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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"
- /*
- * Private typedefs for circuitmux.c
- */
- /*
- * Map of muxinfos for circuitmux_t to use; struct is defined below (name
- * of struct must match HT_HEAD line).
- */
- typedef struct chanid_circid_muxinfo_map chanid_circid_muxinfo_map_t;
- /*
- * Hash table entry (yeah, calling it chanid_circid_muxinfo_s seems to
- * break the hash table code).
- */
- typedef struct chanid_circid_muxinfo_t chanid_circid_muxinfo_t;
- /*
- * Anything the mux wants to store per-circuit in the map; right now just
- * a count of queued cells.
- */
- typedef struct circuit_muxinfo_s circuit_muxinfo_t;
- /*
- * Structures for circuitmux.c
- */
- /*
- * 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 {
- /* Keep count of attached, active circuits */
- unsigned int n_circuits, n_active_circuits;
- /*
- * Map from (channel ID, circuit ID) pairs to circuit_muxinfo_t
- */
- chanid_circid_muxinfo_map_t *chanid_circid_map;
- /*
- * 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 int active_circuit_pqueue_last_recalibrated;
- };
- /*
- * This struct holds whatever we want to store per attached circuit on a
- * circuitmux_t; right now, just the count of queued cells.
- */
- struct circuit_muxinfo_s {
- unsigned int cell_count;
- };
- /*
- * A map from channel ID and circuit ID to a circuit_muxinfo_t for that
- * circuit.
- */
- struct chanid_circid_muxinfo_t {
- HT_ENTRY(chanid_circid_muxinfo_t) node;
- uint64_t chan_id;
- circid_t circ_id;
- circuit_muxinfo_t muxinfo;
- };
- /*
- * Static function declarations
- */
- static INLINE int
- chanid_circid_entries_eq(chanid_circid_muxinfo_t *a,
- chanid_circid_muxinfo_t *b);
- static INLINE unsigned int
- chanid_circid_entry_hash(chanid_circid_muxinfo_t *a);
- /* Function definitions */
- /**
- * Helper for chanid_circid_cell_count_map_t hash table: compare the channel
- * ID and circuit ID for a and b, and return less than, equal to, or greater
- * than zero appropriately.
- */
- static INLINE int
- chanid_circid_entries_eq(chanid_circid_muxinfo_t *a,
- chanid_circid_muxinfo_t *b)
- {
- return a->chan_id == b->chan_id && a->circ_id == b->circ_id;
- }
- /**
- * Helper: return a hash based on circuit ID and channel ID in a.
- */
- static INLINE unsigned int
- chanid_circid_entry_hash(chanid_circid_muxinfo_t *a)
- {
- return (((unsigned int)(a->circ_id) << 8) ^
- ((unsigned int)((a->chan_id >> 32) & 0xffffffff)) ^
- ((unsigned int)(a->chan_id & 0xffffffff)));
- }
- /* Declare the struct chanid_circid_muxinfo_map type */
- HT_HEAD(chanid_circid_muxinfo_map, chanid_circid_muxinfo_t);
- /* Emit a bunch of hash table stuff */
- HT_PROTOTYPE(chanid_circid_muxinfo_map, chanid_circid_muxinfo_t, node,
- chanid_circid_entry_hash, chanid_circid_entries_eq);
- HT_GENERATE(chanid_circid_muxinfo_map, chanid_circid_muxinfo_t, node,
- chanid_circid_entry_hash, chanid_circid_entries_eq, 0.6,
- malloc, realloc, free);
- /**
- * Allocate a new circuitmux_t
- */
- circuitmux_t *
- circuitmux_alloc(void)
- {
- circuitmux_t *rv = NULL;
- rv = tor_malloc_zero(sizeof(*rv));
- rv->chanid_circid_map = tor_malloc_zero(sizeof(*( rv->chanid_circid_map)));
- HT_INIT(chanid_circid_muxinfo_map, rv->chanid_circid_map);
- return rv;
- }
- /**
- * Free a circuitmux_t; the circuits must be detached first with
- * circuitmux_detach_all_circuits().
- */
- void
- circuitmux_free(circuitmux_t *cmux)
- {
- if (!cmux) return;
- tor_assert(cmux->n_circuits == 0);
- tor_assert(cmux->n_active_circuits == 0);
- smartlist_free(cmux->active_circuit_pqueue);
- if (cmux->chanid_circid_map) {
- HT_CLEAR(chanid_circid_muxinfo_map, cmux->chanid_circid_map);
- tor_free(cmux->chanid_circid_map);
- }
- tor_free(cmux);
- }
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