host.c

dos 下 网络协议 dos 下 网络协议

*   returns the appropriate status code and if the ip number is available,
*   copies it into mip
*/
static longword ddextract(qp,mip)
struct useek *qp;
unsigned char *mip;
{
    word i,j,nans,rcode;
    struct rrpart *rrp;
    byte *p,space[260];

    nans = intel16(qp->h.ancount);		/* number of answers */
    rcode = DRCODE & intel16(qp->h.flags);	/* return code for this message*/
    if (rcode > 0)
	return(rcode);

    if (nans > 0 &&								/* at least one answer */
    (intel16(qp->h.flags) & DQR)) {			/* response flag is set */
    p = (byte *)&qp->x;                 /* where question starts */
	i = unpackdom(space,p,qp);				/* unpack question name */
	/*  spec defines name then  QTYPE + QCLASS = 4 bytes */
	p += i+4;
printf(" NAME : ? %s\n", space );
        
/*
 *  at this point, there may be several answers.  We will take the first
 *  one which has an IP number.  There may be other types of answers that
 *  we want to support later.
 */
	while (nans-- > 0) {					/* look at each answer */
	    i = unpackdom(space,p,qp);			/* answer name to unpack */
	    /*			n_puts(space);*/
	    p += i;								/* account for string */
	    rrp = (struct rrpart *)p;			/* resource record here */
 /*
  *  check things which might not align on 68000 chip one byte at a time
  */
	    if (!*p && *(p+1) == DTYPEA && 		/* correct type and class */
	    !*(p+2) && *(p+3) == DIN) {
		movmem(rrp->rdata,mip,4);	/* save IP # 		*/
		return(0);						/* successful return */
	    }
	    movmem(&rrp->rdlength,&j,2);	/* 68000 alignment */
	    p += 10+intel16(j);				/* length of rest of RR */
	}
    }

    return(-1);						/* generic failed to parse */
}

/*********************************************************************/
/*  getdomain
*   Look at the results to see if our DOMAIN request is ready.
*   It may be a timeout, which requires another query.
*/

static longword udpdom()
{
    int i,uret;
    longword desired;

    uret = sock_fastread(dom_sock, question, sizeof(struct useek ));
    /* this does not happen */
    if (uret < 0) {
	/*		netputevent(USERCLASS,DOMFAIL,-1);  */
	return(-1);
    }

 /* num = intel16(question->h.ident); */     /* get machine number */
/*
 *  check to see if the necessary information was in the UDP response
 */

    i = ddextract(question, &desired);
    switch (i) {
        case 3:	return(0);		/* name does not exist */
        case 0: return(intel(desired)); /* we found the IP number */
        case -1:return( 0 );		/* strange return code from ddextract */
        default:return( 0 );            /* dunno */
    }
}


/**************************************************************************/
/*  Sdomain
*   DOMAIN based name lookup
*   query a domain name server to get an IP number
*	Returns the machine number of the machine record for future reference.
*   Events generated will have this number tagged with them.
*   Returns various negative numbers on error conditions.
*
*   if adddom is nonzero, add default domain
*/
static longword Sdomain(mname, adddom, nameserver, timedout )
char *mname;
int adddom;
longword nameserver;
int *timedout;	/* set to 1 on timeout */
{
    char namebuff[512];
    int isaname;
    int domainsremaining;
    int status, i;
    longword response;

    isaname = !isaddr( mname );
    response = 0;
    *timedout = 1;

    if (!nameserver) {	/* no nameserver, give up now */
	outs("No nameserver defined!\n\r");
	return(0);
    }

    while (*mname && *mname < 33) mname ++;   /* kill leading spaces */

    if (!(*mname))
	return(0L);

    question->h.flags = intel16(DRD);   /* use recursion */
    question->h.qdcount = 0;
    question->h.ancount = 0;
    question->h.nscount = 0;
    question->h.arcount = 0;

    qinit();				/* initialize some flag fields */

    strcpy( namebuff, mname );

    if ( isaname ) {
        /* forward lookup */
        /* only add these things if we are doing a real name */

        question->h.qdcount = intel16(1);
        if ( adddom ) {
            if(namebuff[strlen(namebuff)-1] != '.') {       /* if no trailing dot */
                if(loc_domain) {             /* there is a search list */
                    domainsremaining = countpaths( loc_domain );

                    strcat(namebuff,".");
                    strcat(namebuff,getpath(loc_domain,1));
                }
            } else
                namebuff[ strlen(namebuff)-1] = 0;  /* kill trailing dot */
        }
    } else {
        /* reverse lookup */
        question->h.ancount = intel16(1);

    }
    /*
     * This is not terribly good, but it attempts to use a binary
     * exponentially increasing delays.
     */

     for ( i = 2; i < 17; i *= 2) {
        if ( isaname ) sendom(namebuff,nameserver, 0xf001);    /* try UDP */
        else sendrdom( namebuff, nameserver, 0xf001 );

        ip_timer_init( dom_sock, i );
        do {
            kbhit();
            tcp_tick( dom_sock );
            if (ip_timer_expired( dom_sock )) break;
            if ( watcbroke ) {
                break;
            }
            if (chk_timeout( timeoutwhen ))
                break;
            if ( sock_dataready( dom_sock )) *timedout = 0;
        } while ( *timedout );

	if ( !*timedout ) break;	/* got an answer */
    }

    if ( !*timedout )
	response = udpdom();	/* process the received data */

    sock_close( dom_sock );
    return( response );
}

/*
 * nextdomain - given domain and count = 0,1,2,..., return next larger
 *		domain or NULL when no more are available
 */
static char *nextdomain( char *domain, int count )
{
    char *p;
    int i;

    p = domain;

    for (i = 0; i < count; ++i) {
	p = strchr( p, '.' );
	if (!p) return( NULL );
	++p;
    }
    return( p );
}


/*
 * newresolve()
 * 	convert domain name -> address resolution.
 * 	returns 0 if name is unresolvable right now
 */
longword newresolve(name)
char *name;
{
    longword ip_address, temp;
    int count, i;
    byte timeout[ MAX_NAMESERVERS ];
    struct useek qp;        /* temp buffer */
    udp_Socket ds;          /* temp buffer */
    word oldhndlcbrk;


    question = &qp;
    dom_sock = &ds;
    if (!name) return( 0 );
    rip( name );

    if (!_domaintimeout) _domaintimeout = sock_delay << 2;
    timeoutwhen = set_timeout( _domaintimeout );

    count = 0;
    memset( &timeout, 0, sizeof( timeout ));

    oldhndlcbrk = wathndlcbrk;
    wathndlcbrk = 1;        /* enable special interrupt mode */
    watcbroke = 0;
    do {
	if (!(loc_domain = nextdomain( def_domain, count )))
		count = -1;	/* use default name */

	for ( i = 0; i < _last_nameserver ; ++i ) {
	    if (!timeout[i])
		if (ip_address = Sdomain( name , count != -1 ,
			def_nameservers[i], &timeout[i] ))
		    break;	/* got name, bail out of loop */
	}

	if (count == -1) break;
	count++;
    } while (!ip_address);
    watcbroke = 0;          /* always clean up */
    wathndlcbrk = oldhndlcbrk;

    return( ip_address );
}



main(int argc, char **argv )
{
    char *name;
    longword host;
    int status,i;
    char buffer[ 20];

    if (argc < 2) {
        puts("HOST  hostname");
        exit(3);
    }

    sock_init();

    for ( i = 1 ; i < argc ; ++i ) {
        if ((*argv[i] == '/') || (*argv[i] == '-' )) {
        }
        else {
            name = strdup( argv[i] );

            printf("resolving \"%s\"...", name );
            host = newresolve( name );
            printf("\r");
            clreol();
        }
    }
    if ( host ) {
        printf("\r");
        clreol();
        printf("%s : %s\n", name, inet_ntoa( buffer , host ));
    }
    exit( host ? 0 : 1 );
}
/* udpdom &&  ddextract(question, &desired); */