Monotonize the OOM-killer data timers

In a couple of places, to implement the OOM-circuit-killer defense
against sniper attacks, we have counters to remember the age of
cells or data chunks.  These timers were based on wall clock time,
which can move backwards, thus giving roll-over results for our age
calculation.  This commit creates a low-budget monotonic time, based
on ratcheting gettimeofday(), so that even in the event of a time
rollback, we don't do anything _really_ stupid.

A future version of Tor should update this function to do something
even less stupid here, like employ clock_gettime() or its kin.

3 files changed, 3 insertions, 3 deletions

diff --git a/src/or/buffers.c b/src/or/buffers.c
index 352e60a97..b16ee6efa 100644
--- a/src/or/buffers.c
+++ b/src/or/buffers.c
@@ -632,7 +632,7 @@ buf_add_chunk_with_capacity(buf_t *buf, size_t capacity, int capped)
     chunk = chunk_new_with_alloc_size(preferred_chunk_size(capacity));
   }
 
-  tor_gettimeofday_cached(&now);
+  tor_gettimeofday_cached_monotonic(&now);
   chunk->inserted_time = (uint32_t)tv_to_msec(&now);
 
   if (buf->tail) {
diff --git a/src/or/circuitlist.c b/src/or/circuitlist.c
index 45fc95b56..0534e3555 100644
--- a/src/or/circuitlist.c
+++ b/src/or/circuitlist.c
@@ -1551,7 +1551,7 @@ circuits_handle_oom(size_t current_allocation)
     mem_to_recover = current_allocation - mem_target;
   }
 
-  tor_gettimeofday_cached(&now);
+  tor_gettimeofday_cached_monotonic(&now);
   now_ms = (uint32_t)tv_to_msec(&now);
 
   /* This algorithm itself assumes that you've got enough memory slack
diff --git a/src/or/relay.c b/src/or/relay.c
index e6d0f50ac..4cbc8fa47 100644
--- a/src/or/relay.c
+++ b/src/or/relay.c
@@ -1906,7 +1906,7 @@ cell_queue_append_packed_copy(cell_queue_t *queue, const cell_t *cell)
 {
   struct timeval now;
   packed_cell_t *copy = packed_cell_copy(cell);
-  tor_gettimeofday_cached(&now);
+  tor_gettimeofday_cached_monotonic(&now);
   copy->inserted_time = (uint32_t)tv_to_msec(&now);
 
   /* Remember the time when this cell was put in the queue. */