Diff: lwip/core/dns.c

Revision:

1:9d93f4dc2f46

Parent:

0:8b387bed54c2

--- a/lwip/core/dns.c	Mon Jan 10 21:03:11 2011 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,969 +0,0 @@
-/**
- * @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: %d\n", err)); //FIX DG, lwip_strerr is part of lwip/api
-      }
-      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)); //FIX DG, lwip_strerr is part of lwip/api
-        }
-      }
-      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 */