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Implement a placeholder mechanism in the channel,id->circ map

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We'll use this to help fix bug 7912, by providing a way to mark
that a circuit ID can't get reused while a DESTROY is queued but not sent.
This commit is contained in:
Nick Mathewson 2013-03-14 12:13:45 -04:00
parent 42fb61d172
commit 967503c12c
2 changed files with 76 additions and 7 deletions
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81
src/or/circuitlist.c
View File

@ -207,6 +207,61 @@ circuit_set_circid_chan_helper(circuit_t *circ, int direction,
}
}
/** Mark that circuit id <b>id</b> shouldn't be used on channel <b>chan</b>,
* even if there is no circuit on the channel. We use this to keep the
* circuit id from getting re-used while we have queued but not yet sent
* a destroy cell. */
void
channel_mark_circid_unusable(channel_t *chan, circid_t id)
{
chan_circid_circuit_map_t search;
chan_circid_circuit_map_t *ent;
/* See if there's an entry there. That wouldn't be good. */
memset(&search, 0, sizeof(search));
search.chan = chan;
search.circ_id = id;
ent = HT_FIND(chan_circid_map, &chan_circid_map, &search);
if (ent && ent->circuit) {
/* we have a problem. */
log_warn(LD_BUG, "Tried to mark %u unusable on %p, but there was already "
"a circuit there.", (unsigned)id, chan);
} else if (ent) {
/* It's already marked. */
} else {
ent = tor_malloc_zero(sizeof(chan_circid_circuit_map_t));
ent->chan = chan;
ent->circ_id = id;
/* leave circuit at NULL */
HT_INSERT(chan_circid_map, &chan_circid_map, ent);
}
}
/** Mark that a circuit id <b>id</b> can be used again on <b>chan</b>.
* We use this to re-enable the circuit ID after we've sent a destroy cell.
*/
void
channel_mark_circid_usable(channel_t *chan, circid_t id)
{
chan_circid_circuit_map_t search;
chan_circid_circuit_map_t *ent;
/* See if there's an entry there. That wouldn't be good. */
memset(&search, 0, sizeof(search));
search.chan = chan;
search.circ_id = id;
ent = HT_REMOVE(chan_circid_map, &chan_circid_map, &search);
if (ent && ent->circuit) {
log_warn(LD_BUG, "Tried to mark %u usable on %p, but there was already "
"a circuit there.", (unsigned)id, chan);
return;
}
if (_last_circid_chan_ent == ent)
_last_circid_chan_ent = NULL;
tor_free(ent);
}
/** Set the p_conn field of a circuit <b>circ</b>, along
* with the corresponding circuit ID, and add the circuit as appropriate
* to the (chan,id)-\>circuit map. */
@ -928,9 +983,13 @@ circuit_get_by_global_id(uint32_t id)
* - circ-\>n_circ_id or circ-\>p_circ_id is equal to <b>circ_id</b>, and
* - circ is attached to <b>chan</b>, either as p_chan or n_chan.
* Return NULL if no such circuit exists.
*
* If <b>found_entry_out</b> is provided, set it to true if we have a
* placeholder entry for circid/chan, and leave it unset otherwise.
*/
static INLINE circuit_t *
circuit_get_by_circid_channel_impl(circid_t circ_id, channel_t *chan)
circuit_get_by_circid_channel_impl(circid_t circ_id, channel_t *chan,
int *found_entry_out)
{
chan_circid_circuit_map_t search;
chan_circid_circuit_map_t *found;
@ -951,15 +1010,21 @@ circuit_get_by_circid_channel_impl(circid_t circ_id, channel_t *chan)
" circ_id %u, channel ID " U64_FORMAT " (%p)",
found->circuit, (unsigned)circ_id,
U64_PRINTF_ARG(chan->global_identifier), chan);
if (found_entry_out)
*found_entry_out = 1;
return found->circuit;
}
log_debug(LD_CIRC,
"circuit_get_by_circid_channel_impl() found nothing for"
"circuit_get_by_circid_channel_impl() found %s for"
" circ_id %u, channel ID " U64_FORMAT " (%p)",
found ? "placeholder" : "nothing",
(unsigned)circ_id,
U64_PRINTF_ARG(chan->global_identifier), chan);
if (found_entry_out)
*found_entry_out = found ? 1 : 0;
return NULL;
/* The rest of this checks for bugs. Disabled by default. */
/* We comment it out because coverity complains otherwise.
@ -993,7 +1058,7 @@ circuit_get_by_circid_channel_impl(circid_t circ_id, channel_t *chan)
circuit_t *
circuit_get_by_circid_channel(circid_t circ_id, channel_t *chan)
{
circuit_t *circ = circuit_get_by_circid_channel_impl(circ_id, chan);
circuit_t *circ = circuit_get_by_circid_channel_impl(circ_id, chan, NULL);
if (!circ || circ->marked_for_close)
return NULL;
else
@ -1009,7 +1074,7 @@ circuit_t *
circuit_get_by_circid_channel_even_if_marked(circid_t circ_id,
channel_t *chan)
{
return circuit_get_by_circid_channel_impl(circ_id, chan);
return circuit_get_by_circid_channel_impl(circ_id, chan, NULL);
}
/** Return true iff the circuit ID <b>circ_id</b> is currently used by a
@ -1017,7 +1082,9 @@ circuit_get_by_circid_channel_even_if_marked(circid_t circ_id,
int
circuit_id_in_use_on_channel(circid_t circ_id, channel_t *chan)
{
return circuit_get_by_circid_channel_impl(circ_id, chan) != NULL;
int found = 0;
return circuit_get_by_circid_channel_impl(circ_id, chan, &found) != NULL
|| found;
}
/** Return the circuit that a given edge connection is using. */
@ -1585,7 +1652,7 @@ assert_circuit_ok(const circuit_t *c)
/* We use the _impl variant here to make sure we don't fail on marked
* circuits, which would not be returned by the regular function. */
circuit_t *c2 = circuit_get_by_circid_channel_impl(c->n_circ_id,
c->n_chan);
c->n_chan, NULL);
tor_assert(c == c2);
}
}
@ -1593,7 +1660,7 @@ assert_circuit_ok(const circuit_t *c)
if (or_circ->p_circ_id) {
/* ibid */
circuit_t *c2 = circuit_get_by_circid_channel_impl(or_circ->p_circ_id,
or_circ->p_chan);
or_circ->p_chan, NULL);
tor_assert(c == c2);
}
}

2
src/or/circuitlist.h
View File

@ -23,6 +23,8 @@ void circuit_set_p_circid_chan(or_circuit_t *circ, circid_t id,
channel_t *chan);
void circuit_set_n_circid_chan(circuit_t *circ, circid_t id,
channel_t *chan);
void channel_mark_circid_unusable(channel_t *chan, circid_t id);
void channel_mark_circid_usable(channel_t *chan, circid_t id);
void circuit_set_state(circuit_t *circ, uint8_t state);
void circuit_close_all_marked(void);
int32_t circuit_initial_package_window(void);