/* 
 * Copyright (c) 1985, 1993
 *    The Regents of the University of California.  All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/* 
 * Portions Copyright (c) 1993 by Digital Equipment Corporation.
 * 
 * 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, and that
 * the name of Digital Equipment Corporation not be used in advertising or
 * publicity pertaining to distribution of the document or software without
 * specific, written prior permission.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
 * CORPORATION 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.
 */

/* 
 * Portions 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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM 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.
 */

/* Original copyright ISC as above. Code modified specifically for ircd use from the following
 * orginal files in bind ... res_comp.c ns_name.c ns_netint.c res_init.c - Dianora */

#include "dns.h"

#ifdef _WIN32
#define EMSGSIZE	WSAEMSGSIZE
#endif

#define MOWGLI_DNS_NS_TYPE_ELT		0x40	/* EDNS0 extended label type */
#define MOWGLI_DNS_LABELTYPE_BITSTRING	0x41

/* from Hybrid Id: reslib.c 177 2005-10-22 09:05:05Z michael $ */

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 */
};

static const char digits[] = "0123456789";

static int labellen(const unsigned char *lp);
static bool mowgli_dns_is_special(int ch);
static bool mowgli_dns_is_printable(int ch);
static int mowgli_dns_decode_bitstring(const char **cpp, char *dn, const char *eom);
static int mowgli_dns_ns_name_compress(const char *src, unsigned char *dst, size_t dstsiz, unsigned char **dnptrs, unsigned char **lastdnptr);
static int mowgli_dns_dn_find(const unsigned char *, const unsigned char *, const unsigned char *const *, const unsigned char *const *);
static int mowgli_dns_encode_bitsring(const char **, const char *, unsigned char **, unsigned char **, const char *);
static int mowgli_dns_ns_name_uncompress(const unsigned char *, const unsigned char *, const unsigned char *, char *, size_t);
static int mowgli_dns_ns_name_unpack(const unsigned char *, const unsigned char *, const unsigned char *, unsigned char *, size_t);
static int mowgli_dns_ns_name_ntop(const char *, char *, size_t);
static int mowgli_dns_ns_name_skip(const unsigned char **, const unsigned char *);
static int mowgli_dns_mklower(int ch);

/*
 * Expand compressed domain name 'comp_dn' to full domain name.
 * 'rmsg' is a pointer to the begining of the message,
 * 'eomorig' points to the first location after the message,
 * 'exp_dn' is a pointer to a buffer of size 'length' for the result.
 * Return size of compressed name or -1 if there was an error.
 */
int
mowgli_dns_dn_expand(const unsigned char *rmsg, const unsigned char *eom,
			  const unsigned char *src, char *dst, int dstsiz)
{
	int n = mowgli_dns_ns_name_uncompress(rmsg, eom, src, dst, (size_t) dstsiz);

	if (n > 0 && dst[0] == '.')
		dst[0] = '\0';
	return n;
}

/* 
 * mowgli_dns_ns_name_uncompress(rmsg, eom, src, dst, dstsiz)
 *  Expand compressed domain name to presentation format.
 * return:
 *  Number of bytes read out of `src', or -1 (with errno set).
 * note:
 *  Root domain returns as "." not "".
 */
static int
mowgli_dns_ns_name_uncompress(const unsigned char *rmsg, const unsigned char *eom,
					   const unsigned char *src, char *dst, size_t dstsiz)
{
	unsigned char tmp[MOWGLI_DNS_NS_MAXCDNAME];
	int n;

	if ((n = mowgli_dns_ns_name_unpack(rmsg, eom, src, tmp, sizeof tmp)) == -1)
		return -1;
	if (mowgli_dns_ns_name_ntop((char *)tmp, dst, dstsiz) == -1)
		return -1;
	return n;
}

/* 
 * mowgli_dns_ns_name_unpack(rmsg, eom, src, dst, dstsiz)
 *  Unpack a domain name from a message, source may be compressed.
 * return:
 *  -1 if it fails, or consumed octets if it succeeds.
 */
static int
mowgli_dns_ns_name_unpack(const unsigned char *rmsg, const unsigned char *eom, const unsigned char *src, unsigned char *dst, size_t dstsiz)
{
	const unsigned char *srcp, *dstlim;
	unsigned char *dstp;
	int n, len, checked, l;

	len = -1;
	checked = 0;
	dstp = dst;
	srcp = src;
	dstlim = dst + dstsiz;
	if (srcp < rmsg || srcp >= eom)
	{
		errno = EMSGSIZE;
		return -1;
	}
	/* Fetch next label in domain name. */
	while ((n = *srcp++) != 0)
	{
		/* Check for indirection. */
		switch (n & MOWGLI_DNS_NS_CMPRSFLAGS)
		{
		case 0:
		case MOWGLI_DNS_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 MOWGLI_DNS_NS_CMPRSFLAGS:
			if (srcp >= eom)
			{
				errno = EMSGSIZE;
				return -1;
			}
			if (len < 0)
				len = srcp - src + 1;
			srcp = rmsg + (((n & 0x3f) << 8) | (*srcp & 0xff));
			if (srcp < rmsg || srcp >= eom)
			{					/* Out of range. */
				errno = EMSGSIZE;
				return -1;
			}
			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 - rmsg)
			{
				errno = EMSGSIZE;
				return -1;
			}
			break;

		default:
			errno = EMSGSIZE;
			return -1;		/* flag error */
		}
	}
	*dstp = '\0';
	if (len < 0)
		len = srcp - src;
	return len;
}

/* 
 * mowgli_dns_ns_name_ntop(src, dst, dstsiz)
 *  Convert an encoded domain name to mowgli_dns_is_printable ascii as per RFC1035.
 * return:
 *  Number of bytes written to buffer, or -1 (with errno set)
 * notes:
 *  The root is returned as "."
 *  All other domains are returned in non absolute form
 */
static int mowgli_dns_ns_name_ntop(const char *src, char *dst, size_t dstsiz)
{
	const char *cp;
	char *dn, *eom;
	unsigned char c;
	unsigned int n;
	int l;

	cp = src;
	dn = dst;
	eom = dst + dstsiz;

	while ((n = *cp++) != 0)
	{
		if ((n & MOWGLI_DNS_NS_CMPRSFLAGS) == MOWGLI_DNS_NS_CMPRSFLAGS)
		{
			/* Some kind of compression pointer. */
			errno = EMSGSIZE;
			return -1;
		}
		if (dn != dst)
		{
			if (dn >= eom)
			{
				errno = EMSGSIZE;
				return -1;
			}
			*dn++ = '.';
		}
		if ((l = labellen((const unsigned char *)(cp - 1))) < 0)
		{
			errno = EMSGSIZE;	/* XXX */
			return -1;
		}
		if (dn + l >= eom)
		{
			errno = EMSGSIZE;
			return -1;
		}
		if ((n & MOWGLI_DNS_NS_CMPRSFLAGS) == MOWGLI_DNS_NS_TYPE_ELT)
		{
			int m;

			if (n != MOWGLI_DNS_LABELTYPE_BITSTRING)
			{
				/* XXX: labellen should reject this case */
				errno = EINVAL;
				return -1;
			}
			if ((m = mowgli_dns_decode_bitstring(&cp, dn, eom)) < 0)
			{
				errno = EMSGSIZE;
				return -1;
			}
			dn += m;
			continue;
		}
		for ((void)NULL; l > 0; l--)
		{
			c = *cp++;
			if (mowgli_dns_is_special(c))
			{
				if (dn + 1 >= eom)
				{
					errno = EMSGSIZE;
					return -1;
				}
				*dn++ = '\\';
				*dn++ = (char)c;
			}
			else if (!mowgli_dns_is_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;
}

/* 
 * Pack domain name 'exp_dn' in presentation form into 'comp_dn'.
 * Return the size of the compressed name or -1.
 * 'length' is the size of the array pointed to by 'comp_dn'.
 */
static int
mowgli_dns_dn_comp(const char *src, unsigned char *dst, int dstsiz,
			unsigned char **dnptrs, unsigned char **lastdnptr)
{
	return mowgli_dns_ns_name_compress(src, dst, (size_t) dstsiz, dnptrs, lastdnptr);
}

/* 
 * Skip over a compressed domain name. Return the size or -1.
 */
int mowgli_dns_dn_skipname(const unsigned char *ptr, const unsigned char *eom)
{
	const unsigned char *saveptr = ptr;

	if (mowgli_dns_ns_name_skip(&ptr, eom) == -1)
		return -1;
	return ptr - saveptr;
}

/* 
 * ns_name_skip(ptrptr, eom)
 *  Advance *ptrptr to skip over the compressed name it points at.
 * return:
 *  0 on success, -1 (with errno set) on failure.
 */
static int mowgli_dns_ns_name_skip(const unsigned char **ptrptr, const unsigned char *eom)
{
	const unsigned char *cp;
	unsigned int n;
	int l;

	cp = *ptrptr;

	while (cp < eom && (n = *cp++) != 0)
	{
		/* Check for indirection. */
		switch (n & MOWGLI_DNS_NS_CMPRSFLAGS)
		{
		case 0:				/* normal case, n == len */
			cp += n;
			continue;
		case MOWGLI_DNS_NS_TYPE_ELT:		/* EDNS0 extended label */
			if ((l = labellen(cp - 1)) < 0)
			{
				errno = EMSGSIZE;	/* XXX */
				return -1;
			}

			cp += l;
			continue;
		case MOWGLI_DNS_NS_CMPRSFLAGS:		/* indirection */
			cp++;
			break;
		default:				/* illegal type */
			errno = EMSGSIZE;
			return -1;
		}

		break;
	}

	if (cp > eom)
	{
		errno = EMSGSIZE;
		return -1;
	}

	*ptrptr = cp;
	return 0;
}

unsigned int mowgli_dns_ns_get16(const unsigned char *src)
{
	unsigned int dst;

	MOWGLI_DNS_NS_GET16(dst, src);
	return dst;
}

unsigned long mowgli_dns_ns_get32(const unsigned char *src)
{
	unsigned long dst;

	MOWGLI_DNS_NS_GET32(dst, src);
	return dst;
}

void mowgli_dns_ns_put16(unsigned int src, unsigned char *dst)
{
	MOWGLI_DNS_NS_PUT16(src, dst);
}

void mowgli_dns_ns_put32(unsigned long src, unsigned char *dst)
{
	MOWGLI_DNS_NS_PUT32(src, dst);
}

/* From ns_name.c */

/* 
 * mowgli_dns_is_special(ch)
 *      Thinking in noninternationalized USASCII (per the DNS spec),
 *      is this characted mowgli_dns_is_special ("in need of quoting") ?
 * return:
 *      boolean.
 */
static bool mowgli_dns_is_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 true;
	default:
		return false;
	}
}

static int labellen(const unsigned char *lp)
{
	int bitlen;
	unsigned char l = *lp;

	if ((l & MOWGLI_DNS_NS_CMPRSFLAGS) == MOWGLI_DNS_NS_CMPRSFLAGS)
		/* should be avoided by the caller */
		return -1;

	if ((l & MOWGLI_DNS_NS_CMPRSFLAGS) == MOWGLI_DNS_NS_TYPE_ELT)
	{
		if (l == MOWGLI_DNS_LABELTYPE_BITSTRING)
		{
			if ((bitlen = *(lp + 1)) == 0)
				bitlen = 256;

			return (bitlen + 7) / 8 + 1;
		}

		return -1;			/* unknwon ELT */
	}

	return l;
}


/* 
 * mowgli_dns_is_printable(ch)
 *      Thinking in noninternationalized USASCII (per the DNS spec),
 *      is this character visible and not a space when printed ?
 * return:
 *      boolean.
 */
static bool mowgli_dns_is_printable(int ch)
{
	return (ch > 0x20 && ch < 0x7f) ? true : false;
}

static int mowgli_dns_decode_bitstring(const char **cpp, char *dn, const char *eom)
{
	const char *cp = *cpp;
	char *beg = dn, tc;
	int b, blen, plen;

	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++;
	dn += sprintf(dn, "\\[x");
	for (b = blen; b > 7; b -= 8, cp++)
		dn += sprintf(dn, "%02x", *cp & 0xff);
	if (b > 4)
	{
		tc = *cp++;
		dn += sprintf(dn, "%02x", tc & (0xff << (8 - b)));
	}
	else if (b > 0)
	{
		tc = *cp++;
		dn += sprintf(dn, "%1x", ((tc >> 4) & 0x0f) & (0x0f << (4 - b)));
	}
	dn += sprintf(dn, "/%d]", blen);

	*cpp = cp;
	return (dn - beg);
}

/* 
 * mowgli_dns_ns_name_pton(src, dst, dstsiz)
 *  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
 * notes:
 *  Enforces label and domain length limits.
 */
static int mowgli_dns_ns_name_pton(const char *src, unsigned char *dst, size_t dstsiz)
{
	unsigned char *label, *bp, *eom;
	char *cp;
	int c, n, escaped, e = 0;

	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 = mowgli_dns_encode_bitsring(&src, cp + 2, &label, &bp, (const char *)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 & MOWGLI_DNS_NS_CMPRSFLAGS) != 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) > MOWGLI_DNS_NS_MAXCDNAME)
				{
					errno = EMSGSIZE;
					return -1;
				}
				return (1);
			}
			if (c == 0 || *src == '.')
			{
				errno = EMSGSIZE;
				return -1;
			}
			label = bp++;
			continue;
		}
		if (bp >= eom)
		{
			errno = EMSGSIZE;
			return -1;
		}
		*bp++ = (unsigned char)c;
	}
	c = (bp - label - 1);
	if ((c & MOWGLI_DNS_NS_CMPRSFLAGS) != 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) > MOWGLI_DNS_NS_MAXCDNAME)
	{							/* src too big */
		errno = EMSGSIZE;
		return -1;
	}

	return 0;
}

/* 
 * mowgli_dns_ns_name_pack(src, dst, dstsiz, dnptrs, lastdnptr)
 *  Pack domain name 'domain' into 'comp_dn'.
 * return:
 *  Size of the compressed name, or -1.
 * notes:
 *  'dnptrs' is an array of pointers to previous compressed names.
 *  dnptrs[0] is a pointer to the beginning of the message. The array
 *  ends with NULL.
 *  'lastdnptr' is a pointer to the end of the array pointed to
 *  by 'dnptrs'.
 * Side effects:
 *  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.
 */
static int
mowgli_dns_ns_name_pack(const unsigned char *src, unsigned char *dst, int dstsiz,
				 unsigned char **dnptrs, unsigned char **lastdnptr)
{
	unsigned char *dstp;
	unsigned char **cpp, **lpp;
	const unsigned char *eob, *rmsg;
	const unsigned char *srcp;
	int n, l, first = 1;

	srcp = src;
	dstp = dst;
	eob = dstp + dstsiz;
	lpp = cpp = NULL;
	if (dnptrs != NULL)
	{
		if ((rmsg = *dnptrs++) != NULL)
		{
			for (cpp = dnptrs; *cpp != NULL; cpp++)
				(void)NULL;
			lpp = cpp;			/* end of list to search */
		}
	}
	else
		rmsg = NULL;

	/* make sure the domain we are about to add is legal */
	l = 0;
	do
	{
		int l0;

		n = *srcp;
		if ((n & MOWGLI_DNS_NS_CMPRSFLAGS) == MOWGLI_DNS_NS_CMPRSFLAGS)
		{
			errno = EMSGSIZE;
			return -1;
		}
		if ((l0 = labellen(srcp)) < 0)
		{
			errno = EINVAL;
			return -1;
		}
		l += l0 + 1;
		if (l > MOWGLI_DNS_NS_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 && rmsg != NULL)
		{
			l = mowgli_dns_dn_find(srcp, rmsg, (const unsigned char *const *)dnptrs,
							(const unsigned char *const *)lpp);
			if (l >= 0)
			{
				if (dstp + 1 >= eob)
				{
					goto cleanup;
				}
				*dstp++ = (l >> 8) | MOWGLI_DNS_NS_CMPRSFLAGS;
				*dstp++ = l % 256;
				return (dstp - dst);
			}
			/* Not found, save it. */
			if (lastdnptr != NULL && cpp < lastdnptr - 1 && (dstp - rmsg) < 0x4000 && first)
			{
				*cpp++ = dstp;
				*cpp = NULL;
				first = 0;
			}
		}
		/* copy label to buffer */
		if ((n & MOWGLI_DNS_NS_CMPRSFLAGS) == MOWGLI_DNS_NS_CMPRSFLAGS)
		{
			/* 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 (rmsg != NULL)
			*lpp = NULL;
		errno = EMSGSIZE;
		return -1;
	}
	return (dstp - dst);
}

static int
mowgli_dns_ns_name_compress(const char *src, unsigned char *dst, size_t dstsiz,
					 unsigned char **dnptrs, unsigned char **lastdnptr)
{
	unsigned char tmp[MOWGLI_DNS_NS_MAXCDNAME];

	if (mowgli_dns_ns_name_pton(src, tmp, sizeof tmp) == -1)
		return -1;
	return (mowgli_dns_ns_name_pack(tmp, dst, dstsiz, dnptrs, lastdnptr));
}

static int
mowgli_dns_encode_bitsring(const char **bp, const char *end, unsigned char **labelp,
					unsigned char **dst, const char *eom)
{
	int afterslash = 0;
	const char *cp = *bp;
	char *tp, 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 = (char *)(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.
	 * RFC 2673, 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 = MOWGLI_DNS_LABELTYPE_BITSTRING;
	**dst = blen;

	*bp = cp;
	*dst = (unsigned char *)tp;

	return 0;
}

/* 
 * dn_find(domain, rmsg, dnptrs, lastdnptr)
 *  Search for the counted-label name in an array of compressed names.
 * return:
 *  offset from rmsg if found, or -1.
 * notes:
 *  dnptrs is the pointer to the first name on the list,
 *  not the pointer to the start of the message.
 */
static int
mowgli_dns_dn_find(const unsigned char *domain, const unsigned char *rmsg,
			const unsigned char *const *dnptrs, const unsigned char *const *lastdnptr)
{
	const unsigned char *dn, *cp, *sp;
	const unsigned char *const *cpp;
	unsigned int n;

	for (cpp = dnptrs; cpp < lastdnptr; cpp++)
	{
		sp = *cpp;
		/* 
		 * terminate search on:
		 * root label
		 * compression pointer
		 * unusable offset
		 */
		while (*sp != 0 && (*sp & MOWGLI_DNS_NS_CMPRSFLAGS) == 0 && (sp - rmsg) < 0x4000)
		{
			dn = domain;
			cp = sp;
			while ((n = *cp++) != 0)
			{
				/* 
				 * check for indirection
				 */
				switch (n & MOWGLI_DNS_NS_CMPRSFLAGS)
				{
				case 0:		/* normal case, n == len */
					n = labellen(cp - 1);	/* XXX */

					if (n != *dn++)
						goto next;

					for ( ; n > 0; n--)
						if (mowgli_dns_mklower(*dn++) != mowgli_dns_mklower(*cp++))
							goto next;
					
					/* Is next root for both ? */
					if (*dn == '\0' && *cp == '\0')
						return sp - rmsg;
					if (*dn)
						continue;
					goto next;
				case MOWGLI_DNS_NS_CMPRSFLAGS:	/* indirection */
					cp = rmsg + (((n & 0x3f) << 8) | *cp);
					break;

				default:	/* illegal type */
					errno = EMSGSIZE;
					return -1;
				}
			}
		  next:;
			sp += *sp + 1;
		}
	}
	errno = ENOENT;
	return -1;
}

/* 
 *  Thinking in noninternationalized USASCII (per the DNS spec),
 *  convert this character to lower case if it's upper case.
 */
static int mowgli_dns_mklower(int ch)
{
	if (ch >= 0x41 && ch <= 0x5A)
		return ch + 0x20;

	return ch;
}

/* From resolv/mkquery.c */

/* 
 * Form all types of queries.
 * Returns the size of the result or -1.
 */
int mowgli_dns_res_mkquery(const char *dname,	/* domain name */
					int query_class, int type,	/* class and type of query */
					unsigned char *buf,	/* buffer to put query */
					int buflen)	/* size of buffer */
{
	mowgli_dns_resheader_t *hp;
	unsigned char *cp;
	int n;
	unsigned char *dnptrs[20], **dpp, **lastdnptr;

	/* 
	 * Initialize header fields.
	 */
	if ((buf == NULL) || (buflen < MOWGLI_DNS_HFIXEDSIZE))
		return -1;
	memset(buf, 0, MOWGLI_DNS_HFIXEDSIZE);
	hp = (mowgli_dns_resheader_t *) buf;

	hp->id = 0;
	hp->opcode = MOWGLI_DNS_QUERY;
	hp->rd = 1;		/* recurse */
	hp->rcode = MOWGLI_DNS_NO_ERRORS;
	cp = buf + MOWGLI_DNS_HFIXEDSIZE;
	buflen -= MOWGLI_DNS_HFIXEDSIZE;
	dpp = dnptrs;
	*dpp++ = buf;
	*dpp++ = NULL;
	lastdnptr = dnptrs + sizeof dnptrs / sizeof dnptrs[0];

	if ((buflen -= MOWGLI_DNS_QFIXEDSIZE) < 0)
		return -1;
	if ((n = mowgli_dns_dn_comp(dname, cp, buflen, dnptrs, lastdnptr)) < 0)
		return -1;

	cp += n;
	buflen -= n;
	MOWGLI_DNS_NS_PUT16(type, cp);
	MOWGLI_DNS_NS_PUT16(query_class, cp);
	hp->qdcount = htons(1);

	return cp - buf;
}
