+/**
+ * An iterator into a set of requests
+ */
+typedef requestlist::iterator requestlist_iter;
+
+/**
+ * Query and resource record types
+ */
+enum QueryType
+{
+ DNS_QUERY_A = 1, /* 'A' record: an ipv4 address */
+ DNS_QUERY_CNAME = 5, /* 'CNAME' record: An alias */
+ DNS_QUERY_PTR = 12, /* 'PTR' record: a hostname */
+ DNS_QUERY_AAAA = 28, /* 'AAAA' record: an ipv6 address */
+
+ DNS_QUERY_PTR4 = 0xFFFD, /* Force 'PTR' to use IPV4 scemantics */
+ DNS_QUERY_PTR6 = 0xFFFE, /* Force 'PTR' to use IPV6 scemantics */
+};
+
+#ifdef IPV6
+const QueryType DNS_QUERY_FORWARD = DNS_QUERY_AAAA;
+const QueryType DNS_QUERY_REVERSE = DNS_QUERY_PTR;
+#else
+const QueryType DNS_QUERY_FORWARD = DNS_QUERY_A;
+const QueryType DNS_QUERY_REVERSE = DNS_QUERY_PTR;
+#endif
+
+/**
+ * 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
+{
+ PROTOCOL_IPV4 = 0, /* Forced to use ipv4 */
+ PROTOCOL_IPV6 = 1 /* Forced to use ipv6 */
+};
+
+/**
+ * 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 Resolver : public Extensible
+{
+ protected:
+ /**
+ * Pointer to creator
+ */
+ InspIRCd* ServerInstance;
+ /**
+ * 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;
+ 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. If you just want to perform a forward
+ * or reverse lookup, and you don't care wether you get ipv4 or ipv6, then use
+ * the constants DNS_QUERY_FORWARD and DNS_QUERY_REVERSE, which automatically
+ * select from 'A' record or 'AAAA' record lookups. However, if you want to resolve
+ * a specific record type, 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.
+ * If you attempt to resolve a 'PTR' record using DNS_QUERY_PTR, and InspIRCd is
+ * built with ipv6 support, the 'PTR' record will be formatted to ipv6 specs,
+ * e.g. x.x.x.x.x....ip6.arpa. otherwise it will be formatted to ipv4 specs,
+ * e.g. x.x.x.x.in-addr.arpa. This translation is automatic.
+ * To get around this automatic behaviour, you must use one of the values
+ * DNS_QUERY_PTR4 or DNS_QUERY_PTR6 to force ipv4 or ipv6 behaviour on the lookup,
+ * irrespective of what protocol InspIRCd has been built for.
+ * @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.
+ */
+ Resolver(InspIRCd* Instance, const std::string &source, QueryType qt);
+ /**
+ * 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.
+ */
+ virtual void OnLookupComplete(const std::string &result) = 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();