Simulate various network links. Useful e.g. for mobile development on localhost.

linksim.rb

# Usage
#
# To simulate lossy 3G on local connections to and from port 3004
# ruby linksim.rb up 3004 3g_lossy
#
# To clear ipfw rules
# ruby linksim down

conf = {
  :"3g_lossy" => {
    down: {
      bw: 780,
      delay: 100,
      plr: 0.01
    },
    up: {
      bw: 330,
      delay: 100,
      plr: 0
    }
  }
}

if __FILE__ == $0

  if ARGV[0] == "up"
    port = ARGV[1] || 3004
    key = (ARGV[2] || :"3g_lossy").to_sym
    c = conf[key]

    puts "Setting up ipfw pipes..."
    system("sudo ipfw pipe 1 config bw #{c[:down][:bw]}KByte/s delay #{c[:down][:delay]}ms plr #{c[:down][:plr]}")
    system("sudo ipfw pipe 2 config bw #{c[:up][:bw]}KByte/s delay #{c[:up][:delay]}ms plr #{c[:up][:plr]}")
    system("sudo ipfw add 1 pipe 1 ip from me to any src-port #{port}")
    system("sudo ipfw add 2 pipe 2 ip from any to me dst-port #{port}")
  else
    puts "Deleting ipfw pipes..."
    system("sudo ipfw delete 1")
    system("sudo ipfw delete 2")
  end

end