Re: MPro fails with IPv6-only servers (interaction with local DNS resolution)

Darren Salt <listspam@...> wrote:

> This creates an interesting situation: MPro does the DNS lookup and is
> told 192.0.2.1 and 2A00:801:103:10::35. It tries to connect via IPv4, gets
> an ICMPv4 “admin prohibited” error from my router/firewall and doesn't
> bother to try via IPv6. I've also tested with “network unreachable” and
> without a local rule to trap this (in which case my ISP does so instead)
> with the same result.

It appears that this is due to a very old workaround to prevent Qt from
doing its own DNS lookups (IIRC because Qt 3 didn't use the system resolvers
and made queries direct to the configured name servers which triggered
warnings in various Windows firewall products). The workaround was for MPro
to use the system resolver and always pass an IP address to Qt, but this
code never got updated to be IPv6 aware.

I'm now testing a version of MPro that once again uses Qt for name
resolution as I believe it now does this differently. As Qt is claimed to be
IPv6 aware, this should hopefully mean MPro is too. As a side effect, MPro
will lose its internal DNS cache, but as this wasn't particularly
intelligent, this likely fixes some other obscure issues.

-- 
Mark Sawle                                                www.intellegit.com
Intellegit Ltd.
Developers of Messenger Pro: multi-platform mail, news and calendar software

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