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Bug 25705: Don't count circuit path failures as build failures.

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Also emit a rate limited log message when they happen, since they are likely
correlated with other issues.
This commit is contained in:
Mike Perry 2018-04-01 03:52:34 +00:00
parent b116710e31
commit 937260af6a
2 changed files with 39 additions and 11 deletions
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5
changes/bug25705 Normal file
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@ -0,0 +1,5 @@
o Minor bugfixes (circuit path selection):
- Don't count path selection failures as circuit build failures. This
should eliminate cases where Tor blames its guard or the network
for situations like insufficient microdescriptors and/or overly
restrictive torrc settings. Fixes bug 25705; bugfix on 0.3.3.1-alpha.

45
src/or/circuituse.c
View File

@ -1757,6 +1757,39 @@ circuit_build_failed(origin_circuit_t *circ)
* the last hop or an earlier hop. then use this info below.
*/
int failed_at_last_hop = 0;
/* First, check to see if this was a path failure, rather than build
* failure.
*
* Note that we deliberately use circuit_get_cpath_len() (and not
* circuit_get_cpath_opened_len()) because we only want to ensure
* that a full path is *chosen*. This is different than a full path
* being *built*. We only want to count *build* failures below.
*
* Path selection failures can happen spuriously for a number
* of reasons (such as aggressive/invalid user-specified path
* restrictions in the torrc, insufficient microdescriptors, and
* non-user reasons like exitpolicy issues), and so should not be
* counted as failures below.
*/
if (circuit_get_cpath_len(circ) < circ->build_state->desired_path_len) {
static ratelim_t pathfail_limit = RATELIM_INIT(3600);
log_fn_ratelim(&pathfail_limit, LOG_NOTICE, LD_CIRC,
"Our circuit %u (id: %" PRIu32 ") died due to an invalid "
"selected path, purpose %s. This may be a torrc "
"configuration issue, or a bug.",
TO_CIRCUIT(circ)->n_circ_id, circ->global_identifier,
circuit_purpose_to_string(TO_CIRCUIT(circ)->purpose));
/* If the path failed on an RP, retry it. */
if (TO_CIRCUIT(circ)->purpose == CIRCUIT_PURPOSE_S_CONNECT_REND)
hs_circ_retry_service_rendezvous_point(circ);
/* In all other cases, just bail. The rest is just failure accounting
* that we don't want to do */
return;
}
/* If the last hop isn't open, and the second-to-last is, we failed
* at the last hop. */
if (circ->cpath &&
@ -1806,18 +1839,8 @@ circuit_build_failed(origin_circuit_t *circ)
* If we have guard state (new guard API) and our path selection
* code actually chose a full path, then blame the failure of this
* circuit on the guard.
*
* Note that we deliberately use circuit_get_cpath_len() (and not
* circuit_get_cpath_opened_len()) because we only want to ensure
* that a full path is *chosen*. This is different than a full path
* being *built*. We only want to blame *build* failures on this
* guard. Path selection failures can happen spuriously for a number
* of reasons (such as aggressive/invalid user-specified path
* restrictions in the torrc, as well as non-user reasons like
* exitpolicy issues), and so should not be counted here.
*/
if (circ->guard_state &&
circuit_get_cpath_len(circ) >= circ->build_state->desired_path_len)
if (circ->guard_state)
entry_guard_failed(&circ->guard_state);
/* if there are any one-hop streams waiting on this circuit, fail
* them now so they can retry elsewhere. */