Howto - Transparent Proxy Using Squid

./configure --prefix=/usr/local \
   --sysconfdir=/etc/squid \
   --enable-epoll \
   --enable-snmp \
   --enable-removal-policies="heap,lru" \
   --enable-storeio="aufs,coss,diskd,null,ufs" \
   --enable-ssl \
   --with-openssl=/usr/kerberos \
   --enable-delay-pools \
   --enable-linux-netfilter \
   --with-pthreads \
   --enable-ntlm-auth-helpers="SMB,fakeauth" \
   --enable-external-acl-helpers="ip_user,ldap_group,unix_group,wbinfo_group" \
   --enable-auth="basic,digest,ntlm" \
   --enable-digest-auth-helpers="password" \
   --with-winbind-auth-challenge \
   --enable-useragent-log \
   --enable-referer-log \
   --disable-dependency-tracking \
   --enable-cachemgr-hostname=localhost \
   --enable-underscores \
   --enable-basic-auth-helpers="LDAP,MSNT,NCSA,PAM,SMB,YP,getpwnam,multi-domain-NTLM,SASL" \
   --enable-cache-digests \
   --enable-ident-lookups \
   --enable-follow-x-forwarded-for \
   --enable-wccpv2 \
   --enable-fd-config \
   --with-maxfd=16384

http_port 127.0.0.1:3128
http_port 192.168.0.1:3128 transparent

cache_dir ufs /usr/local/var/squid/cache 100 16 256
pid_filename /usr/local/var/squid/logs/squid.pid

visible_hostname gw.office.intern
cache_mgr bl00d@gw.office.intern

logformat combined %>a %ui %un [%tl] "%rm %ru HTTP/%rv" %Hs %<st "%{Referer}>h" "%{User-Agent}>h" %Ss:%Sh
access_log /usr/local/var/squid/logs/access.log squid
cache_log /usr/local/var/squid/logs/cache.log
cache_store_log /usr/local/var/squid/logs/store.log
useragent_log /usr/local/var/squid/logs/useragent.log
referer_log /usr/local/var/squid/logs/referer.log

acl localhost src 127.0.0.1/255.255.255.255
acl intern src 192.168.0.0/24
acl all src 0.0.0.0/0.0.0.0

acl manager proto cache_object
acl to_localhost dst 127.0.0.0/8

acl SSL_ports port 443 563
acl Safe_ports port 80 21 443 563 70 210 1025-65535
acl CONNECT method CONNECT

http_access allow intern
http_access allow localhost
http_access deny !Safe_ports
http_access deny all

acl QUERY urlpath_regex cgi-bin \? asp jsp php
cache deny QUERY

follow_x_forwarded_for deny all
http_reply_access allow all

# default squid options
# -D disables initial dns checks. If you most likely will not to have an
#    internet connection when you start squid, uncomment this
SQUID_OPTS="-D"

# Time to wait for Squid to shut down when asked. Should not be necessary
# most of the time.
SQUID_SHUTDOWN_TIMEOUT=100

/usr/local/var/squid/logs/access.log {
    weekly
    rotate 5
    copytruncate
    compress
    notifempty
    missingok
}
/usr/local/var/squid/logs/cache.log {
    weekly
    rotate 5
    copytruncate
    compress
    notifempty
    missingok
}
/usr/local/var/squid/logs/useragent.log {
    weekly
    rotate 5
    copytruncate
    compress
    notifempty
    missingok
}
/usr/local/var/squid/logs/referer.log {
    weekly
    rotate 5
    copytruncate
    compress
    notifempty
    missingok
}

/usr/local/var/squid/logs/store.log {
    weekly
    rotate 5
    copytruncate
    compress
    notifempty
    missingok
# This script asks squid to rotate its logs on its own.
# Restarting squid is a long process and it is not worth
# doing it just to rotate logs
    postrotate
      /usr/local/sbin/squid -k rotate
    endscript
}
[/quote]

8. put the following in /etc/rc.d/init.d/squid:

[code]
#!/bin/bash
# squid This shell script takes care of starting and stopping
# Squid Internet Object Cache
#
# chkconfig: - 90 25
# description: Squid - Internet Object Cache. Internet object caching is \
# a way to store requested Internet objects (i.e., data available \
# via the HTTP, FTP, and gopher protocols) on a system closer to the \
# requesting site than to the source. Web browsers can then use the \
# local Squid cache as a proxy HTTP server, reducing access time as \
# well as bandwidth consumption.
# pidfile: /usr/local/var/squid/logs/squid.pid
# config: /etc/squid/squid.conf

PATH=/usr/local/sbin:/usr/local/bin:/usr/bin:/sbin:/bin:/usr/sbin
export PATH

# Source function library.
. /etc/rc.d/init.d/functions

# Source networking configuration.
. /etc/sysconfig/network

# Check that networking is up.
[ ${NETWORKING} = "no" ] && exit 0

# check if the squid conf file is present
[ -f /etc/squid/squid.conf ] || exit 0

if [ -f /etc/sysconfig/squid ]; then
. /etc/sysconfig/squid
fi

# don't raise an error if the config file is incomplete
# set defaults instead:
SQUID_OPTS=${SQUID_OPTS:-"-D"}
SQUID_PIDFILE_TIMEOUT=${SQUID_PIDFILE_TIMEOUT:-20}
SQUID_SHUTDOWN_TIMEOUT=${SQUID_SHUTDOWN_TIMEOUT:-100}

# determine the name of the squid binary
[ -f /usr/local/sbin/squid ] && SQUID=/usr/local/sbin/squid && SQUID1=squid
[ -z "$SQUID" ] && exit 0

prog="$SQUID"

# determine which one is the cache_swap directory
CACHE_SWAP=`sed -e 's/#.*//g' /etc/squid/squid.conf | \
grep cache_dir | awk '{ print $3 }'`
[ -z "$CACHE_SWAP" ] && CACHE_SWAP=/usr/local/var/squid/cache

RETVAL=0

start() {
for adir in $CACHE_SWAP; do
if [ ! -d $adir/00 ]; then
echo -n "init_cache_dir $adir... "
$SQUID -z -F -D >> /usr/local/var/squid/logs/squid.out 2>&1
fi
done
echo -n $"Starting $prog: "
$SQUID $SQUID_OPTS >> /usr/local/var/squid/logs/squid.out 2>&1
RETVAL=$?
if [ $RETVAL -eq 0 ]; then
timeout=0;
while :; do
[ ! -f /usr/local/var/squid/logs/squid.pid ] || break
if [ $timeout -ge $SQUID_PIDFILE_TIMEOUT ]; then
RETVAL=1
break
fi
sleep 1 && echo -n "."
timeout=$((timeout+1))
done
fi
[ $RETVAL -eq 0 ] && touch /var/lock/subsys/$SQUID1
[ $RETVAL -eq 0 ] && echo_success
[ $RETVAL -ne 0 ] && echo_failure
echo
return $RETVAL
}

stop() {
echo -n $"Stopping $prog: "
$SQUID -k check >> /usr/local/var/squid/logs/squid.out 2>&1
RETVAL=$?
if [ $RETVAL -eq 0 ]; then
$SQUID -k shutdown &
rm -f /var/lock/subsys/$SQUID1
timeout=0
while :; do
[ -f /usr/local/var/squid/logs/squid.pid ] || break
if [ $timeout -ge $SQUID_SHUTDOWN_TIMEOUT ]; then
echo
return 1
fi
sleep 2 && echo -n "."
timeout=$((timeout+2))
done
echo_success
echo
else
echo_failure
echo
fi
return $RETVAL
}

reload() {
$SQUID $SQUID_OPTS -k reconfigure
}

restart() {
stop
start
}

condrestart() {
[ -e /var/lock/subsys/squid ] && restart || :
}

rhstatus() {
status $SQUID && $SQUID -k check
}

probe() {
return 0
}

case "$1" in
start)
start
;;

stop)
stop
;;

reload)
reload
;;

restart)
restart
;;

condrestart)
condrestart
;;

status)
rhstatus
;;

probe)
exit 0
;;

*)
echo $"Usage: $0 {start|stop|status|reload|restart|condrestart}"
exit 1
esac

exit $?

A PREROUTING -p tcp -m tcp -i eth1 --dport 80 -j REDIRECT --to-ports 3128

as root:
chkconfig --add squid
chkconfig --level 345 squid on

as root:
service squid start