Eliminating IPv6 (?)

[Eugene Grosbein]

19.06.2019 22:42, Rodney W. Grimes wrote:

>> 18.06.2019 10:10, Ronald F. Guilmette wrote:
>>> How can I turn off IPv6 entirely without rebuilding the kernel?
>> You cannot. GENERIC kernel specifically enables IPv6 support and you need to disable it at compile time.
>> And if you do, you better rebuild the world too using WITHOUT_INET6=yes in the /etc/src.conf
>> or else some utilities compiled with INET6 by default will query kernel
>> for IPv6-specific data (like routing entries) and complain that your kernel does not know about it.
> I have not seen these issues, can you give a specific example that fails?

Other than kernel/userland interaction (that may be not relevant anymore for modern FreeBSD),
that's basically about making network connections (such as telnet etc.)
to FQDNs resolved to IPv6 addresses supported by binaries (and resolver being userland beast)
but not kernel/routing table.

> A netstat -rn on a v4 only kernel simple reports the v4 table, and iirc a
> netstat -rn6 returns a "Protocol not supported error" as should all other
> things.
>> World built WITHOUT_INET6 has no such rough edges.
> I find that actually causes me more issues, as then my
> netstat -rn6 returns a hard error due to:
>                 case '6':
> #ifdef INET6
>                         af = AF_INET6;
> #else
>                         errx(1, "IPv6 support is not compiled in");
> #endif

Seems very logical to me. Do we have a script in base running "netstat -rn6"
and breaking on this?