Date: Sun, 28 Sep 1997 11:26:12 +0200 From: sthaug@nethelp.no To: tlambert@primenet.com Cc: freebsd-hackers@freefall.FreeBSD.org Subject: Re: r-cmds and DNS and /etc/host.conf Message-ID: <22414.875438772@verdi.nethelp.no> In-Reply-To: Your message of "Sat, 27 Sep 1997 21:29:41 %2B0000 (GMT)" References: <199709272129.OAA11592@usr08.primenet.com>
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> Technically 127.1 and 127.0.0.1 are synonymous; one would think the
> code should know this...
Technically, 127.0.0.1 for the loopback address is a Berkeley-ism, but
it is now cast in stone, since RFC1700 defines
(g) {127, <any>}
Internal host loopback address. Should never appear outside
a host.
As far as I can see, this change occurred in two steps:
- RFC 820 (January 1983 "Assigned Numbers") doesn't mention 127.*.*.*.
- RFC 870 (October 1983 "Assigned Numbers") has 127.*.*.* as "reserved".
- RFC 990 (November 1986 "Assigned Numbers") has 127.*.*.* explicitly
as loopback.
127.1 as an alternative way of writing 127.0.0.1 is also a Berkeley-ism,
as far as I know. The name server (BIND) knows nothing about it, and the
inet_pton() routine (part of POSIX 1003.1g work in progress) does not
recognize this format, even if inet_addr() and inet_ntoa() does. It is
*not* a particularly good idea to depend on 127.1 being interpreted as
127.0.0.1.
Steinar Haug, Nethelp consulting, sthaug@nethelp.no
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