In case you didn’t know, there’s a work in progress for IPv6 support in Squid-2.6. You’ll find a patch here which, reportedly, is being used in production at a few sites.
If you’d like to see IPv6 in a future Squid-2 release – its a very large change to introduce in the squid-2.6 release so it would appear in a 2.7 or 2.8 release – then please join the squid-users mailing list and let us know.
(I hear a lot of people complaining about how Squid doesn’t “support IPv6” and yet won’t try Squid-3+IPv6 or even try googling for alternatives. The truth is that there’s been unofficial patches to Squid-2 to support IPv6 in some fashion for a number of years now – heck, there was an IPv6 patch to Squid-1! – but noone volunteered to stand up, tidy it up and get it in shape for inclusion into the main tree. If IPv6 is important to you then please say so; please test the stuff thats out there and don’t hesitate to donate to the Squid project with a note saying “for IPv6!”.)