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localhostname.c revision 1.8 
      1 /*	$NetBSD: localhostname.c,v 1.8 2002/07/06 21:39:25 wiz Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1996 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Jason R. Thorpe.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *        This product includes software developed by the NetBSD
     21  *        Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 #ifndef lint
     41 __RCSID("$NetBSD: localhostname.c,v 1.8 2002/07/06 21:39:25 wiz Exp $");
     42 #endif
     43 
     44 #include <sys/param.h>
     45 #include <sys/socket.h>
     46 
     47 #include <err.h>
     48 #include <netdb.h>
     49 #include <stdio.h>
     50 #include <string.h>
     51 #include <unistd.h>
     52 
     53 #include "protos.h"
     54 
     55 void
     56 localhostname(char *buf, size_t buflen)
     57 {
     58 	struct addrinfo *res, hints;
     59 	char hostname[MAXHOSTNAMELEN + 1];
     60 	int error;
     61 
     62 	if (gethostname(hostname, sizeof(hostname)))
     63 		err(1, "gethostname");
     64 	hostname[sizeof(hostname) - 1] = '\0';
     65 
     66 	memset(buf, 0, buflen);
     67 
     68 	/*
     69 	 * If hostname appears to be fully-qualified,
     70 	 * just return it.
     71 	 */
     72 	if (strchr(hostname, '.')) {
     73 		strlcpy(buf, hostname, buflen);
     74 		return;
     75 	}
     76 
     77 	/*
     78 	 * Lookup the host.  Return the canonical name.
     79 	 */
     80 	memset(&hints, 0, sizeof(hints));
     81 	hints.ai_flags = AI_CANONNAME;
     82 	hints.ai_family = PF_UNSPEC;
     83 
     84 	error = getaddrinfo(hostname, NULL, &hints, &res);
     85 	if (error)
     86 		errx(1, "getaddrinfo(%s) failed: %s", hostname,
     87 		    gai_strerror(error));
     88 	strlcpy(buf, res->ai_canonname, buflen);
     89 	freeaddrinfo(res);
     90 }
     91