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/* +------------------------------------+
* | Inspire Internet Relay Chat Daemon |
* +------------------------------------+
*
* InspIRCd: (C) 2002-2007 InspIRCd Development Team
* See: http://www.inspircd.org/wiki/index.php/Credits
*
* 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 "base.h"
#include "socketengine.h"
#include "socket.h"
#include "hash_map.h"
#include "hashcomp.h"
using namespace std;
using irc::sockets::insp_aton;
using irc::sockets::insp_ntoa;
using irc::sockets::insp_sockaddr;
using irc::sockets::insp_inaddr;
class InspIRCd;
class Module;
/**
* Result status, used internally
*/
class CoreExport DNSResult : public classbase
{
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) : data(res)
{
expires = time(NULL) + ttl;
}
/** Returns the number of seconds remaining before this
* cache item has expired and should be removed.
*/
int CalcTTLRemaining()
{
int n = (int)expires - (int)time(NULL);
return (n < 0 ? 0 : n);
}
};
/** DNS cache information. Holds IPs mapped to hostnames, and hostnames mapped to IPs.
*/
#ifndef WIN32
typedef nspace::hash_map<irc::string, CachedQuery, nspace::hash<irc::string> > dnscache;
#else
typedef nspace::hash_map<irc::string, CachedQuery, nspace::hash_compare<irc::string> > 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_NOTREADY = 3,
RESOLVER_BADIP = 4,
RESOLVER_TIMEOUT = 5,
RESLOVER_FORCEUNLOAD = 6
};
/**
* A DNS request
*/
class DNSRequest;
/**
* A DNS packet header
*/
class DNSHeader;
/**
* A DNS Resource Record (rr)
*/
struct ResourceRecord;
/**
* Query and resource record types
*/
enum QueryType
{
DNS_QUERY_NONE = 0, /* Uninitialized Query */
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;
#else
const QueryType DNS_QUERY_FORWARD = DNS_QUERY_A;
#endif
const QueryType DNS_QUERY_REVERSE = DNS_QUERY_PTR;
/**
* 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 CoreExport Resolver : public Extensible
{
protected:
/**
* Pointer to creator
*/
InspIRCd* ServerInstance;
/**
* Pointer to creator module (if any, or NULL)
*/
Module* 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. 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.
* @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(InspIRCd* Instance, const std::string &source, QueryType qt, bool &cached, Module* creator = NULL);
/**
* 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:
/**
* Creator/Owner object
*/
InspIRCd* ServerInstance;
/**
* The maximum value of a dns request id,
* 16 bits wide, 0xFFFF.
*/
static const int MAX_REQUEST_ID = 0xFFFF;
/**
* A counter used to form part of the pseudo-random id
*/
int currid;
/**
* We have to turn off a few checks on received packets
* when people are using 4in6 (e.g. ::ffff:xxxx). This is
* a temporary kludge, Please let me know if you know how
* to fix it.
*/
bool ip6munge;
/**
* 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:
/**
* Server address being used currently
*/
int socketfamily;
#ifdef IPV6
in6_addr myserver6;
#endif
in_addr myserver4;
/**
* 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 the lookup of a hostname from an ip,
* always using the protocol inspircd is built for,
* e.g. use ipv6 reverse lookup when built for ipv6,
* or ipv4 lookup when built for ipv4.
*/
int GetName(const insp_inaddr* ip);
/**
* 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(InspIRCd* Instance);
/**
* Re-initialize the DNS subsystem.
*/
void Rehash();
/**
* 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();
/**
* 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
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