git.meshlink.io Git - catta/blob - libavahi-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 #include <netinet/in.h>
  23
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <stdio.h>
  27
  28 #include "dns.h"
  29 #include "util.h"
  30
  31 AvahiDnsPacket* avahi_dns_packet_new(guint max_size) {
  32     AvahiDnsPacket *p;
  33
  34     if (max_size <= 0)
  35         max_size = AVAHI_DNS_PACKET_MAX_SIZE;
  36     else if (max_size < AVAHI_DNS_PACKET_HEADER_SIZE)
  37         max_size = AVAHI_DNS_PACKET_HEADER_SIZE;
  38
  39     p = g_malloc(sizeof(AvahiDnsPacket) + max_size);
  40     p->size = p->rindex = AVAHI_DNS_PACKET_HEADER_SIZE;
  41     p->max_size = max_size;
  42     p->name_table = NULL;
  43
  44     memset(AVAHI_DNS_PACKET_DATA(p), 0, p->size);
  45     return p;
  46 }
  47
  48 AvahiDnsPacket* avahi_dns_packet_new_query(guint max_size) {
  49     AvahiDnsPacket *p;
  50
  51     p = avahi_dns_packet_new(max_size);
  52     avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_FLAGS, AVAHI_DNS_FLAGS(0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
  53     return p;
  54 }
  55
  56 AvahiDnsPacket* avahi_dns_packet_new_response(guint max_size) {
  57     AvahiDnsPacket *p;
  58
  59     p = avahi_dns_packet_new(max_size);
  60     avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_FLAGS, AVAHI_DNS_FLAGS(1, 0, 0, 0, 0, 0, 0, 0, 0, 0));
  61     return p;
  62 }
  63
  64 void avahi_dns_packet_free(AvahiDnsPacket *p) {
  65     g_assert(p);
  66
  67     if (p->name_table)
  68         g_hash_table_destroy(p->name_table);
  69
  70     g_free(p);
  71 }
  72
  73 void avahi_dns_packet_set_field(AvahiDnsPacket *p, guint index, guint16 v) {
  74     g_assert(p);
  75     g_assert(index < AVAHI_DNS_PACKET_HEADER_SIZE);
  76
  77     ((guint16*) AVAHI_DNS_PACKET_DATA(p))[index] = g_htons(v);
  78 }
  79
  80 guint16 avahi_dns_packet_get_field(AvahiDnsPacket *p, guint index) {
  81     g_assert(p);
  82     g_assert(index < AVAHI_DNS_PACKET_HEADER_SIZE);
  83
  84     return g_ntohs(((guint16*) AVAHI_DNS_PACKET_DATA(p))[index]);
  85 }
  86
  87 /* Read the first label from string *name, unescape "\" and write it to dest */
  88 gchar *avahi_unescape_label(gchar *dest, guint size, const gchar **name) {
  89     guint i = 0;
  90     gchar *d;
  91
  92     g_assert(dest);
  93     g_assert(size > 0);
  94     g_assert(name);
  95     g_assert(*name);
  96
  97     d = dest;
  98
  99     for (;;) {
 100         if (i >= size)
 101             return NULL;
 102
 103         if (**name == '.') {
 104             (*name)++;
 105             break;
 106         }
 107
 108         if (**name == 0)
 109             break;
 110
 111         if (**name == '\\') {
 112             (*name) ++;
 113
 114             if (**name == 0)
 115                 break;
 116         }
 117
 118         *(d++) = *((*name) ++);
 119         i++;
 120     }
 121
 122     g_assert(i < size);
 123
 124     *d = 0;
 125
 126     return dest;
 127 }
 128
 129 guint8* avahi_dns_packet_append_name(AvahiDnsPacket *p, const gchar *name) {
 130     guint8 *d, *saved_ptr = NULL;
 131     guint saved_size;
 132
 133     g_assert(p);
 134     g_assert(name);
 135
 136     saved_size = p->size;
 137     saved_ptr = avahi_dns_packet_extend(p, 0);
 138
 139     while (*name) {
 140         guint8* prev;
 141         const gchar *pname;
 142         gchar label[64];
 143
 144         /* Check whether we can compress this name. */
 145
 146         if (p->name_table && (prev = g_hash_table_lookup(p->name_table, name))) {
 147             guint index;
 148
 149             g_assert(prev >= AVAHI_DNS_PACKET_DATA(p));
 150             index = (guint) (prev - AVAHI_DNS_PACKET_DATA(p));
 151
 152             g_assert(index < p->size);
 153
 154             if (index < 0x4000) {
 155                 guint16 *t;
 156                 if (!(t = (guint16*) avahi_dns_packet_extend(p, sizeof(guint16))))
 157                     return NULL;
 158
 159                 *t = g_htons((0xC000 | index));
 160                 return saved_ptr;
 161             }
 162         }
 163
 164         pname = name;
 165
 166         if (!(avahi_unescape_label(label, sizeof(label), &name)))
 167             goto fail;
 168
 169         if (!(d = avahi_dns_packet_append_string(p, label)))
 170             goto fail;
 171
 172         if (!p->name_table)
 173             p->name_table = g_hash_table_new_full((GHashFunc) avahi_domain_hash, (GEqualFunc) avahi_domain_equal, g_free, NULL);
 174
 175         g_hash_table_insert(p->name_table, g_strdup(pname), d);
 176     }
 177
 178     if (!(d = avahi_dns_packet_extend(p, 1)))
 179         goto fail;
 180
 181     *d = 0;
 182
 183     return saved_ptr;
 184
 185 fail:
 186     p->size = saved_size;
 187     return NULL;
 188 }
 189
 190 guint8* avahi_dns_packet_append_uint16(AvahiDnsPacket *p, guint16 v) {
 191     guint8 *d;
 192     g_assert(p);
 193
 194     if (!(d = avahi_dns_packet_extend(p, sizeof(guint16))))
 195         return NULL;
 196
 197     *((guint16*) d) = g_htons(v);
 198     return d;
 199 }
 200
 201 guint8 *avahi_dns_packet_append_uint32(AvahiDnsPacket *p, guint32 v) {
 202     guint8 *d;
 203     g_assert(p);
 204
 205     if (!(d = avahi_dns_packet_extend(p, sizeof(guint32))))
 206         return NULL;
 207
 208     *((guint32*) d) = g_htonl(v);
 209
 210     return d;
 211 }
 212
 213 guint8 *avahi_dns_packet_append_bytes(AvahiDnsPacket  *p, gconstpointer b, guint l) {
 214     guint8* d;
 215
 216     g_assert(p);
 217     g_assert(b);
 218     g_assert(l);
 219
 220     if (!(d = avahi_dns_packet_extend(p, l)))
 221         return NULL;
 222
 223     memcpy(d, b, l);
 224     return d;
 225 }
 226
 227 guint8* avahi_dns_packet_append_string(AvahiDnsPacket *p, const gchar *s) {
 228     guint8* d;
 229     guint k;
 230
 231     g_assert(p);
 232     g_assert(s);
 233
 234     if ((k = strlen(s)) >= 255)
 235         k = 255;
 236
 237     if (!(d = avahi_dns_packet_extend(p, k+1)))
 238         return NULL;
 239
 240     *d = (guint8) k;
 241     memcpy(d+1, s, k);
 242
 243     return d;
 244 }
 245
 246 guint8 *avahi_dns_packet_extend(AvahiDnsPacket *p, guint l) {
 247     guint8 *d;
 248
 249     g_assert(p);
 250
 251     if (p->size+l > p->max_size)
 252         return NULL;
 253
 254     d = AVAHI_DNS_PACKET_DATA(p) + p->size;
 255     p->size += l;
 256
 257     return d;
 258 }
 259
 260 gint avahi_dns_packet_check_valid(AvahiDnsPacket *p) {
 261     guint16 flags;
 262     g_assert(p);
 263
 264     if (p->size < 12)
 265         return -1;
 266
 267     flags = avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS);
 268
 269     if (flags & AVAHI_DNS_FLAG_OPCODE || flags & AVAHI_DNS_FLAG_RCODE)
 270         return -1;
 271
 272     return 0;
 273 }
 274
 275 gint avahi_dns_packet_is_query(AvahiDnsPacket *p) {
 276     g_assert(p);
 277
 278     return !(avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS) & AVAHI_DNS_FLAG_QR);
 279 }
 280
 281 /* Read a label from a DNS packet, escape "\" and ".", append \0 */
 282 static gchar *escape_label(guint8* src, guint src_length, gchar **ret_name, guint *ret_name_length) {
 283     gchar *r;
 284
 285     g_assert(src);
 286     g_assert(ret_name);
 287     g_assert(*ret_name);
 288     g_assert(ret_name_length);
 289     g_assert(*ret_name_length > 0);
 290
 291     r = *ret_name;
 292
 293     while (src_length > 0) {
 294         if (*src == '.' || *src == '\\') {
 295             if (*ret_name_length < 3)
 296                 return NULL;
 297
 298             *((*ret_name) ++) = '\\';
 299             (*ret_name_length) --;
 300         }
 301
 302         if (*ret_name_length < 2)
 303             return NULL;
 304
 305         *((*ret_name)++) = *src;
 306         (*ret_name_length) --;
 307
 308         src_length --;
 309         src++;
 310     }
 311
 312     **ret_name = 0;
 313
 314     return r;
 315 }
 316
 317 static gint consume_labels(AvahiDnsPacket *p, guint index, gchar *ret_name, guint l) {
 318     gint ret = 0;
 319     int compressed = 0;
 320     int first_label = 1;
 321     g_assert(p && ret_name && l);
 322
 323     for (;;) {
 324         guint8 n;
 325
 326         if (index+1 > p->size)
 327             return -1;
 328
 329         n = AVAHI_DNS_PACKET_DATA(p)[index];
 330
 331         if (!n) {
 332             index++;
 333             if (!compressed)
 334                 ret++;
 335
 336             if (l < 1)
 337                 return -1;
 338             *ret_name = 0;
 339
 340             return ret;
 341
 342         } else if (n <= 63) {
 343             /* Uncompressed label */
 344             index++;
 345             if (!compressed)
 346                 ret++;
 347
 348             if (index + n > p->size)
 349                 return -1;
 350
 351             if ((guint) n + 1 > l)
 352                 return -1;
 353
 354             if (!first_label) {
 355                 *(ret_name++) = '.';
 356                 l--;
 357             } else
 358                 first_label = 0;
 359
 360             if (!(escape_label(AVAHI_DNS_PACKET_DATA(p) + index, n, &ret_name, &l)))
 361                 return -1;
 362
 363             index += n;
 364
 365             if (!compressed)
 366                 ret += n;
 367         } else if ((n & 0xC0) == 0xC0) {
 368             /* Compressed label */
 369
 370             if (index+2 > p->size)
 371                 return -1;
 372
 373             index = ((guint) (AVAHI_DNS_PACKET_DATA(p)[index] & ~0xC0)) << 8 | AVAHI_DNS_PACKET_DATA(p)[index+1];
 374
 375             if (!compressed)
 376                 ret += 2;
 377
 378             compressed = 1;
 379         } else
 380             return -1;
 381     }
 382 }
 383
 384 gint avahi_dns_packet_consume_name(AvahiDnsPacket *p, gchar *ret_name, guint l) {
 385     gint r;
 386
 387     if ((r = consume_labels(p, p->rindex, ret_name, l)) < 0)
 388         return -1;
 389
 390     p->rindex += r;
 391     return 0;
 392 }
 393
 394 gint avahi_dns_packet_consume_uint16(AvahiDnsPacket *p, guint16 *ret_v) {
 395     g_assert(p);
 396     g_assert(ret_v);
 397
 398     if (p->rindex + sizeof(guint16) > p->size)
 399         return -1;
 400
 401     *ret_v = g_ntohs(*((guint16*) (AVAHI_DNS_PACKET_DATA(p) + p->rindex)));
 402     p->rindex += sizeof(guint16);
 403
 404     return 0;
 405 }
 406
 407 gint avahi_dns_packet_consume_uint32(AvahiDnsPacket *p, guint32 *ret_v) {
 408     g_assert(p);
 409     g_assert(ret_v);
 410
 411     if (p->rindex + sizeof(guint32) > p->size)
 412         return -1;
 413
 414     *ret_v = g_ntohl(*((guint32*) (AVAHI_DNS_PACKET_DATA(p) + p->rindex)));
 415     p->rindex += sizeof(guint32);
 416
 417     return 0;
 418 }
 419
 420 gint avahi_dns_packet_consume_bytes(AvahiDnsPacket *p, gpointer ret_data, guint l) {
 421     g_assert(p);
 422     g_assert(ret_data);
 423     g_assert(l > 0);
 424
 425     if (p->rindex + l > p->size)
 426         return -1;
 427
 428     memcpy(ret_data, AVAHI_DNS_PACKET_DATA(p) + p->rindex, l);
 429     p->rindex += l;
 430
 431     return 0;
 432 }
 433
 434 gint avahi_dns_packet_consume_string(AvahiDnsPacket *p, gchar *ret_string, guint l) {
 435     guint k;
 436
 437     g_assert(p);
 438     g_assert(ret_string);
 439     g_assert(l > 0);
 440
 441     if (p->rindex >= p->size)
 442         return -1;
 443
 444     k = AVAHI_DNS_PACKET_DATA(p)[p->rindex];
 445
 446     if (p->rindex+1+k > p->size)
 447         return -1;
 448
 449     if (l > k+1)
 450         l = k+1;
 451
 452     memcpy(ret_string, AVAHI_DNS_PACKET_DATA(p)+p->rindex+1, l-1);
 453     ret_string[l-1] = 0;
 454
 455
 456     p->rindex += 1+k;
 457
 458     return 0;
 459
 460 }
 461
 462 gconstpointer avahi_dns_packet_get_rptr(AvahiDnsPacket *p) {
 463     g_assert(p);
 464
 465     if (p->rindex > p->size)
 466         return NULL;
 467
 468     return AVAHI_DNS_PACKET_DATA(p) + p->rindex;
 469 }
 470
 471 gint avahi_dns_packet_skip(AvahiDnsPacket *p, guint length) {
 472     g_assert(p);
 473
 474     if (p->rindex + length > p->size)
 475         return -1;
 476
 477     p->rindex += length;
 478     return 0;
 479 }
 480
 481 AvahiRecord* avahi_dns_packet_consume_record(AvahiDnsPacket *p, gboolean *ret_cache_flush) {
 482     gchar name[257], buf[257];
 483     guint16 type, class;
 484     guint32 ttl;
 485     guint16 rdlength;
 486     AvahiRecord *r = NULL;
 487     gconstpointer start;
 488
 489     g_assert(p);
 490     g_assert(ret_cache_flush);
 491
 492 /*     g_message("consume_record()"); */
 493
 494     if (avahi_dns_packet_consume_name(p, name, sizeof(name)) < 0 ||
 495         avahi_dns_packet_consume_uint16(p, &type) < 0 ||
 496         avahi_dns_packet_consume_uint16(p, &class) < 0 ||
 497         avahi_dns_packet_consume_uint32(p, &ttl) < 0 ||
 498         avahi_dns_packet_consume_uint16(p, &rdlength) < 0 ||
 499         p->rindex + rdlength > p->size)
 500         goto fail;
 501
 502 /*     g_message("name = %s, rdlength = %u", name, rdlength); */
 503
 504     *ret_cache_flush = !!(class & AVAHI_DNS_CACHE_FLUSH);
 505     class &= ~AVAHI_DNS_CACHE_FLUSH;
 506
 507     start = avahi_dns_packet_get_rptr(p);
 508
 509     r = avahi_record_new_full(name, class, type);
 510
 511     switch (type) {
 512         case AVAHI_DNS_TYPE_PTR:
 513         case AVAHI_DNS_TYPE_CNAME:
 514
 515 /*             g_message("ptr"); */
 516
 517             if (avahi_dns_packet_consume_name(p, buf, sizeof(buf)) < 0)
 518                 goto fail;
 519
 520             r->data.ptr.name = g_strdup(buf);
 521             break;
 522
 523
 524         case AVAHI_DNS_TYPE_SRV:
 525
 526 /*             g_message("srv"); */
 527
 528             if (avahi_dns_packet_consume_uint16(p, &r->data.srv.priority) < 0 ||
 529                 avahi_dns_packet_consume_uint16(p, &r->data.srv.weight) < 0 ||
 530                 avahi_dns_packet_consume_uint16(p, &r->data.srv.port) < 0 ||
 531                 avahi_dns_packet_consume_name(p, buf, sizeof(buf)) < 0)
 532                 goto fail;
 533
 534             r->data.srv.name = g_strdup(buf);
 535             break;
 536
 537         case AVAHI_DNS_TYPE_HINFO:
 538
 539 /*             g_message("hinfo"); */
 540
 541             if (avahi_dns_packet_consume_string(p, buf, sizeof(buf)) < 0)
 542                 goto fail;
 543
 544             r->data.hinfo.cpu = g_strdup(buf);
 545
 546             if (avahi_dns_packet_consume_string(p, buf, sizeof(buf)) < 0)
 547                 goto fail;
 548
 549             r->data.hinfo.os = g_strdup(buf);
 550             break;
 551
 552         case AVAHI_DNS_TYPE_TXT:
 553
 554 /*             g_message("txt"); */
 555
 556             if (rdlength > 0) {
 557                 r->data.txt.string_list = avahi_string_list_parse(avahi_dns_packet_get_rptr(p), rdlength);
 558
 559                 if (avahi_dns_packet_skip(p, rdlength) < 0)
 560                     goto fail;
 561             } else
 562                 r->data.txt.string_list = NULL;
 563
 564             break;
 565
 566         case AVAHI_DNS_TYPE_A:
 567
 568 /*             g_message("A"); */
 569
 570             if (avahi_dns_packet_consume_bytes(p, &r->data.a.address, sizeof(AvahiIPv4Address)) < 0)
 571                 goto fail;
 572
 573             break;
 574
 575         case AVAHI_DNS_TYPE_AAAA:
 576
 577 /*             g_message("aaaa"); */
 578
 579             if (avahi_dns_packet_consume_bytes(p, &r->data.aaaa.address, sizeof(AvahiIPv6Address)) < 0)
 580                 goto fail;
 581
 582             break;
 583
 584         default:
 585
 586 /*             g_message("generic"); */
 587
 588             if (rdlength > 0) {
 589
 590                 r->data.generic.data = g_memdup(avahi_dns_packet_get_rptr(p), rdlength);
 591
 592                 if (avahi_dns_packet_skip(p, rdlength) < 0)
 593                     goto fail;
 594             }
 595
 596             break;
 597     }
 598
 599 /*     g_message("%i == %u ?", (guint8*) avahi_dns_packet_get_rptr(p) - (guint8*) start, rdlength); */
 600
 601     /* Check if we read enough data */
 602     if ((guint8*) avahi_dns_packet_get_rptr(p) - (guint8*) start != rdlength)
 603         goto fail;
 604
 605     r->ttl = ttl;
 606
 607     return r;
 608
 609 fail:
 610     if (r)
 611         avahi_record_unref(r);
 612
 613     return NULL;
 614 }
 615
 616 AvahiKey* avahi_dns_packet_consume_key(AvahiDnsPacket *p, gboolean *ret_unicast_response) {
 617     gchar name[256];
 618     guint16 type, class;
 619
 620     g_assert(p);
 621     g_assert(ret_unicast_response);
 622
 623     if (avahi_dns_packet_consume_name(p, name, sizeof(name)) < 0 ||
 624         avahi_dns_packet_consume_uint16(p, &type) < 0 ||
 625         avahi_dns_packet_consume_uint16(p, &class) < 0)
 626         return NULL;
 627
 628     *ret_unicast_response = !!(class & AVAHI_DNS_UNICAST_RESPONSE);
 629     class &= ~AVAHI_DNS_UNICAST_RESPONSE;
 630
 631     return avahi_key_new(name, class, type);
 632 }
 633
 634 guint8* avahi_dns_packet_append_key(AvahiDnsPacket *p, AvahiKey *k, gboolean unicast_response) {
 635     guint8 *t;
 636     guint size;
 637
 638     g_assert(p);
 639     g_assert(k);
 640
 641     size = p->size;
 642
 643     if (!(t = avahi_dns_packet_append_name(p, k->name)) ||
 644         !avahi_dns_packet_append_uint16(p, k->type) ||
 645         !avahi_dns_packet_append_uint16(p, k->class | (unicast_response ? AVAHI_DNS_UNICAST_RESPONSE : 0))) {
 646         p->size = size;
 647         return NULL;
 648     }
 649
 650     return t;
 651 }
 652
 653 guint8* avahi_dns_packet_append_record(AvahiDnsPacket *p, AvahiRecord *r, gboolean cache_flush) {
 654     guint8 *t, *l, *start;
 655     guint size;
 656
 657     g_assert(p);
 658     g_assert(r);
 659
 660     size = p->size;
 661
 662     if (!(t = avahi_dns_packet_append_name(p, r->key->name)) ||
 663         !avahi_dns_packet_append_uint16(p, r->key->type) ||
 664         !avahi_dns_packet_append_uint16(p, cache_flush ? (r->key->class | AVAHI_DNS_CACHE_FLUSH) : (r->key->class &~ AVAHI_DNS_CACHE_FLUSH)) ||
 665         !avahi_dns_packet_append_uint32(p, r->ttl) ||
 666         !(l = avahi_dns_packet_append_uint16(p, 0)))
 667         goto fail;
 668
 669     start = avahi_dns_packet_extend(p, 0);
 670
 671     switch (r->key->type) {
 672
 673         case AVAHI_DNS_TYPE_PTR:
 674         case AVAHI_DNS_TYPE_CNAME :
 675
 676             if (!(avahi_dns_packet_append_name(p, r->data.ptr.name)))
 677                 goto fail;
 678
 679             break;
 680
 681         case AVAHI_DNS_TYPE_SRV:
 682
 683             if (!avahi_dns_packet_append_uint16(p, r->data.srv.priority) ||
 684                 !avahi_dns_packet_append_uint16(p, r->data.srv.weight) ||
 685                 !avahi_dns_packet_append_uint16(p, r->data.srv.port) ||
 686                 !avahi_dns_packet_append_name(p, r->data.srv.name))
 687                 goto fail;
 688
 689             break;
 690
 691         case AVAHI_DNS_TYPE_HINFO:
 692             if (!avahi_dns_packet_append_string(p, r->data.hinfo.cpu) ||
 693                 !avahi_dns_packet_append_string(p, r->data.hinfo.os))
 694                 goto fail;
 695
 696             break;
 697
 698         case AVAHI_DNS_TYPE_TXT: {
 699
 700             guint8 *data;
 701             guint size;
 702
 703             size = avahi_string_list_serialize(r->data.txt.string_list, NULL, 0);
 704
 705 /*             g_message("appending string: %u %p", size, r->data.txt.string_list); */
 706
 707             if (!(data = avahi_dns_packet_extend(p, size)))
 708                 goto fail;
 709
 710             avahi_string_list_serialize(r->data.txt.string_list, data, size);
 711             break;
 712         }
 713
 714
 715         case AVAHI_DNS_TYPE_A:
 716
 717             if (!avahi_dns_packet_append_bytes(p, &r->data.a.address, sizeof(r->data.a.address)))
 718                 goto fail;
 719
 720             break;
 721
 722         case AVAHI_DNS_TYPE_AAAA:
 723
 724             if (!avahi_dns_packet_append_bytes(p, &r->data.aaaa.address, sizeof(r->data.aaaa.address)))
 725                 goto fail;
 726
 727             break;
 728
 729         default:
 730
 731             if (r->data.generic.size &&
 732                 avahi_dns_packet_append_bytes(p, r->data.generic.data, r->data.generic.size))
 733                 goto fail;
 734
 735             break;
 736     }
 737
 738
 739
 740
 741     size = avahi_dns_packet_extend(p, 0) - start;
 742     g_assert(size <= 0xFFFF);
 743
 744 /*     g_message("appended %u", size); */
 745
 746     * (guint16*) l = g_htons((guint16) size);
 747
 748     return t;
 749
 750
 751 fail:
 752     p->size = size;
 753     return NULL;
 754 }
 755
 756 gboolean avahi_dns_packet_is_empty(AvahiDnsPacket *p) {
 757     g_assert(p);
 758
 759     return p->size <= AVAHI_DNS_PACKET_HEADER_SIZE;
 760 }
 761
 762 guint avahi_dns_packet_space(AvahiDnsPacket *p) {
 763     g_assert(p);
 764
 765     g_assert(p->size <= p->max_size);
 766
 767     return p->max_size - p->size;
 768 }