realhostname.c revision 184683
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 184683 2008-11-05 12:13:10Z des $"); 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 86/* 87 * struct sockaddr has very lax alignment requirements, since all its 88 * members are char or equivalent. This is a problem when trying to 89 * dereference a struct sockaddr_in6 * that was passed in as a struct 90 * sockaddr *. Although we know (or trust) that the passed-in struct was 91 * properly aligned, the compiler doesn't, and (rightly) complains. These 92 * macros perform the cast in a way that the compiler will accept. 93 */ 94#define SOCKADDR_IN6(p) ((struct sockaddr_in6 *)(void *)(p)) 95#define SOCKADDR_IN(p) ((struct sockaddr_in *)(void *)(p)) 96#define SOCKINET(p) ((struct sockinet *)(void *)(p)) 97 98int 99realhostname_sa(char *host, size_t hsize, struct sockaddr *addr, int addrlen) 100{ 101 int result, error; 102 char buf[NI_MAXHOST]; 103 struct sockaddr_in lsin; 104 105 result = HOSTNAME_INVALIDADDR; 106 107#ifdef INET6 108 /* IPv4 mapped IPv6 addr consideraton, specified in rfc2373. */ 109 if (addr->sa_family == AF_INET6 && 110 addrlen == sizeof(struct sockaddr_in6) && 111 IN6_IS_ADDR_V4MAPPED(&SOCKADDR_IN6(addr)->sin6_addr)) { 112 struct sockaddr_in6 *sin6; 113 114 sin6 = SOCKADDR_IN6(addr); 115 116 memset(&lsin, 0, sizeof(lsin)); 117 lsin.sin_len = sizeof(struct sockaddr_in); 118 lsin.sin_family = AF_INET; 119 lsin.sin_port = sin6->sin6_port; 120 memcpy(&lsin.sin_addr, &sin6->sin6_addr.s6_addr[12], 121 sizeof(struct in_addr)); 122 addr = (struct sockaddr *)&lsin; 123 addrlen = lsin.sin_len; 124 } 125#endif 126 127 error = getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0, 128 NI_NAMEREQD); 129 if (error == 0) { 130 struct addrinfo hints, *res, *ores; 131 struct sockaddr *sa; 132 133 memset(&hints, 0, sizeof(struct addrinfo)); 134 hints.ai_family = addr->sa_family; 135 hints.ai_flags = AI_CANONNAME | AI_PASSIVE; 136 hints.ai_socktype = SOCK_STREAM; 137 138 error = getaddrinfo(buf, NULL, &hints, &res); 139 if (error) { 140 result = HOSTNAME_INVALIDNAME; 141 goto numeric; 142 } 143 for (ores = res; ; res = res->ai_next) { 144 if (res == NULL) { 145 freeaddrinfo(ores); 146 result = HOSTNAME_INCORRECTNAME; 147 goto numeric; 148 } 149 sa = res->ai_addr; 150 if (sa == NULL) { 151 freeaddrinfo(ores); 152 result = HOSTNAME_INCORRECTNAME; 153 goto numeric; 154 } 155 if (sa->sa_len == addrlen && 156 sa->sa_family == addr->sa_family) { 157 SOCKINET(sa)->si_port = SOCKINET(addr)->si_port; 158#ifdef INET6 159 /* 160 * XXX: sin6_socpe_id may not been 161 * filled by DNS 162 */ 163 if (sa->sa_family == AF_INET6 && 164 SOCKADDR_IN6(sa)->sin6_scope_id == 0) 165 SOCKADDR_IN6(sa)->sin6_scope_id = 166 SOCKADDR_IN6(addr)->sin6_scope_id; 167#endif 168 if (!memcmp(sa, addr, sa->sa_len)) { 169 result = HOSTNAME_FOUND; 170 if (ores->ai_canonname == NULL) { 171 freeaddrinfo(ores); 172 goto numeric; 173 } 174 strlcpy(buf, ores->ai_canonname, 175 sizeof(buf)); 176 trimdomain(buf, hsize); 177 if (strlen(buf) > hsize && 178 addr->sa_family == AF_INET) { 179 freeaddrinfo(ores); 180 goto numeric; 181 } 182 strncpy(host, buf, hsize); 183 break; 184 } 185 } 186 } 187 freeaddrinfo(ores); 188 } else { 189 numeric: 190 if (getnameinfo(addr, addrlen, buf, sizeof(buf), NULL, 0, 191 NI_NUMERICHOST) == 0) 192 strncpy(host, buf, hsize); 193 } 194 195 return result; 196} 197 198 199