/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, you can obtain one at https://mozilla.org/MPL/2.0/.
 *
 * See the COPYRIGHT file distributed with this work for additional
 * information regarding copyright ownership.
 */

#ifndef DNS_DISPATCH_H
#define DNS_DISPATCH_H 1

/*****
***** Module Info
*****/

/*! \file dns/dispatch.h
 * \brief
 * DNS Dispatch Management
 * 	Shared UDP and single-use TCP dispatches for queries and responses.
 *
 * MP:
 *
 *\li     	All locking is performed internally to each dispatch.
 * 	Restrictions apply to dns_dispatch_removeresponse().
 *
 * Reliability:
 *
 * Resources:
 *
 * Security:
 *
 *\li	Depends on the isc_socket_t and dns_message_t for prevention of
 *	buffer overruns.
 *
 * Standards:
 *
 *\li	None.
 */

/***
 *** Imports
 ***/

#include <inttypes.h>
#include <stdbool.h>

#include <isc/buffer.h>
#include <isc/lang.h>
#include <isc/mutex.h>
#include <isc/socket.h>
#include <isc/types.h>

#include <dns/types.h>

ISC_LANG_BEGINDECLS

/*%
 * This event is sent to a task when a response comes in.
 * No part of this structure should ever be modified by the caller,
 * other than parts of the buffer.  The holy parts of the buffer are
 * the base and size of the buffer.  All other parts of the buffer may
 * be used.  On event delivery the used region contains the packet.
 *
 * "id" is the received message id,
 *
 * "addr" is the host that sent it to us,
 *
 * "buffer" holds state on the received data.
 *
 * The "free" routine for this event will clean up itself as well as
 * any buffer space allocated from common pools.
 */

struct dns_dispatchevent {
	ISC_EVENT_COMMON(dns_dispatchevent_t); /*%< standard event common */
	isc_result_t	   result;	       /*%< result code */
	int32_t		   id;		       /*%< message id */
	isc_sockaddr_t	   addr;	       /*%< address recv'd from */
	struct in6_pktinfo pktinfo;	       /*%< reply info for v6 */
	isc_buffer_t	   buffer;	       /*%< data buffer */
	uint32_t	   attributes;	       /*%< mirrored from socket.h */
};

/*%
 * This is a set of one or more dispatches which can be retrieved
 * round-robin fashion.
 */
struct dns_dispatchset {
	isc_mem_t	  *mctx;
	dns_dispatch_t **dispatches;
	int		 ndisp;
	int		 cur;
	isc_mutex_t	 lock;
};

/*@{*/
/*%
 * Attributes for added dispatchers.
 *
 * Values with the mask 0xffff0000 are application defined.
 * Values with the mask 0x0000ffff are library defined.
 *
 * Insane values (like setting both TCP and UDP) are not caught.  Don't
 * do that.
 *
 * _PRIVATE
 *	The dispatcher cannot be shared.
 *
 * _TCP, _UDP
 *	The dispatcher is a TCP or UDP socket.
 *
 * _IPV4, _IPV6
 *	The dispatcher uses an IPv4 or IPv6 socket.
 *
 * _NOLISTEN
 *	The dispatcher should not listen on the socket.
 *
 * _MAKEQUERY
 *	The dispatcher can be used to issue queries to other servers, and
 *	accept replies from them.
 *
 * _RANDOMPORT
 *	Previously used to indicate that the port of a dispatch UDP must be
 *	chosen randomly.  This behavior now always applies and the attribute
 *	is obsoleted.
 *
 * _EXCLUSIVE
 *	A separate socket will be used on-demand for each transaction.
 */
#define DNS_DISPATCHATTR_PRIVATE   0x00000001U
#define DNS_DISPATCHATTR_TCP	   0x00000002U
#define DNS_DISPATCHATTR_UDP	   0x00000004U
#define DNS_DISPATCHATTR_IPV4	   0x00000008U
#define DNS_DISPATCHATTR_IPV6	   0x00000010U
#define DNS_DISPATCHATTR_NOLISTEN  0x00000020U
#define DNS_DISPATCHATTR_MAKEQUERY 0x00000040U
#define DNS_DISPATCHATTR_CONNECTED 0x00000080U
#define DNS_DISPATCHATTR_FIXEDID   0x00000100U
#define DNS_DISPATCHATTR_EXCLUSIVE 0x00000200U
#define DNS_DISPATCHATTR_CANREUSE  0x00000400U
/*@}*/

/*
 */
#define DNS_DISPATCHOPT_FIXEDID 0x00000001U

isc_result_t
dns_dispatchmgr_create(isc_mem_t *mctx, dns_dispatchmgr_t **mgrp);
/*%<
 * Creates a new dispatchmgr object.
 *
 * Requires:
 *\li	"mctx" be a valid memory context.
 *
 *\li	mgrp != NULL && *mgrp == NULL
 *
 * Returns:
 *\li	ISC_R_SUCCESS	-- all ok
 *
 *\li	anything else	-- failure
 */

void
dns_dispatchmgr_destroy(dns_dispatchmgr_t **mgrp);
/*%<
 * Destroys the dispatchmgr when it becomes empty.  This could be
 * immediately.
 *
 * Requires:
 *\li	mgrp != NULL && *mgrp is a valid dispatchmgr.
 */

void
dns_dispatchmgr_setblackhole(dns_dispatchmgr_t *mgr, dns_acl_t *blackhole);
/*%<
 * Sets the dispatcher's "blackhole list," a list of addresses that will
 * be ignored by all dispatchers created by the dispatchmgr.
 *
 * Requires:
 * \li	mgrp is a valid dispatchmgr
 * \li	blackhole is a valid acl
 */

dns_acl_t *
dns_dispatchmgr_getblackhole(dns_dispatchmgr_t *mgr);
/*%<
 * Gets a pointer to the dispatcher's current blackhole list,
 * without incrementing its reference count.
 *
 * Requires:
 *\li 	mgr is a valid dispatchmgr
 * Returns:
 *\li	A pointer to the current blackhole list, or NULL.
 */

void
dns_dispatchmgr_setblackportlist(dns_dispatchmgr_t *mgr,
				 dns_portlist_t	*portlist);
/*%<
 * This function is deprecated.  Use dns_dispatchmgr_setavailports() instead.
 *
 * Requires:
 *\li	mgr is a valid dispatchmgr
 */

dns_portlist_t *
dns_dispatchmgr_getblackportlist(dns_dispatchmgr_t *mgr);
/*%<
 * This function is deprecated and always returns NULL.
 *
 * Requires:
 *\li	mgr is a valid dispatchmgr
 */

isc_result_t
dns_dispatchmgr_setavailports(dns_dispatchmgr_t *mgr, isc_portset_t *v4portset,
			      isc_portset_t *v6portset);
/*%<
 * Sets a list of UDP ports that can be used for outgoing UDP messages.
 *
 * Requires:
 *\li	mgr is a valid dispatchmgr
 *\li	v4portset is NULL or a valid port set
 *\li	v6portset is NULL or a valid port set
 */

void
dns_dispatchmgr_setstats(dns_dispatchmgr_t *mgr, isc_stats_t *stats);
/*%<
 * Sets statistics counter for the dispatchmgr.  This function is expected to
 * be called only on zone creation (when necessary).
 * Once installed, it cannot be removed or replaced.  Also, there is no
 * interface to get the installed stats from the zone; the caller must keep the
 * stats to reference (e.g. dump) it later.
 *
 * Requires:
 *\li	mgr is a valid dispatchmgr with no managed dispatch.
 *\li	stats is a valid statistics supporting resolver statistics counters
 *	(see dns/stats.h).
 */

isc_result_t
dns_dispatch_getudp(dns_dispatchmgr_t *mgr, isc_socketmgr_t *sockmgr,
		    isc_taskmgr_t *taskmgr, const isc_sockaddr_t *localaddr,
		    unsigned int buffersize, unsigned int maxbuffers,
		    unsigned int maxrequests, unsigned int buckets,
		    unsigned int increment, unsigned int attributes,
		    unsigned int mask, dns_dispatch_t **dispp);

isc_result_t
dns_dispatch_getudp_dup(dns_dispatchmgr_t *mgr, isc_socketmgr_t *sockmgr,
			isc_taskmgr_t *taskmgr, const isc_sockaddr_t *localaddr,
			unsigned int buffersize, unsigned int maxbuffers,
			unsigned int maxrequests, unsigned int buckets,
			unsigned int increment, unsigned int attributes,
			unsigned int mask, dns_dispatch_t **dispp,
			dns_dispatch_t *dup);
/*%<
 * Attach to existing dns_dispatch_t if one is found with dns_dispatchmgr_find,
 * otherwise create a new UDP dispatch.
 *
 * Requires:
 *\li	All pointer parameters be valid for their respective types.
 *
 *\li	dispp != NULL && *disp == NULL
 *
 *\li	512 <= buffersize <= 64k
 *
 *\li	maxbuffers > 0
 *
 *\li	buckets < 2097169
 *
 *\li	increment > buckets
 *
 *\li	(attributes & DNS_DISPATCHATTR_TCP) == 0
 *
 * Returns:
 *\li	ISC_R_SUCCESS	-- success.
 *
 *\li	Anything else	-- failure.
 */

isc_result_t
dns_dispatch_createtcp(dns_dispatchmgr_t *mgr, isc_socket_t *sock,
		       isc_taskmgr_t *taskmgr, const isc_sockaddr_t *localaddr,
		       const isc_sockaddr_t *destaddr, unsigned int buffersize,
		       unsigned int maxbuffers, unsigned int maxrequests,
		       unsigned int buckets, unsigned int increment,
		       unsigned int attributes, dns_dispatch_t **dispp);
/*%<
 * Create a new dns_dispatch and attach it to the provided isc_socket_t.
 *
 * For all dispatches, "buffersize" is the maximum packet size we will
 * accept.
 *
 * "maxbuffers" and "maxrequests" control the number of buffers in the
 * overall system and the number of buffers which can be allocated to
 * requests.
 *
 * "buckets" is the number of buckets to use, and should be prime.
 *
 * "increment" is used in a collision avoidance function, and needs to be
 * a prime > buckets, and not 2.
 *
 * Requires:
 *
 *\li	mgr is a valid dispatch manager.
 *
 *\li	sock is a valid.
 *
 *\li	task is a valid task that can be used internally to this dispatcher.
 *
 * \li	512 <= buffersize <= 64k
 *
 *\li	maxbuffers > 0.
 *
 *\li	maxrequests <= maxbuffers.
 *
 *\li	buckets < 2097169 (the next prime after 65536 * 32)
 *
 *\li	increment > buckets (and prime).
 *
 *\li	attributes includes #DNS_DISPATCHATTR_TCP and does not include
 *	#DNS_DISPATCHATTR_UDP.
 *
 * Returns:
 *\li	ISC_R_SUCCESS	-- success.
 *
 *\li	Anything else	-- failure.
 */

void
dns_dispatch_attach(dns_dispatch_t *disp, dns_dispatch_t **dispp);
/*%<
 * Attach to a dispatch handle.
 *
 * Requires:
 *\li	disp is valid.
 *
 *\li	dispp != NULL && *dispp == NULL
 */

void
dns_dispatch_detach(dns_dispatch_t **dispp);
/*%<
 * Detaches from the dispatch.
 *
 * Requires:
 *\li	dispp != NULL and *dispp be a valid dispatch.
 */

void
dns_dispatch_starttcp(dns_dispatch_t *disp);
/*%<
 * Start processing of a TCP dispatch once the socket connects.
 *
 * Requires:
 *\li	'disp' is valid.
 */

isc_result_t
dns_dispatch_gettcp(dns_dispatchmgr_t *mgr, const isc_sockaddr_t *destaddr,
		    const isc_sockaddr_t *localaddr, bool *connected,
		    dns_dispatch_t **dispp);
/*
 * Attempt to connect to a existing TCP connection (connection completed
 * if connected == NULL).
 */

isc_result_t
dns_dispatch_addresponse(dns_dispatch_t *disp, unsigned int options,
			 const isc_sockaddr_t *dest, isc_task_t *task,
			 isc_taskaction_t action, void *arg, uint16_t *idp,
			 dns_dispentry_t **resp, isc_socketmgr_t *sockmgr);
/*%<
 * Add a response entry for this dispatch.
 *
 * "*idp" is filled in with the assigned message ID, and *resp is filled in
 * to contain the magic token used to request event flow stop.
 *
 * Arranges for the given task to get a callback for response packets.  When
 * the event is delivered, it must be returned using dns_dispatch_freeevent()
 * or through dns_dispatch_removeresponse() for another to be delivered.
 *
 * Requires:
 *\li	"idp" be non-NULL.
 *
 *\li	"task" "action" and "arg" be set as appropriate.
 *
 *\li	"dest" be non-NULL and valid.
 *
 *\li	"resp" be non-NULL and *resp be NULL
 *
 *\li	"sockmgr" be NULL or a valid socket manager.  If 'disp' has
 *	the DNS_DISPATCHATTR_EXCLUSIVE attribute, this must not be NULL,
 *	which also means dns_dispatch_addresponse() cannot be used.
 *
 * Ensures:
 *
 *\li	&lt;id, dest> is a unique tuple.  That means incoming messages
 *	are identifiable.
 *
 * Returns:
 *
 *\li	ISC_R_SUCCESS		-- all is well.
 *\li	ISC_R_NOMEMORY		-- memory could not be allocated.
 *\li	ISC_R_NOMORE		-- no more message ids can be allocated
 *				   for this destination.
 */

void
dns_dispatch_removeresponse(dns_dispentry_t	    **resp,
			    dns_dispatchevent_t **sockevent);
/*%<
 * Stops the flow of responses for the provided id and destination.
 * If "sockevent" is non-NULL, the dispatch event and associated buffer is
 * also returned to the system.
 *
 * Requires:
 *\li	"resp" != NULL and "*resp" contain a value previously allocated
 *	by dns_dispatch_addresponse();
 *
 *\li	May only be called from within the task given as the 'task'
 * 	argument to dns_dispatch_addresponse() when allocating '*resp'.
 */

isc_socket_t *
dns_dispatch_getentrysocket(dns_dispentry_t *resp);

isc_socket_t *
dns_dispatch_getsocket(dns_dispatch_t *disp);
/*%<
 * Return the socket associated with this dispatcher.
 *
 * Requires:
 *\li	disp is valid.
 *
 * Returns:
 *\li	The socket the dispatcher is using.
 */

isc_result_t
dns_dispatch_getlocaladdress(dns_dispatch_t *disp, isc_sockaddr_t *addrp);
/*%<
 * Return the local address for this dispatch.
 * This currently only works for dispatches using UDP sockets.
 *
 * Requires:
 *\li	disp is valid.
 *\li	addrp to be non null.
 *
 * Returns:
 *\li	ISC_R_SUCCESS
 *\li	ISC_R_NOTIMPLEMENTED
 */

void
dns_dispatch_cancel(dns_dispatch_t *disp);
/*%<
 * cancel outstanding clients
 *
 * Requires:
 *\li	disp is valid.
 */

unsigned int
dns_dispatch_getattributes(dns_dispatch_t *disp);
/*%<
 * Return the attributes (DNS_DISPATCHATTR_xxx) of this dispatch.  Only the
 * non-changeable attributes are expected to be referenced by the caller.
 *
 * Requires:
 *\li	disp is valid.
 */

void
dns_dispatch_changeattributes(dns_dispatch_t *disp, unsigned int attributes,
			      unsigned int mask);
/*%<
 * Set the bits described by "mask" to the corresponding values in
 * "attributes".
 *
 * That is:
 *
 * \code
 *	new = (old & ~mask) | (attributes & mask)
 * \endcode
 *
 * This function has a side effect when #DNS_DISPATCHATTR_NOLISTEN changes.
 * When the flag becomes off, the dispatch will start receiving on the
 * corresponding socket.  When the flag becomes on, receive events on the
 * corresponding socket will be canceled.
 *
 * Requires:
 *\li	disp is valid.
 *
 *\li	attributes are reasonable for the dispatch.  That is, setting the UDP
 *	attribute on a TCP socket isn't reasonable.
 */

void
dns_dispatch_importrecv(dns_dispatch_t *disp, isc_event_t *event);
/*%<
 * Inform the dispatcher of a socket receive.  This is used for sockets
 * shared between dispatchers and clients.  If the dispatcher fails to copy
 * or send the event, nothing happens.
 *
 * If the attribute DNS_DISPATCHATTR_NOLISTEN is not set, then
 * the dispatch is already handling a recv; return immediately.
 *
 * Requires:
 *\li 	disp is valid, and the attribute DNS_DISPATCHATTR_NOLISTEN is set.
 * 	event != NULL
 */

dns_dispatch_t *
dns_dispatchset_get(dns_dispatchset_t *dset);
/*%<
 * Retrieve the next dispatch from dispatch set 'dset', and increment
 * the round-robin counter.
 *
 * Requires:
 *\li 	dset != NULL
 */

isc_result_t
dns_dispatchset_create(isc_mem_t *mctx, isc_socketmgr_t *sockmgr,
		       isc_taskmgr_t *taskmgr, dns_dispatch_t *source,
		       dns_dispatchset_t **dsetp, int n);
/*%<
 * Given a valid dispatch 'source', create a dispatch set containing
 * 'n' UDP dispatches, with the remainder filled out by clones of the
 * source.
 *
 * Requires:
 *\li 	source is a valid UDP dispatcher
 *\li 	dsetp != NULL, *dsetp == NULL
 */

void
dns_dispatchset_cancelall(dns_dispatchset_t *dset, isc_task_t *task);
/*%<
 * Cancel socket operations for the dispatches in 'dset'.
 */

void
dns_dispatchset_destroy(dns_dispatchset_t **dsetp);
/*%<
 * Dereference all the dispatches in '*dsetp', free the dispatchset
 * memory, and set *dsetp to NULL.
 *
 * Requires:
 *\li 	dset is valid
 */

void
dns_dispatch_setdscp(dns_dispatch_t *disp, isc_dscp_t dscp);
isc_dscp_t
dns_dispatch_getdscp(dns_dispatch_t *disp);
/*%<
 * Set/get the DSCP value to be used when sending responses to clients,
 * as defined in the "listen-on" or "listen-on-v6" statements.
 *
 * Requires:
 *\li	disp is valid.
 */

isc_result_t
dns_dispatch_getnext(dns_dispentry_t *resp, dns_dispatchevent_t **sockevent);
/*%<
 * Free the sockevent and trigger the sending of the next item off the
 * dispatch queue if present.
 *
 * Requires:
 *\li	resp is valid
 *\li	*sockevent to be valid
 */

ISC_LANG_ENDDECLS

#endif /* DNS_DISPATCH_H */
