From: "Theo de Raadt" <deraadt@openbsd.org>
Subject: Re: netstat(1): get rid of inet_aton
To: tech@openbsd.org
Date: Mon, 12 Aug 2024 09:21:22 -0600

Florian Obser <florian@openbsd.org> wrote:

> On 2024-08-12 00:07 +02, Kirill A. Korinsky <kirill@korins.ky> wrote:
> >
> > The current code handles the case where localhost is 127.0.0.2 and
> > /etc/hosts has relevant records.
> 
> not since rev 1.60 of lib/libc/asr/getaddrinfo_async.c
> 
> >
> > As far as I can see in RFC 1122 and 6890, any address from 127.0.0.0/8 can
> > be used as a loopback.
> >
> > Am I missing the place where 127.0.0.1 is required to be the only possible
> > localhost address?
> >
> 
> The commit message quotes this:
> 
>     RFC 6761, 6.3 Domain Name Reservation Considerations for "localhost.":
>        3.  Name resolution APIs and libraries SHOULD recognize localhost
>            names as special and SHOULD always return the IP loopback address
>            for address queries and negative responses for all other query
>            types.  Name resolution APIs SHOULD NOT send queries for
>            localhost names to their configured caching DNS server(s).
> 
> Now, you could hagle a bit what "the IP loopback address" actually
> means. On OpenBSD it means 127.0.0.1 for IPv4 and ::1 for IPv6.

There's nothing to haggle about, because getaddrinfo_async.c hard-codes
127.0.0.1.

It does not open a socket and ioctl to see what "lo0" is configured for.