look_up.c

压缩包中包含LINUX下多个命令的源码

/*
 * Copyright (c) 1983, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static char sccsid[] = "@(#)look_up.c	8.1 (Berkeley) 6/6/93";
#endif /* not lint */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#ifdef HAVE_OSOCKADDR_H
#include <osockaddr.h>
#endif
#include <protocols/talkd.h>
#include <errno.h>
#include "talk_ctl.h"
#include "talk.h"

/*
 * See if the local daemon has an invitation for us.
 */
int
check_local()
{
	CTL_RESPONSE response;
	register CTL_RESPONSE *rp = &response;

	/* the rest of msg was set up in get_names */
	msg.ctl_addr.sa_family = htons (ctl_addr.sin_family);
	memcpy (msg.ctl_addr.sa_data,
		((struct sockaddr *)&ctl_addr)->sa_data,
		sizeof ((struct sockaddr *)&ctl_addr)->sa_data);

	/* must be initiating a talk */
	if (!look_for_invite(rp))
		return (0);
	/*
	 * There was an invitation waiting for us,
	 * so connect with the other (hopefully waiting) party
	 */
	current_state = "Waiting to connect with caller";
	do {
		if (rp->addr.sa_family != AF_INET)
			p_error("Response uses invalid network address");
		errno = 0;
		if (connect(sockt,
		    (struct sockaddr *)&rp->addr, sizeof (rp->addr)) != -1)
			return (1);
	} while (errno == EINTR);
	if (errno == ECONNREFUSED) {
		/*
		 * The caller gave up, but his invitation somehow
		 * was not cleared. Clear it and initiate an
		 * invitation. (We know there are no newer invitations,
		 * the talkd works LIFO.)
		 */
		ctl_transact(his_machine_addr, msg, DELETE, rp);
		close(sockt);
		open_sockt();
		return (0);
	}
	p_error("Unable to connect with initiator");
	/*NOTREACHED*/
}

/*
 * Look for an invitation on 'machine'
 */
int
look_for_invite(rp)
	CTL_RESPONSE *rp;
{
	struct in_addr machine_addr;

	current_state = "Checking for invitation on caller's machine";
	ctl_transact(his_machine_addr, msg, LOOK_UP, rp);
	/* the switch is for later options, such as multiple invitations */
	switch (rp->answer) {

	case SUCCESS:
		msg.id_num = htonl(rp->id_num);
		return (1);

	default:
		/* there wasn't an invitation waiting for us */
		return (0);
	}
}