SNATing connections of a transparent proxy to their original IPs

["Vicentiu Rizan" <vici@xxxxxxxxxx>]

This question has probably been asked before but I can't find anything 
relevant.
I'm looking for a way to SNAT the connections that a transparent squid cache 
makes back to their original IPs.

client(IP: a.b.c.d)->squid machine(a.b.c.e)->site server(w.x.y.z) (I want 
this server to see a.b.c.d instead of the a.b.c.e IP)

Is there a plugin for squid that can work with netfilter to do this? (kernel 
2.6)

Thanks