+#include "socket.h"
+#include "hashcomp.h"
+
+/**
+ * Result status, used internally
+ */
+class CoreExport DNSResult
+{
+ public:
+ /** Result ID
+ */
+ int id;
+ /** Result body, a hostname or IP address
+ */
+ std::string result;
+ /** Time-to-live value of the result
+ */
+ unsigned long ttl;
+ /** The original request, a hostname or IP address
+ */
+ std::string original;
+
+ /** Build a DNS result.
+ * @param i The request ID
+ * @param res The request result, a hostname or IP
+ * @param timetolive The request time-to-live
+ * @param orig The original request, a hostname or IP
+ */
+ DNSResult(int i, const std::string &res, unsigned long timetolive, const std::string &orig) : id(i), result(res), ttl(timetolive), original(orig) { }
+};
+
+/**
+ * Information on a completed lookup, used internally
+ */
+typedef std::pair<unsigned char*, std::string> DNSInfo;
+
+/** Cached item stored in the query cache.
+ */
+class CoreExport CachedQuery
+{
+ public:
+ /** The cached result data, an IP or hostname
+ */
+ std::string data;
+ /** The time when the item is due to expire
+ */
+ time_t expires;
+
+ /** Build a cached query
+ * @param res The result data, an IP or hostname
+ * @param ttl The time-to-live value of the query result
+ */
+ CachedQuery(const std::string &res, unsigned int ttl);
+
+ /** Returns the number of seconds remaining before this
+ * cache item has expired and should be removed.
+ */
+ int CalcTTLRemaining();
+};
+
+/** DNS cache information. Holds IPs mapped to hostnames, and hostnames mapped to IPs.
+ */
+#if defined(WINDOWS) && !defined(HASHMAP_DEPRECATED)
+typedef nspace::hash_map<irc::string, CachedQuery, nspace::hash_compare<irc::string> > dnscache;
+#else
+typedef nspace::hash_map<irc::string, CachedQuery, irc::hash> dnscache;
+#endif
+
+/**
+ * Error types that class Resolver can emit to its error method.
+ */
+enum ResolverError
+{
+ RESOLVER_NOERROR = 0,
+ RESOLVER_NSDOWN = 1,
+ RESOLVER_NXDOMAIN = 2,
+ RESOLVER_BADIP = 3,
+ RESOLVER_TIMEOUT = 4,
+ RESOLVER_FORCEUNLOAD = 5
+};
+
+/**
+ * Query and resource record types
+ */
+enum QueryType
+{
+ /** Uninitialized Query */
+ DNS_QUERY_NONE = 0,
+ /** 'A' record: an ipv4 address */
+ DNS_QUERY_A = 1,
+ /** 'CNAME' record: An alias */
+ DNS_QUERY_CNAME = 5,
+ /** 'PTR' record: a hostname */
+ DNS_QUERY_PTR = 12,
+ /** 'AAAA' record: an ipv6 address */
+ DNS_QUERY_AAAA = 28,
+
+ /** Force 'PTR' to use IPV4 scemantics */
+ DNS_QUERY_PTR4 = 0xFFFD,
+ /** Force 'PTR' to use IPV6 scemantics */
+ DNS_QUERY_PTR6 = 0xFFFE
+};
+
+/**
+ * Used internally to force PTR lookups to use a certain protocol scemantics,
+ * e.g. x.x.x.x.in-addr.arpa for v4, and *.ip6.arpa for v6.
+ */
+enum ForceProtocol
+{
+ /** Forced to use ipv4 */
+ PROTOCOL_IPV4 = 0,
+ /** Forced to use ipv6 */
+ PROTOCOL_IPV6 = 1
+};
+
+/**
+ * The Resolver class is a high-level abstraction for resolving DNS entries.
+ * It can do forward and reverse IPv4 lookups, and where IPv6 is supported, will
+ * also be able to do those, transparent of protocols. Module developers must
+ * extend this class via inheritence, and then insert a pointer to their derived
+ * class into the core using Server::AddResolver(). Once you have done this,
+ * the class will be able to receive callbacks. There are two callbacks which
+ * can occur by calling virtual methods, one is a success situation, and the other
+ * an error situation.
+ */
+class CoreExport Resolver
+{
+ protected:
+ /**
+ * Pointer to creator module (if any, or NULL)
+ */
+ ModuleRef Creator;
+ /**
+ * The input data, either a host or an IP address
+ */
+ std::string input;
+ /**
+ * True if a forward lookup is being performed, false if otherwise
+ */
+ QueryType querytype;
+ /**
+ * The DNS erver being used for lookups. If this is an empty string,
+ * the value of ServerConfig::DNSServer is used instead.
+ */
+ std::string server;
+ /**
+ * The ID allocated to your lookup. This is a pseudo-random number
+ * between 0 and 65535, a value of -1 indicating a failure.
+ * The core uses this to route results to the correct objects.
+ */
+ int myid;
+
+ /**
+ * Cached result, if there is one
+ */
+ CachedQuery *CQ;
+
+ /**
+ * Time left before cache expiry
+ */
+ int time_left;
+
+ public:
+ /**
+ * Initiate DNS lookup. Your class should not attempt to delete or free these
+ * objects, as the core will do this for you. They must always be created upon
+ * the heap using new, as you cannot be sure at what time they will be deleted.
+ * Allocating them on the stack or attempting to delete them yourself could cause
+ * the object to go 'out of scope' and cause a segfault in the core if the result
+ * arrives at a later time.
+ * @param source The IP or hostname to resolve
+ * @param qt The query type to perform. Resolution of 'A', 'AAAA', 'PTR' and 'CNAME' records
+ * is supported. Use one of the QueryType enum values to initiate this type of
+ * lookup. Resolution of 'AAAA' ipv6 records is always supported, regardless of
+ * wether InspIRCd is built with ipv6 support.
+ * To look up reverse records, specify one of DNS_QUERY_PTR4 or DNS_QUERY_PTR6 depending
+ * on the type of address you are looking up.
+ * @param cached The constructor will set this boolean to true or false depending
+ * on whether the DNS lookup you are attempting is cached (and not expired) or not.
+ * If the value is cached, upon return this will be set to true, otherwise it will
+ * be set to false. You should pass this value to InspIRCd::AddResolver(), which
+ * will then influence the behaviour of the method and determine whether a cached
+ * or non-cached result is obtained. The value in this variable is always correct
+ * for the given request when the constructor exits.
+ * @param creator See the note below.
+ * @throw ModuleException This class may throw an instance of ModuleException, in the
+ * event a lookup could not be allocated, or a similar hard error occurs such as
+ * the network being down. This will also be thrown if an invalid IP address is
+ * passed when resolving a 'PTR' record.
+ *
+ * NOTE: If you are instantiating your DNS lookup from a module, you should set the
+ * value of creator to point at your Module class. This way if your module is unloaded
+ * whilst lookups are in progress, they can be safely removed and your module will not
+ * crash the server.
+ */
+ Resolver(const std::string &source, QueryType qt, bool &cached, Module* creator);
+
+ /**
+ * The default destructor does nothing.
+ */
+ virtual ~Resolver();
+
+ /**
+ * When your lookup completes, this method will be called.
+ * @param result The resulting DNS lookup, either an IP address or a hostname.
+ * @param ttl The time-to-live value of the result, in the instance of a cached
+ * result, this is the number of seconds remaining before refresh/expiry.
+ * @param cached True if the result is a cached result, false if it was requested
+ * from the DNS server.
+ */
+ virtual void OnLookupComplete(const std::string &result, unsigned int ttl, bool cached) = 0;
+
+ /**
+ * If an error occurs (such as NXDOMAIN, no domain name found) then this method
+ * will be called.
+ * @param e A ResolverError enum containing the error type which has occured.
+ * @param errormessage The error text of the error that occured.
+ */
+ virtual void OnError(ResolverError e, const std::string &errormessage);
+
+ /**
+ * Returns the id value of this class. This is primarily used by the core
+ * to determine where in various tables to place a pointer to your class, but it
+ * is safe to call and use this method.
+ * As specified in RFC1035, each dns request has a 16 bit ID value, ranging
+ * from 0 to 65535. If there is an issue and the core cannot send your request,
+ * this method will return -1.
+ */
+ int GetId();