[CentOS] Transparent proxy with LVS

Tue Apr 27 18:22:20 UTC 2010
Enrique Verdes <EVerdes at conatel.com.uy>

I've managed to configure a LVS Cluster to act as a transparent proxy
squid farm, with a virtual server as load balancer, and three real
servers. Because redirecting packets going to port 80 to port 3128 of
squid in the load balancer doesn't works, the solution has a mix of ip
route and iptables.

Here is the script I wrote to configure transparent proxy.

#Transparent proxy configuration

#Packet marking
iptables -t mangle -F
iptables -t mangle -A PREROUTING -p tcp --dport $WEB --dst ! $VIP -j
MARK --set-mark 2

#Routing table creation
if [ $(grep -sq 'www\.out' /etc/iproute2/rt_tables) ]; then
	echo "Table exists"
	echo "202 www.out" >> /etc/iproute2/rt_tables

#Clean tables and rules
ip rule del prio 100 fwmark 2 table www.out
ip route flush table www.out

#Routing of marked packets
ip rule add prio 100 fwmark 2 table www.out
ip route add table www.out to local 0/0 dev lo
ip route flush cache

#ipvsadm rules
ipvsadm -A --fwmark-service 2
ipvsadm -a --fwmark-service 2 --real-server $SRV01 --gatewaying
ipvsadm -a --fwmark-service 2 --real-server $SRV02 --gatewaying
ipvsadm -a --fwmark-service 2 --real-server $SRV03 --gatewaying

As you can see, I mark all packets not directed to the virtual server
itself, to port 80 with 2, and then route all those marked packets to
the loopback interface.

With ipvsadm I forward the marked packets to the real servers. In the
real servers there's a rule in the prerouting chain to redirect those
packets to port 3128

I'm using pulse service to start lvs, and would like to add the ipvsadm
rules to the /etc/sysconfig/ha/lvs.cf, so they are issued by pulse at
startup. I can't figure out how to do it. When I try to start pulse, it
fails because i left the address field empty. But this service is not
tied to any address, I just want the fwmark match to forward the packets
to the real servers. I also have dns in this lvs cluster. 

Any suggestion about how I can add my ipvsad rules to the lvs.cf file?
Enrique Verdes <EVerdes at conatel.com.uy>
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