Enabling IPv6 support for IPv4-only apps on Linux

Re:Enabling IPv6 support for IPv4-only apps on Linux by hot_gril on Thursday October 05, 2023 @06:26PM (#37785047)

It's valid but not routable in practice. The Internet collectively didn't choose to map existing IPv4 addresses into v6 or keep the routing unified, that's the problem. It should've been that 1.1.1.1 on v4 now owns 1.1.1.1/32 on v6, so going all-v6 doesn't mean cutting yourself off from v4 hosts. Once v6 was well-adopted, they could start using the longer addresses. Instead, we got two totally separate networks.

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Re:Enabling IPv6 support for IPv4-only apps on Linux by Macha on Thursday October 05, 2023 @06:38PM (#37785144)

This is an "IPv6" network that does not allow for more users. The IPv4 network space is already depleted. This is why mobile ISPs, Indian ISPs etc. are all dual stack with CGNAT for IPv4.

Perhaps you meant to suggest that they should own 1.1.1.1::/64 or 1.1.1.1/128?

Even if it's the latter case, both the actual ::ffff:1.2.3.4 (or it's predecessor ::1.2.3.4) have the problem that some middle box receives a packet for 1.1.1.1::abcd:1234, doesn't understand the header the abcd:1234 portion is encoded in, throws it away, and the router at 1.1.1.1 receives a packet which is destined for some unknown device behind the router with no info for how to get the packet to that device.

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Re:Enabling IPv6 support for IPv4-only apps on Linux by hot_gril on Thursday October 05, 2023 @06:55PM (#37785267)

Yes, it wouldn't allow more users, which would've been fine back then. They'd focus on getting everyone onto the v6 protocol first, then open up the new addresses for use. That's the transition period that never happened.

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Re:Enabling IPv6 support for IPv4-only apps on Linux by Macha on Thursday October 05, 2023 @07:31PM (#37785547)

The only motivation for the ISPs etc., who you need to get onboard, is to get more users. This is why IPv6 adoption has been soaring in the last 3-4 years when there's large new use cases that cannot economically get addresses in the volume they would require and didn't happen when IPv4 addresses were more freely available.

The only other way to get them to invest in alternatives to IPv4 before IPv4 stopped meeting their business needs would have been via regulation.

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Re:Enabling IPv6 support for IPv4-only apps on Linux by p1mrx on Thursday October 05, 2023 @10:36PM (#37786613)

You are describing 6to4, where 1.1.1.1 owns 2002:101:101::/48.

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Re:Enabling IPv6 support for IPv4-only apps on Linux by Dagger2 on Friday October 06, 2023 @05:53AM (#37788802)

We did map existing v4 addresses into v6. They're not two totally separate networks at all.

But the limitations of v4 and of existing v4 devices limit the ways that can work. Reinventing stuff and calling it "4.1" won't change that. You'll still face all of the same limitations.

> They'd focus on getting everyone onto the v6 protocol first, then open up the new addresses for use. That's the transition period that never happened.

That's basically the transition period that _is_ happening, except we aren't delaying the "open up the new addresses" stage -- the new addresses are usable straight away for anything you've migrated.

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