gistfile1.rb

#!/usr/bin/env ruby

if ARGV.include? '--help'
  puts "simulate-network [speed-option] [lossiness-option]"
  puts ""
  puts "[speed-option] is one of:"
  puts "--edge - Simulate an EDGE (GPRS) wireless network"
  puts "--3g - Simulate a 3G wireless network"
  puts "--wifi - Simulate an average (but not great) WiFi network"
  puts ""
  puts "[lossiness-option] is optionally one of:"
  puts "--lossy - drop 1% of packets randomly"
  puts "--hellalossy - drop 33% of packets randomly"
  exit 1
end

speed_table_in = {
  'edge' => 'delay 400ms bw 240Kbit/s',
  '3g' => 'delay 100ms bw 780Kbit/s',
  'wifi' => 'delay 10ms bw 40Mbit/s',
}

speed_table_out = {
  'edge' => 'delay 400ms bw 200Kbit/s',
  '3g' => 'delay 100ms bw 330Kbit/s',
  'wifi' => 'delay 10ms bw 33Mbit/s',
}

lossy_table = {
  'lossy' => 'plr 0.01',
  'hellalossy' => 'plr 0.3',
}

speed = ARGV.map {|x| x.gsub(/^--/, '')}.detect { |x| speed_table_in.keys.include? x } || "wifi"
lossy = ARGV.map {|x| x.gsub(/^--/, '')}.detect { |x| lossy_table.keys.include? x }

puts "Finna gonna slow down your nets to #{speed} speed"
puts "Lossiness is enabled" if lossy

`sudo ipfw add pipe 1 dst-port 80,443 proto tcp > /dev/null 2>&1`
`sudo ipfw add pipe 2 src-port 80,443 proto tcp > /dev/null 2>&1`

lossy ||= '__NOTHERE__'
`sudo ipfw pipe 1 config #{speed_table_in[speed]} #{lossy_table[lossy] || ''}`
`sudo ipfw pipe 2 config #{speed_table_out[speed]} #{lossy_table[lossy] || ''}`

puts "Your network is now artificially slower - exit this shell via 'exit' to restore it to normal\n"
system "/usr/bin/login -f -lq $USER"

puts "Now back to full speed"
`sudo ipfw -q flush`