1 /**
2 * @file
3 * DNS - host name to IP address resolver.
4 *
5 * @defgroup dns DNS
6 * @ingroup callbackstyle_api
7 *
8 * Implements a DNS host name to IP address resolver.
9 *
10 * The lwIP DNS resolver functions are used to lookup a host name and
11 * map it to a numerical IP address. It maintains a list of resolved
12 * hostnames that can be queried with the dns_lookup() function.
13 * New hostnames can be resolved using the dns_query() function.
14 *
15 * The lwIP version of the resolver also adds a non-blocking version of
16 * gethostbyname() that will work with a raw API application. This function
17 * checks for an IP address string first and converts it if it is valid.
18 * gethostbyname() then does a dns_lookup() to see if the name is
19 * already in the table. If so, the IP is returned. If not, a query is
20 * issued and the function returns with a ERR_INPROGRESS status. The app
21 * using the dns client must then go into a waiting state.
22 *
23 * Once a hostname has been resolved (or found to be non-existent),
24 * the resolver code calls a specified callback function (which
25 * must be implemented by the module that uses the resolver).
26 *
27 * Multicast DNS queries are supported for names ending on ".local".
28 * However, only "One-Shot Multicast DNS Queries" are supported (RFC 6762
29 * chapter 5.1), this is not a fully compliant implementation of continuous
30 * mDNS querying!
31 *
32 * All functions must be called from TCPIP thread.
33 *
34 * @see DNS_MAX_SERVERS
35 * @see LWIP_DHCP_MAX_DNS_SERVERS
36 * @see @ref netconn_common for thread-safe access.
37 */
38
39 /*
40 * Port to lwIP from uIP
41 * by Jim Pettinato April 2007
42 *
43 * security fixes and more by Simon Goldschmidt
44 *
45 * uIP version Copyright (c) 2002-2003, Adam Dunkels.
46 * All rights reserved.
47 *
48 * Redistribution and use in source and binary forms, with or without
49 * modification, are permitted provided that the following conditions
50 * are met:
51 * 1. Redistributions of source code must retain the above copyright
52 * notice, this list of conditions and the following disclaimer.
53 * 2. Redistributions in binary form must reproduce the above copyright
54 * notice, this list of conditions and the following disclaimer in the
55 * documentation and/or other materials provided with the distribution.
56 * 3. The name of the author may not be used to endorse or promote
57 * products derived from this software without specific prior
58 * written permission.
59 *
60 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
61 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
62 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
63 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
64 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
65 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
66 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
67 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
68 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
69 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
70 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
71 */
72
73 /*-----------------------------------------------------------------------------
74 * RFC 1035 - Domain names - implementation and specification
75 * RFC 2181 - Clarifications to the DNS Specification
76 *----------------------------------------------------------------------------*/
77
78 /** @todo: define good default values (rfc compliance) */
79 /** @todo: improve answer parsing, more checkings... */
80 /** @todo: check RFC1035 - 7.3. Processing responses */
81 /** @todo: one-shot mDNS: dual-stack fallback to another IP version */
82
83 /*-----------------------------------------------------------------------------
84 * Includes
85 *----------------------------------------------------------------------------*/
86
87 #include "lwip/opt.h"
88
89 #if LWIP_ENABLE_DISTRIBUTED_NET && !LWIP_USE_GET_HOST_BY_NAME_EXTERNAL
90 #include "lwip/distributed_net/distributed_net.h"
91 #include "lwip/distributed_net/udp_transmit.h"
92 #endif
93
94 #if LWIP_DNS /* don't build if not configured for use in lwipopts.h */
95
96 #include "lwip/def.h"
97 #include "lwip/udp.h"
98 #include "lwip/mem.h"
99 #include "lwip/memp.h"
100 #include "lwip/dns.h"
101 #include "lwip/prot/dns.h"
102
103 #include <string.h>
104
105 /** Random generator function to create random TXIDs and source ports for queries */
106 #ifndef DNS_RAND_TXID
107 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_XID) != 0)
108 #define DNS_RAND_TXID LWIP_RAND
109 #else
110 static u16_t dns_txid;
111 #define DNS_RAND_TXID() (++dns_txid)
112 #endif
113 #endif
114
115 /** Limits the source port to be >= 1024 by default */
116 #ifndef DNS_PORT_ALLOWED
117 #define DNS_PORT_ALLOWED(port) ((port) >= 1024)
118 #endif
119
120 /** DNS resource record max. TTL (one week as default) */
121 #ifndef DNS_MAX_TTL
122 #define DNS_MAX_TTL 604800
123 #elif DNS_MAX_TTL > 0x7FFFFFFF
124 #error DNS_MAX_TTL must be a positive 32-bit value
125 #endif
126
127 #if DNS_TABLE_SIZE > 255
128 #error DNS_TABLE_SIZE must fit into an u8_t
129 #endif
130 #if DNS_MAX_SERVERS > 255
131 #error DNS_MAX_SERVERS must fit into an u8_t
132 #endif
133
134 /* The number of parallel requests (i.e. calls to dns_gethostbyname
135 * that cannot be answered from the DNS table.
136 * This is set to the table size by default.
137 */
138 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
139 #ifndef DNS_MAX_REQUESTS
140 #define DNS_MAX_REQUESTS DNS_TABLE_SIZE
141 #else
142 #if DNS_MAX_REQUESTS > 255
143 #error DNS_MAX_REQUESTS must fit into an u8_t
144 #endif
145 #endif
146 #else
147 /* In this configuration, both arrays have to have the same size and are used
148 * like one entry (used/free) */
149 #define DNS_MAX_REQUESTS DNS_TABLE_SIZE
150 #endif
151
152 /* The number of UDP source ports used in parallel */
153 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
154 #ifndef DNS_MAX_SOURCE_PORTS
155 #define DNS_MAX_SOURCE_PORTS DNS_MAX_REQUESTS
156 #else
157 #if DNS_MAX_SOURCE_PORTS > 255
158 #error DNS_MAX_SOURCE_PORTS must fit into an u8_t
159 #endif
160 #endif
161 #else
162 #ifdef DNS_MAX_SOURCE_PORTS
163 #undef DNS_MAX_SOURCE_PORTS
164 #endif
165 #define DNS_MAX_SOURCE_PORTS 1
166 #endif
167
168 #if LWIP_IPV4 && LWIP_IPV6
169 #define LWIP_DNS_ADDRTYPE_IS_IPV6(t) (((t) == LWIP_DNS_ADDRTYPE_IPV6_IPV4) || ((t) == LWIP_DNS_ADDRTYPE_IPV6))
170 #define LWIP_DNS_ADDRTYPE_MATCH_IP(t, ip) (IP_IS_V6_VAL(ip) ? LWIP_DNS_ADDRTYPE_IS_IPV6(t) : (!LWIP_DNS_ADDRTYPE_IS_IPV6(t)))
171 #define LWIP_DNS_ADDRTYPE_ARG(x) , x
172 #define LWIP_DNS_ADDRTYPE_ARG_OR_ZERO(x) x
173 #define LWIP_DNS_SET_ADDRTYPE(x, y) do { x = y; } while(0)
174 #else
175 #if LWIP_IPV6
176 #define LWIP_DNS_ADDRTYPE_IS_IPV6(t) 1
177 #else
178 #define LWIP_DNS_ADDRTYPE_IS_IPV6(t) 0
179 #endif
180 #define LWIP_DNS_ADDRTYPE_MATCH_IP(t, ip) 1
181 #define LWIP_DNS_ADDRTYPE_ARG(x)
182 #define LWIP_DNS_ADDRTYPE_ARG_OR_ZERO(x) 0
183 #define LWIP_DNS_SET_ADDRTYPE(x, y)
184 #endif /* LWIP_IPV4 && LWIP_IPV6 */
185
186 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
187 #define LWIP_DNS_ISMDNS_ARG(x) , x
188 #else
189 #define LWIP_DNS_ISMDNS_ARG(x)
190 #endif
191
192 /** DNS query message structure.
193 No packing needed: only used locally on the stack. */
194 struct dns_query {
195 /* DNS query record starts with either a domain name or a pointer
196 to a name already present somewhere in the packet. */
197 u16_t type;
198 u16_t cls;
199 };
200 #define SIZEOF_DNS_QUERY 4
201
202 /** DNS answer message structure.
203 No packing needed: only used locally on the stack. */
204 struct dns_answer {
205 /* DNS answer record starts with either a domain name or a pointer
206 to a name already present somewhere in the packet. */
207 u16_t type;
208 u16_t cls;
209 u32_t ttl;
210 u16_t len;
211 };
212 #define SIZEOF_DNS_ANSWER 10
213 /* maximum allowed size for the struct due to non-packed */
214 #define SIZEOF_DNS_ANSWER_ASSERT 12
215
216 /* DNS table entry states */
217 typedef enum {
218 DNS_STATE_UNUSED = 0,
219 DNS_STATE_NEW = 1,
220 DNS_STATE_ASKING = 2,
221 DNS_STATE_DONE = 3
222 } dns_state_enum_t;
223
224 /** DNS table entry */
225 struct dns_table_entry {
226 u32_t ttl;
227 ip_addr_t ipaddr;
228 u16_t txid;
229 u8_t state;
230 u8_t server_idx;
231 u8_t tmr;
232 u8_t retries;
233 u8_t seqno;
234 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
235 u8_t pcb_idx;
236 #endif
237 char name[DNS_MAX_NAME_LENGTH];
238 #if LWIP_IPV4 && LWIP_IPV6
239 u8_t reqaddrtype;
240 #endif /* LWIP_IPV4 && LWIP_IPV6 */
241 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
242 u8_t is_mdns;
243 #endif
244 };
245
246 /** DNS request table entry: used when dns_gehostbyname cannot answer the
247 * request from the DNS table */
248 struct dns_req_entry {
249 /* pointer to callback on DNS query done */
250 dns_found_callback found;
251 /* argument passed to the callback function */
252 void *arg;
253 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
254 u8_t dns_table_idx;
255 #endif
256 #if LWIP_IPV4 && LWIP_IPV6
257 u8_t reqaddrtype;
258 #endif /* LWIP_IPV4 && LWIP_IPV6 */
259 };
260
261 #if DNS_LOCAL_HOSTLIST
262
263 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
264 /** Local host-list. For hostnames in this list, no
265 * external name resolution is performed */
266 static struct local_hostlist_entry *local_hostlist_dynamic;
267 #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
268
269 /** Defining this allows the local_hostlist_static to be placed in a different
270 * linker section (e.g. FLASH) */
271 #ifndef DNS_LOCAL_HOSTLIST_STORAGE_PRE
272 #define DNS_LOCAL_HOSTLIST_STORAGE_PRE static
273 #endif /* DNS_LOCAL_HOSTLIST_STORAGE_PRE */
274 /** Defining this allows the local_hostlist_static to be placed in a different
275 * linker section (e.g. FLASH) */
276 #ifndef DNS_LOCAL_HOSTLIST_STORAGE_POST
277 #define DNS_LOCAL_HOSTLIST_STORAGE_POST
278 #endif /* DNS_LOCAL_HOSTLIST_STORAGE_POST */
279 DNS_LOCAL_HOSTLIST_STORAGE_PRE struct local_hostlist_entry local_hostlist_static[]
280 DNS_LOCAL_HOSTLIST_STORAGE_POST = DNS_LOCAL_HOSTLIST_INIT;
281
282 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
283
284 static void dns_init_local(void);
285 static err_t dns_lookup_local(const char *hostname, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype));
286 #endif /* DNS_LOCAL_HOSTLIST */
287
288
289 /* forward declarations */
290 static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port);
291 static void dns_check_entries(void);
292 static void dns_call_found(u8_t idx, ip_addr_t *addr);
293
294 /*-----------------------------------------------------------------------------
295 * Globals
296 *----------------------------------------------------------------------------*/
297
298 /* DNS variables */
299 static struct udp_pcb *dns_pcbs[DNS_MAX_SOURCE_PORTS];
300 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
301 static u8_t dns_last_pcb_idx;
302 #endif
303 static u8_t dns_seqno;
304 static struct dns_table_entry dns_table[DNS_TABLE_SIZE];
305 static struct dns_req_entry dns_requests[DNS_MAX_REQUESTS];
306 static ip_addr_t dns_servers[DNS_MAX_SERVERS];
307
308 #if LWIP_IPV4
309 const ip_addr_t dns_mquery_v4group = DNS_MQUERY_IPV4_GROUP_INIT;
310 #endif /* LWIP_IPV4 */
311 #if LWIP_IPV6
312 const ip_addr_t dns_mquery_v6group = DNS_MQUERY_IPV6_GROUP_INIT;
313 #endif /* LWIP_IPV6 */
314
315 /**
316 * Initialize the resolver: set up the UDP pcb and configure the default server
317 * (if DNS_SERVER_ADDRESS is set).
318 */
319 void
dns_init(void)320 dns_init(void)
321 {
322 #ifdef DNS_SERVER_ADDRESS
323 /* initialize default DNS server address */
324 ip_addr_t dnsserver;
325 DNS_SERVER_ADDRESS(&dnsserver);
326 dns_setserver(0, &dnsserver);
327 #ifdef DNS_SERVER_ADDRESS_SECONDARY
328 DNS_SERVER_ADDRESS_SECONDARY(&dnsserver);
329 dns_setserver(1, &dnsserver);
330 #endif
331 #endif /* DNS_SERVER_ADDRESS */
332
333 LWIP_ASSERT("sanity check SIZEOF_DNS_QUERY",
334 sizeof(struct dns_query) == SIZEOF_DNS_QUERY);
335 LWIP_ASSERT("sanity check SIZEOF_DNS_ANSWER",
336 sizeof(struct dns_answer) <= SIZEOF_DNS_ANSWER_ASSERT);
337
338 LWIP_DEBUGF(DNS_DEBUG, ("dns_init: initializing\n"));
339
340 /* if dns client not yet initialized... */
341 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) == 0)
342 if (dns_pcbs[0] == NULL) {
343 dns_pcbs[0] = udp_new_ip_type(IPADDR_TYPE_ANY);
344 LWIP_ASSERT("dns_pcbs[0] != NULL", dns_pcbs[0] != NULL);
345
346 /* initialize DNS table not needed (initialized to zero since it is a
347 * global variable) */
348 LWIP_ASSERT("For implicit initialization to work, DNS_STATE_UNUSED needs to be 0",
349 DNS_STATE_UNUSED == 0);
350
351 /* initialize DNS client */
352 udp_bind(dns_pcbs[0], IP_ANY_TYPE, 0);
353 udp_recv(dns_pcbs[0], dns_recv, NULL);
354 }
355 #endif
356
357 #if DNS_LOCAL_HOSTLIST
358 dns_init_local();
359 #endif
360 }
361
362 /**
363 * @ingroup dns
364 * Initialize one of the DNS servers.
365 *
366 * @param numdns the index of the DNS server to set must be < DNS_MAX_SERVERS
367 * @param dnsserver IP address of the DNS server to set
368 */
369 void
dns_setserver(u8_t numdns,const ip_addr_t * dnsserver)370 dns_setserver(u8_t numdns, const ip_addr_t *dnsserver)
371 {
372 if (numdns < DNS_MAX_SERVERS) {
373 if (dnsserver != NULL) {
374 dns_servers[numdns] = (*dnsserver);
375 } else {
376 dns_servers[numdns] = *IP_ADDR_ANY;
377 }
378 }
379 }
380
381 /**
382 * @ingroup dns
383 * Obtain one of the currently configured DNS server.
384 *
385 * @param numdns the index of the DNS server
386 * @return IP address of the indexed DNS server or "ip_addr_any" if the DNS
387 * server has not been configured.
388 */
389 const ip_addr_t *
dns_getserver(u8_t numdns)390 dns_getserver(u8_t numdns)
391 {
392 if (numdns < DNS_MAX_SERVERS) {
393 return &dns_servers[numdns];
394 } else {
395 return IP_ADDR_ANY;
396 }
397 }
398
399 /**
400 * The DNS resolver client timer - handle retries and timeouts and should
401 * be called every DNS_TMR_INTERVAL milliseconds (every second by default).
402 */
403 void
dns_tmr(void)404 dns_tmr(void)
405 {
406 LWIP_DEBUGF(DNS_DEBUG, ("dns_tmr: dns_check_entries\n"));
407 dns_check_entries();
408 }
409
410 #if LWIP_LOWPOWER
411 #include "lwip/lowpower.h"
412 u32_t
dns_tmr_tick(void)413 dns_tmr_tick(void)
414 {
415 u32_t tick = 0;
416 u32_t val;
417 s32_t i;
418
419 for (i = 0; i < DNS_TABLE_SIZE; i++) {
420 if ((dns_table[i].state == DNS_STATE_NEW) ||
421 (dns_table[i].state == DNS_STATE_ASKING)) {
422 LWIP_DEBUGF(LOWPOWER_DEBUG, ("%s tmr tick: 1\n", "dns_tmr_tick"));
423 return 1;
424 }
425 if (dns_table[i].state == DNS_STATE_DONE) {
426 val = dns_table[i].ttl;
427 SET_TMR_TICK(tick, val);
428 }
429 }
430 LWIP_DEBUGF(LOWPOWER_DEBUG, ("%s tmr tick: %u\n", "dns_tmr_tick", tick));
431 return tick;
432 }
433 #endif
434
435 #if DNS_LOCAL_HOSTLIST
436 static void
dns_init_local(void)437 dns_init_local(void)
438 {
439 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT)
440 size_t i;
441 struct local_hostlist_entry *entry;
442 /* Dynamic: copy entries from DNS_LOCAL_HOSTLIST_INIT to list */
443 struct local_hostlist_entry local_hostlist_init[] = DNS_LOCAL_HOSTLIST_INIT;
444 size_t namelen;
445 for (i = 0; i < LWIP_ARRAYSIZE(local_hostlist_init); i++) {
446 struct local_hostlist_entry *init_entry = &local_hostlist_init[i];
447 LWIP_ASSERT("invalid host name (NULL)", init_entry->name != NULL);
448 namelen = strlen(init_entry->name);
449 LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN);
450 entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST);
451 LWIP_ASSERT("mem-error in dns_init_local", entry != NULL);
452 if (entry != NULL) {
453 char *entry_name = (char *)entry + sizeof(struct local_hostlist_entry);
454 MEMCPY(entry_name, init_entry->name, namelen);
455 entry_name[namelen] = 0;
456 entry->name = entry_name;
457 entry->addr = init_entry->addr;
458 entry->next = local_hostlist_dynamic;
459 local_hostlist_dynamic = entry;
460 }
461 }
462 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT) */
463 }
464
465 /**
466 * @ingroup dns
467 * Iterate the local host-list for a hostname.
468 *
469 * @param iterator_fn a function that is called for every entry in the local host-list
470 * @param iterator_arg 3rd argument passed to iterator_fn
471 * @return the number of entries in the local host-list
472 */
473 size_t
dns_local_iterate(dns_found_callback iterator_fn,void * iterator_arg)474 dns_local_iterate(dns_found_callback iterator_fn, void *iterator_arg)
475 {
476 size_t i;
477 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
478 struct local_hostlist_entry *entry = local_hostlist_dynamic;
479 i = 0;
480 while (entry != NULL) {
481 if (iterator_fn != NULL) {
482 iterator_fn(entry->name, &entry->addr, iterator_arg);
483 }
484 i++;
485 entry = entry->next;
486 }
487 #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
488 for (i = 0; i < LWIP_ARRAYSIZE(local_hostlist_static); i++) {
489 if (iterator_fn != NULL) {
490 iterator_fn(local_hostlist_static[i].name, &local_hostlist_static[i].addr, iterator_arg);
491 }
492 }
493 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
494 return i;
495 }
496
497 /**
498 * @ingroup dns
499 * Scans the local host-list for a hostname.
500 *
501 * @param hostname Hostname to look for in the local host-list
502 * @param addr the first IP address for the hostname in the local host-list or
503 * IPADDR_NONE if not found.
504 * @param dns_addrtype - LWIP_DNS_ADDRTYPE_IPV4_IPV6: try to resolve IPv4 (ATTENTION: no fallback here!)
505 * - LWIP_DNS_ADDRTYPE_IPV6_IPV4: try to resolve IPv6 (ATTENTION: no fallback here!)
506 * - LWIP_DNS_ADDRTYPE_IPV4: try to resolve IPv4 only
507 * - LWIP_DNS_ADDRTYPE_IPV6: try to resolve IPv6 only
508 * @return ERR_OK if found, ERR_ARG if not found
509 */
510 err_t
dns_local_lookup(const char * hostname,ip_addr_t * addr,u8_t dns_addrtype)511 dns_local_lookup(const char *hostname, ip_addr_t *addr, u8_t dns_addrtype)
512 {
513 LWIP_UNUSED_ARG(dns_addrtype);
514 return dns_lookup_local(hostname, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype));
515 }
516
517 /* Internal implementation for dns_local_lookup and dns_lookup */
518 static err_t
dns_lookup_local(const char * hostname,ip_addr_t * addr LWIP_DNS_ADDRTYPE_ARG (u8_t dns_addrtype))519 dns_lookup_local(const char *hostname, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype))
520 {
521 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
522 struct local_hostlist_entry *entry = local_hostlist_dynamic;
523 while (entry != NULL) {
524 if ((lwip_stricmp(entry->name, hostname) == 0) &&
525 LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, entry->addr)) {
526 if (addr) {
527 ip_addr_copy(*addr, entry->addr);
528 }
529 return ERR_OK;
530 }
531 entry = entry->next;
532 }
533 #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
534 size_t i;
535 for (i = 0; i < LWIP_ARRAYSIZE(local_hostlist_static); i++) {
536 if ((lwip_stricmp(local_hostlist_static[i].name, hostname) == 0) &&
537 LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, local_hostlist_static[i].addr)) {
538 if (addr) {
539 ip_addr_copy(*addr, local_hostlist_static[i].addr);
540 }
541 return ERR_OK;
542 }
543 }
544 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
545 return ERR_ARG;
546 }
547
548 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
549 /**
550 * @ingroup dns
551 * Remove all entries from the local host-list for a specific hostname
552 * and/or IP address
553 *
554 * @param hostname hostname for which entries shall be removed from the local
555 * host-list
556 * @param addr address for which entries shall be removed from the local host-list
557 * @return the number of removed entries
558 */
559 int
dns_local_removehost(const char * hostname,const ip_addr_t * addr)560 dns_local_removehost(const char *hostname, const ip_addr_t *addr)
561 {
562 int removed = 0;
563 struct local_hostlist_entry *entry = local_hostlist_dynamic;
564 struct local_hostlist_entry *last_entry = NULL;
565 while (entry != NULL) {
566 if (((hostname == NULL) || !lwip_stricmp(entry->name, hostname)) &&
567 ((addr == NULL) || ip_addr_cmp(&entry->addr, addr))) {
568 struct local_hostlist_entry *free_entry;
569 if (last_entry != NULL) {
570 last_entry->next = entry->next;
571 } else {
572 local_hostlist_dynamic = entry->next;
573 }
574 free_entry = entry;
575 entry = entry->next;
576 memp_free(MEMP_LOCALHOSTLIST, free_entry);
577 removed++;
578 } else {
579 last_entry = entry;
580 entry = entry->next;
581 }
582 }
583 return removed;
584 }
585
586 /**
587 * @ingroup dns
588 * Add a hostname/IP address pair to the local host-list.
589 * Duplicates are not checked.
590 *
591 * @param hostname hostname of the new entry
592 * @param addr IP address of the new entry
593 * @return ERR_OK if succeeded or ERR_MEM on memory error
594 */
595 err_t
dns_local_addhost(const char * hostname,const ip_addr_t * addr)596 dns_local_addhost(const char *hostname, const ip_addr_t *addr)
597 {
598 struct local_hostlist_entry *entry;
599 size_t namelen;
600 char *entry_name;
601 LWIP_ASSERT("invalid host name (NULL)", hostname != NULL);
602 namelen = strlen(hostname);
603 LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN);
604 entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST);
605 if (entry == NULL) {
606 return ERR_MEM;
607 }
608 entry_name = (char *)entry + sizeof(struct local_hostlist_entry);
609 MEMCPY(entry_name, hostname, namelen);
610 entry_name[namelen] = 0;
611 entry->name = entry_name;
612 ip_addr_copy(entry->addr, *addr);
613 entry->next = local_hostlist_dynamic;
614 local_hostlist_dynamic = entry;
615 return ERR_OK;
616 }
617 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC*/
618 #endif /* DNS_LOCAL_HOSTLIST */
619
620 /**
621 * @ingroup dns
622 * Look up a hostname in the array of known hostnames.
623 *
624 * @note This function only looks in the internal array of known
625 * hostnames, it does not send out a query for the hostname if none
626 * was found. The function dns_enqueue() can be used to send a query
627 * for a hostname.
628 *
629 * @param name the hostname to look up
630 * @param addr the hostname's IP address, as u32_t (instead of ip_addr_t to
631 * better check for failure: != IPADDR_NONE) or IPADDR_NONE if the hostname
632 * was not found in the cached dns_table.
633 * @return ERR_OK if found, ERR_ARG if not found
634 */
635 static err_t
dns_lookup(const char * name,ip_addr_t * addr LWIP_DNS_ADDRTYPE_ARG (u8_t dns_addrtype))636 dns_lookup(const char *name, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype))
637 {
638 u8_t i;
639 #if DNS_LOCAL_HOSTLIST
640 if (dns_lookup_local(name, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)) == ERR_OK) {
641 return ERR_OK;
642 }
643 #endif /* DNS_LOCAL_HOSTLIST */
644 #ifdef DNS_LOOKUP_LOCAL_EXTERN
645 if (DNS_LOOKUP_LOCAL_EXTERN(name, addr, LWIP_DNS_ADDRTYPE_ARG_OR_ZERO(dns_addrtype)) == ERR_OK) {
646 return ERR_OK;
647 }
648 #endif /* DNS_LOOKUP_LOCAL_EXTERN */
649
650 /* Walk through name list, return entry if found. If not, return NULL. */
651 for (i = 0; i < DNS_TABLE_SIZE; ++i) {
652 if ((dns_table[i].state == DNS_STATE_DONE) &&
653 (lwip_strnicmp(name, dns_table[i].name, sizeof(dns_table[i].name)) == 0) &&
654 LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, dns_table[i].ipaddr)) {
655 LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name));
656 ip_addr_debug_print_val(DNS_DEBUG, dns_table[i].ipaddr);
657 LWIP_DEBUGF(DNS_DEBUG, ("\n"));
658 if (addr) {
659 ip_addr_copy(*addr, dns_table[i].ipaddr);
660 }
661 return ERR_OK;
662 }
663 }
664
665 return ERR_ARG;
666 }
667
668 /**
669 * Compare the "dotted" name "query" with the encoded name "response"
670 * to make sure an answer from the DNS server matches the current dns_table
671 * entry (otherwise, answers might arrive late for hostname not on the list
672 * any more).
673 *
674 * For now, this function compares case-insensitive to cope with all kinds of
675 * servers. This also means that "dns 0x20 bit encoding" must be checked
676 * externally, if we want to implement it.
677 * Currently, the request is sent exactly as passed in by he user request.
678 *
679 * @param query hostname (not encoded) from the dns_table
680 * @param p pbuf containing the encoded hostname in the DNS response
681 * @param start_offset offset into p where the name starts
682 * @return 0xFFFF: names differ, other: names equal -> offset behind name
683 */
684 static u16_t
dns_compare_name(const char * query,struct pbuf * p,u16_t start_offset)685 dns_compare_name(const char *query, struct pbuf *p, u16_t start_offset)
686 {
687 int n;
688 u16_t response_offset = start_offset;
689
690 do {
691 n = pbuf_try_get_at(p, response_offset);
692 if ((n < 0) || (response_offset == 0xFFFF)) {
693 /* error or overflow */
694 return 0xFFFF;
695 }
696 response_offset++;
697 /** @see RFC 1035 - 4.1.4. Message compression */
698 if ((n & 0xc0) == 0xc0) {
699 /* Compressed name: cannot be equal since we don't send them */
700 return 0xFFFF;
701 } else {
702 /* Not compressed name */
703 while (n > 0) {
704 int c = pbuf_try_get_at(p, response_offset);
705 if (c < 0) {
706 return 0xFFFF;
707 }
708 if (lwip_tolower((*query)) != lwip_tolower((u8_t)c)) {
709 return 0xFFFF;
710 }
711 if (response_offset == 0xFFFF) {
712 /* would overflow */
713 return 0xFFFF;
714 }
715 response_offset++;
716 ++query;
717 --n;
718 }
719 ++query;
720 }
721 n = pbuf_try_get_at(p, response_offset);
722 if (n < 0) {
723 return 0xFFFF;
724 }
725 } while (n != 0);
726
727 if (response_offset == 0xFFFF) {
728 /* would overflow */
729 return 0xFFFF;
730 }
731 return (u16_t)(response_offset + 1);
732 }
733
734 /**
735 * Walk through a compact encoded DNS name and return the end of the name.
736 *
737 * @param p pbuf containing the name
738 * @param query_idx start index into p pointing to encoded DNS name in the DNS server response
739 * @return index to end of the name
740 */
741 static u16_t
dns_skip_name(struct pbuf * p,u16_t query_idx)742 dns_skip_name(struct pbuf *p, u16_t query_idx)
743 {
744 int n;
745 u16_t offset = query_idx;
746
747 do {
748 n = pbuf_try_get_at(p, offset++);
749 if ((n < 0) || (offset == 0)) {
750 return 0xFFFF;
751 }
752 /** @see RFC 1035 - 4.1.4. Message compression */
753 if ((n & 0xc0) == 0xc0) {
754 /* Compressed name: since we only want to skip it (not check it), stop here */
755 break;
756 } else {
757 /* Not compressed name */
758 if (offset + n >= p->tot_len) {
759 return 0xFFFF;
760 }
761 offset = (u16_t)(offset + n);
762 }
763 n = pbuf_try_get_at(p, offset);
764 if (n < 0) {
765 return 0xFFFF;
766 }
767 } while (n != 0);
768
769 if (offset == 0xFFFF) {
770 return 0xFFFF;
771 }
772 return (u16_t)(offset + 1);
773 }
774
775 /**
776 * Send a DNS query packet.
777 *
778 * @param idx the DNS table entry index for which to send a request
779 * @return ERR_OK if packet is sent; an err_t indicating the problem otherwise
780 */
781 static err_t
dns_send(u8_t idx)782 dns_send(u8_t idx)
783 {
784 err_t err;
785 struct dns_hdr hdr;
786 struct dns_query qry;
787 struct pbuf *p;
788 u16_t query_idx, copy_len;
789 const char *hostname, *hostname_part;
790 u8_t n;
791 u8_t pcb_idx;
792 struct dns_table_entry *entry = &dns_table[idx];
793
794 LWIP_DEBUGF(DNS_DEBUG, ("dns_send: dns_servers[%"U16_F"] \"%s\": request\n",
795 (u16_t)(entry->server_idx), entry->name));
796 LWIP_ASSERT("dns server out of array", entry->server_idx < DNS_MAX_SERVERS);
797 if (ip_addr_isany_val(dns_servers[entry->server_idx])
798 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
799 && !entry->is_mdns
800 #endif
801 ) {
802 /* DNS server not valid anymore, e.g. PPP netif has been shut down */
803 /* call specified callback function if provided */
804 dns_call_found(idx, NULL);
805 /* flush this entry */
806 entry->state = DNS_STATE_UNUSED;
807 return ERR_OK;
808 }
809
810 /* if here, we have either a new query or a retry on a previous query to process */
811 #if LWIP_ENABLE_DISTRIBUTED_NET && !LWIP_USE_GET_HOST_BY_NAME_EXTERNAL
812 if (is_distributed_net_enabled()) {
813 p = pbuf_alloc(PBUF_TRANSPORT,
814 (u16_t)(sizeof(udp_data) + SIZEOF_DNS_HDR + strlen(entry->name) + 2 + SIZEOF_DNS_QUERY), PBUF_RAM);
815 } else {
816 p = pbuf_alloc(PBUF_TRANSPORT, (u16_t)(SIZEOF_DNS_HDR + strlen(entry->name) + 2 + SIZEOF_DNS_QUERY), PBUF_RAM);
817 }
818 #else
819 p = pbuf_alloc(PBUF_TRANSPORT, (u16_t)(SIZEOF_DNS_HDR + strlen(entry->name) + 2 +
820 SIZEOF_DNS_QUERY), PBUF_RAM);
821 #endif
822
823 if (p != NULL) {
824 const ip_addr_t *dst;
825 u16_t dst_port;
826 /* fill dns header */
827 memset(&hdr, 0, SIZEOF_DNS_HDR);
828 hdr.id = lwip_htons(entry->txid);
829 hdr.flags1 = DNS_FLAG1_RD;
830 hdr.numquestions = PP_HTONS(1);
831 #if LWIP_ENABLE_DISTRIBUTED_NET && !LWIP_USE_GET_HOST_BY_NAME_EXTERNAL
832 if (is_distributed_net_enabled()) {
833 udp_data udp_data_hdr = {0};
834 (void)memset_s(&udp_data_hdr, sizeof(udp_data_hdr), 0, sizeof(udp_data_hdr));
835 dst = &dns_servers[entry->server_idx];
836
837 #if LWIP_IPV6
838 (void)strcpy_s(udp_data_hdr.dest_addr, sizeof(udp_data_hdr.dest_addr), ip4addr_ntoa(&dst->u_addr.ip4));
839 #else
840 (void)strcpy_s(udp_data_hdr.dest_addr, sizeof(udp_data_hdr.dest_addr), ip4addr_ntoa(dst));
841 #endif
842
843 udp_data_hdr.dest_port = DNS_SERVER_PORT;
844
845 pbuf_take(p, &udp_data_hdr, sizeof(udp_data_hdr));
846 pbuf_take_at(p, &hdr, SIZEOF_DNS_HDR, sizeof(udp_data_hdr));
847 } else {
848 pbuf_take(p, &hdr, SIZEOF_DNS_HDR);
849 }
850 #else
851 pbuf_take(p, &hdr, SIZEOF_DNS_HDR);
852 #endif
853 hostname = entry->name;
854 --hostname;
855
856 /* convert hostname into suitable query format. */
857 #if LWIP_ENABLE_DISTRIBUTED_NET && !LWIP_USE_GET_HOST_BY_NAME_EXTERNAL
858 if (is_distributed_net_enabled()) {
859 query_idx = sizeof(udp_data) + SIZEOF_DNS_HDR;
860 } else {
861 query_idx = SIZEOF_DNS_HDR;
862 }
863 #else
864 query_idx = SIZEOF_DNS_HDR;
865 #endif
866 do {
867 ++hostname;
868 hostname_part = hostname;
869 for (n = 0; *hostname != '.' && *hostname != 0; ++hostname) {
870 ++n;
871 }
872 copy_len = (u16_t)(hostname - hostname_part);
873 if (query_idx + n + 1 > 0xFFFF) {
874 /* u16_t overflow */
875 goto overflow_return;
876 }
877 pbuf_put_at(p, query_idx, n);
878 pbuf_take_at(p, hostname_part, copy_len, (u16_t)(query_idx + 1));
879 query_idx = (u16_t)(query_idx + n + 1);
880 } while (*hostname != 0);
881 pbuf_put_at(p, query_idx, 0);
882 query_idx++;
883
884 /* fill dns query */
885 if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype)) {
886 qry.type = PP_HTONS(DNS_RRTYPE_AAAA);
887 } else {
888 qry.type = PP_HTONS(DNS_RRTYPE_A);
889 }
890 qry.cls = PP_HTONS(DNS_RRCLASS_IN);
891 pbuf_take_at(p, &qry, SIZEOF_DNS_QUERY, query_idx);
892
893 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
894 pcb_idx = entry->pcb_idx;
895 #else
896 pcb_idx = 0;
897 #endif
898 /* send dns packet */
899 LWIP_DEBUGF(DNS_DEBUG, ("sending DNS request ID %d for name \"%s\" to server %d\r\n",
900 entry->txid, entry->name, entry->server_idx));
901 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
902 if (entry->is_mdns) {
903 dst_port = DNS_MQUERY_PORT;
904 #if LWIP_IPV6
905 if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype)) {
906 dst = &dns_mquery_v6group;
907 }
908 #endif
909 #if LWIP_IPV4 && LWIP_IPV6
910 else
911 #endif
912 #if LWIP_IPV4
913 {
914 dst = &dns_mquery_v4group;
915 }
916 #endif
917 } else
918 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
919 {
920 dst_port = DNS_SERVER_PORT;
921 dst = &dns_servers[entry->server_idx];
922 }
923 #if LWIP_ENABLE_DISTRIBUTED_NET && !LWIP_USE_GET_HOST_BY_NAME_EXTERNAL
924 if (is_distributed_net_enabled()) {
925 ip_addr_t local_addr = {0};
926 dst_port = get_local_udp_server_port();
927
928 #if LWIP_IPV6
929 local_addr.u_addr.ip4.addr = ipaddr_addr(LOCAL_SERVER_IP);
930 local_addr.type = IPADDR_TYPE_V4;
931 #else
932 local_addr.addr = ipaddr_addr(LOCAL_SERVER_IP);
933 #endif
934 #if (defined(EMUI_WEB_CLIENT))
935 DISTRIBUTED_NET_START_UDP_SERVER();
936 #endif
937 err = udp_sendto(dns_pcbs[pcb_idx], p, &local_addr, dst_port);
938 } else {
939 err = udp_sendto(dns_pcbs[pcb_idx], p, dst, dst_port);
940 }
941 #else
942 err = udp_sendto(dns_pcbs[pcb_idx], p, dst, dst_port);
943 #endif
944
945 /* free pbuf */
946 pbuf_free(p);
947 } else {
948 err = ERR_MEM;
949 }
950
951 return err;
952 overflow_return:
953 pbuf_free(p);
954 return ERR_VAL;
955 }
956
957 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
958 static struct udp_pcb *
dns_alloc_random_port(void)959 dns_alloc_random_port(void)
960 {
961 err_t err;
962 struct udp_pcb *pcb;
963
964 pcb = udp_new_ip_type(IPADDR_TYPE_ANY);
965 if (pcb == NULL) {
966 /* out of memory, have to reuse an existing pcb */
967 return NULL;
968 }
969 do {
970 u16_t port = (u16_t)DNS_RAND_TXID();
971 if (DNS_PORT_ALLOWED(port)) {
972 err = udp_bind(pcb, IP_ANY_TYPE, port);
973 } else {
974 /* this port is not allowed, try again */
975 err = ERR_USE;
976 }
977 } while (err == ERR_USE);
978 if (err != ERR_OK) {
979 udp_remove(pcb);
980 return NULL;
981 }
982 udp_recv(pcb, dns_recv, NULL);
983 return pcb;
984 }
985
986 /**
987 * dns_alloc_pcb() - allocates a new pcb (or reuses an existing one) to be used
988 * for sending a request
989 *
990 * @return an index into dns_pcbs
991 */
992 static u8_t
dns_alloc_pcb(void)993 dns_alloc_pcb(void)
994 {
995 u8_t i;
996 u8_t idx;
997
998 for (i = 0; i < DNS_MAX_SOURCE_PORTS; i++) {
999 if (dns_pcbs[i] == NULL) {
1000 break;
1001 }
1002 }
1003 if (i < DNS_MAX_SOURCE_PORTS) {
1004 dns_pcbs[i] = dns_alloc_random_port();
1005 if (dns_pcbs[i] != NULL) {
1006 /* succeeded */
1007 dns_last_pcb_idx = i;
1008 return i;
1009 }
1010 }
1011 /* if we come here, creating a new UDP pcb failed, so we have to use
1012 an already existing one (so overflow is no issue) */
1013 for (i = 0, idx = (u8_t)(dns_last_pcb_idx + 1); i < DNS_MAX_SOURCE_PORTS; i++, idx++) {
1014 if (idx >= DNS_MAX_SOURCE_PORTS) {
1015 idx = 0;
1016 }
1017 if (dns_pcbs[idx] != NULL) {
1018 dns_last_pcb_idx = idx;
1019 return idx;
1020 }
1021 }
1022 return DNS_MAX_SOURCE_PORTS;
1023 }
1024 #endif /* ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0) */
1025
1026 /**
1027 * dns_call_found() - call the found callback and check if there are duplicate
1028 * entries for the given hostname. If there are any, their found callback will
1029 * be called and they will be removed.
1030 *
1031 * @param idx dns table index of the entry that is resolved or removed
1032 * @param addr IP address for the hostname (or NULL on error or memory shortage)
1033 */
1034 static void
dns_call_found(u8_t idx,ip_addr_t * addr)1035 dns_call_found(u8_t idx, ip_addr_t *addr)
1036 {
1037 #if ((LWIP_DNS_SECURE & (LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING | LWIP_DNS_SECURE_RAND_SRC_PORT)) != 0)
1038 u8_t i;
1039 #endif
1040
1041 #if LWIP_IPV4 && LWIP_IPV6
1042 if (addr != NULL) {
1043 /* check that address type matches the request and adapt the table entry */
1044 if (IP_IS_V6_VAL(*addr)) {
1045 LWIP_ASSERT("invalid response", LWIP_DNS_ADDRTYPE_IS_IPV6(dns_table[idx].reqaddrtype));
1046 dns_table[idx].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV6;
1047 } else {
1048 LWIP_ASSERT("invalid response", !LWIP_DNS_ADDRTYPE_IS_IPV6(dns_table[idx].reqaddrtype));
1049 dns_table[idx].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV4;
1050 }
1051 }
1052 #endif /* LWIP_IPV4 && LWIP_IPV6 */
1053
1054 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
1055 for (i = 0; i < DNS_MAX_REQUESTS; i++) {
1056 if (dns_requests[i].found && (dns_requests[i].dns_table_idx == idx)) {
1057 (*dns_requests[i].found)(dns_table[idx].name, addr, dns_requests[i].arg);
1058 /* flush this entry */
1059 dns_requests[i].found = NULL;
1060 }
1061 }
1062 #else
1063 if (dns_requests[idx].found) {
1064 (*dns_requests[idx].found)(dns_table[idx].name, addr, dns_requests[idx].arg);
1065 }
1066 dns_requests[idx].found = NULL;
1067 #endif
1068 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
1069 /* close the pcb used unless other request are using it */
1070 for (i = 0; i < DNS_MAX_REQUESTS; i++) {
1071 if (i == idx) {
1072 continue; /* only check other requests */
1073 }
1074 if (dns_table[i].state == DNS_STATE_ASKING) {
1075 if (dns_table[i].pcb_idx == dns_table[idx].pcb_idx) {
1076 /* another request is still using the same pcb */
1077 dns_table[idx].pcb_idx = DNS_MAX_SOURCE_PORTS;
1078 break;
1079 }
1080 }
1081 }
1082 if (dns_table[idx].pcb_idx < DNS_MAX_SOURCE_PORTS) {
1083 /* if we come here, the pcb is not used any more and can be removed */
1084 udp_remove(dns_pcbs[dns_table[idx].pcb_idx]);
1085 dns_pcbs[dns_table[idx].pcb_idx] = NULL;
1086 dns_table[idx].pcb_idx = DNS_MAX_SOURCE_PORTS;
1087 }
1088 #endif
1089 }
1090
1091 /* Create a query transmission ID that is unique for all outstanding queries */
1092 static u16_t
dns_create_txid(void)1093 dns_create_txid(void)
1094 {
1095 u16_t txid;
1096 u8_t i;
1097
1098 again:
1099 txid = (u16_t)DNS_RAND_TXID();
1100
1101 /* check whether the ID is unique */
1102 for (i = 0; i < DNS_TABLE_SIZE; i++) {
1103 if ((dns_table[i].state == DNS_STATE_ASKING) &&
1104 (dns_table[i].txid == txid)) {
1105 /* ID already used by another pending query */
1106 goto again;
1107 }
1108 }
1109
1110 return txid;
1111 }
1112
1113 /**
1114 * Check whether there are other backup DNS servers available to try
1115 */
1116 static u8_t
dns_backupserver_available(struct dns_table_entry * pentry)1117 dns_backupserver_available(struct dns_table_entry *pentry)
1118 {
1119 u8_t ret = 0;
1120
1121 if (pentry) {
1122 if ((pentry->server_idx + 1 < DNS_MAX_SERVERS) && !ip_addr_isany_val(dns_servers[pentry->server_idx + 1])) {
1123 ret = 1;
1124 }
1125 }
1126
1127 return ret;
1128 }
1129
1130 /**
1131 * dns_check_entry() - see if entry has not yet been queried and, if so, sends out a query.
1132 * Check an entry in the dns_table:
1133 * - send out query for new entries
1134 * - retry old pending entries on timeout (also with different servers)
1135 * - remove completed entries from the table if their TTL has expired
1136 *
1137 * @param i index of the dns_table entry to check
1138 */
1139 static void
dns_check_entry(u8_t i)1140 dns_check_entry(u8_t i)
1141 {
1142 err_t err;
1143 struct dns_table_entry *entry = &dns_table[i];
1144
1145 LWIP_ASSERT("array index out of bounds", i < DNS_TABLE_SIZE);
1146
1147 switch (entry->state) {
1148 case DNS_STATE_NEW:
1149 /* initialize new entry */
1150 entry->txid = dns_create_txid();
1151 entry->state = DNS_STATE_ASKING;
1152 entry->server_idx = 0;
1153 entry->tmr = 1;
1154 entry->retries = 0;
1155
1156 /* send DNS packet for this entry */
1157 err = dns_send(i);
1158 if (err != ERR_OK) {
1159 LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
1160 ("dns_send returned error: %s\n", lwip_strerr(err)));
1161 }
1162 break;
1163 case DNS_STATE_ASKING:
1164 if (--entry->tmr == 0) {
1165 if (++entry->retries == DNS_MAX_RETRIES) {
1166 if (dns_backupserver_available(entry)
1167 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
1168 && !entry->is_mdns
1169 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
1170 ) {
1171 /* change of server */
1172 entry->server_idx++;
1173 entry->tmr = 1;
1174 entry->retries = 0;
1175 } else {
1176 LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": timeout\n", entry->name));
1177 /* call specified callback function if provided */
1178 dns_call_found(i, NULL);
1179 /* flush this entry */
1180 entry->state = DNS_STATE_UNUSED;
1181 break;
1182 }
1183 } else {
1184 /* wait longer for the next retry */
1185 entry->tmr = entry->retries;
1186 }
1187
1188 /* send DNS packet for this entry */
1189 err = dns_send(i);
1190 if (err != ERR_OK) {
1191 LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
1192 ("dns_send returned error: %s\n", lwip_strerr(err)));
1193 }
1194 }
1195 break;
1196 case DNS_STATE_DONE:
1197 /* if the time to live is nul */
1198 if ((entry->ttl == 0) || (--entry->ttl == 0)) {
1199 LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": flush\n", entry->name));
1200 /* flush this entry, there cannot be any related pending entries in this state */
1201 entry->state = DNS_STATE_UNUSED;
1202 }
1203 break;
1204 case DNS_STATE_UNUSED:
1205 /* nothing to do */
1206 break;
1207 default:
1208 LWIP_ASSERT("unknown dns_table entry state:", 0);
1209 break;
1210 }
1211 }
1212
1213 /**
1214 * Call dns_check_entry for each entry in dns_table - check all entries.
1215 */
1216 static void
dns_check_entries(void)1217 dns_check_entries(void)
1218 {
1219 u8_t i;
1220
1221 for (i = 0; i < DNS_TABLE_SIZE; ++i) {
1222 dns_check_entry(i);
1223 }
1224 }
1225
1226 /**
1227 * Save TTL and call dns_call_found for correct response.
1228 */
1229 static void
dns_correct_response(u8_t idx,u32_t ttl)1230 dns_correct_response(u8_t idx, u32_t ttl)
1231 {
1232 struct dns_table_entry *entry = &dns_table[idx];
1233
1234 entry->state = DNS_STATE_DONE;
1235
1236 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", entry->name));
1237 ip_addr_debug_print_val(DNS_DEBUG, entry->ipaddr);
1238 LWIP_DEBUGF(DNS_DEBUG, ("\n"));
1239
1240 /* read the answer resource record's TTL, and maximize it if needed */
1241 entry->ttl = ttl;
1242 if (entry->ttl > DNS_MAX_TTL) {
1243 entry->ttl = DNS_MAX_TTL;
1244 }
1245 dns_call_found(idx, &entry->ipaddr);
1246
1247 if (entry->ttl == 0) {
1248 /* RFC 883, page 29: "Zero values are
1249 interpreted to mean that the RR can only be used for the
1250 transaction in progress, and should not be cached."
1251 -> flush this entry now */
1252 /* entry reused during callback? */
1253 if (entry->state == DNS_STATE_DONE) {
1254 entry->state = DNS_STATE_UNUSED;
1255 }
1256 }
1257 }
1258
1259 /**
1260 * Receive input function for DNS response packets arriving for the dns UDP pcb.
1261 */
1262 static void
dns_recv(void * arg,struct udp_pcb * pcb,struct pbuf * p,const ip_addr_t * addr,u16_t port)1263 dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
1264 {
1265 u8_t i;
1266 u16_t txid;
1267 u16_t res_idx;
1268 struct dns_hdr hdr;
1269 struct dns_answer ans;
1270 struct dns_query qry;
1271 u16_t nquestions, nanswers;
1272
1273 LWIP_UNUSED_ARG(arg);
1274 LWIP_UNUSED_ARG(pcb);
1275 LWIP_UNUSED_ARG(port);
1276
1277 /* is the dns message big enough ? */
1278 if (p->tot_len < (SIZEOF_DNS_HDR + SIZEOF_DNS_QUERY)) {
1279 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too small\n"));
1280 /* free pbuf and return */
1281 goto ignore_packet;
1282 }
1283
1284 /* copy dns payload inside static buffer for processing */
1285 if (pbuf_copy_partial(p, &hdr, SIZEOF_DNS_HDR, 0) == SIZEOF_DNS_HDR) {
1286 /* Match the ID in the DNS header with the name table. */
1287 txid = lwip_htons(hdr.id);
1288 for (i = 0; i < DNS_TABLE_SIZE; i++) {
1289 struct dns_table_entry *entry = &dns_table[i];
1290 if ((entry->state == DNS_STATE_ASKING) &&
1291 (entry->txid == txid)) {
1292
1293 /* We only care about the question(s) and the answers. The authrr
1294 and the extrarr are simply discarded. */
1295 nquestions = lwip_htons(hdr.numquestions);
1296 nanswers = lwip_htons(hdr.numanswers);
1297
1298 /* Check for correct response. */
1299 if ((hdr.flags1 & DNS_FLAG1_RESPONSE) == 0) {
1300 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": not a response\n", entry->name));
1301 goto ignore_packet; /* ignore this packet */
1302 }
1303 if (nquestions != 1) {
1304 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
1305 goto ignore_packet; /* ignore this packet */
1306 }
1307
1308 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
1309 if (!entry->is_mdns)
1310 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
1311 {
1312 /* Check whether response comes from the same network address to which the
1313 question was sent. (RFC 5452) */
1314 #if LWIP_ENABLE_DISTRIBUTED_NET && !LWIP_USE_GET_HOST_BY_NAME_EXTERNAL
1315 if (is_distributed_net_enabled()) {
1316 #if LWIP_IPV6
1317 if (addr->type != IPADDR_TYPE_V4 || addr->u_addr.ip4.addr != ipaddr_addr(LOCAL_SERVER_IP) ||
1318 port != get_local_udp_server_port()) {
1319 goto ignore_packet; /* ignore this packet */
1320 }
1321 #else
1322 if (addr->addr != ipaddr_addr(LOCAL_SERVER_IP) || port != get_local_udp_server_port()) {
1323 goto ignore_packet; /* ignore this packet */
1324 }
1325 #endif
1326 } else {
1327 if (!ip_addr_cmp(addr, &dns_servers[entry->server_idx])) {
1328 goto ignore_packet; /* ignore this packet */
1329 }
1330 }
1331 #else
1332 if (!ip_addr_cmp(addr, &dns_servers[entry->server_idx])) {
1333 goto ignore_packet; /* ignore this packet */
1334 }
1335 #endif
1336 }
1337
1338 /* Check if the name in the "question" part match with the name in the entry and
1339 skip it if equal. */
1340 res_idx = dns_compare_name(entry->name, p, SIZEOF_DNS_HDR);
1341 if (res_idx == 0xFFFF) {
1342 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
1343 goto ignore_packet; /* ignore this packet */
1344 }
1345
1346 /* check if "question" part matches the request */
1347 if (pbuf_copy_partial(p, &qry, SIZEOF_DNS_QUERY, res_idx) != SIZEOF_DNS_QUERY) {
1348 goto ignore_packet; /* ignore this packet */
1349 }
1350 if ((qry.cls != PP_HTONS(DNS_RRCLASS_IN)) ||
1351 (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype) && (qry.type != PP_HTONS(DNS_RRTYPE_AAAA))) ||
1352 (!LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype) && (qry.type != PP_HTONS(DNS_RRTYPE_A)))) {
1353 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
1354 goto ignore_packet; /* ignore this packet */
1355 }
1356 /* skip the rest of the "question" part */
1357 if (res_idx + SIZEOF_DNS_QUERY > 0xFFFF) {
1358 goto ignore_packet;
1359 }
1360 res_idx = (u16_t)(res_idx + SIZEOF_DNS_QUERY);
1361
1362 /* Check for error. If so, call callback to inform. */
1363 if (hdr.flags2 & DNS_FLAG2_ERR_MASK) {
1364 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", entry->name));
1365
1366 /* if there is another backup DNS server to try
1367 * then don't stop the DNS request
1368 */
1369 if (dns_backupserver_available(entry)) {
1370 /* avoid retrying the same server */
1371 entry->retries = DNS_MAX_RETRIES-1;
1372 entry->tmr = 1;
1373
1374 /* contact next available server for this entry */
1375 dns_check_entry(i);
1376
1377 goto ignore_packet;
1378 }
1379 } else {
1380 while ((nanswers > 0) && (res_idx < p->tot_len)) {
1381 /* skip answer resource record's host name */
1382 res_idx = dns_skip_name(p, res_idx);
1383 if (res_idx == 0xFFFF) {
1384 goto ignore_packet; /* ignore this packet */
1385 }
1386
1387 /* Check for IP address type and Internet class. Others are discarded. */
1388 if (pbuf_copy_partial(p, &ans, SIZEOF_DNS_ANSWER, res_idx) != SIZEOF_DNS_ANSWER) {
1389 goto ignore_packet; /* ignore this packet */
1390 }
1391 if (res_idx + SIZEOF_DNS_ANSWER > 0xFFFF) {
1392 goto ignore_packet;
1393 }
1394 res_idx = (u16_t)(res_idx + SIZEOF_DNS_ANSWER);
1395
1396 if (ans.cls == PP_HTONS(DNS_RRCLASS_IN)) {
1397 #if LWIP_IPV4
1398 if ((ans.type == PP_HTONS(DNS_RRTYPE_A)) && (ans.len == PP_HTONS(sizeof(ip4_addr_t)))) {
1399 #if LWIP_IPV4 && LWIP_IPV6
1400 if (!LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype))
1401 #endif /* LWIP_IPV4 && LWIP_IPV6 */
1402 {
1403 ip4_addr_t ip4addr;
1404 /* read the IP address after answer resource record's header */
1405 if (pbuf_copy_partial(p, &ip4addr, sizeof(ip4_addr_t), res_idx) != sizeof(ip4_addr_t)) {
1406 goto ignore_packet; /* ignore this packet */
1407 }
1408 ip_addr_copy_from_ip4(dns_table[i].ipaddr, ip4addr);
1409 pbuf_free(p);
1410 /* handle correct response */
1411 dns_correct_response(i, lwip_ntohl(ans.ttl));
1412 return;
1413 }
1414 }
1415 #endif /* LWIP_IPV4 */
1416 #if LWIP_IPV6
1417 if ((ans.type == PP_HTONS(DNS_RRTYPE_AAAA)) && (ans.len == PP_HTONS(sizeof(ip6_addr_p_t)))) {
1418 #if LWIP_IPV4 && LWIP_IPV6
1419 if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype))
1420 #endif /* LWIP_IPV4 && LWIP_IPV6 */
1421 {
1422 ip6_addr_p_t ip6addr;
1423 /* read the IP address after answer resource record's header */
1424 if (pbuf_copy_partial(p, &ip6addr, sizeof(ip6_addr_p_t), res_idx) != sizeof(ip6_addr_p_t)) {
1425 goto ignore_packet; /* ignore this packet */
1426 }
1427 /* @todo: scope ip6addr? Might be required for link-local addresses at least? */
1428 ip_addr_copy_from_ip6_packed(dns_table[i].ipaddr, ip6addr);
1429 pbuf_free(p);
1430 /* handle correct response */
1431 dns_correct_response(i, lwip_ntohl(ans.ttl));
1432 return;
1433 }
1434 }
1435 #endif /* LWIP_IPV6 */
1436 }
1437 /* skip this answer */
1438 if ((int)(res_idx + lwip_htons(ans.len)) > 0xFFFF) {
1439 goto ignore_packet; /* ignore this packet */
1440 }
1441 res_idx = (u16_t)(res_idx + lwip_htons(ans.len));
1442 --nanswers;
1443 }
1444 #if LWIP_IPV4 && LWIP_IPV6
1445 if ((entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) ||
1446 (entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV6_IPV4)) {
1447 if (entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) {
1448 /* IPv4 failed, try IPv6 */
1449 dns_table[i].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV6;
1450 } else {
1451 /* IPv6 failed, try IPv4 */
1452 dns_table[i].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV4;
1453 }
1454 pbuf_free(p);
1455 dns_table[i].state = DNS_STATE_NEW;
1456 dns_check_entry(i);
1457 return;
1458 }
1459 #endif /* LWIP_IPV4 && LWIP_IPV6 */
1460 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in response\n", entry->name));
1461 }
1462 /* call callback to indicate error, clean up memory and return */
1463 pbuf_free(p);
1464 dns_call_found(i, NULL);
1465 dns_table[i].state = DNS_STATE_UNUSED;
1466 return;
1467 }
1468 }
1469 }
1470
1471 ignore_packet:
1472 /* deallocate memory and return */
1473 pbuf_free(p);
1474 return;
1475 }
1476
1477 /**
1478 * Queues a new hostname to resolve and sends out a DNS query for that hostname
1479 *
1480 * @param name the hostname that is to be queried
1481 * @param hostnamelen length of the hostname
1482 * @param found a callback function to be called on success, failure or timeout
1483 * @param callback_arg argument to pass to the callback function
1484 * @return err_t return code.
1485 */
1486 static err_t
dns_enqueue(const char * name,size_t hostnamelen,dns_found_callback found,void * callback_arg LWIP_DNS_ADDRTYPE_ARG (u8_t dns_addrtype)LWIP_DNS_ISMDNS_ARG (u8_t is_mdns))1487 dns_enqueue(const char *name, size_t hostnamelen, dns_found_callback found,
1488 void *callback_arg LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype) LWIP_DNS_ISMDNS_ARG(u8_t is_mdns))
1489 {
1490 u8_t i;
1491 u8_t lseq, lseqi;
1492 struct dns_table_entry *entry = NULL;
1493 size_t namelen;
1494 struct dns_req_entry *req;
1495
1496 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
1497 u8_t r;
1498 /* check for duplicate entries */
1499 for (i = 0; i < DNS_TABLE_SIZE; i++) {
1500 if ((dns_table[i].state == DNS_STATE_ASKING) &&
1501 (lwip_strnicmp(name, dns_table[i].name, sizeof(dns_table[i].name)) == 0)) {
1502 #if LWIP_IPV4 && LWIP_IPV6
1503 if (dns_table[i].reqaddrtype != dns_addrtype) {
1504 /* requested address types don't match
1505 this can lead to 2 concurrent requests, but mixing the address types
1506 for the same host should not be that common */
1507 continue;
1508 }
1509 #endif /* LWIP_IPV4 && LWIP_IPV6 */
1510 /* this is a duplicate entry, find a free request entry */
1511 for (r = 0; r < DNS_MAX_REQUESTS; r++) {
1512 if (dns_requests[r].found == 0) {
1513 dns_requests[r].found = found;
1514 dns_requests[r].arg = callback_arg;
1515 dns_requests[r].dns_table_idx = i;
1516 LWIP_DNS_SET_ADDRTYPE(dns_requests[r].reqaddrtype, dns_addrtype);
1517 LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": duplicate request\n", name));
1518 return ERR_INPROGRESS;
1519 }
1520 }
1521 }
1522 }
1523 /* no duplicate entries found */
1524 #endif
1525
1526 /* search an unused entry, or the oldest one */
1527 lseq = 0;
1528 lseqi = DNS_TABLE_SIZE;
1529 for (i = 0; i < DNS_TABLE_SIZE; ++i) {
1530 entry = &dns_table[i];
1531 /* is it an unused entry ? */
1532 if (entry->state == DNS_STATE_UNUSED) {
1533 break;
1534 }
1535 /* check if this is the oldest completed entry */
1536 if (entry->state == DNS_STATE_DONE) {
1537 u8_t age = (u8_t)(dns_seqno - entry->seqno);
1538 if (age > lseq) {
1539 lseq = age;
1540 lseqi = i;
1541 }
1542 }
1543 }
1544
1545 /* if we don't have found an unused entry, use the oldest completed one */
1546 if (i == DNS_TABLE_SIZE) {
1547 if ((lseqi >= DNS_TABLE_SIZE) || (dns_table[lseqi].state != DNS_STATE_DONE)) {
1548 /* no entry can be used now, table is full */
1549 LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS entries table is full\n", name));
1550 return ERR_MEM;
1551 } else {
1552 /* use the oldest completed one */
1553 i = lseqi;
1554 entry = &dns_table[i];
1555 }
1556 }
1557
1558 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
1559 /* find a free request entry */
1560 req = NULL;
1561 for (r = 0; r < DNS_MAX_REQUESTS; r++) {
1562 if (dns_requests[r].found == NULL) {
1563 req = &dns_requests[r];
1564 break;
1565 }
1566 }
1567 if (req == NULL) {
1568 /* no request entry can be used now, table is full */
1569 LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS request entries table is full\n", name));
1570 return ERR_MEM;
1571 }
1572 req->dns_table_idx = i;
1573 #else
1574 /* in this configuration, the entry index is the same as the request index */
1575 req = &dns_requests[i];
1576 #endif
1577
1578 /* use this entry */
1579 LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS entry %"U16_F"\n", name, (u16_t)(i)));
1580
1581 /* fill the entry */
1582 entry->state = DNS_STATE_NEW;
1583 entry->seqno = dns_seqno;
1584 LWIP_DNS_SET_ADDRTYPE(entry->reqaddrtype, dns_addrtype);
1585 LWIP_DNS_SET_ADDRTYPE(req->reqaddrtype, dns_addrtype);
1586 req->found = found;
1587 req->arg = callback_arg;
1588 namelen = LWIP_MIN(hostnamelen, DNS_MAX_NAME_LENGTH - 1);
1589 MEMCPY(entry->name, name, namelen);
1590 entry->name[namelen] = 0;
1591
1592 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
1593 entry->pcb_idx = dns_alloc_pcb();
1594 if (entry->pcb_idx >= DNS_MAX_SOURCE_PORTS) {
1595 /* failed to get a UDP pcb */
1596 LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": failed to allocate a pcb\n", name));
1597 entry->state = DNS_STATE_UNUSED;
1598 req->found = NULL;
1599 return ERR_MEM;
1600 }
1601 LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS pcb %"U16_F"\n", name, (u16_t)(entry->pcb_idx)));
1602 #endif
1603
1604 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
1605 entry->is_mdns = is_mdns;
1606 #endif
1607
1608 dns_seqno++;
1609
1610 /* force to send query without waiting timer */
1611 dns_check_entry(i);
1612
1613 /* dns query is enqueued */
1614 return ERR_INPROGRESS;
1615 }
1616
1617 /**
1618 * @ingroup dns
1619 * Resolve a hostname (string) into an IP address.
1620 * NON-BLOCKING callback version for use with raw API!!!
1621 *
1622 * Returns immediately with one of err_t return codes:
1623 * - ERR_OK if hostname is a valid IP address string or the host
1624 * name is already in the local names table.
1625 * - ERR_INPROGRESS enqueue a request to be sent to the DNS server
1626 * for resolution if no errors are present.
1627 * - ERR_ARG: dns client not initialized or invalid hostname
1628 *
1629 * @param hostname the hostname that is to be queried
1630 * @param addr pointer to a ip_addr_t where to store the address if it is already
1631 * cached in the dns_table (only valid if ERR_OK is returned!)
1632 * @param found a callback function to be called on success, failure or timeout (only if
1633 * ERR_INPROGRESS is returned!)
1634 * @param callback_arg argument to pass to the callback function
1635 * @return a err_t return code.
1636 */
1637 err_t
dns_gethostbyname(const char * hostname,ip_addr_t * addr,dns_found_callback found,void * callback_arg)1638 dns_gethostbyname(const char *hostname, ip_addr_t *addr, dns_found_callback found,
1639 void *callback_arg)
1640 {
1641 return dns_gethostbyname_addrtype(hostname, addr, found, callback_arg, LWIP_DNS_ADDRTYPE_DEFAULT);
1642 }
1643
1644 /**
1645 * @ingroup dns
1646 * Like dns_gethostbyname, but returned address type can be controlled:
1647 * @param hostname the hostname that is to be queried
1648 * @param addr pointer to a ip_addr_t where to store the address if it is already
1649 * cached in the dns_table (only valid if ERR_OK is returned!)
1650 * @param found a callback function to be called on success, failure or timeout (only if
1651 * ERR_INPROGRESS is returned!)
1652 * @param callback_arg argument to pass to the callback function
1653 * @param dns_addrtype - LWIP_DNS_ADDRTYPE_IPV4_IPV6: try to resolve IPv4 first, try IPv6 if IPv4 fails only
1654 * - LWIP_DNS_ADDRTYPE_IPV6_IPV4: try to resolve IPv6 first, try IPv4 if IPv6 fails only
1655 * - LWIP_DNS_ADDRTYPE_IPV4: try to resolve IPv4 only
1656 * - LWIP_DNS_ADDRTYPE_IPV6: try to resolve IPv6 only
1657 */
1658 err_t
dns_gethostbyname_addrtype(const char * hostname,ip_addr_t * addr,dns_found_callback found,void * callback_arg,u8_t dns_addrtype)1659 dns_gethostbyname_addrtype(const char *hostname, ip_addr_t *addr, dns_found_callback found,
1660 void *callback_arg, u8_t dns_addrtype)
1661 {
1662 size_t hostnamelen;
1663 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
1664 u8_t is_mdns;
1665 #endif
1666 /* not initialized or no valid server yet, or invalid addr pointer
1667 * or invalid hostname or invalid hostname length */
1668 if ((addr == NULL) ||
1669 (!hostname) || (!hostname[0])) {
1670 return ERR_ARG;
1671 }
1672 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) == 0)
1673 if (dns_pcbs[0] == NULL) {
1674 return ERR_ARG;
1675 }
1676 #endif
1677 hostnamelen = strlen(hostname);
1678 if (hostnamelen >= DNS_MAX_NAME_LENGTH) {
1679 LWIP_DEBUGF(DNS_DEBUG, ("dns_gethostbyname: name too long to resolve"));
1680 return ERR_ARG;
1681 }
1682
1683
1684 #if LWIP_HAVE_LOOPIF
1685 if (strcmp(hostname, "localhost") == 0) {
1686 ip_addr_set_loopback(LWIP_DNS_ADDRTYPE_IS_IPV6(dns_addrtype), addr);
1687 return ERR_OK;
1688 }
1689 #endif /* LWIP_HAVE_LOOPIF */
1690
1691 /* host name already in octet notation? set ip addr and return ERR_OK */
1692 if (ipaddr_aton(hostname, addr)) {
1693 #if LWIP_IPV4 && LWIP_IPV6
1694 if ((IP_IS_V6(addr) && (dns_addrtype != LWIP_DNS_ADDRTYPE_IPV4)) ||
1695 (IP_IS_V4(addr) && (dns_addrtype != LWIP_DNS_ADDRTYPE_IPV6)))
1696 #endif /* LWIP_IPV4 && LWIP_IPV6 */
1697 {
1698 return ERR_OK;
1699 }
1700 }
1701 /* already have this address cached? */
1702 if (dns_lookup(hostname, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)) == ERR_OK) {
1703 return ERR_OK;
1704 }
1705 #if LWIP_IPV4 && LWIP_IPV6
1706 if ((dns_addrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) || (dns_addrtype == LWIP_DNS_ADDRTYPE_IPV6_IPV4)) {
1707 /* fallback to 2nd IP type and try again to lookup */
1708 u8_t fallback;
1709 if (dns_addrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) {
1710 fallback = LWIP_DNS_ADDRTYPE_IPV6;
1711 } else {
1712 fallback = LWIP_DNS_ADDRTYPE_IPV4;
1713 }
1714 if (dns_lookup(hostname, addr LWIP_DNS_ADDRTYPE_ARG(fallback)) == ERR_OK) {
1715 return ERR_OK;
1716 }
1717 }
1718 #else /* LWIP_IPV4 && LWIP_IPV6 */
1719 LWIP_UNUSED_ARG(dns_addrtype);
1720 #endif /* LWIP_IPV4 && LWIP_IPV6 */
1721
1722 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
1723 if (strstr(hostname, ".local") == &hostname[hostnamelen] - 6) {
1724 is_mdns = 1;
1725 } else {
1726 is_mdns = 0;
1727 }
1728
1729 if (!is_mdns)
1730 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
1731 {
1732 /* prevent calling found callback if no server is set, return error instead */
1733 if (ip_addr_isany_val(dns_servers[0])) {
1734 return ERR_VAL;
1735 }
1736 }
1737
1738 /* queue query with specified callback */
1739 return dns_enqueue(hostname, hostnamelen, found, callback_arg LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)
1740 LWIP_DNS_ISMDNS_ARG(is_mdns));
1741 }
1742
1743 #endif /* LWIP_DNS */
1744