lwip_dns.c

00001 /**
00002  * @file
00003  * DNS - host name to IP address resolver.
00004  *
00005  * @defgroup dns DNS
00006  * @ingroup callbackstyle_api
00007  *
00008  * Implements a DNS host name to IP address resolver.
00009  *
00010  * The lwIP DNS resolver functions are used to lookup a host name and
00011  * map it to a numerical IP address. It maintains a list of resolved
00012  * hostnames that can be queried with the dns_lookup() function.
00013  * New hostnames can be resolved using the dns_query() function.
00014  *
00015  * The lwIP version of the resolver also adds a non-blocking version of
00016  * gethostbyname() that will work with a raw API application. This function
00017  * checks for an IP address string first and converts it if it is valid.
00018  * gethostbyname() then does a dns_lookup() to see if the name is
00019  * already in the table. If so, the IP is returned. If not, a query is
00020  * issued and the function returns with a ERR_INPROGRESS status. The app
00021  * using the dns client must then go into a waiting state.
00022  *
00023  * Once a hostname has been resolved (or found to be non-existent),
00024  * the resolver code calls a specified callback function (which
00025  * must be implemented by the module that uses the resolver).
00026  * 
00027  * Multicast DNS queries are supported for names ending on ".local".
00028  * However, only "One-Shot Multicast DNS Queries" are supported (RFC 6762
00029  * chapter 5.1), this is not a fully compliant implementation of continuous
00030  * mDNS querying!
00031  *
00032  * All functions must be called from TCPIP thread.
00033  * 
00034  * @see @ref netconn_common for thread-safe access.
00035  */
00036 
00037 /*
00038  * Port to lwIP from uIP
00039  * by Jim Pettinato April 2007
00040  *
00041  * security fixes and more by Simon Goldschmidt
00042  *
00043  * uIP version Copyright (c) 2002-2003, Adam Dunkels.
00044  * All rights reserved.
00045  *
00046  * Redistribution and use in source and binary forms, with or without
00047  * modification, are permitted provided that the following conditions
00048  * are met:
00049  * 1. Redistributions of source code must retain the above copyright
00050  *    notice, this list of conditions and the following disclaimer.
00051  * 2. Redistributions in binary form must reproduce the above copyright
00052  *    notice, this list of conditions and the following disclaimer in the
00053  *    documentation and/or other materials provided with the distribution.
00054  * 3. The name of the author may not be used to endorse or promote
00055  *    products derived from this software without specific prior
00056  *    written permission.
00057  *
00058  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
00059  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
00060  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
00061  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
00062  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
00063  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
00064  * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
00065  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
00066  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
00067  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
00068  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00069  */
00070 
00071 /*-----------------------------------------------------------------------------
00072  * RFC 1035 - Domain names - implementation and specification
00073  * RFC 2181 - Clarifications to the DNS Specification
00074  *----------------------------------------------------------------------------*/
00075 
00076 /** @todo: define good default values (rfc compliance) */
00077 /** @todo: improve answer parsing, more checkings... */
00078 /** @todo: check RFC1035 - 7.3. Processing responses */
00079 /** @todo: one-shot mDNS: dual-stack fallback to another IP version */
00080 
00081 /*-----------------------------------------------------------------------------
00082  * Includes
00083  *----------------------------------------------------------------------------*/
00084 
00085 #include "lwip/opt.h"
00086 
00087 #if LWIP_DNS /* don't build if not configured for use in lwipopts.h */
00088 
00089 #include "lwip/def.h"
00090 #include "lwip/udp.h"
00091 #include "lwip/mem.h"
00092 #include "lwip/memp.h"
00093 #include "lwip/dns.h"
00094 #include "lwip/prot/dns.h"
00095 
00096 #include <string.h>
00097 
00098 /** Random generator function to create random TXIDs and source ports for queries */
00099 #ifndef DNS_RAND_TXID
00100 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_XID) != 0)
00101 #define DNS_RAND_TXID LWIP_RAND
00102 #else
00103 static u16_t dns_txid;
00104 #define DNS_RAND_TXID() (++dns_txid)
00105 #endif
00106 #endif
00107 
00108 /** Limits the source port to be >= 1024 by default */
00109 #ifndef DNS_PORT_ALLOWED
00110 #define DNS_PORT_ALLOWED(port) ((port) >= 1024)
00111 #endif
00112 
00113 /** DNS maximum number of retries when asking for a name, before "timeout". */
00114 #ifndef DNS_MAX_RETRIES
00115 #define DNS_MAX_RETRIES           4
00116 #endif
00117 
00118 /** DNS resource record max. TTL (one week as default) */
00119 #ifndef DNS_MAX_TTL
00120 #define DNS_MAX_TTL               604800
00121 #elif DNS_MAX_TTL > 0x7FFFFFFF
00122 #error DNS_MAX_TTL must be a positive 32-bit value
00123 #endif
00124 
00125 #if DNS_TABLE_SIZE > 255
00126 #error DNS_TABLE_SIZE must fit into an u8_t
00127 #endif
00128 #if DNS_MAX_SERVERS > 255
00129 #error DNS_MAX_SERVERS must fit into an u8_t
00130 #endif
00131 
00132 /* The number of parallel requests (i.e. calls to dns_gethostbyname
00133  * that cannot be answered from the DNS table.
00134  * This is set to the table size by default.
00135  */
00136 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
00137 #ifndef DNS_MAX_REQUESTS
00138 #define DNS_MAX_REQUESTS          DNS_TABLE_SIZE
00139 #else
00140 #if DNS_MAX_REQUESTS > 255
00141 #error DNS_MAX_REQUESTS must fit into an u8_t
00142 #endif
00143 #endif
00144 #else
00145 /* In this configuration, both arrays have to have the same size and are used
00146  * like one entry (used/free) */
00147 #define DNS_MAX_REQUESTS          DNS_TABLE_SIZE
00148 #endif
00149 
00150 /* The number of UDP source ports used in parallel */
00151 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00152 #ifndef DNS_MAX_SOURCE_PORTS
00153 #define DNS_MAX_SOURCE_PORTS      DNS_MAX_REQUESTS
00154 #else
00155 #if DNS_MAX_SOURCE_PORTS > 255
00156 #error DNS_MAX_SOURCE_PORTS must fit into an u8_t
00157 #endif
00158 #endif
00159 #else
00160 #ifdef DNS_MAX_SOURCE_PORTS
00161 #undef DNS_MAX_SOURCE_PORTS
00162 #endif
00163 #define DNS_MAX_SOURCE_PORTS      1
00164 #endif
00165 
00166 #if LWIP_IPV4 && LWIP_IPV6
00167 #define LWIP_DNS_ADDRTYPE_IS_IPV6(t) (((t) == LWIP_DNS_ADDRTYPE_IPV6_IPV4) || ((t) == LWIP_DNS_ADDRTYPE_IPV6))
00168 #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)))
00169 #define LWIP_DNS_ADDRTYPE_ARG(x) , x
00170 #define LWIP_DNS_ADDRTYPE_ARG_OR_ZERO(x) x
00171 #define LWIP_DNS_SET_ADDRTYPE(x, y) do { x = y; } while(0)
00172 #else
00173 #if LWIP_IPV6
00174 #define LWIP_DNS_ADDRTYPE_IS_IPV6(t) 1
00175 #else
00176 #define LWIP_DNS_ADDRTYPE_IS_IPV6(t) 0
00177 #endif
00178 #define LWIP_DNS_ADDRTYPE_MATCH_IP(t, ip) 1
00179 #define LWIP_DNS_ADDRTYPE_ARG(x)
00180 #define LWIP_DNS_ADDRTYPE_ARG_OR_ZERO(x) 0
00181 #define LWIP_DNS_SET_ADDRTYPE(x, y)
00182 #endif /* LWIP_IPV4 && LWIP_IPV6 */
00183 
00184 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
00185 #define LWIP_DNS_ISMDNS_ARG(x) , x
00186 #else
00187 #define LWIP_DNS_ISMDNS_ARG(x)
00188 #endif
00189 
00190 /** DNS query message structure.
00191     No packing needed: only used locally on the stack. */
00192 struct dns_query {
00193   /* DNS query record starts with either a domain name or a pointer
00194      to a name already present somewhere in the packet. */
00195   u16_t type;
00196   u16_t cls;
00197 };
00198 #define SIZEOF_DNS_QUERY 4
00199 
00200 /** DNS answer message structure.
00201     No packing needed: only used locally on the stack. */
00202 struct dns_answer {
00203   /* DNS answer record starts with either a domain name or a pointer
00204      to a name already present somewhere in the packet. */
00205   u16_t type;
00206   u16_t cls;
00207   u32_t ttl;
00208   u16_t len;
00209 };
00210 #define SIZEOF_DNS_ANSWER 10
00211 /* maximum allowed size for the struct due to non-packed */
00212 #define SIZEOF_DNS_ANSWER_ASSERT 12
00213 
00214 /* DNS table entry states */
00215 typedef enum {
00216   DNS_STATE_UNUSED           = 0,
00217   DNS_STATE_NEW              = 1,
00218   DNS_STATE_ASKING           = 2,
00219   DNS_STATE_DONE             = 3
00220 } dns_state_enum_t;
00221 
00222 /** DNS table entry */
00223 struct dns_table_entry {
00224   u32_t ttl;
00225   ip_addr_t ipaddr;
00226   u16_t txid;
00227   u8_t  state;
00228   u8_t  server_idx;
00229   u8_t  tmr;
00230   u8_t  retries;
00231   u8_t  seqno;
00232 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00233   u8_t pcb_idx;
00234 #endif
00235   char name[DNS_MAX_NAME_LENGTH];
00236 #if LWIP_IPV4 && LWIP_IPV6
00237   u8_t reqaddrtype;
00238 #endif /* LWIP_IPV4 && LWIP_IPV6 */
00239 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
00240   u8_t is_mdns;
00241 #endif
00242 };
00243 
00244 /** DNS request table entry: used when dns_gehostbyname cannot answer the
00245  * request from the DNS table */
00246 struct dns_req_entry {
00247   /* pointer to callback on DNS query done */
00248   dns_found_callback found;
00249   /* argument passed to the callback function */
00250   void *arg;
00251 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
00252   u8_t dns_table_idx;
00253 #endif
00254 #if LWIP_IPV4 && LWIP_IPV6
00255   u8_t reqaddrtype;
00256 #endif /* LWIP_IPV4 && LWIP_IPV6 */
00257 };
00258 
00259 #if DNS_LOCAL_HOSTLIST
00260 
00261 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
00262 /** Local host-list. For hostnames in this list, no
00263  *  external name resolution is performed */
00264 static struct local_hostlist_entry *local_hostlist_dynamic;
00265 #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00266 
00267 /** Defining this allows the local_hostlist_static to be placed in a different
00268  * linker section (e.g. FLASH) */
00269 #ifndef DNS_LOCAL_HOSTLIST_STORAGE_PRE
00270 #define DNS_LOCAL_HOSTLIST_STORAGE_PRE static
00271 #endif /* DNS_LOCAL_HOSTLIST_STORAGE_PRE */
00272 /** Defining this allows the local_hostlist_static to be placed in a different
00273  * linker section (e.g. FLASH) */
00274 #ifndef DNS_LOCAL_HOSTLIST_STORAGE_POST
00275 #define DNS_LOCAL_HOSTLIST_STORAGE_POST
00276 #endif /* DNS_LOCAL_HOSTLIST_STORAGE_POST */
00277 DNS_LOCAL_HOSTLIST_STORAGE_PRE struct local_hostlist_entry local_hostlist_static[]
00278   DNS_LOCAL_HOSTLIST_STORAGE_POST = DNS_LOCAL_HOSTLIST_INIT;
00279 
00280 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00281 
00282 static void dns_init_local(void);
00283 #endif /* DNS_LOCAL_HOSTLIST */
00284 
00285 
00286 /* forward declarations */
00287 static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port);
00288 static void dns_check_entries(void);
00289 static void dns_call_found(u8_t idx, ip_addr_t* addr);
00290 
00291 /*-----------------------------------------------------------------------------
00292  * Globals
00293  *----------------------------------------------------------------------------*/
00294 
00295 /* DNS variables */
00296 static struct udp_pcb        *dns_pcbs[DNS_MAX_SOURCE_PORTS];
00297 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00298 static u8_t                   dns_last_pcb_idx;
00299 #endif
00300 static u8_t                   dns_seqno;
00301 static struct dns_table_entry dns_table[DNS_TABLE_SIZE];
00302 static struct dns_req_entry   dns_requests[DNS_MAX_REQUESTS];
00303 static ip_addr_t              dns_servers[DNS_MAX_SERVERS];
00304 
00305 #if LWIP_IPV4
00306 const ip_addr_t dns_mquery_v4group = DNS_MQUERY_IPV4_GROUP_INIT;
00307 #endif /* LWIP_IPV4 */
00308 #if LWIP_IPV6
00309 const ip_addr_t dns_mquery_v6group = DNS_MQUERY_IPV6_GROUP_INIT;
00310 #endif /* LWIP_IPV6 */
00311 
00312 /**
00313  * Initialize the resolver: set up the UDP pcb and configure the default server
00314  * (if DNS_SERVER_ADDRESS is set).
00315  */
00316 void
00317 dns_init(void)
00318 {
00319 #ifdef DNS_SERVER_ADDRESS
00320   /* initialize default DNS server address */
00321   ip_addr_t dnsserver;
00322   DNS_SERVER_ADDRESS(&dnsserver);
00323   dns_setserver(0, &dnsserver);
00324 #endif /* DNS_SERVER_ADDRESS */
00325 
00326   LWIP_ASSERT("sanity check SIZEOF_DNS_QUERY",
00327     sizeof(struct dns_query) == SIZEOF_DNS_QUERY);
00328   LWIP_ASSERT("sanity check SIZEOF_DNS_ANSWER",
00329     sizeof(struct dns_answer) <= SIZEOF_DNS_ANSWER_ASSERT);
00330 
00331   LWIP_DEBUGF(DNS_DEBUG, ("dns_init: initializing\n"));
00332 
00333   /* if dns client not yet initialized... */
00334 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) == 0)
00335   if (dns_pcbs[0] == NULL) {
00336     dns_pcbs[0] = udp_new_ip_type(IPADDR_TYPE_ANY);
00337     LWIP_ASSERT("dns_pcbs[0] != NULL", dns_pcbs[0] != NULL);
00338 
00339     /* initialize DNS table not needed (initialized to zero since it is a
00340      * global variable) */
00341     LWIP_ASSERT("For implicit initialization to work, DNS_STATE_UNUSED needs to be 0",
00342       DNS_STATE_UNUSED == 0);
00343 
00344     /* initialize DNS client */
00345     udp_bind(dns_pcbs[0], IP_ANY_TYPE, 0);
00346     udp_recv(dns_pcbs[0], dns_recv, NULL);
00347   }
00348 #endif
00349 
00350 #if DNS_LOCAL_HOSTLIST
00351   dns_init_local();
00352 #endif
00353 }
00354 
00355 /**
00356  * @ingroup dns
00357  * Initialize one of the DNS servers.
00358  *
00359  * @param numdns the index of the DNS server to set must be < DNS_MAX_SERVERS
00360  * @param dnsserver IP address of the DNS server to set
00361  */
00362 void
00363 dns_setserver(u8_t numdns, const ip_addr_t *dnsserver)
00364 {
00365   if (numdns < DNS_MAX_SERVERS) {
00366     if (dnsserver != NULL) {
00367       dns_servers[numdns] = (*dnsserver);
00368     } else {
00369       dns_servers[numdns] = *IP_ADDR_ANY;
00370     }
00371   }
00372 }
00373 
00374 /**
00375  * @ingroup dns
00376  * Obtain one of the currently configured DNS server.
00377  *
00378  * @param numdns the index of the DNS server
00379  * @return IP address of the indexed DNS server or "ip_addr_any" if the DNS
00380  *         server has not been configured.
00381  */
00382 const ip_addr_t*
00383 dns_getserver(u8_t numdns)
00384 {
00385   if (numdns < DNS_MAX_SERVERS) {
00386     return &dns_servers[numdns];
00387   } else {
00388     return IP_ADDR_ANY;
00389   }
00390 }
00391 
00392 /**
00393  * The DNS resolver client timer - handle retries and timeouts and should
00394  * be called every DNS_TMR_INTERVAL milliseconds (every second by default).
00395  */
00396 void
00397 dns_tmr(void)
00398 {
00399   LWIP_DEBUGF(DNS_DEBUG, ("dns_tmr: dns_check_entries\n"));
00400   dns_check_entries();
00401 }
00402 
00403 #if DNS_LOCAL_HOSTLIST
00404 static void
00405 dns_init_local(void)
00406 {
00407 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT)
00408   size_t i;
00409   struct local_hostlist_entry *entry;
00410   /* Dynamic: copy entries from DNS_LOCAL_HOSTLIST_INIT to list */
00411   struct local_hostlist_entry local_hostlist_init[] = DNS_LOCAL_HOSTLIST_INIT;
00412   size_t namelen;
00413   for (i = 0; i < LWIP_ARRAYSIZE(local_hostlist_init); i++) {
00414     struct local_hostlist_entry *init_entry = &local_hostlist_init[i];
00415     LWIP_ASSERT("invalid host name (NULL)", init_entry->name != NULL);
00416     namelen = strlen(init_entry->name);
00417     LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN);
00418     entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST);
00419     LWIP_ASSERT("mem-error in dns_init_local", entry != NULL);
00420     if (entry != NULL) {
00421       char* entry_name = (char*)entry + sizeof(struct local_hostlist_entry);
00422       MEMCPY(entry_name, init_entry->name, namelen);
00423       entry_name[namelen] = 0;
00424       entry->name = entry_name;
00425       entry->addr = init_entry->addr;
00426       entry->next = local_hostlist_dynamic;
00427       local_hostlist_dynamic = entry;
00428     }
00429   }
00430 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT) */
00431 }
00432 
00433 /**
00434  * @ingroup dns
00435  * Scans the local host-list for a hostname.
00436  *
00437  * @param hostname Hostname to look for in the local host-list
00438  * @param addr the first IP address for the hostname in the local host-list or
00439  *         IPADDR_NONE if not found.
00440  * @return ERR_OK if found, ERR_ARG if not found
00441  */
00442 static err_t
00443 dns_lookup_local(const char *hostname, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype))
00444 {
00445 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
00446   struct local_hostlist_entry *entry = local_hostlist_dynamic;
00447   while (entry != NULL) {
00448     if ((lwip_stricmp(entry->name, hostname) == 0) &&
00449         LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, entry->addr)) {
00450       if (addr) {
00451         ip_addr_copy(*addr, entry->addr);
00452       }
00453       return ERR_OK;
00454     }
00455     entry = entry->next;
00456   }
00457 #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00458   size_t i;
00459   for (i = 0; i < LWIP_ARRAYSIZE(local_hostlist_static); i++) {
00460     if ((lwip_stricmp(local_hostlist_static[i].name, hostname) == 0) &&
00461         LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, local_hostlist_static[i].addr)) {
00462       if (addr) {
00463         ip_addr_copy(*addr, local_hostlist_static[i].addr);
00464       }
00465       return ERR_OK;
00466     }
00467   }
00468 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00469   return ERR_ARG;
00470 }
00471 
00472 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
00473 /**
00474  * @ingroup dns
00475  * Remove all entries from the local host-list for a specific hostname
00476  * and/or IP address
00477  *
00478  * @param hostname hostname for which entries shall be removed from the local
00479  *                 host-list
00480  * @param addr address for which entries shall be removed from the local host-list
00481  * @return the number of removed entries
00482  */
00483 int
00484 dns_local_removehost(const char *hostname, const ip_addr_t *addr)
00485 {
00486   int removed = 0;
00487   struct local_hostlist_entry *entry = local_hostlist_dynamic;
00488   struct local_hostlist_entry *last_entry = NULL;
00489   while (entry != NULL) {
00490     if (((hostname == NULL) || !lwip_stricmp(entry->name, hostname)) &&
00491         ((addr == NULL) || ip_addr_cmp(&entry->addr, addr))) {
00492       struct local_hostlist_entry *free_entry;
00493       if (last_entry != NULL) {
00494         last_entry->next = entry->next;
00495       } else {
00496         local_hostlist_dynamic = entry->next;
00497       }
00498       free_entry = entry;
00499       entry = entry->next;
00500       memp_free(MEMP_LOCALHOSTLIST, free_entry);
00501       removed++;
00502     } else {
00503       last_entry = entry;
00504       entry = entry->next;
00505     }
00506   }
00507   return removed;
00508 }
00509 
00510 /**
00511  * @ingroup dns
00512  * Add a hostname/IP address pair to the local host-list.
00513  * Duplicates are not checked.
00514  *
00515  * @param hostname hostname of the new entry
00516  * @param addr IP address of the new entry
00517  * @return ERR_OK if succeeded or ERR_MEM on memory error
00518  */
00519 err_t
00520 dns_local_addhost(const char *hostname, const ip_addr_t *addr)
00521 {
00522   struct local_hostlist_entry *entry;
00523   size_t namelen;
00524   char* entry_name;
00525   LWIP_ASSERT("invalid host name (NULL)", hostname != NULL);
00526   namelen = strlen(hostname);
00527   LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN);
00528   entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST);
00529   if (entry == NULL) {
00530     return ERR_MEM;
00531   }
00532   entry_name = (char*)entry + sizeof(struct local_hostlist_entry);
00533   MEMCPY(entry_name, hostname, namelen);
00534   entry_name[namelen] = 0;
00535   entry->name = entry_name;
00536   ip_addr_copy(entry->addr, *addr);
00537   entry->next = local_hostlist_dynamic;
00538   local_hostlist_dynamic = entry;
00539   return ERR_OK;
00540 }
00541 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC*/
00542 #endif /* DNS_LOCAL_HOSTLIST */
00543 
00544 /**
00545  * @ingroup dns
00546  * Look up a hostname in the array of known hostnames.
00547  *
00548  * @note This function only looks in the internal array of known
00549  * hostnames, it does not send out a query for the hostname if none
00550  * was found. The function dns_enqueue() can be used to send a query
00551  * for a hostname.
00552  *
00553  * @param name the hostname to look up
00554  * @param addr the hostname's IP address, as u32_t (instead of ip_addr_t to
00555  *         better check for failure: != IPADDR_NONE) or IPADDR_NONE if the hostname
00556  *         was not found in the cached dns_table.
00557  * @return ERR_OK if found, ERR_ARG if not found
00558  */
00559 static err_t
00560 dns_lookup(const char *name, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype))
00561 {
00562   u8_t i;
00563 #if DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN)
00564 #endif /* DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN) */
00565 #if DNS_LOCAL_HOSTLIST
00566   if (dns_lookup_local(name, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)) == ERR_OK) {
00567     return ERR_OK;
00568   }
00569 #endif /* DNS_LOCAL_HOSTLIST */
00570 #ifdef DNS_LOOKUP_LOCAL_EXTERN
00571   if (DNS_LOOKUP_LOCAL_EXTERN(name, addr, LWIP_DNS_ADDRTYPE_ARG_OR_ZERO(dns_addrtype)) == ERR_OK) {
00572     return ERR_OK;
00573   }
00574 #endif /* DNS_LOOKUP_LOCAL_EXTERN */
00575 
00576   /* Walk through name list, return entry if found. If not, return NULL. */
00577   for (i = 0; i < DNS_TABLE_SIZE; ++i) {
00578     if ((dns_table[i].state == DNS_STATE_DONE) &&
00579         (lwip_strnicmp(name, dns_table[i].name, sizeof(dns_table[i].name)) == 0) &&
00580         LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, dns_table[i].ipaddr)) {
00581       LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name));
00582       ip_addr_debug_print(DNS_DEBUG, &(dns_table[i].ipaddr));
00583       LWIP_DEBUGF(DNS_DEBUG, ("\n"));
00584       if (addr) {
00585         ip_addr_copy(*addr, dns_table[i].ipaddr);
00586       }
00587       return ERR_OK;
00588     }
00589   }
00590 
00591   return ERR_ARG;
00592 }
00593 
00594 /**
00595  * Compare the "dotted" name "query" with the encoded name "response"
00596  * to make sure an answer from the DNS server matches the current dns_table
00597  * entry (otherwise, answers might arrive late for hostname not on the list
00598  * any more).
00599  *
00600  * @param query hostname (not encoded) from the dns_table
00601  * @param p pbuf containing the encoded hostname in the DNS response
00602  * @param start_offset offset into p where the name starts
00603  * @return 0xFFFF: names differ, other: names equal -> offset behind name
00604  */
00605 static u16_t
00606 dns_compare_name(const char *query, struct pbuf* p, u16_t start_offset)
00607 {
00608   int n;
00609   u16_t response_offset = start_offset;
00610 
00611   do {
00612     n = pbuf_try_get_at(p, response_offset++);
00613     if (n < 0) {
00614       return 0xFFFF;
00615     }
00616     /** @see RFC 1035 - 4.1.4. Message compression */
00617     if ((n & 0xc0) == 0xc0) {
00618       /* Compressed name: cannot be equal since we don't send them */
00619       return 0xFFFF;
00620     } else {
00621       /* Not compressed name */
00622       while (n > 0) {
00623         int c = pbuf_try_get_at(p, response_offset);
00624         if (c < 0) {
00625           return 0xFFFF;
00626         }
00627         if ((*query) != (u8_t)c) {
00628           return 0xFFFF;
00629         }
00630         ++response_offset;
00631         ++query;
00632         --n;
00633       }
00634       ++query;
00635     }
00636     n = pbuf_try_get_at(p, response_offset);
00637     if (n < 0) {
00638       return 0xFFFF;
00639     }
00640   } while (n != 0);
00641 
00642   return response_offset + 1;
00643 }
00644 
00645 /**
00646  * Walk through a compact encoded DNS name and return the end of the name.
00647  *
00648  * @param p pbuf containing the name
00649  * @param query_idx start index into p pointing to encoded DNS name in the DNS server response
00650  * @return index to end of the name
00651  */
00652 static u16_t
00653 dns_skip_name(struct pbuf* p, u16_t query_idx)
00654 {
00655   int n;
00656   u16_t offset = query_idx;
00657 
00658   do {
00659     n = pbuf_try_get_at(p, offset++);
00660     if (n < 0) {
00661       return 0xFFFF;
00662     }
00663     /** @see RFC 1035 - 4.1.4. Message compression */
00664     if ((n & 0xc0) == 0xc0) {
00665       /* Compressed name: since we only want to skip it (not check it), stop here */
00666       break;
00667     } else {
00668       /* Not compressed name */
00669       if (offset + n >= p->tot_len) {
00670         return 0xFFFF;
00671       }
00672       offset = (u16_t)(offset + n);
00673     }
00674     n = pbuf_try_get_at(p, offset);
00675     if (n < 0) {
00676       return 0xFFFF;
00677     }
00678   } while (n != 0);
00679 
00680   return offset + 1;
00681 }
00682 
00683 /**
00684  * Send a DNS query packet.
00685  *
00686  * @param idx the DNS table entry index for which to send a request
00687  * @return ERR_OK if packet is sent; an err_t indicating the problem otherwise
00688  */
00689 static err_t
00690 dns_send(u8_t idx)
00691 {
00692   err_t err;
00693   struct dns_hdr hdr;
00694   struct dns_query qry;
00695   struct pbuf *p;
00696   u16_t query_idx, copy_len;
00697   const char *hostname, *hostname_part;
00698   u8_t n;
00699   u8_t pcb_idx;
00700   struct dns_table_entry* entry = &dns_table[idx];
00701 
00702   LWIP_DEBUGF(DNS_DEBUG, ("dns_send: dns_servers[%"U16_F"] \"%s\": request\n",
00703               (u16_t)(entry->server_idx), entry->name));
00704   LWIP_ASSERT("dns server out of array", entry->server_idx < DNS_MAX_SERVERS);
00705   if (ip_addr_isany_val(dns_servers[entry->server_idx])
00706 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
00707       && !entry->is_mdns
00708 #endif
00709     ) {
00710     /* DNS server not valid anymore, e.g. PPP netif has been shut down */
00711     /* call specified callback function if provided */
00712     dns_call_found(idx, NULL);
00713     /* flush this entry */
00714     entry->state = DNS_STATE_UNUSED;
00715     return ERR_OK;
00716   }
00717 
00718   /* if here, we have either a new query or a retry on a previous query to process */
00719   p = pbuf_alloc(PBUF_TRANSPORT, (u16_t)(SIZEOF_DNS_HDR + strlen(entry->name) + 2 +
00720                  SIZEOF_DNS_QUERY), PBUF_RAM);
00721   if (p != NULL) {
00722     const ip_addr_t* dst;
00723     u16_t dst_port;
00724     /* fill dns header */
00725     memset(&hdr, 0, SIZEOF_DNS_HDR);
00726     hdr.id = lwip_htons(entry->txid);
00727     hdr.flags1 = DNS_FLAG1_RD;
00728     hdr.numquestions = PP_HTONS(1);
00729     pbuf_take(p, &hdr, SIZEOF_DNS_HDR);
00730     hostname = entry->name;
00731     --hostname;
00732 
00733     /* convert hostname into suitable query format. */
00734     query_idx = SIZEOF_DNS_HDR;
00735     do {
00736       ++hostname;
00737       hostname_part = hostname;
00738       for (n = 0; *hostname != '.' && *hostname != 0; ++hostname) {
00739         ++n;
00740       }
00741       copy_len = (u16_t)(hostname - hostname_part);
00742       pbuf_put_at(p, query_idx, n);
00743       pbuf_take_at(p, hostname_part, copy_len, query_idx + 1);
00744       query_idx += n + 1;
00745     } while (*hostname != 0);
00746     pbuf_put_at(p, query_idx, 0);
00747     query_idx++;
00748 
00749     /* fill dns query */
00750     if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype)) {
00751       qry.type = PP_HTONS(DNS_RRTYPE_AAAA);
00752     } else {
00753       qry.type = PP_HTONS(DNS_RRTYPE_A);
00754     }
00755     qry.cls = PP_HTONS(DNS_RRCLASS_IN);
00756     pbuf_take_at(p, &qry, SIZEOF_DNS_QUERY, query_idx);
00757 
00758 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00759     pcb_idx = entry->pcb_idx;
00760 #else
00761     pcb_idx = 0;
00762 #endif
00763     /* send dns packet */
00764     LWIP_DEBUGF(DNS_DEBUG, ("sending DNS request ID %d for name \"%s\" to server %d\r\n",
00765       entry->txid, entry->name, entry->server_idx));
00766 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
00767     if (entry->is_mdns) {
00768       dst_port = DNS_MQUERY_PORT;
00769 #if LWIP_IPV6
00770       if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype))
00771       {
00772         dst = &dns_mquery_v6group;
00773       }
00774 #endif
00775 #if LWIP_IPV4 && LWIP_IPV6
00776       else
00777 #endif
00778 #if LWIP_IPV4
00779       {
00780         dst = &dns_mquery_v4group;
00781       }
00782 #endif
00783     } else
00784 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
00785     {
00786       dst_port = DNS_SERVER_PORT;
00787       dst = &dns_servers[entry->server_idx];
00788     }
00789     err = udp_sendto(dns_pcbs[pcb_idx], p, dst, dst_port);
00790 
00791     /* free pbuf */
00792     pbuf_free(p);
00793   } else {
00794     err = ERR_MEM;
00795   }
00796 
00797   return err;
00798 }
00799 
00800 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00801 static struct udp_pcb*
00802 dns_alloc_random_port(void)
00803 {
00804   err_t err;
00805   struct udp_pcb* ret;
00806 
00807   ret = udp_new_ip_type(IPADDR_TYPE_ANY);
00808   if (ret == NULL) {
00809     /* out of memory, have to reuse an existing pcb */
00810     return NULL;
00811   }
00812   do {
00813     u16_t port = (u16_t)DNS_RAND_TXID();
00814     if (!DNS_PORT_ALLOWED(port)) {
00815       /* this port is not allowed, try again */
00816       err = ERR_USE;
00817       continue;
00818     }
00819     err = udp_bind(ret, IP_ANY_TYPE, port);
00820   } while (err == ERR_USE);
00821   if (err != ERR_OK) {
00822     udp_remove(ret);
00823     return NULL;
00824   }
00825   udp_recv(ret, dns_recv, NULL);
00826   return ret;
00827 }
00828 
00829 /**
00830  * dns_alloc_pcb() - allocates a new pcb (or reuses an existing one) to be used
00831  * for sending a request
00832  *
00833  * @return an index into dns_pcbs
00834  */
00835 static u8_t
00836 dns_alloc_pcb(void)
00837 {
00838   u8_t i;
00839   u8_t idx;
00840 
00841   for (i = 0; i < DNS_MAX_SOURCE_PORTS; i++) {
00842     if (dns_pcbs[i] == NULL) {
00843       break;
00844     }
00845   }
00846   if (i < DNS_MAX_SOURCE_PORTS) {
00847     dns_pcbs[i] = dns_alloc_random_port();
00848     if (dns_pcbs[i] != NULL) {
00849       /* succeeded */
00850       dns_last_pcb_idx = i;
00851       return i;
00852     }
00853   }
00854   /* if we come here, creating a new UDP pcb failed, so we have to use
00855      an already existing one */
00856   for (i = 0, idx = dns_last_pcb_idx + 1; i < DNS_MAX_SOURCE_PORTS; i++, idx++) {
00857     if (idx >= DNS_MAX_SOURCE_PORTS) {
00858       idx = 0;
00859     }
00860     if (dns_pcbs[idx] != NULL) {
00861       dns_last_pcb_idx = idx;
00862       return idx;
00863     }
00864   }
00865   return DNS_MAX_SOURCE_PORTS;
00866 }
00867 #endif /* ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0) */
00868 
00869 /**
00870  * dns_call_found() - call the found callback and check if there are duplicate
00871  * entries for the given hostname. If there are any, their found callback will
00872  * be called and they will be removed.
00873  *
00874  * @param idx dns table index of the entry that is resolved or removed
00875  * @param addr IP address for the hostname (or NULL on error or memory shortage)
00876  */
00877 static void
00878 dns_call_found(u8_t idx, ip_addr_t* addr)
00879 {
00880 #if ((LWIP_DNS_SECURE & (LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING | LWIP_DNS_SECURE_RAND_SRC_PORT)) != 0)
00881   u8_t i;
00882 #endif
00883 
00884 #if LWIP_IPV4 && LWIP_IPV6
00885   if (addr != NULL) {
00886     /* check that address type matches the request and adapt the table entry */
00887     if (IP_IS_V6_VAL(*addr)) {
00888       LWIP_ASSERT("invalid response", LWIP_DNS_ADDRTYPE_IS_IPV6(dns_table[idx].reqaddrtype));
00889       dns_table[idx].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV6;
00890     } else {
00891       LWIP_ASSERT("invalid response", !LWIP_DNS_ADDRTYPE_IS_IPV6(dns_table[idx].reqaddrtype));
00892       dns_table[idx].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV4;
00893     }
00894   }
00895 #endif /* LWIP_IPV4 && LWIP_IPV6 */
00896 
00897 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
00898   for (i = 0; i < DNS_MAX_REQUESTS; i++) {
00899     if (dns_requests[i].found && (dns_requests[i].dns_table_idx == idx)) {
00900       (*dns_requests[i].found)(dns_table[idx].name, addr, dns_requests[i].arg);
00901       /* flush this entry */
00902       dns_requests[i].found = NULL;
00903     }
00904   }
00905 #else
00906   if (dns_requests[idx].found) {
00907     (*dns_requests[idx].found)(dns_table[idx].name, addr, dns_requests[idx].arg);
00908   }
00909   dns_requests[idx].found = NULL;
00910 #endif
00911 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00912   /* close the pcb used unless other request are using it */
00913   for (i = 0; i < DNS_MAX_REQUESTS; i++) {
00914     if (i == idx) {
00915       continue; /* only check other requests */
00916     }
00917     if (dns_table[i].state == DNS_STATE_ASKING) {
00918       if (dns_table[i].pcb_idx == dns_table[idx].pcb_idx) {
00919         /* another request is still using the same pcb */
00920         dns_table[idx].pcb_idx = DNS_MAX_SOURCE_PORTS;
00921         break;
00922       }
00923     }
00924   }
00925   if (dns_table[idx].pcb_idx < DNS_MAX_SOURCE_PORTS) {
00926     /* if we come here, the pcb is not used any more and can be removed */
00927     udp_remove(dns_pcbs[dns_table[idx].pcb_idx]);
00928     dns_pcbs[dns_table[idx].pcb_idx] = NULL;
00929     dns_table[idx].pcb_idx = DNS_MAX_SOURCE_PORTS;
00930   }
00931 #endif
00932 }
00933 
00934 /* Create a query transmission ID that is unique for all outstanding queries */
00935 static u16_t
00936 dns_create_txid(void)
00937 {
00938   u16_t txid;
00939   u8_t i;
00940 
00941 again:
00942   txid = (u16_t)DNS_RAND_TXID();
00943 
00944   /* check whether the ID is unique */
00945   for (i = 0; i < DNS_TABLE_SIZE; i++) {
00946     if ((dns_table[i].state == DNS_STATE_ASKING) &&
00947         (dns_table[i].txid == txid)) {
00948       /* ID already used by another pending query */
00949       goto again;
00950     }
00951   }
00952 
00953   return txid;
00954 }
00955 
00956 /**
00957  * dns_check_entry() - see if entry has not yet been queried and, if so, sends out a query.
00958  * Check an entry in the dns_table:
00959  * - send out query for new entries
00960  * - retry old pending entries on timeout (also with different servers)
00961  * - remove completed entries from the table if their TTL has expired
00962  *
00963  * @param i index of the dns_table entry to check
00964  */
00965 static void
00966 dns_check_entry(u8_t i)
00967 {
00968   err_t err;
00969   struct dns_table_entry *entry = &dns_table[i];
00970 
00971   LWIP_ASSERT("array index out of bounds", i < DNS_TABLE_SIZE);
00972 
00973   switch (entry->state) {
00974     case DNS_STATE_NEW:
00975       /* initialize new entry */
00976       entry->txid = dns_create_txid();
00977       entry->state = DNS_STATE_ASKING;
00978       entry->server_idx = 0;
00979       entry->tmr = 1;
00980       entry->retries = 0;
00981 
00982       /* send DNS packet for this entry */
00983       err = dns_send(i);
00984       if (err != ERR_OK) {
00985         LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
00986                     ("dns_send returned error: %s\n", lwip_strerr(err)));
00987       }
00988       break;
00989     case DNS_STATE_ASKING:
00990       if (--entry->tmr == 0) {
00991         if (++entry->retries == DNS_MAX_RETRIES) {
00992           if ((entry->server_idx + 1 < DNS_MAX_SERVERS) && !ip_addr_isany_val(dns_servers[entry->server_idx + 1])
00993 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
00994             && !entry->is_mdns
00995 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
00996             ) {
00997             /* change of server */
00998             entry->server_idx++;
00999             entry->tmr = 1;
01000             entry->retries = 0;
01001           } else {
01002             LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": timeout\n", entry->name));
01003             /* call specified callback function if provided */
01004             dns_call_found(i, NULL);
01005             /* flush this entry */
01006             entry->state = DNS_STATE_UNUSED;
01007             break;
01008           }
01009         } else {
01010           /* wait longer for the next retry */
01011           entry->tmr = entry->retries;
01012         }
01013 
01014         /* send DNS packet for this entry */
01015         err = dns_send(i);
01016         if (err != ERR_OK) {
01017           LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
01018                       ("dns_send returned error: %s\n", lwip_strerr(err)));
01019         }
01020       }
01021       break;
01022     case DNS_STATE_DONE:
01023       /* if the time to live is nul */
01024       if ((entry->ttl == 0) || (--entry->ttl == 0)) {
01025         LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": flush\n", entry->name));
01026         /* flush this entry, there cannot be any related pending entries in this state */
01027         entry->state = DNS_STATE_UNUSED;
01028       }
01029       break;
01030     case DNS_STATE_UNUSED:
01031       /* nothing to do */
01032       break;
01033     default:
01034       LWIP_ASSERT("unknown dns_table entry state:", 0);
01035       break;
01036   }
01037 }
01038 
01039 /**
01040  * Call dns_check_entry for each entry in dns_table - check all entries.
01041  */
01042 static void
01043 dns_check_entries(void)
01044 {
01045   u8_t i;
01046 
01047   for (i = 0; i < DNS_TABLE_SIZE; ++i) {
01048     dns_check_entry(i);
01049   }
01050 }
01051 
01052 /**
01053  * Save TTL and call dns_call_found for correct response.
01054  */
01055 static void
01056 dns_correct_response(u8_t idx, u32_t ttl)
01057 {
01058   struct dns_table_entry *entry = &dns_table[idx];
01059 
01060   entry->state = DNS_STATE_DONE;
01061 
01062   LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", entry->name));
01063   ip_addr_debug_print(DNS_DEBUG, (&(entry->ipaddr)));
01064   LWIP_DEBUGF(DNS_DEBUG, ("\n"));
01065 
01066   /* read the answer resource record's TTL, and maximize it if needed */
01067   entry->ttl = ttl;
01068   if (entry->ttl > DNS_MAX_TTL) {
01069     entry->ttl = DNS_MAX_TTL;
01070   }
01071   dns_call_found(idx, &entry->ipaddr);
01072 
01073   if (entry->ttl == 0) {
01074     /* RFC 883, page 29: "Zero values are
01075        interpreted to mean that the RR can only be used for the
01076        transaction in progress, and should not be cached."
01077        -> flush this entry now */
01078     /* entry reused during callback? */
01079     if (entry->state == DNS_STATE_DONE) {
01080       entry->state = DNS_STATE_UNUSED;
01081     }
01082   }
01083 }
01084 /**
01085  * Receive input function for DNS response packets arriving for the dns UDP pcb.
01086  */
01087 static void
01088 dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
01089 {
01090   u8_t i;
01091   u16_t txid;
01092   u16_t res_idx;
01093   struct dns_hdr hdr;
01094   struct dns_answer ans;
01095   struct dns_query qry;
01096   u16_t nquestions, nanswers;
01097 
01098   LWIP_UNUSED_ARG(arg);
01099   LWIP_UNUSED_ARG(pcb);
01100   LWIP_UNUSED_ARG(port);
01101 
01102   /* is the dns message big enough ? */
01103   if (p->tot_len < (SIZEOF_DNS_HDR + SIZEOF_DNS_QUERY)) {
01104     LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too small\n"));
01105     /* free pbuf and return */
01106     goto memerr;
01107   }
01108 
01109   /* copy dns payload inside static buffer for processing */
01110   if (pbuf_copy_partial(p, &hdr, SIZEOF_DNS_HDR, 0) == SIZEOF_DNS_HDR) {
01111     /* Match the ID in the DNS header with the name table. */
01112     txid = lwip_htons(hdr.id);
01113     for (i = 0; i < DNS_TABLE_SIZE; i++) {
01114       const struct dns_table_entry *entry = &dns_table[i];
01115       if ((entry->state == DNS_STATE_ASKING) &&
01116           (entry->txid == txid)) {
01117 
01118         /* We only care about the question(s) and the answers. The authrr
01119            and the extrarr are simply discarded. */
01120         nquestions = lwip_htons(hdr.numquestions);
01121         nanswers   = lwip_htons(hdr.numanswers);
01122 
01123         /* Check for correct response. */
01124         if ((hdr.flags1 & DNS_FLAG1_RESPONSE) == 0) {
01125           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": not a response\n", entry->name));
01126           goto memerr; /* ignore this packet */
01127         }
01128         if (nquestions != 1) {
01129           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
01130           goto memerr; /* ignore this packet */
01131         }
01132 
01133 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01134         if (!entry->is_mdns)
01135 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
01136         {
01137           /* Check whether response comes from the same network address to which the
01138              question was sent. (RFC 5452) */
01139           if (!ip_addr_cmp(addr, &dns_servers[entry->server_idx])) {
01140             goto memerr; /* ignore this packet */
01141           }
01142         }
01143 
01144         /* Check if the name in the "question" part match with the name in the entry and
01145            skip it if equal. */
01146         res_idx = dns_compare_name(entry->name, p, SIZEOF_DNS_HDR);
01147         if (res_idx == 0xFFFF) {
01148           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
01149           goto memerr; /* ignore this packet */
01150         }
01151 
01152         /* check if "question" part matches the request */
01153         if (pbuf_copy_partial(p, &qry, SIZEOF_DNS_QUERY, res_idx) != SIZEOF_DNS_QUERY) {
01154           goto memerr; /* ignore this packet */
01155         }
01156         if ((qry.cls != PP_HTONS(DNS_RRCLASS_IN)) ||
01157           (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype) && (qry.type != PP_HTONS(DNS_RRTYPE_AAAA))) ||
01158           (!LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype) && (qry.type != PP_HTONS(DNS_RRTYPE_A)))) {
01159           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
01160           goto memerr; /* ignore this packet */
01161         }
01162         /* skip the rest of the "question" part */
01163         res_idx += SIZEOF_DNS_QUERY;
01164 
01165         /* Check for error. If so, call callback to inform. */
01166         if (hdr.flags2 & DNS_FLAG2_ERR_MASK) {
01167           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", entry->name));
01168         } else {
01169           while ((nanswers > 0) && (res_idx < p->tot_len)) {
01170             /* skip answer resource record's host name */
01171             res_idx = dns_skip_name(p, res_idx);
01172             if (res_idx == 0xFFFF) {
01173               goto memerr; /* ignore this packet */
01174             }
01175 
01176             /* Check for IP address type and Internet class. Others are discarded. */
01177             if (pbuf_copy_partial(p, &ans, SIZEOF_DNS_ANSWER, res_idx) != SIZEOF_DNS_ANSWER) {
01178               goto memerr; /* ignore this packet */
01179             }
01180             res_idx += SIZEOF_DNS_ANSWER;
01181 
01182             if (ans.cls == PP_HTONS(DNS_RRCLASS_IN)) {
01183 #if LWIP_IPV4
01184               if ((ans.type == PP_HTONS(DNS_RRTYPE_A)) && (ans.len == PP_HTONS(sizeof(ip4_addr_t)))) {
01185 #if LWIP_IPV4 && LWIP_IPV6
01186                 if (!LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype))
01187 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01188                 {
01189                   ip4_addr_t ip4addr;
01190                   /* read the IP address after answer resource record's header */
01191                   if (pbuf_copy_partial(p, &ip4addr, sizeof(ip4_addr_t), res_idx) != sizeof(ip4_addr_t)) {
01192                     goto memerr; /* ignore this packet */
01193                   }
01194                   ip_addr_copy_from_ip4(dns_table[i].ipaddr, ip4addr);
01195                   pbuf_free(p);
01196                   /* handle correct response */
01197                   dns_correct_response(i, lwip_ntohl(ans.ttl));
01198                   return;
01199                 }
01200               }
01201 #endif /* LWIP_IPV4 */
01202 #if LWIP_IPV6
01203               if ((ans.type == PP_HTONS(DNS_RRTYPE_AAAA)) && (ans.len == PP_HTONS(sizeof(ip6_addr_t)))) {
01204 #if LWIP_IPV4 && LWIP_IPV6
01205                 if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype))
01206 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01207                 {
01208                   ip6_addr_t ip6addr;
01209                   /* read the IP address after answer resource record's header */
01210                   if (pbuf_copy_partial(p, &ip6addr, sizeof(ip6_addr_t), res_idx) != sizeof(ip6_addr_t)) {
01211                     goto memerr; /* ignore this packet */
01212                   }
01213                   ip_addr_copy_from_ip6(dns_table[i].ipaddr, ip6addr);
01214                   pbuf_free(p);
01215                   /* handle correct response */
01216                   dns_correct_response(i, lwip_ntohl(ans.ttl));
01217                   return;
01218                 }
01219               }
01220 #endif /* LWIP_IPV6 */
01221             }
01222             /* skip this answer */
01223             if ((int)(res_idx + lwip_htons(ans.len)) > 0xFFFF) {
01224               goto memerr; /* ignore this packet */
01225             }
01226             res_idx += lwip_htons(ans.len);
01227             --nanswers;
01228           }
01229 #if LWIP_IPV4 && LWIP_IPV6
01230           if ((entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) ||
01231               (entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV6_IPV4)) {
01232             if (entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) {
01233               /* IPv4 failed, try IPv6 */
01234               dns_table[i].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV6;
01235             } else {
01236               /* IPv6 failed, try IPv4 */
01237               dns_table[i].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV4;
01238             }
01239             pbuf_free(p);
01240             dns_table[i].state = DNS_STATE_NEW;
01241             dns_check_entry(i);
01242             return;
01243           }
01244 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01245           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in response\n", entry->name));
01246         }
01247         /* call callback to indicate error, clean up memory and return */
01248         pbuf_free(p);
01249         dns_call_found(i, NULL);
01250         dns_table[i].state = DNS_STATE_UNUSED;
01251         return;
01252       }
01253     }
01254   }
01255 
01256 memerr:
01257   /* deallocate memory and return */
01258   pbuf_free(p);
01259   return;
01260 }
01261 
01262 /**
01263  * Queues a new hostname to resolve and sends out a DNS query for that hostname
01264  *
01265  * @param name the hostname that is to be queried
01266  * @param hostnamelen length of the hostname
01267  * @param found a callback function to be called on success, failure or timeout
01268  * @param callback_arg argument to pass to the callback function
01269  * @return err_t return code.
01270  */
01271 static err_t
01272 dns_enqueue(const char *name, size_t hostnamelen, dns_found_callback found,
01273             void *callback_arg LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype) LWIP_DNS_ISMDNS_ARG(u8_t is_mdns))
01274 {
01275   u8_t i;
01276   u8_t lseq, lseqi;
01277   struct dns_table_entry *entry = NULL;
01278   size_t namelen;
01279   struct dns_req_entry* req;
01280 
01281 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
01282   u8_t r;
01283   /* check for duplicate entries */
01284   for (i = 0; i < DNS_TABLE_SIZE; i++) {
01285     if ((dns_table[i].state == DNS_STATE_ASKING) &&
01286         (lwip_strnicmp(name, dns_table[i].name, sizeof(dns_table[i].name)) == 0)) {
01287 #if LWIP_IPV4 && LWIP_IPV6
01288       if (dns_table[i].reqaddrtype != dns_addrtype) {
01289         /* requested address types don't match
01290            this can lead to 2 concurrent requests, but mixing the address types
01291            for the same host should not be that common */
01292         continue;
01293       }
01294 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01295       /* this is a duplicate entry, find a free request entry */
01296       for (r = 0; r < DNS_MAX_REQUESTS; r++) {
01297         if (dns_requests[r].found == 0) {
01298           dns_requests[r].found = found;
01299           dns_requests[r].arg = callback_arg;
01300           dns_requests[r].dns_table_idx = i;
01301           LWIP_DNS_SET_ADDRTYPE(dns_requests[r].reqaddrtype, dns_addrtype);
01302           LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": duplicate request\n", name));
01303           return ERR_INPROGRESS;
01304         }
01305       }
01306     }
01307   }
01308   /* no duplicate entries found */
01309 #endif
01310 
01311   /* search an unused entry, or the oldest one */
01312   lseq = 0;
01313   lseqi = DNS_TABLE_SIZE;
01314   for (i = 0; i < DNS_TABLE_SIZE; ++i) {
01315     entry = &dns_table[i];
01316     /* is it an unused entry ? */
01317     if (entry->state == DNS_STATE_UNUSED) {
01318       break;
01319     }
01320     /* check if this is the oldest completed entry */
01321     if (entry->state == DNS_STATE_DONE) {
01322       u8_t age = dns_seqno - entry->seqno;
01323       if (age > lseq) {
01324         lseq = age;
01325         lseqi = i;
01326       }
01327     }
01328   }
01329 
01330   /* if we don't have found an unused entry, use the oldest completed one */
01331   if (i == DNS_TABLE_SIZE) {
01332     if ((lseqi >= DNS_TABLE_SIZE) || (dns_table[lseqi].state != DNS_STATE_DONE)) {
01333       /* no entry can be used now, table is full */
01334       LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS entries table is full\n", name));
01335       return ERR_MEM;
01336     } else {
01337       /* use the oldest completed one */
01338       i = lseqi;
01339       entry = &dns_table[i];
01340     }
01341   }
01342 
01343 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
01344   /* find a free request entry */
01345   req = NULL;
01346   for (r = 0; r < DNS_MAX_REQUESTS; r++) {
01347     if (dns_requests[r].found == NULL) {
01348       req = &dns_requests[r];
01349       break;
01350     }
01351   }
01352   if (req == NULL) {
01353     /* no request entry can be used now, table is full */
01354     LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS request entries table is full\n", name));
01355     return ERR_MEM;
01356   }
01357   req->dns_table_idx = i;
01358 #else
01359   /* in this configuration, the entry index is the same as the request index */
01360   req = &dns_requests[i];
01361 #endif
01362 
01363   /* use this entry */
01364   LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS entry %"U16_F"\n", name, (u16_t)(i)));
01365 
01366   /* fill the entry */
01367   entry->state = DNS_STATE_NEW;
01368   entry->seqno = dns_seqno;
01369   LWIP_DNS_SET_ADDRTYPE(entry->reqaddrtype, dns_addrtype);
01370   LWIP_DNS_SET_ADDRTYPE(req->reqaddrtype, dns_addrtype);
01371   req->found = found;
01372   req->arg   = callback_arg;
01373   namelen = LWIP_MIN(hostnamelen, DNS_MAX_NAME_LENGTH-1);
01374   MEMCPY(entry->name, name, namelen);
01375   entry->name[namelen] = 0;
01376 
01377 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
01378   entry->pcb_idx = dns_alloc_pcb();
01379   if (entry->pcb_idx >= DNS_MAX_SOURCE_PORTS) {
01380     /* failed to get a UDP pcb */
01381     LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": failed to allocate a pcb\n", name));
01382     entry->state = DNS_STATE_UNUSED;
01383     req->found = NULL;
01384     return ERR_MEM;
01385   }
01386   LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS pcb %"U16_F"\n", name, (u16_t)(entry->pcb_idx)));
01387 #endif
01388 
01389 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01390   entry->is_mdns = is_mdns;
01391 #endif
01392 
01393   dns_seqno++;
01394 
01395   /* force to send query without waiting timer */
01396   dns_check_entry(i);
01397 
01398   /* dns query is enqueued */
01399   return ERR_INPROGRESS;
01400 }
01401 
01402 /**
01403  * @ingroup dns
01404  * Resolve a hostname (string) into an IP address.
01405  * NON-BLOCKING callback version for use with raw API!!!
01406  *
01407  * Returns immediately with one of err_t return codes:
01408  * - ERR_OK if hostname is a valid IP address string or the host
01409  *   name is already in the local names table.
01410  * - ERR_INPROGRESS enqueue a request to be sent to the DNS server
01411  *   for resolution if no errors are present.
01412  * - ERR_ARG: dns client not initialized or invalid hostname
01413  *
01414  * @param hostname the hostname that is to be queried
01415  * @param addr pointer to a ip_addr_t where to store the address if it is already
01416  *             cached in the dns_table (only valid if ERR_OK is returned!)
01417  * @param found a callback function to be called on success, failure or timeout (only if
01418  *              ERR_INPROGRESS is returned!)
01419  * @param callback_arg argument to pass to the callback function
01420  * @return a err_t return code.
01421  */
01422 err_t
01423 dns_gethostbyname(const char *hostname, ip_addr_t *addr, dns_found_callback found,
01424                   void *callback_arg)
01425 {
01426   return dns_gethostbyname_addrtype(hostname, addr, found, callback_arg, LWIP_DNS_ADDRTYPE_DEFAULT);
01427 }
01428 
01429 /**
01430  * @ingroup dns
01431  * Like dns_gethostbyname, but returned address type can be controlled:
01432  * @param hostname the hostname that is to be queried
01433  * @param addr pointer to a ip_addr_t where to store the address if it is already
01434  *             cached in the dns_table (only valid if ERR_OK is returned!)
01435  * @param found a callback function to be called on success, failure or timeout (only if
01436  *              ERR_INPROGRESS is returned!)
01437  * @param callback_arg argument to pass to the callback function
01438  * @param dns_addrtype - LWIP_DNS_ADDRTYPE_IPV4_IPV6: try to resolve IPv4 first, try IPv6 if IPv4 fails only
01439  *                      - LWIP_DNS_ADDRTYPE_IPV6_IPV4: try to resolve IPv6 first, try IPv4 if IPv6 fails only
01440  *                      - LWIP_DNS_ADDRTYPE_IPV4: try to resolve IPv4 only
01441  *                      - LWIP_DNS_ADDRTYPE_IPV6: try to resolve IPv6 only
01442  */
01443 err_t
01444 dns_gethostbyname_addrtype(const char *hostname, ip_addr_t *addr, dns_found_callback found,
01445                            void *callback_arg, u8_t dns_addrtype)
01446 {
01447   size_t hostnamelen;
01448 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01449   u8_t is_mdns;
01450 #endif
01451   /* not initialized or no valid server yet, or invalid addr pointer
01452    * or invalid hostname or invalid hostname length */
01453   if ((addr == NULL) ||
01454       (!hostname) || (!hostname[0])) {
01455     return ERR_ARG;
01456   }
01457 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) == 0)
01458   if (dns_pcbs[0] == NULL) {
01459     return ERR_ARG;
01460   }
01461 #endif
01462   hostnamelen = strlen(hostname);
01463   if (hostnamelen >= DNS_MAX_NAME_LENGTH) {
01464     LWIP_DEBUGF(DNS_DEBUG, ("dns_gethostbyname: name too long to resolve"));
01465     return ERR_ARG;
01466   }
01467 
01468 
01469 #if LWIP_HAVE_LOOPIF
01470   if (strcmp(hostname, "localhost") == 0) {
01471     ip_addr_set_loopback(LWIP_DNS_ADDRTYPE_IS_IPV6(dns_addrtype), addr);
01472     return ERR_OK;
01473   }
01474 #endif /* LWIP_HAVE_LOOPIF */
01475 
01476   /* host name already in octet notation? set ip addr and return ERR_OK */
01477   if (ipaddr_aton(hostname, addr)) {
01478 #if LWIP_IPV4 && LWIP_IPV6
01479     if ((IP_IS_V6(addr) && (dns_addrtype != LWIP_DNS_ADDRTYPE_IPV4)) ||
01480         (IP_IS_V4(addr) && (dns_addrtype != LWIP_DNS_ADDRTYPE_IPV6)))
01481 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01482     {
01483       return ERR_OK;
01484     }
01485   }
01486   /* already have this address cached? */
01487   if (dns_lookup(hostname, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)) == ERR_OK) {
01488     return ERR_OK;
01489   }
01490 #if LWIP_IPV4 && LWIP_IPV6
01491   if ((dns_addrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) || (dns_addrtype == LWIP_DNS_ADDRTYPE_IPV6_IPV4)) {
01492     /* fallback to 2nd IP type and try again to lookup */
01493     u8_t fallback;
01494     if (dns_addrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) {
01495       fallback = LWIP_DNS_ADDRTYPE_IPV6;
01496     } else {
01497       fallback = LWIP_DNS_ADDRTYPE_IPV4;
01498     }
01499     if (dns_lookup(hostname, addr LWIP_DNS_ADDRTYPE_ARG(fallback)) == ERR_OK) {
01500       return ERR_OK;
01501     }
01502   }
01503 #else /* LWIP_IPV4 && LWIP_IPV6 */
01504   LWIP_UNUSED_ARG(dns_addrtype);
01505 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01506 
01507 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01508   if (strstr(hostname, ".local") == &hostname[hostnamelen] - 6) {
01509     is_mdns = 1;
01510   } else {
01511     is_mdns = 0;
01512   }
01513 
01514   if (!is_mdns)
01515 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
01516   {
01517     /* prevent calling found callback if no server is set, return error instead */
01518     if (ip_addr_isany_val(dns_servers[0])) {
01519       return ERR_VAL;
01520     }
01521   }
01522 
01523   /* queue query with specified callback */
01524   return dns_enqueue(hostname, hostnamelen, found, callback_arg LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)
01525      LWIP_DNS_ISMDNS_ARG(is_mdns));
01526 }
01527 
01528 #endif /* LWIP_DNS */