Comment 8 for bug 370542

@Andreas: When troubleshooting Ubuntu, please do not "think so", please test instead :)

All my Intrepid Desktop VMs have "::1 ip6-localhost ip6-loopback", and all my Jaunty VMs have "::1 localhost ip6-localhost ip6-loopback" in /etc/hosts.

Further, both on Intrepid and on Jaunty, Apache2 *does* listen on IPv6 addresses by default, as a quick

  sudo netstat -ntlp |grep ::80

will show. Again: please do not "take it", please test instead :)

As a further test, I just now:

(1) Created two new VMs, one booted/installed from a ubuntu-8.10-desktop-i386.iso image and one from a ubuntu-9.04-desktop-i386.iso image. Other than their hostnames (itest and jtest respectively) I was careful to perform the installs in exactly the same way. Result: itest has "::1 ip6-localhost ip6-loopback", and jtest has "::1 localhost ip6-localhost ip6-loopback" in /etc/hosts. I conclude that this *is* in fact something that changed in Jaunty.

(2) I then installed apache2 (sudo apt-get install apache2 --no-install-recommends) on each VM and restarted it.
At this point both VMs can browse to http://localhost/ and also http://[::1]/ successsfully.

(3) I then edited /etc/apache2/sites-available/default on both machines, editing only the line 13 from "allow from all" into "allow from localhost", and then rebooted both VMs. At this point the Intrepid machine can still browse localhost, but the Jaunty machine cannot. At this point both machines can browse http://127.0.0.1, and neither machine can browse http://[::1]/ .

(4) On jtest (the Jaunty machine), I then edited /etc/apache2/sites-available/default to add an additional line "allow from ::1" just after the "allow from localhost" line, and rebooted. Now http://localhost and http://[::1] are both browseable on this machine.

I trust this is sufficient testing to support my earlier diagnosis of this issue. I can provide tcpdump packet captures to demonstrate that in Jaunty, browsing http://localhost is generating IPv6 traffic, but in Intrepid browsing http://localhost uses IPv4, if we really need to do that to demonstrate that this really is the difference here :)

Jonathan