commit 14ec8b89f83ea9cc4fbc7b8bd24194f5408cfea4 Author: Mike Perry mikeperry-git@torproject.org Date: Wed May 8 00:40:49 2019 +0000
Bug 29085: Avoid monotime usage for rtt estimates if it is not in use. --- src/core/or/circuitpadding.c | 25 +++++++++++++++++++++---- src/test/test_circuitpadding.c | 1 + 2 files changed, 22 insertions(+), 4 deletions(-)
diff --git a/src/core/or/circuitpadding.c b/src/core/or/circuitpadding.c index eeedbc124..7674f3510 100644 --- a/src/core/or/circuitpadding.c +++ b/src/core/or/circuitpadding.c @@ -1547,10 +1547,26 @@ circpad_estimate_circ_rtt_on_received(circuit_t *circ, ", %d) after two back to back packets. Current RTT: %d", circ->n_chan ? circ->n_chan->global_identifier : 0, circ->n_circ_id, mi->rtt_estimate_usec); - mi->stop_rtt_update = 1; + mi->stop_rtt_update = 1; + + if (!mi->rtt_estimate_usec) { + static ratelim_t rtt_lim = RATELIM_INIT(600); + log_fn_ratelim(&rtt_lim,LOG_NOTICE,LD_BUG, + "Circuit got two cells back to back before estimating RTT."); + } } } else { - mi->last_received_time_usec = monotime_absolute_usec(); + const circpad_state_t *state = circpad_machine_current_state(mi); + + /* Since monotime is unpredictably expensive, only update this field + * if rtt estimates are needed. Otherwise, stop the rtt update. */ + if (state->use_rtt_estimate) { + mi->last_received_time_usec = monotime_absolute_usec(); + } else { + /* Let's fast-path future decisions not to update rtt if the + * feature is not in use. */ + mi->stop_rtt_update = 1; + } } }
@@ -1610,8 +1626,9 @@ circpad_estimate_circ_rtt_on_send(circuit_t *circ, mi->stop_rtt_update = 1;
if (!mi->rtt_estimate_usec) { - log_fn(LOG_NOTICE, LD_CIRC, - "Got two cells back to back on a circuit before estimating RTT."); + static ratelim_t rtt_lim = RATELIM_INIT(600); + log_fn_ratelim(&rtt_lim,LOG_NOTICE,LD_BUG, + "Circuit sent two cells back to back before estimating RTT."); } } } diff --git a/src/test/test_circuitpadding.c b/src/test/test_circuitpadding.c index b7dbf022a..13371df68 100644 --- a/src/test/test_circuitpadding.c +++ b/src/test/test_circuitpadding.c @@ -415,6 +415,7 @@ helper_create_basic_machine(void)
circ_client_machine.states[CIRCPAD_STATE_START]. next_state[CIRCPAD_EVENT_NONPADDING_RECV] = CIRCPAD_STATE_BURST; + circ_client_machine.states[CIRCPAD_STATE_START].use_rtt_estimate = 1;
circ_client_machine.states[CIRCPAD_STATE_BURST]. next_state[CIRCPAD_EVENT_PADDING_RECV] = CIRCPAD_STATE_BURST;