realhostname.c revision 50476
1/*-
2 * Copyright (c) 1999 Brian Somers <brian@Awfulhak.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD: head/lib/libutil/realhostname.c 50476 1999-08-28 00:22:10Z peter $
27 */
28
29#include <sys/param.h>
30
31#include <sys/socket.h>
32#include <netdb.h>
33#include <netinet/in.h>
34#include <arpa/inet.h>
35
36#include <stdio.h>
37#include <string.h>
38
39#include "libutil.h"
40
41int
42realhostname(char *host, size_t hsize, const struct in_addr *ip)
43{
44	int result;
45	struct hostent *hp;
46
47	result = HOSTNAME_INVALIDADDR;
48	hp = gethostbyaddr((char *)ip, sizeof(*ip), AF_INET);
49
50	if (hp != NULL && strlen(hp->h_name) <= hsize) {
51		char lookup[MAXHOSTNAMELEN];
52
53		strncpy(lookup, hp->h_name, sizeof(lookup) - 1);
54		lookup[sizeof(lookup) - 1] = '\0';
55		hp = gethostbyname(lookup);
56		if (hp == NULL)
57			result = HOSTNAME_INVALIDNAME;
58		else for (; ; hp->h_addr_list++) {
59			if (hp->h_addr_list[0] == NULL) {
60				result = HOSTNAME_INCORRECTNAME;
61				break;
62			}
63			if (!memcmp(*hp->h_addr_list, ip, sizeof(*ip))) {
64				strncpy(host, lookup, hsize);
65				return HOSTNAME_FOUND;
66			}
67		}
68	}
69
70	strncpy(host, inet_ntoa(*ip), hsize);
71
72	return result;
73}
74