A version of LWIP, provided for backwards compatibility.
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dns.c
00001 /** 00002 * @file 00003 * DNS - host name to IP address resolver. 00004 * 00005 */ 00006 00007 /** 00008 00009 * This file implements a DNS host name to IP address resolver. 00010 00011 * Port to lwIP from uIP 00012 * by Jim Pettinato April 2007 00013 00014 * uIP version Copyright (c) 2002-2003, Adam Dunkels. 00015 * All rights reserved. 00016 * 00017 * Redistribution and use in source and binary forms, with or without 00018 * modification, are permitted provided that the following conditions 00019 * are met: 00020 * 1. Redistributions of source code must retain the above copyright 00021 * notice, this list of conditions and the following disclaimer. 00022 * 2. Redistributions in binary form must reproduce the above copyright 00023 * notice, this list of conditions and the following disclaimer in the 00024 * documentation and/or other materials provided with the distribution. 00025 * 3. The name of the author may not be used to endorse or promote 00026 * products derived from this software without specific prior 00027 * written permission. 00028 * 00029 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS 00030 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 00031 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 00032 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY 00033 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 00034 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE 00035 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 00036 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 00037 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 00038 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 00039 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 00040 * 00041 * 00042 * DNS.C 00043 * 00044 * The lwIP DNS resolver functions are used to lookup a host name and 00045 * map it to a numerical IP address. It maintains a list of resolved 00046 * hostnames that can be queried with the dns_lookup() function. 00047 * New hostnames can be resolved using the dns_query() function. 00048 * 00049 * The lwIP version of the resolver also adds a non-blocking version of 00050 * gethostbyname() that will work with a raw API application. This function 00051 * checks for an IP address string first and converts it if it is valid. 00052 * gethostbyname() then does a dns_lookup() to see if the name is 00053 * already in the table. If so, the IP is returned. If not, a query is 00054 * issued and the function returns with a ERR_INPROGRESS status. The app 00055 * using the dns client must then go into a waiting state. 00056 * 00057 * Once a hostname has been resolved (or found to be non-existent), 00058 * the resolver code calls a specified callback function (which 00059 * must be implemented by the module that uses the resolver). 00060 */ 00061 00062 /*----------------------------------------------------------------------------- 00063 * RFC 1035 - Domain names - implementation and specification 00064 * RFC 2181 - Clarifications to the DNS Specification 00065 *----------------------------------------------------------------------------*/ 00066 00067 /** @todo: define good default values (rfc compliance) */ 00068 /** @todo: improve answer parsing, more checkings... */ 00069 /** @todo: check RFC1035 - 7.3. Processing responses */ 00070 00071 /*----------------------------------------------------------------------------- 00072 * Includes 00073 *----------------------------------------------------------------------------*/ 00074 00075 #include "lwip/opt.h" 00076 00077 #if LWIP_DNS /* don't build if not configured for use in lwipopts.h */ 00078 00079 #include "lwip/udp.h" 00080 #include "lwip/mem.h" 00081 #include "lwip/dns.h" 00082 00083 #include <string.h> 00084 00085 /** DNS server IP address */ 00086 #ifndef DNS_SERVER_ADDRESS 00087 #define DNS_SERVER_ADDRESS inet_addr("208.67.222.222") /* resolver1.opendns.com */ 00088 #endif 00089 00090 /** DNS server port address */ 00091 #ifndef DNS_SERVER_PORT 00092 #define DNS_SERVER_PORT 53 00093 #endif 00094 00095 /** DNS maximum number of retries when asking for a name, before "timeout". */ 00096 #ifndef DNS_MAX_RETRIES 00097 #define DNS_MAX_RETRIES 4 00098 #endif 00099 00100 /** DNS resource record max. TTL (one week as default) */ 00101 #ifndef DNS_MAX_TTL 00102 #define DNS_MAX_TTL 604800 00103 #endif 00104 00105 /* DNS protocol flags */ 00106 #define DNS_FLAG1_RESPONSE 0x80 00107 #define DNS_FLAG1_OPCODE_STATUS 0x10 00108 #define DNS_FLAG1_OPCODE_INVERSE 0x08 00109 #define DNS_FLAG1_OPCODE_STANDARD 0x00 00110 #define DNS_FLAG1_AUTHORATIVE 0x04 00111 #define DNS_FLAG1_TRUNC 0x02 00112 #define DNS_FLAG1_RD 0x01 00113 #define DNS_FLAG2_RA 0x80 00114 #define DNS_FLAG2_ERR_MASK 0x0f 00115 #define DNS_FLAG2_ERR_NONE 0x00 00116 #define DNS_FLAG2_ERR_NAME 0x03 00117 00118 /* DNS protocol states */ 00119 #define DNS_STATE_UNUSED 0 00120 #define DNS_STATE_NEW 1 00121 #define DNS_STATE_ASKING 2 00122 #define DNS_STATE_DONE 3 00123 00124 00125 // XXX: For C++ compatibility 00126 #define class mclass 00127 00128 #ifdef PACK_STRUCT_USE_INCLUDES 00129 # include "arch/bpstruct.h" 00130 #endif 00131 PACK_STRUCT_BEGIN 00132 /** DNS message header */ 00133 struct dns_hdr { 00134 u16_t id; 00135 u8_t flags1; 00136 u8_t flags2; 00137 u16_t numquestions; 00138 u16_t numanswers; 00139 u16_t numauthrr; 00140 u16_t numextrarr; 00141 } PACK_STRUCT_STRUCT; 00142 PACK_STRUCT_END 00143 #ifdef PACK_STRUCT_USE_INCLUDES 00144 # include "arch/epstruct.h" 00145 #endif 00146 #define SIZEOF_DNS_HDR 12 00147 00148 #ifdef PACK_STRUCT_USE_INCLUDES 00149 # include "arch/bpstruct.h" 00150 #endif 00151 PACK_STRUCT_BEGIN 00152 /** DNS query message structure */ 00153 struct dns_query { 00154 /* DNS query record starts with either a domain name or a pointer 00155 to a name already present somewhere in the packet. */ 00156 u16_t type; 00157 u16_t class; 00158 } PACK_STRUCT_STRUCT; 00159 PACK_STRUCT_END 00160 #ifdef PACK_STRUCT_USE_INCLUDES 00161 # include "arch/epstruct.h" 00162 #endif 00163 #define SIZEOF_DNS_QUERY 4 00164 00165 #ifdef PACK_STRUCT_USE_INCLUDES 00166 # include "arch/bpstruct.h" 00167 #endif 00168 PACK_STRUCT_BEGIN 00169 /** DNS answer message structure */ 00170 struct dns_answer { 00171 /* DNS answer record starts with either a domain name or a pointer 00172 to a name already present somewhere in the packet. */ 00173 u16_t type; 00174 u16_t class; 00175 u32_t ttl; 00176 u16_t len; 00177 } PACK_STRUCT_STRUCT; 00178 PACK_STRUCT_END 00179 #ifdef PACK_STRUCT_USE_INCLUDES 00180 # include "arch/epstruct.h" 00181 #endif 00182 #define SIZEOF_DNS_ANSWER 10 00183 00184 /** DNS table entry */ 00185 struct dns_table_entry { 00186 u8_t state; 00187 u8_t numdns; 00188 u8_t tmr; 00189 u8_t retries; 00190 u8_t seqno; 00191 u8_t err; 00192 u32_t ttl; 00193 char name[DNS_MAX_NAME_LENGTH]; 00194 struct ip_addr ipaddr; 00195 /* pointer to callback on DNS query done */ 00196 dns_found_callback found; 00197 void *arg; 00198 }; 00199 00200 #if DNS_LOCAL_HOSTLIST 00201 /** struct used for local host-list */ 00202 struct local_hostlist_entry { 00203 /** static hostname */ 00204 const char *name; 00205 /** static host address in network byteorder */ 00206 u32_t addr; 00207 struct local_hostlist_entry *next; 00208 }; 00209 00210 #if !DNS_LOCAL_HOSTLIST_IS_DYNAMIC 00211 static struct local_hostlist_entry local_hostlist_static[] = DNS_LOCAL_HOSTLIST_INIT MEM_POSITION; 00212 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ 00213 00214 /** Local host-list. For hostnames in this list, no 00215 * external name resolution is performed */ 00216 static struct local_hostlist_entry *local_hostlist; 00217 00218 static void dns_init_local(); 00219 #endif /* DNS_LOCAL_HOSTLIST */ 00220 00221 00222 /* forward declarations */ 00223 static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port); 00224 static void dns_check_entries(void); 00225 00226 /*----------------------------------------------------------------------------- 00227 * Globales 00228 *----------------------------------------------------------------------------*/ 00229 00230 /* DNS variables */ 00231 static struct udp_pcb *dns_pcb; 00232 static u8_t dns_seqno; 00233 static struct dns_table_entry dns_table[DNS_TABLE_SIZE] MEM_POSITION; 00234 static struct ip_addr dns_servers[DNS_MAX_SERVERS] MEM_POSITION; 00235 00236 #if (DNS_USES_STATIC_BUF == 1) 00237 static u8_t dns_payload[DNS_MSG_SIZE] MEM_POSITION; 00238 #endif /* (DNS_USES_STATIC_BUF == 1) */ 00239 00240 /** 00241 * Initialize the resolver: set up the UDP pcb and configure the default server 00242 * (DNS_SERVER_ADDRESS). 00243 */ 00244 void 00245 dns_init() 00246 { 00247 struct ip_addr dnsserver; 00248 00249 /* initialize default DNS server address */ 00250 dnsserver.addr = DNS_SERVER_ADDRESS; 00251 00252 LWIP_DEBUGF(DNS_DEBUG, ("dns_init: initializing\n")); 00253 00254 /* if dns client not yet initialized... */ 00255 if (dns_pcb == NULL) { 00256 dns_pcb = udp_new(); 00257 00258 if (dns_pcb != NULL) { 00259 /* initialize DNS table not needed (initialized to zero since it is a 00260 * global variable) */ 00261 LWIP_ASSERT("For implicit initialization to work, DNS_STATE_UNUSED needs to be 0", 00262 DNS_STATE_UNUSED == 0); 00263 00264 /* initialize DNS client */ 00265 udp_bind(dns_pcb, IP_ADDR_ANY, 0); 00266 udp_recv(dns_pcb, dns_recv, NULL); 00267 00268 /* initialize default DNS primary server */ 00269 dns_setserver(0, &dnsserver); 00270 } 00271 } 00272 #if DNS_LOCAL_HOSTLIST 00273 dns_init_local(); 00274 #endif 00275 } 00276 00277 /** 00278 * Initialize one of the DNS servers. 00279 * 00280 * @param numdns the index of the DNS server to set must be < DNS_MAX_SERVERS 00281 * @param dnsserver IP address of the DNS server to set 00282 */ 00283 void 00284 dns_setserver(u8_t numdns, struct ip_addr *dnsserver) 00285 { 00286 if ((numdns < DNS_MAX_SERVERS) && (dns_pcb != NULL) && 00287 (dnsserver != NULL) && (dnsserver->addr !=0 )) { 00288 dns_servers[numdns] = (*dnsserver); 00289 } 00290 } 00291 00292 /** 00293 * Obtain one of the currently configured DNS server. 00294 * 00295 * @param numdns the index of the DNS server 00296 * @return IP address of the indexed DNS server or "ip_addr_any" if the DNS 00297 * server has not been configured. 00298 */ 00299 struct ip_addr 00300 dns_getserver(u8_t numdns) 00301 { 00302 if (numdns < DNS_MAX_SERVERS) { 00303 return dns_servers[numdns]; 00304 } else { 00305 return *IP_ADDR_ANY; 00306 } 00307 } 00308 00309 /** 00310 * The DNS resolver client timer - handle retries and timeouts and should 00311 * be called every DNS_TMR_INTERVAL milliseconds (every second by default). 00312 */ 00313 void 00314 dns_tmr(void) 00315 { 00316 if (dns_pcb != NULL) { 00317 LWIP_DEBUGF(DNS_DEBUG, ("dns_tmr: dns_check_entries\n")); 00318 dns_check_entries(); 00319 } 00320 } 00321 00322 #if DNS_LOCAL_HOSTLIST 00323 static void 00324 dns_init_local() 00325 { 00326 #ifdef DNS_LOCAL_HOSTLIST_INIT 00327 int i; 00328 struct local_hostlist_entry *entry; 00329 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC 00330 /* Dynamic: copy entries from DNS_LOCAL_HOSTLIST_INIT to list */ 00331 struct local_hostlist_entry local_hostlist_init[] = DNS_LOCAL_HOSTLIST_INIT; 00332 for (i = 0; i < sizeof(local_hostlist_init) / sizeof(struct local_hostlist_entry); i++) { 00333 entry = mem_malloc(sizeof(struct local_hostlist_entry)); 00334 LWIP_ASSERT("mem-error in dns_init_local", entry != NULL); 00335 if (entry != NULL) { 00336 struct local_hostlist_entry *init_entry = &local_hostlist_init[i]; 00337 entry->name = init_entry->name; 00338 entry->addr = init_entry->addr; 00339 entry->next = local_hostlist; 00340 local_hostlist = entry; 00341 } 00342 } 00343 #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ 00344 /* Static: only adjust the 'next' pointers */ 00345 entry = NULL; 00346 local_hostlist = local_hostlist_static; 00347 for (i = sizeof(local_hostlist_static) / sizeof(struct local_hostlist_entry) - 1; i >= 0; i--) { 00348 local_hostlist_static[i].next = entry; 00349 entry = &local_hostlist_static[i]; 00350 } 00351 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ 00352 #endif /* DNS_LOCAL_HOSTLIST_INIT */ 00353 } 00354 00355 static u32_t 00356 dns_lookup_static(const char *name) 00357 { 00358 struct local_hostlist_entry *entry = local_hostlist; 00359 while(entry != NULL) { 00360 if(strcmp(entry->name, name) == 0) { 00361 return htons(entry->addr); 00362 } 00363 entry = entry->next; 00364 } 00365 return INADDR_NONE; 00366 } 00367 00368 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC 00369 /** Remove all entries from the local host-list for a specific hostname 00370 * 00371 * @param hostname hostname for which entries shall be removed from the local 00372 * host-list 00373 * @return the number of removed entries 00374 */ 00375 int 00376 dns_local_removehostname(const char *hostname) 00377 { 00378 int removed = 0; 00379 struct local_hostlist_entry *entry = local_hostlist; 00380 struct local_hostlist_entry *last_entry = NULL; 00381 while (entry != NULL) { 00382 if (!strcmp(entry->name, hostname)) { 00383 if (last_entry != NULL) { 00384 last_entry->next = entry->next; 00385 } else { 00386 local_hostlist = entry->next; 00387 } 00388 mem_free(entry); 00389 removed++; 00390 } 00391 last_entry = entry; 00392 entry = entry->next; 00393 } 00394 return removed; 00395 } 00396 00397 /** Remove all entries from the local host-list for a specific address 00398 * 00399 * @param addr address for which entries shall be removed from the local 00400 * host-list 00401 * @return the number of removed entries 00402 */ 00403 int 00404 dns_local_removehostaddr(const struct ip_addr *addr) 00405 { 00406 int removed = 0; 00407 struct local_hostlist_entry *entry = local_hostlist; 00408 struct local_hostlist_entry *last_entry = NULL; 00409 while (entry != NULL) { 00410 if (entry->addr == addr->addr) { 00411 struct local_hostlist_entry *removed_entry = entry; 00412 if (last_entry != NULL) { 00413 last_entry->next = entry->next; 00414 } else { 00415 local_hostlist = entry->next; 00416 } 00417 entry = entry->next; 00418 mem_free(removed_entry); 00419 removed++; 00420 } else { 00421 last_entry = entry; 00422 entry = entry->next; 00423 } 00424 } 00425 return removed; 00426 } 00427 00428 err_t 00429 dns_local_addhost(const char *hostname, const struct ip_addr *addr) 00430 { 00431 struct local_hostlist_entry *entry; 00432 entry = mem_malloc(sizeof(struct local_hostlist_entry)); 00433 if (entry == NULL) { 00434 return ERR_MEM; 00435 } 00436 entry->name = hostname; 00437 entry->addr = addr->addr; 00438 entry->next = local_hostlist; 00439 local_hostlist = entry; 00440 return ERR_OK; 00441 } 00442 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC*/ 00443 #endif /* DNS_LOCAL_HOSTLIST */ 00444 00445 /** 00446 * Look up a hostname in the array of known hostnames. 00447 * 00448 * @note This function only looks in the internal array of known 00449 * hostnames, it does not send out a query for the hostname if none 00450 * was found. The function dns_enqueue() can be used to send a query 00451 * for a hostname. 00452 * 00453 * @param name the hostname to look up 00454 * @return the hostname's IP address, as u32_t (instead of struct ip_addr to 00455 * better check for failure: != INADDR_NONE) or INADDR_NONE if the hostname 00456 * was not found in the cached dns_table. 00457 */ 00458 static u32_t 00459 dns_lookup(const char *name) 00460 { 00461 u8_t i; 00462 #if DNS_LOCAL_HOSTLIST 00463 u32_t addr; 00464 00465 if ((addr = dns_lookup_static(name)) != INADDR_NONE) { 00466 return addr; 00467 } 00468 #endif /* DNS_LOCAL_HOSTLIST */ 00469 00470 /* Walk through name list, return entry if found. If not, return NULL. */ 00471 for (i = 0; i < DNS_TABLE_SIZE; ++i) { 00472 if ((dns_table[i].state == DNS_STATE_DONE) && 00473 (strcmp(name, dns_table[i].name) == 0)) { 00474 LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name)); 00475 ip_addr_debug_print(DNS_DEBUG, &(dns_table[i].ipaddr)); 00476 LWIP_DEBUGF(DNS_DEBUG, ("\n")); 00477 return dns_table[i].ipaddr.addr; 00478 } 00479 } 00480 00481 return INADDR_NONE; 00482 } 00483 00484 #if DNS_DOES_NAME_CHECK 00485 /** 00486 * Compare the "dotted" name "query" with the encoded name "response" 00487 * to make sure an answer from the DNS server matches the current dns_table 00488 * entry (otherwise, answers might arrive late for hostname not on the list 00489 * any more). 00490 * 00491 * @param query hostname (not encoded) from the dns_table 00492 * @param response encoded hostname in the DNS response 00493 * @return 0: names equal; 1: names differ 00494 */ 00495 static u8_t 00496 dns_compare_name(unsigned char *query, unsigned char *response) 00497 { 00498 unsigned char n; 00499 00500 do { 00501 n = *response++; 00502 /** @see RFC 1035 - 4.1.4. Message compression */ 00503 if ((n & 0xc0) == 0xc0) { 00504 /* Compressed name */ 00505 break; 00506 } else { 00507 /* Not compressed name */ 00508 while (n > 0) { 00509 if ((*query) != (*response)) { 00510 return 1; 00511 } 00512 ++response; 00513 ++query; 00514 --n; 00515 }; 00516 ++query; 00517 } 00518 } while (*response != 0); 00519 00520 return 0; 00521 } 00522 #endif /* DNS_DOES_NAME_CHECK */ 00523 00524 /** 00525 * Walk through a compact encoded DNS name and return the end of the name. 00526 * 00527 * @param query encoded DNS name in the DNS server response 00528 * @return end of the name 00529 */ 00530 static unsigned char * 00531 dns_parse_name(unsigned char *query) 00532 { 00533 unsigned char n; 00534 00535 do { 00536 n = *query++; 00537 /** @see RFC 1035 - 4.1.4. Message compression */ 00538 if ((n & 0xc0) == 0xc0) { 00539 /* Compressed name */ 00540 break; 00541 } else { 00542 /* Not compressed name */ 00543 while (n > 0) { 00544 ++query; 00545 --n; 00546 }; 00547 } 00548 } while (*query != 0); 00549 00550 return query + 1; 00551 } 00552 00553 /** 00554 * Send a DNS query packet. 00555 * 00556 * @param numdns index of the DNS server in the dns_servers table 00557 * @param name hostname to query 00558 * @param id index of the hostname in dns_table, used as transaction ID in the 00559 * DNS query packet 00560 * @return ERR_OK if packet is sent; an err_t indicating the problem otherwise 00561 */ 00562 static err_t 00563 dns_send(u8_t numdns, const char* name, u8_t id) 00564 { 00565 err_t err; 00566 struct dns_hdr *hdr; 00567 struct dns_query qry; 00568 struct pbuf *p; 00569 char *query, *nptr; 00570 const char *pHostname; 00571 u8_t n; 00572 00573 LWIP_DEBUGF(DNS_DEBUG, ("dns_send: dns_servers[%"U16_F"] \"%s\": request\n", 00574 (u16_t)(numdns), name)); 00575 LWIP_ASSERT("dns server out of array", numdns < DNS_MAX_SERVERS); 00576 LWIP_ASSERT("dns server has no IP address set", dns_servers[numdns].addr != 0); 00577 00578 /* if here, we have either a new query or a retry on a previous query to process */ 00579 p = pbuf_alloc(PBUF_TRANSPORT, SIZEOF_DNS_HDR + DNS_MAX_NAME_LENGTH + 00580 SIZEOF_DNS_QUERY, PBUF_RAM); 00581 if (p != NULL) { 00582 LWIP_ASSERT("pbuf must be in one piece", p->next == NULL); 00583 /* fill dns header */ 00584 hdr = (struct dns_hdr*)p->payload; 00585 memset(hdr, 0, SIZEOF_DNS_HDR); 00586 hdr->id = htons(id); 00587 hdr->flags1 = DNS_FLAG1_RD; 00588 hdr->numquestions = htons(1); 00589 query = (char*)hdr + SIZEOF_DNS_HDR; 00590 pHostname = name; 00591 --pHostname; 00592 00593 /* convert hostname into suitable query format. */ 00594 do { 00595 ++pHostname; 00596 nptr = query; 00597 ++query; 00598 for(n = 0; *pHostname != '.' && *pHostname != 0; ++pHostname) { 00599 *query = *pHostname; 00600 ++query; 00601 ++n; 00602 } 00603 *nptr = n; 00604 } while(*pHostname != 0); 00605 *query++='\0'; 00606 00607 /* fill dns query */ 00608 qry.type = htons(DNS_RRTYPE_A); 00609 qry.class = htons(DNS_RRCLASS_IN); 00610 MEMCPY( query, &qry, SIZEOF_DNS_QUERY); 00611 00612 /* resize pbuf to the exact dns query */ 00613 pbuf_realloc(p, (query + SIZEOF_DNS_QUERY) - ((char*)(p->payload))); 00614 00615 /* connect to the server for faster receiving */ 00616 udp_connect(dns_pcb, &dns_servers[numdns], DNS_SERVER_PORT); 00617 /* send dns packet */ 00618 err = udp_sendto(dns_pcb, p, &dns_servers[numdns], DNS_SERVER_PORT); 00619 00620 /* free pbuf */ 00621 pbuf_free(p); 00622 } else { 00623 err = ERR_MEM; 00624 } 00625 00626 return err; 00627 } 00628 00629 /** 00630 * dns_check_entry() - see if pEntry has not yet been queried and, if so, sends out a query. 00631 * Check an entry in the dns_table: 00632 * - send out query for new entries 00633 * - retry old pending entries on timeout (also with different servers) 00634 * - remove completed entries from the table if their TTL has expired 00635 * 00636 * @param i index of the dns_table entry to check 00637 */ 00638 static void 00639 dns_check_entry(u8_t i) 00640 { 00641 struct dns_table_entry *pEntry = &dns_table[i]; 00642 00643 LWIP_ASSERT("array index out of bounds", i < DNS_TABLE_SIZE); 00644 00645 switch(pEntry->state) { 00646 00647 case DNS_STATE_NEW: { 00648 /* initialize new entry */ 00649 pEntry->state = DNS_STATE_ASKING; 00650 pEntry->numdns = 0; 00651 pEntry->tmr = 1; 00652 pEntry->retries = 0; 00653 00654 /* send DNS packet for this entry */ 00655 dns_send(pEntry->numdns, pEntry->name, i); 00656 break; 00657 } 00658 00659 case DNS_STATE_ASKING: { 00660 if (--pEntry->tmr == 0) { 00661 if (++pEntry->retries == DNS_MAX_RETRIES) { 00662 if ((pEntry->numdns+1<DNS_MAX_SERVERS) && (dns_servers[pEntry->numdns+1].addr!=0)) { 00663 /* change of server */ 00664 pEntry->numdns++; 00665 pEntry->tmr = 1; 00666 pEntry->retries = 0; 00667 break; 00668 } else { 00669 LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": timeout\n", pEntry->name)); 00670 /* call specified callback function if provided */ 00671 if (pEntry->found) 00672 (*pEntry->found)(pEntry->name, NULL, pEntry->arg); 00673 /* flush this entry */ 00674 pEntry->state = DNS_STATE_UNUSED; 00675 pEntry->found = NULL; 00676 break; 00677 } 00678 } 00679 00680 /* wait longer for the next retry */ 00681 pEntry->tmr = pEntry->retries; 00682 00683 /* send DNS packet for this entry */ 00684 dns_send(pEntry->numdns, pEntry->name, i); 00685 } 00686 break; 00687 } 00688 00689 case DNS_STATE_DONE: { 00690 /* if the time to live is nul */ 00691 if (--pEntry->ttl == 0) { 00692 LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": flush\n", pEntry->name)); 00693 /* flush this entry */ 00694 pEntry->state = DNS_STATE_UNUSED; 00695 pEntry->found = NULL; 00696 } 00697 break; 00698 } 00699 case DNS_STATE_UNUSED: 00700 /* nothing to do */ 00701 break; 00702 default: 00703 LWIP_ASSERT("unknown dns_table entry state:", 0); 00704 break; 00705 } 00706 } 00707 00708 /** 00709 * Call dns_check_entry for each entry in dns_table - check all entries. 00710 */ 00711 static void 00712 dns_check_entries(void) 00713 { 00714 u8_t i; 00715 00716 for (i = 0; i < DNS_TABLE_SIZE; ++i) { 00717 dns_check_entry(i); 00718 } 00719 } 00720 00721 /** 00722 * Receive input function for DNS response packets arriving for the dns UDP pcb. 00723 * 00724 * @params see udp.h 00725 */ 00726 static void 00727 dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, struct ip_addr *addr, u16_t port) 00728 { 00729 u8_t i; 00730 char *pHostname; 00731 struct dns_hdr *hdr; 00732 struct dns_answer ans; 00733 struct dns_table_entry *pEntry; 00734 u8_t nquestions, nanswers; 00735 #if (DNS_USES_STATIC_BUF == 0) 00736 u8_t dns_payload[DNS_MSG_SIZE]; 00737 #endif /* (DNS_USES_STATIC_BUF == 0) */ 00738 #if (DNS_USES_STATIC_BUF == 2) 00739 u8_t* dns_payload; 00740 #endif /* (DNS_USES_STATIC_BUF == 2) */ 00741 00742 LWIP_UNUSED_ARG(arg); 00743 LWIP_UNUSED_ARG(pcb); 00744 LWIP_UNUSED_ARG(addr); 00745 LWIP_UNUSED_ARG(port); 00746 00747 /* is the dns message too big ? */ 00748 if (p->tot_len > DNS_MSG_SIZE) { 00749 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too big\n")); 00750 /* free pbuf and return */ 00751 goto memerr1; 00752 } 00753 00754 /* is the dns message big enough ? */ 00755 if (p->tot_len < (SIZEOF_DNS_HDR + SIZEOF_DNS_QUERY + SIZEOF_DNS_ANSWER)) { 00756 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too small\n")); 00757 /* free pbuf and return */ 00758 goto memerr1; 00759 } 00760 00761 #if (DNS_USES_STATIC_BUF == 2) 00762 dns_payload = mem_malloc(p->tot_len); 00763 if (dns_payload == NULL) { 00764 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: mem_malloc error\n")); 00765 /* free pbuf and return */ 00766 goto memerr1; 00767 } 00768 #endif /* (DNS_USES_STATIC_BUF == 2) */ 00769 00770 /* copy dns payload inside static buffer for processing */ 00771 if (pbuf_copy_partial(p, dns_payload, p->tot_len, 0) == p->tot_len) { 00772 /* The ID in the DNS header should be our entry into the name table. */ 00773 hdr = (struct dns_hdr*)dns_payload; 00774 i = htons(hdr->id); 00775 if (i < DNS_TABLE_SIZE) { 00776 pEntry = &dns_table[i]; 00777 if(pEntry->state == DNS_STATE_ASKING) { 00778 /* This entry is now completed. */ 00779 pEntry->state = DNS_STATE_DONE; 00780 pEntry->err = hdr->flags2 & DNS_FLAG2_ERR_MASK; 00781 00782 /* We only care about the question(s) and the answers. The authrr 00783 and the extrarr are simply discarded. */ 00784 nquestions = htons(hdr->numquestions); 00785 nanswers = htons(hdr->numanswers); 00786 00787 /* Check for error. If so, call callback to inform. */ 00788 if (((hdr->flags1 & DNS_FLAG1_RESPONSE) == 0) || (pEntry->err != 0) || (nquestions != 1)) { 00789 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", pEntry->name)); 00790 /* call callback to indicate error, clean up memory and return */ 00791 goto responseerr; 00792 } 00793 00794 #if DNS_DOES_NAME_CHECK 00795 /* Check if the name in the "question" part match with the name in the entry. */ 00796 if (dns_compare_name((unsigned char *)(pEntry->name), (unsigned char *)dns_payload + SIZEOF_DNS_HDR) != 0) { 00797 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", pEntry->name)); 00798 /* call callback to indicate error, clean up memory and return */ 00799 goto responseerr; 00800 } 00801 #endif /* DNS_DOES_NAME_CHECK */ 00802 00803 /* Skip the name in the "question" part */ 00804 pHostname = (char *) dns_parse_name((unsigned char *)dns_payload + SIZEOF_DNS_HDR) + SIZEOF_DNS_QUERY; 00805 00806 while(nanswers > 0) { 00807 /* skip answer resource record's host name */ 00808 pHostname = (char *) dns_parse_name((unsigned char *)pHostname); 00809 00810 /* Check for IP address type and Internet class. Others are discarded. */ 00811 MEMCPY(&ans, pHostname, SIZEOF_DNS_ANSWER); 00812 if((ntohs(ans.type) == DNS_RRTYPE_A) && (ntohs(ans.class) == DNS_RRCLASS_IN) && (ntohs(ans.len) == sizeof(struct ip_addr)) ) { 00813 /* read the answer resource record's TTL, and maximize it if needed */ 00814 pEntry->ttl = ntohl(ans.ttl); 00815 if (pEntry->ttl > DNS_MAX_TTL) { 00816 pEntry->ttl = DNS_MAX_TTL; 00817 } 00818 /* read the IP address after answer resource record's header */ 00819 MEMCPY( &(pEntry->ipaddr), (pHostname+SIZEOF_DNS_ANSWER), sizeof(struct ip_addr)); 00820 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", pEntry->name)); 00821 ip_addr_debug_print(DNS_DEBUG, (&(pEntry->ipaddr))); 00822 LWIP_DEBUGF(DNS_DEBUG, ("\n")); 00823 /* call specified callback function if provided */ 00824 if (pEntry->found) { 00825 (*pEntry->found)(pEntry->name, &pEntry->ipaddr, pEntry->arg); 00826 } 00827 /* deallocate memory and return */ 00828 goto memerr2; 00829 } else { 00830 pHostname = pHostname + SIZEOF_DNS_ANSWER + htons(ans.len); 00831 } 00832 --nanswers; 00833 } 00834 LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in response\n", pEntry->name)); 00835 /* call callback to indicate error, clean up memory and return */ 00836 goto responseerr; 00837 } 00838 } 00839 } 00840 00841 /* deallocate memory and return */ 00842 goto memerr2; 00843 00844 responseerr: 00845 /* ERROR: call specified callback function with NULL as name to indicate an error */ 00846 if (pEntry->found) { 00847 (*pEntry->found)(pEntry->name, NULL, pEntry->arg); 00848 } 00849 /* flush this entry */ 00850 pEntry->state = DNS_STATE_UNUSED; 00851 pEntry->found = NULL; 00852 00853 memerr2: 00854 #if (DNS_USES_STATIC_BUF == 2) 00855 /* free dns buffer */ 00856 mem_free(dns_payload); 00857 #endif /* (DNS_USES_STATIC_BUF == 2) */ 00858 00859 memerr1: 00860 /* free pbuf */ 00861 pbuf_free(p); 00862 return; 00863 } 00864 00865 /** 00866 * Queues a new hostname to resolve and sends out a DNS query for that hostname 00867 * 00868 * @param name the hostname that is to be queried 00869 * @param found a callback founction to be called on success, failure or timeout 00870 * @param callback_arg argument to pass to the callback function 00871 * @return @return a err_t return code. 00872 */ 00873 static err_t 00874 dns_enqueue(const char *name, dns_found_callback found, void *callback_arg) 00875 { 00876 u8_t i; 00877 u8_t lseq, lseqi; 00878 struct dns_table_entry *pEntry = NULL; 00879 00880 /* search an unused entry, or the oldest one */ 00881 lseq = lseqi = 0; 00882 for (i = 0; i < DNS_TABLE_SIZE; ++i) { 00883 pEntry = &dns_table[i]; 00884 /* is it an unused entry ? */ 00885 if (pEntry->state == DNS_STATE_UNUSED) 00886 break; 00887 00888 /* check if this is the oldest completed entry */ 00889 if (pEntry->state == DNS_STATE_DONE) { 00890 if ((dns_seqno - pEntry->seqno) > lseq) { 00891 lseq = dns_seqno - pEntry->seqno; 00892 lseqi = i; 00893 } 00894 } 00895 } 00896 00897 /* if we don't have found an unused entry, use the oldest completed one */ 00898 if (i == DNS_TABLE_SIZE) { 00899 if ((lseqi >= DNS_TABLE_SIZE) || (dns_table[lseqi].state != DNS_STATE_DONE)) { 00900 /* no entry can't be used now, table is full */ 00901 LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS entries table is full\n", name)); 00902 return ERR_MEM; 00903 } else { 00904 /* use the oldest completed one */ 00905 i = lseqi; 00906 pEntry = &dns_table[i]; 00907 } 00908 } 00909 00910 /* use this entry */ 00911 LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS entry %"U16_F"\n", name, (u16_t)(i))); 00912 00913 /* fill the entry */ 00914 pEntry->state = DNS_STATE_NEW; 00915 pEntry->seqno = dns_seqno++; 00916 pEntry->found = found; 00917 pEntry->arg = callback_arg; 00918 strcpy(pEntry->name, name); 00919 00920 /* force to send query without waiting timer */ 00921 dns_check_entry(i); 00922 00923 /* dns query is enqueued */ 00924 return ERR_INPROGRESS; 00925 } 00926 00927 /** 00928 * Resolve a hostname (string) into an IP address. 00929 * NON-BLOCKING callback version for use with raw API!!! 00930 * 00931 * Returns immediately with one of err_t return codes: 00932 * - ERR_OK if hostname is a valid IP address string or the host 00933 * name is already in the local names table. 00934 * - ERR_INPROGRESS enqueue a request to be sent to the DNS server 00935 * for resolution if no errors are present. 00936 * 00937 * @param hostname the hostname that is to be queried 00938 * @param addr pointer to a struct ip_addr where to store the address if it is already 00939 * cached in the dns_table (only valid if ERR_OK is returned!) 00940 * @param found a callback function to be called on success, failure or timeout (only if 00941 * ERR_INPROGRESS is returned!) 00942 * @param callback_arg argument to pass to the callback function 00943 * @return a err_t return code. 00944 */ 00945 err_t 00946 dns_gethostbyname(const char *hostname, struct ip_addr *addr, dns_found_callback found, 00947 void *callback_arg) 00948 { 00949 /* not initialized or no valid server yet, or invalid addr pointer 00950 * or invalid hostname or invalid hostname length */ 00951 if ((dns_pcb == NULL) || (addr == NULL) || 00952 (!hostname) || (!hostname[0]) || 00953 (strlen(hostname) >= DNS_MAX_NAME_LENGTH)) { 00954 return ERR_VAL; 00955 } 00956 00957 #if LWIP_HAVE_LOOPIF 00958 if (strcmp(hostname,"localhost")==0) { 00959 addr->addr = INADDR_LOOPBACK; 00960 return ERR_OK; 00961 } 00962 #endif /* LWIP_HAVE_LOOPIF */ 00963 00964 /* host name already in octet notation? set ip addr and return ERR_OK 00965 * already have this address cached? */ 00966 if (((addr->addr = inet_addr(hostname)) != INADDR_NONE) || 00967 ((addr->addr = dns_lookup(hostname)) != INADDR_NONE)) { 00968 return ERR_OK; 00969 } 00970 00971 /* queue query with specified callback */ 00972 return dns_enqueue(hostname, found, callback_arg); 00973 } 00974 00975 #endif /* LWIP_DNS */
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