How to prefere ipv4 when using 6in4?

Hello,
I’m using 6in4 tunnel as described here: https://www.turris.cz/doc/cs/howto/ipv6tunnel
Is there any way to prefere IPv4 over IPv6?
I was trying to create /etc/gai.conf with content
label ::1/128 0
label ::/0 1
label 2002::/16 2
label ::/96 3
label ::ffff:0:0/96 4
precedence ::1/128 50
precedence ::/0 40
precedence 2002::/16 30
precedence ::/96 20
precedence ::ffff:0:0/96 100
but it does not helped.
How can I find out, if is gai.conf used by clibc?