diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/or/relay.c | 35 |
1 files changed, 34 insertions, 1 deletions
diff --git a/src/or/relay.c b/src/or/relay.c index 467f8847c8..7b618baa8b 100644 --- a/src/or/relay.c +++ b/src/or/relay.c @@ -1482,6 +1482,8 @@ circuit_resume_edge_reading_helper(edge_connection_t *first_conn, int packaged_this_round; int cells_on_queue; int cells_per_conn; + int num_streams = 0; + edge_connection_t *chosen_stream = NULL; /* How many cells do we have space for? It will be the minimum of * the number needed to exhaust the package window, and the minimum @@ -1499,7 +1501,38 @@ circuit_resume_edge_reading_helper(edge_connection_t *first_conn, /* Count how many non-marked streams there are that have anything on * their inbuf, and enable reading on all of the connections. */ n_streams = 0; - for (conn=first_conn; conn; conn=conn->next_stream) { + /* This used to start listening on the streams in the order they + * appeared in the linked list. That leads to starvation in the + * event that, for example, our circuit window is almost full, and + * there are lots of streams. Then the first few streams will have + * data read from them, and then the window will close again. When + * it reopens, we would enable reading from the beginning of the list + * again. Instead, we just pick a random stream on the list, and + * enable reading for streams starting at that point (and wrapping + * around as if the list were circular). It would probably be better + * to actually remember which streams we've serviced in the past, but + * this is simple and effective. */ + + /* Select a stream uniformly at random from the linked list. We + * don't need cryptographic randomness here. */ + for(conn = first_conn; conn; conn = conn->next_stream) { + num_streams++; + if((random() % num_streams)==0) chosen_stream = conn; + } + /* Activate reading starting from the chosen stream */ + for (conn=chosen_stream; conn; conn = conn->next_stream) { + /* Start reading for the streams starting from here */ + if (conn->_base.marked_for_close || conn->package_window <= 0) + continue; + if (!layer_hint || conn->cpath_layer == layer_hint) { + connection_start_reading(TO_CONN(conn)); + + if (connection_get_inbuf_len(TO_CONN(conn)) > 0) + ++n_streams; + } + } + /* Go back and do the ones we skipped, circular-style */ + for(conn = first_conn; conn != chosen_stream; conn = conn->next_stream) { if (conn->_base.marked_for_close || conn->package_window <= 0) continue; if (!layer_hint || conn->cpath_layer == layer_hint) { |