acksend.c

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· C语言 代码 · 共 112 行

#ifndef lint
static	char	*sccsid = "@(#)acksend.c	4.1	(ULTRIX)	7/2/90";
#endif lint

/************************************************************************
 *									*
 *			Copyright (c) 1988 by				*
 *		Digital Equipment Corporation, Maynard, MA		*
 *			All rights reserved.				*
 *									*
 *   This software is furnished under a license and may be used and	*
 *   copied  only  in accordance with the terms of such license and	*
 *   with the  inclusion  of  the  above  copyright  notice.   This	*
 *   software  or  any  other copies thereof may not be provided or	*
 *   otherwise made available to any other person.  No title to and	*
 *   ownership of the software is hereby transferred.			*
 *									*
 *   This software is  derived  from  software  received  from  the	*
 *   University    of   California,   Berkeley,   and   from   Bell	*
 *   Laboratories.  Use, duplication, or disclosure is  subject  to	*
 *   restrictions  under  license  agreements  with  University  of	*
 *   California and with AT&T.						*
 *									*
 *   The information in this software is subject to change  without	*
 *   notice  and should not be construed as a commitment by Digital	*
 *   Equipment Corporation.						*
 *									*
 *   Digital assumes no responsibility for the use  or  reliability	*
 *   of its software on equipment which is not supplied by Digital.	*
 *									*
 ************************************************************************/
/*
 * Copyright (c) 1985 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 *static char sccsid[] = "@(#)acksend.c	2.4 (Berkeley) 5/27/86";
 */


#include "globals.h"
#include <protocols/timed.h>

#define RECEIVED	0
#define LOST	 	1
#define SECFORACK	1	/* seconds */
#define USECFORACK	0	/* microseconds */
#define MAXCOUNT	5

struct tsp *answer;

/*
 * Acksend implements reliable datagram transmission by using sequence 
 * numbers and retransmission when necessary.
 * `name' is the name of the destination
 * `addr' is the address to send to
 * If `name' is ANYADDR, this routine implements reliable broadcast.
 */

struct tsp *acksend(message, addr, name, ack, net)
struct tsp *message;
struct sockaddr_in *addr;
char *name;
int ack;
struct netinfo *net;
{
	int count;
	int flag;
	extern u_short sequence;
	struct timeval tout;
	struct tsp *readmsg();

	count = 0;

	message->tsp_vers = TSPVERSION;
	message->tsp_seq = sequence;
	if (trace) {
		fprintf(fd, "acksend: ");
		if (name == ANYADDR)
			fprintf(fd, "broadcast: ");
		else
			fprintf(fd, "%s: ", name);
		print(message, addr);
	}
	bytenetorder(message);
	do {
		if (sendto(sock, (char *)message, sizeof(struct tsp), 0, addr,
		    sizeof(struct sockaddr_in)) < 0) {
			syslog(LOG_ERR, "acksend: sendto: %m");
			exit(1);
		}
		tout.tv_sec = SECFORACK;
		tout.tv_usec = USECFORACK;
		answer  = readmsg(ack, name, &tout, net);
		if (answer != NULL) {
			if (answer->tsp_seq != sequence) {
				if (trace)
					fprintf(fd, "acksend: seq # %d != %d\n",
					    answer->tsp_seq, sequence);
				continue;
			}
			flag = RECEIVED;
		} else {
			flag = LOST;
			if (++count == MAXCOUNT) {
				break;
			}
		}
	} while (flag != RECEIVED);
	sequence++;
	return(answer);
}