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 DNS_MAX_SERVERS
00035  * @see LWIP_DHCP_MAX_DNS_SERVERS
00036  * @see @ref netconn_common for thread-safe access.
00037  */
00038 
00039 /*
00040  * Port to lwIP from uIP
00041  * by Jim Pettinato April 2007
00042  *
00043  * security fixes and more by Simon Goldschmidt
00044  *
00045  * uIP version Copyright (c) 2002-2003, Adam Dunkels.
00046  * All rights reserved.
00047  *
00048  * Redistribution and use in source and binary forms, with or without
00049  * modification, are permitted provided that the following conditions
00050  * are met:
00051  * 1. Redistributions of source code must retain the above copyright
00052  *    notice, this list of conditions and the following disclaimer.
00053  * 2. Redistributions in binary form must reproduce the above copyright
00054  *    notice, this list of conditions and the following disclaimer in the
00055  *    documentation and/or other materials provided with the distribution.
00056  * 3. The name of the author may not be used to endorse or promote
00057  *    products derived from this software without specific prior
00058  *    written permission.
00059  *
00060  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
00061  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
00062  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
00063  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
00064  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
00065  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
00066  * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
00067  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
00068  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
00069  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
00070  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00071  */
00072 
00073 /*-----------------------------------------------------------------------------
00074  * RFC 1035 - Domain names - implementation and specification
00075  * RFC 2181 - Clarifications to the DNS Specification
00076  *----------------------------------------------------------------------------*/
00077 
00078 /** @todo: define good default values (rfc compliance) */
00079 /** @todo: improve answer parsing, more checkings... */
00080 /** @todo: check RFC1035 - 7.3. Processing responses */
00081 /** @todo: one-shot mDNS: dual-stack fallback to another IP version */
00082 
00083 /*-----------------------------------------------------------------------------
00084  * Includes
00085  *----------------------------------------------------------------------------*/
00086 
00087 #include "lwip/opt.h"
00088 
00089 #if LWIP_DNS /* don't build if not configured for use in lwipopts.h */
00090 
00091 #include "lwip/def.h"
00092 #include "lwip/udp.h"
00093 #include "lwip/mem.h"
00094 #include "lwip/memp.h"
00095 #include "lwip/dns.h"
00096 #include "lwip/prot/dns.h"
00097 
00098 #include <string.h>
00099 
00100 /** Random generator function to create random TXIDs and source ports for queries */
00101 #ifndef DNS_RAND_TXID
00102 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_XID) != 0)
00103 #define DNS_RAND_TXID LWIP_RAND
00104 #else
00105 static u16_t dns_txid;
00106 #define DNS_RAND_TXID() (++dns_txid)
00107 #endif
00108 #endif
00109 
00110 /** Limits the source port to be >= 1024 by default */
00111 #ifndef DNS_PORT_ALLOWED
00112 #define DNS_PORT_ALLOWED(port) ((port) >= 1024)
00113 #endif
00114 
00115 /** DNS resource record max. TTL (one week as default) */
00116 #ifndef DNS_MAX_TTL
00117 #define DNS_MAX_TTL               604800
00118 #elif DNS_MAX_TTL > 0x7FFFFFFF
00119 #error DNS_MAX_TTL must be a positive 32-bit value
00120 #endif
00121 
00122 #if DNS_TABLE_SIZE > 255
00123 #error DNS_TABLE_SIZE must fit into an u8_t
00124 #endif
00125 #if DNS_MAX_SERVERS > 255
00126 #error DNS_MAX_SERVERS must fit into an u8_t
00127 #endif
00128 
00129 /* The number of parallel requests (i.e. calls to dns_gethostbyname
00130  * that cannot be answered from the DNS table.
00131  * This is set to the table size by default.
00132  */
00133 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
00134 #ifndef DNS_MAX_REQUESTS
00135 #define DNS_MAX_REQUESTS          DNS_TABLE_SIZE
00136 #else
00137 #if DNS_MAX_REQUESTS > 255
00138 #error DNS_MAX_REQUESTS must fit into an u8_t
00139 #endif
00140 #endif
00141 #else
00142 /* In this configuration, both arrays have to have the same size and are used
00143  * like one entry (used/free) */
00144 #define DNS_MAX_REQUESTS          DNS_TABLE_SIZE
00145 #endif
00146 
00147 /* The number of UDP source ports used in parallel */
00148 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00149 #ifndef DNS_MAX_SOURCE_PORTS
00150 #define DNS_MAX_SOURCE_PORTS      DNS_MAX_REQUESTS
00151 #else
00152 #if DNS_MAX_SOURCE_PORTS > 255
00153 #error DNS_MAX_SOURCE_PORTS must fit into an u8_t
00154 #endif
00155 #endif
00156 #else
00157 #ifdef DNS_MAX_SOURCE_PORTS
00158 #undef DNS_MAX_SOURCE_PORTS
00159 #endif
00160 #define DNS_MAX_SOURCE_PORTS      1
00161 #endif
00162 
00163 #if LWIP_IPV4 && LWIP_IPV6
00164 #define LWIP_DNS_ADDRTYPE_IS_IPV6(t) (((t) == LWIP_DNS_ADDRTYPE_IPV6_IPV4) || ((t) == LWIP_DNS_ADDRTYPE_IPV6))
00165 #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)))
00166 #define LWIP_DNS_ADDRTYPE_ARG(x) , x
00167 #define LWIP_DNS_ADDRTYPE_ARG_OR_ZERO(x) x
00168 #define LWIP_DNS_SET_ADDRTYPE(x, y) do { x = y; } while(0)
00169 #else
00170 #if LWIP_IPV6
00171 #define LWIP_DNS_ADDRTYPE_IS_IPV6(t) 1
00172 #else
00173 #define LWIP_DNS_ADDRTYPE_IS_IPV6(t) 0
00174 #endif
00175 #define LWIP_DNS_ADDRTYPE_MATCH_IP(t, ip) 1
00176 #define LWIP_DNS_ADDRTYPE_ARG(x)
00177 #define LWIP_DNS_ADDRTYPE_ARG_OR_ZERO(x) 0
00178 #define LWIP_DNS_SET_ADDRTYPE(x, y)
00179 #endif /* LWIP_IPV4 && LWIP_IPV6 */
00180 
00181 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
00182 #define LWIP_DNS_ISMDNS_ARG(x) , x
00183 #else
00184 #define LWIP_DNS_ISMDNS_ARG(x)
00185 #endif
00186 
00187 /** DNS query message structure.
00188     No packing needed: only used locally on the stack. */
00189 struct dns_query {
00190   /* DNS query record starts with either a domain name or a pointer
00191      to a name already present somewhere in the packet. */
00192   u16_t type;
00193   u16_t cls;
00194 };
00195 #define SIZEOF_DNS_QUERY 4
00196 
00197 /** DNS answer message structure.
00198     No packing needed: only used locally on the stack. */
00199 struct dns_answer {
00200   /* DNS answer record starts with either a domain name or a pointer
00201      to a name already present somewhere in the packet. */
00202   u16_t type;
00203   u16_t cls;
00204   u32_t ttl;
00205   u16_t len;
00206 };
00207 #define SIZEOF_DNS_ANSWER 10
00208 /* maximum allowed size for the struct due to non-packed */
00209 #define SIZEOF_DNS_ANSWER_ASSERT 12
00210 
00211 /* DNS table entry states */
00212 typedef enum {
00213   DNS_STATE_UNUSED           = 0,
00214   DNS_STATE_NEW              = 1,
00215   DNS_STATE_ASKING           = 2,
00216   DNS_STATE_DONE             = 3
00217 } dns_state_enum_t;
00218 
00219 /** DNS table entry */
00220 struct dns_table_entry {
00221   u32_t ttl;
00222   ip_addr_t ipaddr;
00223   u16_t txid;
00224   u8_t  state;
00225   u8_t  server_idx;
00226   u8_t  tmr;
00227   u8_t  retries;
00228   u8_t  seqno;
00229 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00230   u8_t pcb_idx;
00231 #endif
00232   char name[DNS_MAX_NAME_LENGTH];
00233 #if LWIP_IPV4 && LWIP_IPV6
00234   u8_t reqaddrtype;
00235 #endif /* LWIP_IPV4 && LWIP_IPV6 */
00236 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
00237   u8_t is_mdns;
00238 #endif
00239 };
00240 
00241 /** DNS request table entry: used when dns_gehostbyname cannot answer the
00242  * request from the DNS table */
00243 struct dns_req_entry {
00244   /* pointer to callback on DNS query done */
00245   dns_found_callback found;
00246   /* argument passed to the callback function */
00247   void *arg;
00248 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
00249   u8_t dns_table_idx;
00250 #endif
00251 #if LWIP_IPV4 && LWIP_IPV6
00252   u8_t reqaddrtype;
00253 #endif /* LWIP_IPV4 && LWIP_IPV6 */
00254 };
00255 
00256 #if DNS_LOCAL_HOSTLIST
00257 
00258 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
00259 /** Local host-list. For hostnames in this list, no
00260  *  external name resolution is performed */
00261 static struct local_hostlist_entry *local_hostlist_dynamic;
00262 #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00263 
00264 /** Defining this allows the local_hostlist_static to be placed in a different
00265  * linker section (e.g. FLASH) */
00266 #ifndef DNS_LOCAL_HOSTLIST_STORAGE_PRE
00267 #define DNS_LOCAL_HOSTLIST_STORAGE_PRE static
00268 #endif /* DNS_LOCAL_HOSTLIST_STORAGE_PRE */
00269 /** Defining this allows the local_hostlist_static to be placed in a different
00270  * linker section (e.g. FLASH) */
00271 #ifndef DNS_LOCAL_HOSTLIST_STORAGE_POST
00272 #define DNS_LOCAL_HOSTLIST_STORAGE_POST
00273 #endif /* DNS_LOCAL_HOSTLIST_STORAGE_POST */
00274 DNS_LOCAL_HOSTLIST_STORAGE_PRE struct local_hostlist_entry local_hostlist_static[]
00275   DNS_LOCAL_HOSTLIST_STORAGE_POST = DNS_LOCAL_HOSTLIST_INIT;
00276 
00277 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00278 
00279 static void dns_init_local(void);
00280 static err_t dns_lookup_local(const char *hostname, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype));
00281 #endif /* DNS_LOCAL_HOSTLIST */
00282 
00283 #if LWIP_FULL_DNS
00284 /* forward declarations */
00285 static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port);
00286 static void dns_check_entries(void);
00287 static void dns_call_found(u8_t idx, ip_addr_t* addr);
00288 #endif
00289 
00290 /*-----------------------------------------------------------------------------
00291  * Globals
00292  *----------------------------------------------------------------------------*/
00293 
00294 #if LWIP_FULL_DNS
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 #endif
00304 static ip_addr_t              dns_servers[DNS_MAX_SERVERS];
00305 struct dns_server_interface   *multihoming_dns_servers;
00306 
00307 #if LWIP_IPV4
00308 const ip_addr_t dns_mquery_v4group = DNS_MQUERY_IPV4_GROUP_INIT;
00309 #endif /* LWIP_IPV4 */
00310 #if LWIP_IPV6
00311 const ip_addr_t dns_mquery_v6group = DNS_MQUERY_IPV6_GROUP_INIT;
00312 #endif /* LWIP_IPV6 */
00313 
00314 /**
00315  * Initialize the resolver: set up the UDP pcb and configure the default server
00316  * (if DNS_SERVER_ADDRESS is set).
00317  */
00318 void
00319 dns_init(void)
00320 {
00321 #ifdef DNS_SERVER_ADDRESS
00322   /* initialize default DNS server address */
00323   ip_addr_t dnsserver;
00324   DNS_SERVER_ADDRESS(&dnsserver);
00325   dns_setserver(0, &dnsserver, NULL);
00326 #endif /* DNS_SERVER_ADDRESS */
00327 
00328 #if LWIP_FULL_DNS
00329   LWIP_ASSERT("sanity check SIZEOF_DNS_QUERY",
00330               sizeof(struct dns_query) == SIZEOF_DNS_QUERY);
00331   LWIP_ASSERT("sanity check SIZEOF_DNS_ANSWER",
00332               sizeof(struct dns_answer) <= SIZEOF_DNS_ANSWER_ASSERT);
00333 
00334   LWIP_DEBUGF(DNS_DEBUG, ("dns_init: initializing\n"));
00335 
00336   /* if dns client not yet initialized... */
00337 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) == 0)
00338   if (dns_pcbs[0] == NULL) {
00339     dns_pcbs[0] = udp_new_ip_type(IPADDR_TYPE_ANY);
00340     LWIP_ASSERT("dns_pcbs[0] != NULL", dns_pcbs[0] != NULL);
00341 
00342     /* initialize DNS table not needed (initialized to zero since it is a
00343      * global variable) */
00344     LWIP_ASSERT("For implicit initialization to work, DNS_STATE_UNUSED needs to be 0",
00345                 DNS_STATE_UNUSED == 0);
00346 
00347     /* initialize DNS client */
00348     udp_bind(dns_pcbs[0], IP_ANY_TYPE, 0);
00349     udp_recv(dns_pcbs[0], dns_recv, NULL);
00350   }
00351 #endif
00352 
00353 #if DNS_LOCAL_HOSTLIST
00354   dns_init_local();
00355 #endif
00356 #endif /* LWIP_FULL_DNS */
00357 }
00358 
00359 /**
00360  * @ingroup dns
00361  * Initialize one of the DNS servers.
00362  *
00363  * @param numdns the index of the DNS server to set must be < DNS_MAX_SERVERS
00364  * @param dnsserver IP address of the DNS server to set
00365  */
00366 void
00367 dns_setserver(u8_t numdns, const ip_addr_t *dnsserver, struct netif *netif)
00368 {
00369 
00370   if (netif == NULL ) {
00371     if (numdns < DNS_MAX_SERVERS) {
00372       if (dnsserver != NULL) {
00373         dns_servers[numdns] = (*dnsserver);
00374       } else {
00375         dns_servers[numdns] = *IP_ADDR_ANY;
00376       }
00377     }
00378   } else {
00379     char name[INTERFACE_NAME_MAX_SIZE];
00380     sprintf(name, "%c%c%d", netif->name[0], netif->name[1], netif->num);
00381     dns_add_interface_server(numdns, name, dnsserver);
00382   }
00383 }
00384 
00385 /**
00386  * @ingroup dns
00387  * Obtain one of the currently configured DNS server.
00388  *
00389  * @param numdns the index of the DNS server
00390  * @return IP address of the indexed DNS server or "ip_addr_any" if the DNS
00391  *         server has not been configured.
00392  */
00393 const ip_addr_t *
00394 dns_getserver(u8_t numdns, const char *interface_name)
00395 {
00396   if (numdns < DNS_MAX_SERVERS) {
00397     const ip_addr_t *dns_addr = dns_get_interface_server(numdns, interface_name);
00398     if (dns_addr != IP_ADDR_ANY) {
00399       return dns_addr;
00400     } else {
00401       return &dns_servers[numdns];
00402     }
00403   } else {
00404     return IP_ADDR_ANY;
00405   }
00406 }
00407 
00408 /**
00409  * @ingroup dns
00410  * Initialize one of the DNS servers.
00411  *
00412  * @param numdns the index of the DNS server to set must be < DNS_MAX_SERVERS
00413  * @param dnsserver IP address of the DNS server to set
00414  */
00415 void
00416 dns_add_interface_server(u8_t numdns, const char *interface_name, const ip_addr_t *dnsserver)
00417 {
00418   struct dns_server_interface *new_interface_server;
00419 
00420   if (numdns >= DNS_MAX_SERVERS) {
00421     return;
00422   }
00423 
00424   if (multihoming_dns_servers != NULL) {
00425     // if interface server already exists on the list just update it
00426     for (new_interface_server = multihoming_dns_servers; new_interface_server != NULL; new_interface_server = new_interface_server->next) {
00427       if (!strcmp(interface_name, new_interface_server->interface_name)) {
00428         new_interface_server->dns_servers[numdns] = (*dnsserver);
00429         return;
00430       }
00431     }
00432   }
00433   // add new dns server to the list tail
00434   new_interface_server = mem_malloc(sizeof(struct dns_server_interface));
00435   snprintf(new_interface_server->interface_name, INTERFACE_NAME_MAX_SIZE, "%s",interface_name);
00436   new_interface_server->dns_servers[numdns] = (*dnsserver);
00437   new_interface_server->next = NULL;
00438 
00439   if (multihoming_dns_servers == NULL) {
00440     multihoming_dns_servers = new_interface_server;
00441   } else {
00442     struct dns_server_interface *tail;
00443     tail = multihoming_dns_servers;
00444 
00445     while (tail->next != NULL) {
00446       tail = tail->next;
00447     }
00448     tail->next = new_interface_server;
00449 
00450   }
00451 }
00452 
00453 void
00454 dns_remove_interface_servers(const char *interface_name)
00455 {
00456   struct dns_server_interface *temp = multihoming_dns_servers;
00457   struct dns_server_interface *prev = NULL;
00458 
00459   if (temp != NULL && !strcmp(interface_name, temp->interface_name)) {
00460     multihoming_dns_servers = temp->next;
00461     mem_free(temp);
00462     return;
00463   }
00464 
00465   while (temp != NULL && strcmp(interface_name, temp->interface_name)) {
00466     prev = temp;
00467     temp = temp->next;
00468   }
00469 
00470   if (temp == NULL) {
00471     return;
00472   }
00473 
00474   prev->next = temp->next;
00475   mem_free(temp);
00476 }
00477 
00478 /**
00479  * @ingroup dns
00480  * Obtain one of the currently configured DNS server.
00481  *
00482  * @param numdns the index of the DNS server
00483  * @return IP address of the indexed DNS server or "ip_addr_any" if the DNS
00484  *         server has not been configured.
00485  */
00486 const ip_addr_t *
00487 dns_get_interface_server(u8_t numdns, const char *interface_name)
00488 {
00489   struct dns_server_interface *interface_server;
00490 
00491   if (numdns >= DNS_MAX_SERVERS) {
00492     return IP_ADDR_ANY;
00493   }
00494 
00495   for (interface_server = multihoming_dns_servers; interface_server != NULL; interface_server = interface_server->next) {
00496     if (!strcmp(interface_name, interface_server->interface_name)) {
00497       return &interface_server->dns_servers[numdns];
00498     }
00499   }
00500   return IP_ADDR_ANY;
00501 }
00502 
00503 /**
00504  * The DNS resolver client timer - handle retries and timeouts and should
00505  * be called every DNS_TMR_INTERVAL milliseconds (every second by default).
00506  */
00507 void
00508 dns_tmr(void)
00509 {
00510 #if LWIP_FULL_DNS
00511   LWIP_DEBUGF(DNS_DEBUG, ("dns_tmr: dns_check_entries\n"));
00512   dns_check_entries();
00513 #endif
00514 }
00515 
00516 #if LWIP_FULL_DNS
00517 
00518 #if DNS_LOCAL_HOSTLIST
00519 static void
00520 dns_init_local(void)
00521 {
00522 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT)
00523   size_t i;
00524   struct local_hostlist_entry *entry;
00525   /* Dynamic: copy entries from DNS_LOCAL_HOSTLIST_INIT to list */
00526   struct local_hostlist_entry local_hostlist_init[] = DNS_LOCAL_HOSTLIST_INIT;
00527   size_t namelen;
00528   for (i = 0; i < LWIP_ARRAYSIZE(local_hostlist_init); i++) {
00529     struct local_hostlist_entry *init_entry = &local_hostlist_init[i];
00530     LWIP_ASSERT("invalid host name (NULL)", init_entry->name != NULL);
00531     namelen = strlen(init_entry->name);
00532     LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN);
00533     entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST);
00534     LWIP_ASSERT("mem-error in dns_init_local", entry != NULL);
00535     if (entry != NULL) {
00536       char *entry_name = (char *)entry + sizeof(struct local_hostlist_entry);
00537       MEMCPY(entry_name, init_entry->name, namelen);
00538       entry_name[namelen] = 0;
00539       entry->name = entry_name;
00540       entry->addr = init_entry->addr;
00541       entry->next = local_hostlist_dynamic;
00542       local_hostlist_dynamic = entry;
00543     }
00544   }
00545 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT) */
00546 }
00547 
00548 /**
00549  * @ingroup dns
00550  * Iterate the local host-list for a hostname.
00551  *
00552  * @param iterator_fn a function that is called for every entry in the local host-list
00553  * @param iterator_arg 3rd argument passed to iterator_fn
00554  * @return the number of entries in the local host-list
00555  */
00556 size_t
00557 dns_local_iterate(dns_found_callback iterator_fn, void *iterator_arg)
00558 {
00559   size_t i;
00560 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
00561   struct local_hostlist_entry *entry = local_hostlist_dynamic;
00562   i = 0;
00563   while (entry != NULL) {
00564     if (iterator_fn != NULL) {
00565       iterator_fn(entry->name, &entry->addr, iterator_arg);
00566     }
00567     i++;
00568     entry = entry->next;
00569   }
00570 #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00571   for (i = 0; i < LWIP_ARRAYSIZE(local_hostlist_static); i++) {
00572     if (iterator_fn != NULL) {
00573       iterator_fn(local_hostlist_static[i].name, &local_hostlist_static[i].addr, iterator_arg);
00574     }
00575   }
00576 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00577   return i;
00578 }
00579 
00580 /**
00581  * @ingroup dns
00582  * Scans the local host-list for a hostname.
00583  *
00584  * @param hostname Hostname to look for in the local host-list
00585  * @param addr the first IP address for the hostname in the local host-list or
00586  *         IPADDR_NONE if not found.
00587  * @param dns_addrtype - LWIP_DNS_ADDRTYPE_IPV4_IPV6: try to resolve IPv4 (ATTENTION: no fallback here!)
00588  *                     - LWIP_DNS_ADDRTYPE_IPV6_IPV4: try to resolve IPv6 (ATTENTION: no fallback here!)
00589  *                     - LWIP_DNS_ADDRTYPE_IPV4: try to resolve IPv4 only
00590  *                     - LWIP_DNS_ADDRTYPE_IPV6: try to resolve IPv6 only
00591  * @return ERR_OK if found, ERR_ARG if not found
00592  */
00593 err_t
00594 dns_local_lookup(const char *hostname, ip_addr_t *addr, u8_t dns_addrtype)
00595 {
00596   LWIP_UNUSED_ARG(dns_addrtype);
00597   return dns_lookup_local(hostname, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype));
00598 }
00599 
00600 /* Internal implementation for dns_local_lookup and dns_lookup */
00601 static err_t
00602 dns_lookup_local(const char *hostname, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype))
00603 {
00604 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
00605   struct local_hostlist_entry *entry = local_hostlist_dynamic;
00606   while (entry != NULL) {
00607     if ((lwip_stricmp(entry->name, hostname) == 0) &&
00608         LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, entry->addr)) {
00609       if (addr) {
00610         ip_addr_copy(*addr, entry->addr);
00611       }
00612       return ERR_OK;
00613     }
00614     entry = entry->next;
00615   }
00616 #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00617   size_t i;
00618   for (i = 0; i < LWIP_ARRAYSIZE(local_hostlist_static); i++) {
00619     if ((lwip_stricmp(local_hostlist_static[i].name, hostname) == 0) &&
00620         LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, local_hostlist_static[i].addr)) {
00621       if (addr) {
00622         ip_addr_copy(*addr, local_hostlist_static[i].addr);
00623       }
00624       return ERR_OK;
00625     }
00626   }
00627 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */
00628   return ERR_ARG;
00629 }
00630 
00631 #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC
00632 /**
00633  * @ingroup dns
00634  * Remove all entries from the local host-list for a specific hostname
00635  * and/or IP address
00636  *
00637  * @param hostname hostname for which entries shall be removed from the local
00638  *                 host-list
00639  * @param addr address for which entries shall be removed from the local host-list
00640  * @return the number of removed entries
00641  */
00642 int
00643 dns_local_removehost(const char *hostname, const ip_addr_t *addr)
00644 {
00645   int removed = 0;
00646   struct local_hostlist_entry *entry = local_hostlist_dynamic;
00647   struct local_hostlist_entry *last_entry = NULL;
00648   while (entry != NULL) {
00649     if (((hostname == NULL) || !lwip_stricmp(entry->name, hostname)) &&
00650         ((addr == NULL) || ip_addr_cmp(&entry->addr, addr))) {
00651       struct local_hostlist_entry *free_entry;
00652       if (last_entry != NULL) {
00653         last_entry->next = entry->next;
00654       } else {
00655         local_hostlist_dynamic = entry->next;
00656       }
00657       free_entry = entry;
00658       entry = entry->next;
00659       memp_free(MEMP_LOCALHOSTLIST, free_entry);
00660       removed++;
00661     } else {
00662       last_entry = entry;
00663       entry = entry->next;
00664     }
00665   }
00666   return removed;
00667 }
00668 
00669 /**
00670  * @ingroup dns
00671  * Add a hostname/IP address pair to the local host-list.
00672  * Duplicates are not checked.
00673  *
00674  * @param hostname hostname of the new entry
00675  * @param addr IP address of the new entry
00676  * @return ERR_OK if succeeded or ERR_MEM on memory error
00677  */
00678 err_t
00679 dns_local_addhost(const char *hostname, const ip_addr_t *addr)
00680 {
00681   struct local_hostlist_entry *entry;
00682   size_t namelen;
00683   char *entry_name;
00684   LWIP_ASSERT("invalid host name (NULL)", hostname != NULL);
00685   namelen = strlen(hostname);
00686   LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN);
00687   entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST);
00688   if (entry == NULL) {
00689     return ERR_MEM;
00690   }
00691   entry_name = (char *)entry + sizeof(struct local_hostlist_entry);
00692   MEMCPY(entry_name, hostname, namelen);
00693   entry_name[namelen] = 0;
00694   entry->name = entry_name;
00695   ip_addr_copy(entry->addr, *addr);
00696   entry->next = local_hostlist_dynamic;
00697   local_hostlist_dynamic = entry;
00698   return ERR_OK;
00699 }
00700 #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC*/
00701 #endif /* DNS_LOCAL_HOSTLIST */
00702 
00703 /**
00704  * @ingroup dns
00705  * Look up a hostname in the array of known hostnames.
00706  *
00707  * @note This function only looks in the internal array of known
00708  * hostnames, it does not send out a query for the hostname if none
00709  * was found. The function dns_enqueue() can be used to send a query
00710  * for a hostname.
00711  *
00712  * @param name the hostname to look up
00713  * @param addr the hostname's IP address, as u32_t (instead of ip_addr_t to
00714  *         better check for failure: != IPADDR_NONE) or IPADDR_NONE if the hostname
00715  *         was not found in the cached dns_table.
00716  * @return ERR_OK if found, ERR_ARG if not found
00717  */
00718 static err_t
00719 dns_lookup(const char *name, ip_addr_t *addr LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype))
00720 {
00721   u8_t i;
00722 #if DNS_LOCAL_HOSTLIST
00723   if (dns_lookup_local(name, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)) == ERR_OK) {
00724     return ERR_OK;
00725   }
00726 #endif /* DNS_LOCAL_HOSTLIST */
00727 #ifdef DNS_LOOKUP_LOCAL_EXTERN
00728   if (DNS_LOOKUP_LOCAL_EXTERN(name, addr, LWIP_DNS_ADDRTYPE_ARG_OR_ZERO(dns_addrtype)) == ERR_OK) {
00729     return ERR_OK;
00730   }
00731 #endif /* DNS_LOOKUP_LOCAL_EXTERN */
00732 
00733   /* Walk through name list, return entry if found. If not, return NULL. */
00734   for (i = 0; i < DNS_TABLE_SIZE; ++i) {
00735     if ((dns_table[i].state == DNS_STATE_DONE) &&
00736         (lwip_strnicmp(name, dns_table[i].name, sizeof(dns_table[i].name)) == 0) &&
00737         LWIP_DNS_ADDRTYPE_MATCH_IP(dns_addrtype, dns_table[i].ipaddr)) {
00738       LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name));
00739       ip_addr_debug_print_val(DNS_DEBUG, dns_table[i].ipaddr);
00740       LWIP_DEBUGF(DNS_DEBUG, ("\n"));
00741       if (addr) {
00742         ip_addr_copy(*addr, dns_table[i].ipaddr);
00743       }
00744       return ERR_OK;
00745     }
00746   }
00747 
00748   return ERR_ARG;
00749 }
00750 
00751 /**
00752  * Compare the "dotted" name "query" with the encoded name "response"
00753  * to make sure an answer from the DNS server matches the current dns_table
00754  * entry (otherwise, answers might arrive late for hostname not on the list
00755  * any more).
00756  *
00757  * For now, this function compares case-insensitive to cope with all kinds of
00758  * servers. This also means that "dns 0x20 bit encoding" must be checked
00759  * externally, if we want to implement it.
00760  * Currently, the request is sent exactly as passed in by he user request.
00761  *
00762  * @param query hostname (not encoded) from the dns_table
00763  * @param p pbuf containing the encoded hostname in the DNS response
00764  * @param start_offset offset into p where the name starts
00765  * @return 0xFFFF: names differ, other: names equal -> offset behind name
00766  */
00767 static u16_t
00768 dns_compare_name(const char *query, struct pbuf *p, u16_t start_offset)
00769 {
00770   int n;
00771   u16_t response_offset = start_offset;
00772 
00773   do {
00774     n = pbuf_try_get_at(p, response_offset);
00775     if ((n < 0) || (response_offset == 0xFFFF)) {
00776       /* error or overflow */
00777       return 0xFFFF;
00778     }
00779     response_offset++;
00780     /** @see RFC 1035 - 4.1.4. Message compression */
00781     if ((n & 0xc0) == 0xc0) {
00782       /* Compressed name: cannot be equal since we don't send them */
00783       return 0xFFFF;
00784     } else {
00785       /* Not compressed name */
00786       while (n > 0) {
00787         int c = pbuf_try_get_at(p, response_offset);
00788         if (c < 0) {
00789           return 0xFFFF;
00790         }
00791         if (lwip_tolower((*query)) != lwip_tolower((u8_t)c)) {
00792           return 0xFFFF;
00793         }
00794         if (response_offset == 0xFFFF) {
00795           /* would overflow */
00796           return 0xFFFF;
00797         }
00798         response_offset++;
00799         ++query;
00800         --n;
00801       }
00802       ++query;
00803     }
00804     n = pbuf_try_get_at(p, response_offset);
00805     if (n < 0) {
00806       return 0xFFFF;
00807     }
00808   } while (n != 0);
00809 
00810   if (response_offset == 0xFFFF) {
00811     /* would overflow */
00812     return 0xFFFF;
00813   }
00814   return (u16_t)(response_offset + 1);
00815 }
00816 
00817 /**
00818  * Walk through a compact encoded DNS name and return the end of the name.
00819  *
00820  * @param p pbuf containing the name
00821  * @param query_idx start index into p pointing to encoded DNS name in the DNS server response
00822  * @return index to end of the name
00823  */
00824 static u16_t
00825 dns_skip_name(struct pbuf *p, u16_t query_idx)
00826 {
00827   int n;
00828   u16_t offset = query_idx;
00829 
00830   do {
00831     n = pbuf_try_get_at(p, offset++);
00832     if ((n < 0) || (offset == 0)) {
00833       return 0xFFFF;
00834     }
00835     /** @see RFC 1035 - 4.1.4. Message compression */
00836     if ((n & 0xc0) == 0xc0) {
00837       /* Compressed name: since we only want to skip it (not check it), stop here */
00838       break;
00839     } else {
00840       /* Not compressed name */
00841       if (offset + n >= p->tot_len) {
00842         return 0xFFFF;
00843       }
00844       offset = (u16_t)(offset + n);
00845     }
00846     n = pbuf_try_get_at(p, offset);
00847     if (n < 0) {
00848       return 0xFFFF;
00849     }
00850   } while (n != 0);
00851 
00852   if (offset == 0xFFFF) {
00853     return 0xFFFF;
00854   }
00855   return (u16_t)(offset + 1);
00856 }
00857 
00858 /**
00859  * Send a DNS query packet.
00860  *
00861  * @param idx the DNS table entry index for which to send a request
00862  * @return ERR_OK if packet is sent; an err_t indicating the problem otherwise
00863  */
00864 static err_t
00865 dns_send(u8_t idx)
00866 {
00867   err_t err;
00868   struct dns_hdr hdr;
00869   struct dns_query qry;
00870   struct pbuf *p;
00871   u16_t query_idx, copy_len;
00872   const char *hostname, *hostname_part;
00873   u8_t n;
00874   u8_t pcb_idx;
00875   struct dns_table_entry *entry = &dns_table[idx];
00876 
00877   LWIP_DEBUGF(DNS_DEBUG, ("dns_send: dns_servers[%"U16_F"] \"%s\": request\n",
00878                           (u16_t)(entry->server_idx), entry->name));
00879   LWIP_ASSERT("dns server out of array", entry->server_idx < DNS_MAX_SERVERS);
00880   if (ip_addr_isany_val(dns_servers[entry->server_idx])
00881 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
00882       && !entry->is_mdns
00883 #endif
00884      ) {
00885     /* DNS server not valid anymore, e.g. PPP netif has been shut down */
00886     /* call specified callback function if provided */
00887     dns_call_found(idx, NULL);
00888     /* flush this entry */
00889     entry->state = DNS_STATE_UNUSED;
00890     return ERR_OK;
00891   }
00892 
00893   /* if here, we have either a new query or a retry on a previous query to process */
00894   p = pbuf_alloc(PBUF_TRANSPORT, (u16_t)(SIZEOF_DNS_HDR + strlen(entry->name) + 2 +
00895                                          SIZEOF_DNS_QUERY), PBUF_RAM);
00896   if (p != NULL) {
00897     const ip_addr_t *dst;
00898     u16_t dst_port;
00899     /* fill dns header */
00900     memset(&hdr, 0, SIZEOF_DNS_HDR);
00901     hdr.id = lwip_htons(entry->txid);
00902     hdr.flags1 = DNS_FLAG1_RD;
00903     hdr.numquestions = PP_HTONS(1);
00904     pbuf_take(p, &hdr, SIZEOF_DNS_HDR);
00905     hostname = entry->name;
00906     --hostname;
00907 
00908     /* convert hostname into suitable query format. */
00909     query_idx = SIZEOF_DNS_HDR;
00910     do {
00911       ++hostname;
00912       hostname_part = hostname;
00913       for (n = 0; *hostname != '.' && *hostname != 0; ++hostname) {
00914         ++n;
00915       }
00916       copy_len = (u16_t)(hostname - hostname_part);
00917       if (query_idx + n + 1 > 0xFFFF) {
00918         /* u16_t overflow */
00919         goto overflow_return;
00920       }
00921       pbuf_put_at(p, query_idx, n);
00922       pbuf_take_at(p, hostname_part, copy_len, (u16_t)(query_idx + 1));
00923       query_idx = (u16_t)(query_idx + n + 1);
00924     } while (*hostname != 0);
00925     pbuf_put_at(p, query_idx, 0);
00926     query_idx++;
00927 
00928     /* fill dns query */
00929     if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype)) {
00930       qry.type = PP_HTONS(DNS_RRTYPE_AAAA);
00931     } else {
00932       qry.type = PP_HTONS(DNS_RRTYPE_A);
00933     }
00934     qry.cls = PP_HTONS(DNS_RRCLASS_IN);
00935     pbuf_take_at(p, &qry, SIZEOF_DNS_QUERY, query_idx);
00936 
00937 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00938     pcb_idx = entry->pcb_idx;
00939 #else
00940     pcb_idx = 0;
00941 #endif
00942     /* send dns packet */
00943     LWIP_DEBUGF(DNS_DEBUG, ("sending DNS request ID %d for name \"%s\" to server %d\r\n",
00944                             entry->txid, entry->name, entry->server_idx));
00945 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
00946     if (entry->is_mdns) {
00947       dst_port = DNS_MQUERY_PORT;
00948 #if LWIP_IPV6
00949       if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype)) {
00950         dst = &dns_mquery_v6group;
00951       }
00952 #endif
00953 #if LWIP_IPV4 && LWIP_IPV6
00954       else
00955 #endif
00956 #if LWIP_IPV4
00957       {
00958         dst = &dns_mquery_v4group;
00959       }
00960 #endif
00961     } else
00962 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
00963     {
00964       dst_port = DNS_SERVER_PORT;
00965       dst = &dns_servers[entry->server_idx];
00966     }
00967     err = udp_sendto(dns_pcbs[pcb_idx], p, dst, dst_port);
00968 
00969     /* free pbuf */
00970     pbuf_free(p);
00971   } else {
00972     err = ERR_MEM;
00973   }
00974 
00975   return err;
00976 overflow_return:
00977   pbuf_free(p);
00978   return ERR_VAL;
00979 }
00980 
00981 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
00982 static struct udp_pcb *
00983 dns_alloc_random_port(void)
00984 {
00985   err_t err;
00986   struct udp_pcb *pcb;
00987 
00988   pcb = udp_new_ip_type(IPADDR_TYPE_ANY);
00989   if (pcb == NULL) {
00990     /* out of memory, have to reuse an existing pcb */
00991     return NULL;
00992   }
00993   do {
00994     u16_t port = (u16_t)DNS_RAND_TXID();
00995     if (DNS_PORT_ALLOWED(port)) {
00996       err = udp_bind(pcb, IP_ANY_TYPE, port);
00997     } else {
00998       /* this port is not allowed, try again */
00999       err = ERR_USE;
01000     }
01001   } while (err == ERR_USE);
01002   if (err != ERR_OK) {
01003     udp_remove(pcb);
01004     return NULL;
01005   }
01006   udp_recv(pcb, dns_recv, NULL);
01007   return pcb;
01008 }
01009 
01010 /**
01011  * dns_alloc_pcb() - allocates a new pcb (or reuses an existing one) to be used
01012  * for sending a request
01013  *
01014  * @return an index into dns_pcbs
01015  */
01016 static u8_t
01017 dns_alloc_pcb(void)
01018 {
01019   u8_t i;
01020   u8_t idx;
01021 
01022   for (i = 0; i < DNS_MAX_SOURCE_PORTS; i++) {
01023     if (dns_pcbs[i] == NULL) {
01024       break;
01025     }
01026   }
01027   if (i < DNS_MAX_SOURCE_PORTS) {
01028     dns_pcbs[i] = dns_alloc_random_port();
01029     if (dns_pcbs[i] != NULL) {
01030       /* succeeded */
01031       dns_last_pcb_idx = i;
01032       return i;
01033     }
01034   }
01035   /* if we come here, creating a new UDP pcb failed, so we have to use
01036      an already existing one (so overflow is no issue) */
01037   for (i = 0, idx = (u8_t)(dns_last_pcb_idx + 1); i < DNS_MAX_SOURCE_PORTS; i++, idx++) {
01038     if (idx >= DNS_MAX_SOURCE_PORTS) {
01039       idx = 0;
01040     }
01041     if (dns_pcbs[idx] != NULL) {
01042       dns_last_pcb_idx = idx;
01043       return idx;
01044     }
01045   }
01046   return DNS_MAX_SOURCE_PORTS;
01047 }
01048 #endif /* ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0) */
01049 
01050 /**
01051  * dns_call_found() - call the found callback and check if there are duplicate
01052  * entries for the given hostname. If there are any, their found callback will
01053  * be called and they will be removed.
01054  *
01055  * @param idx dns table index of the entry that is resolved or removed
01056  * @param addr IP address for the hostname (or NULL on error or memory shortage)
01057  */
01058 static void
01059 dns_call_found(u8_t idx, ip_addr_t *addr)
01060 {
01061 #if ((LWIP_DNS_SECURE & (LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING | LWIP_DNS_SECURE_RAND_SRC_PORT)) != 0)
01062   u8_t i;
01063 #endif
01064 
01065 #if LWIP_IPV4 && LWIP_IPV6
01066   if (addr != NULL) {
01067     /* check that address type matches the request and adapt the table entry */
01068     if (IP_IS_V6_VAL(*addr)) {
01069       LWIP_ASSERT("invalid response", LWIP_DNS_ADDRTYPE_IS_IPV6(dns_table[idx].reqaddrtype));
01070       dns_table[idx].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV6;
01071     } else {
01072       LWIP_ASSERT("invalid response", !LWIP_DNS_ADDRTYPE_IS_IPV6(dns_table[idx].reqaddrtype));
01073       dns_table[idx].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV4;
01074     }
01075   }
01076 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01077 
01078 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
01079   for (i = 0; i < DNS_MAX_REQUESTS; i++) {
01080     if (dns_requests[i].found && (dns_requests[i].dns_table_idx == idx)) {
01081       (*dns_requests[i].found)(dns_table[idx].name, addr, dns_requests[i].arg);
01082       /* flush this entry */
01083       dns_requests[i].found = NULL;
01084     }
01085   }
01086 #else
01087   if (dns_requests[idx].found) {
01088     (*dns_requests[idx].found)(dns_table[idx].name, addr, dns_requests[idx].arg);
01089   }
01090   dns_requests[idx].found = NULL;
01091 #endif
01092 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
01093   /* close the pcb used unless other request are using it */
01094   for (i = 0; i < DNS_MAX_REQUESTS; i++) {
01095     if (i == idx) {
01096       continue; /* only check other requests */
01097     }
01098     if (dns_table[i].state == DNS_STATE_ASKING) {
01099       if (dns_table[i].pcb_idx == dns_table[idx].pcb_idx) {
01100         /* another request is still using the same pcb */
01101         dns_table[idx].pcb_idx = DNS_MAX_SOURCE_PORTS;
01102         break;
01103       }
01104     }
01105   }
01106   if (dns_table[idx].pcb_idx < DNS_MAX_SOURCE_PORTS) {
01107     /* if we come here, the pcb is not used any more and can be removed */
01108     udp_remove(dns_pcbs[dns_table[idx].pcb_idx]);
01109     dns_pcbs[dns_table[idx].pcb_idx] = NULL;
01110     dns_table[idx].pcb_idx = DNS_MAX_SOURCE_PORTS;
01111   }
01112 #endif
01113 }
01114 
01115 /* Create a query transmission ID that is unique for all outstanding queries */
01116 static u16_t
01117 dns_create_txid(void)
01118 {
01119   u16_t txid;
01120   u8_t i;
01121 
01122 again:
01123   txid = (u16_t)DNS_RAND_TXID();
01124 
01125   /* check whether the ID is unique */
01126   for (i = 0; i < DNS_TABLE_SIZE; i++) {
01127     if ((dns_table[i].state == DNS_STATE_ASKING) &&
01128         (dns_table[i].txid == txid)) {
01129       /* ID already used by another pending query */
01130       goto again;
01131     }
01132   }
01133 
01134   return txid;
01135 }
01136 
01137 /**
01138  * Check whether there are other backup DNS servers available to try
01139  */
01140 static u8_t
01141 dns_backupserver_available(struct dns_table_entry *pentry)
01142 {
01143   u8_t ret = 0;
01144 
01145   if (pentry) {
01146     if ((pentry->server_idx + 1 < DNS_MAX_SERVERS) && !ip_addr_isany_val(dns_servers[pentry->server_idx + 1])) {
01147       ret = 1;
01148     }
01149   }
01150 
01151   return ret;
01152 }
01153 
01154 /**
01155  * dns_check_entry() - see if entry has not yet been queried and, if so, sends out a query.
01156  * Check an entry in the dns_table:
01157  * - send out query for new entries
01158  * - retry old pending entries on timeout (also with different servers)
01159  * - remove completed entries from the table if their TTL has expired
01160  *
01161  * @param i index of the dns_table entry to check
01162  */
01163 static void
01164 dns_check_entry(u8_t i)
01165 {
01166   err_t err;
01167   struct dns_table_entry *entry = &dns_table[i];
01168 
01169   LWIP_ASSERT("array index out of bounds", i < DNS_TABLE_SIZE);
01170 
01171   switch (entry->state) {
01172     case DNS_STATE_NEW:
01173       /* initialize new entry */
01174       entry->txid = dns_create_txid();
01175       entry->state = DNS_STATE_ASKING;
01176       entry->server_idx = 0;
01177       entry->tmr = 1;
01178       entry->retries = 0;
01179 
01180       /* send DNS packet for this entry */
01181       err = dns_send(i);
01182       if (err != ERR_OK) {
01183         LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
01184                     ("dns_send returned error: %s\n", lwip_strerr(err)));
01185       }
01186       break;
01187     case DNS_STATE_ASKING:
01188       if (--entry->tmr == 0) {
01189         if (++entry->retries == DNS_MAX_RETRIES) {
01190           if (dns_backupserver_available(entry)
01191 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01192               && !entry->is_mdns
01193 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
01194              ) {
01195             /* change of server */
01196             entry->server_idx++;
01197             entry->tmr = 1;
01198             entry->retries = 0;
01199           } else {
01200             LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": timeout\n", entry->name));
01201             /* call specified callback function if provided */
01202             dns_call_found(i, NULL);
01203             /* flush this entry */
01204             entry->state = DNS_STATE_UNUSED;
01205             break;
01206           }
01207         } else {
01208           /* wait longer for the next retry */
01209           entry->tmr = entry->retries;
01210         }
01211 
01212         /* send DNS packet for this entry */
01213         err = dns_send(i);
01214         if (err != ERR_OK) {
01215           LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING,
01216                       ("dns_send returned error: %s\n", lwip_strerr(err)));
01217         }
01218       }
01219       break;
01220     case DNS_STATE_DONE:
01221       /* if the time to live is nul */
01222       if ((entry->ttl == 0) || (--entry->ttl == 0)) {
01223         LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": flush\n", entry->name));
01224         /* flush this entry, there cannot be any related pending entries in this state */
01225         entry->state = DNS_STATE_UNUSED;
01226       }
01227       break;
01228     case DNS_STATE_UNUSED:
01229       /* nothing to do */
01230       break;
01231     default:
01232       LWIP_ASSERT("unknown dns_table entry state:", 0);
01233       break;
01234   }
01235 }
01236 
01237 /**
01238  * Call dns_check_entry for each entry in dns_table - check all entries.
01239  */
01240 static void
01241 dns_check_entries(void)
01242 {
01243   u8_t i;
01244 
01245   for (i = 0; i < DNS_TABLE_SIZE; ++i) {
01246     dns_check_entry(i);
01247   }
01248 }
01249 
01250 /**
01251  * Save TTL and call dns_call_found for correct response.
01252  */
01253 static void
01254 dns_correct_response(u8_t idx, u32_t ttl)
01255 {
01256   struct dns_table_entry *entry = &dns_table[idx];
01257 
01258   entry->state = DNS_STATE_DONE;
01259 
01260   LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", entry->name));
01261   ip_addr_debug_print_val(DNS_DEBUG, entry->ipaddr);
01262   LWIP_DEBUGF(DNS_DEBUG, ("\n"));
01263 
01264   /* read the answer resource record's TTL, and maximize it if needed */
01265   entry->ttl = ttl;
01266   if (entry->ttl > DNS_MAX_TTL) {
01267     entry->ttl = DNS_MAX_TTL;
01268   }
01269   dns_call_found(idx, &entry->ipaddr);
01270 
01271   if (entry->ttl == 0) {
01272     /* RFC 883, page 29: "Zero values are
01273        interpreted to mean that the RR can only be used for the
01274        transaction in progress, and should not be cached."
01275        -> flush this entry now */
01276     /* entry reused during callback? */
01277     if (entry->state == DNS_STATE_DONE) {
01278       entry->state = DNS_STATE_UNUSED;
01279     }
01280   }
01281 }
01282 
01283 /**
01284  * Receive input function for DNS response packets arriving for the dns UDP pcb.
01285  */
01286 static void
01287 dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *addr, u16_t port)
01288 {
01289   u8_t i;
01290   u16_t txid;
01291   u16_t res_idx;
01292   struct dns_hdr hdr;
01293   struct dns_answer ans;
01294   struct dns_query qry;
01295   u16_t nquestions, nanswers;
01296 
01297   LWIP_UNUSED_ARG(arg);
01298   LWIP_UNUSED_ARG(pcb);
01299   LWIP_UNUSED_ARG(port);
01300 
01301   /* is the dns message big enough ? */
01302   if (p->tot_len < (SIZEOF_DNS_HDR + SIZEOF_DNS_QUERY)) {
01303     LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too small\n"));
01304     /* free pbuf and return */
01305     goto ignore_packet;
01306   }
01307 
01308   /* copy dns payload inside static buffer for processing */
01309   if (pbuf_copy_partial(p, &hdr, SIZEOF_DNS_HDR, 0) == SIZEOF_DNS_HDR) {
01310     /* Match the ID in the DNS header with the name table. */
01311     txid = lwip_htons(hdr.id);
01312     for (i = 0; i < DNS_TABLE_SIZE; i++) {
01313       struct dns_table_entry *entry = &dns_table[i];
01314       if ((entry->state == DNS_STATE_ASKING) &&
01315           (entry->txid == txid)) {
01316 
01317         /* We only care about the question(s) and the answers. The authrr
01318            and the extrarr are simply discarded. */
01319         nquestions = lwip_htons(hdr.numquestions);
01320         nanswers   = lwip_htons(hdr.numanswers);
01321 
01322         /* Check for correct response. */
01323         if ((hdr.flags1 & DNS_FLAG1_RESPONSE) == 0) {
01324           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": not a response\n", entry->name));
01325           goto ignore_packet; /* ignore this packet */
01326         }
01327         if (nquestions != 1) {
01328           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
01329           goto ignore_packet; /* ignore this packet */
01330         }
01331 
01332 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01333         if (!entry->is_mdns)
01334 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
01335         {
01336           /* Check whether response comes from the same network address to which the
01337              question was sent. (RFC 5452) */
01338           if (!ip_addr_cmp(addr, &dns_servers[entry->server_idx])) {
01339             goto ignore_packet; /* ignore this packet */
01340           }
01341         }
01342 
01343         /* Check if the name in the "question" part match with the name in the entry and
01344            skip it if equal. */
01345         res_idx = dns_compare_name(entry->name, p, SIZEOF_DNS_HDR);
01346         if (res_idx == 0xFFFF) {
01347           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
01348           goto ignore_packet; /* ignore this packet */
01349         }
01350 
01351         /* check if "question" part matches the request */
01352         if (pbuf_copy_partial(p, &qry, SIZEOF_DNS_QUERY, res_idx) != SIZEOF_DNS_QUERY) {
01353           goto ignore_packet; /* ignore this packet */
01354         }
01355         if ((qry.cls != PP_HTONS(DNS_RRCLASS_IN)) ||
01356             (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype) && (qry.type != PP_HTONS(DNS_RRTYPE_AAAA))) ||
01357             (!LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype) && (qry.type != PP_HTONS(DNS_RRTYPE_A)))) {
01358           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", entry->name));
01359           goto ignore_packet; /* ignore this packet */
01360         }
01361         /* skip the rest of the "question" part */
01362         if (res_idx + SIZEOF_DNS_QUERY > 0xFFFF) {
01363           goto ignore_packet;
01364         }
01365         res_idx = (u16_t)(res_idx + SIZEOF_DNS_QUERY);
01366 
01367         /* Check for error. If so, call callback to inform. */
01368         if (hdr.flags2 & DNS_FLAG2_ERR_MASK) {
01369           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", entry->name));
01370 
01371           /* if there is another backup DNS server to try
01372            * then don't stop the DNS request
01373            */
01374           if (dns_backupserver_available(entry)) {
01375             /* avoid retrying the same server */
01376             entry->retries = DNS_MAX_RETRIES-1;
01377             entry->tmr     = 1;
01378 
01379             /* contact next available server for this entry */
01380             dns_check_entry(i);
01381 
01382             goto ignore_packet;
01383           }
01384         } else {
01385           while ((nanswers > 0) && (res_idx < p->tot_len)) {
01386             /* skip answer resource record's host name */
01387             res_idx = dns_skip_name(p, res_idx);
01388             if (res_idx == 0xFFFF) {
01389               goto ignore_packet; /* ignore this packet */
01390             }
01391 
01392             /* Check for IP address type and Internet class. Others are discarded. */
01393             if (pbuf_copy_partial(p, &ans, SIZEOF_DNS_ANSWER, res_idx) != SIZEOF_DNS_ANSWER) {
01394               goto ignore_packet; /* ignore this packet */
01395             }
01396             if (res_idx + SIZEOF_DNS_ANSWER > 0xFFFF) {
01397               goto ignore_packet;
01398             }
01399             res_idx = (u16_t)(res_idx + SIZEOF_DNS_ANSWER);
01400 
01401             if (ans.cls == PP_HTONS(DNS_RRCLASS_IN)) {
01402 #if LWIP_IPV4
01403               if ((ans.type == PP_HTONS(DNS_RRTYPE_A)) && (ans.len == PP_HTONS(sizeof(ip4_addr_t)))) {
01404 #if LWIP_IPV4 && LWIP_IPV6
01405                 if (!LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype))
01406 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01407                 {
01408                   ip4_addr_t ip4addr;
01409                   /* read the IP address after answer resource record's header */
01410                   if (pbuf_copy_partial(p, &ip4addr, sizeof(ip4_addr_t), res_idx) != sizeof(ip4_addr_t)) {
01411                     goto ignore_packet; /* ignore this packet */
01412                   }
01413                   ip_addr_copy_from_ip4(dns_table[i].ipaddr, ip4addr);
01414                   pbuf_free(p);
01415                   /* handle correct response */
01416                   dns_correct_response(i, lwip_ntohl(ans.ttl));
01417                   return;
01418                 }
01419               }
01420 #endif /* LWIP_IPV4 */
01421 #if LWIP_IPV6
01422               if ((ans.type == PP_HTONS(DNS_RRTYPE_AAAA)) && (ans.len == PP_HTONS(sizeof(ip6_addr_p_t)))) {
01423 #if LWIP_IPV4 && LWIP_IPV6
01424                 if (LWIP_DNS_ADDRTYPE_IS_IPV6(entry->reqaddrtype))
01425 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01426                 {
01427                   ip6_addr_p_t ip6addr;
01428                   /* read the IP address after answer resource record's header */
01429                   if (pbuf_copy_partial(p, &ip6addr, sizeof(ip6_addr_p_t), res_idx) != sizeof(ip6_addr_p_t)) {
01430                     goto ignore_packet; /* ignore this packet */
01431                   }
01432                   /* @todo: scope ip6addr? Might be required for link-local addresses at least? */
01433                   ip_addr_copy_from_ip6_packed(dns_table[i].ipaddr, ip6addr);
01434                   pbuf_free(p);
01435                   /* handle correct response */
01436                   dns_correct_response(i, lwip_ntohl(ans.ttl));
01437                   return;
01438                 }
01439               }
01440 #endif /* LWIP_IPV6 */
01441             }
01442             /* skip this answer */
01443             if ((int)(res_idx + lwip_htons(ans.len)) > 0xFFFF) {
01444               goto ignore_packet; /* ignore this packet */
01445             }
01446             res_idx = (u16_t)(res_idx + lwip_htons(ans.len));
01447             --nanswers;
01448           }
01449 #if LWIP_IPV4 && LWIP_IPV6
01450           if ((entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) ||
01451               (entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV6_IPV4)) {
01452             if (entry->reqaddrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) {
01453               /* IPv4 failed, try IPv6 */
01454               dns_table[i].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV6;
01455             } else {
01456               /* IPv6 failed, try IPv4 */
01457               dns_table[i].reqaddrtype = LWIP_DNS_ADDRTYPE_IPV4;
01458             }
01459             pbuf_free(p);
01460             dns_table[i].state = DNS_STATE_NEW;
01461             dns_check_entry(i);
01462             return;
01463           }
01464 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01465           LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in response\n", entry->name));
01466         }
01467         /* call callback to indicate error, clean up memory and return */
01468         pbuf_free(p);
01469         dns_call_found(i, NULL);
01470         dns_table[i].state = DNS_STATE_UNUSED;
01471         return;
01472       }
01473     }
01474   }
01475 
01476 ignore_packet:
01477   /* deallocate memory and return */
01478   pbuf_free(p);
01479   return;
01480 }
01481 
01482 /**
01483  * Queues a new hostname to resolve and sends out a DNS query for that hostname
01484  *
01485  * @param name the hostname that is to be queried
01486  * @param hostnamelen length of the hostname
01487  * @param found a callback function to be called on success, failure or timeout
01488  * @param callback_arg argument to pass to the callback function
01489  * @return err_t return code.
01490  */
01491 static err_t
01492 dns_enqueue(const char *name, size_t hostnamelen, dns_found_callback found,
01493             void *callback_arg LWIP_DNS_ADDRTYPE_ARG(u8_t dns_addrtype) LWIP_DNS_ISMDNS_ARG(u8_t is_mdns))
01494 {
01495   u8_t i;
01496   u8_t lseq, lseqi;
01497   struct dns_table_entry *entry = NULL;
01498   size_t namelen;
01499   struct dns_req_entry *req;
01500 
01501 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
01502   u8_t r;
01503   /* check for duplicate entries */
01504   for (i = 0; i < DNS_TABLE_SIZE; i++) {
01505     if ((dns_table[i].state == DNS_STATE_ASKING) &&
01506         (lwip_strnicmp(name, dns_table[i].name, sizeof(dns_table[i].name)) == 0)) {
01507 #if LWIP_IPV4 && LWIP_IPV6
01508       if (dns_table[i].reqaddrtype != dns_addrtype) {
01509         /* requested address types don't match
01510            this can lead to 2 concurrent requests, but mixing the address types
01511            for the same host should not be that common */
01512         continue;
01513       }
01514 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01515       /* this is a duplicate entry, find a free request entry */
01516       for (r = 0; r < DNS_MAX_REQUESTS; r++) {
01517         if (dns_requests[r].found == 0) {
01518           dns_requests[r].found = found;
01519           dns_requests[r].arg = callback_arg;
01520           dns_requests[r].dns_table_idx = i;
01521           LWIP_DNS_SET_ADDRTYPE(dns_requests[r].reqaddrtype, dns_addrtype);
01522           LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": duplicate request\n", name));
01523           return ERR_INPROGRESS;
01524         }
01525       }
01526     }
01527   }
01528   /* no duplicate entries found */
01529 #endif
01530 
01531   /* search an unused entry, or the oldest one */
01532   lseq = 0;
01533   lseqi = DNS_TABLE_SIZE;
01534   for (i = 0; i < DNS_TABLE_SIZE; ++i) {
01535     entry = &dns_table[i];
01536     /* is it an unused entry ? */
01537     if (entry->state == DNS_STATE_UNUSED) {
01538       break;
01539     }
01540     /* check if this is the oldest completed entry */
01541     if (entry->state == DNS_STATE_DONE) {
01542       u8_t age = (u8_t)(dns_seqno - entry->seqno);
01543       if (age > lseq) {
01544         lseq = age;
01545         lseqi = i;
01546       }
01547     }
01548   }
01549 
01550   /* if we don't have found an unused entry, use the oldest completed one */
01551   if (i == DNS_TABLE_SIZE) {
01552     if ((lseqi >= DNS_TABLE_SIZE) || (dns_table[lseqi].state != DNS_STATE_DONE)) {
01553       /* no entry can be used now, table is full */
01554       LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS entries table is full\n", name));
01555       return ERR_MEM;
01556     } else {
01557       /* use the oldest completed one */
01558       i = lseqi;
01559       entry = &dns_table[i];
01560     }
01561   }
01562 
01563 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_NO_MULTIPLE_OUTSTANDING) != 0)
01564   /* find a free request entry */
01565   req = NULL;
01566   for (r = 0; r < DNS_MAX_REQUESTS; r++) {
01567     if (dns_requests[r].found == NULL) {
01568       req = &dns_requests[r];
01569       break;
01570     }
01571   }
01572   if (req == NULL) {
01573     /* no request entry can be used now, table is full */
01574     LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS request entries table is full\n", name));
01575     return ERR_MEM;
01576   }
01577   req->dns_table_idx = i;
01578 #else
01579   /* in this configuration, the entry index is the same as the request index */
01580   req = &dns_requests[i];
01581 #endif
01582 
01583   /* use this entry */
01584   LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS entry %"U16_F"\n", name, (u16_t)(i)));
01585 
01586   /* fill the entry */
01587   entry->state = DNS_STATE_NEW;
01588   entry->seqno = dns_seqno;
01589   LWIP_DNS_SET_ADDRTYPE(entry->reqaddrtype, dns_addrtype);
01590   LWIP_DNS_SET_ADDRTYPE(req->reqaddrtype, dns_addrtype);
01591   req->found = found;
01592   req->arg   = callback_arg;
01593   namelen = LWIP_MIN(hostnamelen, DNS_MAX_NAME_LENGTH - 1);
01594   MEMCPY(entry->name, name, namelen);
01595   entry->name[namelen] = 0;
01596 
01597 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) != 0)
01598   entry->pcb_idx = dns_alloc_pcb();
01599   if (entry->pcb_idx >= DNS_MAX_SOURCE_PORTS) {
01600     /* failed to get a UDP pcb */
01601     LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": failed to allocate a pcb\n", name));
01602     entry->state = DNS_STATE_UNUSED;
01603     req->found = NULL;
01604     return ERR_MEM;
01605   }
01606   LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS pcb %"U16_F"\n", name, (u16_t)(entry->pcb_idx)));
01607 #endif
01608 
01609 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01610   entry->is_mdns = is_mdns;
01611 #endif
01612 
01613   dns_seqno++;
01614 
01615   /* force to send query without waiting timer */
01616   dns_check_entry(i);
01617 
01618   /* dns query is enqueued */
01619   return ERR_INPROGRESS;
01620 }
01621 
01622 /**
01623  * @ingroup dns
01624  * Resolve a hostname (string) into an IP address.
01625  * NON-BLOCKING callback version for use with raw API!!!
01626  *
01627  * Returns immediately with one of err_t return codes:
01628  * - ERR_OK if hostname is a valid IP address string or the host
01629  *   name is already in the local names table.
01630  * - ERR_INPROGRESS enqueue a request to be sent to the DNS server
01631  *   for resolution if no errors are present.
01632  * - ERR_ARG: dns client not initialized or invalid hostname
01633  *
01634  * @param hostname the hostname that is to be queried
01635  * @param addr pointer to a ip_addr_t where to store the address if it is already
01636  *             cached in the dns_table (only valid if ERR_OK is returned!)
01637  * @param found a callback function to be called on success, failure or timeout (only if
01638  *              ERR_INPROGRESS is returned!)
01639  * @param callback_arg argument to pass to the callback function
01640  * @return a err_t return code.
01641  */
01642 err_t
01643 dns_gethostbyname(const char *hostname, ip_addr_t *addr, dns_found_callback found,
01644                   void *callback_arg)
01645 {
01646   return dns_gethostbyname_addrtype(hostname, addr, found, callback_arg, LWIP_DNS_ADDRTYPE_DEFAULT);
01647 }
01648 
01649 /**
01650  * @ingroup dns
01651  * Like dns_gethostbyname, but returned address type can be controlled:
01652  * @param hostname the hostname that is to be queried
01653  * @param addr pointer to a ip_addr_t where to store the address if it is already
01654  *             cached in the dns_table (only valid if ERR_OK is returned!)
01655  * @param found a callback function to be called on success, failure or timeout (only if
01656  *              ERR_INPROGRESS is returned!)
01657  * @param callback_arg argument to pass to the callback function
01658  * @param dns_addrtype - LWIP_DNS_ADDRTYPE_IPV4_IPV6: try to resolve IPv4 first, try IPv6 if IPv4 fails only
01659  *                     - LWIP_DNS_ADDRTYPE_IPV6_IPV4: try to resolve IPv6 first, try IPv4 if IPv6 fails only
01660  *                     - LWIP_DNS_ADDRTYPE_IPV4: try to resolve IPv4 only
01661  *                     - LWIP_DNS_ADDRTYPE_IPV6: try to resolve IPv6 only
01662  */
01663 err_t
01664 dns_gethostbyname_addrtype(const char *hostname, ip_addr_t *addr, dns_found_callback found,
01665                            void *callback_arg, u8_t dns_addrtype)
01666 {
01667   size_t hostnamelen;
01668 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01669   u8_t is_mdns;
01670 #endif
01671   /* not initialized or no valid server yet, or invalid addr pointer
01672    * or invalid hostname or invalid hostname length */
01673   if ((addr == NULL) ||
01674       (!hostname) || (!hostname[0])) {
01675     return ERR_ARG;
01676   }
01677 #if ((LWIP_DNS_SECURE & LWIP_DNS_SECURE_RAND_SRC_PORT) == 0)
01678   if (dns_pcbs[0] == NULL) {
01679     return ERR_ARG;
01680   }
01681 #endif
01682   hostnamelen = strlen(hostname);
01683   if (hostnamelen >= DNS_MAX_NAME_LENGTH) {
01684     LWIP_DEBUGF(DNS_DEBUG, ("dns_gethostbyname: name too long to resolve"));
01685     return ERR_ARG;
01686   }
01687 
01688 
01689 #if LWIP_HAVE_LOOPIF
01690   if (strcmp(hostname, "localhost") == 0) {
01691     ip_addr_set_loopback(LWIP_DNS_ADDRTYPE_IS_IPV6(dns_addrtype), addr);
01692     return ERR_OK;
01693   }
01694 #endif /* LWIP_HAVE_LOOPIF */
01695 
01696   /* host name already in octet notation? set ip addr and return ERR_OK */
01697   if (ipaddr_aton(hostname, addr)) {
01698 #if LWIP_IPV4 && LWIP_IPV6
01699     if ((IP_IS_V6(addr) && (dns_addrtype != LWIP_DNS_ADDRTYPE_IPV4)) ||
01700         (IP_IS_V4(addr) && (dns_addrtype != LWIP_DNS_ADDRTYPE_IPV6)))
01701 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01702     {
01703       return ERR_OK;
01704     }
01705   }
01706   /* already have this address cached? */
01707   if (dns_lookup(hostname, addr LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)) == ERR_OK) {
01708     return ERR_OK;
01709   }
01710 #if LWIP_IPV4 && LWIP_IPV6
01711   if ((dns_addrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) || (dns_addrtype == LWIP_DNS_ADDRTYPE_IPV6_IPV4)) {
01712     /* fallback to 2nd IP type and try again to lookup */
01713     u8_t fallback;
01714     if (dns_addrtype == LWIP_DNS_ADDRTYPE_IPV4_IPV6) {
01715       fallback = LWIP_DNS_ADDRTYPE_IPV6;
01716     } else {
01717       fallback = LWIP_DNS_ADDRTYPE_IPV4;
01718     }
01719     if (dns_lookup(hostname, addr LWIP_DNS_ADDRTYPE_ARG(fallback)) == ERR_OK) {
01720       return ERR_OK;
01721     }
01722   }
01723 #else /* LWIP_IPV4 && LWIP_IPV6 */
01724   LWIP_UNUSED_ARG(dns_addrtype);
01725 #endif /* LWIP_IPV4 && LWIP_IPV6 */
01726 
01727 #if LWIP_DNS_SUPPORT_MDNS_QUERIES
01728   if (strstr(hostname, ".local") == &hostname[hostnamelen] - 6) {
01729     is_mdns = 1;
01730   } else {
01731     is_mdns = 0;
01732   }
01733 
01734   if (!is_mdns)
01735 #endif /* LWIP_DNS_SUPPORT_MDNS_QUERIES */
01736   {
01737     /* prevent calling found callback if no server is set, return error instead */
01738     if (ip_addr_isany_val(dns_servers[0])) {
01739       return ERR_VAL;
01740     }
01741   }
01742 
01743   /* queue query with specified callback */
01744   return dns_enqueue(hostname, hostnamelen, found, callback_arg LWIP_DNS_ADDRTYPE_ARG(dns_addrtype)
01745                      LWIP_DNS_ISMDNS_ARG(is_mdns));
01746 }
01747 
01748 #endif /* LWIP_FULL_DNS */
01749 
01750 #endif /* LWIP_DNS */