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 static err_t dns_lookup_local(const char *hostname, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype));
00284 #endif /* DNS_LOCAL_HOSTLIST */
00285 
00286 
00287 /* forward declarations */
00288 static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port);
00289 static void dns_check_entries(void);
00290 static void dns_call_found(u8_t idx, ip_addr_t* addr);
00291 
00292 /*-----------------------------------------------------------------------------
00293  * Globals
00294  *----------------------------------------------------------------------------*/
00295 
00296 /* DNS variables */
00297 static struct udp_pcb        *dns_pcbs[DNS_MAX_SOURCE_PORTS];
00298 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00299 static u8_t                   dns_last_pcb_idx;
00300 #endif
00301 static u8_t                   dns_seqno;
00302 static struct dns_table_entry dns_table[DNS_TABLE_SIZE];
00303 static struct dns_req_entry   dns_requests[DNS_MAX_REQUESTS];
00304 static ip_addr_t              dns_servers[DNS_MAX_SERVERS];
00305 
00306 #if LWIP_IPV4
00307 const ip_addr_t dns_mquery_v4group = DNS_MQUERY_IPV4_GROUP_INIT;
00308 #endif /* LWIP_IPV4 */
00309 #if LWIP_IPV6
00310 const ip_addr_t dns_mquery_v6group = DNS_MQUERY_IPV6_GROUP_INIT;
00311 #endif /* LWIP_IPV6 */
00312 
00313 /**
00314  * Initialize the resolver: set up the UDP pcb and configure the default server
00315  * (if DNS_SERVER_ADDRESS is set).
00316  */
00317 void
00318 dns_init(void)
00319 {
00320 #ifdef DNS_SERVER_ADDRESS
00321   /* initialize default DNS server address */
00322   ip_addr_t dnsserver;
00323   DNS_SERVER_ADDRESS(&dnsserver);
00324   dns_setserver(0, &dnsserver);
00325 #endif /* DNS_SERVER_ADDRESS */
00326 
00327   LWIP_ASSERT("sanity check SIZEOF_DNS_QUERY",
00328     sizeof(struct dns_query) == SIZEOF_DNS_QUERY);
00329   LWIP_ASSERT("sanity check SIZEOF_DNS_ANSWER",
00330     sizeof(struct dns_answer) <= SIZEOF_DNS_ANSWER_ASSERT);
00331 
00332   LWIP_DEBUGF(DNS_DEBUG, ("dns_init: initializing\n"));
00333 
00334   /* if dns client not yet initialized... */
00335 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) == 0)
00336   if (dns_pcbs[0] == NULL) {
00337     dns_pcbs[0] = udp_new_ip_type(IPADDR_TYPE_ANY);
00338     LWIP_ASSERT("dns_pcbs[0] != NULL", dns_pcbs[0] != NULL);
00339 
00340     /* initialize DNS table not needed (initialized to zero since it is a
00341      * global variable) */
00342     LWIP_ASSERT("For implicit initialization to work, DNS_STATE_UNUSED needs to be 0",
00343       DNS_STATE_UNUSED == 0);
00344 
00345     /* initialize DNS client */
00346     udp_bind(dns_pcbs[0], IP_ANY_TYPE, 0);
00347     udp_recv(dns_pcbs[0], dns_recv, NULL);
00348   }
00349 #endif
00350 
00351 #if DNS_LOCAL_HOSTLIST
00352   dns_init_local();
00353 #endif
00354 }
00355 
00356 /**
00357  * @ingroup dns
00358  * Initialize one of the DNS servers.
00359  *
00360  * @param numdns the index of the DNS server to set must be < DNS_MAX_SERVERS
00361  * @param dnsserver IP address of the DNS server to set
00362  */
00363 void
00364 dns_setserver(u8_t numdns, const ip_addr_t *dnsserver)
00365 {
00366   if (numdns < DNS_MAX_SERVERS) {
00367     if (dnsserver != NULL) {
00368       dns_servers[numdns] = (*dnsserver);
00369     } else {
00370       dns_servers[numdns] = *IP_ADDR_ANY;
00371     }
00372   }
00373 }
00374 
00375 /**
00376  * @ingroup dns
00377  * Obtain one of the currently configured DNS server.
00378  *
00379  * @param numdns the index of the DNS server
00380  * @return IP address of the indexed DNS server or "ip_addr_any" if the DNS
00381  *         server has not been configured.
00382  */
00383 const ip_addr_t*
00384 dns_getserver(u8_t numdns)
00385 {
00386   if (numdns < DNS_MAX_SERVERS) {
00387     return &dns_servers[numdns];
00388   } else {
00389     return IP_ADDR_ANY;
00390   }
00391 }
00392 
00393 /**
00394  * The DNS resolver client timer - handle retries and timeouts and should
00395  * be called every DNS_TMR_INTERVAL milliseconds (every second by default).
00396  */
00397 void
00398 dns_tmr(void)
00399 {
00400   LWIP_DEBUGF(DNS_DEBUG, ("dns_tmr: dns_check_entries\n"));
00401   dns_check_entries();
00402 }
00403 
00404 #if DNS_LOCAL_HOSTLIST
00405 static void
00406 dns_init_local(void)
00407 {
00408 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT)
00409   size_t i;
00410   struct local_hostlist_entry *entry;
00411   /* Dynamic: copy entries from DNS_LOCAL_HOSTLIST_INIT to list */
00412   struct local_hostlist_entry local_hostlist_init[] = DNS_LOCAL_HOSTLIST_INIT;
00413   size_t namelen;
00414   for (i = 0; i < LWIP_ARRAYSIZE(local_hostlist_init); i++) {
00415     struct local_hostlist_entry *init_entry = &local_hostlist_init[i];
00416     LWIP_ASSERT("invalid host name (NULL)", init_entry->name != NULL);
00417     namelen = strlen(init_entry->name);
00418     LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN);
00419     entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST);
00420     LWIP_ASSERT("mem-error in dns_init_local", entry != NULL);
00421     if (entry != NULL) {
00422       char* entry_name = (char*)entry + sizeof(struct local_hostlist_entry);
00423       MEMCPY(entry_name, init_entry->name, namelen);
00424       entry_name[namelen] = 0;
00425       entry->name = entry_name;
00426       entry->addr = init_entry->addr;
00427       entry->next = local_hostlist_dynamic;
00428       local_hostlist_dynamic = entry;
00429     }
00430   }
00431 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT) */
00432 }
00433 
00434 /**
00435  * @ingroup dns
00436  * Iterate the local host-list for a hostname.
00437  *
00438  * @param iterator_fn a function that is called for every entry in the local host-list
00439  * @param iterator_arg 3rd argument passed to iterator_fn
00440  * @return the number of entries in the local host-list
00441  */
00442 size_t
00443 dns_local_iterate(dns_found_callback iterator_fn, void *iterator_arg)
00444 {
00445   size_t i;
00446 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
00447   struct local_hostlist_entry *entry = local_hostlist_dynamic;
00448   i = 0;
00449   while (entry != NULL) {
00450     if (iterator_fn != NULL) {
00451       iterator_fn(entry->name, &entry->addr, iterator_arg);
00452     }
00453     i++;
00454     entry = entry->next;
00455   }
00456 #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00457   for (i = 0; i < LWIP_ARRAYSIZE(local_hostlist_static); i++) {
00458     if (iterator_fn != NULL) {
00459       iterator_fn(local_hostlist_static[i].name, &local_hostlist_static[i].addr, iterator_arg);
00460     }
00461   }
00462 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00463   return i;
00464 }
00465 
00466 /**
00467  * @ingroup dns
00468  * Scans the local host-list for a hostname.
00469  *
00470  * @param hostname Hostname to look for in the local host-list
00471  * @param addr the first IP address for the hostname in the local host-list or
00472  *         IPADDR_NONE if not found.
00473  * @param dns_addrtype - LWIP_DNS_ADDRTYPE_IPV4_IPV6: try to resolve IPv4 (ATTENTION: no fallback here!)
00474  *                     - LWIP_DNS_ADDRTYPE_IPV6_IPV4: try to resolve IPv6 (ATTENTION: no fallback here!)
00475  *                     - LWIP_DNS_ADDRTYPE_IPV4: try to resolve IPv4 only
00476  *                     - LWIP_DNS_ADDRTYPE_IPV6: try to resolve IPv6 only
00477  * @return ERR_OK if found, ERR_ARG if not found
00478  */
00479 err_t
00480 dns_local_lookup(const char *hostname, ip_addr_t *addr, u8_t dns_addrtype)
00481 {
00482   LWIP_UNUSED_ARG(dns_addrtype);
00483   return dns_lookup_local(hostname, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype));
00484 }
00485 
00486 /* Internal implementation for dns_local_lookup and dns_lookup */
00487 static err_t
00488 dns_lookup_local(const char *hostname, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype))
00489 {
00490 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
00491   struct local_hostlist_entry *entry = local_hostlist_dynamic;
00492   while (entry != NULL) {
00493     if ((lwip_stricmp(entry->name, hostname) == 0) &&
00494         LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, entry->addr)) {
00495       if (addr) {
00496         ip_addr_copy(*addr, entry->addr);
00497       }
00498       return ERR_OK;
00499     }
00500     entry = entry->next;
00501   }
00502 #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00503   size_t i;
00504   for (i = 0; i < LWIP_ARRAYSIZE(local_hostlist_static); i++) {
00505     if ((lwip_stricmp(local_hostlist_static[i].name, hostname) == 0) &&
00506         LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, local_hostlist_static[i].addr)) {
00507       if (addr) {
00508         ip_addr_copy(*addr, local_hostlist_static[i].addr);
00509       }
00510       return ERR_OK;
00511     }
00512   }
00513 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00514   return ERR_ARG;
00515 }
00516 
00517 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
00518 /**
00519  * @ingroup dns
00520  * Remove all entries from the local host-list for a specific hostname
00521  * and/or IP address
00522  *
00523  * @param hostname hostname for which entries shall be removed from the local
00524  *                 host-list
00525  * @param addr address for which entries shall be removed from the local host-list
00526  * @return the number of removed entries
00527  */
00528 int
00529 dns_local_removehost(const char *hostname, const ip_addr_t *addr)
00530 {
00531   int removed = 0;
00532   struct local_hostlist_entry *entry = local_hostlist_dynamic;
00533   struct local_hostlist_entry *last_entry = NULL;
00534   while (entry != NULL) {
00535     if (((hostname == NULL) || !lwip_stricmp(entry->name, hostname)) &&
00536         ((addr == NULL) || ip_addr_cmp(&entry->addr, addr))) {
00537       struct local_hostlist_entry *free_entry;
00538       if (last_entry != NULL) {
00539         last_entry->next = entry->next;
00540       } else {
00541         local_hostlist_dynamic = entry->next;
00542       }
00543       free_entry = entry;
00544       entry = entry->next;
00545       memp_free(MEMP_LOCALHOSTLIST, free_entry);
00546       removed++;
00547     } else {
00548       last_entry = entry;
00549       entry = entry->next;
00550     }
00551   }
00552   return removed;
00553 }
00554 
00555 /**
00556  * @ingroup dns
00557  * Add a hostname/IP address pair to the local host-list.
00558  * Duplicates are not checked.
00559  *
00560  * @param hostname hostname of the new entry
00561  * @param addr IP address of the new entry
00562  * @return ERR_OK if succeeded or ERR_MEM on memory error
00563  */
00564 err_t
00565 dns_local_addhost(const char *hostname, const ip_addr_t *addr)
00566 {
00567   struct local_hostlist_entry *entry;
00568   size_t namelen;
00569   char* entry_name;
00570   LWIP_ASSERT("invalid host name (NULL)", hostname != NULL);
00571   namelen = strlen(hostname);
00572   LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN);
00573   entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST);
00574   if (entry == NULL) {
00575     return ERR_MEM;
00576   }
00577   entry_name = (char*)entry + sizeof(struct local_hostlist_entry);
00578   MEMCPY(entry_name, hostname, namelen);
00579   entry_name[namelen] = 0;
00580   entry->name = entry_name;
00581   ip_addr_copy(entry->addr, *addr);
00582   entry->next = local_hostlist_dynamic;
00583   local_hostlist_dynamic = entry;
00584   return ERR_OK;
00585 }
00586 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC*/
00587 #endif /* DNS_LOCAL_HOSTLIST */
00588 
00589 /**
00590  * @ingroup dns
00591  * Look up a hostname in the array of known hostnames.
00592  *
00593  * @note This function only looks in the internal array of known
00594  * hostnames, it does not send out a query for the hostname if none
00595  * was found. The function dns_enqueue() can be used to send a query
00596  * for a hostname.
00597  *
00598  * @param name the hostname to look up
00599  * @param addr the hostname's IP address, as u32_t (instead of ip_addr_t to
00600  *         better check for failure: != IPADDR_NONE) or IPADDR_NONE if the hostname
00601  *         was not found in the cached dns_table.
00602  * @return ERR_OK if found, ERR_ARG if not found
00603  */
00604 static err_t
00605 dns_lookup(const char *name, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype))
00606 {
00607   u8_t i;
00608 #if DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN)
00609 #endif /* DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN) */
00610 #if DNS_LOCAL_HOSTLIST
00611   if (dns_lookup_local(name, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)) == ERR_OK) {
00612     return ERR_OK;
00613   }
00614 #endif /* DNS_LOCAL_HOSTLIST */
00615 #ifdef DNS_LOOKUP_LOCAL_EXTERN
00616   if (DNS_LOOKUP_LOCAL_EXTERN(name, addr, LWIP_DNS_ADDRTYPE_ARG_OR_ZERO(dns_addrtype)) == ERR_OK) {
00617     return ERR_OK;
00618   }
00619 #endif /* DNS_LOOKUP_LOCAL_EXTERN */
00620 
00621   /* Walk through name list, return entry if found. If not, return NULL. */
00622   for (i = 0; i < DNS_TABLE_SIZE; ++i) {
00623     if ((dns_table[i].state == DNS_STATE_DONE) &&
00624         (lwip_strnicmp(name, dns_table[i].name, sizeof(dns_table[i].name)) == 0) &&
00625         LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, dns_table[i].ipaddr)) {
00626       LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name));
00627       ip_addr_debug_print(DNS_DEBUG, &(dns_table[i].ipaddr));
00628       LWIP_DEBUGF(DNS_DEBUG, ("\n"));
00629       if (addr) {
00630         ip_addr_copy(*addr, dns_table[i].ipaddr);
00631       }
00632       return ERR_OK;
00633     }
00634   }
00635 
00636   return ERR_ARG;
00637 }
00638 
00639 /**
00640  * Compare the "dotted" name "query" with the encoded name "response"
00641  * to make sure an answer from the DNS server matches the current dns_table
00642  * entry (otherwise, answers might arrive late for hostname not on the list
00643  * any more).
00644  *
00645  * @param query hostname (not encoded) from the dns_table
00646  * @param p pbuf containing the encoded hostname in the DNS response
00647  * @param start_offset offset into p where the name starts
00648  * @return 0xFFFF: names differ, other: names equal -> offset behind name
00649  */
00650 static u16_t
00651 dns_compare_name(const char *query, struct pbuf* p, u16_t start_offset)
00652 {
00653   int n;
00654   u16_t response_offset = start_offset;
00655 
00656   do {
00657     n = pbuf_try_get_at(p, response_offset++);
00658     if (n < 0) {
00659       return 0xFFFF;
00660     }
00661     /** @see RFC 1035 - 4.1.4. Message compression */
00662     if ((n & 0xc0) == 0xc0) {
00663       /* Compressed name: cannot be equal since we don't send them */
00664       return 0xFFFF;
00665     } else {
00666       /* Not compressed name */
00667       while (n > 0) {
00668         int c = pbuf_try_get_at(p, response_offset);
00669         if (c < 0) {
00670           return 0xFFFF;
00671         }
00672         if ((*query) != (u8_t)c) {
00673           return 0xFFFF;
00674         }
00675         ++response_offset;
00676         ++query;
00677         --n;
00678       }
00679       ++query;
00680     }
00681     n = pbuf_try_get_at(p, response_offset);
00682     if (n < 0) {
00683       return 0xFFFF;
00684     }
00685   } while (n != 0);
00686 
00687   return response_offset + 1;
00688 }
00689 
00690 /**
00691  * Walk through a compact encoded DNS name and return the end of the name.
00692  *
00693  * @param p pbuf containing the name
00694  * @param query_idx start index into p pointing to encoded DNS name in the DNS server response
00695  * @return index to end of the name
00696  */
00697 static u16_t
00698 dns_skip_name(struct pbuf* p, u16_t query_idx)
00699 {
00700   int n;
00701   u16_t offset = query_idx;
00702 
00703   do {
00704     n = pbuf_try_get_at(p, offset++);
00705     if (n < 0) {
00706       return 0xFFFF;
00707     }
00708     /** @see RFC 1035 - 4.1.4. Message compression */
00709     if ((n & 0xc0) == 0xc0) {
00710       /* Compressed name: since we only want to skip it (not check it), stop here */
00711       break;
00712     } else {
00713       /* Not compressed name */
00714       if (offset + n >= p->tot_len) {
00715         return 0xFFFF;
00716       }
00717       offset = (u16_t)(offset + n);
00718     }
00719     n = pbuf_try_get_at(p, offset);
00720     if (n < 0) {
00721       return 0xFFFF;
00722     }
00723   } while (n != 0);
00724 
00725   return offset + 1;
00726 }
00727 
00728 /**
00729  * Send a DNS query packet.
00730  *
00731  * @param idx the DNS table entry index for which to send a request
00732  * @return ERR_OK if packet is sent; an err_t indicating the problem otherwise
00733  */
00734 static err_t
00735 dns_send(u8_t idx)
00736 {
00737   err_t err;
00738   struct dns_hdr hdr;
00739   struct dns_query qry;
00740   struct pbuf *p;
00741   u16_t query_idx, copy_len;
00742   const char *hostname, *hostname_part;
00743   u8_t n;
00744   u8_t pcb_idx;
00745   struct dns_table_entry* entry = &dns_table[idx];
00746 
00747   LWIP_DEBUGF(DNS_DEBUG, ("dns_send: dns_servers[%"U16_F"] \"%s\": request\n",
00748               (u16_t)(entry->server_idx), entry->name));
00749   LWIP_ASSERT("dns server out of array", entry->server_idx < DNS_MAX_SERVERS);
00750   if (ip_addr_isany_val(dns_servers[entry->server_idx])
00751 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
00752       && !entry->is_mdns
00753 #endif
00754     ) {
00755     /* DNS server not valid anymore, e.g. PPP netif has been shut down */
00756     /* call specified callback function if provided */
00757     dns_call_found(idx, NULL);
00758     /* flush this entry */
00759     entry->state = DNS_STATE_UNUSED;
00760     return ERR_OK;
00761   }
00762 
00763   /* if here, we have either a new query or a retry on a previous query to process */
00764   p = pbuf_alloc(PBUF_TRANSPORT, (u16_t)(SIZEOF_DNS_HDR + strlen(entry->name) + 2 +
00765                  SIZEOF_DNS_QUERY), PBUF_RAM);
00766   if (p != NULL) {
00767     const ip_addr_t* dst;
00768     u16_t dst_port;
00769     /* fill dns header */
00770     memset(&hdr, 0, SIZEOF_DNS_HDR);
00771     hdr.id = lwip_htons(entry->txid);
00772     hdr.flags1 = DNS_FLAG1_RD;
00773     hdr.numquestions = PP_HTONS(1);
00774     pbuf_take(p, &hdr, SIZEOF_DNS_HDR);
00775     hostname = entry->name;
00776     --hostname;
00777 
00778     /* convert hostname into suitable query format. */
00779     query_idx = SIZEOF_DNS_HDR;
00780     do {
00781       ++hostname;
00782       hostname_part = hostname;
00783       for (n = 0; *hostname != '.' && *hostname != 0; ++hostname) {
00784         ++n;
00785       }
00786       copy_len = (u16_t)(hostname - hostname_part);
00787       pbuf_put_at(p, query_idx, n);
00788       pbuf_take_at(p, hostname_part, copy_len, query_idx + 1);
00789       query_idx += n + 1;
00790     } while (*hostname != 0);
00791     pbuf_put_at(p, query_idx, 0);
00792     query_idx++;
00793 
00794     /* fill dns query */
00795     if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype)) {
00796       qry.type = PP_HTONS(DNS_RRTYPE_AAAA);
00797     } else {
00798       qry.type = PP_HTONS(DNS_RRTYPE_A);
00799     }
00800     qry.cls = PP_HTONS(DNS_RRCLASS_IN);
00801     pbuf_take_at(p, &qry, SIZEOF_DNS_QUERY, query_idx);
00802 
00803 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00804     pcb_idx = entry->pcb_idx;
00805 #else
00806     pcb_idx = 0;
00807 #endif
00808     /* send dns packet */
00809     LWIP_DEBUGF(DNS_DEBUG, ("sending DNS request ID %d for name \"%s\" to server %d\r\n",
00810       entry->txid, entry->name, entry->server_idx));
00811 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
00812     if (entry->is_mdns) {
00813       dst_port = DNS_MQUERY_PORT;
00814 #if LWIP_IPV6
00815       if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype))
00816       {
00817         dst = &dns_mquery_v6group;
00818       }
00819 #endif
00820 #if LWIP_IPV4 && LWIP_IPV6
00821       else
00822 #endif
00823 #if LWIP_IPV4
00824       {
00825         dst = &dns_mquery_v4group;
00826       }
00827 #endif
00828     } else
00829 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
00830     {
00831       dst_port = DNS_SERVER_PORT;
00832       dst = &dns_servers[entry->server_idx];
00833     }
00834     err = udp_sendto(dns_pcbs[pcb_idx], p, dst, dst_port);
00835 
00836     /* free pbuf */
00837     pbuf_free(p);
00838   } else {
00839     err = ERR_MEM;
00840   }
00841 
00842   return err;
00843 }
00844 
00845 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00846 static struct udp_pcb*
00847 dns_alloc_random_port(void)
00848 {
00849   err_t err;
00850   struct udp_pcb* ret;
00851 
00852   ret = udp_new_ip_type(IPADDR_TYPE_ANY);
00853   if (ret == NULL) {
00854     /* out of memory, have to reuse an existing pcb */
00855     return NULL;
00856   }
00857   do {
00858     u16_t port = (u16_t)DNS_RAND_TXID();
00859     if (!DNS_PORT_ALLOWED(port)) {
00860       /* this port is not allowed, try again */
00861       err = ERR_USE;
00862       continue;
00863     }
00864     err = udp_bind(ret, IP_ANY_TYPE, port);
00865   } while (err == ERR_USE);
00866   if (err != ERR_OK) {
00867     udp_remove(ret);
00868     return NULL;
00869   }
00870   udp_recv(ret, dns_recv, NULL);
00871   return ret;
00872 }
00873 
00874 /**
00875  * dns_alloc_pcb() - allocates a new pcb (or reuses an existing one) to be used
00876  * for sending a request
00877  *
00878  * @return an index into dns_pcbs
00879  */
00880 static u8_t
00881 dns_alloc_pcb(void)
00882 {
00883   u8_t i;
00884   u8_t idx;
00885 
00886   for (i = 0; i < DNS_MAX_SOURCE_PORTS; i++) {
00887     if (dns_pcbs[i] == NULL) {
00888       break;
00889     }
00890   }
00891   if (i < DNS_MAX_SOURCE_PORTS) {
00892     dns_pcbs[i] = dns_alloc_random_port();
00893     if (dns_pcbs[i] != NULL) {
00894       /* succeeded */
00895       dns_last_pcb_idx = i;
00896       return i;
00897     }
00898   }
00899   /* if we come here, creating a new UDP pcb failed, so we have to use
00900      an already existing one */
00901   for (i = 0, idx = dns_last_pcb_idx + 1; i < DNS_MAX_SOURCE_PORTS; i++, idx++) {
00902     if (idx >= DNS_MAX_SOURCE_PORTS) {
00903       idx = 0;
00904     }
00905     if (dns_pcbs[idx] != NULL) {
00906       dns_last_pcb_idx = idx;
00907       return idx;
00908     }
00909   }
00910   return DNS_MAX_SOURCE_PORTS;
00911 }
00912 #endif /* ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0) */
00913 
00914 /**
00915  * dns_call_found() - call the found callback and check if there are duplicate
00916  * entries for the given hostname. If there are any, their found callback will
00917  * be called and they will be removed.
00918  *
00919  * @param idx dns table index of the entry that is resolved or removed
00920  * @param addr IP address for the hostname (or NULL on error or memory shortage)
00921  */
00922 static void
00923 dns_call_found(u8_t idx, ip_addr_t* addr)
00924 {
00925 #if ((LWIP_DNS_SECURE & (LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING | LWIP_DNS_SECURE_RAND_SRC_PORT)) != 0)
00926   u8_t i;
00927 #endif
00928 
00929 #if LWIP_IPV4 && LWIP_IPV6
00930   if (addr != NULL) {
00931     /* check that address type matches the request and adapt the table entry */
00932     if (IP_IS_V6_VAL(*addr)) {
00933       LWIP_ASSERT("invalid response", LWIP_DNS_ADDRTYPE_IS_IPV6(dns_table[idx].reqaddrtype));
00934       dns_table[idx].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV6;
00935     } else {
00936       LWIP_ASSERT("invalid response", !LWIP_DNS_ADDRTYPE_IS_IPV6(dns_table[idx].reqaddrtype));
00937       dns_table[idx].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV4;
00938     }
00939   }
00940 #endif /* LWIP_IPV4 && LWIP_IPV6 */
00941 
00942 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
00943   for (i = 0; i < DNS_MAX_REQUESTS; i++) {
00944     if (dns_requests[i].found && (dns_requests[i].dns_table_idx == idx)) {
00945       (*dns_requests[i].found)(dns_table[idx].name, addr, dns_requests[i].arg);
00946       /* flush this entry */
00947       dns_requests[i].found = NULL;
00948     }
00949   }
00950 #else
00951   if (dns_requests[idx].found) {
00952     (*dns_requests[idx].found)(dns_table[idx].name, addr, dns_requests[idx].arg);
00953   }
00954   dns_requests[idx].found = NULL;
00955 #endif
00956 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00957   /* close the pcb used unless other request are using it */
00958   for (i = 0; i < DNS_MAX_REQUESTS; i++) {
00959     if (i == idx) {
00960       continue; /* only check other requests */
00961     }
00962     if (dns_table[i].state == DNS_STATE_ASKING) {
00963       if (dns_table[i].pcb_idx == dns_table[idx].pcb_idx) {
00964         /* another request is still using the same pcb */
00965         dns_table[idx].pcb_idx = DNS_MAX_SOURCE_PORTS;
00966         break;
00967       }
00968     }
00969   }
00970   if (dns_table[idx].pcb_idx < DNS_MAX_SOURCE_PORTS) {
00971     /* if we come here, the pcb is not used any more and can be removed */
00972     udp_remove(dns_pcbs[dns_table[idx].pcb_idx]);
00973     dns_pcbs[dns_table[idx].pcb_idx] = NULL;
00974     dns_table[idx].pcb_idx = DNS_MAX_SOURCE_PORTS;
00975   }
00976 #endif
00977 }
00978 
00979 /* Create a query transmission ID that is unique for all outstanding queries */
00980 static u16_t
00981 dns_create_txid(void)
00982 {
00983   u16_t txid;
00984   u8_t i;
00985 
00986 again:
00987   txid = (u16_t)DNS_RAND_TXID();
00988 
00989   /* check whether the ID is unique */
00990   for (i = 0; i < DNS_TABLE_SIZE; i++) {
00991     if ((dns_table[i].state == DNS_STATE_ASKING) &&
00992         (dns_table[i].txid == txid)) {
00993       /* ID already used by another pending query */
00994       goto again;
00995     }
00996   }
00997 
00998   return txid;
00999 }
01000 
01001 /**
01002  * dns_check_entry() - see if entry has not yet been queried and, if so, sends out a query.
01003  * Check an entry in the dns_table:
01004  * - send out query for new entries
01005  * - retry old pending entries on timeout (also with different servers)
01006  * - remove completed entries from the table if their TTL has expired
01007  *
01008  * @param i index of the dns_table entry to check
01009  */
01010 static void
01011 dns_check_entry(u8_t i)
01012 {
01013   err_t err;
01014   struct dns_table_entry *entry = &dns_table[i];
01015 
01016   LWIP_ASSERT("array index out of bounds", i < DNS_TABLE_SIZE);
01017 
01018   switch (entry->state) {
01019     case DNS_STATE_NEW:
01020       /* initialize new entry */
01021       entry->txid = dns_create_txid();
01022       entry->state = DNS_STATE_ASKING;
01023       entry->server_idx = 0;
01024       entry->tmr = 1;
01025       entry->retries = 0;
01026 
01027       /* send DNS packet for this entry */
01028       err = dns_send(i);
01029       if (err != ERR_OK) {
01030         LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
01031                     ("dns_send returned error: %s\n", lwip_strerr(err)));
01032       }
01033       break;
01034     case DNS_STATE_ASKING:
01035       if (--entry->tmr == 0) {
01036         if (++entry->retries == DNS_MAX_RETRIES) {
01037           if ((entry->server_idx + 1 < DNS_MAX_SERVERS) && !ip_addr_isany_val(dns_servers[entry->server_idx + 1])
01038 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01039             && !entry->is_mdns
01040 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
01041             ) {
01042             /* change of server */
01043             entry->server_idx++;
01044             entry->tmr = 1;
01045             entry->retries = 0;
01046           } else {
01047             LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": timeout\n", entry->name));
01048             /* call specified callback function if provided */
01049             dns_call_found(i, NULL);
01050             /* flush this entry */
01051             entry->state = DNS_STATE_UNUSED;
01052             break;
01053           }
01054         } else {
01055           /* wait longer for the next retry */
01056           entry->tmr = entry->retries;
01057         }
01058 
01059         /* send DNS packet for this entry */
01060         err = dns_send(i);
01061         if (err != ERR_OK) {
01062           LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
01063                       ("dns_send returned error: %s\n", lwip_strerr(err)));
01064         }
01065       }
01066       break;
01067     case DNS_STATE_DONE:
01068       /* if the time to live is nul */
01069       if ((entry->ttl == 0) || (--entry->ttl == 0)) {
01070         LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": flush\n", entry->name));
01071         /* flush this entry, there cannot be any related pending entries in this state */
01072         entry->state = DNS_STATE_UNUSED;
01073       }
01074       break;
01075     case DNS_STATE_UNUSED:
01076       /* nothing to do */
01077       break;
01078     default:
01079       LWIP_ASSERT("unknown dns_table entry state:", 0);
01080       break;
01081   }
01082 }
01083 
01084 /**
01085  * Call dns_check_entry for each entry in dns_table - check all entries.
01086  */
01087 static void
01088 dns_check_entries(void)
01089 {
01090   u8_t i;
01091 
01092   for (i = 0; i < DNS_TABLE_SIZE; ++i) {
01093     dns_check_entry(i);
01094   }
01095 }
01096 
01097 /**
01098  * Save TTL and call dns_call_found for correct response.
01099  */
01100 static void
01101 dns_correct_response(u8_t idx, u32_t ttl)
01102 {
01103   struct dns_table_entry *entry = &dns_table[idx];
01104 
01105   entry->state = DNS_STATE_DONE;
01106 
01107   LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", entry->name));
01108   ip_addr_debug_print(DNS_DEBUG, (&(entry->ipaddr)));
01109   LWIP_DEBUGF(DNS_DEBUG, ("\n"));
01110 
01111   /* read the answer resource record's TTL, and maximize it if needed */
01112   entry->ttl = ttl;
01113   if (entry->ttl > DNS_MAX_TTL) {
01114     entry->ttl = DNS_MAX_TTL;
01115   }
01116   dns_call_found(idx, &entry->ipaddr);
01117 
01118   if (entry->ttl == 0) {
01119     /* RFC 883, page 29: "Zero values are
01120        interpreted to mean that the RR can only be used for the
01121        transaction in progress, and should not be cached."
01122        -> flush this entry now */
01123     /* entry reused during callback? */
01124     if (entry->state == DNS_STATE_DONE) {
01125       entry->state = DNS_STATE_UNUSED;
01126     }
01127   }
01128 }
01129 /**
01130  * Receive input function for DNS response packets arriving for the dns UDP pcb.
01131  */
01132 static void
01133 dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
01134 {
01135   u8_t i;
01136   u16_t txid;
01137   u16_t res_idx;
01138   struct dns_hdr hdr;
01139   struct dns_answer ans;
01140   struct dns_query qry;
01141   u16_t nquestions, nanswers;
01142 
01143   LWIP_UNUSED_ARG(arg);
01144   LWIP_UNUSED_ARG(pcb);
01145   LWIP_UNUSED_ARG(port);
01146 
01147   /* is the dns message big enough ? */
01148   if (p->tot_len < (SIZEOF_DNS_HDR + SIZEOF_DNS_QUERY)) {
01149     LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too small\n"));
01150     /* free pbuf and return */
01151     goto memerr;
01152   }
01153 
01154   /* copy dns payload inside static buffer for processing */
01155   if (pbuf_copy_partial(p, &hdr, SIZEOF_DNS_HDR, 0) == SIZEOF_DNS_HDR) {
01156     /* Match the ID in the DNS header with the name table. */
01157     txid = lwip_htons(hdr.id);
01158     for (i = 0; i < DNS_TABLE_SIZE; i++) {
01159       const struct dns_table_entry *entry = &dns_table[i];
01160       if ((entry->state == DNS_STATE_ASKING) &&
01161           (entry->txid == txid)) {
01162 
01163         /* We only care about the question(s) and the answers. The authrr
01164            and the extrarr are simply discarded. */
01165         nquestions = lwip_htons(hdr.numquestions);
01166         nanswers   = lwip_htons(hdr.numanswers);
01167 
01168         /* Check for correct response. */
01169         if ((hdr.flags1 & DNS_FLAG1_RESPONSE) == 0) {
01170           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": not a response\n", entry->name));
01171           goto memerr; /* ignore this packet */
01172         }
01173         if (nquestions != 1) {
01174           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
01175           goto memerr; /* ignore this packet */
01176         }
01177 
01178 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01179         if (!entry->is_mdns)
01180 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
01181         {
01182           /* Check whether response comes from the same network address to which the
01183              question was sent. (RFC 5452) */
01184           if (!ip_addr_cmp(addr, &dns_servers[entry->server_idx])) {
01185             goto memerr; /* ignore this packet */
01186           }
01187         }
01188 
01189         /* Check if the name in the "question" part match with the name in the entry and
01190            skip it if equal. */
01191         res_idx = dns_compare_name(entry->name, p, SIZEOF_DNS_HDR);
01192         if (res_idx == 0xFFFF) {
01193           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
01194           goto memerr; /* ignore this packet */
01195         }
01196 
01197         /* check if "question" part matches the request */
01198         if (pbuf_copy_partial(p, &qry, SIZEOF_DNS_QUERY, res_idx) != SIZEOF_DNS_QUERY) {
01199           goto memerr; /* ignore this packet */
01200         }
01201         if ((qry.cls != PP_HTONS(DNS_RRCLASS_IN)) ||
01202           (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype) && (qry.type != PP_HTONS(DNS_RRTYPE_AAAA))) ||
01203           (!LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype) && (qry.type != PP_HTONS(DNS_RRTYPE_A)))) {
01204           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
01205           goto memerr; /* ignore this packet */
01206         }
01207         /* skip the rest of the "question" part */
01208         res_idx += SIZEOF_DNS_QUERY;
01209 
01210         /* Check for error. If so, call callback to inform. */
01211         if (hdr.flags2 & DNS_FLAG2_ERR_MASK) {
01212           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", entry->name));
01213         } else {
01214           while ((nanswers > 0) && (res_idx < p->tot_len)) {
01215             /* skip answer resource record's host name */
01216             res_idx = dns_skip_name(p, res_idx);
01217             if (res_idx == 0xFFFF) {
01218               goto memerr; /* ignore this packet */
01219             }
01220 
01221             /* Check for IP address type and Internet class. Others are discarded. */
01222             if (pbuf_copy_partial(p, &ans, SIZEOF_DNS_ANSWER, res_idx) != SIZEOF_DNS_ANSWER) {
01223               goto memerr; /* ignore this packet */
01224             }
01225             res_idx += SIZEOF_DNS_ANSWER;
01226 
01227             if (ans.cls == PP_HTONS(DNS_RRCLASS_IN)) {
01228 #if LWIP_IPV4
01229               if ((ans.type == PP_HTONS(DNS_RRTYPE_A)) && (ans.len == PP_HTONS(sizeof(ip4_addr_t)))) {
01230 #if LWIP_IPV4 && LWIP_IPV6
01231                 if (!LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype))
01232 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01233                 {
01234                   ip4_addr_t ip4addr;
01235                   /* read the IP address after answer resource record's header */
01236                   if (pbuf_copy_partial(p, &ip4addr, sizeof(ip4_addr_t), res_idx) != sizeof(ip4_addr_t)) {
01237                     goto memerr; /* ignore this packet */
01238                   }
01239                   ip_addr_copy_from_ip4(dns_table[i].ipaddr, ip4addr);
01240                   pbuf_free(p);
01241                   /* handle correct response */
01242                   dns_correct_response(i, lwip_ntohl(ans.ttl));
01243                   return;
01244                 }
01245               }
01246 #endif /* LWIP_IPV4 */
01247 #if LWIP_IPV6
01248               if ((ans.type == PP_HTONS(DNS_RRTYPE_AAAA)) && (ans.len == PP_HTONS(sizeof(ip6_addr_t)))) {
01249 #if LWIP_IPV4 && LWIP_IPV6
01250                 if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype))
01251 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01252                 {
01253                   ip6_addr_t ip6addr;
01254                   /* read the IP address after answer resource record's header */
01255                   if (pbuf_copy_partial(p, &ip6addr, sizeof(ip6_addr_t), res_idx) != sizeof(ip6_addr_t)) {
01256                     goto memerr; /* ignore this packet */
01257                   }
01258                   ip_addr_copy_from_ip6(dns_table[i].ipaddr, ip6addr);
01259                   pbuf_free(p);
01260                   /* handle correct response */
01261                   dns_correct_response(i, lwip_ntohl(ans.ttl));
01262                   return;
01263                 }
01264               }
01265 #endif /* LWIP_IPV6 */
01266             }
01267             /* skip this answer */
01268             if ((int)(res_idx + lwip_htons(ans.len)) > 0xFFFF) {
01269               goto memerr; /* ignore this packet */
01270             }
01271             res_idx += lwip_htons(ans.len);
01272             --nanswers;
01273           }
01274 #if LWIP_IPV4 && LWIP_IPV6
01275           if ((entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) ||
01276               (entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV6_IPV4)) {
01277             if (entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) {
01278               /* IPv4 failed, try IPv6 */
01279               dns_table[i].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV6;
01280             } else {
01281               /* IPv6 failed, try IPv4 */
01282               dns_table[i].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV4;
01283             }
01284             pbuf_free(p);
01285             dns_table[i].state = DNS_STATE_NEW;
01286             dns_check_entry(i);
01287             return;
01288           }
01289 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01290           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in response\n", entry->name));
01291         }
01292         /* call callback to indicate error, clean up memory and return */
01293         pbuf_free(p);
01294         dns_call_found(i, NULL);
01295         dns_table[i].state = DNS_STATE_UNUSED;
01296         return;
01297       }
01298     }
01299   }
01300 
01301 memerr:
01302   /* deallocate memory and return */
01303   pbuf_free(p);
01304   return;
01305 }
01306 
01307 /**
01308  * Queues a new hostname to resolve and sends out a DNS query for that hostname
01309  *
01310  * @param name the hostname that is to be queried
01311  * @param hostnamelen length of the hostname
01312  * @param found a callback function to be called on success, failure or timeout
01313  * @param callback_arg argument to pass to the callback function
01314  * @return err_t return code.
01315  */
01316 static err_t
01317 dns_enqueue(const char *name, size_t hostnamelen, dns_found_callback found,
01318             void *callback_arg LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype) LWIP_DNS_ISMDNS_ARG(u8_t is_mdns))
01319 {
01320   u8_t i;
01321   u8_t lseq, lseqi;
01322   struct dns_table_entry *entry = NULL;
01323   size_t namelen;
01324   struct dns_req_entry* req;
01325 
01326 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
01327   u8_t r;
01328   /* check for duplicate entries */
01329   for (i = 0; i < DNS_TABLE_SIZE; i++) {
01330     if ((dns_table[i].state == DNS_STATE_ASKING) &&
01331         (lwip_strnicmp(name, dns_table[i].name, sizeof(dns_table[i].name)) == 0)) {
01332 #if LWIP_IPV4 && LWIP_IPV6
01333       if (dns_table[i].reqaddrtype != dns_addrtype) {
01334         /* requested address types don't match
01335            this can lead to 2 concurrent requests, but mixing the address types
01336            for the same host should not be that common */
01337         continue;
01338       }
01339 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01340       /* this is a duplicate entry, find a free request entry */
01341       for (r = 0; r < DNS_MAX_REQUESTS; r++) {
01342         if (dns_requests[r].found == 0) {
01343           dns_requests[r].found = found;
01344           dns_requests[r].arg = callback_arg;
01345           dns_requests[r].dns_table_idx = i;
01346           LWIP_DNS_SET_ADDRTYPE(dns_requests[r].reqaddrtype, dns_addrtype);
01347           LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": duplicate request\n", name));
01348           return ERR_INPROGRESS;
01349         }
01350       }
01351     }
01352   }
01353   /* no duplicate entries found */
01354 #endif
01355 
01356   /* search an unused entry, or the oldest one */
01357   lseq = 0;
01358   lseqi = DNS_TABLE_SIZE;
01359   for (i = 0; i < DNS_TABLE_SIZE; ++i) {
01360     entry = &dns_table[i];
01361     /* is it an unused entry ? */
01362     if (entry->state == DNS_STATE_UNUSED) {
01363       break;
01364     }
01365     /* check if this is the oldest completed entry */
01366     if (entry->state == DNS_STATE_DONE) {
01367       u8_t age = dns_seqno - entry->seqno;
01368       if (age > lseq) {
01369         lseq = age;
01370         lseqi = i;
01371       }
01372     }
01373   }
01374 
01375   /* if we don't have found an unused entry, use the oldest completed one */
01376   if (i == DNS_TABLE_SIZE) {
01377     if ((lseqi >= DNS_TABLE_SIZE) || (dns_table[lseqi].state != DNS_STATE_DONE)) {
01378       /* no entry can be used now, table is full */
01379       LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS entries table is full\n", name));
01380       return ERR_MEM;
01381     } else {
01382       /* use the oldest completed one */
01383       i = lseqi;
01384       entry = &dns_table[i];
01385     }
01386   }
01387 
01388 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
01389   /* find a free request entry */
01390   req = NULL;
01391   for (r = 0; r < DNS_MAX_REQUESTS; r++) {
01392     if (dns_requests[r].found == NULL) {
01393       req = &dns_requests[r];
01394       break;
01395     }
01396   }
01397   if (req == NULL) {
01398     /* no request entry can be used now, table is full */
01399     LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS request entries table is full\n", name));
01400     return ERR_MEM;
01401   }
01402   req->dns_table_idx = i;
01403 #else
01404   /* in this configuration, the entry index is the same as the request index */
01405   req = &dns_requests[i];
01406 #endif
01407 
01408   /* use this entry */
01409   LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS entry %"U16_F"\n", name, (u16_t)(i)));
01410 
01411   /* fill the entry */
01412   entry->state = DNS_STATE_NEW;
01413   entry->seqno = dns_seqno;
01414   LWIP_DNS_SET_ADDRTYPE(entry->reqaddrtype, dns_addrtype);
01415   LWIP_DNS_SET_ADDRTYPE(req->reqaddrtype, dns_addrtype);
01416   req->found = found;
01417   req->arg   = callback_arg;
01418   namelen = LWIP_MIN(hostnamelen, DNS_MAX_NAME_LENGTH-1);
01419   MEMCPY(entry->name, name, namelen);
01420   entry->name[namelen] = 0;
01421 
01422 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
01423   entry->pcb_idx = dns_alloc_pcb();
01424   if (entry->pcb_idx >= DNS_MAX_SOURCE_PORTS) {
01425     /* failed to get a UDP pcb */
01426     LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": failed to allocate a pcb\n", name));
01427     entry->state = DNS_STATE_UNUSED;
01428     req->found = NULL;
01429     return ERR_MEM;
01430   }
01431   LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS pcb %"U16_F"\n", name, (u16_t)(entry->pcb_idx)));
01432 #endif
01433 
01434 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01435   entry->is_mdns = is_mdns;
01436 #endif
01437 
01438   dns_seqno++;
01439 
01440   /* force to send query without waiting timer */
01441   dns_check_entry(i);
01442 
01443   /* dns query is enqueued */
01444   return ERR_INPROGRESS;
01445 }
01446 
01447 /**
01448  * @ingroup dns
01449  * Resolve a hostname (string) into an IP address.
01450  * NON-BLOCKING callback version for use with raw API!!!
01451  *
01452  * Returns immediately with one of err_t return codes:
01453  * - ERR_OK if hostname is a valid IP address string or the host
01454  *   name is already in the local names table.
01455  * - ERR_INPROGRESS enqueue a request to be sent to the DNS server
01456  *   for resolution if no errors are present.
01457  * - ERR_ARG: dns client not initialized or invalid hostname
01458  *
01459  * @param hostname the hostname that is to be queried
01460  * @param addr pointer to a ip_addr_t where to store the address if it is already
01461  *             cached in the dns_table (only valid if ERR_OK is returned!)
01462  * @param found a callback function to be called on success, failure or timeout (only if
01463  *              ERR_INPROGRESS is returned!)
01464  * @param callback_arg argument to pass to the callback function
01465  * @return a err_t return code.
01466  */
01467 err_t
01468 dns_gethostbyname(const char *hostname, ip_addr_t *addr, dns_found_callback found,
01469                   void *callback_arg)
01470 {
01471   return dns_gethostbyname_addrtype(hostname, addr, found, callback_arg, LWIP_DNS_ADDRTYPE_DEFAULT);
01472 }
01473 
01474 /**
01475  * @ingroup dns
01476  * Like dns_gethostbyname, but returned address type can be controlled:
01477  * @param hostname the hostname that is to be queried
01478  * @param addr pointer to a ip_addr_t where to store the address if it is already
01479  *             cached in the dns_table (only valid if ERR_OK is returned!)
01480  * @param found a callback function to be called on success, failure or timeout (only if
01481  *              ERR_INPROGRESS is returned!)
01482  * @param callback_arg argument to pass to the callback function
01483  * @param dns_addrtype - LWIP_DNS_ADDRTYPE_IPV4_IPV6: try to resolve IPv4 first, try IPv6 if IPv4 fails only
01484  *                     - LWIP_DNS_ADDRTYPE_IPV6_IPV4: try to resolve IPv6 first, try IPv4 if IPv6 fails only
01485  *                     - LWIP_DNS_ADDRTYPE_IPV4: try to resolve IPv4 only
01486  *                     - LWIP_DNS_ADDRTYPE_IPV6: try to resolve IPv6 only
01487  */
01488 err_t
01489 dns_gethostbyname_addrtype(const char *hostname, ip_addr_t *addr, dns_found_callback found,
01490                            void *callback_arg, u8_t dns_addrtype)
01491 {
01492   size_t hostnamelen;
01493 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01494   u8_t is_mdns;
01495 #endif
01496   /* not initialized or no valid server yet, or invalid addr pointer
01497    * or invalid hostname or invalid hostname length */
01498   if ((addr == NULL) ||
01499       (!hostname) || (!hostname[0])) {
01500     return ERR_ARG;
01501   }
01502 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) == 0)
01503   if (dns_pcbs[0] == NULL) {
01504     return ERR_ARG;
01505   }
01506 #endif
01507   hostnamelen = strlen(hostname);
01508   if (hostnamelen >= DNS_MAX_NAME_LENGTH) {
01509     LWIP_DEBUGF(DNS_DEBUG, ("dns_gethostbyname: name too long to resolve"));
01510     return ERR_ARG;
01511   }
01512 
01513 
01514 #if LWIP_HAVE_LOOPIF
01515   if (strcmp(hostname, "localhost") == 0) {
01516     ip_addr_set_loopback(LWIP_DNS_ADDRTYPE_IS_IPV6(dns_addrtype), addr);
01517     return ERR_OK;
01518   }
01519 #endif /* LWIP_HAVE_LOOPIF */
01520 
01521   /* host name already in octet notation? set ip addr and return ERR_OK */
01522   if (ipaddr_aton(hostname, addr)) {
01523 #if LWIP_IPV4 && LWIP_IPV6
01524     if ((IP_IS_V6(addr) && (dns_addrtype != LWIP_DNS_ADDRTYPE_IPV4)) ||
01525         (IP_IS_V4(addr) && (dns_addrtype != LWIP_DNS_ADDRTYPE_IPV6)))
01526 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01527     {
01528       return ERR_OK;
01529     }
01530   }
01531   /* already have this address cached? */
01532   if (dns_lookup(hostname, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)) == ERR_OK) {
01533     return ERR_OK;
01534   }
01535 #if LWIP_IPV4 && LWIP_IPV6
01536   if ((dns_addrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) || (dns_addrtype == LWIP_DNS_ADDRTYPE_IPV6_IPV4)) {
01537     /* fallback to 2nd IP type and try again to lookup */
01538     u8_t fallback;
01539     if (dns_addrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) {
01540       fallback = LWIP_DNS_ADDRTYPE_IPV6;
01541     } else {
01542       fallback = LWIP_DNS_ADDRTYPE_IPV4;
01543     }
01544     if (dns_lookup(hostname, addr LWIP_DNS_ADDRTYPE_ARG(fallback)) == ERR_OK) {
01545       return ERR_OK;
01546     }
01547   }
01548 #else /* LWIP_IPV4 && LWIP_IPV6 */
01549   LWIP_UNUSED_ARG(dns_addrtype);
01550 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01551 
01552 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01553   if (strstr(hostname, ".local") == &hostname[hostnamelen] - 6) {
01554     is_mdns = 1;
01555   } else {
01556     is_mdns = 0;
01557   }
01558 
01559   if (!is_mdns)
01560 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
01561   {
01562     /* prevent calling found callback if no server is set, return error instead */
01563     if (ip_addr_isany_val(dns_servers[0])) {
01564       return ERR_VAL;
01565     }
01566   }
01567 
01568   /* queue query with specified callback */
01569   return dns_enqueue(hostname, hostnamelen, found, callback_arg LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)
01570      LWIP_DNS_ISMDNS_ARG(is_mdns));
01571 }
01572 
01573 #endif /* LWIP_DNS */