File: DnsEvents.cpp

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/*******************************************************************************
 * shroudBNC - an object-oriented framework for IRC                            *
 * Copyright (C) 2005-2007 Gunnar Beutner                                      *
 *                                                                             *
 * This program 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; either version 2              *
 * of the License, or (at your option) any later version.                      *
 *                                                                             *
 * 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. *
 *******************************************************************************/

#include "StdAfx.h"

/**
 * GenericDnsQueryCallback
 *
 * Used as a thunk between c-ares' C-style callbacks and shroudBNC's
 * object-oriented dns class.
 *
 * @param Cookie a pointer to a CDnsQuery object
 * @param Status the status of the dns query
 * @param Timeout reports how many times a query timed out during the
 *        execution of the given request, useable for logging purpose.
 * @param HostEntity the response for the dns query (can be NULL)
 */
void GenericDnsQueryCallback(void *Cookie, int Status, int Timeout, hostent *HostEntity) {
	CDnsQuery *Query = (CDnsQuery *)Cookie;

	Query->AsyncDnsEvent(Status, HostEntity);

	Query->m_PendingQueries--;
}

/**
 * CDnsQuery
 *
 * Constructs a new DNS query object.
 *
 * @param EventInterface an object to which DNS callbacks are routed
 * @param EventFunction a function which is called when DNS queries are completed
 * @param Timeout specifies the timeout value for dns queries
 *
 * \see IMPL_DNSEVENTPROXY
 * \see USE_DNSEVENTPROXY
 */

CDnsQuery::CDnsQuery(void *EventInterface, DnsEventFunction EventFunction, int Timeout) {
	m_Timeout = Timeout;
	m_EventObject = EventInterface;
	m_EventFunction = EventFunction;

	m_Channel = NULL;
	m_PendingQueries = 0;
	FD_ZERO(&m_Reader);
	FD_ZERO(&m_Writer);
}

/**
 * InitChannel
 *
 * Initializes a new ARES channel.
 */
void CDnsQuery::InitChannel(void) {
	if (m_Channel == NULL) {
		ares_options Options;

		Options.timeout = m_Timeout;
		ares_init_options(&m_Channel, &Options, ARES_OPT_TIMEOUT);

		g_Bouncer->RegisterDnsQuery(this);
	}
}

/**
 * DestroyChannel
 *
 * Destroys the ARES channel.
 */
void CDnsQuery::DestroyChannel(void) {
	DnsEventFunction Function;

	if (m_Channel != NULL) {
		FD_ZERO(&m_Reader);
		FD_ZERO(&m_Writer);
		Function = m_EventFunction;
		m_EventFunction = NULL;
		ares_destroy(m_Channel);
		m_EventFunction = Function;

		m_Channel = NULL;

		g_Bouncer->UnregisterDnsQuery(this);

		m_PendingQueries = 0;
	}
}

/**
 * ~CDnsQuery
 *
 * Destructs a DNS query object.
 */
CDnsQuery::~CDnsQuery(void) {
	DestroyChannel();
}

/**
 * GetHostByName
 *
 * Asynchronously performs the task of the "gethostbyname" function
 * and calls the callback function once the operation has completed.
 *
 * @param Host the hostname
 * @param Family the address family (AF_INET or AF_INET6)
 */
void CDnsQuery::GetHostByName(const char *Host, int Family) {
	InitChannel();
	m_PendingQueries++;
	ares_gethostbyname(m_Channel, Host, Family, GenericDnsQueryCallback, this);
}

/**
 * GetHostByAddr
 *
 * Asynchronously performs the task of the "gethostbyaddr" function
 * and calls the callback function once the operation has completed.
 *
 * @param Address the address for which the hostname should be looked up
 */
void CDnsQuery::GetHostByAddr(sockaddr *Address) {
	void *IpAddr;

#ifdef IPV6
	if (Address->sa_family == AF_INET) {
#endif
		IpAddr = &(((sockaddr_in *)Address)->sin_addr);
#ifdef IPV6
	} else {
		IpAddr = &(((sockaddr_in6 *)Address)->sin6_addr);
	}
#endif

	InitChannel();
	m_PendingQueries++;
	ares_gethostbyaddr(m_Channel, IpAddr, INADDR_LEN(Address->sa_family), Address->sa_family, GenericDnsQueryCallback, this);
}

/**
 * GetChannel
 *
 * Returns the underlying c-ares channel object.
 */
ares_channel CDnsQuery::GetChannel(void) {
	return m_Channel;
}

/**
 * AsyncDnsEvent
 *
 * Used by GenericDnsQueryCallback to notify the object of the status
 * of a dns query.
 *
 * @param Status the status
 * @param Response the response for the dns query
 */
void CDnsQuery::AsyncDnsEvent(int Status, hostent *Response) {
	if (m_EventFunction != NULL) {
		(*m_EventFunction)(m_EventObject, Response);
	}
}

/**
 * Cleanup
 *
 * Cleans up unused channels.
 */
void CDnsQuery::Cleanup(void) {
	if (m_PendingQueries == 0) {
		DestroyChannel();
	}
}