#
/* nettime.c */

/* EMACS_MODES: c !fill */

/* This file contains the routines to deal with the Internet time
 * servers for finding out the time.  Presently the addresses
 * of the available Internet time servers are compiled in; the
 * routine udptime () goes out to all the available Internet
 * time servers to try to get the time.
 * This file contains the following routines:
 *	udptime		ask some udp timeservers what time it is
 */

typedef	long	time_t;			/* ugly! */

#include	<stdio.h>
#include	<udp.h>


#define	TIMEOUT		5		/* response timeout */
#define	TIMESOCK	37		/* time server socket */
#define	MAGICFUDGE	0x83AA7e80	/* seconds from 1900 to 1970 */


/* Table of all known timeservers */

static in_name timeservers[] = {
	0x000A0600,			/* mit-multics */
	0x04800700,			/* dcn7 */
};
static	int	ntsrv = sizeof(timeservers)/sizeof(in_name);

time_t	udptime ()

/* Try to find the current time by asking other udp timeservers.
 * Build timeserver requests for each of the timeservers we presently
 * know about, send them all out, then wait for responses.  Returns
 * the time in seconds since midnight Jan 1 1970 GMT, or 0 if unknown.
 */
{
	register in_name	*pn;	/* pointer to current ts */
	register struct	udp	*pup;	/* ptr. to udp header */
	register struct	ip	*pip;	/* ptr. to internet header */
	unshort	*ptm;			/* ptr. to returned time */
	unshort	locsoc;			/* local socket number */
	caddr_t	inpkt;			/* received packet */
	caddr_t	outpkt;			/* output packet */
	int	udpfd;			/* udp file descriptor */
	union	{
		time_t	r_time;
		unshort	r_word[2];
	} res;				/* returned time */
	int	rcvlen;			/* len of received packet */
	int	i;			/* temp index */

	locsoc = udp_socket ();

	if ((udpfd = udp_open (0L, 0, locsoc)) < 0)
		return (0L);

	if ((inpkt = udp_alloc (INETLEN, 0)) == NULL)
		return (0L);
	if ((outpkt = udp_alloc (0, 0)) == NULL) {
		udp_free (inpkt);
		return (0L);
	}
		
	pip = in_head(outpkt);		 /* get headers */
	pup = udp_head(pip);

	for (pn = &timeservers[0]; pn < &timeservers[ntsrv]; pn++) {
		pip->ip_dest = *pn;	/* set up headers */
		pip->ip_id = 0;		/* kernel fills id */
		pup->ud_srcp = locsoc;	/* udp headers must be built here */
		pup->ud_dstp = TIMESOCK; /* they're byteswapped in pkt */

		udp_write (udpfd, outpkt, 0);
#ifdef	DEBUG
		in_logpkt (outpkt,sizeof(struct udp),OUTPKT);
#endif
	}


	res.r_time = 0L;
	if ((rcvlen = udp_bread (udpfd, inpkt, INETLEN, TIMEOUT)) > 0) {
		pip = in_head(inpkt);
		pup = udp_head(pip);
		ptm = (unshort *)udp_data(pup);
#ifdef	DEBUG
		in_logpkt (inpkt,pup->ud_len,INPKT);
#endif
		res.r_word[0] = short_to_net (*ptm++); /* byte swap */
		res.r_word[1] = short_to_net (*ptm++); /* the sucker */
		res.r_time -= MAGICFUDGE; /* cvt to 1970-based time */
	}

	udp_close (udpfd);
	udp_free (outpkt);
	udp_free (inpkt);
	return (res.r_time);
}