realhostname.c revision 183989 
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
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: head/lib/libutil/realhostname.c 183989 2008-10-17 21:21:14Z delphij $");
29
30#include <sys/param.h>
31#include <sys/socket.h>
32
33#include <netdb.h>
34#include <netinet/in.h>
35#include <arpa/inet.h>
36
37#include <stdio.h>
38#include <string.h>
39
40#include "libutil.h"
41
42struct sockinet {
43	u_char	si_len;
44	u_char	si_family;
45	u_short	si_port;
46};
47
48int
49realhostname(char *host, size_t hsize, const struct in_addr *ip)
50{
51	char trimmed[MAXHOSTNAMELEN];
52	int result;
53	struct hostent *hp;
54
55	result = HOSTNAME_INVALIDADDR;
56	hp = gethostbyaddr((const char *)ip, sizeof(*ip), AF_INET);
57
58	if (hp != NULL) {
59		strlcpy(trimmed, hp->h_name, sizeof(trimmed));
60		trimdomain(trimmed, strlen(trimmed));
61		if (strlen(trimmed) <= hsize) {
62			char lookup[MAXHOSTNAMELEN];
63
64			strlcpy(lookup, hp->h_name, sizeof(lookup));
65			hp = gethostbyname(lookup);
66			if (hp == NULL)
67				result = HOSTNAME_INVALIDNAME;
68			else for (; ; hp->h_addr_list++) {
69				if (*hp->h_addr_list == NULL) {
70					result = HOSTNAME_INCORRECTNAME;
71					break;
72				}
73				if (!memcmp(*hp->h_addr_list, ip, sizeof(*ip))) {
74					strncpy(host, trimmed, hsize);
75					return HOSTNAME_FOUND;
76				}
77			}
78		}
79	}
80
81	strncpy(host, inet_ntoa(*ip), hsize);
82
83	return result;
84}
85
86int
87realhostname_sa(char *host, size_t hsize, struct sockaddr *addr, int addrlen)
88{
89	int result, error;
90	char buf[NI_MAXHOST];
91	struct sockaddr_in lsin;
92
93	result = HOSTNAME_INVALIDADDR;
94
95#ifdef INET6
96	/* IPv4 mapped IPv6 addr consideraton, specified in rfc2373. */
97	if (addr->sa_family == AF_INET6 &&
98	    addrlen == sizeof(struct sockaddr_in6) &&
99	    IN6_IS_ADDR_V4MAPPED(&((struct sockaddr_in6 *)addr)->sin6_addr)) {
100		struct sockaddr_in6 *sin6;
101
102		sin6 = (struct sockaddr_in6 *)addr;
103
104		memset(&lsin, 0, sizeof(lsin));
105		lsin.sin_len = sizeof(struct sockaddr_in);
106		lsin.sin_family = AF_INET;
107		lsin.sin_port = sin6->sin6_port;
108		memcpy(&lsin.sin_addr, &sin6->sin6_addr.s6_addr[12],
109		       sizeof(struct in_addr));
110		addr = (struct sockaddr *)&lsin;
111		addrlen = lsin.sin_len;
112	}
113#endif
114
115	error = getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
116			    NI_NAMEREQD);
117	if (error == 0) {
118		struct addrinfo hints, *res, *ores;
119		struct sockaddr *sa;
120
121		memset(&hints, 0, sizeof(struct addrinfo));
122		hints.ai_family = addr->sa_family;
123		hints.ai_flags = AI_CANONNAME | AI_PASSIVE;
124		hints.ai_socktype = SOCK_STREAM;
125
126		error = getaddrinfo(buf, NULL, &hints, &res);
127		if (error) {
128			result = HOSTNAME_INVALIDNAME;
129			goto numeric;
130		}
131		for (ores = res; ; res = res->ai_next) {
132			if (res == NULL) {
133				freeaddrinfo(ores);
134				result = HOSTNAME_INCORRECTNAME;
135				goto numeric;
136			}
137			sa = res->ai_addr;
138			if (sa == NULL) {
139				freeaddrinfo(ores);
140				result = HOSTNAME_INCORRECTNAME;
141				goto numeric;
142			}
143			if (sa->sa_len == addrlen &&
144			    sa->sa_family == addr->sa_family) {
145				((struct sockinet *)sa)->si_port = ((struct sockinet *)addr)->si_port;
146#ifdef INET6
147				/*
148				 * XXX: sin6_socpe_id may not been
149				 * filled by DNS
150				 */
151				if (sa->sa_family == AF_INET6 &&
152				    ((struct sockaddr_in6 *)sa)->sin6_scope_id == 0)
153					((struct sockaddr_in6 *)sa)->sin6_scope_id = ((struct sockaddr_in6 *)addr)->sin6_scope_id;
154#endif
155				if (!memcmp(sa, addr, sa->sa_len)) {
156					result = HOSTNAME_FOUND;
157					if (ores->ai_canonname == NULL) {
158						freeaddrinfo(ores);
159						goto numeric;
160					}
161					strlcpy(buf, ores->ai_canonname,
162						sizeof(buf));
163					trimdomain(buf, hsize);
164					if (strlen(buf) > hsize &&
165					    addr->sa_family == AF_INET) {
166						freeaddrinfo(ores);
167						goto numeric;
168					}
169					strncpy(host, buf, hsize);
170					break;
171				}
172			}
173		}
174		freeaddrinfo(ores);
175	} else {
176    numeric:
177		if (getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0,
178				NI_NUMERICHOST) == 0)
179			strncpy(host, buf, hsize);
180	}
181
182	return result;
183}
184
185
186