/*
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 * 	This product includes software developed by the University of
 * 	California, Berkeley and its contributors.
 * 4. 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 "stdinc.h"
#include "ircd_defs.h"
#include "common.h"
#include "ircd.h"
#include "res.h"
#include "reslib.h"
#include "match.h"

#define NS_TYPE_ELT             0x40 /* EDNS0 extended label type */
#define DNS_LABELTYPE_BITSTRING 0x41
#define DNS_MAXLINE 128


struct rb_sockaddr_storage irc_nsaddr_list[IRCD_MAXNS];
int irc_nscount = 0;
char irc_domain[IRCD_RES_HOSTLEN + 1];

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 int parse_resvconf(void);
static void add_nameserver(const char *);

static const char digits[] = "0123456789";
static int labellen(const unsigned char *lp);
static int special(int ch);
static int printable(int ch);
static int irc_decode_bitstring(const char **cpp, char *dn, const char *eom);
static int irc_ns_name_compress(const char *src, unsigned char *dst, size_t dstsiz,
                                const unsigned char **dnptrs, const unsigned char **lastdnptr);
static int irc_dn_find(const unsigned char *, const unsigned char *, const unsigned char * const *,
                       const unsigned char * const *);
static int irc_encode_bitsring(const char **, const char *, unsigned char **, unsigned char **,
                               const char *);
static int irc_ns_name_uncompress(const unsigned char *, const unsigned char *,
                                  const unsigned char *, char *, size_t);
static int irc_ns_name_unpack(const unsigned char *, const unsigned char *,
                              const unsigned char *, unsigned char *,
                              size_t);
static int irc_ns_name_ntop(const char *, char *, size_t);
static int irc_ns_name_skip(const unsigned char **, const unsigned char *);
static int mklower(int ch);

int
irc_res_init(void)
{
    irc_nscount = 0;
    parse_resvconf();
    if (irc_nscount == 0)
        add_nameserver("127.0.0.1");
    return 0;
}

/* parse_resvconf()
 *
 * inputs - NONE
 * output - -1 if failure 0 if success
 * side effects - fills in irc_nsaddr_list
 */
static int
parse_resvconf(void)
{
    char *p;
    char *opt;
    char *arg;
    char input[DNS_MAXLINE];
    FILE *file;

    /* XXX "/etc/resolv.conf" should be from a define in setup.h perhaps
     * for cygwin support etc. this hardcodes it to unix for now -db
     */
    if ((file = fopen("/etc/resolv.conf", "r")) == NULL)
        return -1;

    while (fgets(input, sizeof(input), file) != NULL) {
        /* blow away any newline */
        if ((p = strpbrk(input, "\r\n")) != NULL)
            *p = '\0';

        p = input;
        /* skip until something thats not a space is seen */
        while (IsSpace(*p))
            p++;
        /* if at this point, have a '\0' then continue */
        if (*p == '\0')
            continue;

        /* Ignore comment lines immediately */
        if (*p == '#' || *p == ';')
            continue;

        /* skip until a space is found */
        opt = p;
        while (!IsSpace(*p) && *p != '\0')
            p++;
        if (*p == '\0')
            continue;  /* no arguments?.. ignore this line */
        /* blow away the space character */
        *p++ = '\0';

        /* skip these spaces that are before the argument */
        while (IsSpace(*p))
            p++;
        /* Now arg should be right where p is pointing */
        arg = p;
        if ((p = strpbrk(arg, " \t")) != NULL)
            *p = '\0';  /* take the first word */

        if (irccmp(opt, "domain") == 0)
            rb_strlcpy(irc_domain, arg, sizeof(irc_domain));
        else if (irccmp(opt, "nameserver") == 0)
            add_nameserver(arg);
    }

    fclose(file);
    return 0;
}

/* add_nameserver()
 *
 * input        - either an IPV4 address in dotted quad
 *                or an IPV6 address in : format
 * output       - NONE
 * side effects - entry in irc_nsaddr_list is filled in as needed
 */
static void
add_nameserver(const char *arg)
{
    struct addrinfo hints, *res;

    /* Done max number of nameservers? */
    if (irc_nscount >= IRCD_MAXNS) {
        ilog (L_MAIN, "Too many nameservers, ignoring %s", arg);
        return;
    }

    ilog (L_MAIN, "Using nameserver: %s", arg);

    memset(&hints, 0, sizeof(hints));
    hints.ai_family   = PF_UNSPEC;
    hints.ai_socktype = SOCK_DGRAM;
    hints.ai_flags    = AI_PASSIVE | AI_NUMERICHOST;

    if (getaddrinfo(arg, "domain", &hints, &res))
        return;

    if (res == NULL)
        return;

    memcpy(&irc_nsaddr_list[irc_nscount], res->ai_addr, res->ai_addrlen);
    SET_SS_LEN(&irc_nsaddr_list[irc_nscount], res->ai_addrlen);
    irc_nscount++;
    freeaddrinfo(res);
}

/*
 * Expand compressed domain name 'comp_dn' to full domain name.
 * 'msg' 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
irc_dn_expand(const unsigned char *msg, const unsigned char *eom,
              const unsigned char *src, char *dst, int dstsiz)
{
    int n = irc_ns_name_uncompress(msg, eom, src, dst, (size_t)dstsiz);

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

/*
 * irc_ns_name_uncompress(msg, 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
irc_ns_name_uncompress(const unsigned char *msg, const unsigned char *eom,
                       const unsigned char *src, char *dst, size_t dstsiz)
{
    unsigned char tmp[NS_MAXCDNAME];
    int n;

    if ((n = irc_ns_name_unpack(msg, eom, src, tmp, sizeof tmp)) == -1)
        return(-1);
    if (irc_ns_name_ntop((char*)tmp, dst, dstsiz) == -1)
        return(-1);
    return(n);
}
/*
 * irc_ns_name_unpack(msg, 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
irc_ns_name_unpack(const unsigned char *msg, 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 < 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;
            srcp = msg + (((n & 0x3f) << 8) | (*srcp & 0xff));
            if (srcp < msg || 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 - msg) {
                errno = EMSGSIZE;
                return (-1);
            }
            break;

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

/*
 * irc_ns_name_ntop(src, dst, dstsiz)
 *	Convert an encoded domain name to 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
irc_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 & 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((const unsigned char*)(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 = irc_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);
}

/*
 * 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
irc_dn_comp(const char *src, unsigned char *dst, int dstsiz,
            unsigned char **dnptrs, unsigned char **lastdnptr)
{
    return(irc_ns_name_compress(src, dst, (size_t)dstsiz,
                                (const unsigned char **)dnptrs,
                                (const unsigned char **)lastdnptr));
}

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

    if (irc_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
irc_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 & 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);
}

unsigned int
irc_ns_get16(const unsigned char *src)
{
    unsigned int dst;

    IRC_NS_GET16(dst, src);
    return(dst);
}

unsigned long
irc_ns_get32(const unsigned char *src)
{
    unsigned long dst;

    IRC_NS_GET32(dst, src);
    return(dst);
}

void
irc_ns_put16(unsigned int src, unsigned char *dst)
{
    IRC_NS_PUT16(src, dst);
}

void
irc_ns_put32(unsigned long src, unsigned char *dst)
{
    IRC_NS_PUT32(src, dst);
}

/* From ns_name.c */

/*
 * special(ch)
 *      Thinking in noninternationalized USASCII (per the DNS spec),
 *      is this characted special ("in need of quoting") ?
 * return:
 *      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);
    }
}

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


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

static int
irc_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);
}

/*
 * irc_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
irc_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 = irc_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 & 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) > 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 & 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) > NS_MAXCDNAME) {
        /* src too big */
        errno = EMSGSIZE;
        return (-1);
    }

    return (0);
}

/*
 * irc_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
irc_ns_name_pack(const unsigned char *src, unsigned char *dst, int dstsiz,
                 const unsigned char **dnptrs, const unsigned char **lastdnptr)
{
    unsigned char *dstp;
    const unsigned char **cpp, **lpp, *eob, *msg;
    const unsigned 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 > 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 && msg != NULL) {
            l = irc_dn_find(srcp, msg, (const unsigned char * const *)dnptrs,
                            (const unsigned 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);
}

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

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

static int
irc_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 = DNS_LABELTYPE_BITSTRING;
    **dst = blen;

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

    return(0);
}

/*
 * dn_find(domain, msg, dnptrs, lastdnptr)
 *  Search for the counted-label name in an array of compressed names.
 * return:
 *  offset from msg 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
irc_dn_find(const unsigned char *domain, const unsigned char *msg,
            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 & 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);
}

/*
 *  *  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);
}

/* From resolv/mkquery.c */

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

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

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

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

    cp += n;
    buflen -= n;
    IRC_NS_PUT16(type, cp);
    IRC_NS_PUT16(class, cp);
    hp->qdcount = htons(1);

    return (cp - buf);
}
