/* * InspIRCd -- Internet Relay Chat Daemon * * Copyright (C) 2009 Daniel De Graaf * Copyright (C) 2005-2008 Craig Edwards * Copyright (C) 2007 Dennis Friis * * This file is part of InspIRCd. InspIRCd is free software: you can * redistribute it and/or modify it under the terms of the GNU General Public * License as published by the Free Software Foundation, version 2. * * This program is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more * details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see . */ /* dns.h - dns library very very loosely based on firedns, Copyright (C) 2002 Ian Gulliver This program is free software; you can redistribute it and/or modify it under the terms of version 2 of the GNU General Public License as published by the Free Software Foundation. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ #ifndef DNS_H #define DNS_H #include "socket.h" #include "hashcomp.h" /** * 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 }; /** * 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; /** The type of the request */ QueryType type; /** 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, QueryType qt = DNS_QUERY_NONE) : id(i), result(res), ttl(timetolive), original(orig), type(qt) { } }; /** * Information on a completed lookup, used internally */ typedef std::pair DNSInfo; /** Cached item stored in the query cache. */ class CoreExport CachedQuery { public: /** The cached result data, an IP or hostname */ std::string data; /** The type of result this is */ QueryType type; /** 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, QueryType qt, 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. */ typedef nspace::hash_map dnscache; /** * 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 }; /** * 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(); /** * Returns the creator module, or NULL */ Module* GetCreator(); /** * If the result is a cached result, this triggers the objects * OnLookupComplete. This is done because it is not safe to call * the abstract virtual method from the constructor. */ void TriggerCachedResult(); }; /** DNS is a singleton class used by the core to dispatch dns * requests to the dns server, and route incoming dns replies * back to Resolver objects, based upon the request ID. You * should never use this class yourself. */ class CoreExport DNS : public EventHandler { private: /** * The maximum value of a dns request id, * 16 bits wide, 0xFFFF. */ static const int MAX_REQUEST_ID = 0xFFFF; /** * Currently cached items */ dnscache* cache; /** A timer which ticks every hour to remove expired * items from the DNS cache. */ class CacheTimer* PruneTimer; /** * Build a dns packet payload */ int MakePayload(const char* name, const QueryType rr, const unsigned short rr_class, unsigned char* payload); public: irc::sockets::sockaddrs myserver; /** * Currently active Resolver classes */ Resolver* Classes[MAX_REQUEST_ID]; /** * Requests that are currently 'in flight' */ DNSRequest* requests[MAX_REQUEST_ID]; /** * The port number DNS requests are made on, * and replies have as a source-port number. */ static const int QUERY_PORT = 53; /** * Fill an rr (resource record) with data from input */ static void FillResourceRecord(ResourceRecord* rr, const unsigned char* input); /** * Fill a header with data from input limited by a length */ static void FillHeader(DNSHeader *header, const unsigned char *input, const int length); /** * Empty out a header into a data stream ready for transmission "on the wire" */ static void EmptyHeader(unsigned char *output, const DNSHeader *header, const int length); /** * Start the lookup of an ipv4 from a hostname */ int GetIP(const char* name); /** * Start lookup of a hostname from an ip, but * force a specific protocol to be used for the lookup * for example to perform an ipv6 reverse lookup. */ int GetNameForce(const char *ip, ForceProtocol fp); /** * Start lookup of an ipv6 from a hostname */ int GetIP6(const char *name); /** * Start lookup of a CNAME from another hostname */ int GetCName(const char* alias); /** * Fetch the result string (an ip or host) * and/or an error message to go with it. */ DNSResult GetResult(); /** * Handle a SocketEngine read event * Inherited from EventHandler */ void HandleEvent(EventType et, int errornum = 0); /** * Add a Resolver* to the list of active classes */ bool AddResolverClass(Resolver* r); /** * Add a query to the list to be sent */ DNSRequest* AddQuery(DNSHeader *header, int &id, const char* original); /** * The constructor initialises the dns socket, * and clears the request lists. */ DNS(); /** * Re-initialize the DNS subsystem. */ void Rehash(); /** * Destructor */ ~DNS(); /** * Turn an in6_addr into a .ip6.arpa domain */ static void MakeIP6Int(char* query, const in6_addr *ip); /** * Clean out all dns resolvers owned by a particular * module, to make unloading a module safe if there * are dns requests currently in progress. */ void CleanResolvers(Module* module); /** Return the cached value of an IP or hostname * @param source An IP or hostname to find in the cache. * @return A pointer to a CachedQuery if the item exists, * otherwise NULL. */ CachedQuery* GetCache(const std::string &source); /** Delete a cached item from the DNS cache. * @param source An IP or hostname to remove */ void DelCache(const std::string &source); /** Clear all items from the DNS cache immediately. */ int ClearCache(); /** Prune the DNS cache, e.g. remove all expired * items and rehash the cache buckets, but leave * items in the hash which are still valid. */ int PruneCache(); }; #endif