Simulate lacking internet connections

simulate-connectivity-issues.sh

#!/bin/bash
#
# Needs to be run as root!

# between 0 (never flakey) and 100 (regularly flaky)
flakiness=20

# max delay in seconds
max_delay_normal=8
max_delay_flakey=300

device="wlp0s20f3"

set -x

logfile="/tmp/simulate-connectivity-issues.log"
echo "Log file: $logfile"
: > "$logfile"

init() {
    { nodelay > /dev/null 2> /dev/null ; tc qdisc add dev "$device" root netem delay 0s ; } && (echo "Init complete" >> "$logfile")
}

random_delay() {
    time=$(( RANDOM % $max_delay_flakey ))
    echo "Adding delay of $time seconds..." >> "$logfile"
    tc qdisc change dev "$device" root netem delay ${time}s && (echo "Adding delay of $time seconds...DONE" >> "$logfile")
    printf "\rDelay: ${time} seconds                              \r"
}

random_sleep() {
    time=$(( RANDOM % 20 ))
    echo "Sleeping for $time seconds..." >> "$logfile"
    sleep $time
    echo "Sleeping for $time seconds...done" >> "$logfile"
}

nodelay() {
    time=$(( RANDOM % $max_delay_normal ))
    echo "Changing to no delay..." >> "$logfile"
    tc qdisc change dev "$device" root netem delay ${time}s && (echo "Changing to no delay...DONE" >> "$logfile")
    printf "\rDelay: $time seconds                              \r"
}

cleanup() {
    status=$?
    echo "cleanup..."
    tc qdisc delete dev "$device" root netem || echo 'Failed to undo settings'
    echo "cleanup...done"
    exit $status
}

trap "cleanup" INT TERM EXIT

init
nodelay

while :; do
    if [[ $(( RANDOM % 100 < $flakiness )) -eq 1 ]]; then
        random_delay
        random_sleep
    fi
    nodelay
    random_sleep
done