/***

  This file is part of avahi.

  avahi is free software; you can redistribute it and/or modify it

  under the terms of the GNU Lesser General Public License as

  published by the Free Software Foundation; either version 2.1 of the

  License, or (at your option) any later version.

  avahi is distributed in the hope that it will be useful, but WITHOUT

  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY

  or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General

  Public License for more details.

  You should have received a copy of the GNU Lesser General Public

  License along with avahi; if not, write to the Free Software

  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307

  USA.

***/

#ifdef HAVE_CONFIG_H

#include <config.h>

#endif

#include <stdlib.h>

#include <string.h>

#include <stdio.h>

#include <assert.h>

#include <sys/types.h>

#include <netinet/in.h>

#include <avahi-common/defs.h>

#include <avahi-common/domain.h>

#include <avahi-common/malloc.h>

#include "dns.h"

#include "log.h"

AvahiDnsPacket* avahi_dns_packet_new(unsigned mtu) {

    AvahiDnsPacket *p;

    size_t max_size;

    if (mtu <= 0)

        max_size = AVAHI_DNS_PACKET_SIZE_MAX;

    else if (mtu >= AVAHI_DNS_PACKET_EXTRA_SIZE)

        max_size = mtu - AVAHI_DNS_PACKET_EXTRA_SIZE;

    else

        max_size = 0;

    if (max_size < AVAHI_DNS_PACKET_HEADER_SIZE)

        max_size = AVAHI_DNS_PACKET_HEADER_SIZE;

    if (!(p = avahi_malloc(sizeof(AvahiDnsPacket) + max_size)))

        return p;

    p->size = p->rindex = AVAHI_DNS_PACKET_HEADER_SIZE;

    p->max_size = max_size;

    p->res_size = 0;

    p->name_table = NULL;

    p->data = NULL;

    memset(AVAHI_DNS_PACKET_DATA(p), 0, p->size);

    return p;

}

AvahiDnsPacket* avahi_dns_packet_new_query(unsigned mtu) {

    AvahiDnsPacket *p;

    if (!(p = avahi_dns_packet_new(mtu)))

        return NULL;

    avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_FLAGS, AVAHI_DNS_FLAGS(0, 0, 0, 0, 0, 0, 0, 0, 0, 0));

    return p;

}

AvahiDnsPacket* avahi_dns_packet_new_response(unsigned mtu, int aa) {

    AvahiDnsPacket *p;

    if (!(p = avahi_dns_packet_new(mtu)))

        return NULL;

    avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_FLAGS, AVAHI_DNS_FLAGS(1, 0, aa, 0, 0, 0, 0, 0, 0, 0));

    return p;

}

AvahiDnsPacket* avahi_dns_packet_new_reply(AvahiDnsPacket* p, unsigned mtu, int copy_queries, int aa) {

    AvahiDnsPacket *r;

    assert(p);

    if (!(r = avahi_dns_packet_new_response(mtu, aa)))

        return NULL;

    if (copy_queries) {

        unsigned saved_rindex;

        uint32_t n;

        saved_rindex = p->rindex;

        p->rindex = AVAHI_DNS_PACKET_HEADER_SIZE;

        for (n = avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_QDCOUNT); n > 0; n--) {

            AvahiKey *k;

            int unicast_response;

            if ((k = avahi_dns_packet_consume_key(p, &unicast_response))) {

                avahi_dns_packet_append_key(r, k, unicast_response);

                avahi_key_unref(k);

            }

        }

        p->rindex = saved_rindex;

        avahi_dns_packet_set_field(r, AVAHI_DNS_FIELD_QDCOUNT, avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_QDCOUNT));

    }

    avahi_dns_packet_set_field(r, AVAHI_DNS_FIELD_ID, avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_ID));

    avahi_dns_packet_set_field(r, AVAHI_DNS_FIELD_FLAGS,

                               (avahi_dns_packet_get_field(r, AVAHI_DNS_FIELD_FLAGS) & ~AVAHI_DNS_FLAG_OPCODE) |

                               (avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS) & AVAHI_DNS_FLAG_OPCODE));

    return r;

}

void avahi_dns_packet_free(AvahiDnsPacket *p) {

    assert(p);

    if (p->name_table)

        avahi_hashmap_free(p->name_table);

    avahi_free(p);

}

void avahi_dns_packet_set_field(AvahiDnsPacket *p, unsigned idx, uint16_t v) {

    assert(p);

    assert(idx < AVAHI_DNS_PACKET_HEADER_SIZE);

    ((uint16_t*) AVAHI_DNS_PACKET_DATA(p))[idx] = htons(v);

}

uint16_t avahi_dns_packet_get_field(AvahiDnsPacket *p, unsigned idx) {

    assert(p);

    assert(idx < AVAHI_DNS_PACKET_HEADER_SIZE);

    return ntohs(((uint16_t*) AVAHI_DNS_PACKET_DATA(p))[idx]);

}

void avahi_dns_packet_inc_field(AvahiDnsPacket *p, unsigned idx) {

    assert(p);

    assert(idx < AVAHI_DNS_PACKET_HEADER_SIZE);

    avahi_dns_packet_set_field(p, idx, avahi_dns_packet_get_field(p, idx) + 1);

}

static void name_table_cleanup(void *key, void *value, void *user_data) {

    AvahiDnsPacket *p = user_data;

    if ((uint8_t*) value >= AVAHI_DNS_PACKET_DATA(p) + p->size)

        avahi_hashmap_remove(p->name_table, key);

}

void avahi_dns_packet_cleanup_name_table(AvahiDnsPacket *p) {

    if (p->name_table)

        avahi_hashmap_foreach(p->name_table, name_table_cleanup, p);

}

uint8_t* avahi_dns_packet_append_name(AvahiDnsPacket *p, const char *name) {

    uint8_t *d, *saved_ptr = NULL;

    size_t saved_size;

    assert(p);

    assert(name);

    saved_size = p->size;

    saved_ptr = avahi_dns_packet_extend(p, 0);

    while (*name) {

        uint8_t* prev;

        const char *pname;

        char label[64], *u;

        /* Check whether we can compress this name. */

        if (p->name_table && (prev = avahi_hashmap_lookup(p->name_table, name))) {

            unsigned idx;

            assert(prev >= AVAHI_DNS_PACKET_DATA(p));

            idx = (unsigned) (prev - AVAHI_DNS_PACKET_DATA(p));

            assert(idx < p->size);

            if (idx < 0x4000) {

                uint8_t *t;

                if (!(t = (uint8_t*) avahi_dns_packet_extend(p, sizeof(uint16_t))))

                    return NULL;

    t[0] = (uint8_t) ((0xC000 | idx) >> 8);

    t[1] = (uint8_t) idx;

                return saved_ptr;

            }

        }

        pname = name;

        if (!(avahi_unescape_label(&name, label, sizeof(label))))

            goto fail;

        if (!(d = avahi_dns_packet_append_string(p, label)))

            goto fail;

        if (!p->name_table)

            /* This works only for normalized domain names */

            p->name_table = avahi_hashmap_new(avahi_string_hash, avahi_string_equal, avahi_free, NULL);

        if (!(u = avahi_strdup(pname)))

            avahi_log_error("avahi_strdup() failed.");

        else

            avahi_hashmap_insert(p->name_table, u, d);

    }

    if (!(d = avahi_dns_packet_extend(p, 1)))

        goto fail;

    *d = 0;

    return saved_ptr;

fail:

    p->size = saved_size;

    avahi_dns_packet_cleanup_name_table(p);

    return NULL;

}

uint8_t* avahi_dns_packet_append_uint16(AvahiDnsPacket *p, uint16_t v) {

    uint8_t *d;

    assert(p);

    if (!(d = avahi_dns_packet_extend(p, sizeof(uint16_t))))

        return NULL;

    d[0] = (uint8_t) (v >> 8);

    d[1] = (uint8_t) v;

    return d;

}

uint8_t *avahi_dns_packet_append_uint32(AvahiDnsPacket *p, uint32_t v) {

    uint8_t *d;

    assert(p);

    if (!(d = avahi_dns_packet_extend(p, sizeof(uint32_t))))

        return NULL;

    d[0] = (uint8_t) (v >> 24);

    d[1] = (uint8_t) (v >> 16);

    d[2] = (uint8_t) (v >> 8);

    d[3] = (uint8_t) v;

    return d;

}

uint8_t *avahi_dns_packet_append_bytes(AvahiDnsPacket  *p, const void *b, size_t l) {

    uint8_t* d;

    assert(p);

    assert(b);

    assert(l);

    if (!(d = avahi_dns_packet_extend(p, l)))

        return NULL;

    memcpy(d, b, l);

    return d;

}

uint8_t* avahi_dns_packet_append_string(AvahiDnsPacket *p, const char *s) {

    uint8_t* d;

    size_t k;

    assert(p);

    assert(s);

    if ((k = strlen(s)) >= 255)

        k = 255;

    if (!(d = avahi_dns_packet_extend(p, k+1)))

        return NULL;

    *d = (uint8_t) k;

    memcpy(d+1, s, k);

    return d;

}

uint8_t *avahi_dns_packet_extend(AvahiDnsPacket *p, size_t l) {

    uint8_t *d;

    assert(p);

    if (p->size+l > p->max_size)

        return NULL;

    d = AVAHI_DNS_PACKET_DATA(p) + p->size;

    p->size += l;

    return d;

}

int avahi_dns_packet_check_valid(AvahiDnsPacket *p) {

    uint16_t flags;

    assert(p);

    if (p->size < AVAHI_DNS_PACKET_HEADER_SIZE)

        return -1;

    flags = avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS);

    if (flags & AVAHI_DNS_FLAG_OPCODE)

        return -1;

    return 0;

}

int avahi_dns_packet_check_valid_multicast(AvahiDnsPacket *p) {

    uint16_t flags;

    assert(p);

    if (avahi_dns_packet_check_valid(p) < 0)

        return -1;

    flags = avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS);

    if (flags & AVAHI_DNS_FLAG_RCODE)

        return -1;

    return 0;

}

int avahi_dns_packet_is_query(AvahiDnsPacket *p) {

    assert(p);

    return !(avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS) & AVAHI_DNS_FLAG_QR);

}

static int consume_labels(AvahiDnsPacket *p, unsigned idx, char *ret_name, size_t l) {

    int ret = 0;

    int compressed = 0;

    int first_label = 1;

    unsigned label_ptr;

    int i;

    assert(p && ret_name && l);

    for (i = 0; i < AVAHI_DNS_LABELS_MAX; i++) {

        uint8_t n;

        if (idx+1 > p->size)

            return -1;

        n = AVAHI_DNS_PACKET_DATA(p)[idx];

        if (!n) {

            idx++;

            if (!compressed)

                ret++;

            if (l < 1)

                return -1;

            *ret_name = 0;

            return ret;

        } else if (n <= 63) {

            /* Uncompressed label */

            idx++;

            if (!compressed)

                ret++;

            if (idx + n > p->size)

                return -1;

            if ((size_t) n + 1 > l)

                return -1;

            if (!first_label) {

                *(ret_name++) = '.';

                l--;

            } else

                first_label = 0;

            if (!(avahi_escape_label((char*) AVAHI_DNS_PACKET_DATA(p) + idx, n, &ret_name, &l)))

                return -1;

            idx += n;

            if (!compressed)

                ret += n;

        } else if ((n & 0xC0) == 0xC0) {

            /* Compressed label */

            if (idx+2 > p->size)

                return -1;

            label_ptr = ((unsigned) (AVAHI_DNS_PACKET_DATA(p)[idx] & ~0xC0)) << 8 | AVAHI_DNS_PACKET_DATA(p)[idx+1];

            if ((label_ptr < AVAHI_DNS_PACKET_HEADER_SIZE) || (label_ptr >= idx))

                return -1;

            idx = label_ptr;

            if (!compressed)

                ret += 2;

            compressed = 1;

        } else

            return -1;

    }

    return -1;

}

int avahi_dns_packet_consume_name(AvahiDnsPacket *p, char *ret_name, size_t l) {

    int r;

    if ((r = consume_labels(p, p->rindex, ret_name, l)) < 0)

        return -1;

    p->rindex += r;

    return 0;

}

int avahi_dns_packet_consume_uint16(AvahiDnsPacket *p, uint16_t *ret_v) {

    uint8_t *d;

    assert(p);

    assert(ret_v);

    if (p->rindex + sizeof(uint16_t) > p->size)

        return -1;

    d = (uint8_t*) (AVAHI_DNS_PACKET_DATA(p) + p->rindex);

    *ret_v = (d[0] << 8) | d[1];

    p->rindex += sizeof(uint16_t);

    return 0;

}

int avahi_dns_packet_consume_uint32(AvahiDnsPacket *p, uint32_t *ret_v) {

    uint8_t* d;

    assert(p);

    assert(ret_v);

    if (p->rindex + sizeof(uint32_t) > p->size)

        return -1;

    d = (uint8_t*) (AVAHI_DNS_PACKET_DATA(p) + p->rindex);

    *ret_v = ((uint32_t)d[0] << 24) | ((uint32_t)d[1] << 16) | ((uint32_t)d[2] << 8) | (uint32_t)d[3];

    p->rindex += sizeof(uint32_t);

    return 0;

}

int avahi_dns_packet_consume_bytes(AvahiDnsPacket *p, void * ret_data, size_t l) {

    assert(p);

    assert(ret_data);

    assert(l > 0);

    if (p->rindex + l > p->size)

        return -1;

    memcpy(ret_data, AVAHI_DNS_PACKET_DATA(p) + p->rindex, l);

    p->rindex += l;

    return 0;

}

int avahi_dns_packet_consume_string(AvahiDnsPacket *p, char *ret_string, size_t l) {

    size_t k;

    assert(p);

    assert(ret_string);

    assert(l > 0);

    if (p->rindex >= p->size)

        return -1;

    k = AVAHI_DNS_PACKET_DATA(p)[p->rindex];

    if (p->rindex+1+k > p->size)

        return -1;

    if (l > k+1)

        l = k+1;

    memcpy(ret_string, AVAHI_DNS_PACKET_DATA(p)+p->rindex+1, l-1);

    ret_string[l-1] = 0;

    p->rindex += 1+k;

    return 0;

}

const void* avahi_dns_packet_get_rptr(AvahiDnsPacket *p) {

    assert(p);

    if (p->rindex > p->size)

        return NULL;

    return AVAHI_DNS_PACKET_DATA(p) + p->rindex;

}

int avahi_dns_packet_skip(AvahiDnsPacket *p, size_t length) {

    assert(p);

    if (p->rindex + length > p->size)

        return -1;

    p->rindex += length;

    return 0;

}

static int parse_rdata(AvahiDnsPacket *p, AvahiRecord *r, uint16_t rdlength) {

    char buf[AVAHI_DOMAIN_NAME_MAX];

    const void* start;

    assert(p);

    assert(r);

    start = avahi_dns_packet_get_rptr(p);

    switch (r->key->type) {

        case AVAHI_DNS_TYPE_PTR:

        case AVAHI_DNS_TYPE_CNAME:

        case AVAHI_DNS_TYPE_NS:

            if (avahi_dns_packet_consume_name(p, buf, sizeof(buf)) < 0)

                return -1;

            r->data.ptr.name = avahi_strdup(buf);

            break;

        case AVAHI_DNS_TYPE_SRV:

            if (avahi_dns_packet_consume_uint16(p, &r->data.srv.priority) < 0 ||

                avahi_dns_packet_consume_uint16(p, &r->data.srv.weight) < 0 ||

                avahi_dns_packet_consume_uint16(p, &r->data.srv.port) < 0 ||

                avahi_dns_packet_consume_name(p, buf, sizeof(buf)) < 0)

                return -1;

            r->data.srv.name = avahi_strdup(buf);

            break;

        case AVAHI_DNS_TYPE_HINFO:

            if (avahi_dns_packet_consume_string(p, buf, sizeof(buf)) < 0)

                return -1;

            r->data.hinfo.cpu = avahi_strdup(buf);

            if (avahi_dns_packet_consume_string(p, buf, sizeof(buf)) < 0)

                return -1;

            r->data.hinfo.os = avahi_strdup(buf);

            break;

        case AVAHI_DNS_TYPE_TXT:

            if (rdlength > 0) {

                if (avahi_string_list_parse(avahi_dns_packet_get_rptr(p), rdlength, &r->data.txt.string_list) < 0)

                    return -1;

                if (avahi_dns_packet_skip(p, rdlength) < 0)

                    return -1;

            } else

                r->data.txt.string_list = NULL;

            break;

        case AVAHI_DNS_TYPE_A:

/*             avahi_log_debug("A"); */

            if (avahi_dns_packet_consume_bytes(p, &r->data.a.address, sizeof(AvahiIPv4Address)) < 0)

                return -1;

            break;

        case AVAHI_DNS_TYPE_AAAA:

/*             avahi_log_debug("aaaa"); */

            if (avahi_dns_packet_consume_bytes(p, &r->data.aaaa.address, sizeof(AvahiIPv6Address)) < 0)

                return -1;

            break;

        default:

/*             avahi_log_debug("generic"); */

            if (rdlength > 0) {

                r->data.generic.data = avahi_memdup(avahi_dns_packet_get_rptr(p), rdlength);

                r->data.generic.size = rdlength;

                if (avahi_dns_packet_skip(p, rdlength) < 0)

                    return -1;

            }

            break;

    }

    /* Check if we read enough data */

    if ((const uint8_t*) avahi_dns_packet_get_rptr(p) - (const uint8_t*) start != rdlength)

        return -1;

    return 0;

}

AvahiRecord* avahi_dns_packet_consume_record(AvahiDnsPacket *p, int *ret_cache_flush) {

    char name[AVAHI_DOMAIN_NAME_MAX];

    uint16_t type, class;

    uint32_t ttl;

    uint16_t rdlength;

    AvahiRecord *r = NULL;

    assert(p);

    if (avahi_dns_packet_consume_name(p, name, sizeof(name)) < 0 ||

        avahi_dns_packet_consume_uint16(p, &type) < 0 ||

        avahi_dns_packet_consume_uint16(p, &class) < 0 ||

        avahi_dns_packet_consume_uint32(p, &ttl) < 0 ||

        avahi_dns_packet_consume_uint16(p, &rdlength) < 0 ||

        p->rindex + rdlength > p->size)

        goto fail;

    if (ret_cache_flush)

        *ret_cache_flush = !!(class & AVAHI_DNS_CACHE_FLUSH);

    class &= ~AVAHI_DNS_CACHE_FLUSH;

    if (!(r = avahi_record_new_full(name, class, type, ttl)))

        goto fail;

    if (parse_rdata(p, r, rdlength) < 0)

        goto fail;

    if (!avahi_record_is_valid(r))

        goto fail;

    return r;

fail:

    if (r)

        avahi_record_unref(r);

    return NULL;

}

AvahiKey* avahi_dns_packet_consume_key(AvahiDnsPacket *p, int *ret_unicast_response) {

    char name[256];

    uint16_t type, class;

    AvahiKey *k;

    assert(p);

    if (avahi_dns_packet_consume_name(p, name, sizeof(name)) < 0 ||

        avahi_dns_packet_consume_uint16(p, &type) < 0 ||

        avahi_dns_packet_consume_uint16(p, &class) < 0)

        return NULL;

    if (ret_unicast_response)

        *ret_unicast_response = !!(class & AVAHI_DNS_UNICAST_RESPONSE);

    class &= ~AVAHI_DNS_UNICAST_RESPONSE;

    if (!(k = avahi_key_new(name, class, type)))

        return NULL;

    if (!avahi_key_is_valid(k)) {

        avahi_key_unref(k);

        return NULL;

    }

    return k;

}

uint8_t* avahi_dns_packet_append_key(AvahiDnsPacket *p, AvahiKey *k, int unicast_response) {

    uint8_t *t;

    size_t size;

    assert(p);

    assert(k);

    size = p->size;

    if (!(t = avahi_dns_packet_append_name(p, k->name)) ||

        !avahi_dns_packet_append_uint16(p, k->type) ||

        !avahi_dns_packet_append_uint16(p, k->clazz | (unicast_response ? AVAHI_DNS_UNICAST_RESPONSE : 0))) {

        p->size = size;

        avahi_dns_packet_cleanup_name_table(p);

        return NULL;

    }

    return t;

}

static int append_rdata(AvahiDnsPacket *p, AvahiRecord *r) {

    assert(p);

    assert(r);

    switch (r->key->type) {

        case AVAHI_DNS_TYPE_PTR:

        case AVAHI_DNS_TYPE_CNAME:

        case AVAHI_DNS_TYPE_NS:

            if (!(avahi_dns_packet_append_name(p, r->data.ptr.name)))

                return -1;

            break;

        case AVAHI_DNS_TYPE_SRV:

            if (!avahi_dns_packet_append_uint16(p, r->data.srv.priority) ||

                !avahi_dns_packet_append_uint16(p, r->data.srv.weight) ||

                !avahi_dns_packet_append_uint16(p, r->data.srv.port) ||

                !avahi_dns_packet_append_name(p, r->data.srv.name))

                return -1;

            break;

        case AVAHI_DNS_TYPE_HINFO:

            if (!avahi_dns_packet_append_string(p, r->data.hinfo.cpu) ||

                !avahi_dns_packet_append_string(p, r->data.hinfo.os))

                return -1;

            break;

        case AVAHI_DNS_TYPE_TXT: {

            uint8_t *data;

            size_t n;

            n = avahi_string_list_serialize(r->data.txt.string_list, NULL, 0);

            if (!(data = avahi_dns_packet_extend(p, n)))

                return -1;

            avahi_string_list_serialize(r->data.txt.string_list, data, n);

            break;

        }

        case AVAHI_DNS_TYPE_A:

            if (!avahi_dns_packet_append_bytes(p, &r->data.a.address, sizeof(r->data.a.address)))

                return -1;

            break;

        case AVAHI_DNS_TYPE_AAAA:

            if (!avahi_dns_packet_append_bytes(p, &r->data.aaaa.address, sizeof(r->data.aaaa.address)))

                return -1;

            break;

        default:

            if (r->data.generic.size)

                if (!avahi_dns_packet_append_bytes(p, r->data.generic.data, r->data.generic.size))

                    return -1;

            break;

    }

    return 0;

}

uint8_t* avahi_dns_packet_append_record(AvahiDnsPacket *p, AvahiRecord *r, int cache_flush, unsigned max_ttl) {

    uint8_t *t, *l, *start;

    size_t size;

    assert(p);

    assert(r);

    size = p->size;

    if (!(t = avahi_dns_packet_append_name(p, r->key->name)) ||

        !avahi_dns_packet_append_uint16(p, r->key->type) ||

        !avahi_dns_packet_append_uint16(p, cache_flush ? (r->key->clazz | AVAHI_DNS_CACHE_FLUSH) : (r->key->clazz &~ AVAHI_DNS_CACHE_FLUSH)) ||

        !avahi_dns_packet_append_uint32(p, (max_ttl && r->ttl > max_ttl) ? max_ttl : r->ttl) ||

        !(l = avahi_dns_packet_append_uint16(p, 0)))

        goto fail;

    start = avahi_dns_packet_extend(p, 0);

    if (append_rdata(p, r) < 0)

        goto fail;

    size = avahi_dns_packet_extend(p, 0) - start;

    assert(size <= AVAHI_DNS_RDATA_MAX);

/*     avahi_log_debug("appended %u", size); */

    l[0] = (uint8_t) ((uint16_t) size >> 8);

    l[1] = (uint8_t) ((uint16_t) size);

    return t;

fail:

    p->size = size;

    avahi_dns_packet_cleanup_name_table(p);

    return NULL;

}

int avahi_dns_packet_is_empty(AvahiDnsPacket *p) {

    assert(p);

    return p->size <= AVAHI_DNS_PACKET_HEADER_SIZE;

}

size_t avahi_dns_packet_space(AvahiDnsPacket *p) {

    assert(p);

    assert(p->size <= p->max_size);

    return p->max_size - p->size;

}

size_t avahi_dns_packet_reserve_size(AvahiDnsPacket *p, size_t res_size) {

    assert(p);

    assert(p->size + p->res_size <= p->max_size);

    if ((p->size + p->res_size + res_size) <= p->max_size)

   p->res_size += res_size;

    return p->res_size;

}

size_t avahi_dns_packet_reserved_space(AvahiDnsPacket *p) {

    assert(p);

    assert(p->size + p->res_size <= p->max_size);

    return p->max_size - p->size - p->res_size;

}

int avahi_rdata_parse(AvahiRecord *record, const void* rdata, size_t size) {

    int ret;

    AvahiDnsPacket p;

    assert(record);

    assert(rdata);

    p.data = (void*) rdata;

    p.max_size = p.size = size;

    p.rindex = 0;

    p.name_table = NULL;

    ret = parse_rdata(&p, record, size);

    assert(!p.name_table);

    return ret;

}

size_t avahi_rdata_serialize(AvahiRecord *record, void *rdata, size_t max_size) {

    int ret;

    AvahiDnsPacket p;

    assert(record);

    assert(rdata);

    assert(max_size > 0);

    p.data = (void*) rdata;

    p.max_size = max_size;

    p.size = p.rindex = 0;

    p.name_table = NULL;

    ret = append_rdata(&p, record);

    if (p.name_table)

         avahi_hashmap_free(p.name_table);

    if (ret < 0)

        return (size_t) -1;

    return p.size;

}