host.c

早期freebsd实现

	/* return overall result */
	return(excode);
}

/*
** PROCESS_NAME -- Process a single command line argument
** ------------------------------------------------------
**
**	Returns:
**		EX_OK if information was obtained successfully.
**		Appropriate exit code otherwise.
**
**	Wrapper for execute_name() to hide administrative tasks.
*/

int
process_name(name)
input char *name;			/* command line argument */
{
	int result;			/* result status of action taken */
	static int save_querytype;
	static bool save_reverse;
	static bool firstname = TRUE;

	/* separate subsequent pieces of output */
	if (!firstname && (verbose || debug || checkmode))
		printf("\n");

/*
 * Some global variables are redefined further on. Save their initial
 * values in the first pass, and restore them during subsequent passes.
 */
	if (firstname)
	{
		save_querytype = querytype;
		save_reverse = reverse;
		firstname = FALSE;
	}
	else
	{
		querytype = save_querytype;
		reverse = save_reverse;
	}

/*
 * Do the real work.
 */
	result = execute_name(name);
	return(result);
}

/*
** EXECUTE_NAME -- Process a single command line argument
** ------------------------------------------------------
**
**	Returns:
**		EX_OK if information was obtained successfully.
**		Appropriate exit code otherwise.
**
**	Outputs:
**		Defines queryname appropriately.
**
**	Side effects:
**		May redefine querytype and reverse if necessary.
*/

int
execute_name(name)
input char *name;			/* command line argument */
{
	ipaddr_t addr;			/* explicit address of query */
	bool result;			/* result status of action taken */

	/* check for nonsense input name */
	if (strlength(name) > MAXDNAME)
	{
		errmsg("Query name %s too long", name);
		return(EX_USAGE);
	}

/*
 * Analyze name and type to be queried about.
 * In regular mode, the querytype is used to formulate the nameserver
 * query, and any response is filtered out when processing the answer.
 * In listmode, the querytype is used to filter out the proper records.
 */
	queryname = name;
	if (queryname[0] == '\0')
		queryname = ".";

	if (sameword(queryname, "."))
		addr = NOT_DOTTED_QUAD;
	else
		addr = inet_addr(queryname);

	/* invert dotted quad if so requested */
	if ((addr != NOT_DOTTED_QUAD) && reverse)
	{
		queryname = in_addr_arpa(queryname);
		if (queryname == NULL)
		{
			errmsg("Invalid dotted quad %s", name);
			return(EX_USAGE);
		}

		addr = NOT_DOTTED_QUAD;
	}
	else
		reverse = FALSE;

	/* set querytype for regular mode if unspecified */
	if ((querytype == T_NONE) && !listmode)
	{
		if ((addr != NOT_DOTTED_QUAD) || reverse)
			querytype = T_PTR;
		else
			querytype = T_A;
	}

	/* cannot have dotted quad in listmode */
	if (listmode && (addr != NOT_DOTTED_QUAD))
	{
		errmsg("Invalid query name %s", queryname);
		return(EX_USAGE);
	}

	/* must have regular name or dotted quad in addrmode */
	if (addrmode && reverse)
	{
		errmsg("Invalid query name %s", queryname);
		return(EX_USAGE);
	}

	/* show what we are going to query about */
	if (verbose)
		show_types(queryname, querytype, queryclass);

/*
 * All set. Perform requested function.
 */
	result = execute(addr);
	return(result ? EX_OK : EX_UNAVAILABLE);
}

/*
** EXECUTE -- Perform the requested function
** -----------------------------------------
**
**	Returns:
**		TRUE if information was obtained successfully.
**		FALSE otherwise.
**
**	The whole environment has been set up and checked.
*/

bool
execute(addr)
input ipaddr_t addr;			/* explicit address of query */
{
	struct hostent *hp;
	char newnamebuf[MAXDNAME+1];
	char *newname = NULL;		/* name to which CNAME is aliased */
	int ncnames = 0;		/* count of CNAMEs in chain */
	bool result;			/* result status of action taken */

/*
 * Special mode to check reverse mappings of host addresses.
 */
	if (addrmode)
	{
		if (addr == NOT_DOTTED_QUAD)
			result = check_addr(queryname);
		else
			result = check_name(addr);
		return(result);
	}

/*
 * Special mode to list contents of specified zone.
 */
	if (listmode)
	{
		result = list_zone(queryname);
		return(result);
	}

/*
 * Regular mode to query about specified host.
 */
	result = FALSE;
	h_errno = TRY_AGAIN;

	/* retry until positive result or permanent failure */
	while (result == FALSE && h_errno == TRY_AGAIN)
	{
		/* reset before each query */
		realname = NULL;

		if (addr == NOT_DOTTED_QUAD)
		{
			/* reset CNAME indicator */
			cname = NULL;

			/* lookup the name in question */
			if (newname == NULL)
				result = get_hostinfo(queryname);
			else
				result = get_hostinfo(newname);

			/* recurse on CNAMEs, but not too deep */
			if (cname && (querytype != T_CNAME))
			{
				newname = strcpy(newnamebuf, cname);

				if (++ncnames > 5)
				{
					errmsg("Possible CNAME loop");
					return(FALSE);
				}

				result = FALSE;
				h_errno = TRY_AGAIN;
				continue;
			}
		}
		else
		{
			hp = gethostbyaddr((char *)&addr, sizeof(addr), AF_INET);
			if (hp != NULL)
			{
				print_host("Name", hp);
				result = TRUE;
			}
		}

		/* only retry if so requested */
		if (!waitmode)
			break;
	}

	/* use actual name if available */
	if (realname != NULL)
		queryname = realname;

	/* explain the reason of a failure */
	if (result == FALSE)
		ns_error(queryname, querytype, queryclass);

	return(result);
}

/*
** SET_SERVER -- Override default nameserver with explicit server
** --------------------------------------------------------------
**
**	Returns:
**		None.
**		Aborts the program if an unknown host was given.
**
**	Side effects:
**		The global variable server is set to indicate
**		that an explicit server is being used.
**
**	The default nameserver addresses in the resolver database
**	which are initialized by res_init() from /etc/resolv.conf
**	are replaced with the (possibly multiple) addresses of an
**	explicitly named server host. If a dotted quad is given,
**	only that single address will be used.
*/

void
set_server(name)
input char *name;			/* name of server to be queried */
{
	register int i;
	struct hostent *hp;
	struct in_addr inaddr;
	ipaddr_t addr;			/* explicit address of server */

	/* check for nonsense input name */
	if (strlength(name) > MAXDNAME)
	{
		errmsg("Server name %s too long", name);
		exit(EX_USAGE);
	}

	addr = inet_addr(name);
	inaddr.s_addr = addr;
	if (addr == NOT_DOTTED_QUAD)
	{
		/* lookup all of its addresses; this must not fail */
		hp = gethostbyname(name);
		if (hp == NULL)
		{
			ns_error(name, T_A, C_IN);
			errmsg("Error in looking up server name");
			exit(EX_NOHOST);
		}

		for (i = 0; i < MAXNS && hp->h_addr_list[i]; i++)
		{
			nslist(i).sin_family = AF_INET;
			nslist(i).sin_port = htons(NAMESERVER_PORT);
			nslist(i).sin_addr = incopy(hp->h_addr_list[i]);
		}
		_res.nscount = i;
	}
	else
	{
		/* lookup the name, but use only the given address */
		hp = gethostbyaddr((char *)&addr, sizeof(addr), AF_INET);

		nslist(0).sin_family = AF_INET;
		nslist(0).sin_port = htons(NAMESERVER_PORT);
		nslist(0).sin_addr = inaddr;
		_res.nscount = 1;
	}

	if (hp != NULL)
	{
		server = strcpy(serverbuf, hp->h_name);
		print_host("Server", hp);
	}
	else
	{
		server = strcpy(serverbuf, inet_ntoa(inaddr));
		printf("Server: %s\n\n", server);
	}
}

/*
** FATAL -- Abort program when illegal option encountered
** ------------------------------------------------------
**
**	Returns:
**		Aborts after issuing error message.
*/

void /*VARARGS1*/
fatal(fmt, a, b, c, d)
input char *fmt;			/* format of message */
input char *a, *b, *c, *d;		/* optional arguments */
{
	(void) fprintf(stderr, fmt, a, b, c, d);
	(void) fprintf(stderr, "\n");
	exit(EX_USAGE);
}


/*
** ERRMSG -- Issue error message to error output
** ---------------------------------------------
**
**	Returns:
**		None.
**
**	Side effects:
**		Increments the global error count.
*/

void /*VARARGS1*/
errmsg(fmt, a, b, c, d)
input char *fmt;			/* format of message */
input char *a, *b, *c, *d;		/* optional arguments */
{
	(void) fprintf(stderr, fmt, a, b, c, d);
	(void) fprintf(stderr, "\n");

	/* flag an error */
	Errors++;
}

/*
** GET_HOSTINFO -- Principal routine to query about given name
** -----------------------------------------------------------
**
**	Returns:
**		TRUE if requested info was obtained successfully.
**		FALSE otherwise.
**
**	This is the equivalent of the resolver module res_search().
**
**	In this program RES_DEFNAMES is always on, and RES_DNSRCH
**	is off by default. This means that single names without dot
**	are always, and only, tried within the own default domain,
**	and compound names are assumed to be already fully qualified.
**
**	The default BIND behaviour can be simulated by turning on
**	RES_DNSRCH with -R. The given name, whether or not compound,
**	is then	first tried within the possible search domains.
**
**	Note. In the latter case, the search terminates in case the
**	specified name exists but does not have the desired type.
**	The BIND behaviour is to continue the search. This can be
**	simulated with the undocumented option -B.
*/

bool
get_hostinfo(name)
input char *name;			/* name to query about */
{
	register char **domain;
	register char *cp;
	int dot;			/* number of dots in query name */
	bool result;			/* result status of action taken */
	char oldnamebuf[2*MAXDNAME+2];
	char *oldname;			/* saved actual name when NO_DATA */
	int nodata = 0;			/* NO_DATA status during DNSRCH */
	int nquery = 0;			/* number of extra search queries */

/*
 * Single dot means root zone.
 */
	if (sameword(name, "."))
	{
		result = get_domaininfo(name, (char *)NULL);
		return(result);
	}

/*
 * Count number of dots. Move to the end of the name.
 */
	for (dot = 0, cp = name; *cp != '\0'; cp++)
		if (*cp == '.')
			dot++;

/*
 * Check for aliases of single name.
 * Note that the alias is supposed to be fully qualified.
 */
	if (dot == 0 && (cp = hostalias(name)) != NULL)
	{
		if (verbose)
			printf("Aliased to \"%s\"\n", cp);

		result = get_domaininfo(cp, (char *)NULL);
		return(result);
	}

/*
 * Trailing dot means absolute (fully qualified) address.
 */
	if (dot != 0 && cp[-1] == '.')
	{
		cp[-1] = '\0';
		result = get_domaininfo(name, (char *)NULL);
		cp[-1] = '.';
		return(result);
	}

/*
 * Append own default domain and other search domains if appropriate.
 */
	if ((dot == 0 && bitset(RES_DEFNAMES, _res.options)) ||
	    (dot != 0 && bitset(RES_DNSRCH, _res.options)))
	{
		for (domain = _res.dnsrch; *domain; domain++)
		{
			result = get_domaininfo(name, *domain);
			if (result)
				return(result);

			/* keep count of extra search queries */
			nquery++;

			/* in case nameserver not present */
			if (errno == ECONNREFUSED)
				return(FALSE);

			/* if no further search desired (single name) */
	    		if (!bitset(RES_DNSRCH, _res.options))
				break;

			/* if name exists but has not requested type */
			if (h_errno == NO_DATA || h_errno == NO_RREC)
			{
				if (bindcompat)
				{
					/* remember status and search up */
					oldname = strcpy(oldnamebuf, realname);
					nodata = h_errno;
					continue;
				}

				return(FALSE);
			}

			/* retry only if name does not exist at all */
			if (h_errno != HOST_NOT_FOUND && h_errno != NO_HOST)
				break;
		}
	}

/*
 * Single name lookup failed.
 */
	if (dot == 0)
	{
		/* unclear what actual name should be */
		if (nquery != 1)
			realname = NULL;

		/* restore nodata status from search */
		if (bindcompat && nodata)
		{
			realname = strcpy(realnamebuf, oldname);
			h_errno = nodata;
		}

		/* set status in case we never queried */
		if (!bitset(RES_DEFNAMES, _res.options))
			h_errno = HOST_NOT_FOUND;

		return(FALSE);
	}