inspircd/include/dns.h

/*       +------------------------------------+
 *       | Inspire Internet Relay Chat Daemon |
 *       +------------------------------------+
 *
 *  InspIRCd is copyright (C) 2002-2006 ChatSpike-Dev.
 *                     E-mail:
 *              <brain@chatspike.net>
 *              <Craig@chatspike.net>
 *
 * Written by Craig Edwards, Craig McLure, and others.
 * This program is free but copyrighted software; see
 *          the file COPYING for details.
 *
 * ---------------------------------------------------
 */

/*
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 <string>
#include "inspircd_config.h"
#include "socket.h"
#include "base.h"

/**
 * Result status, used internally
 */
typedef std::pair<int,std::string> DNSResult;

/**
 * Information on a completed lookup, used internally
 */
typedef std::pair<unsigned char*, std::string> DNSInfo;

/**
 * Error types that class Resolver can emit to its error method.
 */
enum ResolverError
{
	RESOLVER_NOERROR	=	0,
	RESOLVER_NSDOWN		= 	1,
	RESOLVER_NXDOMAIN	=	2,
	RESOLVER_NOTREADY	=	3,
	RESOLVER_BADIP		=	4
};

/**
 * A DNS request
 */
class DNSRequest;

/**
 * A DNS packet header
 */
class DNSHeader;

/**
 * A DNS Resource Record (rr)
 */
class ResourceRecord;

/**
 * A set of requests keyed by request id
 */
typedef std::map<int,DNSRequest*> requestlist;

/**
 * An iterator into a set of requests
 */
typedef requestlist::iterator requestlist_iter;

/**
 * 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:
	/**
	 * The input data, either a host or an IP address
	 */
	std::string input;
	/**
	 * True if a forward lookup is being performed, false if otherwise
	 */
	bool fwd;
	/**
	 * 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 forward Set to true to perform a forward lookup (hostname to ip) or false
	 * to perform a reverse lookup (ip to hostname). Lookups on A records and PTR
	 * records are supported. CNAME and MX are not supported by this resolver.
	 * If InspIRCd is compiled with ipv6 support, lookups on AAAA records are preferred
	 * and supported over A records.
	 * @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.
	 */
	Resolver(const std::string &source, bool forward);
	/**
	 * 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();
};

/**
 * Query and resource record types
 */
enum QueryType
{
	DNS_QUERY_A	= 1,	/* 'A' record: an IP address */
	DNS_QUERY_PTR	= 12	/* 'PTR' record: a hostname */
};

/** 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 DNS : public Extensible
{
 private:

	/**
	 * The maximum value of a dns request id,
	 * 16 bits wide, 0xFFFF.
	 */
	static const int MAX_REQUEST_ID = 0xFFFF;

	/**
	 * Requests that are currently 'in flight'
	 */
	requestlist requests;

	/**
	 * Server address being used currently
	 */
	insp_inaddr myserver;

	/**
	 * File descriptor being used to perform queries
	 */
	static int MasterSocket;

	/**
	 * A counter used to form part of the pseudo-random id
	 */
	int currid;

	/**
	 * Currently active Resolver classes
	 */
	Resolver* Classes[MAX_REQUEST_ID];

	/**
	 * Build a dns packet payload
	 */
	int MakePayload(const char* name, const QueryType rr, const unsigned short rr_class, unsigned char* payload);

 public:
	/**
	 * 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);
	/**
	 * Get the master socket fd, used internally
	 */
	static int GetMasterSocket();

	/**
	 * Start the lookup of an ip from a hostname
	 */
	int GetIP(const char* name);

	/**
	 * Start the lookup of a hostname from an ip
	 */
	int GetName(const insp_inaddr* ip);

	/**
	 * Fetch the result string (an ip or host)
	 * and/or an error message to go with it.
	 */
	DNSResult GetResult();

	/**
	 * Handle a SocketEngine read event
	 */
	void MarshallReads(int fd);

	/**
	 * 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);

	/**
	 * The constructor initialises the dns socket,
	 * and clears the request lists.
	 */
	DNS();

	/**
	 * Destructor
	 */
	~DNS();

	/** Portable random number generator, generates
	 * its random number from the ircd stats counters,
	 * effective user id, time of day and the rollover
	 * counter (currid)
	 */
	unsigned long PRNG();
};

#endif