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/*
* 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 "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"

/* 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;
/** 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 deferred_cb 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;
};

/** 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);

/** Free any storage and deallocate any extra data or structures used
in this implementation.
*/
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)

#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. */
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. */
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. */
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()
*/
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. */
int bufferevent_enable_locking_(struct bufferevent *bufev, void *lock);
/** Internal: Increment the reference count on bufev. */
void bufferevent_incref_(struct bufferevent *bufev);
/** Internal: Lock bufev and increase its reference count.
* unlocking it otherwise. */
void bufferevent_incref_and_lock_(struct bufferevent *bufev);
/** Internal: Decrement the reference count on bufev. Returns 1 if it freed
* the bufferevent.*/
int bufferevent_decref_(struct bufferevent *bufev);
/** Internal: Drop the reference count on bufev, freeing as necessary, and
* unlocking it otherwise. Returns 1 if it freed the bufferevent. */
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. */
void bufferevent_run_readcb_(struct bufferevent *bufev);
/** Internal: If callbacks are deferred and we have a write callback, schedule
* a writecb. Otherwise just run the writecb. */
void bufferevent_run_writecb_(struct bufferevent *bufev);
/** Internal: If callbacks are deferred and we have an eventcb, schedule
* it to run with events "what". Otherwise just run the eventcb. */
void bufferevent_run_eventcb_(struct bufferevent *bufev, short what);

/** Internal: Add the event 'ev' with timeout tv, unless tv is set to 0, in
* which case add ev with no timeout. */
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. */
void bufferevent_init_generic_timeout_cbs_(struct bufferevent *bev);
/** Internal use: Delete the ev_read and ev_write callbacks if they're pending.
* Call this from the destructor function. */
int bufferevent_del_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. */
int bufferevent_generic_adj_timeouts_(struct bufferevent *bev);

/** 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. */

int bufferevent_decrement_write_buckets_(struct bufferevent_private *bev,
    ev_ssize_t bytes);
int bufferevent_decrement_read_buckets_(struct bufferevent_private *bev,
    ev_ssize_t bytes);
ev_ssize_t bufferevent_get_read_max_(struct bufferevent_private *bev);
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_ */
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