/*      $NetBSD: bufferevent-internal.h,v 1.6 2024/08/18 20:47:20 christos Exp $        */

/*
* Copyright (c) 2008-2012 Niels Provos and Nick Mathewson
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. The name of the author may not be used to endorse or promote products
*    derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
*/
#ifndef BUFFEREVENT_INTERNAL_H_INCLUDED_
#define BUFFEREVENT_INTERNAL_H_INCLUDED_

#ifdef __cplusplus
extern "C" {
#endif

#include "event2/event-config.h"
#include "event2/event_struct.h"
#include "evconfig-private.h"
#include "event2/util.h"
#include "defer-internal.h"
#include "evthread-internal.h"
#include "event2/thread.h"
#include "ratelim-internal.h"
#include "event2/bufferevent_struct.h"

#include "ipv6-internal.h"
#ifdef _WIN32
#include <ws2tcpip.h>
#endif
#ifdef EVENT__HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef EVENT__HAVE_NETINET_IN6_H
#include <netinet/in6.h>
#endif

/* These flags are reasons that we might be declining to actually enable
  reading or writing on a bufferevent.
*/

/* On a all bufferevents, for reading: used when we have read up to the
  watermark value.

  On a filtering bufferevent, for writing: used when the underlying
  bufferevent's write buffer has been filled up to its watermark
  value.
*/
#define BEV_SUSPEND_WM 0x01
/* On a base bufferevent: when we have emptied a bandwidth buckets */
#define BEV_SUSPEND_BW 0x02
/* On a base bufferevent: when we have emptied the group's bandwidth bucket. */
#define BEV_SUSPEND_BW_GROUP 0x04
/* On a socket bufferevent: can't do any operations while we're waiting for
* name lookup to finish. */
#define BEV_SUSPEND_LOOKUP 0x08
/* On a base bufferevent, for reading: used when a filter has choked this
* (underlying) bufferevent because it has stopped reading from it. */
#define BEV_SUSPEND_FILT_READ 0x10

typedef ev_uint16_t bufferevent_suspend_flags;

struct bufferevent_rate_limit_group {
       /** List of all members in the group */
       LIST_HEAD(rlim_group_member_list, bufferevent_private) members;
       /** Current limits for the group. */
       struct ev_token_bucket rate_limit;
       struct ev_token_bucket_cfg rate_limit_cfg;

       /** True iff we don't want to read from any member of the group.until
        * the token bucket refills.  */
       unsigned read_suspended : 1;
       /** True iff we don't want to write from any member of the group.until
        * the token bucket refills.  */
       unsigned write_suspended : 1;
       /** True iff we were unable to suspend one of the bufferevents in the
        * group for reading the last time we tried, and we should try
        * again. */
       unsigned pending_unsuspend_read : 1;
       /** True iff we were unable to suspend one of the bufferevents in the
        * group for writing the last time we tried, and we should try
        * again. */
       unsigned pending_unsuspend_write : 1;

       /*@{*/
       /** Total number of bytes read or written in this group since last
        * reset. */
       ev_uint64_t total_read;
       ev_uint64_t total_written;
       /*@}*/

       /** The number of bufferevents in the group. */
       int n_members;

       /** The smallest number of bytes that any member of the group should
        * be limited to read or write at a time. */
       ev_ssize_t min_share;
       ev_ssize_t configured_min_share;

       /** Timeout event that goes off once a tick, when the bucket is ready
        * to refill. */
       struct event master_refill_event;

       /** Seed for weak random number generator. Protected by 'lock' */
       struct evutil_weakrand_state weakrand_seed;

       /** Lock to protect the members of this group.  This lock should nest
        * within every bufferevent lock: if you are holding this lock, do
        * not assume you can lock another bufferevent. */
       void *lock;
};

/** Fields for rate-limiting a single bufferevent. */
struct bufferevent_rate_limit {
       /* Linked-list elements for storing this bufferevent_private in a
        * group.
        *
        * Note that this field is supposed to be protected by the group
        * lock */
       LIST_ENTRY(bufferevent_private) next_in_group;
       /** The rate-limiting group for this bufferevent, or NULL if it is
        * only rate-limited on its own. */
       struct bufferevent_rate_limit_group *group;

       /* This bufferevent's current limits. */
       struct ev_token_bucket limit;
       /* Pointer to the rate-limit configuration for this bufferevent.
        * Can be shared.  XXX reference-count this? */
       struct ev_token_bucket_cfg *cfg;

       /* Timeout event used when one this bufferevent's buckets are
        * empty. */
       struct event refill_bucket_event;
};

/** Parts of the bufferevent structure that are shared among all bufferevent
* types, but not exposed in bufferevent_struct.h. */
struct bufferevent_private {
       /** The underlying bufferevent structure. */
       struct bufferevent bev;

       /** Evbuffer callback to enforce watermarks on input. */
       struct evbuffer_cb_entry *read_watermarks_cb;

       /** If set, we should free the lock when we free the bufferevent. */
       unsigned own_lock : 1;

       /** Flag: set if we have deferred callbacks and a read callback is
        * pending. */
       unsigned readcb_pending : 1;
       /** Flag: set if we have deferred callbacks and a write callback is
        * pending. */
       unsigned writecb_pending : 1;
       /** Flag: set if we are currently busy connecting. */
       unsigned connecting : 1;
       /** Flag: set if a connect failed prematurely; this is a hack for
        * getting around the bufferevent abstraction. */
       unsigned connection_refused : 1;
       /** Set to the events pending if we have deferred callbacks and
        * an events callback is pending. */
       short eventcb_pending;

       /** If set, read is suspended until one or more conditions are over.
        * The actual value here is a bitfield of those conditions; see the
        * BEV_SUSPEND_* flags above. */
       bufferevent_suspend_flags read_suspended;

       /** If set, writing is suspended until one or more conditions are over.
        * The actual value here is a bitfield of those conditions; see the
        * BEV_SUSPEND_* flags above. */
       bufferevent_suspend_flags write_suspended;

       /** Set to the current socket errno if we have deferred callbacks and
        * an events callback is pending. */
       int errno_pending;

       /** The DNS error code for bufferevent_socket_connect_hostname */
       int dns_error;

       /** Used to implement deferred callbacks */
       struct event_callback deferred;

       /** The options this bufferevent was constructed with */
       enum bufferevent_options options;

       /** Current reference count for this bufferevent. */
       int refcnt;

       /** Lock for this bufferevent.  Shared by the inbuf and the outbuf.
        * If NULL, locking is disabled. */
       void *lock;

       /** No matter how big our bucket gets, don't try to read more than this
        * much in a single read operation. */
       ev_ssize_t max_single_read;

       /** No matter how big our bucket gets, don't try to write more than this
        * much in a single write operation. */
       ev_ssize_t max_single_write;

       /** Rate-limiting information for this bufferevent */
       struct bufferevent_rate_limit *rate_limiting;

       /* Saved conn_addr, to extract IP address from it.
        *
        * Because some servers may reset/close connection without waiting clients,
        * in that case we can't extract IP address even in close_cb.
        * So we need to save it, just after we connected to remote server, or
        * after resolving (to avoid extra dns requests during retrying, since UDP
        * is slow) */
       union {
               struct sockaddr_in6 in6;
               struct sockaddr_in in;
       } conn_address;

       struct evdns_getaddrinfo_request *dns_request;
};

/** Possible operations for a control callback. */
enum bufferevent_ctrl_op {
       BEV_CTRL_SET_FD,
       BEV_CTRL_GET_FD,
       BEV_CTRL_GET_UNDERLYING,
       BEV_CTRL_CANCEL_ALL
};

/** Possible data types for a control callback */
union bufferevent_ctrl_data {
       void *ptr;
       evutil_socket_t fd;
};

/**
  Implementation table for a bufferevent: holds function pointers and other
  information to make the various bufferevent types work.
*/
struct bufferevent_ops {
       /** The name of the bufferevent's type. */
       const char *type;
       /** At what offset into the implementation type will we find a
           bufferevent structure?

           Example: if the type is implemented as
           struct bufferevent_x {
              int extra_data;
              struct bufferevent bev;
           }
           then mem_offset should be offsetof(struct bufferevent_x, bev)
       */
       off_t mem_offset;

       /** Enables one or more of EV_READ|EV_WRITE on a bufferevent.  Does
           not need to adjust the 'enabled' field.  Returns 0 on success, -1
           on failure.
        */
       int (*enable)(struct bufferevent *, short);

       /** Disables one or more of EV_READ|EV_WRITE on a bufferevent.  Does
           not need to adjust the 'enabled' field.  Returns 0 on success, -1
           on failure.
        */
       int (*disable)(struct bufferevent *, short);

       /** Detatches the bufferevent from related data structures. Called as
        * soon as its reference count reaches 0. */
       void (*unlink)(struct bufferevent *);

       /** Free any storage and deallocate any extra data or structures used
           in this implementation. Called when the bufferevent is
           finalized.
        */
       void (*destruct)(struct bufferevent *);

       /** Called when the timeouts on the bufferevent have changed.*/
       int (*adj_timeouts)(struct bufferevent *);

       /** Called to flush data. */
       int (*flush)(struct bufferevent *, short, enum bufferevent_flush_mode);

       /** Called to access miscellaneous fields. */
       int (*ctrl)(struct bufferevent *, enum bufferevent_ctrl_op, union bufferevent_ctrl_data *);

};

extern const struct bufferevent_ops bufferevent_ops_socket;
extern const struct bufferevent_ops bufferevent_ops_filter;
extern const struct bufferevent_ops bufferevent_ops_pair;

#define BEV_IS_SOCKET(bevp) ((bevp)->be_ops == &bufferevent_ops_socket)
#define BEV_IS_FILTER(bevp) ((bevp)->be_ops == &bufferevent_ops_filter)
#define BEV_IS_PAIR(bevp) ((bevp)->be_ops == &bufferevent_ops_pair)

#if defined(EVENT__HAVE_OPENSSL)
extern const struct bufferevent_ops bufferevent_ops_openssl;
#define BEV_IS_OPENSSL(bevp) ((bevp)->be_ops == &bufferevent_ops_openssl)
#else
#define BEV_IS_OPENSSL(bevp) 0
#endif

#ifdef _WIN32
extern const struct bufferevent_ops bufferevent_ops_async;
#define BEV_IS_ASYNC(bevp) ((bevp)->be_ops == &bufferevent_ops_async)
#else
#define BEV_IS_ASYNC(bevp) 0
#endif

/** Initialize the shared parts of a bufferevent. */
EVENT2_EXPORT_SYMBOL
int bufferevent_init_common_(struct bufferevent_private *, struct event_base *, const struct bufferevent_ops *, enum bufferevent_options options);

/** For internal use: temporarily stop all reads on bufev, until the conditions
* in 'what' are over. */
EVENT2_EXPORT_SYMBOL
void bufferevent_suspend_read_(struct bufferevent *bufev, bufferevent_suspend_flags what);
/** For internal use: clear the conditions 'what' on bufev, and re-enable
* reading if there are no conditions left. */
EVENT2_EXPORT_SYMBOL
void bufferevent_unsuspend_read_(struct bufferevent *bufev, bufferevent_suspend_flags what);

/** For internal use: temporarily stop all writes on bufev, until the conditions
* in 'what' are over. */
void bufferevent_suspend_write_(struct bufferevent *bufev, bufferevent_suspend_flags what);
/** For internal use: clear the conditions 'what' on bufev, and re-enable
* writing if there are no conditions left. */
void bufferevent_unsuspend_write_(struct bufferevent *bufev, bufferevent_suspend_flags what);

#define bufferevent_wm_suspend_read(b) \
       bufferevent_suspend_read_((b), BEV_SUSPEND_WM)
#define bufferevent_wm_unsuspend_read(b) \
       bufferevent_unsuspend_read_((b), BEV_SUSPEND_WM)

/*
 Disable a bufferevent.  Equivalent to bufferevent_disable(), but
 first resets 'connecting' flag to force EV_WRITE down for sure.

 XXXX this method will go away in the future; try not to add new users.
   See comment in evhttp_connection_reset_() for discussion.

 @param bufev the bufferevent to be disabled
 @param event any combination of EV_READ | EV_WRITE.
 @return 0 if successful, or -1 if an error occurred
 @see bufferevent_disable()
*/
EVENT2_EXPORT_SYMBOL
int bufferevent_disable_hard_(struct bufferevent *bufev, short event);

/** Internal: Set up locking on a bufferevent.  If lock is set, use it.
* Otherwise, use a new lock. */
EVENT2_EXPORT_SYMBOL
int bufferevent_enable_locking_(struct bufferevent *bufev, void *lock);
/** Internal: backwards compat macro for the now public function
* Increment the reference count on bufev. */
#define bufferevent_incref_(bufev) bufferevent_incref(bufev)
/** Internal: Lock bufev and increase its reference count.
* unlocking it otherwise. */
EVENT2_EXPORT_SYMBOL
void bufferevent_incref_and_lock_(struct bufferevent *bufev);
/** Internal: backwards compat macro for the now public function
* Decrement the reference count on bufev.  Returns 1 if it freed
* the bufferevent.*/
#define bufferevent_decref_(bufev) bufferevent_decref(bufev)

/** Internal: Drop the reference count on bufev, freeing as necessary, and
* unlocking it otherwise.  Returns 1 if it freed the bufferevent. */
EVENT2_EXPORT_SYMBOL
int bufferevent_decref_and_unlock_(struct bufferevent *bufev);

/** Internal: If callbacks are deferred and we have a read callback, schedule
* a readcb.  Otherwise just run the readcb. Ignores watermarks. */
EVENT2_EXPORT_SYMBOL
void bufferevent_run_readcb_(struct bufferevent *bufev, int options);
/** Internal: If callbacks are deferred and we have a write callback, schedule
* a writecb.  Otherwise just run the writecb. Ignores watermarks. */
EVENT2_EXPORT_SYMBOL
void bufferevent_run_writecb_(struct bufferevent *bufev, int options);
/** Internal: If callbacks are deferred and we have an eventcb, schedule
* it to run with events "what".  Otherwise just run the eventcb.
* See bufferevent_trigger_event for meaning of "options". */
EVENT2_EXPORT_SYMBOL
void bufferevent_run_eventcb_(struct bufferevent *bufev, short what, int options);

/** Internal: Run or schedule (if deferred or options contain
* BEV_TRIG_DEFER_CALLBACKS) I/O callbacks specified in iotype.
* Must already hold the bufev lock. Honors watermarks unless
* BEV_TRIG_IGNORE_WATERMARKS is in options. */
static inline void bufferevent_trigger_nolock_(struct bufferevent *bufev, short iotype, int options);

/* Making this inline since all of the common-case calls to this function in
* libevent use constant arguments. */
static inline void
bufferevent_trigger_nolock_(struct bufferevent *bufev, short iotype, int options)
{
       if ((iotype & EV_READ) && ((options & BEV_TRIG_IGNORE_WATERMARKS) ||
           evbuffer_get_length(bufev->input) >= bufev->wm_read.low))
               bufferevent_run_readcb_(bufev, options);
       if ((iotype & EV_WRITE) && ((options & BEV_TRIG_IGNORE_WATERMARKS) ||
           evbuffer_get_length(bufev->output) <= bufev->wm_write.low))
               bufferevent_run_writecb_(bufev, options);
}

/** Internal: Add the event 'ev' with timeout tv, unless tv is set to 0, in
* which case add ev with no timeout. */
EVENT2_EXPORT_SYMBOL
int bufferevent_add_event_(struct event *ev, const struct timeval *tv);

/* =========
* These next functions implement timeouts for bufferevents that aren't doing
* anything else with ev_read and ev_write, to handle timeouts.
* ========= */
/** Internal use: Set up the ev_read and ev_write callbacks so that
* the other "generic_timeout" functions will work on it.  Call this from
* the constructor function. */
EVENT2_EXPORT_SYMBOL
void bufferevent_init_generic_timeout_cbs_(struct bufferevent *bev);
/** Internal use: Add or delete the generic timeout events as appropriate.
* (If an event is enabled and a timeout is set, we add the event.  Otherwise
* we delete it.)  Call this from anything that changes the timeout values,
* that enabled EV_READ or EV_WRITE, or that disables EV_READ or EV_WRITE. */
EVENT2_EXPORT_SYMBOL
int bufferevent_generic_adj_timeouts_(struct bufferevent *bev);
EVENT2_EXPORT_SYMBOL
int bufferevent_generic_adj_existing_timeouts_(struct bufferevent *bev);

EVENT2_EXPORT_SYMBOL
enum bufferevent_options bufferevent_get_options_(struct bufferevent *bev);

EVENT2_EXPORT_SYMBOL
const struct sockaddr*
bufferevent_socket_get_conn_address_(struct bufferevent *bev);

EVENT2_EXPORT_SYMBOL
void
bufferevent_socket_set_conn_address_fd_(struct bufferevent *bev, evutil_socket_t fd);

EVENT2_EXPORT_SYMBOL
void
bufferevent_socket_set_conn_address_(struct bufferevent *bev, struct sockaddr *addr, size_t addrlen);


/** Internal use: We have just successfully read data into an inbuf, so
* reset the read timeout (if any). */
#define BEV_RESET_GENERIC_READ_TIMEOUT(bev)                             \
       do {                                                            \
               if (evutil_timerisset(&(bev)->timeout_read))            \
                       event_add(&(bev)->ev_read, &(bev)->timeout_read); \
       } while (0)
/** Internal use: We have just successfully written data from an inbuf, so
* reset the read timeout (if any). */
#define BEV_RESET_GENERIC_WRITE_TIMEOUT(bev)                            \
       do {                                                            \
               if (evutil_timerisset(&(bev)->timeout_write))           \
                       event_add(&(bev)->ev_write, &(bev)->timeout_write); \
       } while (0)
#define BEV_DEL_GENERIC_READ_TIMEOUT(bev)       \
               event_del(&(bev)->ev_read)
#define BEV_DEL_GENERIC_WRITE_TIMEOUT(bev)      \
               event_del(&(bev)->ev_write)


/** Internal: Given a bufferevent, return its corresponding
* bufferevent_private. */
#define BEV_UPCAST(b) EVUTIL_UPCAST((b), struct bufferevent_private, bev)

#ifdef EVENT__DISABLE_THREAD_SUPPORT
#define BEV_LOCK(b) EVUTIL_NIL_STMT_
#define BEV_UNLOCK(b) EVUTIL_NIL_STMT_
#else
/** Internal: Grab the lock (if any) on a bufferevent */
#define BEV_LOCK(b) do {                                                \
               struct bufferevent_private *locking =  BEV_UPCAST(b);   \
               EVLOCK_LOCK(locking->lock, 0);                          \
       } while (0)

/** Internal: Release the lock (if any) on a bufferevent */
#define BEV_UNLOCK(b) do {                                              \
               struct bufferevent_private *locking =  BEV_UPCAST(b);   \
               EVLOCK_UNLOCK(locking->lock, 0);                        \
       } while (0)
#endif


/* ==== For rate-limiting. */

EVENT2_EXPORT_SYMBOL
int bufferevent_decrement_write_buckets_(struct bufferevent_private *bev,
   ev_ssize_t bytes);
EVENT2_EXPORT_SYMBOL
int bufferevent_decrement_read_buckets_(struct bufferevent_private *bev,
   ev_ssize_t bytes);
EVENT2_EXPORT_SYMBOL
ev_ssize_t bufferevent_get_read_max_(struct bufferevent_private *bev);
EVENT2_EXPORT_SYMBOL
ev_ssize_t bufferevent_get_write_max_(struct bufferevent_private *bev);

int bufferevent_ratelim_init_(struct bufferevent_private *bev);

#ifdef __cplusplus
}
#endif


#endif /* BUFFEREVENT_INTERNAL_H_INCLUDED_ */