/*
 * util/netevent.h - event notification
 *
 * Copyright (c) 2007, NLnet Labs. All rights reserved.
 *
 * This software is open source.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 * 
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * 
 * Neither the name of the NLNET LABS nor the names of its contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * \file
 *
 * This file contains event notification functions.
 *
 * There are three types of communication points
 *    o UDP socket - perthread buffer.
 *    o TCP-accept socket - array of TCP-sockets, socketcount.
 *    o TCP socket - own buffer, parent-TCPaccept, read/write state,
 *                   number of bytes read/written, timeout.
 *
 * There are sockets aimed towards our clients and towards the internet.
 *    o frontside - aimed towards our clients, queries come in, answers back.
 *    o behind - aimed towards internet, to the authoritative DNS servers.
 *
 * Several event types are available:
 *    o comm_base - for thread safety of the comm points, one per thread.
 *    o comm_point - udp and tcp networking, with callbacks.
 *    o comm_timer - a timeout with callback.
 *    o comm_signal - callbacks when signal is caught.
 *    o comm_reply - holds reply info during networking callback.
 *
 */

#ifndef NET_EVENT_H
#define NET_EVENT_H

struct sldns_buffer;
struct comm_point;
struct comm_reply;
struct event_base;

/* internal event notification data storage structure. */
struct internal_event;
struct internal_base;
struct internal_timer;

/** callback from communication point function type */
typedef int comm_point_callback_t(struct comm_point*, void*, int, 
	struct comm_reply*);

/** to pass no_error to callback function */
#define NETEVENT_NOERROR 0
/** to pass closed connection to callback function */
#define NETEVENT_CLOSED -1
/** to pass timeout happened to callback function */
#define NETEVENT_TIMEOUT -2 
/** to pass fallback from capsforID to callback function; 0x20 failed */
#define NETEVENT_CAPSFAIL -3

/** timeout to slow accept calls when not possible, in msec. */
#define NETEVENT_SLOW_ACCEPT_TIME 2000

/**
 * A communication point dispatcher. Thread specific.
 */
struct comm_base {
	/** behind the scenes structure. with say libevent info. alloced */
	struct internal_base* eb;
	/** callback to stop listening on accept sockets,
	 * performed when accept() will not function properly */
	void (*stop_accept)(void*);
	/** callback to start listening on accept sockets, performed
	 * after stop_accept() then a timeout has passed. */
	void (*start_accept)(void*);
	/** user argument for stop_accept and start_accept functions */
	void* cb_arg;
};

/**
 * Reply information for a communication point.
 */
struct comm_reply {
	/** the comm_point with fd to send reply on to. */
	struct comm_point* c;
	/** the address (for UDP based communication) */
	struct sockaddr_storage addr;
	/** length of address */
	socklen_t addrlen;
	/** return type 0 (none), 4(IP4), 6(IP6) */
	int srctype;
	/** the return source interface data */
	union {
#ifdef IPV6_PKTINFO
		struct in6_pktinfo v6info;
#endif
#ifdef IP_PKTINFO
		struct in_pktinfo v4info;
#elif defined(IP_RECVDSTADDR)
		struct in_addr v4addr;
#endif
	} 	
		/** variable with return source data */
		pktinfo;
};

/** 
 * Communication point to the network 
 * These behaviours can be accomplished by setting the flags
 * and passing return values from the callback.
 *    udp frontside: called after readdone. sendafter.
 *    tcp frontside: called readdone, sendafter. close.
 *    udp behind: called after readdone. No send after.
 *    tcp behind: write done, read done, then called. No send after.
 */
struct comm_point {
	/** behind the scenes structure, with say libevent info. alloced. */
	struct internal_event* ev;

	/** file descriptor for communication point */
	int fd;

	/** timeout (NULL if it does not). Malloced. */
	struct timeval* timeout;

	/** buffer pointer. Either to perthread, or own buffer or NULL */
	struct sldns_buffer* buffer;

	/* -------- TCP Handler -------- */
	/** Read/Write state for TCP */
	int tcp_is_reading;
	/** The current read/write count for TCP */
	size_t tcp_byte_count;
	/** parent communication point (for TCP sockets) */
	struct comm_point* tcp_parent;
	/** sockaddr from peer, for TCP handlers */
	struct comm_reply repinfo;

	/* -------- TCP Accept -------- */
	/** the number of TCP handlers for this tcp-accept socket */
	int max_tcp_count;
	/** current number of tcp handler in-use for this accept socket */
	int cur_tcp_count;
	/** malloced array of tcp handlers for a tcp-accept, 
	    of size max_tcp_count. */
	struct comm_point** tcp_handlers;
	/** linked list of free tcp_handlers to use for new queries.
	    For tcp_accept the first entry, for tcp_handlers the next one. */
	struct comm_point* tcp_free;

	/* -------- SSL TCP DNS ------- */
	/** the SSL object with rw bio (owned) or for commaccept ctx ref */
	void* ssl;
	/** handshake state for init and renegotiate */
	enum {
		/** no handshake, it has been done */
		comm_ssl_shake_none = 0,
		/** ssl initial handshake wants to read */
		comm_ssl_shake_read,
		/** ssl initial handshake wants to write */
		comm_ssl_shake_write,
		/** ssl_write wants to read */
		comm_ssl_shake_hs_read,
		/** ssl_read wants to write */
		comm_ssl_shake_hs_write
	} ssl_shake_state;

	/* -------- dnstap ------- */
	/** the dnstap environment */
	struct dt_env* dtenv;

	/** is this a UDP, TCP-accept or TCP socket. */
	enum comm_point_type {
		/** UDP socket - handle datagrams. */
		comm_udp, 
		/** TCP accept socket - only creates handlers if readable. */
		comm_tcp_accept, 
		/** TCP handler socket - handle byteperbyte readwrite. */
		comm_tcp,
		/** AF_UNIX socket - for internal commands. */
		comm_local,
		/** raw - not DNS format - for pipe readers and writers */
		comm_raw
	} 
		/** variable with type of socket, UDP,TCP-accept,TCP,pipe */
		type;

	/* ---------- Behaviour ----------- */
	/** if set the connection is NOT closed on delete. */
	int do_not_close;

	/** if set, the connection is closed on error, on timeout, 
	    and after read/write completes. No callback is done. */
	int tcp_do_close;

	/** if set, read/write completes:
		read/write state of tcp is toggled.
		buffer reset/bytecount reset.
		this flag cleared.
	    So that when that is done the callback is called. */
	int tcp_do_toggle_rw;

	/** if set, checks for pending error from nonblocking connect() call.*/
	int tcp_check_nb_connect;

	/** number of queries outstanding on this socket, used by
	 * outside network for udp ports */
	int inuse;

	/** callback when done.
	    tcp_accept does not get called back, is NULL then.
	    If a timeout happens, callback with timeout=1 is called.
	    If an error happens, callback is called with error set 
	    nonzero. If not NETEVENT_NOERROR, it is an errno value.
	    If the connection is closed (by remote end) then the
	    callback is called with error set to NETEVENT_CLOSED=-1.
	    If a timeout happens on the connection, the error is set to 
	    NETEVENT_TIMEOUT=-2.
	    The reply_info can be copied if the reply needs to happen at a
	    later time. It consists of a struct with commpoint and address.
	    It can be passed to a msg send routine some time later.
	    Note the reply information is temporary and must be copied.
	    NULL is passed for_reply info, in cases where error happened.

	    declare as: 
	    int my_callback(struct comm_point* c, void* my_arg, int error,
		struct comm_reply *reply_info);

	    if the routine returns 0, nothing is done.
	    Notzero, the buffer will be sent back to client.
	    		For UDP this is done without changing the commpoint.
			In TCP it sets write state.
	*/
	comm_point_callback_t* callback;
	/** argument to pass to callback. */
	void *cb_arg;
};

/**
 * Structure only for making timeout events.
 */
struct comm_timer {
	/** the internal event stuff */
	struct internal_timer* ev_timer;

	/** callback function, takes user arg only */
	void (*callback)(void*);

	/** callback user argument */
	void* cb_arg;
};

/**
 * Structure only for signal events.
 */
struct comm_signal {
	/** the communication base */
	struct comm_base* base;

	/** the internal event stuff */
	struct internal_signal* ev_signal;

	/** callback function, takes signal number and user arg */
	void (*callback)(int, void*);

	/** callback user argument */
	void* cb_arg;
};

/**
 * Create a new comm base.
 * @param sigs: if true it attempts to create a default loop for 
 *   signal handling.
 * @return: the new comm base. NULL on error.
 */
struct comm_base* comm_base_create(int sigs);

/**
 * Create comm base that uses the given event_base (underlying event
 * mechanism pointer).
 * @param base: underlying lib event base.
 * @return: the new comm base. NULL on error.
 */
struct comm_base* comm_base_create_event(struct event_base* base);

/**
 * Delete comm base structure but not the underlying lib event base.
 * All comm points must have been deleted.
 * @param b: the base to delete.
 */
void comm_base_delete_no_base(struct comm_base* b);

/**
 * Destroy a comm base.
 * All comm points must have been deleted.
 * @param b: the base to delete.
 */
void comm_base_delete(struct comm_base* b);

/**
 * Obtain two pointers. The pointers never change (until base_delete()).
 * The pointers point to time values that are updated regularly.
 * @param b: the communication base that will update the time values.
 * @param tt: pointer to time in seconds is returned.
 * @param tv: pointer to time in microseconds is returned.
 */
void comm_base_timept(struct comm_base* b, time_t** tt, struct timeval** tv);

/**
 * Dispatch the comm base events.
 * @param b: the communication to perform.
 */
void comm_base_dispatch(struct comm_base* b);

/**
 * Exit from dispatch loop.
 * @param b: the communication base that is in dispatch().
 */
void comm_base_exit(struct comm_base* b);

/**
 * Set the slow_accept mode handlers.  You can not provide these if you do
 * not perform accept() calls.
 * @param b: comm base
 * @param stop_accept: function that stops listening to accept fds.
 * @param start_accept: function that resumes listening to accept fds.
 * @param arg: callback arg to pass to the functions.
 */
void comm_base_set_slow_accept_handlers(struct comm_base* b,
	void (*stop_accept)(void*), void (*start_accept)(void*), void* arg);

/**
 * Access internal data structure (for util/tube.c on windows)
 * @param b: comm base
 * @return event_base. Could be libevent, or internal event handler.
 */
struct event_base* comm_base_internal(struct comm_base* b);

/**
 * Create an UDP comm point. Calls malloc.
 * setups the structure with the parameters you provide.
 * @param base: in which base to alloc the commpoint.
 * @param fd : file descriptor of open UDP socket.
 * @param buffer: shared buffer by UDP sockets from this thread.
 * @param callback: callback function pointer.
 * @param callback_arg: will be passed to your callback function.
 * @return: returns the allocated communication point. NULL on error.
 * Sets timeout to NULL. Turns off TCP options.
 */
struct comm_point* comm_point_create_udp(struct comm_base* base,
	int fd, struct sldns_buffer* buffer, 
	comm_point_callback_t* callback, void* callback_arg);

/**
 * Create an UDP with ancillary data comm point. Calls malloc.
 * Uses recvmsg instead of recv to get udp message.
 * setups the structure with the parameters you provide.
 * @param base: in which base to alloc the commpoint.
 * @param fd : file descriptor of open UDP socket.
 * @param buffer: shared buffer by UDP sockets from this thread.
 * @param callback: callback function pointer.
 * @param callback_arg: will be passed to your callback function.
 * @return: returns the allocated communication point. NULL on error.
 * Sets timeout to NULL. Turns off TCP options.
 */
struct comm_point* comm_point_create_udp_ancil(struct comm_base* base,
	int fd, struct sldns_buffer* buffer, 
	comm_point_callback_t* callback, void* callback_arg);

/**
 * Create a TCP listener comm point. Calls malloc.
 * Setups the structure with the parameters you provide.
 * Also Creates TCP Handlers, pre allocated for you.
 * Uses the parameters you provide.
 * @param base: in which base to alloc the commpoint.
 * @param fd: file descriptor of open TCP socket set to listen nonblocking.
 * @param num: becomes max_tcp_count, the routine allocates that
 *	many tcp handler commpoints.
 * @param bufsize: size of buffer to create for handlers.
 * @param callback: callback function pointer for TCP handlers.
 * @param callback_arg: will be passed to your callback function.
 * @return: returns the TCP listener commpoint. You can find the
 *  	TCP handlers in the array inside the listener commpoint.
 *	returns NULL on error.
 * Inits timeout to NULL. All handlers are on the free list.
 */
struct comm_point* comm_point_create_tcp(struct comm_base* base,
	int fd, int num, size_t bufsize, 
	comm_point_callback_t* callback, void* callback_arg);

/**
 * Create an outgoing TCP commpoint. No file descriptor is opened, left at -1.
 * @param base: in which base to alloc the commpoint.
 * @param bufsize: size of buffer to create for handlers.
 * @param callback: callback function pointer for the handler.
 * @param callback_arg: will be passed to your callback function.
 * @return: the commpoint or NULL on error.
 */
struct comm_point* comm_point_create_tcp_out(struct comm_base* base,
	size_t bufsize, comm_point_callback_t* callback, void* callback_arg);

/**
 * Create commpoint to listen to a local domain file descriptor.
 * @param base: in which base to alloc the commpoint.
 * @param fd: file descriptor of open AF_UNIX socket set to listen nonblocking.
 * @param bufsize: size of buffer to create for handlers.
 * @param callback: callback function pointer for the handler.
 * @param callback_arg: will be passed to your callback function.
 * @return: the commpoint or NULL on error.
 */
struct comm_point* comm_point_create_local(struct comm_base* base,
	int fd, size_t bufsize, 
	comm_point_callback_t* callback, void* callback_arg);

/**
 * Create commpoint to listen to a local domain pipe descriptor.
 * @param base: in which base to alloc the commpoint.
 * @param fd: file descriptor.
 * @param writing: true if you want to listen to writes, false for reads.
 * @param callback: callback function pointer for the handler.
 * @param callback_arg: will be passed to your callback function.
 * @return: the commpoint or NULL on error.
 */
struct comm_point* comm_point_create_raw(struct comm_base* base,
	int fd, int writing, 
	comm_point_callback_t* callback, void* callback_arg);

/**
 * Close a comm point fd.
 * @param c: comm point to close.
 */
void comm_point_close(struct comm_point* c);

/**
 * Close and deallocate (free) the comm point. If the comm point is
 * a tcp-accept point, also its tcp-handler points are deleted.
 * @param c: comm point to delete.
 */
void comm_point_delete(struct comm_point* c);

/**
 * Send reply. Put message into commpoint buffer.
 * @param repinfo: The reply info copied from a commpoint callback call.
 */
void comm_point_send_reply(struct comm_reply* repinfo);

/**
 * Drop reply. Cleans up.
 * @param repinfo: The reply info copied from a commpoint callback call.
 */
void comm_point_drop_reply(struct comm_reply* repinfo);

/**
 * Send an udp message over a commpoint.
 * @param c: commpoint to send it from.
 * @param packet: what to send.
 * @param addr: where to send it to.
 * @param addrlen: length of addr.
 * @return: false on a failure.
 */
int comm_point_send_udp_msg(struct comm_point* c, struct sldns_buffer* packet,
	struct sockaddr* addr, socklen_t addrlen);

/**
 * Stop listening for input on the commpoint. No callbacks will happen.
 * @param c: commpoint to disable. The fd is not closed.
 */
void comm_point_stop_listening(struct comm_point* c);

/**
 * Start listening again for input on the comm point.
 * @param c: commpoint to enable again.
 * @param newfd: new fd, or -1 to leave fd be.
 * @param sec: timeout in seconds, or -1 for no (change to the) timeout.
 */
void comm_point_start_listening(struct comm_point* c, int newfd, int sec);

/**
 * Stop listening and start listening again for reading or writing.
 * @param c: commpoint
 * @param rd: if true, listens for reading.
 * @param wr: if true, listens for writing.
 */
void comm_point_listen_for_rw(struct comm_point* c, int rd, int wr);

/**
 * Get size of memory used by comm point.
 * For TCP handlers this includes subhandlers.
 * For UDP handlers, this does not include the (shared) UDP buffer.
 * @param c: commpoint.
 * @return size in bytes.
 */
size_t comm_point_get_mem(struct comm_point* c);

/**
 * create timer. Not active upon creation.
 * @param base: event handling base.
 * @param cb: callback function: void myfunc(void* myarg);
 * @param cb_arg: user callback argument.
 * @return: the new timer or NULL on error.
 */
struct comm_timer* comm_timer_create(struct comm_base* base, 
	void (*cb)(void*), void* cb_arg);

/**
 * disable timer. Stops callbacks from happening.
 * @param timer: to disable.
 */
void comm_timer_disable(struct comm_timer* timer);

/**
 * reset timevalue for timer.
 * @param timer: timer to (re)set.
 * @param tv: when the timer should activate. if NULL timer is disabled.
 */
void comm_timer_set(struct comm_timer* timer, struct timeval* tv);

/**
 * delete timer.
 * @param timer: to delete.
 */
void comm_timer_delete(struct comm_timer* timer);

/**
 * see if timeout has been set to a value.
 * @param timer: the timer to examine.
 * @return: false if disabled or not set.
 */
int comm_timer_is_set(struct comm_timer* timer);

/**
 * Get size of memory used by comm timer.
 * @param timer: the timer to examine.
 * @return size in bytes.
 */
size_t comm_timer_get_mem(struct comm_timer* timer);

/**
 * Create a signal handler. Call signal_bind() later to bind to a signal.
 * @param base: communication base to use.
 * @param callback: called when signal is caught.
 * @param cb_arg: user argument to callback
 * @return: the signal struct or NULL on error.
 */
struct comm_signal* comm_signal_create(struct comm_base* base,
	void (*callback)(int, void*), void* cb_arg);

/**
 * Bind signal struct to catch a signal. A signle comm_signal can be bound
 * to multiple signals, calling comm_signal_bind multiple times.
 * @param comsig: the communication point, with callback information.
 * @param sig: signal number.
 * @return: true on success. false on error.
 */
int comm_signal_bind(struct comm_signal* comsig, int sig);

/**
 * Delete the signal communication point.
 * @param comsig: to delete.
 */
void comm_signal_delete(struct comm_signal* comsig);

/**
 * perform accept(2) with error checking.
 * @param c: commpoint with accept fd.
 * @param addr: remote end returned here.
 * @param addrlen: length of remote end returned here.
 * @return new fd, or -1 on error.
 *	if -1, error message has been printed if necessary, simply drop
 *	out of the reading handler.
 */
int comm_point_perform_accept(struct comm_point* c, 
	struct sockaddr_storage* addr, socklen_t* addrlen);

/**** internal routines ****/

/**
 * This routine is published for checks and tests, and is only used internally.
 * handle libevent callback for udp comm point.
 * @param fd: file descriptor.
 * @param event: event bits from libevent: 
 *	EV_READ, EV_WRITE, EV_SIGNAL, EV_TIMEOUT.
 * @param arg: the comm_point structure.
 */
void comm_point_udp_callback(int fd, short event, void* arg);

/**
 * This routine is published for checks and tests, and is only used internally.
 * handle libevent callback for udp ancillary data comm point.
 * @param fd: file descriptor.
 * @param event: event bits from libevent: 
 *	EV_READ, EV_WRITE, EV_SIGNAL, EV_TIMEOUT.
 * @param arg: the comm_point structure.
 */
void comm_point_udp_ancil_callback(int fd, short event, void* arg);

/**
 * This routine is published for checks and tests, and is only used internally.
 * handle libevent callback for tcp accept comm point
 * @param fd: file descriptor.
 * @param event: event bits from libevent: 
 *	EV_READ, EV_WRITE, EV_SIGNAL, EV_TIMEOUT.
 * @param arg: the comm_point structure.
 */
void comm_point_tcp_accept_callback(int fd, short event, void* arg);

/**
 * This routine is published for checks and tests, and is only used internally.
 * handle libevent callback for tcp data comm point
 * @param fd: file descriptor.
 * @param event: event bits from libevent: 
 *	EV_READ, EV_WRITE, EV_SIGNAL, EV_TIMEOUT.
 * @param arg: the comm_point structure.
 */
void comm_point_tcp_handle_callback(int fd, short event, void* arg);

/**
 * This routine is published for checks and tests, and is only used internally.
 * handle libevent callback for timer comm.
 * @param fd: file descriptor (always -1).
 * @param event: event bits from libevent: 
 *	EV_READ, EV_WRITE, EV_SIGNAL, EV_TIMEOUT.
 * @param arg: the comm_timer structure.
 */
void comm_timer_callback(int fd, short event, void* arg);

/**
 * This routine is published for checks and tests, and is only used internally.
 * handle libevent callback for signal comm.
 * @param fd: file descriptor (used for the signal number).
 * @param event: event bits from libevent: 
 *	EV_READ, EV_WRITE, EV_SIGNAL, EV_TIMEOUT.
 * @param arg: the internal commsignal structure.
 */
void comm_signal_callback(int fd, short event, void* arg);

/**
 * This routine is published for checks and tests, and is only used internally.
 * libevent callback for AF_UNIX fds
 * @param fd: file descriptor.
 * @param event: event bits from libevent: 
 *	EV_READ, EV_WRITE, EV_SIGNAL, EV_TIMEOUT.
 * @param arg: the comm_point structure.
 */
void comm_point_local_handle_callback(int fd, short event, void* arg);

/**
 * This routine is published for checks and tests, and is only used internally.
 * libevent callback for raw fd access.
 * @param fd: file descriptor.
 * @param event: event bits from libevent: 
 *	EV_READ, EV_WRITE, EV_SIGNAL, EV_TIMEOUT.
 * @param arg: the comm_point structure.
 */
void comm_point_raw_handle_callback(int fd, short event, void* arg);

/**
 * This routine is published for checks and tests, and is only used internally.
 * libevent callback for timeout on slow accept.
 * @param fd: file descriptor.
 * @param event: event bits from libevent: 
 *	EV_READ, EV_WRITE, EV_SIGNAL, EV_TIMEOUT.
 * @param arg: the comm_point structure.
 */
void comm_base_handle_slow_accept(int fd, short event, void* arg);

#ifdef USE_WINSOCK
/**
 * Callback for openssl BIO to on windows detect WSAEWOULDBLOCK and notify
 * the winsock_event of this for proper TCP nonblocking implementation.
 * @param c: comm_point, fd must be set its struct event is registered.
 * @param ssl: openssl SSL, fd must be set so it has a bio.
 */
void comm_point_tcp_win_bio_cb(struct comm_point* c, void* ssl);
#endif

/** see if errno for tcp connect has to be logged or not. This uses errno */
int tcp_connect_errno_needs_log(struct sockaddr* addr, socklen_t addrlen);

#endif /* NET_EVENT_H */