From owner-freebsd-questions  Mon Nov 26 10:21:20 2001
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Date: Mon, 26 Nov 2001 01:07:53 -0800
From: "Crist J. Clark" <cristjc@earthlink.net>
To: John Smith <anarcat@anarcat.dyndns.org>
Cc: Simon Dick <simond@irrelevant.org>,
	Jim Conner <jconner@enterit.com>,
	FreeBSD Questions <freebsd-questions@FreeBSD.ORG>
Subject: Re: can't do reverse dns with /etc/hosts
Message-ID: <20011126010753.E222@gohan.cjclark.org>
Reply-To: cjclark@alum.mit.edu
References: <5.1.0.14.0.20011123164749.0245ec60@mail.enterit.com> <20011114173647.D66694@blossom.cjclark.org> <20011115012039.GA61093@shall.anarcat.dyndns.org> <20011114173647.D66694@blossom.cjclark.org> <5.1.0.14.0.20011123164749.0245ec60@mail.enterit.com> <5.1.0.14.0.20011123172728.02c61518@mail.enterit.com> <20011124103734.GB386@irrelevant.org> <3BFFF17E.D2E2F7C1@anarcat.dyndns.org>
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In-Reply-To: <3BFFF17E.D2E2F7C1@anarcat.dyndns.org>; from anarcat@anarcat.dyndns.org on Sat, Nov 24, 2001 at 02:14:06PM -0500
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On Sat, Nov 24, 2001 at 02:14:06PM -0500, John Smith wrote:
> 
> 
> Simon Dick wrote:
> > 
> > I guess my method of just using ping <hostname> and seeing what IP it tries
> > to ping won't be suitable for this? :)
> 
> no because I want to test reverse DNS.

That does not make any sense. You want to test reverse-DNS without
using DNS? ITYM, "I want to test address-to-hostname translation using
/etc/hosts."

I couldn't sleep so I wrote a quick program.
-- 
Crist J. Clark                           cjclark@alum.mit.edu

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/*
 * Copyright (c) 2001 Crist J. Clark
 * $Id: iplookup.c,v 1.2 2001/11/26 09:07:02 cjc Exp $
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <err.h>
#include <netdb.h>
#include <stdio.h>
#include <sysexits.h>

int main(int argc, char *argv[])
{
	struct hostent	*h;
	struct in_addr	a;
	int		i, j;

	for (i = 1; i < argc; i++) {
		if (inet_aton(argv[i], &a) == 0)
			errx(EX_USAGE, "could not parse IP address: %s",
			    argv[i]);

		if ((h = gethostbyaddr((char *)&a, sizeof a, AF_INET)) == NULL)
			errx(EX_OSERR, "address, %s, failed: %s",
			    argv[i], hstrerror(h_errno));

		printf("%s\n", h->h_name);

		for (j = 0; h->h_aliases[j] != NULL; j++)
			printf("\t%s\n", h->h_aliases[j]);
	}

	return 0;
}

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