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112 lines
2.7 KiB
C
112 lines
2.7 KiB
C
/*
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* Copyright (C) 2022 ML!PA Consulting GmbH
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @defgroup net_dns_cache DNS cache
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* @ingroup net_dns
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*
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* @brief DNS cache
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*
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* @{
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*
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* @file
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* @brief DNS cache definitions
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*
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* This implements a simple DNS cache for A and AAAA entries.
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*
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* The cache eviction strategy is based on the remaining time to live
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* of the cache entries, so the first entry to expire will be evicted.
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*
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* This is fine if there are only few cache entries and cache eviction
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* is unlikely.
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* If there is communication to many different hosts, the addition of a
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* least-recently used counter could likely improve the behavior.
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*
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* @author Benjamin Valentin <benjamin.valentin@ml-pa.com>
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*/
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#ifndef NET_DNS_CACHE_H
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#define NET_DNS_CACHE_H
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#include <stdint.h>
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#include "modules.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @brief Maximum number of DNS cache entries
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*/
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#ifndef CONFIG_DNS_CACHE_SIZE
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#define CONFIG_DNS_CACHE_SIZE 4
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#endif
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/**
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* @brief Handle to cache A records
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*/
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#ifndef CONFIG_DNS_CACHE_A
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#define CONFIG_DNS_CACHE_A IS_USED(MODULE_IPV4)
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#endif
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/**
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* @brief Handle to cache AAAA records
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*/
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#ifndef CONFIG_DNS_CACHE_AAAA
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#define CONFIG_DNS_CACHE_AAAA IS_USED(MODULE_IPV6)
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#endif
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#if IS_USED(MODULE_DNS_CACHE) || DOXYGEN
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/**
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* @brief Get IP address for a DNS name from the DNS cache
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*
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* @param[in] domain_name DNS name to resolve into address
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* @param[out] addr_out buffer to write result into
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* @param[in] family Either AF_INET, AF_INET6 or AF_UNSPEC
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*
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* @return the size of the resolved address on success
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* @return <= 0 otherwise
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*/
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int dns_cache_query(const char *domain_name, void *addr_out, int family);
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/**
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* @brief Add an IP address for a DNS name to the DNS cache
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*
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* @param[in] domain_name DNS name to resolve into address
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* @param[in] addr buffer containing the address
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* @param[in] addr_len length of the address in bytes
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* @param[in] ttl lifetime of the entry in seconds
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*/
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void dns_cache_add(const char *domain_name, const void *addr, int addr_len, uint32_t ttl);
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#else
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static inline int dns_cache_query(const char *domain_name, void *addr_out, int family)
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{
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(void)domain_name;
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(void)addr_out;
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(void)family;
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return 0;
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}
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static inline void dns_cache_add(const char *domain_name, const void *addr,
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int addr_len, uint32_t ttl)
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{
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(void)domain_name;
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(void)addr;
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(void)addr_len;
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(void)ttl;
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}
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#endif
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#ifdef __cplusplus
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}
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#endif
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#endif /* NET_DNS_CACHE_H */
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/** @} */
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