host.c

dos 下 网络协议 dos 下 网络协议

#include <copyright.h>
#include <stdio.h>
#include <string.h>
#include <tcp.h>

/* domain name server protocol
 *
 * This portion of the code needs some major work.  I ported it (read STOLE IT)
 * from NCSA and lost about half the code somewhere in the process.
 *
 * Note, this is a user level process.  We include <tcp.h> not <wattcp.h>
 *
 *  0.2 : Apr 24, 1991 - use substring portions of domain
 *  0.1 : Mar 18, 1991 - improved the trailing domain list
 *  0.0 : Feb 19, 1991 - pirated by Erick Engelke
 * -1.0 :              - NCSA code
 */


/* These next 'constants' are loaded from WATTCP.CFG file */

extern char *def_domain;
extern char *loc_domain;       /* current subname to be used by the domain system */

extern longword def_nameservers[ MAX_NAMESERVERS ];
extern int _last_nameserver;
extern word _domaintimeout = 0;

static longword timeoutwhen;

/*
longword def_nameserver;
longword def2_nameserver;
*/
static udp_Socket *dom_sock;

#define DOMSIZE 512				/* maximum domain message size to mess with */

/*
 *  Header for the DOMAIN queries
 *  ALL OF THESE ARE BYTE SWAPPED QUANTITIES!
 *  We are the poor slobs who are incompatible with the world's byte order
 */
struct dhead {
    word	ident,		/* unique identifier */
		flags,
		qdcount,	/* question section, # of entries */
		ancount,	/* answers, how many */
		nscount,	/* count of name server RRs */
		arcount;	/* number of "additional" records */
};

/*
 *  flag masks for the flags field of the DOMAIN header
 */
#define DQR		0x8000	/* query = 0, response = 1 */
#define DOPCODE		0x7100	/* opcode, see below */
#define DAA		0x0400	/* Authoritative answer */
#define DTC		0x0200	/* Truncation, response was cut off at 512 */
#define DRD		0x0100	/* Recursion desired */
#define DRA		0x0080	/* Recursion available */
#define DRCODE		0x000F	/* response code, see below */

/* opcode possible values: */
#define DOPQUERY	0	/* a standard query */
#define DOPIQ           1       /* an inverse query */
#define DOPCQM		2	/* a completion query, multiple reply */
#define DOPCQU		3     	/* a completion query, single reply */
/* the rest reserved for future */

/* legal response codes: */
#define DROK	0		/* okay response */
#define DRFORM	1		/* format error */
#define DRFAIL	2		/* their problem, server failed */
#define DRNAME	3		/* name error, we know name doesn't exist */
#define DRNOPE	4		/* no can do request */
#define DRNOWAY	5		/* name server refusing to do request */

#define DTYPEA		1	/* host address resource record (RR) */
#define DTYPEPTR	12	/* a domain name ptr */

#define DIN		1	/* ARPA internet class */
#define DWILD		255	/* wildcard for several of the classifications */

/*
 *  a resource record is made up of a compressed domain name followed by
 *  this structure.  All of these ints need to be byteswapped before use.
 */
struct rrpart {
    word   	rtype,		/* resource record type = DTYPEA */
		rclass;		/* RR class = DIN */
    longword	ttl;		/* time-to-live, changed to 32 bits */
    word	rdlength;	/* length of next field */
    byte 	rdata[DOMSIZE];	/* data field */
};

/*
 *  data for domain name lookup
 */
static struct useek {
    struct dhead h;
    byte         x[DOMSIZE];
} *question;


/*********************************************************************/
/*  packdom
*   pack a regular text string into a packed domain name, suitable
*   for the name server.
*
*   returns length
*/
static packdom(dst,src)
char *src,*dst;
{
    char *p,*q,*savedst;
    int i,dotflag,defflag;

    p = src;
    dotflag = defflag = 0;
    savedst = dst;

    do {			/* copy whole string */
	*dst = 0;
	q = dst + 1;
	while (*p && (*p != '.'))
	    *q++ = *p++;

	i = p - src;
	if (i > 0x3f)
	    return(-1);
	*dst = i;
	*q = 0;

	if (*p) {					/* update pointers */
	    dotflag = 1;
	    src = ++p;
	    dst = q;
	}
	else if (!dotflag && !defflag && loc_domain) {
	    p = loc_domain;		/* continue packing with default */
	    defflag = 1;
	    src = p;
	    dst = q;
	}
    }
    while (*p);
    q++;
    return(q-savedst);			/* length of packed string */
}

/*********************************************************************/
/*  unpackdom
*  Unpack a compressed domain name that we have received from another
*  host.  Handles pointers to continuation domain names -- buf is used
*  as the base for the offset of any pointer which is present.
*  returns the number of bytes at src which should be skipped over.
*  Includes the NULL terminator in its length count.
*/
static unpackdom(dst,src,buf)
char *src,*dst,buf[];
{
    int i,j,retval;
    char *savesrc;

    savesrc = src;
    retval = 0;

    while (*src) {
	j = *src;

	while ((j & 0xC0) == 0xC0) {
	    if (!retval)
		retval = src-savesrc+2;
	    src++;
	    src = &buf[(j & 0x3f)*256+*src];		/* pointer dereference */
	    j = *src;
	}

	src++;
	for (i=0; i < (j & 0x3f) ; i++)
	    *dst++ = *src++;

	*dst++ = '.';
    }

    *(--dst) = 0;			/* add terminator */
    src++;					/* account for terminator on src */

    if (!retval)
	retval = src-savesrc;

    return(retval);
}

/*********************************************************************/
/*  sendom
*   put together a domain lookup packet and send it
*   uses port 53
*	num is used as identifier
*/
static sendom(s,towho,num)
char *s;
longword towho;
word num;
{
    word i,ulen;
    byte *psave,*p;

    psave = (byte*)&(question->x);
    i = packdom(&(question->x),s);

    p = &(question->x[i]);
    *p++ = 0;				/* high byte of qtype */
    *p++ = DTYPEA;			/* number is < 256, so we know high byte=0 */
    *p++ = 0;				/* high byte of qclass */
    *p++ = DIN;				/* qtype is < 256 */

    question->h.ident = intel16(num);
    ulen = sizeof(struct dhead)+(p-psave);

    udp_open( dom_sock, 997, towho, 53, NULL );    /* divide err */

    sock_write( dom_sock, question, ulen );
    return( ulen);
}


/*********************************************************************/
/*  senrdom
*   put together a reverse domain lookup packet and send it
*   uses port 53
*	num is used as identifier
*/
static sendrdom(char *s, longword towhom, word num )
{
    word i,ulen;
    byte *psave,*p;



    psave = (byte*)&(question->x);
    i = packdom(&(question->x),s);

    p = &(question->x[i]);
    *p++ = 0;				/* high byte of qtype */
    *p++ = DTYPEA;                      /* want host address */
    *p++ = 0;				/* high byte of qclass */
    *p++ = DIN;				/* qtype is < 256 */

    question->h.ident = intel16(num);
    ulen = sizeof(struct dhead)+(p-psave);

    udp_open( dom_sock, 997, towho, 53, NULL );    /* divide err */

    sock_write( dom_sock, question, ulen );
    return( ulen);
}

static int countpaths(pathstring)
char *pathstring;
{
    int     count = 0;
    char    *p;

    for(p=pathstring; (*p != 0) || (*(p+1) != 0); p++) {
	if(*p == 0)
	    count++;
    }
    return(++count);
}

static char *getpath(pathstring,whichone)
char *pathstring;            /* the path list to search      */
int   whichone;               /* which path to get, starts at 1 */
{
    char    *retval;

    if(whichone > countpaths(pathstring))
	return(NULL);
    whichone--;
    for(retval = pathstring;whichone ; retval++ ) {
	if(*retval == 0)
	    whichone--;
    }
    return(retval);
}

/*********************************************************************/
/*  ddextract
*   extract the ip number from a response message.