How to simulate network latency and errors on macosx

latency.sh

#! /bin/sh

# --
# How to simulate network latency and errors on macosx.
# 
# After this you can access the 127.0.0.10 as an alias
# to your localhost, but with a roundtrip delay.
#
# delay 150ms adds the delay to the given pipe (*)
# plr 0.05 simulates packet loss.
# bw 1Mbit/s limits the bandwidth.
# 
# Use "ipfw list" and "ipfw delete" to remove this setup.
#
#
# (*) According to my tests the delay will be more then 2x
# the value you entered, so best to check the result with ping.
#
# --

sudo ifconfig lo0 inet 127.0.0.10 netmask 255.255.255.255 alias

sudo ipfw add pipe 1 ip from any to 127.0.0.10
sudo ipfw add pipe 2 ip from 127.0.0.10 to any

sudo ipfw pipe 1 config delay 150ms bw 1Mbit/s plr 0.05
sudo ipfw pipe 2 config delay 150ms bw 1Mbit/s plr 0.05