Add cache feature

src/dns_cache.h

@@ -0,0 +1,41 @@
+#ifndef _SMARTDNS_CACHE_H
+#define _SMARTDNS_CACHE_H
+
+#include "dns.h"
+#include "hashtable.h"
+#include "hash.h"
+#include "list.h"
+#include "atomic.h"
+
+struct dns_cache {
+	struct hlist_node node;
+	struct list_head list;
+	atomic_t ref;
+	char domain[DNS_MAX_CNAME_LEN];
+	unsigned ttl;
+	time_t insert_time;
+	dns_type_t qtype;
+	union {
+		unsigned char ipv4_addr[DNS_RR_A_LEN];
+		unsigned char ipv6_addr[DNS_RR_AAAA_LEN];
+		unsigned char addr[0];
+	};
+};
+
+int dns_cache_init(int size);
+
+int dns_cache_insert(char *domain, int ttl, dns_type_t qtype, unsigned char *addr, int addr_len);
+
+struct dns_cache *dns_cache_get(char *domain, dns_type_t qtype);
+
+void dns_cache_delete(struct dns_cache *dns_cache);
+
+void dns_cache_release(struct dns_cache *dns_cache);
+
+void dns_cache_update(struct dns_cache *dns_cache);
+
+int dns_cache_get_ttl(struct dns_cache *dns_cache);
+
+void dns_cache_destroy(void);
+
+#endif // !_SMARTDNS_CACHE_H