Commit 4f3a0e39 authored by Mike Perry's avatar Mike Perry
Browse files

Guard against 0 time delta in BDP calc. 

This can only happen in Shadow, but it will cause issues there.
parent 8052d0c2

src/core/or/congestion_control_common.c

+20 −15
Original line number Diff line number Diff line
@@ -937,10 +937,14 @@ congestion_control_update_circuit_bdp(congestion_control_t *cc, 
      timestamp_usec = peek_timestamp(cc->sendme_arrival_timestamps);

      uint64_t delta = now_usec - timestamp_usec;



      /* The acked data is in sendme_cnt-1 chunks, because we are counting the

       * data that is processed by the other endpoint *between* all of these

       * sendmes. There's one less gap between the sendmes than the number

       * of sendmes. */

      /* In Shadow, the time delta between acks can be 0 if there is no

       * network activity between them. Only update BDP if the delta is

       * non-zero. */

      if (delta > 0) {

        /* The acked data is in sendme_cnt-1 chunks, because we are counting

         * the data that is processed by the other endpoint *between* all of

         * these sendmes. There's one less gap between the sendmes than the

         * number of sendmes. */

        uint64_t cells = (sendme_cnt-1)*cc->sendme_inc;



        /* The bandwidth estimate is cells/delta, which when multiplied
@@ -953,6 +957,7 @@ congestion_control_update_circuit_bdp(congestion_control_t *cc, 
                   n_count_ewma(sendme_rate_bdp, cc->bdp[BDP_ALG_SENDME_RATE],

                                cc->ewma_cwnd_cnt*sendme_acks_per_cwnd(cc));

      }

    }



    /* In-flight BDP will cause the cwnd to drift down when underutilized.

     * It is most useful when the local OR conn is blocked, so we only