How to simulate network failures using socat proxies

README.md

• ./port-proxy-prepare.sh to create PID directory for running proxy
• ./sample-google-proxy.sh start to start listening 8443 and proxying traffic to google
• Configure client application to perform requests to localhost:8443 instead of www.google.com:443
• ./sample-google-proxy.sh stop to simulate situation when google is down
• Do client testing
• ./sample-google-proxy.sh start to simulate service up again

port-proxy-prepare.sh

#!/bin/sh -e
USER=$(whoami)
PID_DIR=/var/run/test-proxy
sudo mkdir -p $PID_DIR
sudo chown $USER $PID_DIR
echo Created PID directory for test-proxy

port-proxy.sh

#!/bin/bash
SOCAT=socat

if [ "$#" -ne 5 ]; then
	echo Usage:
	echo "$(basename $0) NAME SOURCE_PORT TARGET TARGET_PORT [start|stop]"
	exit 1
fi

NAME=$1
SOURCE_PORT=$2
TARGET=$3
TARGET_PORT=$4
COMMAND=$5

PID_FILE=/var/run/test-proxy/socat-$SOURCE_PORT

if [ "$COMMAND" = "start" ]; then
	if [ -e $PID_FILE ]; then
		PID_IN_PID_FILE=$(/bin/cat $PID_FILE)
		PID_STATUS=$(ps -p$PID_IN_PID_FILE -o pid=)
		if [ -n "$PID_STATUS" ]; then
			echo -e "[$NAME]\t\tProxy in $SOURCE_PORT is already started!"
			exit 0
		else
			rm $PID_FILE
			echo -e [$NAME]\t\tRemoved stale $PID_FILE
		fi
	fi
	$SOCAT TCP4-LISTEN:${SOURCE_PORT},reuseaddr,fork TCP4:$TARGET:$TARGET_PORT &
	echo $! > $PID_FILE
	echo -e "[$NAME]\t\tStarted proxy from $SOURCE_PORT to $TARGET:$TARGET_PORT"

elif [ "$COMMAND" = "stop" ]; then
	if [ -e $PID_FILE ]; then
		PID_IN_PID_FILE=$(/bin/cat $PID_FILE)
		PID_STATUS=$(ps -p$PID_IN_PID_FILE -o pid=)
        	if [ -z "$PID_STATUS" ]; then
       			echo -e "[$NAME]\t\tProxy in $SOURCE_PORT is already stopped!"
			rm $PID_FILE
                	echo Removed stale $PID_FILE
                	exit 1
        	fi
		kill -9 -$(ps -o pgid= $PID_IN_PID_FILE| grep -o '[0-9]*')
		rm $PID_FILE
		echo -e "[$NAME]\t\tStopped proxy from $SOURCE_PORT to $TARGET:$TARGET_PORT"
	else
		echo -e "[$NAME]\t\tCould not find $PID_FILE. Proxy in $SOURCE_PORT is already stopped?"
		exit 0
	fi
else
	echo Unknown command: $COMMAND
fi

sample-google-proxy.sh

#!/bin/sh
if [ "$#" -ne 1 ]; then
	echo Usage:
	echo "$(basename $0) [start|stop]"
	exit 1
fi

SOURCE_PORT=8443
TARGET=www.google.com
TARGET_PORT=443
./port-proxy.sh http-proxy $SOURCE_PORT $TARGET $TARGET_PORT $1