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[tor-commits] [tor/release-0.2.5] Move destroy cells into a separate queue type of their own, to save RAM
commit 520cf21793e9c6b662c76c02235315f898d10fb9
Author: Nick Mathewson <nickm@xxxxxxxxxxxxxx>
Date: Tue Dec 19 13:53:52 2017 -0500
Move destroy cells into a separate queue type of their own, to save RAM
We've been seeing problems with destroy cells queues taking up a
huge amount of RAM. We can mitigate this, since while a full packed
destroy cell takes 514 bytes, we only need 5 bytes to remember a
circuit ID and a reason.
Fixes bug 24666. Bugfix on 0.2.5.1-alpha, when destroy cell queues
were introduced.
---
changes/bug24666 | 7 ++++
src/or/circuitmux.c | 34 +++++--------------
src/or/circuitmux.h | 2 +-
src/or/or.h | 15 +++++++++
src/or/relay.c | 82 ++++++++++++++++++++++++++++++++++++++++++++--
src/or/relay.h | 8 +++++
src/test/test_circuitmux.c | 12 +++----
7 files changed, 126 insertions(+), 34 deletions(-)
diff --git a/changes/bug24666 b/changes/bug24666
new file mode 100644
index 000000000..830775f5f
--- /dev/null
+++ b/changes/bug24666
@@ -0,0 +1,7 @@
+ o Minor bugfixes (memory usage):
+
+ - When queuing DESTROY cells on a channel, only queue the
+ circuit-id and reason fields: not the entire 514-byte
+ cell. This fix should help mitigate any bugs or attacks that
+ fill up these queues, and free more RAM for other uses. Fixes
+ bug 24666; bugfix on 0.2.5.1-alpha.
diff --git a/src/or/circuitmux.c b/src/or/circuitmux.c
index e4571ff94..5e28b27bc 100644
--- a/src/or/circuitmux.c
+++ b/src/or/circuitmux.c
@@ -117,7 +117,7 @@ struct circuitmux_s {
struct circuit_t *active_circuits_head, *active_circuits_tail;
/** List of queued destroy cells */
- cell_queue_t destroy_cell_queue;
+ destroy_cell_queue_t destroy_cell_queue;
/** Boolean: True iff the last cell to circuitmux_get_first_active_circuit
* returned the destroy queue. Used to force alternation between
* destroy/non-destroy cells.
@@ -383,7 +383,7 @@ circuitmux_alloc(void)
rv = tor_malloc_zero(sizeof(*rv));
rv->chanid_circid_map = tor_malloc_zero(sizeof(*( rv->chanid_circid_map)));
HT_INIT(chanid_circid_muxinfo_map, rv->chanid_circid_map);
- cell_queue_init(&rv->destroy_cell_queue);
+ destroy_cell_queue_init(&rv->destroy_cell_queue);
return rv;
}
@@ -522,19 +522,10 @@ circuitmux_detach_all_circuits(circuitmux_t *cmux, smartlist_t *detached_out)
void
circuitmux_mark_destroyed_circids_usable(circuitmux_t *cmux, channel_t *chan)
{
- packed_cell_t *cell;
- int n_bad = 0;
+ destroy_cell_t *cell;
TOR_SIMPLEQ_FOREACH(cell, &cmux->destroy_cell_queue.head, next) {
- circid_t circid = 0;
- if (packed_cell_is_destroy(chan, cell, &circid)) {
- channel_mark_circid_usable(chan, circid);
- } else {
- ++n_bad;
- }
+ channel_mark_circid_usable(chan, cell->circid);
}
- if (n_bad)
- log_warn(LD_BUG, "%d cell(s) on destroy queue did not look like a "
- "DESTROY cell.", n_bad);
}
/**
@@ -591,7 +582,7 @@ circuitmux_free(circuitmux_t *cmux)
I64_PRINTF_ARG(global_destroy_ctr));
}
- cell_queue_clear(&cmux->destroy_cell_queue);
+ destroy_cell_queue_clear(&cmux->destroy_cell_queue);
tor_free(cmux);
}
@@ -1469,7 +1460,7 @@ circuitmux_set_num_cells(circuitmux_t *cmux, circuit_t *circ,
circuit_t *
circuitmux_get_first_active_circuit(circuitmux_t *cmux,
- cell_queue_t **destroy_queue_out)
+ destroy_cell_queue_t **destroy_queue_out)
{
circuit_t *circ = NULL;
@@ -1885,14 +1876,7 @@ circuitmux_append_destroy_cell(channel_t *chan,
circid_t circ_id,
uint8_t reason)
{
- cell_t cell;
- memset(&cell, 0, sizeof(cell_t));
- cell.circ_id = circ_id;
- cell.command = CELL_DESTROY;
- cell.payload[0] = (uint8_t) reason;
-
- cell_queue_append_packed_copy(NULL, &cmux->destroy_cell_queue, 0, &cell,
- chan->wide_circ_ids, 0);
+ destroy_cell_queue_append(&cmux->destroy_cell_queue, circ_id, reason);
/* Destroy entering the queue, update counters */
++(cmux->destroy_ctr);
@@ -1925,13 +1909,13 @@ circuitmux_count_queued_destroy_cells(const channel_t *chan,
int64_t manual_total = 0;
int64_t manual_total_in_map = 0;
- packed_cell_t *cell;
+ destroy_cell_t *cell;
TOR_SIMPLEQ_FOREACH(cell, &cmux->destroy_cell_queue.head, next) {
circid_t id;
++manual_total;
- id = packed_cell_get_circid(cell, chan->wide_circ_ids);
+ id = cell->circid;
if (circuit_id_in_use_on_channel(id, (channel_t*)chan))
++manual_total_in_map;
}
diff --git a/src/or/circuitmux.h b/src/or/circuitmux.h
index 2b5fb7e51..468044cec 100644
--- a/src/or/circuitmux.h
+++ b/src/or/circuitmux.h
@@ -127,7 +127,7 @@ int64_t circuitmux_count_queued_destroy_cells(const channel_t *chan,
/* Channel interface */
circuit_t * circuitmux_get_first_active_circuit(circuitmux_t *cmux,
- cell_queue_t **destroy_queue_out);
+ destroy_cell_queue_t **destroy_queue_out);
void circuitmux_notify_xmit_cells(circuitmux_t *cmux, circuit_t *circ,
unsigned int n_cells);
void circuitmux_notify_xmit_destroy(circuitmux_t *cmux);
diff --git a/src/or/or.h b/src/or/or.h
index adf3cfa86..b6a3f62ef 100644
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -1121,6 +1121,21 @@ typedef struct cell_queue_t {
int n; /**< The number of cells in the queue. */
} cell_queue_t;
+/** A single queued destroy cell. */
+typedef struct destroy_cell_t {
+ TOR_SIMPLEQ_ENTRY(destroy_cell_t) next;
+ circid_t circid;
+ uint32_t inserted_time; /** Timestamp when this was queued. */
+ uint8_t reason;
+} destroy_cell_t;
+
+/** A queue of destroy cells on a channel. */
+typedef struct destroy_cell_queue_t {
+ /** Linked list of packed_cell_t */
+ TOR_SIMPLEQ_HEAD(dcell_simpleq, destroy_cell_t) head;
+ int n; /**< The number of cells in the queue. */
+} destroy_cell_queue_t;
+
/** Beginning of a RELAY cell payload. */
typedef struct {
uint8_t command; /**< The end-to-end relay command. */
diff --git a/src/or/relay.c b/src/or/relay.c
index daf354c34..ce9fb934e 100644
--- a/src/or/relay.c
+++ b/src/or/relay.c
@@ -2418,6 +2418,75 @@ cell_queue_pop(cell_queue_t *queue)
return cell;
}
+/** Initialize <b>queue</b> as an empty cell queue. */
+void
+destroy_cell_queue_init(destroy_cell_queue_t *queue)
+{
+ memset(queue, 0, sizeof(destroy_cell_queue_t));
+ TOR_SIMPLEQ_INIT(&queue->head);
+}
+
+/** Remove and free every cell in <b>queue</b>. */
+void
+destroy_cell_queue_clear(destroy_cell_queue_t *queue)
+{
+ destroy_cell_t *cell;
+ while ((cell = TOR_SIMPLEQ_FIRST(&queue->head))) {
+ TOR_SIMPLEQ_REMOVE_HEAD(&queue->head, next);
+ tor_free(cell);
+ }
+ TOR_SIMPLEQ_INIT(&queue->head);
+ queue->n = 0;
+}
+
+/** Extract and return the cell at the head of <b>queue</b>; return NULL if
+ * <b>queue</b> is empty. */
+STATIC destroy_cell_t *
+destroy_cell_queue_pop(destroy_cell_queue_t *queue)
+{
+ destroy_cell_t *cell = TOR_SIMPLEQ_FIRST(&queue->head);
+ if (!cell)
+ return NULL;
+ TOR_SIMPLEQ_REMOVE_HEAD(&queue->head, next);
+ --queue->n;
+ return cell;
+}
+
+/** Append a destroy cell for <b>circid</b> to <b>queue</b>. */
+void
+destroy_cell_queue_append(destroy_cell_queue_t *queue,
+ circid_t circid,
+ uint8_t reason)
+{
+ struct timeval now;
+
+ destroy_cell_t *cell = tor_malloc_zero(sizeof(destroy_cell_t));
+ cell->circid = circid;
+ cell->reason = reason;
+ tor_gettimeofday_cached_monotonic(&now);
+ /* Not yet used, but will be required for OOM handling. */
+ cell->inserted_time = (uint32_t)tv_to_msec(&now);
+
+ TOR_SIMPLEQ_INSERT_TAIL(&queue->head, cell, next);
+ ++queue->n;
+}
+
+/** Convert a destroy_cell_t to a newly allocated cell_t. Frees its input. */
+static packed_cell_t *
+destroy_cell_to_packed_cell(destroy_cell_t *inp, int wide_circ_ids)
+{
+ packed_cell_t *packed = packed_cell_new();
+ cell_t cell;
+ memset(&cell, 0, sizeof(cell));
+ cell.circ_id = inp->circid;
+ cell.command = CELL_DESTROY;
+ cell.payload[0] = inp->reason;
+ cell_pack(packed, &cell, wide_circ_ids);
+
+ tor_free(inp);
+ return packed;
+}
+
/** Return the total number of bytes used for each packed_cell in a queue.
* Approximate. */
size_t
@@ -2596,7 +2665,8 @@ channel_flush_from_first_active_circuit(channel_t *chan, int max)
{
circuitmux_t *cmux = NULL;
int n_flushed = 0;
- cell_queue_t *queue, *destroy_queue=NULL;
+ cell_queue_t *queue;
+ destroy_cell_queue_t *destroy_queue=NULL;
circuit_t *circ;
or_circuit_t *or_circ;
int streams_blocked;
@@ -2611,9 +2681,17 @@ channel_flush_from_first_active_circuit(channel_t *chan, int max)
while (n_flushed < max) {
circ = circuitmux_get_first_active_circuit(cmux, &destroy_queue);
if (destroy_queue) {
+ destroy_cell_t *dcell;
/* this code is duplicated from some of the logic below. Ugly! XXXX */
+ /* If we are given a destroy_queue here, then it is required to be
+ * nonempty... */
tor_assert(destroy_queue->n > 0);
- cell = cell_queue_pop(destroy_queue);
+ dcell = destroy_cell_queue_pop(destroy_queue);
+ /* ...and pop() will always yield a cell from a nonempty queue. */
+ tor_assert(dcell);
+ /* frees dcell */
+ cell = destroy_cell_to_packed_cell(dcell, chan->wide_circ_ids);
+ /* frees cell */
channel_write_packed_cell(chan, cell);
/* Update the cmux destroy counter */
circuitmux_notify_xmit_destroy(cmux);
diff --git a/src/or/relay.h b/src/or/relay.h
index 969c6fb61..9d160b7b9 100644
--- a/src/or/relay.h
+++ b/src/or/relay.h
@@ -63,6 +63,13 @@ void cell_queue_append_packed_copy(circuit_t *circ, cell_queue_t *queue,
void append_cell_to_circuit_queue(circuit_t *circ, channel_t *chan,
cell_t *cell, cell_direction_t direction,
streamid_t fromstream);
+
+void destroy_cell_queue_init(destroy_cell_queue_t *queue);
+void destroy_cell_queue_clear(destroy_cell_queue_t *queue);
+void destroy_cell_queue_append(destroy_cell_queue_t *queue,
+ circid_t circid,
+ uint8_t reason);
+
void channel_unlink_all_circuits(channel_t *chan, smartlist_t *detached_out);
int channel_flush_from_first_active_circuit(channel_t *chan, int max);
void assert_circuit_mux_okay(channel_t *chan);
@@ -101,6 +108,7 @@ STATIC int connection_edge_process_resolved_cell(edge_connection_t *conn,
const relay_header_t *rh);
STATIC packed_cell_t *packed_cell_new(void);
STATIC packed_cell_t *cell_queue_pop(cell_queue_t *queue);
+STATIC destroy_cell_t *destroy_cell_queue_pop(destroy_cell_queue_t *queue);
STATIC size_t cell_queues_get_total_allocation(void);
STATIC int cell_queues_check_size(void);
#endif
diff --git a/src/test/test_circuitmux.c b/src/test/test_circuitmux.c
index b9c0436eb..130be6fc9 100644
--- a/src/test/test_circuitmux.c
+++ b/src/test/test_circuitmux.c
@@ -33,8 +33,9 @@ test_cmux_destroy_cell_queue(void *arg)
circuitmux_t *cmux = NULL;
channel_t *ch = NULL;
circuit_t *circ = NULL;
- cell_queue_t *cq = NULL;
+ destroy_cell_queue_t *cq = NULL;
packed_cell_t *pc = NULL;
+ destroy_cell_t *dc = NULL;
#ifdef ENABLE_MEMPOOLS
init_cell_pool();
@@ -63,11 +64,10 @@ test_cmux_destroy_cell_queue(void *arg)
tt_int_op(cq->n, ==, 3);
- pc = cell_queue_pop(cq);
- tt_assert(pc);
- test_mem_op(pc->body, ==, "\x00\x00\x00\x64\x04\x0a\x00\x00\x00", 9);
- packed_cell_free(pc);
- pc = NULL;
+ dc = destroy_cell_queue_pop(cq);
+ tt_assert(dc);
+ tt_uint_op(dc->circid, ==, 100);
+ tor_free(dc);
tt_int_op(circuitmux_num_cells(cmux), ==, 2);
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