 4294 seconds, but most probably 0.01
# seconds with a standard deviation of 0.007 seconds. The probability of the
# delay follows a Gaussian distribution with an upper limit of ~4294 seconds.

setimpair 0 0 zerostats jitter 100 linear 0 100000 reorderok
setimpair 0 1 zerostats jitter 100 gaussian 10000 7000 reorderok

# Print the impairment settings to insure we set them to our desired values:

getimpair 0 0
getimpair 0 1

# On exit from this script the impairment will continue to run until the
# stdiserver process is killed or the impairment is changed using another
# script or using the nstdgui.py GUI control application.