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      1 /*	$NetBSD: localhostname.c,v 1.9 2008/04/28 20:24:18 martin 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  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #ifndef lint
     34 __RCSID("$NetBSD: localhostname.c,v 1.9 2008/04/28 20:24:18 martin Exp $");
     35 #endif
     36 
     37 #include <sys/param.h>
     38 #include <sys/socket.h>
     39 
     40 #include <err.h>
     41 #include <netdb.h>
     42 #include <stdio.h>
     43 #include <string.h>
     44 #include <unistd.h>
     45 
     46 #include "protos.h"
     47 
     48 void
     49 localhostname(char *buf, size_t buflen)
     50 {
     51 	struct addrinfo *res, hints;
     52 	char hostname[MAXHOSTNAMELEN + 1];
     53 	int error;
     54 
     55 	if (gethostname(hostname, sizeof(hostname)))
     56 		err(1, "gethostname");
     57 	hostname[sizeof(hostname) - 1] = '\0';
     58 
     59 	memset(buf, 0, buflen);
     60 
     61 	/*
     62 	 * If hostname appears to be fully-qualified,
     63 	 * just return it.
     64 	 */
     65 	if (strchr(hostname, '.')) {
     66 		strlcpy(buf, hostname, buflen);
     67 		return;
     68 	}
     69 
     70 	/*
     71 	 * Lookup the host.  Return the canonical name.
     72 	 */
     73 	memset(&hints, 0, sizeof(hints));
     74 	hints.ai_flags = AI_CANONNAME;
     75 	hints.ai_family = PF_UNSPEC;
     76 
     77 	error = getaddrinfo(hostname, NULL, &hints, &res);
     78 	if (error)
     79 		errx(1, "getaddrinfo(%s) failed: %s", hostname,
     80 		    gai_strerror(error));
     81 	strlcpy(buf, res->ai_canonname, buflen);
     82 	freeaddrinfo(res);
     83 }
     84