host.c

操作系统源代码

 *  ListHosts --
 *
 *	Requests the name server to do a zone transfer so we
 *	find out what hosts it knows about.
 *
 *  Results:
 *	SUCCESS		the listing was successful.
 *	ERROR		the server could not be contacted because 
 *			a socket could not be obtained or an error
 *			occured while receiving, or the output file
 *			could not be opened.
 *
 ******************************************************************************
 */

static int
ListHosts(namePtr, queryType)
    char *namePtr;
    int  queryType;  /* e.g. T_A */
{
	querybuf_t 		buf, answer;
	dns_hdr_t		*headerPtr;

	int 			msglen;
	int 			amtToRead;
	int 			numRead;
	int 			i;
	int 			numAnswers = 0;
	int 			result;
	int 			soacnt = 0;
	u_short 		len;
	int			dlen;
	int			type;
	int			nscount;
	u8_t 			*cp, *nmp;
	u8_t 			name[NAME_LEN];
	char 			dname[2][NAME_LEN];
	u8_t 			domain[NAME_LEN];
/* names and addresses of name servers to try */
#define NUMNS 8
	char			nsname[NUMNS][NAME_LEN];
	int			nshaveaddr[NUMNS];
#define IPADDRSIZE 4
#define NUMNSADDR 16
	char	 		nsipaddr[NUMNSADDR][IPADDRSIZE];
	int			numns;
	int			numnsaddr;
	int			thisns;
	struct hostent		*hp;
	enum {
	    NO_ERRORS, 
	    ERR_READING_LEN, 
	    ERR_READING_MSG,
	    ERR_PRINTING
	} error = NO_ERRORS;
	char *tcp_serv_name;
	int tcp_fd;
	nwio_tcpconf_t tcpconf;
	nwio_tcpcl_t clopt;
	int terrno;

/*
 * normalize to not have trailing dot.  We do string compares below
 * of info from name server, and it won't have trailing dots.
 */
	i = strlen(namePtr);
	if (namePtr[i-1] == '.')
	  namePtr[i-1] = 0;

	if (server_specified) {
	  bcopy((char *)&_res.nsaddr, nsipaddr[0], IPADDRSIZE);
	  numnsaddr = 1;
	}
	else {

/*
 * First we have to find out where to look.  This needs a NS query,
 * possibly followed by looking up addresses for some of the names.
 */

	msglen = res_mkquery(QUERY, namePtr, C_IN, T_NS,
				(char *)0, 0, (struct rrec *)0, 
				(char *)&buf, sizeof(buf));

	if (msglen < 0) {
		printf("res_mkquery failed\n");
		return (ERROR);
	}

	msglen = res_send((char *)&buf,msglen,(char *)&answer, sizeof(answer));
	
	if (msglen < 0) {
		printf("Unable to get to nameserver -- try again later\n");
		return (ERROR);
	}
	if (_res.options & RES_DEBUG || verbose)
		printf("rcode = %d (%s), ancount=%d\n", 
		       answer.qb1.dh_flag2 & DHF_RCODE,
		       DecodeError(answer.qb1.dh_flag2 & DHF_RCODE),
		       ntohs(answer.qb1.dh_ancount));

/*
 * Analyze response to our NS lookup
 */

	nscount = ntohs(answer.qb1.dh_ancount) + ntohs(answer.qb1.dh_nscount) +
		  ntohs(answer.qb1.dh_arcount);

	if (answer.qb1.dh_flag2 & DHF_RCODE != NOERROR || nscount == 0) {
		switch (answer.qb1.dh_flag2 & DHF_RCODE) {
			case NXDOMAIN:
				/* Check if it's an authoritive answer */
				if (answer.qb1.dh_flag1 & DHF_AA) {
					printf("No such domain\n");
				} else {
					printf("Unable to get information about domain -- try again later.\n");
				}
				break;
			case SERVFAIL:
				printf("Unable to get information about that domain -- try again later.\n");
				break;
			case NOERROR:
				printf("That domain exists, but seems to be a leaf node.\n");
				break;
			case FORMERR:
			case NOTIMP:
			case REFUSED:
				printf("Unrecoverable error looking up domain name.\n");
				break;
		}
		return (0);
	}

	cp = answer.qb2 + sizeof(dns_hdr_t);
	if (ntohs(answer.qb1.dh_qdcount) > 0)
	  cp += dn_skipname(cp, answer.qb2 + msglen) + QFIXEDSZ;

	numns = 0;
	numnsaddr = 0;

/*
 * Look at response from NS lookup for NS and A records.
 */

	for (;nscount; nscount--) {
	  cp += dn_expand(answer.qb2, answer.qb2 + msglen, cp,
			  domain, sizeof(domain));
	  type = _getshort(cp);
	  cp += sizeof(u_short) + sizeof(u_short) + sizeof(u_long);
	  dlen = _getshort(cp);
	  cp += sizeof(u_short);
	  if (type == T_NS) {
	    if (dn_expand(answer.qb2, answer.qb2 + msglen, cp, 
			  name, sizeof(name)) >= 0) {
	      if (numns < NUMNS && strcasecmp((char *)domain, namePtr) == 0) {
		for (i = 0; i < numns; i++)
		  if (strcasecmp(nsname[i], (char *)name) == 0)
		    break;  /* duplicate */
		if (i >= numns) {
		  strncpy(nsname[numns], (char *)name, sizeof(name));
		  nshaveaddr[numns] = 0;
		  numns++;
		}
	      }
	    }
	  }
	  else if (type == T_A) {
	    if (numnsaddr < NUMNSADDR)
	      for (i = 0; i < numns; i++) {
		if (strcasecmp(nsname[i], (char *)domain) == 0) {
		  nshaveaddr[i]++;
		  bcopy((char *)cp, nsipaddr[numnsaddr],IPADDRSIZE);
		  numnsaddr++;
		  break;
		}
	      }
	  }
	  cp += dlen;
	}

/*
 * Usually we'll get addresses for all the servers in the additional
 * info section.  But in case we don't, look up their addresses.
 */

	for (i = 0; i < numns; i++) {
	  if (! nshaveaddr[i]) {
	    register long **hptr;
	    int numaddrs = 0;

	    hp = gethostbyname(nsname[i]);
	    if (hp) {
	      for (hptr = (long **)hp->h_addr_list; *hptr; hptr++)
		if (numnsaddr < NUMNSADDR) {
		  bcopy((char *)*hptr, nsipaddr[numnsaddr],IPADDRSIZE);
		  numnsaddr++;
		  numaddrs++;
		}
	    }
	    if (_res.options & RES_DEBUG || verbose)
	      printf("Found %d addresses for %s by extra query\n",
		     numaddrs, nsname[i]);
	  }
	  else
	    if (_res.options & RES_DEBUG || verbose)
	      printf("Found %d addresses for %s\n",
		     nshaveaddr[i], nsname[i]);
	}
        }
/*
 * Now nsipaddr has numnsaddr addresses for name servers that
 * serve the requested domain.  Now try to find one that will
 * accept a zone transfer.
 */

	thisns = 0;

again:

	numAnswers = 0;
	soacnt = 0;

	/*
	 *  Create a query packet for the requested domain name.
	 *
	 */
	msglen = res_mkquery(QUERY, namePtr, getclass, T_AXFR,
				(char *)0, 0, (struct rrec *)0, 
				(char *) &buf, sizeof(buf));
	if (msglen < 0) {
	    if (_res.options & RES_DEBUG) {
		fprintf(stderr, "ListHosts: Res_mkquery failed\n");
	    }
	    return (ERROR);
	}

	/*
	 *  Set up a virtual circuit to the server.
	 */

	tcp_serv_name= getenv("TCP_DEVICE");
	if (!tcp_serv_name)
		tcp_serv_name= TCP_DEVICE;
	for (;thisns < numnsaddr; thisns++) 
	{
		tcp_fd= open(tcp_serv_name, O_RDWR);
		if (tcp_fd == -1)
		{
			fprintf(stderr, "unable to open '%s': %s\n", tcp_serv_name,
				strerror(errno));
			return ERROR;
		}

		tcpconf.nwtc_flags= NWTC_EXCL | NWTC_LP_SEL | NWTC_SET_RA | 
								NWTC_SET_RP;
		tcpconf.nwtc_remaddr= *(ipaddr_t *)nsipaddr[thisns];
		tcpconf.nwtc_remport= HTONS(NAMESERVER_PORT);
		result= ioctl(tcp_fd, NWIOSTCPCONF, &tcpconf);
		if (result == -1)
		{
			fprintf(stderr, "tcp_ioc_setconf failed: %s\n", 
				strerror(errno));
			close(tcp_fd);
			return ERROR;
		}
		if (_res.options & RES_DEBUG || verbose)
			printf("Trying %s\n", inet_ntoa(tcpconf.nwtc_remaddr));
		clopt.nwtcl_flags= 0;
		result= ioctl(tcp_fd, NWIOTCPCONN, &clopt);
		if (result == 0)
			break;
		terrno= errno;
		if (verbose)
			fprintf(stderr, 
				"Connection failed, trying next server: %s\n",
				strerror(errno));
		close(tcp_fd);
	}	
	if (thisns >= numnsaddr) {
	  printf("No server for that domain responded\n");
	  if (!verbose)
	    fprintf(stderr, "Error from the last server was: %s\n", 
						strerror(terrno));
	  return(ERROR);
	}

	/*
	 * Send length & message for zone transfer 
	 */

        len = htons(msglen);

	result= tcpip_writeall(tcp_fd, (char *)&len, sizeof(len));
	if (result != sizeof(len))
	{
		fprintf(stderr, "write failed: %s\n", strerror(errno));
		close(tcp_fd);
		return ERROR;
	}
	result= tcpip_writeall(tcp_fd, (char *)&buf, msglen);
	if (result != msglen)
	{
		fprintf(stderr, "write failed: %s\n",
			strerror(errno));
		close(tcp_fd);
		return ERROR;
	}
	filePtr = stdout;

	while (1) {

	    /*
	     * Read the length of the response.
	     */

	    cp = (u8_t *) &buf;
	    amtToRead = sizeof(u_short);
	    while(amtToRead > 0)
	    {
		result = read(tcp_fd, (char *)cp, amtToRead);
		if (result <= 0)
			break;
		cp 	  += result;
		amtToRead -= result;
	    }
	    if (amtToRead) {
		error = ERR_READING_LEN;
		break;
	    }	

	    if ((len = htons(*(u_short *)&buf)) == 0) {
		break;	/* nothing left to read */
	    }

	    /*
	     * Read the response.
	     */

	    amtToRead = len;
	    cp = (u8_t *) &buf;
	    while(amtToRead > 0)
	    {
		result = read(tcp_fd, (char *)cp, amtToRead);
		if (result<= 0)
			break;
		cp 	  += result;
		amtToRead -= result;
	    }
	    if (amtToRead) {
		error = ERR_READING_MSG;
		break;
	    }

	    i = buf.qb1.dh_flag2 & DHF_RCODE;
	    if (i != NOERROR || ntohs(buf.qb1.dh_ancount) == 0) {
	      if ((thisns+1) < numnsaddr &&
		  (i == SERVFAIL || i == NOTIMP || i == REFUSED)) {
		if (_res.options & RES_DEBUG || verbose)
		  printf("Server failed, trying next server: %s\n",
			 i != NOERROR ? 
			 DecodeError(i) : "Premature end of data");
		close(tcp_fd);
		thisns++;
		goto again;
	      }
	      printf("Server failed: %s\n",
		     i != NOERROR ? DecodeError(i) : "Premature end of data");
	      break;
	    }


	    result = printinfo(&buf, cp, queryType, 1);
	    if (! result) {
		error = ERR_PRINTING;
		break;
	    }
	    numAnswers++;
	    cp = buf.qb2 + sizeof(dns_hdr_t);
	    if (ntohs(buf.qb1.dh_qdcount) > 0)
		cp += dn_skipname(cp, buf.qb2 + len) + QFIXEDSZ;

	    nmp = cp;
	    cp += dn_skipname(cp, (u_char *)&buf + len);
	    if ((_getshort(cp) == T_SOA)) {
		dn_expand(buf.qb2, buf.qb2 + len, nmp, (u8_t *)dname[soacnt],
			sizeof(dname[0]));
	        if (soacnt) {
		    if (strcmp(dname[0], dname[1]) == 0)
			break;
		} else
		    soacnt++;
	    }
        }

	close(tcp_fd);

	switch (error) {
	    case NO_ERRORS:
		return (SUCCESS);

	    case ERR_READING_LEN:
		return(ERROR);

	    case ERR_PRINTING:
		fprintf(stderr,"*** Error during listing of %s: %s\n", 
				namePtr, DecodeError(result));
		return(result);

	    case ERR_READING_MSG:
		headerPtr = (dns_hdr_t *) &buf;
		fprintf(stderr,"ListHosts: error receiving zone transfer:\n");
		fprintf(stderr,
	       "  result: %s, answers = %d, authority = %d, additional = %d\n", 
		    	resultcodes[headerPtr->dh_flag2 & DHF_RCODE], 
		    	ntohs(headerPtr->dh_ancount), 
			ntohs(headerPtr->dh_nscount), 
			ntohs(headerPtr->dh_arcount));
		return(ERROR);
	    default:
		return(ERROR);
	}
}

static char *
DecodeError(result)
    int result;
{
	switch(result) {
	    case NOERROR: 	return("Success"); break;
	    case FORMERR:	return("Format error"); break;
	    case SERVFAIL:	return("Server failed"); break;
	    case NXDOMAIN:	return("Non-existent domain"); break;
	    case NOTIMP:	return("Not implemented"); break;
	    case REFUSED:	return("Query refused"); break;
	    case NOCHANGE:	return("No change"); break;
	    case NO_INFO: 	return("No information"); break;
	    case ERROR: 	return("Unspecified error"); break;
	    case TIME_OUT: 	return("Timed out"); break;
	    case NONAUTH: 	return("Non-authoritative answer"); break;
	    default: 		break;
	}
	return("BAD ERROR VALUE"); 
}

static int tcpip_writeall(fd, buf, siz)
int fd;
char *buf;
unsigned siz;
{
	unsigned siz_org;
	int nbytes;

	siz_org= siz;

	while (siz)
	{
		nbytes= write(fd, buf, siz);
		if (nbytes == -1)
			return nbytes;
		assert(siz >= nbytes);
		buf += nbytes;
		siz -= nbytes;
	}
	return siz_org;
}