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ipfw jitter test script
#!/bin/bash
MIN_LAG=25
MAX_LAG=50
(( LAG_RANGE = MAX_LAG - MIN_LAG ))
TIME=600 # total test time (in seconds)
INTERVAL=0.1 # time in between changes in latency (in seconds)
STEPS=6000 # TIME / INTERVAL
# set up a pipe to add latency, which matches only *incoming*
# traffic from the localhost to the localhost
ipfw add 100 pipe 1 ip from 127.0.0.1 to 127.0.0.1 in
ipfw add 100 allow ip from 127.0.0.1 to 127.0.0.1 out
# set up initial random delay
(( delay = RANDOM % LAG_RANGE + MIN_LAG ))
echo "setting delay to" $delay "ms"
ipfw pipe 1 config delay ${delay}ms
# start ping background process and stash result in a file
ping -i 0.05 localhost > ping_out &
PING_PID=$! # remember the PID so we can kill it later
for ((i=0; i < STEPS; i++))
do
sleep $INTERVAL
# change the delay to a new random value
(( delay = RANDOM % LAG_RANGE + MIN_LAG ))
ipfw pipe 1 config delay ${delay}ms
echo "setting delay to" $delay "ms"
done
# kill the ping process
kill $PING_PID
# remove the pipe and the associated rule
ipfw delete 100
ipfw pipe 1 delete
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