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