On Thu Oct 29 15:15:10 UTC 2015, Pavel Simerda wrote:
I am writing to Fedora development mailing lists to get opinions
and ideas regarding our project on improving IPv6 support in
Fedora across its components.

https://fedoraproject.org/wiki/QA/Networking

Most prominent subpages:

 * https://fedoraproject.org/wiki/QA/Networking/Test_environment
 * https://fedoraproject.org/wiki/QA/Networking/Client_software
 * https://fedoraproject.org/wiki/QA/Networking/Server_software

During the first phase we are interested in getting feedback on
testing methods and test cases. Any other ideas are of course
welcome. Even contacts for future collaboration would be great.

I was an early adopter of IPv6; I've had it in some form or another continuously since 2006. I may have a few ideas to share.

My late response today was motivated in part by my attempting to install Fedora in a VM from my private IPv6-only Fedora mirror, and having it completely fail to download .treeinfo and squashfs.img, despite picking up an SLAAC IPv6 address and being bridged to the same subnet as the mirror...

One of the REALLY early adopters of IPv6 was Microsoft, who began rolling it out internally in the early 2000s, when XP was the new OS on the block. I recently read a Microsoft book, Understanding IPv6 (Third Edition) and one of the things I took away from that, with regard to testing, is that since Vista/2008 they do not test Windows without the IPv6 stack, nor can it even be fully removed! But you can uninstall the IPv4 stack from Windows, and this is a fully supported configuration.

A short bit from the book:

> From Microsoft's perspective, IPv6 is a mandatory part of the Windows operating system, and it is enabled and included in standard Windows service and application testing during the operating system development process. Because Windows was designed specifically with IPv6 present, Microsoft does not perform any testing to determine the effects of disabling IPv6. If IPv6 is disabled in Windows, some components will not function. Moreover, applications that you might not think are using IPv6—such as Remote Assistance, HomeGroup, DirectAccess, and Windows Mail—could be.

I'm aware that there remain kernel issues preventing IPv4 from being entirely disabled, but it should be possible today to test Fedora in an (almost) entirely IPv6-only configuration. Such a setup could shake loose a very large pile of bugs (on the order of thousands, across all Fedora packages). One interesting test in particular would be to remove 127.0.0.1 from the lo interface, leaving only ::1; there is a lot of software out there that assumes that 127.0.0.1 will always be there, and this is not a valid assumption.

For some background on things that can be expected to go wrong in an IPv6-only network, RFC 6586 makes good reading.

OK, maybe I just had one idea...

(Note that I'm on digest and usually only skim it, so I might miss any messages not CC'd to me.)