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 #include <assert.h>
  32
  33 #include <avahi-common/domain.h>
  34 #include <avahi-common/malloc.h>
  35
  36 #include "dns.h"
  37 #include "log.h"
  38
  39 AvahiDnsPacket* avahi_dns_packet_new(unsigned mtu) {
  40     AvahiDnsPacket *p;
  41     size_t max_size;
  42
  43     if (mtu <= 0)
  44         max_size = AVAHI_DNS_PACKET_MAX_SIZE;
  45     else if (mtu >= AVAHI_DNS_PACKET_EXTRA_SIZE)
  46         max_size = mtu - AVAHI_DNS_PACKET_EXTRA_SIZE;
  47     else
  48         max_size = 0;
  49
  50     if (max_size < AVAHI_DNS_PACKET_HEADER_SIZE)
  51         max_size = AVAHI_DNS_PACKET_HEADER_SIZE;
  52
  53     if (!(p = avahi_malloc(sizeof(AvahiDnsPacket) + max_size)))
  54         return p;
  55
  56     p->size = p->rindex = AVAHI_DNS_PACKET_HEADER_SIZE;
  57     p->max_size = max_size;
  58     p->name_table = NULL;
  59
  60     memset(AVAHI_DNS_PACKET_DATA(p), 0, p->size);
  61     return p;
  62 }
  63
  64 AvahiDnsPacket* avahi_dns_packet_new_query(unsigned mtu) {
  65     AvahiDnsPacket *p;
  66
  67     if (!(p = avahi_dns_packet_new(mtu)))
  68         return NULL;
  69
  70     avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_FLAGS, AVAHI_DNS_FLAGS(0, 0, 0, 0, 0, 0, 0, 0, 0, 0));
  71     return p;
  72 }
  73
  74 AvahiDnsPacket* avahi_dns_packet_new_response(unsigned mtu, int aa) {
  75     AvahiDnsPacket *p;
  76
  77     if (!(p = avahi_dns_packet_new(mtu)))
  78         return NULL;
  79
  80     avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_FLAGS, AVAHI_DNS_FLAGS(1, 0, aa, 0, 0, 0, 0, 0, 0, 0));
  81     return p;
  82 }
  83
  84 AvahiDnsPacket* avahi_dns_packet_new_reply(AvahiDnsPacket* p, unsigned mtu, int copy_queries, int aa) {
  85     AvahiDnsPacket *r;
  86     assert(p);
  87
  88     if (!(r = avahi_dns_packet_new_response(mtu, aa)))
  89         return NULL;
  90
  91     if (copy_queries) {
  92         unsigned saved_rindex;
  93         uint32_t n;
  94
  95         saved_rindex = p->rindex;
  96         p->rindex = AVAHI_DNS_PACKET_HEADER_SIZE;
  97
  98         for (n = avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_QDCOUNT); n > 0; n--) {
  99             AvahiKey *k;
 100             int unicast_response;
 101
 102             if ((k = avahi_dns_packet_consume_key(p, &unicast_response))) {
 103                 avahi_dns_packet_append_key(r, k, unicast_response);
 104                 avahi_key_unref(k);
 105             }
 106         }
 107
 108         p->rindex = saved_rindex;
 109
 110         avahi_dns_packet_set_field(r, AVAHI_DNS_FIELD_QDCOUNT, avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_QDCOUNT));
 111     }
 112
 113     avahi_dns_packet_set_field(r, AVAHI_DNS_FIELD_ID, avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_ID));
 114
 115     avahi_dns_packet_set_field(r, AVAHI_DNS_FIELD_FLAGS,
 116                                (avahi_dns_packet_get_field(r, AVAHI_DNS_FIELD_FLAGS) & ~AVAHI_DNS_FLAG_OPCODE) |
 117                                (avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS) & AVAHI_DNS_FLAG_OPCODE));
 118
 119     return r;
 120 }
 121
 122
 123 void avahi_dns_packet_free(AvahiDnsPacket *p) {
 124     assert(p);
 125
 126     if (p->name_table)
 127         avahi_hashmap_free(p->name_table);
 128
 129     avahi_free(p);
 130 }
 131
 132 void avahi_dns_packet_set_field(AvahiDnsPacket *p, unsigned idx, uint16_t v) {
 133     assert(p);
 134     assert(idx < AVAHI_DNS_PACKET_HEADER_SIZE);
 135
 136     ((uint16_t*) AVAHI_DNS_PACKET_DATA(p))[idx] = htons(v);
 137 }
 138
 139 uint16_t avahi_dns_packet_get_field(AvahiDnsPacket *p, unsigned idx) {
 140     assert(p);
 141     assert(idx < AVAHI_DNS_PACKET_HEADER_SIZE);
 142
 143     return ntohs(((uint16_t*) AVAHI_DNS_PACKET_DATA(p))[idx]);
 144 }
 145
 146 void avahi_dns_packet_inc_field(AvahiDnsPacket *p, unsigned idx) {
 147     assert(p);
 148     assert(idx < AVAHI_DNS_PACKET_HEADER_SIZE);
 149
 150     avahi_dns_packet_set_field(p, idx, avahi_dns_packet_get_field(p, idx) + 1);
 151 }
 152
 153 uint8_t* avahi_dns_packet_append_name(AvahiDnsPacket *p, const char *name) {
 154     uint8_t *d, *saved_ptr = NULL;
 155     size_t saved_size;
 156
 157     assert(p);
 158     assert(name);
 159
 160     saved_size = p->size;
 161     saved_ptr = avahi_dns_packet_extend(p, 0);
 162
 163     while (*name) {
 164         uint8_t* prev;
 165         const char *pname;
 166         char label[64], *u;
 167
 168         /* Check whether we can compress this name. */
 169
 170         if (p->name_table && (prev = avahi_hashmap_lookup(p->name_table, name))) {
 171             unsigned idx;
 172
 173             assert(prev >= AVAHI_DNS_PACKET_DATA(p));
 174             idx = (unsigned) (prev - AVAHI_DNS_PACKET_DATA(p));
 175
 176             assert(idx < p->size);
 177
 178             if (idx < 0x4000) {
 179                 uint8_t *t;
 180                 if (!(t = (uint8_t*) avahi_dns_packet_extend(p, sizeof(uint16_t))))
 181                     return NULL;
 182
 183                 t[0] = (uint8_t) ((0xC000 | idx) >> 8);
 184                 t[1] = (uint8_t) idx;
 185                 return saved_ptr;
 186             }
 187         }
 188
 189         pname = name;
 190
 191         if (!(avahi_unescape_label(&name, label, sizeof(label))))
 192             goto fail;
 193
 194         if (!(d = avahi_dns_packet_append_string(p, label)))
 195             goto fail;
 196
 197         if (!p->name_table)
 198             /* This works only for normalized domain names */
 199             p->name_table = avahi_hashmap_new(avahi_string_hash, avahi_string_equal, avahi_free, NULL);
 200
 201         if (!(u = avahi_strdup(pname)))
 202             avahi_log_error("avahi_strdup() failed.");
 203         else
 204             avahi_hashmap_insert(p->name_table, u, d);
 205     }
 206
 207     if (!(d = avahi_dns_packet_extend(p, 1)))
 208         goto fail;
 209
 210     *d = 0;
 211
 212     return saved_ptr;
 213
 214 fail:
 215     p->size = saved_size;
 216     return NULL;
 217 }
 218
 219 uint8_t* avahi_dns_packet_append_uint16(AvahiDnsPacket *p, uint16_t v) {
 220     uint8_t *d;
 221     assert(p);
 222
 223     if (!(d = avahi_dns_packet_extend(p, sizeof(uint16_t))))
 224         return NULL;
 225
 226     d[0] = (uint8_t) (v >> 8);
 227     d[1] = (uint8_t) v;
 228     return d;
 229 }
 230
 231 uint8_t *avahi_dns_packet_append_uint32(AvahiDnsPacket *p, uint32_t v) {
 232     uint8_t *d;
 233     assert(p);
 234
 235     if (!(d = avahi_dns_packet_extend(p, sizeof(uint32_t))))
 236         return NULL;
 237
 238     d[0] = (uint8_t) (v >> 24);
 239     d[1] = (uint8_t) (v >> 16);
 240     d[2] = (uint8_t) (v >> 8);
 241     d[3] = (uint8_t) v;
 242
 243     return d;
 244 }
 245
 246 uint8_t *avahi_dns_packet_append_bytes(AvahiDnsPacket  *p, const void *b, size_t l) {
 247     uint8_t* d;
 248
 249     assert(p);
 250     assert(b);
 251     assert(l);
 252
 253     if (!(d = avahi_dns_packet_extend(p, l)))
 254         return NULL;
 255
 256     memcpy(d, b, l);
 257     return d;
 258 }
 259
 260 uint8_t* avahi_dns_packet_append_string(AvahiDnsPacket *p, const char *s) {
 261     uint8_t* d;
 262     size_t k;
 263
 264     assert(p);
 265     assert(s);
 266
 267     if ((k = strlen(s)) >= 255)
 268         k = 255;
 269
 270     if (!(d = avahi_dns_packet_extend(p, k+1)))
 271         return NULL;
 272
 273     *d = (uint8_t) k;
 274     memcpy(d+1, s, k);
 275
 276     return d;
 277 }
 278
 279 uint8_t *avahi_dns_packet_extend(AvahiDnsPacket *p, size_t l) {
 280     uint8_t *d;
 281
 282     assert(p);
 283
 284     if (p->size+l > p->max_size)
 285         return NULL;
 286
 287     d = AVAHI_DNS_PACKET_DATA(p) + p->size;
 288     p->size += l;
 289
 290     return d;
 291 }
 292
 293 int avahi_dns_packet_check_valid(AvahiDnsPacket *p) {
 294     uint16_t flags;
 295     assert(p);
 296
 297     if (p->size < AVAHI_DNS_PACKET_HEADER_SIZE)
 298         return -1;
 299
 300     flags = avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS);
 301
 302     if (flags & AVAHI_DNS_FLAG_OPCODE)
 303         return -1;
 304
 305     return 0;
 306 }
 307
 308 int avahi_dns_packet_check_valid_multicast(AvahiDnsPacket *p) {
 309     uint16_t flags;
 310     assert(p);
 311
 312     if (avahi_dns_packet_check_valid(p) < 0)
 313         return -1;
 314
 315     flags = avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS);
 316
 317     if (flags & AVAHI_DNS_FLAG_RCODE)
 318         return -1;
 319
 320     return 0;
 321 }
 322
 323
 324 int avahi_dns_packet_is_query(AvahiDnsPacket *p) {
 325     assert(p);
 326
 327     return !(avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS) & AVAHI_DNS_FLAG_QR);
 328 }
 329
 330 static int consume_labels(AvahiDnsPacket *p, unsigned idx, char *ret_name, size_t l) {
 331     int ret = 0;
 332     int compressed = 0;
 333     int first_label = 1;
 334     assert(p && ret_name && l);
 335
 336     for (;;) {
 337         uint8_t n;
 338
 339         if (idx+1 > p->size)
 340             return -1;
 341
 342         n = AVAHI_DNS_PACKET_DATA(p)[idx];
 343
 344         if (!n) {
 345             idx++;
 346             if (!compressed)
 347                 ret++;
 348
 349             if (l < 1)
 350                 return -1;
 351             *ret_name = 0;
 352
 353             return ret;
 354
 355         } else if (n <= 63) {
 356             /* Uncompressed label */
 357             idx++;
 358             if (!compressed)
 359                 ret++;
 360
 361             if (idx + n > p->size)
 362                 return -1;
 363
 364             if ((size_t) n + 1 > l)
 365                 return -1;
 366
 367             if (!first_label) {
 368                 *(ret_name++) = '.';
 369                 l--;
 370             } else
 371                 first_label = 0;
 372
 373             if (!(avahi_escape_label((char*) AVAHI_DNS_PACKET_DATA(p) + idx, n, &ret_name, &l)))
 374                 return -1;
 375
 376             idx += n;
 377
 378             if (!compressed)
 379                 ret += n;
 380         } else if ((n & 0xC0) == 0xC0) {
 381             /* Compressed label */
 382
 383             if (idx+2 > p->size)
 384                 return -1;
 385
 386             idx = ((unsigned) (AVAHI_DNS_PACKET_DATA(p)[idx] & ~0xC0)) << 8 | AVAHI_DNS_PACKET_DATA(p)[idx+1];
 387
 388             if (!compressed)
 389                 ret += 2;
 390
 391             compressed = 1;
 392         } else
 393             return -1;
 394     }
 395 }
 396
 397 int avahi_dns_packet_consume_name(AvahiDnsPacket *p, char *ret_name, size_t l) {
 398     int r;
 399
 400     if ((r = consume_labels(p, p->rindex, ret_name, l)) < 0)
 401         return -1;
 402
 403     p->rindex += r;
 404     return 0;
 405 }
 406
 407 int avahi_dns_packet_consume_uint16(AvahiDnsPacket *p, uint16_t *ret_v) {
 408     uint8_t *d;
 409
 410     assert(p);
 411     assert(ret_v);
 412
 413     if (p->rindex + sizeof(uint16_t) > p->size)
 414         return -1;
 415
 416     d = (uint8_t*) (AVAHI_DNS_PACKET_DATA(p) + p->rindex);
 417     *ret_v = (d[0] << 8) | d[1];
 418     p->rindex += sizeof(uint16_t);
 419
 420     return 0;
 421 }
 422
 423 int avahi_dns_packet_consume_uint32(AvahiDnsPacket *p, uint32_t *ret_v) {
 424     uint8_t* d;
 425
 426     assert(p);
 427     assert(ret_v);
 428
 429     if (p->rindex + sizeof(uint32_t) > p->size)
 430         return -1;
 431
 432     d = (uint8_t*) (AVAHI_DNS_PACKET_DATA(p) + p->rindex);
 433     *ret_v = (d[0] << 24) | (d[1] << 16) | (d[2] << 8) | d[3];
 434     p->rindex += sizeof(uint32_t);
 435
 436     return 0;
 437 }
 438
 439 int avahi_dns_packet_consume_bytes(AvahiDnsPacket *p, void * ret_data, size_t l) {
 440     assert(p);
 441     assert(ret_data);
 442     assert(l > 0);
 443
 444     if (p->rindex + l > p->size)
 445         return -1;
 446
 447     memcpy(ret_data, AVAHI_DNS_PACKET_DATA(p) + p->rindex, l);
 448     p->rindex += l;
 449
 450     return 0;
 451 }
 452
 453 int avahi_dns_packet_consume_string(AvahiDnsPacket *p, char *ret_string, size_t l) {
 454     size_t k;
 455
 456     assert(p);
 457     assert(ret_string);
 458     assert(l > 0);
 459
 460     if (p->rindex >= p->size)
 461         return -1;
 462
 463     k = AVAHI_DNS_PACKET_DATA(p)[p->rindex];
 464
 465     if (p->rindex+1+k > p->size)
 466         return -1;
 467
 468     if (l > k+1)
 469         l = k+1;
 470
 471     memcpy(ret_string, AVAHI_DNS_PACKET_DATA(p)+p->rindex+1, l-1);
 472     ret_string[l-1] = 0;
 473
 474     p->rindex += 1+k;
 475
 476     return 0;
 477 }
 478
 479 const void* avahi_dns_packet_get_rptr(AvahiDnsPacket *p) {
 480     assert(p);
 481
 482     if (p->rindex > p->size)
 483         return NULL;
 484
 485     return AVAHI_DNS_PACKET_DATA(p) + p->rindex;
 486 }
 487
 488 int avahi_dns_packet_skip(AvahiDnsPacket *p, size_t length) {
 489     assert(p);
 490
 491     if (p->rindex + length > p->size)
 492         return -1;
 493
 494     p->rindex += length;
 495     return 0;
 496 }
 497
 498 AvahiRecord* avahi_dns_packet_consume_record(AvahiDnsPacket *p, int *ret_cache_flush) {
 499     char name[257], buf[257];
 500     uint16_t type, class;
 501     uint32_t ttl;
 502     uint16_t rdlength;
 503     AvahiRecord *r = NULL;
 504     const void* start;
 505
 506     assert(p);
 507
 508 /*     avahi_log_debug("consume_record()"); */
 509
 510     if (avahi_dns_packet_consume_name(p, name, sizeof(name)) < 0 ||
 511         avahi_dns_packet_consume_uint16(p, &type) < 0 ||
 512         avahi_dns_packet_consume_uint16(p, &class) < 0 ||
 513         avahi_dns_packet_consume_uint32(p, &ttl) < 0 ||
 514         avahi_dns_packet_consume_uint16(p, &rdlength) < 0 ||
 515         p->rindex + rdlength > p->size)
 516         goto fail;
 517
 518 /*     avahi_log_debug("name = %s, rdlength = %u", name, rdlength); */
 519
 520     if (ret_cache_flush)
 521         *ret_cache_flush = !!(class & AVAHI_DNS_CACHE_FLUSH);
 522     class &= ~AVAHI_DNS_CACHE_FLUSH;
 523
 524     start = avahi_dns_packet_get_rptr(p);
 525
 526     if (!(r = avahi_record_new_full(name, class, type, ttl)))
 527         return NULL;
 528
 529     switch (type) {
 530         case AVAHI_DNS_TYPE_PTR:
 531         case AVAHI_DNS_TYPE_CNAME:
 532         case AVAHI_DNS_TYPE_NS:
 533
 534 /*             avahi_log_debug("ptr"); */
 535
 536             if (avahi_dns_packet_consume_name(p, buf, sizeof(buf)) < 0)
 537                 goto fail;
 538
 539             r->data.ptr.name = avahi_strdup(buf);
 540             break;
 541
 542
 543         case AVAHI_DNS_TYPE_SRV:
 544
 545 /*             avahi_log_debug("srv"); */
 546
 547             if (avahi_dns_packet_consume_uint16(p, &r->data.srv.priority) < 0 ||
 548                 avahi_dns_packet_consume_uint16(p, &r->data.srv.weight) < 0 ||
 549                 avahi_dns_packet_consume_uint16(p, &r->data.srv.port) < 0 ||
 550                 avahi_dns_packet_consume_name(p, buf, sizeof(buf)) < 0)
 551                 goto fail;
 552
 553             r->data.srv.name = avahi_strdup(buf);
 554             break;
 555
 556         case AVAHI_DNS_TYPE_HINFO:
 557
 558 /*             avahi_log_debug("hinfo"); */
 559
 560             if (avahi_dns_packet_consume_string(p, buf, sizeof(buf)) < 0)
 561                 goto fail;
 562
 563             r->data.hinfo.cpu = avahi_strdup(buf);
 564
 565             if (avahi_dns_packet_consume_string(p, buf, sizeof(buf)) < 0)
 566                 goto fail;
 567
 568             r->data.hinfo.os = avahi_strdup(buf);
 569             break;
 570
 571         case AVAHI_DNS_TYPE_TXT:
 572
 573 /*             avahi_log_debug("txt"); */
 574
 575             if (rdlength > 0) {
 576                 r->data.txt.string_list = avahi_string_list_parse(avahi_dns_packet_get_rptr(p), rdlength);
 577
 578                 if (avahi_dns_packet_skip(p, rdlength) < 0)
 579                     goto fail;
 580             } else
 581                 r->data.txt.string_list = NULL;
 582
 583             break;
 584
 585         case AVAHI_DNS_TYPE_A:
 586
 587 /*             avahi_log_debug("A"); */
 588
 589             if (avahi_dns_packet_consume_bytes(p, &r->data.a.address, sizeof(AvahiIPv4Address)) < 0)
 590                 goto fail;
 591
 592             break;
 593
 594         case AVAHI_DNS_TYPE_AAAA:
 595
 596 /*             avahi_log_debug("aaaa"); */
 597
 598             if (avahi_dns_packet_consume_bytes(p, &r->data.aaaa.address, sizeof(AvahiIPv6Address)) < 0)
 599                 goto fail;
 600
 601             break;
 602
 603         default:
 604
 605 /*             avahi_log_debug("generic"); */
 606
 607             if (rdlength > 0) {
 608
 609                 r->data.generic.data = avahi_memdup(avahi_dns_packet_get_rptr(p), rdlength);
 610
 611                 if (avahi_dns_packet_skip(p, rdlength) < 0)
 612                     goto fail;
 613             }
 614
 615             break;
 616     }
 617
 618 /*     avahi_log_debug("%i == %u ?", (uint8_t*) avahi_dns_packet_get_rptr(p) - (uint8_t*) start, rdlength); */
 619
 620     /* Check if we read enough data */
 621     if ((const uint8_t*) avahi_dns_packet_get_rptr(p) - (const uint8_t*) start != rdlength)
 622         goto fail;
 623
 624     return r;
 625
 626 fail:
 627     if (r)
 628         avahi_record_unref(r);
 629
 630     return NULL;
 631 }
 632
 633 AvahiKey* avahi_dns_packet_consume_key(AvahiDnsPacket *p, int *ret_unicast_response) {
 634     char name[256];
 635     uint16_t type, class;
 636
 637     assert(p);
 638
 639     if (avahi_dns_packet_consume_name(p, name, sizeof(name)) < 0 ||
 640         avahi_dns_packet_consume_uint16(p, &type) < 0 ||
 641         avahi_dns_packet_consume_uint16(p, &class) < 0)
 642         return NULL;
 643
 644     if (ret_unicast_response)
 645         *ret_unicast_response = !!(class & AVAHI_DNS_UNICAST_RESPONSE);
 646
 647     class &= ~AVAHI_DNS_UNICAST_RESPONSE;
 648
 649     return avahi_key_new(name, class, type);
 650 }
 651
 652 uint8_t* avahi_dns_packet_append_key(AvahiDnsPacket *p, AvahiKey *k, int unicast_response) {
 653     uint8_t *t;
 654     size_t size;
 655
 656     assert(p);
 657     assert(k);
 658
 659     size = p->size;
 660
 661     if (!(t = avahi_dns_packet_append_name(p, k->name)) ||
 662         !avahi_dns_packet_append_uint16(p, k->type) ||
 663         !avahi_dns_packet_append_uint16(p, k->clazz | (unicast_response ? AVAHI_DNS_UNICAST_RESPONSE : 0))) {
 664         p->size = size;
 665         return NULL;
 666     }
 667
 668     return t;
 669 }
 670
 671 uint8_t* avahi_dns_packet_append_record(AvahiDnsPacket *p, AvahiRecord *r, int cache_flush, unsigned max_ttl) {
 672     uint8_t *t, *l, *start;
 673     size_t size;
 674
 675     assert(p);
 676     assert(r);
 677
 678     size = p->size;
 679
 680     if (!(t = avahi_dns_packet_append_name(p, r->key->name)) ||
 681         !avahi_dns_packet_append_uint16(p, r->key->type) ||
 682         !avahi_dns_packet_append_uint16(p, cache_flush ? (r->key->clazz | AVAHI_DNS_CACHE_FLUSH) : (r->key->clazz &~ AVAHI_DNS_CACHE_FLUSH)) ||
 683         !avahi_dns_packet_append_uint32(p, (max_ttl && r->ttl > max_ttl) ? max_ttl : r->ttl) ||
 684         !(l = avahi_dns_packet_append_uint16(p, 0)))
 685         goto fail;
 686
 687     start = avahi_dns_packet_extend(p, 0);
 688
 689     switch (r->key->type) {
 690
 691         case AVAHI_DNS_TYPE_PTR:
 692         case AVAHI_DNS_TYPE_CNAME:
 693         case AVAHI_DNS_TYPE_NS:
 694
 695             if (!(avahi_dns_packet_append_name(p, r->data.ptr.name)))
 696                 goto fail;
 697
 698             break;
 699
 700         case AVAHI_DNS_TYPE_SRV:
 701
 702             if (!avahi_dns_packet_append_uint16(p, r->data.srv.priority) ||
 703                 !avahi_dns_packet_append_uint16(p, r->data.srv.weight) ||
 704                 !avahi_dns_packet_append_uint16(p, r->data.srv.port) ||
 705                 !avahi_dns_packet_append_name(p, r->data.srv.name))
 706                 goto fail;
 707
 708             break;
 709
 710         case AVAHI_DNS_TYPE_HINFO:
 711             if (!avahi_dns_packet_append_string(p, r->data.hinfo.cpu) ||
 712                 !avahi_dns_packet_append_string(p, r->data.hinfo.os))
 713                 goto fail;
 714
 715             break;
 716
 717         case AVAHI_DNS_TYPE_TXT: {
 718
 719             uint8_t *data;
 720             size_t n;
 721
 722             n = avahi_string_list_serialize(r->data.txt.string_list, NULL, 0);
 723
 724 /*             avahi_log_debug("appending string: %u %p", n, r->data.txt.string_list); */
 725
 726             if (!(data = avahi_dns_packet_extend(p, n)))
 727                 goto fail;
 728
 729             avahi_string_list_serialize(r->data.txt.string_list, data, n);
 730             break;
 731         }
 732
 733
 734         case AVAHI_DNS_TYPE_A:
 735
 736             if (!avahi_dns_packet_append_bytes(p, &r->data.a.address, sizeof(r->data.a.address)))
 737                 goto fail;
 738
 739             break;
 740
 741         case AVAHI_DNS_TYPE_AAAA:
 742
 743             if (!avahi_dns_packet_append_bytes(p, &r->data.aaaa.address, sizeof(r->data.aaaa.address)))
 744                 goto fail;
 745
 746             break;
 747
 748         default:
 749
 750             if (r->data.generic.size &&
 751                 avahi_dns_packet_append_bytes(p, r->data.generic.data, r->data.generic.size))
 752                 goto fail;
 753
 754             break;
 755     }
 756
 757
 758
 759
 760     size = avahi_dns_packet_extend(p, 0) - start;
 761     assert(size <= 0xFFFF);
 762
 763 /*     avahi_log_debug("appended %u", size); */
 764
 765     l[0] = (uint8_t) ((uint16_t) size >> 8);
 766     l[1] = (uint8_t) ((uint16_t) size);
 767
 768     return t;
 769
 770
 771 fail:
 772     p->size = size;
 773     return NULL;
 774 }
 775
 776 int avahi_dns_packet_is_empty(AvahiDnsPacket *p) {
 777     assert(p);
 778
 779     return p->size <= AVAHI_DNS_PACKET_HEADER_SIZE;
 780 }
 781
 782 size_t avahi_dns_packet_space(AvahiDnsPacket *p) {
 783     assert(p);
 784
 785     assert(p->size <= p->max_size);
 786
 787     return p->max_size - p->size;
 788 }