Re: Broken IPv6 / IPv4 configuration, or Gmail brokenness?
Hi,
On Sun, Jan 22, 2023 at 11:42:18PM -0500, Celejar wrote:
> Shouldn't this be included somewhere prominently in the Debian
> documentation, in the form of a Big Fat Warning that the standard
> dual-stack condiguration used by Debian can cause serious breakage if
> one's ISP doesn't support IPv6?
Not having IPv6 is not the problem. As you discovered later in this
thread, your ISP is providing just enough IPv6 for your router to
think it has a v6 block to hand out, but not enough that it actually
works. It's a misconfiguration by your ISP and not something that
any operating system's documentation needs to point out. They could
also let you connect to them but make IPv4 not work, it's just that
you'd notice that very quickly!
If you don't have a global scope IPv6 address on any interface then
at the point where your system is trying to decide what source
address to use for some packets, it will not that any IPv6 source
address to use. If there are IPv4 addresses to talk to then it will
source from one of your IPv4 addresses, or else give an error.
The change suggested here to gai.conf says to try IPv4 first, which
is why it fixes things for you.
I'm not sure but I think you may still have a bad time in the event
that a DNS response included ONLY IPv6 addresses, because the need
for a v6 source address would bypass gai.conf settings and then
instead of getting an instant failure you'd again get the long
timeout while your non-working IPv6 was used. But that is obviously
an edge case here.
Anyway, if the ISP can't fix the IPv6 and can't be convinced to stop
advertising it even when it doesn't work, I think you'd be best
off trying to disable radvd on the router. Failing that, disabling
IPv6 on all your clients (check your phones too, as they will try
IPv6 these days if they think it's available).
Cheers,
Andy
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https://bitfolk.com/ -- No-nonsense VPS hosting
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