On Thu, Sep 03, 2015 at 04:14:32PM +0000, Alan Cronin (alcronin) wrote:
> We will want to use IPv6 in the product but we have a US federal
> requirement (DoD UCR available online) to provide a happy eyeballs
> solution where preference is given to IPv4 addresses rather than IPv6.
> This will be provided via configuration in the application.
>
Happy eyeball is more than a preference. It's about speculative TCP connect to
all IP addresses and using the first connected TCP stream for session data.

If you are only after the preference and your product is whole operating
system, you could tune the system DNS resolver instead of each application.
For example, Linux systems with glibc have /etc/gai.conf for that purpose.

-- Petr

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