#
/* name_user.c */

/* EMACS_MODES: c !fill */

/* This file contains the routines to deal with the Internet name
 * servers for resolving Internet names.  Presently the addresses
 * of the available Internet name servers are compiled in; the
 * routine udpname () goes out to all the available Internet
 * name servers to try to resolve the name.
 * This file containst the following routines:
 *	udpname		resolve a name by asking Internet name servers
 */

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


#define	TIMEOUT		15		/* response timeout */


/* Table of all known nameservers */

static struct nstab {
	int	ns_sock;		/* foreign socket */
	in_name ns_name;		/* host address */
} nameservers[] = {
	{ 14, 0x000A0600 },		/* mit-multics */
	{ 14, 0x02128000 },		/* mit-spooler */
	{ 42, 0x000A4900 },		/* sri-nic */
	{ 42, 0x030A0500 },		/* bbna */
	{ 14, 0x000A2C00 },		/* mit-xx */
};
static	int	nnsrv = sizeof(nameservers)/(sizeof(struct nstab));

in_name	udpname (name)

/* Try to resolve the specified name by asking other udp nameservers.
 * Build nameserver requests for each of the nameservers we presently
 * know about, send them all out, then wait for responses.  Returns
 * the internet address, or 0 if unknown.
 * 
 * Arguments:
 */

char	*name;				/* name to be resolved */
{
	register struct	nstab	*pn;	/* pointer to current ns */
	register struct	udp	*pup;	/* ptr. to udp header */
	register struct	ip	*pip;	/* ptr. to internet header */
	struct	nmitem	*pnm;		/* ptr. to packet data area */
	unshort	locsoc;			/* local socket number */
	int	len;			/* length of nameserver request */
	int	done;			/* no. of nameservers responded */
	union {
		char	bytes[4];
		in_name	name;
	} res;				/* result */
	caddr_t	inpkt;			/* received packet */
	caddr_t	outpkt;			/* output packet */
	int	udpfd;			/* udp file descriptor */
	long	now;			/* current time */
	long	donetime;		/* time to finish */
	int	rcvlen;			/* len of received packet */
	int	i;			/* temp index */

	len = strlen (name) + sizeof (struct nmitem);
	locsoc = udp_socket ();


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

	if ((inpkt = udp_alloc (INPKTSIZ, 0)) == NULL)
		return (0L);
	if ((outpkt = udp_alloc (len+1, 0)) == NULL) {
		udp_free (inpkt);
		return (0L);
	}
		
	done = 0;
	pip = in_head(outpkt);		 /* get headers */
	pup = udp_head(pip);
	pnm = (struct nmitem *)udp_data(pup);

	pnm->nm_type = NI_NAME;	/* build common part of request */
	pnm->nm_len = len - 2;
	strcpy (&pnm->nm_item, name);

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

		if (udp_write (udpfd, outpkt, len) <= 0)
			done++;
#ifdef	DEBUG
		else
			in_logpkt (outpkt,len+sizeof(struct udp),OUTPKT);
#endif
	}


	time (&now);
	donetime = now + TIMEOUT;
	while (now < donetime && done < nnsrv) {
		if ((rcvlen = udp_bread (udpfd, inpkt, INPKTSIZ,
			(int)(donetime - now))) > 0) {

			pip = in_head(inpkt);
			pup = udp_head(pip);
			pnm = (struct nmitem *)udp_data(pup);

/* Get to second item in the message - the response */
			
			pnm = (struct nmitem *)(&pnm->nm_item[pnm->nm_len]);
#ifdef	DEBUG
			in_logpkt (inpkt,pup->ud_len,INPKT);
#endif

			if (pnm->nm_type == NI_ADDR) { /* success! */
				for (i = 0; i < sizeof (in_name); i++)
					res.bytes[i] = pnm->nm_item[i];
				udp_close (udpfd);
				udp_free (outpkt);
				udp_free (inpkt);
				return (res.name);
			} 		/* must be error; ignore */
			done++;
			time (&now);
		} else			/* timeout; give up */
			break;
	}

	udp_close (udpfd);
	udp_free (outpkt);
	udp_free (inpkt);
	return (0L);
}