resolve.c   [plain text]

/*
 * test/resolve/resolve.c
 *
 * Copyright 1995 by the Massachusetts Institute of Technology.
 * All Rights Reserved.
 *
 * Export of this software from the United States of America may
 *   require a specific license from the United States Government.
 *   It is the responsibility of any person or organization contemplating
 *   export to obtain such a license before exporting.
 * 
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of M.I.T. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  Furthermore if you modify this software you must label
 * your software as modified software and not distribute it in such a
 * fashion that it might be confused with the original M.I.T. software.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 * 
 *
 * A simple program to test the functionality of the resolver library.
 * It simply will try to get the IP address of the host, and then look 
 * up the name from the address. If the resulting name does not contain the
 * domain name, then the resolve library is broken.
 *
 * Warning: It is possible to fool this program into thinking everything is 
 * alright byt a clever use of /etc/hosts - but this is better than nothing.
 *
 * Usage:
 *   resolve [hostname]
 *
 *   When invoked with no arguments, gethostname is used for the local host.
 *
 */

/* This program tests the resolve library and sees if it is broken... */

#include <stdio.h>

#if STDC_HEADERS
#include <string.h>
#else
#ifndef HAVE_STRCHR
#define strchr index
#endif
char *strchr();
#endif

#ifdef HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif

#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif

#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include <netdb.h>

int
main(argc, argv)
     int argc;
     char **argv;
{
	char myname[MAXHOSTNAMELEN+1];
	char *ptr;
	char addrcopy[4];
	struct hostent *host;
	int quiet = 0;

	argc--; argv++;
	while (argc) {
	    if ((strcmp(*argv, "--quiet") == 0) ||
		(strcmp(*argv, "-q") == 0)) {
		quiet++;
	    } else 
		break;
	    argc--; argv++;
	}

	if (argc >= 1) {
		strncpy(myname, *argv, MAXHOSTNAMELEN);
	} else {
		if(gethostname(myname, MAXHOSTNAMELEN)) {
			perror("gethostname failure");
			exit(1);
		}
	}
	
	myname[MAXHOSTNAMELEN] = '\0';	/* for safety */
	
	/* Look up the address... */
	if (!quiet)
	    printf("Hostname:  %s\n", myname);
	

	/* Set the hosts db to close each time - effectively rewinding file */
	sethostent(0);

	if((host = gethostbyname (myname)) == NULL) {
		fprintf(stderr,
			"Could not look up address for hostname '%s' - fatal\n",
			myname);
		exit(2);
	}
	
	ptr = host->h_addr_list[0];
#define UC(a) (((int)a)&0xff)
	if (!quiet)
	    printf("Host address: %d.%d.%d.%d\n", 
		   UC(ptr[0]), UC(ptr[1]), UC(ptr[2]), UC(ptr[3]));

	memcpy(addrcopy, ptr, 4);

	/* Convert back to full name */
	if((host = gethostbyaddr(addrcopy, 4, AF_INET)) == NULL) {
		fprintf(stderr, "Error looking up IP address - fatal\n");
		exit(2);
	}
	
	if (quiet)
	    printf("%s\n", host->h_name);
	else
	    printf("FQDN: %s\n", host->h_name);
	
	/*
	 * The host name must have at least one '.' in the name, and
	 * if there is only one '.', it must not be at the end of the
	 * string.  (i.e., "foo." is not a FQDN)
	 */
	ptr = strchr(host->h_name, '.');
	if (ptr == NULL || ptr[1] == '\0') {
		fprintf(stderr,
			"\nResolve library did not return a "
			"fully qualified domain name.\n\n"
			"If you are using /etc/hosts before DNS, "
			"e.g. \"files\" is listed first\n"
			"for \"hosts:\" in nsswitch.conf, ensure that "
			"you have listed the FQDN\n"
			"as the first name for the local host.\n\n"
			"If this does not correct the problem, "
			"you may have to reconfigure the kerberos\n"
			"distribution to select a "
			"different set of libraries using \n"
			"--with-netlib[=libs]\n");
		exit(3);
	}

	if (!quiet)
	    printf("Resolve library appears to have passed the test\n");

	/* All ok */
	exit(0);

}