1 /** 2 * @file 3 * DNS - host name to IP address resolver. 4 * 5 */ 6 7 /** 8 9 * This file implements a DNS host name to IP address resolver. 10 11 * Port to lwIP from uIP 12 * by Jim Pettinato April 2007 13 14 * uIP version Copyright (c) 2002-2003, Adam Dunkels. 15 * All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions 19 * are met: 20 * 1. Redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer. 22 * 2. Redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution. 25 * 3. The name of the author may not be used to endorse or promote 26 * products derived from this software without specific prior 27 * written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS 30 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 31 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 32 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 33 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 34 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE 35 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 36 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 37 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 38 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 39 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 40 * 41 * 42 * DNS.C 43 * 44 * The lwIP DNS resolver functions are used to lookup a host name and 45 * map it to a numerical IP address. It maintains a list of resolved 46 * hostnames that can be queried with the dns_lookup() function. 47 * New hostnames can be resolved using the dns_query() function. 48 * 49 * The lwIP version of the resolver also adds a non-blocking version of 50 * gethostbyname() that will work with a raw API application. This function 51 * checks for an IP address string first and converts it if it is valid. 52 * gethostbyname() then does a dns_lookup() to see if the name is 53 * already in the table. If so, the IP is returned. If not, a query is 54 * issued and the function returns with a ERR_INPROGRESS status. The app 55 * using the dns client must then go into a waiting state. 56 * 57 * Once a hostname has been resolved (or found to be non-existent), 58 * the resolver code calls a specified callback function (which 59 * must be implemented by the module that uses the resolver). 60 */ 61 62 /*----------------------------------------------------------------------------- 63 * RFC 1035 - Domain names - implementation and specification 64 * RFC 2181 - Clarifications to the DNS Specification 65 *----------------------------------------------------------------------------*/ 66 67 /** @todo: define good default values (rfc compliance) */ 68 /** @todo: improve answer parsing, more checkings... */ 69 /** @todo: check RFC1035 - 7.3. Processing responses */ 70 71 /*----------------------------------------------------------------------------- 72 * Includes 73 *----------------------------------------------------------------------------*/ 74 75 #include "lwip/opt.h" 76 77 #if LWIP_DNS /* don't build if not configured for use in lwipopts.h */ 78 79 #include "lwip/udp.h" 80 #include "lwip/mem.h" 81 #include "lwip/memp.h" 82 #include "lwip/dns.h" 83 84 #include <string.h> 85 86 /** DNS server IP address */ 87 #ifndef DNS_SERVER_ADDRESS 88 #define DNS_SERVER_ADDRESS(ipaddr) (ip4_addr_set_u32(ipaddr, ipaddr_addr("208.67.222.222"))) /* resolver1.opendns.com */ 89 #endif 90 91 /** DNS server port address */ 92 #ifndef DNS_SERVER_PORT 93 #define DNS_SERVER_PORT 53 94 #endif 95 96 /** DNS maximum number of retries when asking for a name, before "timeout". */ 97 #ifndef DNS_MAX_RETRIES 98 #define DNS_MAX_RETRIES 4 99 #endif 100 101 /** DNS resource record max. TTL (one week as default) */ 102 #ifndef DNS_MAX_TTL 103 #define DNS_MAX_TTL 604800 104 #endif 105 106 /* DNS protocol flags */ 107 #define DNS_FLAG1_RESPONSE 0x80 108 #define DNS_FLAG1_OPCODE_STATUS 0x10 109 #define DNS_FLAG1_OPCODE_INVERSE 0x08 110 #define DNS_FLAG1_OPCODE_STANDARD 0x00 111 #define DNS_FLAG1_AUTHORATIVE 0x04 112 #define DNS_FLAG1_TRUNC 0x02 113 #define DNS_FLAG1_RD 0x01 114 #define DNS_FLAG2_RA 0x80 115 #define DNS_FLAG2_ERR_MASK 0x0f 116 #define DNS_FLAG2_ERR_NONE 0x00 117 #define DNS_FLAG2_ERR_NAME 0x03 118 119 /* DNS protocol states */ 120 #define DNS_STATE_UNUSED 0 121 #define DNS_STATE_NEW 1 122 #define DNS_STATE_ASKING 2 123 #define DNS_STATE_DONE 3 124 125 #ifdef PACK_STRUCT_USE_INCLUDES 126 # include "arch/bpstruct.h" 127 #endif 128 PACK_STRUCT_BEGIN 129 /** DNS message header */ 130 struct dns_hdr { 131 PACK_STRUCT_FIELD(u16_t id); 132 PACK_STRUCT_FIELD(u8_t flags1); 133 PACK_STRUCT_FIELD(u8_t flags2); 134 PACK_STRUCT_FIELD(u16_t numquestions); 135 PACK_STRUCT_FIELD(u16_t numanswers); 136 PACK_STRUCT_FIELD(u16_t numauthrr); 137 PACK_STRUCT_FIELD(u16_t numextrarr); 138 } PACK_STRUCT_STRUCT; 139 PACK_STRUCT_END 140 #ifdef PACK_STRUCT_USE_INCLUDES 141 # include "arch/epstruct.h" 142 #endif 143 #define SIZEOF_DNS_HDR 12 144 145 /** DNS query message structure. 146 No packing needed: only used locally on the stack. */ 147 struct dns_query { 148 /* DNS query record starts with either a domain name or a pointer 149 to a name already present somewhere in the packet. */ 150 u16_t type; 151 u16_t cls; 152 }; 153 #define SIZEOF_DNS_QUERY 4 154 155 /** DNS answer message structure. 156 No packing needed: only used locally on the stack. */ 157 struct dns_answer { 158 /* DNS answer record starts with either a domain name or a pointer 159 to a name already present somewhere in the packet. */ 160 u16_t type; 161 u16_t cls; 162 u32_t ttl; 163 u16_t len; 164 }; 165 #define SIZEOF_DNS_ANSWER 10 166 167 /** DNS table entry */ 168 struct dns_table_entry { 169 u8_t state; 170 u8_t numdns; 171 u8_t tmr; 172 u8_t retries; 173 u8_t seqno; 174 u8_t err; 175 u32_t ttl; 176 char name[DNS_MAX_NAME_LENGTH]; 177 ip_addr_t ipaddr; 178 /* pointer to callback on DNS query done */ 179 dns_found_callback found; 180 void *arg; 181 }; 182 183 #if DNS_LOCAL_HOSTLIST 184 185 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC 186 /** Local host-list. For hostnames in this list, no 187 * external name resolution is performed */ 188 static struct local_hostlist_entry *local_hostlist_dynamic; 189 #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ 190 191 /** Defining this allows the local_hostlist_static to be placed in a different 192 * linker section (e.g. FLASH) */ 193 #ifndef DNS_LOCAL_HOSTLIST_STORAGE_PRE 194 #define DNS_LOCAL_HOSTLIST_STORAGE_PRE static 195 #endif /* DNS_LOCAL_HOSTLIST_STORAGE_PRE */ 196 /** Defining this allows the local_hostlist_static to be placed in a different 197 * linker section (e.g. FLASH) */ 198 #ifndef DNS_LOCAL_HOSTLIST_STORAGE_POST 199 #define DNS_LOCAL_HOSTLIST_STORAGE_POST 200 #endif /* DNS_LOCAL_HOSTLIST_STORAGE_POST */ 201 DNS_LOCAL_HOSTLIST_STORAGE_PRE struct local_hostlist_entry local_hostlist_static[] 202 DNS_LOCAL_HOSTLIST_STORAGE_POST = DNS_LOCAL_HOSTLIST_INIT; 203 204 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ 205 206 static void dns_init_local(); 207 #endif /* DNS_LOCAL_HOSTLIST */ 208 209 210 /* forward declarations */ 211 static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port); 212 static void dns_check_entries(void); 213 214 /*----------------------------------------------------------------------------- 215 * Globales 216 *----------------------------------------------------------------------------*/ 217 218 /* DNS variables */ 219 static struct udp_pcb *dns_pcb; 220 static u8_t dns_seqno; 221 static struct dns_table_entry dns_table[DNS_TABLE_SIZE]; 222 static ip_addr_t dns_servers[DNS_MAX_SERVERS]; 223 /** Contiguous buffer for processing responses */ 224 static u8_t dns_payload_buffer[LWIP_MEM_ALIGN_BUFFER(DNS_MSG_SIZE)]; 225 static u8_t* dns_payload; 226 227 /** 228 * Initialize the resolver: set up the UDP pcb and configure the default server 229 * (DNS_SERVER_ADDRESS). 230 */ 231 void 232 dns_init() 233 { 234 ip_addr_t dnsserver; 235 236 dns_payload = (u8_t *)LWIP_MEM_ALIGN(dns_payload_buffer); 237 238 /* initialize default DNS server address */ 239 DNS_SERVER_ADDRESS(&dnsserver); 240 241 LWIP_DEBUGF(DNS_DEBUG, ("dns_init: initializing\n")); 242 243 /* if dns client not yet initialized... */ 244 if (dns_pcb == NULL) { 245 dns_pcb = udp_new(); 246 247 if (dns_pcb != NULL) { 248 /* initialize DNS table not needed (initialized to zero since it is a 249 * global variable) */ 250 LWIP_ASSERT("For implicit initialization to work, DNS_STATE_UNUSED needs to be 0", 251 DNS_STATE_UNUSED == 0); 252 253 /* initialize DNS client */ 254 udp_bind(dns_pcb, IP_ADDR_ANY, 0); 255 udp_recv(dns_pcb, dns_recv, NULL); 256 257 /* initialize default DNS primary server */ 258 dns_setserver(0, &dnsserver); 259 } 260 } 261 #if DNS_LOCAL_HOSTLIST 262 dns_init_local(); 263 #endif 264 } 265 266 /** 267 * Initialize one of the DNS servers. 268 * 269 * @param numdns the index of the DNS server to set must be < DNS_MAX_SERVERS 270 * @param dnsserver IP address of the DNS server to set 271 */ 272 void 273 dns_setserver(u8_t numdns, ip_addr_t *dnsserver) 274 { 275 /* 276 * hpa: the lwip code has the dnsserver->addr != 0 test, but that would 277 * seem to indicate that there is no way to cancel a previously given 278 * DNS server... 279 */ 280 if ((numdns < DNS_MAX_SERVERS) && (dns_pcb != NULL) && 281 (dnsserver != NULL) /* && !ip_addr_isany(dnsserver) */) { 282 dns_servers[numdns] = (*dnsserver); 283 } 284 } 285 286 /** 287 * Obtain one of the currently configured DNS server. 288 * 289 * @param numdns the index of the DNS server 290 * @return IP address of the indexed DNS server or "ip_addr_any" if the DNS 291 * server has not been configured. 292 */ 293 ip_addr_t 294 dns_getserver(u8_t numdns) 295 { 296 if (numdns < DNS_MAX_SERVERS) { 297 return dns_servers[numdns]; 298 } else { 299 return *IP_ADDR_ANY; 300 } 301 } 302 303 /** 304 * The DNS resolver client timer - handle retries and timeouts and should 305 * be called every DNS_TMR_INTERVAL milliseconds (every second by default). 306 */ 307 void 308 dns_tmr(void) 309 { 310 if (dns_pcb != NULL) { 311 LWIP_DEBUGF(DNS_DEBUG, ("dns_tmr: dns_check_entries\n")); 312 dns_check_entries(); 313 } 314 } 315 316 #if DNS_LOCAL_HOSTLIST 317 static void 318 dns_init_local() 319 { 320 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT) 321 int i; 322 struct local_hostlist_entry *entry; 323 /* Dynamic: copy entries from DNS_LOCAL_HOSTLIST_INIT to list */ 324 struct local_hostlist_entry local_hostlist_init[] = DNS_LOCAL_HOSTLIST_INIT; 325 size_t namelen; 326 for (i = 0; i < sizeof(local_hostlist_init) / sizeof(struct local_hostlist_entry); i++) { 327 struct local_hostlist_entry *init_entry = &local_hostlist_init[i]; 328 LWIP_ASSERT("invalid host name (NULL)", init_entry->name != NULL); 329 namelen = strlen(init_entry->name); 330 LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN); 331 entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST); 332 LWIP_ASSERT("mem-error in dns_init_local", entry != NULL); 333 if (entry != NULL) { 334 entry->name = (char*)entry + sizeof(struct local_hostlist_entry); 335 MEMCPY((char*)entry->name, init_entry->name, namelen); 336 ((char*)entry->name)[namelen] = 0; 337 entry->addr = init_entry->addr; 338 entry->next = local_hostlist_dynamic; 339 local_hostlist_dynamic = entry; 340 } 341 } 342 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT) */ 343 } 344 345 /** 346 * Scans the local host-list for a hostname. 347 * 348 * @param hostname Hostname to look for in the local host-list 349 * @return The first IP address for the hostname in the local host-list or 350 * IPADDR_NONE if not found. 351 */ 352 static u32_t 353 dns_lookup_local(const char *hostname) 354 { 355 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC 356 struct local_hostlist_entry *entry = local_hostlist_dynamic; 357 while(entry != NULL) { 358 if(strcmp(entry->name, hostname) == 0) { 359 return ip4_addr_get_u32(&entry->addr); 360 } 361 entry = entry->next; 362 } 363 #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ 364 int i; 365 for (i = 0; i < sizeof(local_hostlist_static) / sizeof(struct local_hostlist_entry); i++) { 366 if(strcmp(local_hostlist_static[i].name, hostname) == 0) { 367 return ip4_addr_get_u32(&local_hostlist_static[i].addr); 368 } 369 } 370 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ 371 return IPADDR_NONE; 372 } 373 374 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC 375 /** Remove all entries from the local host-list for a specific hostname 376 * and/or IP addess 377 * 378 * @param hostname hostname for which entries shall be removed from the local 379 * host-list 380 * @param addr address for which entries shall be removed from the local host-list 381 * @return the number of removed entries 382 */ 383 int 384 dns_local_removehost(const char *hostname, const ip_addr_t *addr) 385 { 386 int removed = 0; 387 struct local_hostlist_entry *entry = local_hostlist_dynamic; 388 struct local_hostlist_entry *last_entry = NULL; 389 while (entry != NULL) { 390 if (((hostname == NULL) || !strcmp(entry->name, hostname)) && 391 ((addr == NULL) || ip_addr_cmp(&entry->addr, addr))) { 392 struct local_hostlist_entry *free_entry; 393 if (last_entry != NULL) { 394 last_entry->next = entry->next; 395 } else { 396 local_hostlist_dynamic = entry->next; 397 } 398 free_entry = entry; 399 entry = entry->next; 400 memp_free(MEMP_LOCALHOSTLIST, free_entry); 401 removed++; 402 } else { 403 last_entry = entry; 404 entry = entry->next; 405 } 406 } 407 return removed; 408 } 409 410 /** 411 * Add a hostname/IP address pair to the local host-list. 412 * Duplicates are not checked. 413 * 414 * @param hostname hostname of the new entry 415 * @param addr IP address of the new entry 416 * @return ERR_OK if succeeded or ERR_MEM on memory error 417 */ 418 err_t 419 dns_local_addhost(const char *hostname, const ip_addr_t *addr) 420 { 421 struct local_hostlist_entry *entry; 422 size_t namelen; 423 LWIP_ASSERT("invalid host name (NULL)", hostname != NULL); 424 namelen = strlen(hostname); 425 LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN); 426 entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST); 427 if (entry == NULL) { 428 return ERR_MEM; 429 } 430 entry->name = (char*)entry + sizeof(struct local_hostlist_entry); 431 MEMCPY((char*)entry->name, hostname, namelen); 432 ((char*)entry->name)[namelen] = 0; 433 ip_addr_copy(entry->addr, *addr); 434 entry->next = local_hostlist_dynamic; 435 local_hostlist_dynamic = entry; 436 return ERR_OK; 437 } 438 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC*/ 439 #endif /* DNS_LOCAL_HOSTLIST */ 440 441 /** 442 * Look up a hostname in the array of known hostnames. 443 * 444 * @note This function only looks in the internal array of known 445 * hostnames, it does not send out a query for the hostname if none 446 * was found. The function dns_enqueue() can be used to send a query 447 * for a hostname. 448 * 449 * @param name the hostname to look up 450 * @return the hostname's IP address, as u32_t (instead of ip_addr_t to 451 * better check for failure: != IPADDR_NONE) or IPADDR_NONE if the hostname 452 * was not found in the cached dns_table. 453 */ 454 static u32_t 455 dns_lookup(const char *name) 456 { 457 u8_t i; 458 #if DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN) 459 u32_t addr; 460 #endif /* DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN) */ 461 #if DNS_LOCAL_HOSTLIST 462 if ((addr = dns_lookup_local(name)) != IPADDR_NONE) { 463 return addr; 464 } 465 #endif /* DNS_LOCAL_HOSTLIST */ 466 #ifdef DNS_LOOKUP_LOCAL_EXTERN 467 if((addr = DNS_LOOKUP_LOCAL_EXTERN(name)) != IPADDR_NONE) { 468 return addr; 469 } 470 #endif /* DNS_LOOKUP_LOCAL_EXTERN */ 471 472 /* Walk through name list, return entry if found. If not, return NULL. */ 473 for (i = 0; i < DNS_TABLE_SIZE; ++i) { 474 if ((dns_table[i].state == DNS_STATE_DONE) && 475 (strcmp(name, dns_table[i].name) == 0)) { 476 LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name)); 477 ip_addr_debug_print(DNS_DEBUG, &(dns_table[i].ipaddr)); 478 LWIP_DEBUGF(DNS_DEBUG, ("\n")); 479 return ip4_addr_get_u32(&dns_table[i].ipaddr); 480 } 481 } 482 483 return IPADDR_NONE; 484 } 485 486 #if DNS_DOES_NAME_CHECK 487 /** 488 * Compare the "dotted" name "query" with the encoded name "response" 489 * to make sure an answer from the DNS server matches the current dns_table 490 * entry (otherwise, answers might arrive late for hostname not on the list 491 * any more). 492 * 493 * @param query hostname (not encoded) from the dns_table 494 * @param response encoded hostname in the DNS response 495 * @return 0: names equal; 1: names differ 496 */ 497 static u8_t 498 dns_compare_name(unsigned char *query, unsigned char *response) 499 { 500 unsigned char n; 501 502 do { 503 n = *response++; 504 /** @see RFC 1035 - 4.1.4. Message compression */ 505 if ((n & 0xc0) == 0xc0) { 506 /* Compressed name */ 507 break; 508 } else { 509 /* Not compressed name */ 510 while (n > 0) { 511 if ((*query) != (*response)) { 512 return 1; 513 } 514 ++response; 515 ++query; 516 --n; 517 }; 518 ++query; 519 } 520 } while (*response != 0); 521 522 return 0; 523 } 524 #endif /* DNS_DOES_NAME_CHECK */ 525 526 /** 527 * Walk through a compact encoded DNS name and return the end of the name. 528 * 529 * @param query encoded DNS name in the DNS server response 530 * @return end of the name 531 */ 532 static unsigned char * 533 dns_parse_name(unsigned char *query) 534 { 535 unsigned char n; 536 537 do { 538 n = *query++; 539 /** @see RFC 1035 - 4.1.4. Message compression */ 540 if ((n & 0xc0) == 0xc0) { 541 /* Compressed name */ 542 break; 543 } else { 544 /* Not compressed name */ 545 while (n > 0) { 546 ++query; 547 --n; 548 }; 549 } 550 } while (*query != 0); 551 552 return query + 1; 553 } 554 555 /** 556 * Send a DNS query packet. 557 * 558 * @param numdns index of the DNS server in the dns_servers table 559 * @param name hostname to query 560 * @param id index of the hostname in dns_table, used as transaction ID in the 561 * DNS query packet 562 * @return ERR_OK if packet is sent; an err_t indicating the problem otherwise 563 */ 564 static err_t 565 dns_send(u8_t numdns, const char* name, u8_t id) 566 { 567 err_t err; 568 struct dns_hdr *hdr; 569 struct dns_query qry; 570 struct pbuf *p; 571 char *query, *nptr; 572 const char *pHostname; 573 u8_t n; 574 575 LWIP_DEBUGF(DNS_DEBUG, ("dns_send: dns_servers[%"U16_F"] \"%s\": request\n", 576 (u16_t)(numdns), name)); 577 LWIP_ASSERT("dns server out of array", numdns < DNS_MAX_SERVERS); 578 LWIP_ASSERT("dns server has no IP address set", !ip_addr_isany(&dns_servers[numdns])); 579 580 /* if here, we have either a new query or a retry on a previous query to process */ 581 p = pbuf_alloc(PBUF_TRANSPORT, SIZEOF_DNS_HDR + DNS_MAX_NAME_LENGTH + 582 SIZEOF_DNS_QUERY, PBUF_RAM); 583 if (p != NULL) { 584 LWIP_ASSERT("pbuf must be in one piece", p->next == NULL); 585 /* fill dns header */ 586 hdr = (struct dns_hdr*)p->payload; 587 memset(hdr, 0, SIZEOF_DNS_HDR); 588 hdr->id = htons(id); 589 hdr->flags1 = DNS_FLAG1_RD; 590 hdr->numquestions = PP_HTONS(1); 591 query = (char*)hdr + SIZEOF_DNS_HDR; 592 pHostname = name; 593 --pHostname; 594 595 /* convert hostname into suitable query format. */ 596 do { 597 ++pHostname; 598 nptr = query; 599 ++query; 600 for(n = 0; *pHostname != '.' && *pHostname != 0; ++pHostname) { 601 *query = *pHostname; 602 ++query; 603 ++n; 604 } 605 *nptr = n; 606 } while(*pHostname != 0); 607 *query++='\0'; 608 609 /* fill dns query */ 610 qry.type = PP_HTONS(DNS_RRTYPE_A); 611 qry.cls = PP_HTONS(DNS_RRCLASS_IN); 612 SMEMCPY(query, &qry, SIZEOF_DNS_QUERY); 613 614 /* resize pbuf to the exact dns query */ 615 pbuf_realloc(p, (u16_t)((query + SIZEOF_DNS_QUERY) - ((char*)(p->payload)))); 616 617 /* connect to the server for faster receiving */ 618 udp_connect(dns_pcb, &dns_servers[numdns], DNS_SERVER_PORT); 619 /* send dns packet */ 620 err = udp_sendto(dns_pcb, p, &dns_servers[numdns], DNS_SERVER_PORT); 621 622 /* free pbuf */ 623 pbuf_free(p); 624 } else { 625 err = ERR_MEM; 626 } 627 628 return err; 629 } 630 631 /** 632 * dns_check_entry() - see if pEntry has not yet been queried and, if so, sends out a query. 633 * Check an entry in the dns_table: 634 * - send out query for new entries 635 * - retry old pending entries on timeout (also with different servers) 636 * - remove completed entries from the table if their TTL has expired 637 * 638 * @param i index of the dns_table entry to check 639 */ 640 static void 641 dns_check_entry(u8_t i) 642 { 643 err_t err; 644 struct dns_table_entry *pEntry = &dns_table[i]; 645 646 LWIP_ASSERT("array index out of bounds", i < DNS_TABLE_SIZE); 647 648 switch(pEntry->state) { 649 650 case DNS_STATE_NEW: { 651 /* initialize new entry */ 652 pEntry->state = DNS_STATE_ASKING; 653 pEntry->numdns = 0; 654 pEntry->tmr = 1; 655 pEntry->retries = 0; 656 657 /* send DNS packet for this entry */ 658 err = dns_send(pEntry->numdns, pEntry->name, i); 659 if (err != ERR_OK) { 660 LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING, 661 ("dns_send returned error: %s\n", lwip_strerr(err))); 662 } 663 break; 664 } 665 666 case DNS_STATE_ASKING: { 667 if (--pEntry->tmr == 0) { 668 if (++pEntry->retries == DNS_MAX_RETRIES) { 669 if ((pEntry->numdns+1<DNS_MAX_SERVERS) && !ip_addr_isany(&dns_servers[pEntry->numdns+1])) { 670 /* change of server */ 671 pEntry->numdns++; 672 pEntry->tmr = 1; 673 pEntry->retries = 0; 674 break; 675 } else { 676 LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": timeout\n", pEntry->name)); 677 /* call specified callback function if provided */ 678 if (pEntry->found) 679 (*pEntry->found)(pEntry->name, NULL, pEntry->arg); 680 /* flush this entry */ 681 pEntry->state = DNS_STATE_UNUSED; 682 pEntry->found = NULL; 683 break; 684 } 685 } 686 687 /* wait longer for the next retry */ 688 pEntry->tmr = pEntry->retries; 689 690 /* send DNS packet for this entry */ 691 err = dns_send(pEntry->numdns, pEntry->name, i); 692 if (err != ERR_OK) { 693 LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING, 694 ("dns_send returned error: %s\n", lwip_strerr(err))); 695 } 696 } 697 break; 698 } 699 700 case DNS_STATE_DONE: { 701 /* if the time to live is nul */ 702 if (--pEntry->ttl == 0) { 703 LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": flush\n", pEntry->name)); 704 /* flush this entry */ 705 pEntry->state = DNS_STATE_UNUSED; 706 pEntry->found = NULL; 707 } 708 break; 709 } 710 case DNS_STATE_UNUSED: 711 /* nothing to do */ 712 break; 713 default: 714 LWIP_ASSERT("unknown dns_table entry state:", 0); 715 break; 716 } 717 } 718 719 /** 720 * Call dns_check_entry for each entry in dns_table - check all entries. 721 */ 722 static void 723 dns_check_entries(void) 724 { 725 u8_t i; 726 727 for (i = 0; i < DNS_TABLE_SIZE; ++i) { 728 dns_check_entry(i); 729 } 730 } 731 732 /** 733 * Receive input function for DNS response packets arriving for the dns UDP pcb. 734 * 735 * @params see udp.h 736 */ 737 static void 738 dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port) 739 { 740 u16_t i; 741 char *pHostname; 742 struct dns_hdr *hdr; 743 struct dns_answer ans; 744 struct dns_table_entry *pEntry; 745 u16_t nquestions, nanswers; 746 747 LWIP_UNUSED_ARG(arg); 748 LWIP_UNUSED_ARG(pcb); 749 LWIP_UNUSED_ARG(addr); 750 LWIP_UNUSED_ARG(port); 751 752 /* is the dns message too big ? */ 753 if (p->tot_len > DNS_MSG_SIZE) { 754 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too big\n")); 755 /* free pbuf and return */ 756 goto memerr; 757 } 758 759 /* is the dns message big enough ? */ 760 if (p->tot_len < (SIZEOF_DNS_HDR + SIZEOF_DNS_QUERY + SIZEOF_DNS_ANSWER)) { 761 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too small\n")); 762 /* free pbuf and return */ 763 goto memerr; 764 } 765 766 /* copy dns payload inside static buffer for processing */ 767 if (pbuf_copy_partial(p, dns_payload, p->tot_len, 0) == p->tot_len) { 768 /* The ID in the DNS header should be our entry into the name table. */ 769 hdr = (struct dns_hdr*)dns_payload; 770 i = htons(hdr->id); 771 if (i < DNS_TABLE_SIZE) { 772 pEntry = &dns_table[i]; 773 if(pEntry->state == DNS_STATE_ASKING) { 774 /* This entry is now completed. */ 775 pEntry->state = DNS_STATE_DONE; 776 pEntry->err = hdr->flags2 & DNS_FLAG2_ERR_MASK; 777 778 /* We only care about the question(s) and the answers. The authrr 779 and the extrarr are simply discarded. */ 780 nquestions = htons(hdr->numquestions); 781 nanswers = htons(hdr->numanswers); 782 783 /* Check for error. If so, call callback to inform. */ 784 if (((hdr->flags1 & DNS_FLAG1_RESPONSE) == 0) || (pEntry->err != 0) || (nquestions != 1)) { 785 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", pEntry->name)); 786 /* call callback to indicate error, clean up memory and return */ 787 goto responseerr; 788 } 789 790 #if DNS_DOES_NAME_CHECK 791 /* Check if the name in the "question" part match with the name in the entry. */ 792 if (dns_compare_name((unsigned char *)(pEntry->name), (unsigned char *)dns_payload + SIZEOF_DNS_HDR) != 0) { 793 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", pEntry->name)); 794 /* call callback to indicate error, clean up memory and return */ 795 goto responseerr; 796 } 797 #endif /* DNS_DOES_NAME_CHECK */ 798 799 /* Skip the name in the "question" part */ 800 pHostname = (char *) dns_parse_name((unsigned char *)dns_payload + SIZEOF_DNS_HDR) + SIZEOF_DNS_QUERY; 801 802 while (nanswers > 0) { 803 /* skip answer resource record's host name */ 804 pHostname = (char *) dns_parse_name((unsigned char *)pHostname); 805 806 /* Check for IP address type and Internet class. Others are discarded. */ 807 SMEMCPY(&ans, pHostname, SIZEOF_DNS_ANSWER); 808 if((ans.type == PP_HTONS(DNS_RRTYPE_A)) && (ans.cls == PP_HTONS(DNS_RRCLASS_IN)) && 809 (ans.len == PP_HTONS(sizeof(ip_addr_t))) ) { 810 /* read the answer resource record's TTL, and maximize it if needed */ 811 pEntry->ttl = ntohl(ans.ttl); 812 if (pEntry->ttl > DNS_MAX_TTL) { 813 pEntry->ttl = DNS_MAX_TTL; 814 } 815 /* read the IP address after answer resource record's header */ 816 SMEMCPY(&(pEntry->ipaddr), (pHostname+SIZEOF_DNS_ANSWER), sizeof(ip_addr_t)); 817 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", pEntry->name)); 818 ip_addr_debug_print(DNS_DEBUG, (&(pEntry->ipaddr))); 819 LWIP_DEBUGF(DNS_DEBUG, ("\n")); 820 /* call specified callback function if provided */ 821 if (pEntry->found) { 822 (*pEntry->found)(pEntry->name, &pEntry->ipaddr, pEntry->arg); 823 } 824 /* deallocate memory and return */ 825 goto memerr; 826 } else { 827 pHostname = pHostname + SIZEOF_DNS_ANSWER + htons(ans.len); 828 } 829 --nanswers; 830 } 831 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in response\n", pEntry->name)); 832 /* call callback to indicate error, clean up memory and return */ 833 goto responseerr; 834 } 835 } 836 } 837 838 /* deallocate memory and return */ 839 goto memerr; 840 841 responseerr: 842 /* ERROR: call specified callback function with NULL as name to indicate an error */ 843 if (pEntry->found) { 844 (*pEntry->found)(pEntry->name, NULL, pEntry->arg); 845 } 846 /* flush this entry */ 847 pEntry->state = DNS_STATE_UNUSED; 848 pEntry->found = NULL; 849 850 memerr: 851 /* free pbuf */ 852 pbuf_free(p); 853 return; 854 } 855 856 /** 857 * Queues a new hostname to resolve and sends out a DNS query for that hostname 858 * 859 * @param name the hostname that is to be queried 860 * @param found a callback founction to be called on success, failure or timeout 861 * @param callback_arg argument to pass to the callback function 862 * @return @return a err_t return code. 863 */ 864 static err_t 865 dns_enqueue(const char *name, dns_found_callback found, void *callback_arg) 866 { 867 u8_t i; 868 u8_t lseq, lseqi; 869 struct dns_table_entry *pEntry = NULL; 870 size_t namelen; 871 872 /* search an unused entry, or the oldest one */ 873 lseq = lseqi = 0; 874 for (i = 0; i < DNS_TABLE_SIZE; ++i) { 875 pEntry = &dns_table[i]; 876 /* is it an unused entry ? */ 877 if (pEntry->state == DNS_STATE_UNUSED) 878 break; 879 880 /* check if this is the oldest completed entry */ 881 if (pEntry->state == DNS_STATE_DONE) { 882 if ((dns_seqno - pEntry->seqno) > lseq) { 883 lseq = dns_seqno - pEntry->seqno; 884 lseqi = i; 885 } 886 } 887 } 888 889 /* if we don't have found an unused entry, use the oldest completed one */ 890 if (i == DNS_TABLE_SIZE) { 891 if ((lseqi >= DNS_TABLE_SIZE) || (dns_table[lseqi].state != DNS_STATE_DONE)) { 892 /* no entry can't be used now, table is full */ 893 LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS entries table is full\n", name)); 894 return ERR_MEM; 895 } else { 896 /* use the oldest completed one */ 897 i = lseqi; 898 pEntry = &dns_table[i]; 899 } 900 } 901 902 /* use this entry */ 903 LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS entry %"U16_F"\n", name, (u16_t)(i))); 904 905 /* fill the entry */ 906 pEntry->state = DNS_STATE_NEW; 907 pEntry->seqno = dns_seqno++; 908 pEntry->found = found; 909 pEntry->arg = callback_arg; 910 namelen = LWIP_MIN(strlen(name), DNS_MAX_NAME_LENGTH-1); 911 MEMCPY(pEntry->name, name, namelen); 912 pEntry->name[namelen] = 0; 913 914 /* force to send query without waiting timer */ 915 dns_check_entry(i); 916 917 /* dns query is enqueued */ 918 return ERR_INPROGRESS; 919 } 920 921 /** 922 * Resolve a hostname (string) into an IP address. 923 * NON-BLOCKING callback version for use with raw API!!! 924 * 925 * Returns immediately with one of err_t return codes: 926 * - ERR_OK if hostname is a valid IP address string or the host 927 * name is already in the local names table. 928 * - ERR_INPROGRESS enqueue a request to be sent to the DNS server 929 * for resolution if no errors are present. 930 * - ERR_ARG: dns client not initialized or invalid hostname 931 * 932 * @param hostname the hostname that is to be queried 933 * @param addr pointer to a ip_addr_t where to store the address if it is already 934 * cached in the dns_table (only valid if ERR_OK is returned!) 935 * @param found a callback function to be called on success, failure or timeout (only if 936 * ERR_INPROGRESS is returned!) 937 * @param callback_arg argument to pass to the callback function 938 * @return a err_t return code. 939 */ 940 err_t 941 dns_gethostbyname(const char *hostname, ip_addr_t *addr, dns_found_callback found, 942 void *callback_arg) 943 { 944 u32_t ipaddr; 945 /* not initialized or no valid server yet, or invalid addr pointer 946 * or invalid hostname or invalid hostname length */ 947 if ((dns_pcb == NULL) || (addr == NULL) || 948 (!hostname) || (!hostname[0]) || 949 (strlen(hostname) >= DNS_MAX_NAME_LENGTH)) { 950 return ERR_ARG; 951 } 952 953 #if LWIP_HAVE_LOOPIF 954 if (strcmp(hostname, "localhost")==0) { 955 ip_addr_set_loopback(addr); 956 return ERR_OK; 957 } 958 #endif /* LWIP_HAVE_LOOPIF */ 959 960 /* host name already in octet notation? set ip addr and return ERR_OK */ 961 ipaddr = ipaddr_addr(hostname); 962 if (ipaddr == IPADDR_NONE) { 963 /* already have this address cached? */ 964 ipaddr = dns_lookup(hostname); 965 } 966 if (ipaddr != IPADDR_NONE) { 967 ip4_addr_set_u32(addr, ipaddr); 968 return ERR_OK; 969 } 970 971 /* queue query with specified callback */ 972 return dns_enqueue(hostname, found, callback_arg); 973 } 974 975 #endif /* LWIP_DNS */ 976