Petr Menšík wrote: > Hello everyone, > > I have attended recently csnog.eu conference [1], where some interesting > presentations took place. They were usually in Czech, so it is not > something I am going to share more. But what took my interest were ipv6 > readiness with some exceptions. Fedora is ready to be run on dual-stack > IPv4 and IPv6 networks just fine. But the presentation were about future > case where we run most hosts on IPv6 network only, but allow some older > devices to take and use also IPv4 address. > > Fortunately there is roughly the same presentation[2] in English, which > took the place on RIPE 85 meeting. What catched my interest were talk > about Windows 11 and Apple systems are ready, but not really talk about > how any linux distribution is ready for such situation. It seems to me > we should improve the support for mentioned mechanisms in Fedora.
Having watched the latter presentation, I understand that the idea is that, on a network with a limited pool of globally routable IPv4 addresses, IPv6-capable clients should use only IPv6 and refrain from requesting IPv4 addresses, so that addresses will be available to legacy devices that need IPv4. It seems to me that it would be very difficult for a DHCP client program to know whether the Fedora installation it's running on needs an IPv4 address. I think it would have to be manually configured. It's mentioned in the presentation that IPv6 support is required in Apple's App Store. That's not currently the case in Fedora. In my own opinion everything should by now assume IPv6 as the norm, and treat IPv4 as the legacy protocol that must still be supported for compatibility – but that's not Fedora's policy. The policy is as follows: | If an application contains native and stable support for both IPv4 and | IPv6, and support for IPv6 does not negatively affect IPv4 then both | MUST be enabled in the Fedora package. https://docs.fedoraproject.org/en-US/packaging-guidelines/#_networking_support That means that IPv4-only programs are still quite welcome in Fedora if their lack of IPv6 support is an upstream limitation and not introduced by the packager. Thus the network configuration must expect that the user might run such a program and might need IPv4 connectivity. The policy should probably be changed before Fedora begins requesting only IPv6 addresses by default. Another concern is that the entire IPv6-mostly concept seems to assume devices that are strictly clients. It doesn't seem like it would work for anyone who runs any kind of server or peer-to-peer program. The idea seems to be that IPv6 clients will access IPv4-only servers over NAT64. Like all address translation, NAT64 is an obstacle to peer-to-peer communication. If you need to communicate with a peer who is stuck with an RFC 1918 address behind NAT on an IPv4-only network – a case that is still far too common – and you're using IPv6 and NAT64, then you and your peer will both be unable to connect to each other. If globally routable IPv4 addresses are available on the network where you are, then you'll want one so that your peer can at least connect to you. Users of peer-to-peer programs will want to configure their DHCP client to request an IPv4 address in case that need arises. Björn Persson
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