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I changed the DoSCircuitCreationBurst value in my torrc and this BUG() was triggered:

Feb 02 21:52:55.902 [warn] tor_bug_occurred_(): Bug: src/or/dos.c:312: cc_stats_refill_bucket: Non-fatal assertion new_circuit_bucket_count >= stats->circuit_bucket failed. (on Tor 0.3.3.1-alpha-dev eafa252b26ecf83a)
Feb 02 21:52:55.903 [warn] Bug: Non-fatal assertion new_circuit_bucket_count >= stats->circuit_bucket failed in cc_stats_refill_bucket at src/or/dos.c:312. Stack trace: (on Tor 0.3.3.1-alpha-dev eafa252b26ecf83a)
Feb 02 21:52:55.903 [warn] Bug:     /root/git/tor/src/or/tor(log_backtrace+0x42) [0x557248c2bbd2] (on Tor 0.3.3.1-alpha-dev eafa252b26ecf83a)
Feb 02 21:52:55.903 [warn] Bug:     /root/git/tor/src/or/tor(tor_bug_occurred_+0xb9) [0x557248c46f69] (on Tor 0.3.3.1-alpha-dev eafa252b26ecf83a)
Feb 02 21:52:55.903 [warn] Bug:     /root/git/tor/src/or/tor(dos_cc_new_create_cell+0x263) [0x557248bf1e63] (on Tor 0.3.3.1-alpha-dev eafa252b26ecf83a)

This is because of:

  /* This function is not allowed to make the bucket count smaller */
  tor_assert_nonfatal(new_circuit_bucket_count >= stats->circuit_bucket);

We actually can make it smaller if the Burst or Rate is changed at runtime.