| /** |
| * @file |
| * DNS - host name to IP address resolver. |
| * |
| */ |
| |
| /** |
| |
| * This file implements a DNS host name to IP address resolver. |
| |
| * Port to lwIP from uIP |
| * by Jim Pettinato April 2007 |
| |
| * uIP version Copyright (c) 2002-2003, Adam Dunkels. |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * 3. The name of the author may not be used to endorse or promote |
| * products derived from this software without specific prior |
| * written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS |
| * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
| * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY |
| * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE |
| * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
| * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
| * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
| * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| * |
| * |
| * DNS.C |
| * |
| * The lwIP DNS resolver functions are used to lookup a host name and |
| * map it to a numerical IP address. It maintains a list of resolved |
| * hostnames that can be queried with the dns_lookup() function. |
| * New hostnames can be resolved using the dns_query() function. |
| * |
| * The lwIP version of the resolver also adds a non-blocking version of |
| * gethostbyname() that will work with a raw API application. This function |
| * checks for an IP address string first and converts it if it is valid. |
| * gethostbyname() then does a dns_lookup() to see if the name is |
| * already in the table. If so, the IP is returned. If not, a query is |
| * issued and the function returns with a ERR_INPROGRESS status. The app |
| * using the dns client must then go into a waiting state. |
| * |
| * Once a hostname has been resolved (or found to be non-existent), |
| * the resolver code calls a specified callback function (which |
| * must be implemented by the module that uses the resolver). |
| */ |
| |
| /*----------------------------------------------------------------------------- |
| * RFC 1035 - Domain names - implementation and specification |
| * RFC 2181 - Clarifications to the DNS Specification |
| *----------------------------------------------------------------------------*/ |
| |
| /** @todo: define good default values (rfc compliance) */ |
| /** @todo: improve answer parsing, more checkings... */ |
| /** @todo: check RFC1035 - 7.3. Processing responses */ |
| |
| /*----------------------------------------------------------------------------- |
| * Includes |
| *----------------------------------------------------------------------------*/ |
| |
| #include "lwip/opt.h" |
| |
| #if LWIP_DNS /* don't build if not configured for use in lwipopts.h */ |
| |
| #include "lwip/udp.h" |
| #include "lwip/mem.h" |
| #include "lwip/memp.h" |
| #include "lwip/dns.h" |
| |
| #include <string.h> |
| |
| /** DNS server IP address */ |
| #ifndef DNS_SERVER_ADDRESS |
| #define DNS_SERVER_ADDRESS(ipaddr) (ip4_addr_set_u32(ipaddr, ipaddr_addr("208.67.222.222"))) /* resolver1.opendns.com */ |
| #endif |
| |
| /** DNS server port address */ |
| #ifndef DNS_SERVER_PORT |
| #define DNS_SERVER_PORT 53 |
| #endif |
| |
| /** DNS maximum number of retries when asking for a name, before "timeout". */ |
| #ifndef DNS_MAX_RETRIES |
| #define DNS_MAX_RETRIES 4 |
| #endif |
| |
| /** DNS resource record max. TTL (one week as default) */ |
| #ifndef DNS_MAX_TTL |
| #define DNS_MAX_TTL 604800 |
| #endif |
| |
| /* DNS protocol flags */ |
| #define DNS_FLAG1_RESPONSE 0x80 |
| #define DNS_FLAG1_OPCODE_STATUS 0x10 |
| #define DNS_FLAG1_OPCODE_INVERSE 0x08 |
| #define DNS_FLAG1_OPCODE_STANDARD 0x00 |
| #define DNS_FLAG1_AUTHORATIVE 0x04 |
| #define DNS_FLAG1_TRUNC 0x02 |
| #define DNS_FLAG1_RD 0x01 |
| #define DNS_FLAG2_RA 0x80 |
| #define DNS_FLAG2_ERR_MASK 0x0f |
| #define DNS_FLAG2_ERR_NONE 0x00 |
| #define DNS_FLAG2_ERR_NAME 0x03 |
| |
| /* DNS protocol states */ |
| #define DNS_STATE_UNUSED 0 |
| #define DNS_STATE_NEW 1 |
| #define DNS_STATE_ASKING 2 |
| #define DNS_STATE_DONE 3 |
| |
| #ifdef PACK_STRUCT_USE_INCLUDES |
| # include "arch/bpstruct.h" |
| #endif |
| PACK_STRUCT_BEGIN |
| /** DNS message header */ |
| struct dns_hdr { |
| PACK_STRUCT_FIELD(u16_t id); |
| PACK_STRUCT_FIELD(u8_t flags1); |
| PACK_STRUCT_FIELD(u8_t flags2); |
| PACK_STRUCT_FIELD(u16_t numquestions); |
| PACK_STRUCT_FIELD(u16_t numanswers); |
| PACK_STRUCT_FIELD(u16_t numauthrr); |
| PACK_STRUCT_FIELD(u16_t numextrarr); |
| } PACK_STRUCT_STRUCT; |
| PACK_STRUCT_END |
| #ifdef PACK_STRUCT_USE_INCLUDES |
| # include "arch/epstruct.h" |
| #endif |
| #define SIZEOF_DNS_HDR 12 |
| |
| /** DNS query message structure. |
| No packing needed: only used locally on the stack. */ |
| struct dns_query { |
| /* DNS query record starts with either a domain name or a pointer |
| to a name already present somewhere in the packet. */ |
| u16_t type; |
| u16_t cls; |
| }; |
| #define SIZEOF_DNS_QUERY 4 |
| |
| /** DNS answer message structure. |
| No packing needed: only used locally on the stack. */ |
| struct dns_answer { |
| /* DNS answer record starts with either a domain name or a pointer |
| to a name already present somewhere in the packet. */ |
| u16_t type; |
| u16_t cls; |
| u32_t ttl; |
| u16_t len; |
| }; |
| #define SIZEOF_DNS_ANSWER 10 |
| |
| /** DNS table entry */ |
| struct dns_table_entry { |
| u8_t state; |
| u8_t numdns; |
| u8_t tmr; |
| u8_t retries; |
| u8_t seqno; |
| u8_t err; |
| u32_t ttl; |
| char name[DNS_MAX_NAME_LENGTH]; |
| ip_addr_t ipaddr; |
| /* pointer to callback on DNS query done */ |
| dns_found_callback found; |
| void *arg; |
| }; |
| |
| #if DNS_LOCAL_HOSTLIST |
| |
| #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC |
| /** Local host-list. For hostnames in this list, no |
| * external name resolution is performed */ |
| static struct local_hostlist_entry *local_hostlist_dynamic; |
| #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ |
| |
| /** Defining this allows the local_hostlist_static to be placed in a different |
| * linker section (e.g. FLASH) */ |
| #ifndef DNS_LOCAL_HOSTLIST_STORAGE_PRE |
| #define DNS_LOCAL_HOSTLIST_STORAGE_PRE static |
| #endif /* DNS_LOCAL_HOSTLIST_STORAGE_PRE */ |
| /** Defining this allows the local_hostlist_static to be placed in a different |
| * linker section (e.g. FLASH) */ |
| #ifndef DNS_LOCAL_HOSTLIST_STORAGE_POST |
| #define DNS_LOCAL_HOSTLIST_STORAGE_POST |
| #endif /* DNS_LOCAL_HOSTLIST_STORAGE_POST */ |
| DNS_LOCAL_HOSTLIST_STORAGE_PRE struct local_hostlist_entry local_hostlist_static[] |
| DNS_LOCAL_HOSTLIST_STORAGE_POST = DNS_LOCAL_HOSTLIST_INIT; |
| |
| #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ |
| |
| static void dns_init_local(); |
| #endif /* DNS_LOCAL_HOSTLIST */ |
| |
| |
| /* forward declarations */ |
| static void dns_recv(void *s, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port); |
| static void dns_check_entries(void); |
| |
| /*----------------------------------------------------------------------------- |
| * Globales |
| *----------------------------------------------------------------------------*/ |
| |
| /* DNS variables */ |
| static struct udp_pcb *dns_pcb; |
| static u8_t dns_seqno; |
| static struct dns_table_entry dns_table[DNS_TABLE_SIZE]; |
| static ip_addr_t dns_servers[DNS_MAX_SERVERS]; |
| /** Contiguous buffer for processing responses */ |
| static u8_t dns_payload_buffer[LWIP_MEM_ALIGN_BUFFER(DNS_MSG_SIZE)]; |
| static u8_t* dns_payload; |
| |
| /** |
| * Initialize the resolver: set up the UDP pcb and configure the default server |
| * (DNS_SERVER_ADDRESS). |
| */ |
| void |
| dns_init() |
| { |
| ip_addr_t dnsserver; |
| |
| dns_payload = (u8_t *)LWIP_MEM_ALIGN(dns_payload_buffer); |
| |
| /* initialize default DNS server address */ |
| DNS_SERVER_ADDRESS(&dnsserver); |
| |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_init: initializing\n")); |
| |
| /* if dns client not yet initialized... */ |
| if (dns_pcb == NULL) { |
| dns_pcb = udp_new(); |
| |
| if (dns_pcb != NULL) { |
| /* initialize DNS table not needed (initialized to zero since it is a |
| * global variable) */ |
| LWIP_ASSERT("For implicit initialization to work, DNS_STATE_UNUSED needs to be 0", |
| DNS_STATE_UNUSED == 0); |
| |
| /* initialize DNS client */ |
| udp_bind(dns_pcb, IP_ADDR_ANY, 0); |
| udp_recv(dns_pcb, dns_recv, NULL); |
| |
| /* initialize default DNS primary server */ |
| dns_setserver(0, &dnsserver); |
| } |
| } |
| #if DNS_LOCAL_HOSTLIST |
| dns_init_local(); |
| #endif |
| } |
| |
| /** |
| * Initialize one of the DNS servers. |
| * |
| * @param numdns the index of the DNS server to set must be < DNS_MAX_SERVERS |
| * @param dnsserver IP address of the DNS server to set |
| */ |
| void |
| dns_setserver(u8_t numdns, ip_addr_t *dnsserver) |
| { |
| if ((numdns < DNS_MAX_SERVERS) && (dns_pcb != NULL) && |
| (dnsserver != NULL) && !ip_addr_isany(dnsserver)) { |
| dns_servers[numdns] = (*dnsserver); |
| } |
| } |
| |
| /** |
| * Obtain one of the currently configured DNS server. |
| * |
| * @param numdns the index of the DNS server |
| * @return IP address of the indexed DNS server or "ip_addr_any" if the DNS |
| * server has not been configured. |
| */ |
| ip_addr_t |
| dns_getserver(u8_t numdns) |
| { |
| if (numdns < DNS_MAX_SERVERS) { |
| return dns_servers[numdns]; |
| } else { |
| return *IP_ADDR_ANY; |
| } |
| } |
| |
| /** |
| * The DNS resolver client timer - handle retries and timeouts and should |
| * be called every DNS_TMR_INTERVAL milliseconds (every second by default). |
| */ |
| void |
| dns_tmr(void) |
| { |
| if (dns_pcb != NULL) { |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_tmr: dns_check_entries\n")); |
| dns_check_entries(); |
| } |
| } |
| |
| #if DNS_LOCAL_HOSTLIST |
| static void |
| dns_init_local() |
| { |
| #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT) |
| int i; |
| struct local_hostlist_entry *entry; |
| /* Dynamic: copy entries from DNS_LOCAL_HOSTLIST_INIT to list */ |
| struct local_hostlist_entry local_hostlist_init[] = DNS_LOCAL_HOSTLIST_INIT; |
| size_t namelen; |
| for (i = 0; i < sizeof(local_hostlist_init) / sizeof(struct local_hostlist_entry); i++) { |
| struct local_hostlist_entry *init_entry = &local_hostlist_init[i]; |
| LWIP_ASSERT("invalid host name (NULL)", init_entry->name != NULL); |
| namelen = strlen(init_entry->name); |
| LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN); |
| entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST); |
| LWIP_ASSERT("mem-error in dns_init_local", entry != NULL); |
| if (entry != NULL) { |
| entry->name = (char*)entry + sizeof(struct local_hostlist_entry); |
| MEMCPY((char*)entry->name, init_entry->name, namelen); |
| ((char*)entry->name)[namelen] = 0; |
| entry->addr = init_entry->addr; |
| entry->next = local_hostlist_dynamic; |
| local_hostlist_dynamic = entry; |
| } |
| } |
| #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC && defined(DNS_LOCAL_HOSTLIST_INIT) */ |
| } |
| |
| /** |
| * Scans the local host-list for a hostname. |
| * |
| * @param hostname Hostname to look for in the local host-list |
| * @return The first IP address for the hostname in the local host-list or |
| * IPADDR_NONE if not found. |
| */ |
| static u32_t |
| dns_lookup_local(const char *hostname) |
| { |
| #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC |
| struct local_hostlist_entry *entry = local_hostlist_dynamic; |
| while(entry != NULL) { |
| if(strcmp(entry->name, hostname) == 0) { |
| return ip4_addr_get_u32(&entry->addr); |
| } |
| entry = entry->next; |
| } |
| #else /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ |
| int i; |
| for (i = 0; i < sizeof(local_hostlist_static) / sizeof(struct local_hostlist_entry); i++) { |
| if(strcmp(local_hostlist_static[i].name, hostname) == 0) { |
| return ip4_addr_get_u32(&local_hostlist_static[i].addr); |
| } |
| } |
| #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC */ |
| return IPADDR_NONE; |
| } |
| |
| #if DNS_LOCAL_HOSTLIST_IS_DYNAMIC |
| /** Remove all entries from the local host-list for a specific hostname |
| * and/or IP addess |
| * |
| * @param hostname hostname for which entries shall be removed from the local |
| * host-list |
| * @param addr address for which entries shall be removed from the local host-list |
| * @return the number of removed entries |
| */ |
| int |
| dns_local_removehost(const char *hostname, const ip_addr_t *addr) |
| { |
| int removed = 0; |
| struct local_hostlist_entry *entry = local_hostlist_dynamic; |
| struct local_hostlist_entry *last_entry = NULL; |
| while (entry != NULL) { |
| if (((hostname == NULL) || !strcmp(entry->name, hostname)) && |
| ((addr == NULL) || ip_addr_cmp(&entry->addr, addr))) { |
| struct local_hostlist_entry *free_entry; |
| if (last_entry != NULL) { |
| last_entry->next = entry->next; |
| } else { |
| local_hostlist_dynamic = entry->next; |
| } |
| free_entry = entry; |
| entry = entry->next; |
| memp_free(MEMP_LOCALHOSTLIST, free_entry); |
| removed++; |
| } else { |
| last_entry = entry; |
| entry = entry->next; |
| } |
| } |
| return removed; |
| } |
| |
| /** |
| * Add a hostname/IP address pair to the local host-list. |
| * Duplicates are not checked. |
| * |
| * @param hostname hostname of the new entry |
| * @param addr IP address of the new entry |
| * @return ERR_OK if succeeded or ERR_MEM on memory error |
| */ |
| err_t |
| dns_local_addhost(const char *hostname, const ip_addr_t *addr) |
| { |
| struct local_hostlist_entry *entry; |
| size_t namelen; |
| LWIP_ASSERT("invalid host name (NULL)", hostname != NULL); |
| namelen = strlen(hostname); |
| LWIP_ASSERT("namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN", namelen <= DNS_LOCAL_HOSTLIST_MAX_NAMELEN); |
| entry = (struct local_hostlist_entry *)memp_malloc(MEMP_LOCALHOSTLIST); |
| if (entry == NULL) { |
| return ERR_MEM; |
| } |
| entry->name = (char*)entry + sizeof(struct local_hostlist_entry); |
| MEMCPY((char*)entry->name, hostname, namelen); |
| ((char*)entry->name)[namelen] = 0; |
| ip_addr_copy(entry->addr, *addr); |
| entry->next = local_hostlist_dynamic; |
| local_hostlist_dynamic = entry; |
| return ERR_OK; |
| } |
| #endif /* DNS_LOCAL_HOSTLIST_IS_DYNAMIC*/ |
| #endif /* DNS_LOCAL_HOSTLIST */ |
| |
| /** |
| * Look up a hostname in the array of known hostnames. |
| * |
| * @note This function only looks in the internal array of known |
| * hostnames, it does not send out a query for the hostname if none |
| * was found. The function dns_enqueue() can be used to send a query |
| * for a hostname. |
| * |
| * @param name the hostname to look up |
| * @return the hostname's IP address, as u32_t (instead of ip_addr_t to |
| * better check for failure: != IPADDR_NONE) or IPADDR_NONE if the hostname |
| * was not found in the cached dns_table. |
| */ |
| static u32_t |
| dns_lookup(const char *name) |
| { |
| u8_t i; |
| #if DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN) |
| u32_t addr; |
| #endif /* DNS_LOCAL_HOSTLIST || defined(DNS_LOOKUP_LOCAL_EXTERN) */ |
| #if DNS_LOCAL_HOSTLIST |
| if ((addr = dns_lookup_local(name)) != IPADDR_NONE) { |
| return addr; |
| } |
| #endif /* DNS_LOCAL_HOSTLIST */ |
| #ifdef DNS_LOOKUP_LOCAL_EXTERN |
| if((addr = DNS_LOOKUP_LOCAL_EXTERN(name)) != IPADDR_NONE) { |
| return addr; |
| } |
| #endif /* DNS_LOOKUP_LOCAL_EXTERN */ |
| |
| /* Walk through name list, return entry if found. If not, return NULL. */ |
| for (i = 0; i < DNS_TABLE_SIZE; ++i) { |
| if ((dns_table[i].state == DNS_STATE_DONE) && |
| (strcmp(name, dns_table[i].name) == 0)) { |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_lookup: \"%s\": found = ", name)); |
| ip_addr_debug_print(DNS_DEBUG, &(dns_table[i].ipaddr)); |
| LWIP_DEBUGF(DNS_DEBUG, ("\n")); |
| return ip4_addr_get_u32(&dns_table[i].ipaddr); |
| } |
| } |
| |
| return IPADDR_NONE; |
| } |
| |
| #if DNS_DOES_NAME_CHECK |
| /** |
| * Compare the "dotted" name "query" with the encoded name "response" |
| * to make sure an answer from the DNS server matches the current dns_table |
| * entry (otherwise, answers might arrive late for hostname not on the list |
| * any more). |
| * |
| * @param query hostname (not encoded) from the dns_table |
| * @param response encoded hostname in the DNS response |
| * @return 0: names equal; 1: names differ |
| */ |
| static u8_t |
| dns_compare_name(unsigned char *query, unsigned char *response) |
| { |
| unsigned char n; |
| |
| do { |
| n = *response++; |
| /** @see RFC 1035 - 4.1.4. Message compression */ |
| if ((n & 0xc0) == 0xc0) { |
| /* Compressed name */ |
| break; |
| } else { |
| /* Not compressed name */ |
| while (n > 0) { |
| if ((*query) != (*response)) { |
| return 1; |
| } |
| ++response; |
| ++query; |
| --n; |
| }; |
| ++query; |
| } |
| } while (*response != 0); |
| |
| return 0; |
| } |
| #endif /* DNS_DOES_NAME_CHECK */ |
| |
| /** |
| * Walk through a compact encoded DNS name and return the end of the name. |
| * |
| * @param query encoded DNS name in the DNS server response |
| * @return end of the name |
| */ |
| static unsigned char * |
| dns_parse_name(unsigned char *query) |
| { |
| unsigned char n; |
| |
| do { |
| n = *query++; |
| /** @see RFC 1035 - 4.1.4. Message compression */ |
| if ((n & 0xc0) == 0xc0) { |
| /* Compressed name */ |
| break; |
| } else { |
| /* Not compressed name */ |
| while (n > 0) { |
| ++query; |
| --n; |
| }; |
| } |
| } while (*query != 0); |
| |
| return query + 1; |
| } |
| |
| /** |
| * Send a DNS query packet. |
| * |
| * @param numdns index of the DNS server in the dns_servers table |
| * @param name hostname to query |
| * @param id index of the hostname in dns_table, used as transaction ID in the |
| * DNS query packet |
| * @return ERR_OK if packet is sent; an err_t indicating the problem otherwise |
| */ |
| static err_t |
| dns_send(u8_t numdns, const char* name, u8_t id) |
| { |
| err_t err; |
| struct dns_hdr *hdr; |
| struct dns_query qry; |
| struct pbuf *p; |
| char *query, *nptr; |
| const char *pHostname; |
| u8_t n; |
| |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_send: dns_servers[%"U16_F"] \"%s\": request\n", |
| (u16_t)(numdns), name)); |
| LWIP_ASSERT("dns server out of array", numdns < DNS_MAX_SERVERS); |
| LWIP_ASSERT("dns server has no IP address set", !ip_addr_isany(&dns_servers[numdns])); |
| |
| /* if here, we have either a new query or a retry on a previous query to process */ |
| p = pbuf_alloc(PBUF_TRANSPORT, SIZEOF_DNS_HDR + DNS_MAX_NAME_LENGTH + |
| SIZEOF_DNS_QUERY, PBUF_RAM); |
| if (p != NULL) { |
| LWIP_ASSERT("pbuf must be in one piece", p->next == NULL); |
| /* fill dns header */ |
| hdr = (struct dns_hdr*)p->payload; |
| memset(hdr, 0, SIZEOF_DNS_HDR); |
| hdr->id = htons(id); |
| hdr->flags1 = DNS_FLAG1_RD; |
| hdr->numquestions = PP_HTONS(1); |
| query = (char*)hdr + SIZEOF_DNS_HDR; |
| pHostname = name; |
| --pHostname; |
| |
| /* convert hostname into suitable query format. */ |
| do { |
| ++pHostname; |
| nptr = query; |
| ++query; |
| for(n = 0; *pHostname != '.' && *pHostname != 0; ++pHostname) { |
| *query = *pHostname; |
| ++query; |
| ++n; |
| } |
| *nptr = n; |
| } while(*pHostname != 0); |
| *query++='\0'; |
| |
| /* fill dns query */ |
| qry.type = PP_HTONS(DNS_RRTYPE_A); |
| qry.cls = PP_HTONS(DNS_RRCLASS_IN); |
| SMEMCPY(query, &qry, SIZEOF_DNS_QUERY); |
| |
| /* resize pbuf to the exact dns query */ |
| pbuf_realloc(p, (u16_t)((query + SIZEOF_DNS_QUERY) - ((char*)(p->payload)))); |
| |
| /* connect to the server for faster receiving */ |
| udp_connect(dns_pcb, &dns_servers[numdns], DNS_SERVER_PORT); |
| /* send dns packet */ |
| err = udp_sendto(dns_pcb, p, &dns_servers[numdns], DNS_SERVER_PORT); |
| |
| /* free pbuf */ |
| pbuf_free(p); |
| } else { |
| err = ERR_MEM; |
| } |
| |
| return err; |
| } |
| |
| /** |
| * dns_check_entry() - see if pEntry has not yet been queried and, if so, sends out a query. |
| * Check an entry in the dns_table: |
| * - send out query for new entries |
| * - retry old pending entries on timeout (also with different servers) |
| * - remove completed entries from the table if their TTL has expired |
| * |
| * @param i index of the dns_table entry to check |
| */ |
| static void |
| dns_check_entry(u8_t i) |
| { |
| err_t err; |
| struct dns_table_entry *pEntry = &dns_table[i]; |
| |
| LWIP_ASSERT("array index out of bounds", i < DNS_TABLE_SIZE); |
| |
| switch(pEntry->state) { |
| |
| case DNS_STATE_NEW: { |
| /* initialize new entry */ |
| pEntry->state = DNS_STATE_ASKING; |
| pEntry->numdns = 0; |
| pEntry->tmr = 1; |
| pEntry->retries = 0; |
| |
| /* send DNS packet for this entry */ |
| err = dns_send(pEntry->numdns, pEntry->name, i); |
| if (err != ERR_OK) { |
| LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING, |
| ("dns_send returned error: %s\n", lwip_strerr(err))); |
| } |
| break; |
| } |
| |
| case DNS_STATE_ASKING: { |
| if (--pEntry->tmr == 0) { |
| if (++pEntry->retries == DNS_MAX_RETRIES) { |
| if ((pEntry->numdns+1<DNS_MAX_SERVERS) && !ip_addr_isany(&dns_servers[pEntry->numdns+1])) { |
| /* change of server */ |
| pEntry->numdns++; |
| pEntry->tmr = 1; |
| pEntry->retries = 0; |
| break; |
| } else { |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": timeout\n", pEntry->name)); |
| /* call specified callback function if provided */ |
| if (pEntry->found) |
| (*pEntry->found)(pEntry->name, NULL, pEntry->arg); |
| /* flush this entry */ |
| pEntry->state = DNS_STATE_UNUSED; |
| pEntry->found = NULL; |
| break; |
| } |
| } |
| |
| /* wait longer for the next retry */ |
| pEntry->tmr = pEntry->retries; |
| |
| /* send DNS packet for this entry */ |
| err = dns_send(pEntry->numdns, pEntry->name, i); |
| if (err != ERR_OK) { |
| LWIP_DEBUGF(DNS_DEBUG | LWIP_DBG_LEVEL_WARNING, |
| ("dns_send returned error: %s\n", lwip_strerr(err))); |
| } |
| } |
| break; |
| } |
| |
| case DNS_STATE_DONE: { |
| /* if the time to live is nul */ |
| if (--pEntry->ttl == 0) { |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_check_entry: \"%s\": flush\n", pEntry->name)); |
| /* flush this entry */ |
| pEntry->state = DNS_STATE_UNUSED; |
| pEntry->found = NULL; |
| } |
| break; |
| } |
| case DNS_STATE_UNUSED: |
| /* nothing to do */ |
| break; |
| default: |
| LWIP_ASSERT("unknown dns_table entry state:", 0); |
| break; |
| } |
| } |
| |
| /** |
| * Call dns_check_entry for each entry in dns_table - check all entries. |
| */ |
| static void |
| dns_check_entries(void) |
| { |
| u8_t i; |
| |
| for (i = 0; i < DNS_TABLE_SIZE; ++i) { |
| dns_check_entry(i); |
| } |
| } |
| |
| /** |
| * Receive input function for DNS response packets arriving for the dns UDP pcb. |
| * |
| * @params see udp.h |
| */ |
| static void |
| dns_recv(void *arg, struct udp_pcb *pcb, struct pbuf *p, ip_addr_t *addr, u16_t port) |
| { |
| u16_t i; |
| char *pHostname; |
| struct dns_hdr *hdr; |
| struct dns_answer ans; |
| struct dns_table_entry *pEntry; |
| u16_t nquestions, nanswers; |
| |
| LWIP_UNUSED_ARG(arg); |
| LWIP_UNUSED_ARG(pcb); |
| LWIP_UNUSED_ARG(addr); |
| LWIP_UNUSED_ARG(port); |
| |
| /* is the dns message too big ? */ |
| if (p->tot_len > DNS_MSG_SIZE) { |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too big\n")); |
| /* free pbuf and return */ |
| goto memerr; |
| } |
| |
| /* is the dns message big enough ? */ |
| if (p->tot_len < (SIZEOF_DNS_HDR + SIZEOF_DNS_QUERY + SIZEOF_DNS_ANSWER)) { |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: pbuf too small\n")); |
| /* free pbuf and return */ |
| goto memerr; |
| } |
| |
| /* copy dns payload inside static buffer for processing */ |
| if (pbuf_copy_partial(p, dns_payload, p->tot_len, 0) == p->tot_len) { |
| /* The ID in the DNS header should be our entry into the name table. */ |
| hdr = (struct dns_hdr*)dns_payload; |
| i = htons(hdr->id); |
| if (i < DNS_TABLE_SIZE) { |
| pEntry = &dns_table[i]; |
| if(pEntry->state == DNS_STATE_ASKING) { |
| /* This entry is now completed. */ |
| pEntry->state = DNS_STATE_DONE; |
| pEntry->err = hdr->flags2 & DNS_FLAG2_ERR_MASK; |
| |
| /* We only care about the question(s) and the answers. The authrr |
| and the extrarr are simply discarded. */ |
| nquestions = htons(hdr->numquestions); |
| nanswers = htons(hdr->numanswers); |
| |
| /* Check for error. If so, call callback to inform. */ |
| if (((hdr->flags1 & DNS_FLAG1_RESPONSE) == 0) || (pEntry->err != 0) || (nquestions != 1)) { |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in flags\n", pEntry->name)); |
| /* call callback to indicate error, clean up memory and return */ |
| goto responseerr; |
| } |
| |
| #if DNS_DOES_NAME_CHECK |
| /* Check if the name in the "question" part match with the name in the entry. */ |
| if (dns_compare_name((unsigned char *)(pEntry->name), (unsigned char *)dns_payload + SIZEOF_DNS_HDR) != 0) { |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response not match to query\n", pEntry->name)); |
| /* call callback to indicate error, clean up memory and return */ |
| goto responseerr; |
| } |
| #endif /* DNS_DOES_NAME_CHECK */ |
| |
| /* Skip the name in the "question" part */ |
| pHostname = (char *) dns_parse_name((unsigned char *)dns_payload + SIZEOF_DNS_HDR) + SIZEOF_DNS_QUERY; |
| |
| while (nanswers > 0) { |
| /* skip answer resource record's host name */ |
| pHostname = (char *) dns_parse_name((unsigned char *)pHostname); |
| |
| /* Check for IP address type and Internet class. Others are discarded. */ |
| SMEMCPY(&ans, pHostname, SIZEOF_DNS_ANSWER); |
| if((ans.type == PP_HTONS(DNS_RRTYPE_A)) && (ans.cls == PP_HTONS(DNS_RRCLASS_IN)) && |
| (ans.len == PP_HTONS(sizeof(ip_addr_t))) ) { |
| /* read the answer resource record's TTL, and maximize it if needed */ |
| pEntry->ttl = ntohl(ans.ttl); |
| if (pEntry->ttl > DNS_MAX_TTL) { |
| pEntry->ttl = DNS_MAX_TTL; |
| } |
| /* read the IP address after answer resource record's header */ |
| SMEMCPY(&(pEntry->ipaddr), (pHostname+SIZEOF_DNS_ANSWER), sizeof(ip_addr_t)); |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": response = ", pEntry->name)); |
| ip_addr_debug_print(DNS_DEBUG, (&(pEntry->ipaddr))); |
| LWIP_DEBUGF(DNS_DEBUG, ("\n")); |
| /* call specified callback function if provided */ |
| if (pEntry->found) { |
| (*pEntry->found)(pEntry->name, &pEntry->ipaddr, pEntry->arg); |
| } |
| /* deallocate memory and return */ |
| goto memerr; |
| } else { |
| pHostname = pHostname + SIZEOF_DNS_ANSWER + htons(ans.len); |
| } |
| --nanswers; |
| } |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_recv: \"%s\": error in response\n", pEntry->name)); |
| /* call callback to indicate error, clean up memory and return */ |
| goto responseerr; |
| } |
| } |
| } |
| |
| /* deallocate memory and return */ |
| goto memerr; |
| |
| responseerr: |
| /* ERROR: call specified callback function with NULL as name to indicate an error */ |
| if (pEntry->found) { |
| (*pEntry->found)(pEntry->name, NULL, pEntry->arg); |
| } |
| /* flush this entry */ |
| pEntry->state = DNS_STATE_UNUSED; |
| pEntry->found = NULL; |
| |
| memerr: |
| /* free pbuf */ |
| pbuf_free(p); |
| return; |
| } |
| |
| /** |
| * Queues a new hostname to resolve and sends out a DNS query for that hostname |
| * |
| * @param name the hostname that is to be queried |
| * @param found a callback founction to be called on success, failure or timeout |
| * @param callback_arg argument to pass to the callback function |
| * @return @return a err_t return code. |
| */ |
| static err_t |
| dns_enqueue(const char *name, dns_found_callback found, void *callback_arg) |
| { |
| u8_t i; |
| u8_t lseq, lseqi; |
| struct dns_table_entry *pEntry = NULL; |
| size_t namelen; |
| |
| /* search an unused entry, or the oldest one */ |
| lseq = lseqi = 0; |
| for (i = 0; i < DNS_TABLE_SIZE; ++i) { |
| pEntry = &dns_table[i]; |
| /* is it an unused entry ? */ |
| if (pEntry->state == DNS_STATE_UNUSED) |
| break; |
| |
| /* check if this is the oldest completed entry */ |
| if (pEntry->state == DNS_STATE_DONE) { |
| if ((dns_seqno - pEntry->seqno) > lseq) { |
| lseq = dns_seqno - pEntry->seqno; |
| lseqi = i; |
| } |
| } |
| } |
| |
| /* if we don't have found an unused entry, use the oldest completed one */ |
| if (i == DNS_TABLE_SIZE) { |
| if ((lseqi >= DNS_TABLE_SIZE) || (dns_table[lseqi].state != DNS_STATE_DONE)) { |
| /* no entry can't be used now, table is full */ |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": DNS entries table is full\n", name)); |
| return ERR_MEM; |
| } else { |
| /* use the oldest completed one */ |
| i = lseqi; |
| pEntry = &dns_table[i]; |
| } |
| } |
| |
| /* use this entry */ |
| LWIP_DEBUGF(DNS_DEBUG, ("dns_enqueue: \"%s\": use DNS entry %"U16_F"\n", name, (u16_t)(i))); |
| |
| /* fill the entry */ |
| pEntry->state = DNS_STATE_NEW; |
| pEntry->seqno = dns_seqno++; |
| pEntry->found = found; |
| pEntry->arg = callback_arg; |
| namelen = LWIP_MIN(strlen(name), DNS_MAX_NAME_LENGTH-1); |
| MEMCPY(pEntry->name, name, namelen); |
| pEntry->name[namelen] = 0; |
| |
| /* force to send query without waiting timer */ |
| dns_check_entry(i); |
| |
| /* dns query is enqueued */ |
| return ERR_INPROGRESS; |
| } |
| |
| /** |
| * Resolve a hostname (string) into an IP address. |
| * NON-BLOCKING callback version for use with raw API!!! |
| * |
| * Returns immediately with one of err_t return codes: |
| * - ERR_OK if hostname is a valid IP address string or the host |
| * name is already in the local names table. |
| * - ERR_INPROGRESS enqueue a request to be sent to the DNS server |
| * for resolution if no errors are present. |
| * - ERR_ARG: dns client not initialized or invalid hostname |
| * |
| * @param hostname the hostname that is to be queried |
| * @param addr pointer to a ip_addr_t where to store the address if it is already |
| * cached in the dns_table (only valid if ERR_OK is returned!) |
| * @param found a callback function to be called on success, failure or timeout (only if |
| * ERR_INPROGRESS is returned!) |
| * @param callback_arg argument to pass to the callback function |
| * @return a err_t return code. |
| */ |
| err_t |
| dns_gethostbyname(const char *hostname, ip_addr_t *addr, dns_found_callback found, |
| void *callback_arg) |
| { |
| u32_t ipaddr; |
| /* not initialized or no valid server yet, or invalid addr pointer |
| * or invalid hostname or invalid hostname length */ |
| if ((dns_pcb == NULL) || (addr == NULL) || |
| (!hostname) || (!hostname[0]) || |
| (strlen(hostname) >= DNS_MAX_NAME_LENGTH)) { |
| return ERR_ARG; |
| } |
| |
| #if LWIP_HAVE_LOOPIF |
| if (strcmp(hostname, "localhost")==0) { |
| ip_addr_set_loopback(addr); |
| return ERR_OK; |
| } |
| #endif /* LWIP_HAVE_LOOPIF */ |
| |
| /* host name already in octet notation? set ip addr and return ERR_OK */ |
| ipaddr = ipaddr_addr(hostname); |
| if (ipaddr == IPADDR_NONE) { |
| /* already have this address cached? */ |
| ipaddr = dns_lookup(hostname); |
| } |
| if (ipaddr != IPADDR_NONE) { |
| ip4_addr_set_u32(addr, ipaddr); |
| return ERR_OK; |
| } |
| |
| /* queue query with specified callback */ |
| return dns_enqueue(hostname, found, callback_arg); |
| } |
| |
| #endif /* LWIP_DNS */ |