1 /** @file 2 * @brief DNS cache 3 * 4 * An cache holding dns records for faster dns resolving. 5 */ 6 7 /* 8 * Copyright (c) 2024 Endress+Hauser AG 9 * 10 * SPDX-License-Identifier: Apache-2.0 11 */ 12 13 #ifndef ZEPHYR_INCLUDE_NET_DNS_CACHE_H_ 14 #define ZEPHYR_INCLUDE_NET_DNS_CACHE_H_ 15 16 #include <stdint.h> 17 #include <zephyr/net/dns_resolve.h> 18 #include <zephyr/kernel.h> 19 #include <zephyr/sys_clock.h> 20 21 struct dns_cache_entry { 22 char query[CONFIG_DNS_RESOLVER_MAX_QUERY_LEN]; 23 struct dns_addrinfo data; 24 k_timepoint_t expiry; 25 bool in_use; 26 }; 27 28 struct dns_cache { 29 size_t size; 30 struct dns_cache_entry *entries; 31 struct k_mutex *lock; 32 }; 33 34 /** 35 * @brief Statically define and initialize a DNS queue. 36 * 37 * The cache can be accessed outside the module where it is defined using: 38 * 39 * @code extern struct dns_cache <name>; @endcode 40 * 41 * @param name Name of the cache. 42 */ 43 #define DNS_CACHE_DEFINE(name, cache_size) \ 44 static K_MUTEX_DEFINE(name##_mutex); \ 45 static struct dns_cache_entry name##_entries[cache_size]; \ 46 static struct dns_cache name = { \ 47 .entries = name##_entries, .size = cache_size, .lock = &name##_mutex}; 48 49 /** 50 * @brief Flushes the dns cache removing all its entries. 51 * 52 * @param cache Cache to be flushed 53 * @retval 0 on success 54 * @retval On error, a negative value is returned. 55 */ 56 int dns_cache_flush(struct dns_cache *cache); 57 58 /** 59 * @brief Adds a new entry to the dns cache removing the one closest to expiry 60 * if no free space is available. 61 * 62 * @param cache Cache where the entry should be added. 63 * @param query Query which should be persisted in the cache. 64 * @param addrinfo Addrinfo resulting from the query which will be returned 65 * upon cache hit. 66 * @param ttl Time to live for the entry in seconds. This usually represents 67 * the TTL of the RR. 68 * @retval 0 on success 69 * @retval On error, a negative value is returned. 70 */ 71 int dns_cache_add(struct dns_cache *cache, char const *query, struct dns_addrinfo const *addrinfo, 72 uint32_t ttl); 73 74 /** 75 * @brief Removes all entries with the given query 76 * 77 * @param cache Cache where the entries should be removed. 78 * @param query Query which should be searched for. 79 * @retval 0 on success 80 * @retval On error, a negative value is returned. 81 */ 82 int dns_cache_remove(struct dns_cache *cache, char const *query); 83 84 /** 85 * @brief Tries to find the specified query entry within the cache. 86 * 87 * @param cache Cache where the entry should be searched. 88 * @param query Query which should be searched for. 89 * @param addrinfo dns_addrinfo array which will be written if the query was found. 90 * @param addrinfo_array_len Array size of the dns_addrinfo array 91 * @retval on success the amount of dns_addrinfo written into the addrinfo array will be returned. 92 * A cache miss will therefore return a 0. 93 * @retval On error a negative value is returned. 94 * -ENOSR means there was not enough space in the addrinfo array to accommodate all cache hits the 95 * array will however be filled with valid data. 96 */ 97 int dns_cache_find(struct dns_cache const *cache, const char *query, struct dns_addrinfo *addrinfo, 98 size_t addrinfo_array_len); 99 100 #endif /* ZEPHYR_INCLUDE_NET_DNS_CACHE_H_ */ 101
