tor/src/feature/relay/onion_queue.c

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/* Copyright (c) 2001 Matej Pfajfar.
* Copyright (c) 2001-2004, Roger Dingledine.
* Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
* Copyright (c) 2007-2020, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file onion_queue.c
* \brief Functions to queue create cells for processing.
*
* Relays invoke these functions when they receive a CREATE or EXTEND
* cell in command.c or relay.c, in order to queue the pending request.
* They also invoke them from cpuworker.c, which handles dispatching
* onionskin requests to different worker threads.
*
* <br>
*
* This module also handles:
* <ul>
* <li> Queueing incoming onionskins on the relay side before passing
* them to worker threads.
* <li>Expiring onionskins on the relay side if they have waited for
* too long.
* </ul>
**/
#include "core/or/or.h"
#include "feature/relay/onion_queue.h"
#include "app/config/config.h"
#include "core/mainloop/cpuworker.h"
#include "core/or/circuitlist.h"
#include "core/or/onion.h"
#include "feature/nodelist/networkstatus.h"
#include "core/or/or_circuit_st.h"
/** Type for a linked list of circuits that are waiting for a free CPU worker
* to process a waiting onion handshake. */
typedef struct onion_queue_t {
TOR_TAILQ_ENTRY(onion_queue_t) next;
or_circuit_t *circ;
uint16_t handshake_type;
create_cell_t *onionskin;
time_t when_added;
} onion_queue_t;
/** 5 seconds on the onion queue til we just send back a destroy */
#define ONIONQUEUE_WAIT_CUTOFF 5
/** Array of queues of circuits waiting for CPU workers. An element is NULL
* if that queue is empty.*/
static TOR_TAILQ_HEAD(onion_queue_head_t, onion_queue_t)
ol_list[MAX_ONION_HANDSHAKE_TYPE+1] =
{ TOR_TAILQ_HEAD_INITIALIZER(ol_list[0]), /* tap */
TOR_TAILQ_HEAD_INITIALIZER(ol_list[1]), /* fast */
TOR_TAILQ_HEAD_INITIALIZER(ol_list[2]), /* ntor */
};
/** Number of entries of each type currently in each element of ol_list[]. */
static int ol_entries[MAX_ONION_HANDSHAKE_TYPE+1];
static int num_ntors_per_tap(void);
static void onion_queue_entry_remove(onion_queue_t *victim);
/* XXXX Check lengths vs MAX_ONIONSKIN_{CHALLENGE,REPLY}_LEN.
*
* (By which I think I meant, "make sure that no
* X_ONIONSKIN_CHALLENGE/REPLY_LEN is greater than
* MAX_ONIONSKIN_CHALLENGE/REPLY_LEN." Also, make sure that we can pass
* over-large values via EXTEND2/EXTENDED2, for future-compatibility.*/
/** Return true iff we have room to queue another onionskin of type
* <b>type</b>. */
static int
have_room_for_onionskin(uint16_t type)
{
const or_options_t *options = get_options();
int num_cpus;
uint64_t tap_usec, ntor_usec;
uint64_t ntor_during_tap_usec, tap_during_ntor_usec;
/* If we've got fewer than 50 entries, we always have room for one more. */
if (ol_entries[type] < 50)
return 1;
num_cpus = get_num_cpus(options);
/* Compute how many microseconds we'd expect to need to clear all
* onionskins in various combinations of the queues. */
/* How long would it take to process all the TAP cells in the queue? */
tap_usec = estimated_usec_for_onionskins(
ol_entries[ONION_HANDSHAKE_TYPE_TAP],
ONION_HANDSHAKE_TYPE_TAP) / num_cpus;
/* How long would it take to process all the NTor cells in the queue? */
ntor_usec = estimated_usec_for_onionskins(
ol_entries[ONION_HANDSHAKE_TYPE_NTOR],
ONION_HANDSHAKE_TYPE_NTOR) / num_cpus;
/* How long would it take to process the tap cells that we expect to
* process while draining the ntor queue? */
tap_during_ntor_usec = estimated_usec_for_onionskins(
MIN(ol_entries[ONION_HANDSHAKE_TYPE_TAP],
ol_entries[ONION_HANDSHAKE_TYPE_NTOR] / num_ntors_per_tap()),
ONION_HANDSHAKE_TYPE_TAP) / num_cpus;
/* How long would it take to process the ntor cells that we expect to
* process while draining the tap queue? */
ntor_during_tap_usec = estimated_usec_for_onionskins(
MIN(ol_entries[ONION_HANDSHAKE_TYPE_NTOR],
ol_entries[ONION_HANDSHAKE_TYPE_TAP] * num_ntors_per_tap()),
ONION_HANDSHAKE_TYPE_NTOR) / num_cpus;
/* See whether that exceeds MaxOnionQueueDelay. If so, we can't queue
* this. */
if (type == ONION_HANDSHAKE_TYPE_NTOR &&
(ntor_usec + tap_during_ntor_usec) / 1000 >
(uint64_t)options->MaxOnionQueueDelay)
return 0;
if (type == ONION_HANDSHAKE_TYPE_TAP &&
(tap_usec + ntor_during_tap_usec) / 1000 >
(uint64_t)options->MaxOnionQueueDelay)
return 0;
/* If we support the ntor handshake, then don't let TAP handshakes use
* more than 2/3 of the space on the queue. */
if (type == ONION_HANDSHAKE_TYPE_TAP &&
tap_usec / 1000 > (uint64_t)options->MaxOnionQueueDelay * 2 / 3)
return 0;
return 1;
}
/** Add <b>circ</b> to the end of ol_list and return 0, except
* if ol_list is too long, in which case do nothing and return -1.
*/
int
onion_pending_add(or_circuit_t *circ, create_cell_t *onionskin)
{
onion_queue_t *tmp;
time_t now = time(NULL);
if (onionskin->handshake_type > MAX_ONION_HANDSHAKE_TYPE) {
/* LCOV_EXCL_START
* We should have rejected this far before this point */
log_warn(LD_BUG, "Handshake %d out of range! Dropping.",
onionskin->handshake_type);
return -1;
/* LCOV_EXCL_STOP */
}
tmp = tor_malloc_zero(sizeof(onion_queue_t));
tmp->circ = circ;
tmp->handshake_type = onionskin->handshake_type;
tmp->onionskin = onionskin;
tmp->when_added = now;
if (!have_room_for_onionskin(onionskin->handshake_type)) {
#define WARN_TOO_MANY_CIRC_CREATIONS_INTERVAL (60)
static ratelim_t last_warned =
RATELIM_INIT(WARN_TOO_MANY_CIRC_CREATIONS_INTERVAL);
char *m;
if (onionskin->handshake_type == ONION_HANDSHAKE_TYPE_NTOR &&
(m = rate_limit_log(&last_warned, approx_time()))) {
log_warn(LD_GENERAL,
"Your computer is too slow to handle this many circuit "
"creation requests! Please consider using the "
"MaxAdvertisedBandwidth config option or choosing a more "
"restricted exit policy.%s",m);
tor_free(m);
}
tor_free(tmp);
return -1;
}
++ol_entries[onionskin->handshake_type];
log_info(LD_OR, "New create (%s). Queues now ntor=%d and tap=%d.",
onionskin->handshake_type == ONION_HANDSHAKE_TYPE_NTOR ? "ntor" : "tap",
ol_entries[ONION_HANDSHAKE_TYPE_NTOR],
ol_entries[ONION_HANDSHAKE_TYPE_TAP]);
circ->onionqueue_entry = tmp;
TOR_TAILQ_INSERT_TAIL(&ol_list[onionskin->handshake_type], tmp, next);
/* cull elderly requests. */
while (1) {
onion_queue_t *head = TOR_TAILQ_FIRST(&ol_list[onionskin->handshake_type]);
if (now - head->when_added < (time_t)ONIONQUEUE_WAIT_CUTOFF)
break;
circ = head->circ;
circ->onionqueue_entry = NULL;
onion_queue_entry_remove(head);
log_info(LD_CIRC,
"Circuit create request is too old; canceling due to overload.");
if (! TO_CIRCUIT(circ)->marked_for_close) {
circuit_mark_for_close(TO_CIRCUIT(circ), END_CIRC_REASON_RESOURCELIMIT);
}
}
return 0;
}
/** Return a fairness parameter, to prefer processing NTOR style
* handshakes but still slowly drain the TAP queue so we don't starve
* it entirely. */
static int
num_ntors_per_tap(void)
{
#define DEFAULT_NUM_NTORS_PER_TAP 10
#define MIN_NUM_NTORS_PER_TAP 1
#define MAX_NUM_NTORS_PER_TAP 100000
int result = networkstatus_get_param(NULL, "NumNTorsPerTAP",
DEFAULT_NUM_NTORS_PER_TAP,
MIN_NUM_NTORS_PER_TAP,
MAX_NUM_NTORS_PER_TAP);
tor_assert(result > 0);
return result;
}
/** Choose which onion queue we'll pull from next. If one is empty choose
* the other; if they both have elements, load balance across them but
* favoring NTOR. */
static uint16_t
decide_next_handshake_type(void)
{
/* The number of times we've chosen ntor lately when both were available. */
static int recently_chosen_ntors = 0;
if (!ol_entries[ONION_HANDSHAKE_TYPE_NTOR])
return ONION_HANDSHAKE_TYPE_TAP; /* no ntors? try tap */
if (!ol_entries[ONION_HANDSHAKE_TYPE_TAP]) {
/* Nick wants us to prioritize new tap requests when there aren't
* any in the queue and we've processed k ntor cells since the last
* tap cell. This strategy is maybe a good idea, since it starves tap
* less in the case where tap is rare, or maybe a poor idea, since it
* makes the new tap cell unfairly jump in front of ntor cells that
* got here first. In any case this edge case will only become relevant
* once tap is rare. We should reevaluate whether we like this decision
* once tap gets more rare. */
if (ol_entries[ONION_HANDSHAKE_TYPE_NTOR] &&
recently_chosen_ntors <= num_ntors_per_tap())
++recently_chosen_ntors;
return ONION_HANDSHAKE_TYPE_NTOR; /* no taps? try ntor */
}
/* They both have something queued. Pick ntor if we haven't done that
* too much lately. */
if (++recently_chosen_ntors <= num_ntors_per_tap()) {
return ONION_HANDSHAKE_TYPE_NTOR;
}
/* Else, it's time to let tap have its turn. */
recently_chosen_ntors = 0;
return ONION_HANDSHAKE_TYPE_TAP;
}
/** Remove the highest priority item from ol_list[] and return it, or
* return NULL if the lists are empty.
*/
or_circuit_t *
onion_next_task(create_cell_t **onionskin_out)
{
or_circuit_t *circ;
uint16_t handshake_to_choose = decide_next_handshake_type();
onion_queue_t *head = TOR_TAILQ_FIRST(&ol_list[handshake_to_choose]);
if (!head)
return NULL; /* no onions pending, we're done */
tor_assert(head->circ);
tor_assert(head->handshake_type <= MAX_ONION_HANDSHAKE_TYPE);
// tor_assert(head->circ->p_chan); /* make sure it's still valid */
/* XXX I only commented out the above line to make the unit tests
* more manageable. That's probably not good long-term. -RD */
circ = head->circ;
if (head->onionskin)
--ol_entries[head->handshake_type];
log_info(LD_OR, "Processing create (%s). Queues now ntor=%d and tap=%d.",
head->handshake_type == ONION_HANDSHAKE_TYPE_NTOR ? "ntor" : "tap",
ol_entries[ONION_HANDSHAKE_TYPE_NTOR],
ol_entries[ONION_HANDSHAKE_TYPE_TAP]);
*onionskin_out = head->onionskin;
head->onionskin = NULL; /* prevent free. */
circ->onionqueue_entry = NULL;
onion_queue_entry_remove(head);
return circ;
}
/** Return the number of <b>handshake_type</b>-style create requests pending.
*/
int
onion_num_pending(uint16_t handshake_type)
{
return ol_entries[handshake_type];
}
/** Go through ol_list, find the onion_queue_t element which points to
* circ, remove and free that element. Leave circ itself alone.
*/
void
onion_pending_remove(or_circuit_t *circ)
{
onion_queue_t *victim;
if (!circ)
return;
victim = circ->onionqueue_entry;
if (victim)
onion_queue_entry_remove(victim);
cpuworker_cancel_circ_handshake(circ);
}
/** Remove a queue entry <b>victim</b> from the queue, unlinking it from
* its circuit and freeing it and any structures it owns.*/
static void
onion_queue_entry_remove(onion_queue_t *victim)
{
if (victim->handshake_type > MAX_ONION_HANDSHAKE_TYPE) {
/* LCOV_EXCL_START
* We should have rejected this far before this point */
log_warn(LD_BUG, "Handshake %d out of range! Dropping.",
victim->handshake_type);
/* XXX leaks */
return;
/* LCOV_EXCL_STOP */
}
TOR_TAILQ_REMOVE(&ol_list[victim->handshake_type], victim, next);
if (victim->circ)
victim->circ->onionqueue_entry = NULL;
if (victim->onionskin)
--ol_entries[victim->handshake_type];
tor_free(victim->onionskin);
tor_free(victim);
}
/** Remove all circuits from the pending list. Called from tor_free_all. */
void
clear_pending_onions(void)
{
onion_queue_t *victim, *next;
int i;
for (i=0; i<=MAX_ONION_HANDSHAKE_TYPE; i++) {
for (victim = TOR_TAILQ_FIRST(&ol_list[i]); victim; victim = next) {
next = TOR_TAILQ_NEXT(victim,next);
onion_queue_entry_remove(victim);
}
tor_assert(TOR_TAILQ_EMPTY(&ol_list[i]));
}
memset(ol_entries, 0, sizeof(ol_entries));
}