From 32e486de97be6f0267c1318298808488baf6e319 Mon Sep 17 00:00:00 2001 From: Nick Mathewson Date: Mon, 19 Jun 2017 15:48:47 -0400 Subject: [PATCH 1/2] Don't expand guard sample set unless consensus is "reasonably live" Fixes what I think is the main root cause of 22400. Bugfix on 0.3.0.1-alpha. --- changes/bug22400_01 | 4 ++++ src/or/entrynodes.c | 15 +++++++++++++++ 2 files changed, 19 insertions(+) create mode 100644 changes/bug22400_01 diff --git a/changes/bug22400_01 b/changes/bug22400_01 new file mode 100644 index 0000000000..454c5f746f --- /dev/null +++ b/changes/bug22400_01 @@ -0,0 +1,4 @@ + o Major bugfixes (entry guards): + - When starting with an old consensus, do not add new entry guards + unless the consensus is "reasonably live" (under 1 day old). Fixes + one root cause of bug 22400; bugfix on 0.3.0.1-alpha. diff --git a/src/or/entrynodes.c b/src/or/entrynodes.c index 5b5e13bced..34dfdcef15 100644 --- a/src/or/entrynodes.c +++ b/src/or/entrynodes.c @@ -1104,6 +1104,21 @@ entry_guards_expand_sample(guard_selection_t *gs) { tor_assert(gs); const or_options_t *options = get_options(); + + if (gs->type != GS_TYPE_BRIDGE) { + networkstatus_t *consensus = networkstatus_get_latest_consensus(); + time_t now = approx_time(); + if (consensus == NULL) { + log_info(LD_GUARD, "Not expanding the sample guard set; we have " + "no consensus."); + return NULL; + } else if (!networkstatus_consensus_reasonably_live(consensus, now)) { + log_info(LD_GUARD, "Not expanding the sample guard set; we have " + "a consensus, but it is far too old."); + return NULL; + } + } + int n_sampled = smartlist_len(gs->sampled_entry_guards); entry_guard_t *added_guard = NULL; int n_usable_filtered_guards = num_reachable_filtered_guards(gs, NULL); From bdd267e74d97cf2672fa2e1e9deb2a33fd755f2c Mon Sep 17 00:00:00 2001 From: Nick Mathewson Date: Thu, 22 Jun 2017 09:28:30 -0400 Subject: [PATCH 2/2] Combine our "don't do this if no consensus" entryguards checks Suggested by asn on 22400 review. --- src/or/entrynodes.c | 45 ++++++++++++++++++++++----------------------- 1 file changed, 22 insertions(+), 23 deletions(-) diff --git a/src/or/entrynodes.c b/src/or/entrynodes.c index 34dfdcef15..aba35e69f7 100644 --- a/src/or/entrynodes.c +++ b/src/or/entrynodes.c @@ -1093,6 +1093,18 @@ select_and_add_guard_item_for_sample(guard_selection_t *gs, return added_guard; } +/** Return true iff we need a consensus to maintain our */ +static int +live_consensus_is_missing(const guard_selection_t *gs) +{ + tor_assert(gs); + if (gs->type == GS_TYPE_BRIDGE) { + /* We don't update bridges from the consensus; they aren't there. */ + return 0; + } + return networkstatus_get_live_consensus(approx_time()) == NULL; +} + /** * Add new guards to the sampled guards in gs until there are * enough usable filtered guards, but never grow the sample beyond its @@ -1105,18 +1117,10 @@ entry_guards_expand_sample(guard_selection_t *gs) tor_assert(gs); const or_options_t *options = get_options(); - if (gs->type != GS_TYPE_BRIDGE) { - networkstatus_t *consensus = networkstatus_get_latest_consensus(); - time_t now = approx_time(); - if (consensus == NULL) { - log_info(LD_GUARD, "Not expanding the sample guard set; we have " - "no consensus."); - return NULL; - } else if (!networkstatus_consensus_reasonably_live(consensus, now)) { - log_info(LD_GUARD, "Not expanding the sample guard set; we have " - "a consensus, but it is far too old."); - return NULL; - } + if (live_consensus_is_missing(gs)) { + log_info(LD_GUARD, "Not expanding the sample guard set; we have " + "no live consensus."); + return NULL; } int n_sampled = smartlist_len(gs->sampled_entry_guards); @@ -1227,18 +1231,13 @@ sampled_guards_update_from_consensus(guard_selection_t *gs) // It's important to use only a live consensus here; we don't want to // make changes based on anything expired or old. - if (gs->type != GS_TYPE_BRIDGE) { - networkstatus_t *ns = networkstatus_get_live_consensus(approx_time()); - - if (! ns) { - log_info(LD_GUARD, "No live consensus; can't update " - "sampled entry guards."); - return; - } else { - log_info(LD_GUARD, "Updating sampled guard status based on received " - "consensus."); - } + if (live_consensus_is_missing(gs)) { + log_info(LD_GUARD, "Not updating the sample guard set; we have " + "no live consensus."); + return; } + log_info(LD_GUARD, "Updating sampled guard status based on received " + "consensus."); int n_changes = 0;