Re: CVS commit: src/lib/libc/net

[Havard Eidnes <he%NetBSD.org@localhost>]

>   | So, what did we do by default: allow "_" in hostnames when that's
>   | explicitly against standard, or not?
>
> Which standard?

952, referred to from 1123.

> There's RFC952 that specifies the format of HOSTS.TXT (from 1985).
> (The update in Hosts Requirements isn't material, one way or the other, here.)
>
> What else?   In fact, aside from being listed in HOSTS.TXT, what exactly
> is a hostname?   Is it defined somewhere?

I beleive that in the context of the DNS, the customary
definition of a hostname is a DNS name which has either an A or a
AAAA record registered on it.  If I'm not much mistaken, that's
the interpretation implemented by BIND's "check-names" feature:
when turned on, it allows underscores in DNS names as long as
those names don't have A or AAAA information registered on them,
but either complains or errs depending on the value of the option
in BINDs configuration.

> But library functions, like the resolver library, and getaddrinfo(),
> and the older variants, have no idea why the DNS is being consulted, they
> don't know, generally, what rules are intended to apply - they cannot
> possibly legitimately object to anything (getaddrinfo() when given a port
> as well might guess what rules might apply, but even then it cannot know
> for sure .. the name it is being looked up, if the port is "http" (or 80)
> or "https" (or 443) then the name being looked up might be the hostname
> from a URL, which has some syntax constraints, or it might be the name
> configured as the local proxy server, which does not - it is just a key to
> use to extract an address from the DNS.)
>
> There is no rational way that those functions can ever validate name
> syntax, and get it correct.

I'm not entirely certain I agree.  If you're looking up A or AAAA
information, you're looking up a host name, and some syntactical
restrictions may apply (optionally turned on/off?) if you wish to
adhere to the restrictions in RFC 952.

If you're looking up other information in DNS, I agree that there
should be no restrictions on the name being looked up, ref.
section 11 in RFC 2187.

Regards,

- Håvard