[tor-commits] [tor/master] Avoid building exit circuits from a consensus with no exits
nickm at torproject.org
nickm at torproject.org
Tue Dec 30 14:08:00 UTC 2014
commit cb94f7534dfd666eb02fd8560621d713177b0f62
Author: teor <teor2345 at gmail.com>
Date: Fri Dec 26 00:31:16 2014 +1100
Avoid building exit circuits from a consensus with no exits
Tor can now build circuits from a consensus with no exits.
But if it tries to build exit circuits, they fail and flood the logs.
The circuit types in the Exit Circuits list below will only be
built if the current consensus has exits. If it doesn't,
only the Internal Circuits will be built. (This can change
with each new consensus.)
Fixes bug #13814, causes fewer path failures due to #13817.
Exit Circuits:
Predicted Exit Circuits
User Traffic Circuits
Most AP Streams
Circuits Marked Exit
Build Timeout Circuits (with exits)
Internal Circuits:
Hidden Service Server Circuits
Hidden Service Client Circuits
Hidden Service AP Streams
Hidden Service Intro Point Streams
Circuits Marked Internal
Build Timeout Circuits (with no exits)
Other Circuits?
---
changes/bug13814-avoid-exit-paths-no-exits | 25 +++++++
src/or/circuituse.c | 98 ++++++++++++++++++++--------
2 files changed, 95 insertions(+), 28 deletions(-)
diff --git a/changes/bug13814-avoid-exit-paths-no-exits b/changes/bug13814-avoid-exit-paths-no-exits
new file mode 100644
index 0000000..8b0446f
--- /dev/null
+++ b/changes/bug13814-avoid-exit-paths-no-exits
@@ -0,0 +1,25 @@
+ o Minor bugfixes:
+ - Avoid building exit circuits from a consensus with no exits
+ Tor can now build circuits from a consensus with no exits.
+ But if it tries to build exit circuits, they fail and flood the logs.
+ The circuit types in the Exit Circuits list below will only be
+ built if the current consensus has exits. If it doesn't,
+ only the Internal Circuits will be built. (This can change
+ with each new consensus.)
+ Fixes bug #13814, causes fewer path failures due to #13817.
+
+ Exit Circuits:
+ Predicted Exit Circuits
+ User Traffic Circuits
+ Most AP Streams
+ Circuits Marked Exit
+ Build Timeout Circuits (with exits)
+
+ Internal Circuits:
+ Hidden Service Server Circuits
+ Hidden Service Client Circuits
+ Hidden Service AP Streams
+ Hidden Service Intro Point Streams
+ Circuits Marked Internal
+ Build Timeout Circuits (with no exits)
+ Other Circuits?
diff --git a/src/or/circuituse.c b/src/or/circuituse.c
index 9057136..015270c 100644
--- a/src/or/circuituse.c
+++ b/src/or/circuituse.c
@@ -1024,9 +1024,11 @@ circuit_predict_and_launch_new(void)
/* Second, see if we need any more exit circuits. */
/* check if we know of a port that's been requested recently
- * and no circuit is currently available that can handle it. */
+ * and no circuit is currently available that can handle it.
+ * Exits (obviously) require an exit circuit. */
if (!circuit_all_predicted_ports_handled(now, &port_needs_uptime,
- &port_needs_capacity)) {
+ &port_needs_capacity)
+ && router_have_consensus_path() == CONSENSUS_PATH_EXIT) {
if (port_needs_uptime)
flags |= CIRCLAUNCH_NEED_UPTIME;
if (port_needs_capacity)
@@ -1038,8 +1040,10 @@ circuit_predict_and_launch_new(void)
return;
}
- /* Third, see if we need any more hidden service (server) circuits. */
- if (num_rend_services() && num_uptime_internal < 3) {
+ /* Third, see if we need any more hidden service (server) circuits.
+ * HS servers only need an internal circuit. */
+ if (num_rend_services() && num_uptime_internal < 3
+ && router_have_consensus_path() != CONSENSUS_PATH_UNKNOWN) {
flags = (CIRCLAUNCH_NEED_CAPACITY | CIRCLAUNCH_NEED_UPTIME |
CIRCLAUNCH_IS_INTERNAL);
log_info(LD_CIRC,
@@ -1050,11 +1054,13 @@ circuit_predict_and_launch_new(void)
return;
}
- /* Fourth, see if we need any more hidden service (client) circuits. */
+ /* Fourth, see if we need any more hidden service (client) circuits.
+ * HS clients only need an internal circuit. */
if (rep_hist_get_predicted_internal(now, &hidserv_needs_uptime,
&hidserv_needs_capacity) &&
((num_uptime_internal<2 && hidserv_needs_uptime) ||
- num_internal<2)) {
+ num_internal<2)
+ && router_have_consensus_path() != CONSENSUS_PATH_UNKNOWN) {
if (hidserv_needs_uptime)
flags |= CIRCLAUNCH_NEED_UPTIME;
if (hidserv_needs_capacity)
@@ -1071,15 +1077,23 @@ circuit_predict_and_launch_new(void)
/* Finally, check to see if we still need more circuits to learn
* a good build timeout. But if we're close to our max number we
* want, don't do another -- we want to leave a few slots open so
- * we can still build circuits preemptively as needed. */
- if (num < MAX_UNUSED_OPEN_CIRCUITS-2 &&
- ! circuit_build_times_disabled() &&
- circuit_build_times_needs_circuits_now(get_circuit_build_times())) {
- flags = CIRCLAUNCH_NEED_CAPACITY;
- log_info(LD_CIRC,
- "Have %d clean circs need another buildtime test circ.", num);
- circuit_launch(CIRCUIT_PURPOSE_C_GENERAL, flags);
- return;
+ * we can still build circuits preemptively as needed.
+ * XXXX make the assumption that build timeout streams should be
+ * created whenever we can build internal circuits. */
+ if (router_have_consensus_path() != CONSENSUS_PATH_UNKNOWN) {
+ if (num < MAX_UNUSED_OPEN_CIRCUITS-2 &&
+ ! circuit_build_times_disabled() &&
+ circuit_build_times_needs_circuits_now(get_circuit_build_times())) {
+ flags = CIRCLAUNCH_NEED_CAPACITY;
+ /* if there are no exits in the consensus, make timeout
+ * circuits internal */
+ if (router_have_consensus_path() == CONSENSUS_PATH_INTERNAL)
+ flags |= CIRCLAUNCH_IS_INTERNAL;
+ log_info(LD_CIRC,
+ "Have %d clean circs need another buildtime test circ.", num);
+ circuit_launch(CIRCUIT_PURPOSE_C_GENERAL, flags);
+ return;
+ }
}
}
@@ -1096,11 +1110,17 @@ circuit_build_needed_circs(time_t now)
{
const or_options_t *options = get_options();
- /* launch a new circ for any pending streams that need one */
- connection_ap_attach_pending();
+ /* launch a new circ for any pending streams that need one
+ * XXXX make the assumption that (some) AP streams (i.e. HS clients)
+ * don't require an exit circuit, review in #13814.
+ * This allows HSs to function in a consensus without exits. */
+ if (router_have_consensus_path() != CONSENSUS_PATH_UNKNOWN)
+ connection_ap_attach_pending();
- /* make sure any hidden services have enough intro points */
- rend_services_introduce();
+ /* make sure any hidden services have enough intro points
+ * HS intro point streams only require an internal circuit */
+ if (router_have_consensus_path() != CONSENSUS_PATH_UNKNOWN)
+ rend_services_introduce();
circuit_expire_old_circs_as_needed(now);
@@ -1632,6 +1652,16 @@ circuit_launch(uint8_t purpose, int flags)
return circuit_launch_by_extend_info(purpose, NULL, flags);
}
+/** DOCDOC */
+static int
+have_enough_path_info(int need_exit)
+{
+ if (need_exit)
+ return router_have_consensus_path() == CONSENSUS_PATH_EXIT;
+ else
+ return router_have_consensus_path() != CONSENSUS_PATH_UNKNOWN
+}
+
/** Launch a new circuit with purpose <b>purpose</b> and exit node
* <b>extend_info</b> (or NULL to select a random exit node). If flags
* contains CIRCLAUNCH_NEED_UPTIME, choose among routers with high uptime. If
@@ -1646,10 +1676,14 @@ circuit_launch_by_extend_info(uint8_t purpose,
{
origin_circuit_t *circ;
int onehop_tunnel = (flags & CIRCLAUNCH_ONEHOP_TUNNEL) != 0;
-
- if (!onehop_tunnel && !router_have_minimum_dir_info()) {
- log_debug(LD_CIRC,"Haven't fetched enough directory info yet; canceling "
- "circuit launch.");
+ int have_path = have_enough_path_info(! (flags & CIRCLAUNCH_IS_INTERNAL) );
+
+ if (!onehop_tunnel && (!router_have_minimum_dir_info() || !have_path)) {
+ log_debug(LD_CIRC,"Haven't %s yet; canceling "
+ "circuit launch.",
+ !router_have_minimum_dir_info() ?
+ "fetched enough directory info" :
+ "received a consensus with exits");
return NULL;
}
@@ -1806,7 +1840,9 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn,
return 1; /* we're happy */
}
- if (!want_onehop && !router_have_minimum_dir_info()) {
+ int have_path = have_enough_path_info(!need_internal);
+
+ if (!want_onehop && (!router_have_minimum_dir_info() || !have_path)) {
if (!connection_get_by_type(CONN_TYPE_DIR)) {
int severity = LOG_NOTICE;
/* FFFF if this is a tunneled directory fetch, don't yell
@@ -1814,14 +1850,20 @@ circuit_get_open_circ_or_launch(entry_connection_t *conn,
if (entry_list_is_constrained(options) &&
entries_known_but_down(options)) {
log_fn(severity, LD_APP|LD_DIR,
- "Application request when we haven't used client functionality "
- "lately. Optimistically trying known %s again.",
+ "Application request when we haven't %s. "
+ "Optimistically trying known %s again.",
+ !router_have_minimum_dir_info() ?
+ "used client functionality lately" :
+ "received a consensus with exits",
options->UseBridges ? "bridges" : "entrynodes");
entries_retry_all(options);
} else if (!options->UseBridges || any_bridge_descriptors_known()) {
log_fn(severity, LD_APP|LD_DIR,
- "Application request when we haven't used client functionality "
- "lately. Optimistically trying directory fetches again.");
+ "Application request when we haven't %s. "
+ "Optimistically trying directory fetches again.",
+ !router_have_minimum_dir_info() ?
+ "used client functionality lately" :
+ "received a consensus with exits");
routerlist_retry_directory_downloads(time(NULL));
}
}
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