Had this on my relay because I ran out of disk space due to `debug.log` being on. ``` Nov 05 12:39:01.801 [warn] tor_bug_occurred_(): Bug: src/lib/tls/buffers_tls.c:152: buf_flush_to_tls: Non-fatal assertion !(flushlen > *buf_flushlen) failed. (Future instances of this warning will be silenced.) (on Tor 0.4.3.0-alpha-dev 4413b98190d94b54) ``` So the code that exploded is: ``` if (BUG(flushlen > *buf_flushlen)) { flushlen = *buf_flushlen; } ``` It was triggered by lack of disk space for sure. The only thing I can see is if `connection_handle_write_impl()` was called with `force = 1` which happens with `connection_flush()` which makes tor use the bucket limit instead of the outbuf "flushlen" and thus could lead to that assert().