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/* * Copyright (c) 2012, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file circuitmux.c
* \brief Circuit mux/cell selection abstraction
**/
#include "or.h"
#include "circuitmux.h"
/*
* A circuitmux is a collection of circuits; it tracks which subset
* of the attached circuits are 'active' (i.e., have cells available
* to transmit) and how many cells on each. It expoes three distinct
* interfaces to other components:
*
* To channels, which each have a circuitmux_t, the supported operations
* are:
*
* circuitmux_flush_cells():
*
* Retrieve a cell from one of the active circuits, chosen according to
* the circuitmux_t's cell selection policy.
*
* circuitmux_unlink_all():
*
* The channel is closing down, all circuits must be detached.
*
* To circuits, the exposed operations are:
*
* TODO
*
* To circuit selection policies, the exposed operations are:
*
* TODO
*
* General status inquiries?
*
*/
struct circuitmux_s {
/*
* Double-linked ring of circuits with queued cells waiting for room to
* free up on this connection's outbuf. Every time we pull cells from
* a circuit, we advance this pointer to the next circuit in the ring.
*/
struct circuit_t *active_circuits;
/*
* Priority queue of cell_ewma_t for circuits with queued cells waiting
* for room to free up on this connection's outbuf. Kept in heap order
* according to EWMA.
*
* This is redundant with active_circuits; if we ever decide only to use
* the cell_ewma algorithm for choosing circuits, we can remove
* active_circuits.
*/
smartlist_t *active_circuit_pqueue;
/*
* The tick on which the cell_ewma_ts in active_circuit_pqueue last had
* their ewma values rescaled.
*/
unsigned active_circuit_pqueue_last_recalibrated;
};
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