text: /*
   * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
   * Copyright (c) 1996,1999 by Internet Software Consortium.
   *
   * Permission to use, copy, modify, and distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
   * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
   * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
   * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
   */
  
  #ifndef lint
  static const char rcsid[] = "$Id: ns_name.c,v 1.11 2009/01/23 19:59:16 each Exp $";
  #endif
  #include <sys/cdefs.h>
  __FBSDID("$FreeBSD: releng/11.1/lib/libc/nameser/ns_name.c 269873 2014-08-12 13:09:32Z ume $");
  
  #include "port_before.h"
  
  #include <sys/types.h>
  
  #include <netinet/in.h>
  #include <arpa/nameser.h>
  
  #include <errno.h>
  #include <resolv.h>
  #include <string.h>
  #include <ctype.h>
  #include <stdlib.h>
  #include <limits.h>
  
  #include "port_after.h"
  
  #ifdef SPRINTF_CHAR
  # define SPRINTF(x) strlen(sprintf/**/x)
  #else
  # define SPRINTF(x) ((size_t)sprintf x)
  #endif
  
  #define NS_TYPE_ELT			0x40 /*%< EDNS0 extended label type */
  #define DNS_LABELTYPE_BITSTRING		0x41
  
  /* Data. */
  
  static const char	digits[] = "0123456789";
  
  static const char digitvalue[256] = {
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,	/*16*/
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*32*/
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*48*/
  	 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1, /*64*/
  	-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*80*/
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*96*/
  	-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*112*/
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*128*/
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*256*/
  };
  
  /* Forward. */
  
  static int		special(int);
  static int		printable(int);
  static int		dn_find(const u_char *, const u_char *,
  				const u_char * const *,
  				const u_char * const *);
  static int		encode_bitsring(const char **, const char *,
  					unsigned char **, unsigned char **,
  					unsigned const char *);
  static int		labellen(const u_char *);
  static int		decode_bitstring(const unsigned char **,
  					 char *, const char *);
  
  /* Public. */
  
  /*%
   *	Convert an encoded domain name to printable ascii as per RFC1035.
  
   * return:
   *\li	Number of bytes written to buffer, or -1 (with errno set)
   *
   * notes:
   *\li	The root is returned as "."
   *\li	All other domains are returned in non absolute form
   */
  int
  ns_name_ntop(const u_char *src, char *dst, size_t dstsiz)
  {
  	const u_char *cp;
  	char *dn, *eom;
  	u_char c;
  	u_int n;
  	int l;
  
  	cp = src;
  	dn = dst;
  	eom = dst + dstsiz;
  
  	while ((n = *cp++) != 0) {
  		if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
  			/* Some kind of compression pointer. */
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		if (dn != dst) {
  			if (dn >= eom) {
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			*dn++ = '.';
  		}
  		if ((l = labellen(cp - 1)) < 0) {
  			errno = EMSGSIZE; /*%< XXX */
  			return (-1);
  		}
  		if (dn + l >= eom) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		if ((n & NS_CMPRSFLGS) == NS_TYPE_ELT) {
  			int m;
  
  			if (n != DNS_LABELTYPE_BITSTRING) {
  				/* XXX: labellen should reject this case */
  				errno = EINVAL;
  				return (-1);
  			}
  			if ((m = decode_bitstring(&cp, dn, eom)) < 0)
  			{
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			dn += m; 
  			continue;
  		}
  		for ((void)NULL; l > 0; l--) {
  			c = *cp++;
  			if (special(c)) {
  				if (dn + 1 >= eom) {
  					errno = EMSGSIZE;
  					return (-1);
  				}
  				*dn++ = '\\';
  				*dn++ = (char)c;
  			} else if (!printable(c)) {
  				if (dn + 3 >= eom) {
  					errno = EMSGSIZE;
  					return (-1);
  				}
  				*dn++ = '\\';
  				*dn++ = digits[c / 100];
  				*dn++ = digits[(c % 100) / 10];
  				*dn++ = digits[c % 10];
  			} else {
  				if (dn >= eom) {
  					errno = EMSGSIZE;
  					return (-1);
  				}
  				*dn++ = (char)c;
  			}
  		}
  	}
  	if (dn == dst) {
  		if (dn >= eom) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		*dn++ = '.';
  	}
  	if (dn >= eom) {
  		errno = EMSGSIZE;
  		return (-1);
  	}
  	*dn++ = '\0';
  	return (dn - dst);
  }
  
  /*%
   *	Convert a ascii string into an encoded domain name as per RFC1035.
   *
   * return:
   *
   *\li	-1 if it fails
   *\li	1 if string was fully qualified
   *\li	0 is string was not fully qualified
   *
   * notes:
   *\li	Enforces label and domain length limits.
   */
  int
  ns_name_pton(const char *src, u_char *dst, size_t dstsiz) {
  	return (ns_name_pton2(src, dst, dstsiz, NULL));
  }
  
  /*
   * ns_name_pton2(src, dst, dstsiz, *dstlen)
   *	Convert a ascii string into an encoded domain name as per RFC1035.
   * return:
   *	-1 if it fails
   *	1 if string was fully qualified
   *	0 is string was not fully qualified
   * side effects:
   *	fills in *dstlen (if non-NULL)
   * notes:
   *	Enforces label and domain length limits.
   */
  int
  ns_name_pton2(const char *src, u_char *dst, size_t dstsiz, size_t *dstlen) {
  	u_char *label, *bp, *eom;
  	int c, n, escaped, e = 0;
  	char *cp;
  
  	escaped = 0;
  	bp = dst;
  	eom = dst + dstsiz;
  	label = bp++;
  
  	while ((c = *src++) != 0) {
  		if (escaped) {
  			if (c == '[') { /*%< start a bit string label */
  				if ((cp = strchr(src, ']')) == NULL) {
  					errno = EINVAL; /*%< ??? */
  					return (-1);
  				}
  				if ((e = encode_bitsring(&src, cp + 2,
  							 &label, &bp, eom))
  				    != 0) {
  					errno = e;
  					return (-1);
  				}
  				escaped = 0;
  				label = bp++;
  				if ((c = *src++) == 0)
  					goto done;
  				else if (c != '.') {
  					errno = EINVAL;
  					return	(-1);
  				}
  				continue;
  			}
  			else if ((cp = strchr(digits, c)) != NULL) {
  				n = (cp - digits) * 100;
  				if ((c = *src++) == 0 ||
  				    (cp = strchr(digits, c)) == NULL) {
  					errno = EMSGSIZE;
  					return (-1);
  				}
  				n += (cp - digits) * 10;
  				if ((c = *src++) == 0 ||
  				    (cp = strchr(digits, c)) == NULL) {
  					errno = EMSGSIZE;
  					return (-1);
  				}
  				n += (cp - digits);
  				if (n > 255) {
  					errno = EMSGSIZE;
  					return (-1);
  				}
  				c = n;
  			}
  			escaped = 0;
  		} else if (c == '\\') {
  			escaped = 1;
  			continue;
  		} else if (c == '.') {
  			c = (bp - label - 1);
  			if ((c & NS_CMPRSFLGS) != 0) {	/*%< Label too big. */
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			if (label >= eom) {
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			*label = c;
  			/* Fully qualified ? */
  			if (*src == '\0') {
  				if (c != 0) {
  					if (bp >= eom) {
  						errno = EMSGSIZE;
  						return (-1);
  					}
  					*bp++ = '\0';
  				}
  				if ((bp - dst) > MAXCDNAME) {
  					errno = EMSGSIZE;
  					return (-1);
  				}
  				if (dstlen != NULL)
  					*dstlen = (bp - dst);
  				return (1);
  			}
  			if (c == 0 || *src == '.') {
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			label = bp++;
  			continue;
  		}
  		if (bp >= eom) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		*bp++ = (u_char)c;
  	}
  	c = (bp - label - 1);
  	if ((c & NS_CMPRSFLGS) != 0) {		/*%< Label too big. */
  		errno = EMSGSIZE;
  		return (-1);
  	}
    done:
  	if (label >= eom) {
  		errno = EMSGSIZE;
  		return (-1);
  	}
  	*label = c;
  	if (c != 0) {
  		if (bp >= eom) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		*bp++ = 0;
  	}
  	if ((bp - dst) > MAXCDNAME) {	/*%< src too big */
  		errno = EMSGSIZE;
  		return (-1);
  	}
  	if (dstlen != NULL)
  		*dstlen = (bp - dst);
  	return (0);
  }
  
  /*%
   *	Convert a network strings labels into all lowercase.
   *
   * return:
   *\li	Number of bytes written to buffer, or -1 (with errno set)
   *
   * notes:
   *\li	Enforces label and domain length limits.
   */
  
  int
  ns_name_ntol(const u_char *src, u_char *dst, size_t dstsiz)
  {
  	const u_char *cp;
  	u_char *dn, *eom;
  	u_char c;
  	u_int n;
  	int l;
  
  	cp = src;
  	dn = dst;
  	eom = dst + dstsiz;
  
  	if (dn >= eom) {
  		errno = EMSGSIZE;
  		return (-1);
  	}
  	while ((n = *cp++) != 0) {
  		if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
  			/* Some kind of compression pointer. */
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		*dn++ = n;
  		if ((l = labellen(cp - 1)) < 0) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		if (dn + l >= eom) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		for ((void)NULL; l > 0; l--) {
  			c = *cp++;
  			if (isascii(c) && isupper(c))
  				*dn++ = tolower(c);
  			else
  				*dn++ = c;
  		}
  	}
  	*dn++ = '\0';
  	return (dn - dst);
  }
  
  /*%
   *	Unpack a domain name from a message, source may be compressed.
   *
   * return:
   *\li	-1 if it fails, or consumed octets if it succeeds.
   */
  int
  ns_name_unpack(const u_char *msg, const u_char *eom, const u_char *src,
  	       u_char *dst, size_t dstsiz)
  {
  	return (ns_name_unpack2(msg, eom, src, dst, dstsiz, NULL));
  }
  
  /*
   * ns_name_unpack2(msg, eom, src, dst, dstsiz, *dstlen)
   *	Unpack a domain name from a message, source may be compressed.
   * return:
   *	-1 if it fails, or consumed octets if it succeeds.
   * side effect:
   *	fills in *dstlen (if non-NULL).
   */
  int
  ns_name_unpack2(const u_char *msg, const u_char *eom, const u_char *src,
  		u_char *dst, size_t dstsiz, size_t *dstlen)
  {
  	const u_char *srcp, *dstlim;
  	u_char *dstp;
  	int n, len, checked, l;
  
  	len = -1;
  	checked = 0;
  	dstp = dst;
  	srcp = src;
  	dstlim = dst + dstsiz;
  	if (srcp < msg || srcp >= eom) {
  		errno = EMSGSIZE;
  		return (-1);
  	}
  	/* Fetch next label in domain name. */
  	while ((n = *srcp++) != 0) {
  		/* Check for indirection. */
  		switch (n & NS_CMPRSFLGS) {
  		case 0:
  		case NS_TYPE_ELT:
  			/* Limit checks. */
  			if ((l = labellen(srcp - 1)) < 0) {
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			if (dstp + l + 1 >= dstlim || srcp + l >= eom) {
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			checked += l + 1;
  			*dstp++ = n;
  			memcpy(dstp, srcp, l);
  			dstp += l;
  			srcp += l;
  			break;
  
  		case NS_CMPRSFLGS:
  			if (srcp >= eom) {
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			if (len < 0)
  				len = srcp - src + 1;
  			l = ((n & 0x3f) << 8) | (*srcp & 0xff);
  			if (l >= eom - msg) {  /*%< Out of range. */
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			srcp = msg + l;
  			checked += 2;
  			/*
  			 * Check for loops in the compressed name;
  			 * if we've looked at the whole message,
  			 * there must be a loop.
  			 */
  			if (checked >= eom - msg) {
  				errno = EMSGSIZE;
  				return (-1);
  			}
  			break;
  
  		default:
  			errno = EMSGSIZE;
  			return (-1);			/*%< flag error */
  		}
  	}
  	*dstp++ = 0;
  	if (dstlen != NULL)
  		*dstlen = dstp - dst;
  	if (len < 0)
  		len = srcp - src;
  	return (len);
  }
  
  /*%
   *	Pack domain name 'domain' into 'comp_dn'.
   *
   * return:
   *\li	Size of the compressed name, or -1.
   *
   * notes:
   *\li	'dnptrs' is an array of pointers to previous compressed names.
   *\li	dnptrs[0] is a pointer to the beginning of the message. The array
   *	ends with NULL.
   *\li	'lastdnptr' is a pointer to the end of the array pointed to
   *	by 'dnptrs'.
   *
   * Side effects:
   *\li	The list of pointers in dnptrs is updated for labels inserted into
   *	the message as we compress the name.  If 'dnptr' is NULL, we don't
   *	try to compress names. If 'lastdnptr' is NULL, we don't update the
   *	list.
   */
  int
  ns_name_pack(const u_char *src, u_char *dst, int dstsiz,
  	     const u_char **dnptrs, const u_char **lastdnptr)
  {
  	u_char *dstp;
  	const u_char **cpp, **lpp, *eob, *msg;
  	const u_char *srcp;
  	int n, l, first = 1;
  
  	srcp = src;
  	dstp = dst;
  	eob = dstp + dstsiz;
  	lpp = cpp = NULL;
  	if (dnptrs != NULL) {
  		if ((msg = *dnptrs++) != NULL) {
  			for (cpp = dnptrs; *cpp != NULL; cpp++)
  				(void)NULL;
  			lpp = cpp;	/*%< end of list to search */
  		}
  	} else
  		msg = NULL;
  
  	/* make sure the domain we are about to add is legal */
  	l = 0;
  	do {
  		int l0;
  
  		n = *srcp;
  		if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		if ((l0 = labellen(srcp)) < 0) {
  			errno = EINVAL;
  			return (-1);
  		}
  		l += l0 + 1;
  		if (l > MAXCDNAME) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		srcp += l0 + 1;
  	} while (n != 0);
  
  	/* from here on we need to reset compression pointer array on error */
  	srcp = src;
  	do {
  		/* Look to see if we can use pointers. */
  		n = *srcp;
  		if (n != 0 && msg != NULL) {
  			l = dn_find(srcp, msg, (const u_char * const *)dnptrs,
  				    (const u_char * const *)lpp);
  			if (l >= 0) {
  				if (dstp + 1 >= eob) {
  					goto cleanup;
  				}
  				*dstp++ = (l >> 8) | NS_CMPRSFLGS;
  				*dstp++ = l % 256;
  				return (dstp - dst);
  			}
  			/* Not found, save it. */
  			if (lastdnptr != NULL && cpp < lastdnptr - 1 &&
  			    (dstp - msg) < 0x4000 && first) {
  				*cpp++ = dstp;
  				*cpp = NULL;
  				first = 0;
  			}
  		}
  		/* copy label to buffer */
  		if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
  			/* Should not happen. */
  			goto cleanup;
  		}
  		n = labellen(srcp);
  		if (dstp + 1 + n >= eob) {
  			goto cleanup;
  		}
  		memcpy(dstp, srcp, n + 1);
  		srcp += n + 1;
  		dstp += n + 1;
  	} while (n != 0);
  
  	if (dstp > eob) {
  cleanup:
  		if (msg != NULL)
  			*lpp = NULL;
  		errno = EMSGSIZE;
  		return (-1);
  	} 
  	return (dstp - dst);
  }
  
  /*%
   *	Expand compressed domain name to presentation format.
   *
   * return:
   *\li	Number of bytes read out of `src', or -1 (with errno set).
   *
   * note:
   *\li	Root domain returns as "." not "".
   */
  int
  ns_name_uncompress(const u_char *msg, const u_char *eom, const u_char *src,
  		   char *dst, size_t dstsiz)
  {
  	u_char tmp[NS_MAXCDNAME];
  	int n;
  	
  	if ((n = ns_name_unpack(msg, eom, src, tmp, sizeof tmp)) == -1)
  		return (-1);
  	if (ns_name_ntop(tmp, dst, dstsiz) == -1)
  		return (-1);
  	return (n);
  }
  
  /*%
   *	Compress a domain name into wire format, using compression pointers.
   *
   * return:
   *\li	Number of bytes consumed in `dst' or -1 (with errno set).
   *
   * notes:
   *\li	'dnptrs' is an array of pointers to previous compressed names.
   *\li	dnptrs[0] is a pointer to the beginning of the message.
   *\li	The list ends with NULL.  'lastdnptr' is a pointer to the end of the
   *	array pointed to by 'dnptrs'. Side effect is to update the list of
   *	pointers for labels inserted into the message as we compress the name.
   *\li	If 'dnptr' is NULL, we don't try to compress names. If 'lastdnptr'
   *	is NULL, we don't update the list.
   */
  int
  ns_name_compress(const char *src, u_char *dst, size_t dstsiz,
  		 const u_char **dnptrs, const u_char **lastdnptr)
  {
  	u_char tmp[NS_MAXCDNAME];
  
  	if (ns_name_pton(src, tmp, sizeof tmp) == -1)
  		return (-1);
  	return (ns_name_pack(tmp, dst, dstsiz, dnptrs, lastdnptr));
  }
  
  /*%
   * Reset dnptrs so that there are no active references to pointers at or
   * after src.
   */
  void
  ns_name_rollback(const u_char *src, const u_char **dnptrs,
  		 const u_char **lastdnptr)
  {
  	while (dnptrs < lastdnptr && *dnptrs != NULL) {
  		if (*dnptrs >= src) {
  			*dnptrs = NULL;
  			break;
  		}
  		dnptrs++;
  	}
  }
  
  /*%
   *	Advance *ptrptr to skip over the compressed name it points at.
   *
   * return:
   *\li	0 on success, -1 (with errno set) on failure.
   */
  int
  ns_name_skip(const u_char **ptrptr, const u_char *eom)
  {
  	const u_char *cp;
  	u_int n;
  	int l;
  
  	cp = *ptrptr;
  	while (cp < eom && (n = *cp++) != 0) {
  		/* Check for indirection. */
  		switch (n & NS_CMPRSFLGS) {
  		case 0:			/*%< normal case, n == len */
  			cp += n;
  			continue;
  		case NS_TYPE_ELT: /*%< EDNS0 extended label */
  			if ((l = labellen(cp - 1)) < 0) {
  				errno = EMSGSIZE; /*%< XXX */
  				return (-1);
  			}
  			cp += l;
  			continue;
  		case NS_CMPRSFLGS:	/*%< indirection */
  			cp++;
  			break;
  		default:		/*%< illegal type */
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		break;
  	}
  	if (cp > eom) {
  		errno = EMSGSIZE;
  		return (-1);
  	}
  	*ptrptr = cp;
  	return (0);
  }
  
  /* Find the number of octets an nname takes up, including the root label.
   * (This is basically ns_name_skip() without compression-pointer support.)
   * ((NOTE: can only return zero if passed-in namesiz argument is zero.))
   */
  ssize_t
  ns_name_length(ns_nname_ct nname, size_t namesiz) {
  	ns_nname_ct orig = nname;
  	u_int n;
  
  	while (namesiz-- > 0 && (n = *nname++) != 0) {
  		if ((n & NS_CMPRSFLGS) != 0) {
  			errno = EISDIR;
  			return (-1);
  		}
  		if (n > namesiz) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		nname += n;
  		namesiz -= n;
  	}
  	return (nname - orig);
  }
  
  /* Compare two nname's for equality.  Return -1 on error (setting errno).
   */
  int
  ns_name_eq(ns_nname_ct a, size_t as, ns_nname_ct b, size_t bs) {
  	ns_nname_ct ae = a + as, be = b + bs;
  	int ac, bc;
  
  	while (ac = *a, bc = *b, ac != 0 && bc != 0) {
  		if ((ac & NS_CMPRSFLGS) != 0 || (bc & NS_CMPRSFLGS) != 0) {
  			errno = EISDIR;
  			return (-1);
  		}
  		if (a + ac >= ae || b + bc >= be) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		if (ac != bc || strncasecmp((const char *) ++a,
  					    (const char *) ++b, ac) != 0)
  			return (0);
  		a += ac, b += bc;
  	}
  	return (ac == 0 && bc == 0);
  }
  
  /* Is domain "A" owned by (at or below) domain "B"?
   */
  int
  ns_name_owned(ns_namemap_ct a, int an, ns_namemap_ct b, int bn) {
  	/* If A is shorter, it cannot be owned by B. */
  	if (an < bn)
  		return (0);
  
  	/* If they are unequal before the length of the shorter, A cannot... */
  	while (bn > 0) {
  		if (a->len != b->len ||
  		    strncasecmp((const char *) a->base,
  				(const char *) b->base, a->len) != 0)
  			return (0);
  		a++, an--;
  		b++, bn--;
  	}
  
  	/* A might be longer or not, but either way, B owns it. */
  	return (1);
  }
  
  /* Build an array of <base,len> tuples from an nname, top-down order.
   * Return the number of tuples (labels) thus discovered.
   */
  int
  ns_name_map(ns_nname_ct nname, size_t namelen, ns_namemap_t map, int mapsize) {
  	u_int n;
  	int l;
  
  	n = *nname++;
  	namelen--;
  
  	/* Root zone? */
  	if (n == 0) {
  		/* Extra data follows name? */
  		if (namelen > 0) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		return (0);
  	}
  
  	/* Compression pointer? */
  	if ((n & NS_CMPRSFLGS) != 0) {
  		errno = EISDIR;
  		return (-1);
  	}
  
  	/* Label too long? */
  	if (n > namelen) {
  		errno = EMSGSIZE;
  		return (-1);
  	}
  
  	/* Recurse to get rest of name done first. */
  	l = ns_name_map(nname + n, namelen - n, map, mapsize);
  	if (l < 0)
  		return (-1);
  
  	/* Too many labels? */
  	if (l >= mapsize) {
  		errno = ENAMETOOLONG;
  		return (-1);
  	}
  
  	/* We're on our way back up-stack, store current map data. */
  	map[l].base = nname;
  	map[l].len = n;
  	return (l + 1);
  }
  
  /* Count the labels in a domain name.  Root counts, so COM. has two.  This
   * is to make the result comparable to the result of ns_name_map().
   */
  int
  ns_name_labels(ns_nname_ct nname, size_t namesiz) {
  	int ret = 0;
  	u_int n;
  
  	while (namesiz-- > 0 && (n = *nname++) != 0) {
  		if ((n & NS_CMPRSFLGS) != 0) {
  			errno = EISDIR;
  			return (-1);
  		}
  		if (n > namesiz) {
  			errno = EMSGSIZE;
  			return (-1);
  		}
  		nname += n;
  		namesiz -= n;
  		ret++;
  	}
  	return (ret + 1);
  }
  
  /* Private. */
  
  /*%
   *	Thinking in noninternationalized USASCII (per the DNS spec),
   *	is this characted special ("in need of quoting") ?
   *
   * return:
   *\li	boolean.
   */
  static int
  special(int ch) {
  	switch (ch) {
  	case 0x22: /*%< '"' */
  	case 0x2E: /*%< '.' */
  	case 0x3B: /*%< ';' */
  	case 0x5C: /*%< '\\' */
  	case 0x28: /*%< '(' */
  	case 0x29: /*%< ')' */
  	/* Special modifiers in zone files. */
  	case 0x40: /*%< '@' */
  	case 0x24: /*%< '$' */
  		return (1);
  	default:
  		return (0);
  	}
  }
  
  /*%
   *	Thinking in noninternationalized USASCII (per the DNS spec),
   *	is this character visible and not a space when printed ?
   *
   * return:
   *\li	boolean.
   */
  static int
  printable(int ch) {
  	return (ch > 0x20 && ch < 0x7f);
  }
  
  /*%
   *	Thinking in noninternationalized USASCII (per the DNS spec),
   *	convert this character to lower case if it's upper case.
   */
  static int
  mklower(int ch) {
  	if (ch >= 0x41 && ch <= 0x5A)
  		return (ch + 0x20);
  	return (ch);
  }
  
  /*%
   *	Search for the counted-label name in an array of compressed names.
   *
   * return:
   *\li	offset from msg if found, or -1.
   *
   * notes:
   *\li	dnptrs is the pointer to the first name on the list,
   *\li	not the pointer to the start of the message.
   */
  static int
  dn_find(const u_char *domain, const u_char *msg,
  	const u_char * const *dnptrs,
  	const u_char * const *lastdnptr)
  {
  	const u_char *dn, *cp, *sp;
  	const u_char * const *cpp;
  	u_int n;
  
  	for (cpp = dnptrs; cpp < lastdnptr; cpp++) {
  		sp = *cpp;
  		/*
  		 * terminate search on:
  		 * root label
  		 * compression pointer
  		 * unusable offset
  		 */
  		while (*sp != 0 && (*sp & NS_CMPRSFLGS) == 0 &&
  		       (sp - msg) < 0x4000) {
  			dn = domain;
  			cp = sp;
  			while ((n = *cp++) != 0) {
  				/*
  				 * check for indirection
  				 */
  				switch (n & NS_CMPRSFLGS) {
  				case 0:		/*%< normal case, n == len */
  					n = labellen(cp - 1); /*%< XXX */
  					if (n != *dn++)
  						goto next;
  
  					for ((void)NULL; n > 0; n--)
  						if (mklower(*dn++) !=
  						    mklower(*cp++))
  							goto next;
  					/* Is next root for both ? */
  					if (*dn == '\0' && *cp == '\0')
  						return (sp - msg);
  					if (*dn)
  						continue;
  					goto next;
  				case NS_CMPRSFLGS:	/*%< indirection */
  					cp = msg + (((n & 0x3f) << 8) | *cp);
  					break;
  
  				default:	/*%< illegal type */
  					errno = EMSGSIZE;
  					return (-1);
  				}
  			}
   next: ;
  			sp += *sp + 1;
  		}
  	}
  	errno = ENOENT;
  	return (-1);
  }
  
  static int
  decode_bitstring(const unsigned char **cpp, char *dn, const char *eom)
  {
  	const unsigned char *cp = *cpp;
  	char *beg = dn, tc;
  	int b, blen, plen, i;
  
  	if ((blen = (*cp & 0xff)) == 0)
  		blen = 256;
  	plen = (blen + 3) / 4;
  	plen += sizeof("\\[x/]") + (blen > 99 ? 3 : (blen > 9) ? 2 : 1);
  	if (dn + plen >= eom)
  		return (-1);
  
  	cp++;
  	i = SPRINTF((dn, "\\[x"));
  	if (i < 0)
  		return (-1);
  	dn += i;
  	for (b = blen; b > 7; b -= 8, cp++) {
  		i = SPRINTF((dn, "%02x", *cp & 0xff));
  		if (i < 0)
  			return (-1);
  		dn += i;
  	}
  	if (b > 4) {
  		tc = *cp++;
  		i = SPRINTF((dn, "%02x", tc & (0xff << (8 - b))));
  		if (i < 0)
  			return (-1);
  		dn += i;
  	} else if (b > 0) {
  		tc = *cp++;
  		i = SPRINTF((dn, "%1x",
  			       ((tc >> 4) & 0x0f) & (0x0f << (4 - b)))); 
  		if (i < 0)
  			return (-1);
  		dn += i;
  	}
  	i = SPRINTF((dn, "/%d]", blen));
  	if (i < 0)
  		return (-1);
  	dn += i;
  
  	*cpp = cp;
  	return (dn - beg);
  }
  
  static int
  encode_bitsring(const char **bp, const char *end, unsigned char **labelp,
  		unsigned char ** dst, unsigned const char *eom)
  {
  	int afterslash = 0;
  	const char *cp = *bp;
  	unsigned char *tp;
  	char c;
  	const char *beg_blen;
  	char *end_blen = NULL;
  	int value = 0, count = 0, tbcount = 0, blen = 0;
  
  	beg_blen = end_blen = NULL;
  
  	/* a bitstring must contain at least 2 characters */
  	if (end - cp < 2)
  		return (EINVAL);
  
  	/* XXX: currently, only hex strings are supported */
  	if (*cp++ != 'x')
  		return (EINVAL);
  	if (!isxdigit((*cp) & 0xff)) /*%< reject '\[x/BLEN]' */
  		return (EINVAL);
  
  	for (tp = *dst + 1; cp < end && tp < eom; cp++) {
  		switch((c = *cp)) {
  		case ']':	/*%< end of the bitstring */
  			if (afterslash) {
  				if (beg_blen == NULL)
  					return (EINVAL);
  				blen = (int)strtol(beg_blen, &end_blen, 10);
  				if (*end_blen != ']')
  					return (EINVAL);
  			}
  			if (count)
  				*tp++ = ((value << 4) & 0xff);
  			cp++;	/*%< skip ']' */
  			goto done;
  		case '/':
  			afterslash = 1;
  			break;
  		default:
  			if (afterslash) {
  				if (!isdigit(c&0xff))
  					return (EINVAL);
  				if (beg_blen == NULL) {
  					
  					if (c == '0') {
  						/* blen never begings with 0 */
  						return (EINVAL);
  					}
  					beg_blen = cp;
  				}
  			} else {
  				if (!isxdigit(c&0xff))
  					return (EINVAL);
  				value <<= 4;
  				value += digitvalue[(int)c];
  				count += 4;
  				tbcount += 4;
  				if (tbcount > 256)
  					return (EINVAL);
  				if (count == 8) {
  					*tp++ = value;
  					count = 0;
  				}
  			}
  			break;
  		}
  	}
    done:
  	if (cp >= end || tp >= eom)
  		return (EMSGSIZE);
  
  	/*
  	 * bit length validation:
  	 * If a <length> is present, the number of digits in the <bit-data>
  	 * MUST be just sufficient to contain the number of bits specified
  	 * by the <length>. If there are insignificant bits in a final
  	 * hexadecimal or octal digit, they MUST be zero.
  	 * RFC2673, Section 3.2.
  	 */
  	if (blen > 0) {
  		int traillen;
  
  		if (((blen + 3) & ~3) != tbcount)
  			return (EINVAL);
  		traillen = tbcount - blen; /*%< between 0 and 3 */
  		if (((value << (8 - traillen)) & 0xff) != 0)
  			return (EINVAL);
  	}
  	else
  		blen = tbcount;
  	if (blen == 256)
  		blen = 0;
  
  	/* encode the type and the significant bit fields */
  	**labelp = DNS_LABELTYPE_BITSTRING;
  	**dst = blen;
  
  	*bp = cp;
  	*dst = tp;
  
  	return (0);
  }
  
  static int
  labellen(const u_char *lp)
  {
  	int bitlen;
  	u_char l = *lp;
  
  	if ((l & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
  		/* should be avoided by the caller */
  		return (-1);
  	}
  
  	if ((l & NS_CMPRSFLGS) == NS_TYPE_ELT) {
  		if (l == DNS_LABELTYPE_BITSTRING) {
  			if ((bitlen = *(lp + 1)) == 0)
  				bitlen = 256;
  			return ((bitlen + 7 ) / 8 + 1);
  		}
  		return (-1);	/*%< unknwon ELT */
  	}
  	return (l);
  }
  
  /*! \file */
  