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EthernetNetIf Compatibility.
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by 
Donatien Garnier
Diff: lwip/core/dns.c
- Revision:
- 2:a4f97773c90f
- Parent:
- 0:632c9925f013
- Child:
- 5:dd63a1e02b1b
diff -r abb442332fa8 -r a4f97773c90f lwip/core/dns.c
--- a/lwip/core/dns.c Mon Jun 14 10:33:54 2010 +0000
+++ b/lwip/core/dns.c Fri Jun 18 09:22:54 2010 +0000
@@ -1,968 +1,970 @@
-/**
- * @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/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. */
-PACK_STRUCT_BEGIN
-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;
-} PACK_STRUCT_STRUCT;
-PACK_STRUCT_END
-#define SIZEOF_DNS_QUERY 4
-
-/** DNS answer message structure.
- No packing needed: only used locally on the stack. */
-PACK_STRUCT_BEGIN
-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;
-} PACK_STRUCT_STRUCT;
-PACK_STRUCT_END
-#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
-/** struct used for local host-list */
-struct local_hostlist_entry {
- /** static hostname */
- const char *name;
- /** static host address in network byteorder */
- ip_addr_t addr;
- struct local_hostlist_entry *next;
-};
-
-#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);
- entry = mem_malloc((mem_size_t)(sizeof(struct local_hostlist_entry) + namelen + 1));
- 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;
- mem_free(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);
- entry = mem_malloc((mem_size_t)(sizeof(struct local_hostlist_entry) + namelen + 1));
- 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 = 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 = htons(DNS_RRTYPE_A);
- qry.cls = 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)
-{
- 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 */
- dns_send(pEntry->numdns, pEntry->name, i);
- 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 */
- dns_send(pEntry->numdns, pEntry->name, i);
- }
- 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 == htons(DNS_RRTYPE_A)) && (ans.cls == htons(DNS_RRCLASS_IN)) &&
- (ans.len == 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.
- *
- * @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_VAL;
- }
-
-#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 */
+/**
+ * @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 "lwip/debug.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: %d\n", 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: %d\n", 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.
+ *
+ * @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_VAL;
+ }
+
+#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 */