rephist: Introduce a fraction and period for overload onionskin (9a473720) · Commits · Gus / Tor

src/feature/nodelist/networkstatus.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -1666,6 +1666,7 @@ notify_before_networkstatus_changes(const networkstatus_t *old_c,
		dos_consensus_has_changed(new_c);
		relay_consensus_has_changed(new_c);
		hs_dos_consensus_has_changed(new_c);
		rep_hist_consensus_has_changed(new_c);
		}

		/* Called after a new consensus has been put in the global state. It is safe

src/feature/relay/onion_queue.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -191,8 +191,6 @@ onion_pending_add(or_circuit_t circ, create_cell_t onionskin)
		rep_hist_note_circuit_handshake_dropped(queue_idx);
		if (queue_idx == ONION_HANDSHAKE_TYPE_NTOR) {
		char *m;
		/* Note this ntor onionskin drop as an overload */
		rep_hist_note_overload(OVERLOAD_GENERAL);
		if ((m = rate_limit_log(&last_warned, approx_time()))) {
		log_warn(LD_GENERAL,
		"Your computer is too slow to handle this many circuit "

src/feature/stats/rephist.c

+143 −2

Original line number	Diff line number	Diff line
		@@ -2062,6 +2062,56 @@ STATIC int onion_handshakes_assigned[MAX_ONION_STAT_TYPE+1] = {0};
		static uint64_t stats_n_onionskin_assigned[MAX_ONION_STAT_TYPE+1] = {0};
		static uint64_t stats_n_onionskin_dropped[MAX_ONION_STAT_TYPE+1] = {0};

		/* We use a scale here so we can represent percentages with decimal points by
		* scaling the value by this factor and so 0.5% becomes a value of 500.
		* Default is 1% and thus min and max range is 0 to 100%. */
		#define OVERLOAD_ONIONSKIN_NTOR_PERCENT_SCALE 1000.0
		#define OVERLOAD_ONIONSKIN_NTOR_PERCENT_DEFAULT 1000
		#define OVERLOAD_ONIONSKIN_NTOR_PERCENT_MIN 0
		#define OVERLOAD_ONIONSKIN_NTOR_PERCENT_MAX 100000

		/** Consensus parameter: indicate what fraction of ntor onionskin drop over the
		* total number of requests must be reached before we trigger a general
		* overload signal.*/
		static double overload_onionskin_ntor_fraction =
		OVERLOAD_ONIONSKIN_NTOR_PERCENT_DEFAULT /
		OVERLOAD_ONIONSKIN_NTOR_PERCENT_SCALE / 100.0;

		/* Number of seconds for the assessment period. Default is 6 hours (21600) and
		* the min max range is within a 32bit value. We align this period to the
		* Heartbeat so the logs would match this period more or less. */
		#define OVERLOAD_ONIONSKIN_NTOR_PERIOD_SECS_DEFAULT (60 * 60 * 6)
		#define OVERLOAD_ONIONSKIN_NTOR_PERIOD_SECS_MIN 0
		#define OVERLOAD_ONIONSKIN_NTOR_PERIOD_SECS_MAX INT32_MAX

		/** Consensus parameter: Period, in seconds, over which we count the number of
		* ntor onionskins requests and how many were dropped. After that period, we
		* assess if we trigger an overload or not. */
		static int32_t overload_onionskin_ntor_period_secs =
		OVERLOAD_ONIONSKIN_NTOR_PERIOD_SECS_DEFAULT;

		/** Structure containing information for an assessment period of the onionskin
		* drop overload general signal.
		*
		* It is used to track, within a time period, how many requests we've gotten
		* and how many were dropped. The overload general signal is decided from these
		* depending on some consensus parameters. */
		typedef struct {
		/** Total number of ntor onionskin requested for an assessment period. */
		uint64_t n_ntor_requested;

		/** Total number of dropped ntor onionskins for an assessment period. */
		uint64_t n_ntor_dropped;

		/** When is the next assessment time of the general overload for ntor
		* onionskin drop. Once this time is reached, all stats are reset and this
		* time is set to the next assessment time. */
		time_t next_assessment_time;
		} overload_onionskin_assessment_t;

		/** Keep track of the onionskin requests for an assessment period. */
		static overload_onionskin_assessment_t overload_onionskin_assessment;

		/**
		* We combine ntorv3 and ntor into the same stat, so we must
		* use this function to covert the cell type to a stat index.
		@@ -2080,11 +2130,75 @@ onionskin_type_to_stat(uint16_t type)
		return type;
		}

		/** Assess our ntor handshake statistics and decide if we need to emit a
		* general overload signal.
		*
		* Regardless of overloaded or not, if the assessment time period has passed,
		* the stats are reset back to 0 and the assessment time period updated.
		*
		* This is called when a ntor handshake is _requested_ because we want to avoid
		* to have an assymetric situation where requested counter is reset to 0 but
		* then a drop happens leading to the drop counter being incremented while the
		* requested counter is 0. */
		static void
		overload_general_onionskin_assessment(void)
		{
		/* Initialize the time. Should be done once. */
		if (overload_onionskin_assessment.next_assessment_time == 0) {
		goto reset;
		}

		/* Not the time yet. */
		if (overload_onionskin_assessment.next_assessment_time > approx_time()) {
		goto done;
		}

		/* Make sure we have enough requests to be able to make a proper assessment.
		* We want to avoid 1 single request/drop to trigger an overload as we want
		* at least the number of requests to be above the scale of our fraction. */
		if (overload_onionskin_assessment.n_ntor_requested <
		OVERLOAD_ONIONSKIN_NTOR_PERCENT_SCALE) {
		goto done;
		}

		/* Lets see if we can signal a general overload. */
		double fraction = (double) overload_onionskin_assessment.n_ntor_dropped /
		(double) overload_onionskin_assessment.n_ntor_requested;
		if (fraction >= overload_onionskin_ntor_fraction) {
		log_notice(LD_HIST, "General overload -> Ntor dropped (%" PRIu64 ") "
		"fraction %.4f%% is above threshold of %.4f%%",
		overload_onionskin_assessment.n_ntor_dropped,
		fraction * 100.0,
		overload_onionskin_ntor_fraction * 100.0);
		rep_hist_note_overload(OVERLOAD_GENERAL);
		}

		reset:
		/* Reset counters for the next period. */
		overload_onionskin_assessment.n_ntor_dropped = 0;
		overload_onionskin_assessment.n_ntor_requested = 0;
		overload_onionskin_assessment.next_assessment_time =
		approx_time() + overload_onionskin_ntor_period_secs;

		done:
		return;
		}

		/** A new onionskin (using the <b>type</b> handshake) has arrived. */
		void
		rep_hist_note_circuit_handshake_requested(uint16_t type)
		{
		onion_handshakes_requested[onionskin_type_to_stat(type)]++;
		uint16_t stat = onionskin_type_to_stat(type);

		onion_handshakes_requested[stat]++;

		/* Only relays get to record requested onionskins. */
		if (stat == ONION_HANDSHAKE_TYPE_NTOR) {
		/* Assess if we've reached the overload general signal. */
		overload_general_onionskin_assessment();

		overload_onionskin_assessment.n_ntor_requested++;
		}
		}

		/** We've sent an onionskin (using the <b>type</b> handshake) to a
		@@ -2101,7 +2215,15 @@ rep_hist_note_circuit_handshake_assigned(uint16_t type)
		void
		rep_hist_note_circuit_handshake_dropped(uint16_t type)
		{
		stats_n_onionskin_dropped[onionskin_type_to_stat(type)]++;
		uint16_t stat = onionskin_type_to_stat(type);

		stats_n_onionskin_dropped[stat]++;

		/* Only relays get to record requested onionskins. */
		if (stat == ONION_HANDSHAKE_TYPE_NTOR) {
		/* Note the dropped ntor in the overload assessment object. */
		overload_onionskin_assessment.n_ntor_dropped++;
		}
		}

		/** Get the circuit handshake value that is requested. */
		@@ -2704,6 +2826,25 @@ rep_hist_free_all(void)
		tor_assert_nonfatal_once(rephist_total_num == 0);
		}

		/** Called just before the consensus will be replaced. Update the consensus
		* parameters in case they changed. */
		void
		rep_hist_consensus_has_changed(const networkstatus_t *ns)
		{
		overload_onionskin_ntor_fraction =
		networkstatus_get_param(ns, "overload_onionskin_ntor_scale_percent",
		OVERLOAD_ONIONSKIN_NTOR_PERCENT_DEFAULT,
		OVERLOAD_ONIONSKIN_NTOR_PERCENT_MIN,
		OVERLOAD_ONIONSKIN_NTOR_PERCENT_MAX) /
		OVERLOAD_ONIONSKIN_NTOR_PERCENT_SCALE / 100.0;

		overload_onionskin_ntor_period_secs =
		networkstatus_get_param(ns, "overload_onionskin_ntor_period_secs",
		OVERLOAD_ONIONSKIN_NTOR_PERIOD_SECS_DEFAULT,
		OVERLOAD_ONIONSKIN_NTOR_PERIOD_SECS_MIN,
		OVERLOAD_ONIONSKIN_NTOR_PERIOD_SECS_MAX);
		}

		#ifdef TOR_UNIT_TESTS
		/* only exists for unit tests: get HSv2 stats object */
		const hs_v2_stats_t *

src/feature/stats/rephist.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -89,6 +89,8 @@ uint64_t rep_hist_get_n_dns_request(int type);
		void rep_hist_note_dns_request(int type);
		void rep_hist_note_dns_error(int type, uint8_t error);

		void rep_hist_consensus_has_changed(const networkstatus_t *ns);

		/** We combine ntor and ntorv3 stats, so we have 3 stat types:
		* tap, fast, and ntor. The max type is ntor (2) */
		#define MAX_ONION_STAT_TYPE ONION_HANDSHAKE_TYPE_NTOR