A few months ago the netbase package started to install the /etc/sysctl.d/bindv6only.conf file to switch the default bindv6only value from 0 to 1.

A lot of people are not happy with this change, but it is not my goal to give my opinion here. On the other hand, people have propagated the rumour that it has been done as the FreeBSD kernel, used in the kfreebsd-amd64 and kfreebsd-i386 ports of Debian, only supports the mode corresponding to 1.

Let's give the truth:

• GNU/kFreeBSD people haven't been contacted about this decision;
• The FreeBSD kernel can support both modes through the net.inet6.ip6.v6only sysctl. However contrary to the Linux kernel it defaults to 1;
• This option is available in the FreeBSD kernel since 2001, and in the Linux kernel since 2003.