git.meshlink.io Git - catta/blob - avahi-core/dns.c

   1 /* $Id$ */
   2
   3 /***
   4   This file is part of avahi.
   5
   6   avahi is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as
   8   published by the Free Software Foundation; either version 2.1 of the
   9   License, or (at your option) any later version.
  10
  11   avahi is distributed in the hope that it will be useful, but WITHOUT
  12   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  13   or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
  14   Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public
  17   License along with avahi; if not, write to the Free Software
  18   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  19   USA.
  20 ***/
  21
  22 #ifdef HAVE_CONFIG_H
  23 #include <config.h>
  24 #endif
  25
  26 #include <netinet/in.h>
  27
  28 #include <stdlib.h>
  29 #include <string.h>
  30 #include <stdio.h>
  31
  32 #include "dns.h"
  33 #include "util.h"
  34
  35 AvahiDnsPacket* avahi_dns_packet_new(guint mtu) {
  36     AvahiDnsPacket *p;
  37     guint max_size;
  38
  39     if (mtu <= 0)
  40         max_size = AVAHI_DNS_PACKET_MAX_SIZE;
  41     else if (mtu >= 48)
  42         max_size = mtu - 48;
  43     else
  44         max_size = 0;
  45
  46     if (max_size < AVAHI_DNS_PACKET_HEADER_SIZE)
  47         max_size = AVAHI_DNS_PACKET_HEADER_SIZE;
  48
  49     p = g_malloc(sizeof(AvahiDnsPacket) + max_size);
  50     p->size = p->rindex = AVAHI_DNS_PACKET_HEADER_SIZE;
  51     p->max_size = max_size;
  52     p->name_table = NULL;
  53
  54     memset(AVAHI_DNS_PACKET_DATA(p), 0, p->size);
  55     return p;
  56 }
  57
  58 AvahiDnsPacket* avahi_dns_packet_new_query(guint mtu) {
  59     AvahiDnsPacket *p;
  60
  61     p = avahi_dns_packet_new(mtu);
  62     avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_FLAGS, AVAHI_DNS_FLAGS(0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
  63     return p;
  64 }
  65
  66 AvahiDnsPacket* avahi_dns_packet_new_response(guint mtu, gboolean aa) {
  67     AvahiDnsPacket *p;
  68
  69     p = avahi_dns_packet_new(mtu);
  70     avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_FLAGS, AVAHI_DNS_FLAGS(1, 0, aa, 0, 0, 0, 0, 0, 0, 0));
  71     return p;
  72 }
  73
  74 AvahiDnsPacket* avahi_dns_packet_new_reply(AvahiDnsPacket* p, guint mtu, gboolean copy_queries, gboolean aa) {
  75     AvahiDnsPacket *r;
  76     g_assert(p);
  77
  78     r = avahi_dns_packet_new_response(mtu, aa);
  79
  80     if (copy_queries) {
  81         guint n, saved_rindex;
  82
  83         saved_rindex = p->rindex;
  84         p->rindex = AVAHI_DNS_PACKET_HEADER_SIZE;
  85
  86         for (n = avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_QDCOUNT); n > 0; n--) {
  87             AvahiKey *k;
  88             gboolean unicast_response;
  89
  90             if ((k = avahi_dns_packet_consume_key(p, &unicast_response))) {
  91                 avahi_dns_packet_append_key(r, k, unicast_response);
  92                 avahi_key_unref(k);
  93             }
  94         }
  95
  96         p->rindex = saved_rindex;
  97
  98         avahi_dns_packet_set_field(r, AVAHI_DNS_FIELD_QDCOUNT, avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_QDCOUNT));
  99     }
 100
 101     avahi_dns_packet_set_field(r, AVAHI_DNS_FIELD_ID, avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_ID));
 102
 103     avahi_dns_packet_set_field(r, AVAHI_DNS_FIELD_FLAGS,
 104                                (avahi_dns_packet_get_field(r, AVAHI_DNS_FIELD_FLAGS) & ~AVAHI_DNS_FLAG_OPCODE) |
 105                                (avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS) & AVAHI_DNS_FLAG_OPCODE));
 106
 107     return r;
 108 }
 109
 110
 111 void avahi_dns_packet_free(AvahiDnsPacket *p) {
 112     g_assert(p);
 113
 114     if (p->name_table)
 115         g_hash_table_destroy(p->name_table);
 116
 117     g_free(p);
 118 }
 119
 120 void avahi_dns_packet_set_field(AvahiDnsPacket *p, guint index, guint16 v) {
 121     g_assert(p);
 122     g_assert(index < AVAHI_DNS_PACKET_HEADER_SIZE);
 123
 124     ((guint16*) AVAHI_DNS_PACKET_DATA(p))[index] = g_htons(v);
 125 }
 126
 127 guint16 avahi_dns_packet_get_field(AvahiDnsPacket *p, guint index) {
 128     g_assert(p);
 129     g_assert(index < AVAHI_DNS_PACKET_HEADER_SIZE);
 130
 131     return g_ntohs(((guint16*) AVAHI_DNS_PACKET_DATA(p))[index]);
 132 }
 133
 134 void avahi_dns_packet_inc_field(AvahiDnsPacket *p, guint index) {
 135     g_assert(p);
 136
 137     avahi_dns_packet_set_field(p, index, avahi_dns_packet_get_field(p, index) + 1);
 138 }
 139
 140
 141
 142 guint8* avahi_dns_packet_append_name(AvahiDnsPacket *p, const gchar *name) {
 143     guint8 *d, *saved_ptr = NULL;
 144     guint saved_size;
 145
 146     g_assert(p);
 147     g_assert(name);
 148
 149     saved_size = p->size;
 150     saved_ptr = avahi_dns_packet_extend(p, 0);
 151
 152     while (*name) {
 153         guint8* prev;
 154         const gchar *pname;
 155         gchar label[64];
 156
 157         /* Check whether we can compress this name. */
 158
 159         if (p->name_table && (prev = g_hash_table_lookup(p->name_table, name))) {
 160             guint index;
 161
 162             g_assert(prev >= AVAHI_DNS_PACKET_DATA(p));
 163             index = (guint) (prev - AVAHI_DNS_PACKET_DATA(p));
 164
 165             g_assert(index < p->size);
 166
 167             if (index < 0x4000) {
 168                 guint16 *t;
 169                 if (!(t = (guint16*) avahi_dns_packet_extend(p, sizeof(guint16))))
 170                     return NULL;
 171
 172                 *t = g_htons((0xC000 | index));
 173                 return saved_ptr;
 174             }
 175         }
 176
 177         pname = name;
 178
 179         if (!(avahi_unescape_label(&name, label, sizeof(label))))
 180             goto fail;
 181
 182         if (!(d = avahi_dns_packet_append_string(p, label)))
 183             goto fail;
 184
 185         if (!p->name_table)
 186             /* This works only for normalized domain names */
 187             p->name_table = g_hash_table_new_full((GHashFunc) g_str_hash, (GEqualFunc) g_str_equal, g_free, NULL);
 188
 189         g_hash_table_insert(p->name_table, g_strdup(pname), d);
 190     }
 191
 192     if (!(d = avahi_dns_packet_extend(p, 1)))
 193         goto fail;
 194
 195     *d = 0;
 196
 197     return saved_ptr;
 198
 199 fail:
 200     p->size = saved_size;
 201     return NULL;
 202 }
 203
 204 guint8* avahi_dns_packet_append_uint16(AvahiDnsPacket *p, guint16 v) {
 205     guint8 *d;
 206     g_assert(p);
 207
 208     if (!(d = avahi_dns_packet_extend(p, sizeof(guint16))))
 209         return NULL;
 210
 211     *((guint16*) d) = g_htons(v);
 212     return d;
 213 }
 214
 215 guint8 *avahi_dns_packet_append_uint32(AvahiDnsPacket *p, guint32 v) {
 216     guint8 *d;
 217     g_assert(p);
 218
 219     if (!(d = avahi_dns_packet_extend(p, sizeof(guint32))))
 220         return NULL;
 221
 222     *((guint32*) d) = g_htonl(v);
 223
 224     return d;
 225 }
 226
 227 guint8 *avahi_dns_packet_append_bytes(AvahiDnsPacket  *p, gconstpointer b, guint l) {
 228     guint8* d;
 229
 230     g_assert(p);
 231     g_assert(b);
 232     g_assert(l);
 233
 234     if (!(d = avahi_dns_packet_extend(p, l)))
 235         return NULL;
 236
 237     memcpy(d, b, l);
 238     return d;
 239 }
 240
 241 guint8* avahi_dns_packet_append_string(AvahiDnsPacket *p, const gchar *s) {
 242     guint8* d;
 243     guint k;
 244
 245     g_assert(p);
 246     g_assert(s);
 247
 248     if ((k = strlen(s)) >= 255)
 249         k = 255;
 250
 251     if (!(d = avahi_dns_packet_extend(p, k+1)))
 252         return NULL;
 253
 254     *d = (guint8) k;
 255     memcpy(d+1, s, k);
 256
 257     return d;
 258 }
 259
 260 guint8 *avahi_dns_packet_extend(AvahiDnsPacket *p, guint l) {
 261     guint8 *d;
 262
 263     g_assert(p);
 264
 265     if (p->size+l > p->max_size)
 266         return NULL;
 267
 268     d = AVAHI_DNS_PACKET_DATA(p) + p->size;
 269     p->size += l;
 270
 271     return d;
 272 }
 273
 274 gint avahi_dns_packet_check_valid(AvahiDnsPacket *p) {
 275     guint16 flags;
 276     g_assert(p);
 277
 278     if (p->size < 12)
 279         return -1;
 280
 281     flags = avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS);
 282
 283     if (flags & AVAHI_DNS_FLAG_OPCODE || flags & AVAHI_DNS_FLAG_RCODE)
 284         return -1;
 285
 286     return 0;
 287 }
 288
 289 gint avahi_dns_packet_is_query(AvahiDnsPacket *p) {
 290     g_assert(p);
 291
 292     return !(avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS) & AVAHI_DNS_FLAG_QR);
 293 }
 294
 295 static gint consume_labels(AvahiDnsPacket *p, guint index, gchar *ret_name, guint l) {
 296     gint ret = 0;
 297     int compressed = 0;
 298     int first_label = 1;
 299     g_assert(p && ret_name && l);
 300
 301     for (;;) {
 302         guint8 n;
 303
 304         if (index+1 > p->size)
 305             return -1;
 306
 307         n = AVAHI_DNS_PACKET_DATA(p)[index];
 308
 309         if (!n) {
 310             index++;
 311             if (!compressed)
 312                 ret++;
 313
 314             if (l < 1)
 315                 return -1;
 316             *ret_name = 0;
 317
 318             return ret;
 319
 320         } else if (n <= 63) {
 321             /* Uncompressed label */
 322             index++;
 323             if (!compressed)
 324                 ret++;
 325
 326             if (index + n > p->size)
 327                 return -1;
 328
 329             if ((guint) n + 1 > l)
 330                 return -1;
 331
 332             if (!first_label) {
 333                 *(ret_name++) = '.';
 334                 l--;
 335             } else
 336                 first_label = 0;
 337
 338             if (!(avahi_escape_label(AVAHI_DNS_PACKET_DATA(p) + index, n, &ret_name, &l)))
 339                 return -1;
 340
 341             index += n;
 342
 343             if (!compressed)
 344                 ret += n;
 345         } else if ((n & 0xC0) == 0xC0) {
 346             /* Compressed label */
 347
 348             if (index+2 > p->size)
 349                 return -1;
 350
 351             index = ((guint) (AVAHI_DNS_PACKET_DATA(p)[index] & ~0xC0)) << 8 | AVAHI_DNS_PACKET_DATA(p)[index+1];
 352
 353             if (!compressed)
 354                 ret += 2;
 355
 356             compressed = 1;
 357         } else
 358             return -1;
 359     }
 360 }
 361
 362 gint avahi_dns_packet_consume_name(AvahiDnsPacket *p, gchar *ret_name, guint l) {
 363     gint r;
 364
 365     if ((r = consume_labels(p, p->rindex, ret_name, l)) < 0)
 366         return -1;
 367
 368     p->rindex += r;
 369     return 0;
 370 }
 371
 372 gint avahi_dns_packet_consume_uint16(AvahiDnsPacket *p, guint16 *ret_v) {
 373     g_assert(p);
 374     g_assert(ret_v);
 375
 376     if (p->rindex + sizeof(guint16) > p->size)
 377         return -1;
 378
 379     *ret_v = g_ntohs(*((guint16*) (AVAHI_DNS_PACKET_DATA(p) + p->rindex)));
 380     p->rindex += sizeof(guint16);
 381
 382     return 0;
 383 }
 384
 385 gint avahi_dns_packet_consume_uint32(AvahiDnsPacket *p, guint32 *ret_v) {
 386     g_assert(p);
 387     g_assert(ret_v);
 388
 389     if (p->rindex + sizeof(guint32) > p->size)
 390         return -1;
 391
 392     *ret_v = g_ntohl(*((guint32*) (AVAHI_DNS_PACKET_DATA(p) + p->rindex)));
 393     p->rindex += sizeof(guint32);
 394
 395     return 0;
 396 }
 397
 398 gint avahi_dns_packet_consume_bytes(AvahiDnsPacket *p, gpointer ret_data, guint l) {
 399     g_assert(p);
 400     g_assert(ret_data);
 401     g_assert(l > 0);
 402
 403     if (p->rindex + l > p->size)
 404         return -1;
 405
 406     memcpy(ret_data, AVAHI_DNS_PACKET_DATA(p) + p->rindex, l);
 407     p->rindex += l;
 408
 409     return 0;
 410 }
 411
 412 gint avahi_dns_packet_consume_string(AvahiDnsPacket *p, gchar *ret_string, guint l) {
 413     guint k;
 414
 415     g_assert(p);
 416     g_assert(ret_string);
 417     g_assert(l > 0);
 418
 419     if (p->rindex >= p->size)
 420         return -1;
 421
 422     k = AVAHI_DNS_PACKET_DATA(p)[p->rindex];
 423
 424     if (p->rindex+1+k > p->size)
 425         return -1;
 426
 427     if (l > k+1)
 428         l = k+1;
 429
 430     memcpy(ret_string, AVAHI_DNS_PACKET_DATA(p)+p->rindex+1, l-1);
 431     ret_string[l-1] = 0;
 432
 433
 434     p->rindex += 1+k;
 435
 436     return 0;
 437
 438 }
 439
 440 gconstpointer avahi_dns_packet_get_rptr(AvahiDnsPacket *p) {
 441     g_assert(p);
 442
 443     if (p->rindex > p->size)
 444         return NULL;
 445
 446     return AVAHI_DNS_PACKET_DATA(p) + p->rindex;
 447 }
 448
 449 gint avahi_dns_packet_skip(AvahiDnsPacket *p, guint length) {
 450     g_assert(p);
 451
 452     if (p->rindex + length > p->size)
 453         return -1;
 454
 455     p->rindex += length;
 456     return 0;
 457 }
 458
 459 AvahiRecord* avahi_dns_packet_consume_record(AvahiDnsPacket *p, gboolean *ret_cache_flush) {
 460     gchar name[257], buf[257];
 461     guint16 type, class;
 462     guint32 ttl;
 463     guint16 rdlength;
 464     AvahiRecord *r = NULL;
 465     gconstpointer start;
 466
 467     g_assert(p);
 468     g_assert(ret_cache_flush);
 469
 470 /*     g_message("consume_record()"); */
 471
 472     if (avahi_dns_packet_consume_name(p, name, sizeof(name)) < 0 ||
 473         avahi_dns_packet_consume_uint16(p, &type) < 0 ||
 474         avahi_dns_packet_consume_uint16(p, &class) < 0 ||
 475         avahi_dns_packet_consume_uint32(p, &ttl) < 0 ||
 476         avahi_dns_packet_consume_uint16(p, &rdlength) < 0 ||
 477         p->rindex + rdlength > p->size)
 478         goto fail;
 479
 480 /*     g_message("name = %s, rdlength = %u", name, rdlength); */
 481
 482     *ret_cache_flush = !!(class & AVAHI_DNS_CACHE_FLUSH);
 483     class &= ~AVAHI_DNS_CACHE_FLUSH;
 484
 485     start = avahi_dns_packet_get_rptr(p);
 486
 487     r = avahi_record_new_full(name, class, type);
 488
 489     switch (type) {
 490         case AVAHI_DNS_TYPE_PTR:
 491         case AVAHI_DNS_TYPE_CNAME:
 492
 493 /*             g_message("ptr"); */
 494
 495             if (avahi_dns_packet_consume_name(p, buf, sizeof(buf)) < 0)
 496                 goto fail;
 497
 498             r->data.ptr.name = g_strdup(buf);
 499             break;
 500
 501
 502         case AVAHI_DNS_TYPE_SRV:
 503
 504 /*             g_message("srv"); */
 505
 506             if (avahi_dns_packet_consume_uint16(p, &r->data.srv.priority) < 0 ||
 507                 avahi_dns_packet_consume_uint16(p, &r->data.srv.weight) < 0 ||
 508                 avahi_dns_packet_consume_uint16(p, &r->data.srv.port) < 0 ||
 509                 avahi_dns_packet_consume_name(p, buf, sizeof(buf)) < 0)
 510                 goto fail;
 511
 512             r->data.srv.name = g_strdup(buf);
 513             break;
 514
 515         case AVAHI_DNS_TYPE_HINFO:
 516
 517 /*             g_message("hinfo"); */
 518
 519             if (avahi_dns_packet_consume_string(p, buf, sizeof(buf)) < 0)
 520                 goto fail;
 521
 522             r->data.hinfo.cpu = g_strdup(buf);
 523
 524             if (avahi_dns_packet_consume_string(p, buf, sizeof(buf)) < 0)
 525                 goto fail;
 526
 527             r->data.hinfo.os = g_strdup(buf);
 528             break;
 529
 530         case AVAHI_DNS_TYPE_TXT:
 531
 532 /*             g_message("txt"); */
 533
 534             if (rdlength > 0) {
 535                 r->data.txt.string_list = avahi_string_list_parse(avahi_dns_packet_get_rptr(p), rdlength);
 536
 537                 if (avahi_dns_packet_skip(p, rdlength) < 0)
 538                     goto fail;
 539             } else
 540                 r->data.txt.string_list = NULL;
 541
 542             break;
 543
 544         case AVAHI_DNS_TYPE_A:
 545
 546 /*             g_message("A"); */
 547
 548             if (avahi_dns_packet_consume_bytes(p, &r->data.a.address, sizeof(AvahiIPv4Address)) < 0)
 549                 goto fail;
 550
 551             break;
 552
 553         case AVAHI_DNS_TYPE_AAAA:
 554
 555 /*             g_message("aaaa"); */
 556
 557             if (avahi_dns_packet_consume_bytes(p, &r->data.aaaa.address, sizeof(AvahiIPv6Address)) < 0)
 558                 goto fail;
 559
 560             break;
 561
 562         default:
 563
 564 /*             g_message("generic"); */
 565
 566             if (rdlength > 0) {
 567
 568                 r->data.generic.data = g_memdup(avahi_dns_packet_get_rptr(p), rdlength);
 569
 570                 if (avahi_dns_packet_skip(p, rdlength) < 0)
 571                     goto fail;
 572             }
 573
 574             break;
 575     }
 576
 577 /*     g_message("%i == %u ?", (guint8*) avahi_dns_packet_get_rptr(p) - (guint8*) start, rdlength); */
 578
 579     /* Check if we read enough data */
 580     if ((guint8*) avahi_dns_packet_get_rptr(p) - (guint8*) start != rdlength)
 581         goto fail;
 582
 583     r->ttl = ttl;
 584
 585     return r;
 586
 587 fail:
 588     if (r)
 589         avahi_record_unref(r);
 590
 591     return NULL;
 592 }
 593
 594 AvahiKey* avahi_dns_packet_consume_key(AvahiDnsPacket *p, gboolean *ret_unicast_response) {
 595     gchar name[256];
 596     guint16 type, class;
 597
 598     g_assert(p);
 599     g_assert(ret_unicast_response);
 600
 601     if (avahi_dns_packet_consume_name(p, name, sizeof(name)) < 0 ||
 602         avahi_dns_packet_consume_uint16(p, &type) < 0 ||
 603         avahi_dns_packet_consume_uint16(p, &class) < 0)
 604         return NULL;
 605
 606     *ret_unicast_response = !!(class & AVAHI_DNS_UNICAST_RESPONSE);
 607     class &= ~AVAHI_DNS_UNICAST_RESPONSE;
 608
 609     return avahi_key_new(name, class, type);
 610 }
 611
 612 guint8* avahi_dns_packet_append_key(AvahiDnsPacket *p, AvahiKey *k, gboolean unicast_response) {
 613     guint8 *t;
 614     guint size;
 615
 616     g_assert(p);
 617     g_assert(k);
 618
 619     size = p->size;
 620
 621     if (!(t = avahi_dns_packet_append_name(p, k->name)) ||
 622         !avahi_dns_packet_append_uint16(p, k->type) ||
 623         !avahi_dns_packet_append_uint16(p, k->class | (unicast_response ? AVAHI_DNS_UNICAST_RESPONSE : 0))) {
 624         p->size = size;
 625         return NULL;
 626     }
 627
 628     return t;
 629 }
 630
 631 guint8* avahi_dns_packet_append_record(AvahiDnsPacket *p, AvahiRecord *r, gboolean cache_flush, guint max_ttl) {
 632     guint8 *t, *l, *start;
 633     guint size;
 634
 635     g_assert(p);
 636     g_assert(r);
 637
 638     size = p->size;
 639
 640     if (!(t = avahi_dns_packet_append_name(p, r->key->name)) ||
 641         !avahi_dns_packet_append_uint16(p, r->key->type) ||
 642         !avahi_dns_packet_append_uint16(p, cache_flush ? (r->key->class | AVAHI_DNS_CACHE_FLUSH) : (r->key->class &~ AVAHI_DNS_CACHE_FLUSH)) ||
 643         !avahi_dns_packet_append_uint32(p, (max_ttl && r->ttl > max_ttl) ? max_ttl : r->ttl) ||
 644         !(l = avahi_dns_packet_append_uint16(p, 0)))
 645         goto fail;
 646
 647     start = avahi_dns_packet_extend(p, 0);
 648
 649     switch (r->key->type) {
 650
 651         case AVAHI_DNS_TYPE_PTR:
 652         case AVAHI_DNS_TYPE_CNAME :
 653
 654             if (!(avahi_dns_packet_append_name(p, r->data.ptr.name)))
 655                 goto fail;
 656
 657             break;
 658
 659         case AVAHI_DNS_TYPE_SRV:
 660
 661             if (!avahi_dns_packet_append_uint16(p, r->data.srv.priority) ||
 662                 !avahi_dns_packet_append_uint16(p, r->data.srv.weight) ||
 663                 !avahi_dns_packet_append_uint16(p, r->data.srv.port) ||
 664                 !avahi_dns_packet_append_name(p, r->data.srv.name))
 665                 goto fail;
 666
 667             break;
 668
 669         case AVAHI_DNS_TYPE_HINFO:
 670             if (!avahi_dns_packet_append_string(p, r->data.hinfo.cpu) ||
 671                 !avahi_dns_packet_append_string(p, r->data.hinfo.os))
 672                 goto fail;
 673
 674             break;
 675
 676         case AVAHI_DNS_TYPE_TXT: {
 677
 678             guint8 *data;
 679             guint size;
 680
 681             size = avahi_string_list_serialize(r->data.txt.string_list, NULL, 0);
 682
 683 /*             g_message("appending string: %u %p", size, r->data.txt.string_list); */
 684
 685             if (!(data = avahi_dns_packet_extend(p, size)))
 686                 goto fail;
 687
 688             avahi_string_list_serialize(r->data.txt.string_list, data, size);
 689             break;
 690         }
 691
 692
 693         case AVAHI_DNS_TYPE_A:
 694
 695             if (!avahi_dns_packet_append_bytes(p, &r->data.a.address, sizeof(r->data.a.address)))
 696                 goto fail;
 697
 698             break;
 699
 700         case AVAHI_DNS_TYPE_AAAA:
 701
 702             if (!avahi_dns_packet_append_bytes(p, &r->data.aaaa.address, sizeof(r->data.aaaa.address)))
 703                 goto fail;
 704
 705             break;
 706
 707         default:
 708
 709             if (r->data.generic.size &&
 710                 avahi_dns_packet_append_bytes(p, r->data.generic.data, r->data.generic.size))
 711                 goto fail;
 712
 713             break;
 714     }
 715
 716
 717
 718
 719     size = avahi_dns_packet_extend(p, 0) - start;
 720     g_assert(size <= 0xFFFF);
 721
 722 /*     g_message("appended %u", size); */
 723
 724     * (guint16*) l = g_htons((guint16) size);
 725
 726     return t;
 727
 728
 729 fail:
 730     p->size = size;
 731     return NULL;
 732 }
 733
 734 gboolean avahi_dns_packet_is_empty(AvahiDnsPacket *p) {
 735     g_assert(p);
 736
 737     return p->size <= AVAHI_DNS_PACKET_HEADER_SIZE;
 738 }
 739
 740 guint avahi_dns_packet_space(AvahiDnsPacket *p) {
 741     g_assert(p);
 742
 743     g_assert(p->size <= p->max_size);
 744
 745     return p->max_size - p->size;
 746 }