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@@ -967,7 +967,7 @@ entry_guard_learned_bridge_identity(const tor_addr_port_t *addrport,
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* violate it.
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*/
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STATIC int
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-num_reachable_filtered_guards(guard_selection_t *gs,
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+num_reachable_filtered_guards(const guard_selection_t *gs,
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const entry_guard_restriction_t *rst)
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{
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int n_reachable_filtered_guards = 0;
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@@ -1461,6 +1461,94 @@ guard_in_node_family(const entry_guard_t *guard, const node_t *node)
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}
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}
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+/* Allocate and return a new exit guard restriction (where <b>exit_id</b> is of
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+ * size DIGEST_LEN) */
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+STATIC entry_guard_restriction_t *
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+guard_create_exit_restriction(const uint8_t *exit_id)
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+{
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+ entry_guard_restriction_t *rst = NULL;
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+ rst = tor_malloc_zero(sizeof(entry_guard_restriction_t));
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+ rst->type = RST_EXIT_NODE;
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+ memcpy(rst->exclude_id, exit_id, DIGEST_LEN);
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+ return rst;
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+}
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+
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+/** If we have fewer than this many possible usable guards, don't set
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+ * MD-availability-based restrictions: we might blacklist all of them. */
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+#define MIN_GUARDS_FOR_MD_RESTRICTION 10
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+
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+/** Return true if we should set md dirserver restrictions. We might not want
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+ * to set those if our guard options are too restricted, since we don't want
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+ * to blacklist all of them. */
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+static int
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+should_set_md_dirserver_restriction(void)
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+{
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+ const guard_selection_t *gs = get_guard_selection_info();
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+ int num_usable_guards = num_reachable_filtered_guards(gs, NULL);
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+
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+ /* Don't set restriction if too few reachable filtered guards. */
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+ if (num_usable_guards < MIN_GUARDS_FOR_MD_RESTRICTION) {
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+ log_info(LD_GUARD, "Not setting md restriction: only %d"
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+ " usable guards.", num_usable_guards);
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+ return 0;
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+ }
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+
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+ /* We have enough usable guards: set MD restriction */
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+ return 1;
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+}
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+
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+/** Allocate and return an outdated md guard restriction. Return NULL if no
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+ * such restriction is needed. */
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+STATIC entry_guard_restriction_t *
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+guard_create_dirserver_md_restriction(void)
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+{
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+ entry_guard_restriction_t *rst = NULL;
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+
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+ if (!should_set_md_dirserver_restriction()) {
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+ log_debug(LD_GUARD, "Not setting md restriction: too few "
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+ "filtered guards.");
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+ return NULL;
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+ }
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+
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+ rst = tor_malloc_zero(sizeof(entry_guard_restriction_t));
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+ rst->type = RST_OUTDATED_MD_DIRSERVER;
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+
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+ return rst;
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+}
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+
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+/* Return True if <b>guard</b> obeys the exit restriction <b>rst</b>. */
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+static int
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+guard_obeys_exit_restriction(const entry_guard_t *guard,
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+ const entry_guard_restriction_t *rst)
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+{
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+ tor_assert(rst->type == RST_EXIT_NODE);
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+
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+ // Exclude the exit ID and all of its family.
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+ const node_t *node = node_get_by_id((const char*)rst->exclude_id);
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+ if (node && guard_in_node_family(guard, node))
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+ return 0;
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+
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+ return tor_memneq(guard->identity, rst->exclude_id, DIGEST_LEN);
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+}
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+
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+/** Return True if <b>guard</b> should be used as a dirserver for fetching
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+ * microdescriptors. */
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+static int
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+guard_obeys_md_dirserver_restriction(const entry_guard_t *guard)
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+{
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+ /* If this guard is an outdated dirserver, don't use it. */
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+ if (microdesc_relay_is_outdated_dirserver(guard->identity)) {
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+ log_info(LD_GENERAL, "Skipping %s dirserver: outdated",
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+ hex_str(guard->identity, DIGEST_LEN));
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+ return 0;
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+ }
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+
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+ log_debug(LD_GENERAL, "%s dirserver obeys md restrictions",
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+ hex_str(guard->identity, DIGEST_LEN));
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+
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+ return 1;
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+}
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+
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/**
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* Return true iff <b>guard</b> obeys the restrictions defined in <b>rst</b>.
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* (If <b>rst</b> is NULL, there are no restrictions.)
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@@ -1473,13 +1561,14 @@ entry_guard_obeys_restriction(const entry_guard_t *guard,
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if (! rst)
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return 1; // No restriction? No problem.
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- // Only one kind of restriction exists right now: excluding an exit
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- // ID and all of its family.
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- const node_t *node = node_get_by_id((const char*)rst->exclude_id);
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- if (node && guard_in_node_family(guard, node))
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- return 0;
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+ if (rst->type == RST_EXIT_NODE) {
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+ return guard_obeys_exit_restriction(guard, rst);
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+ } else if (rst->type == RST_OUTDATED_MD_DIRSERVER) {
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+ return guard_obeys_md_dirserver_restriction(guard);
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+ }
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- return tor_memneq(guard->identity, rst->exclude_id, DIGEST_LEN);
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+ tor_assert_nonfatal_unreached();
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+ return 0;
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}
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/**
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@@ -2106,7 +2195,7 @@ entry_guard_has_higher_priority(entry_guard_t *a, entry_guard_t *b)
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}
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/** Release all storage held in <b>restriction</b> */
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-static void
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+STATIC void
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entry_guard_restriction_free(entry_guard_restriction_t *rst)
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{
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tor_free(rst);
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@@ -3359,8 +3448,8 @@ guards_choose_guard(cpath_build_state_t *state,
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/* We're building to a targeted exit node, so that node can't be
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* chosen as our guard for this circuit. Remember that fact in a
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* restriction. */
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- rst = tor_malloc_zero(sizeof(entry_guard_restriction_t));
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- memcpy(rst->exclude_id, exit_id, DIGEST_LEN);
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+ rst = guard_create_exit_restriction(exit_id);
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+ tor_assert(rst);
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}
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if (entry_guard_pick_for_circuit(get_guard_selection_info(),
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GUARD_USAGE_TRAFFIC,
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@@ -3412,12 +3501,20 @@ remove_all_entry_guards(void)
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/** Helper: pick a directory guard, with whatever algorithm is used. */
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const node_t *
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-guards_choose_dirguard(circuit_guard_state_t **guard_state_out)
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+guards_choose_dirguard(uint8_t dir_purpose,
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+ circuit_guard_state_t **guard_state_out)
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{
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const node_t *r = NULL;
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+ entry_guard_restriction_t *rst = NULL;
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+
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+ /* If we are fetching microdescs, don't query outdated dirservers. */
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+ if (dir_purpose == DIR_PURPOSE_FETCH_MICRODESC) {
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+ rst = guard_create_dirserver_md_restriction();
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+ }
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+
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if (entry_guard_pick_for_circuit(get_guard_selection_info(),
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GUARD_USAGE_DIRGUARD,
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- NULL,
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+ rst,
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&r,
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guard_state_out) < 0) {
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tor_assert(r == NULL);
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Nick Mathewson