dns_cache.h

Go to the documentation of this file.

/**
 * @file dns_cache.h
 * @brief DNS cache management
 *
 * @section License
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 *
 * Copyright (C) 2010-2026 Oryx Embedded SARL. All rights reserved.
 *
 * This file is part of CycloneTCP Open.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * @author Oryx Embedded SARL (www.oryx-embedded.com)
 * @version 2.6.6
 **/
 
#ifndef _DNS_CACHE_H
#define _DNS_CACHE_H
 
//Dependencies
#include "core/net.h"
#include "core/socket.h"
 
//DNS tick interval
#ifndef DNS_TICK_INTERVAL
   #define DNS_TICK_INTERVAL 200
#elif (DNS_TICK_INTERVAL < 10)
   #error DNS_TICK_INTERVAL parameter is not valid
#endif
 
//Size of DNS cache
#ifndef DNS_CACHE_SIZE
   #define DNS_CACHE_SIZE 8
#elif (DNS_CACHE_SIZE < 1)
   #error DNS_CACHE_SIZE parameter is not valid
#endif
 
//Maximum length of domain names
#ifndef DNS_MAX_NAME_LEN
   #define DNS_MAX_NAME_LEN 63
#elif (DNS_MAX_NAME_LEN < 1)
   #error DNS_MAX_NAME_LEN parameter is not valid
#endif
 
//Initial polling interval
#ifndef DNS_CACHE_INIT_POLLING_INTERVAL
   #define DNS_CACHE_INIT_POLLING_INTERVAL 10
#elif (DNS_CACHE_INIT_POLLING_INTERVAL < 1)
   #error DNS_CACHE_INIT_POLLING_INTERVAL parameter is not valid
#endif
 
//Maximum polling interval
#ifndef DNS_CACHE_MAX_POLLING_INTERVAL
   #define DNS_CACHE_MAX_POLLING_INTERVAL 1000
#elif (DNS_CACHE_MAX_POLLING_INTERVAL < 10)
   #error DNS_CACHE_MAX_POLLING_INTERVAL parameter is not valid
#endif
 
//C++ guard
#ifdef __cplusplus
extern "C" {
#endif
 
 
/**
 * @brief DNS cache entry states
 **/
 
typedef enum
{
   DNS_STATE_NONE        = 0,
   DNS_STATE_IN_PROGRESS = 1,
   DNS_STATE_RESOLVED    = 2,
   DNS_STATE_FAILED      = 3,
   DNS_STATE_PERMANENT   = 4
} DnsState;
 
 
/**
 * @brief DNS cache entry
 **/
 
typedef struct
{
   DnsState state;                    ///<Entry state
   uint_t refCount;                   ///<Reference count for the current entry
   HostType type;                     ///<IPv4 or IPv6 host?
   HostnameResolver protocol;         ///<Name resolution protocol
   NetInterface *interface;           ///<Underlying network interface
   uint_t dnsServerIndex;             ///<This parameter selects between the primary and secondary DNS server
   uint16_t port;                     ///<Port number used by the resolver
   uint16_t id;                       ///<Identifier used to match queries and responses
   char_t name[DNS_MAX_NAME_LEN + 1]; ///<Domain name
   IpAddr ipAddr;                     ///<IP address
   systime_t timestamp;               ///<Timestamp to manage entry lifetime
   systime_t timeout;                 ///<Retransmission timeout
   systime_t maxTimeout;              ///<Maximum retransmission timeout
   uint_t retransmitCount;            ///<Retransmission counter
} DnsCacheEntry;
 
 
//DNS related functions
error_t dnsInit(NetContext *context);
 
void dnsFlushCache(NetInterface *interface);
 
DnsCacheEntry *dnsCreateEntry(NetContext *context);
void dnsDeleteEntry(DnsCacheEntry *entry);
 
DnsCacheEntry *dnsFindEntry(NetInterface *interface,
   const char_t *name, HostType type, HostnameResolver protocol);
 
void dnsTick(NetContext *context);
 
//C++ guard
#ifdef __cplusplus
}
#endif
 
#endif