[tor-bugs] #16480 [Tor]: connection_write_to_buf: indirect recursion for CONN_TYPE_CONTROL

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#16480: connection_write_to_buf: indirect recursion for CONN_TYPE_CONTROL
-------------------------+---------------------
 Reporter:  cypherpunks  |          Owner:
     Type:  defect       |         Status:  new
 Priority:  normal       |      Milestone:
Component:  Tor          |        Version:
 Keywords:               |  Actual Points:
Parent ID:               |         Points:
-------------------------+---------------------
 Call of `connection_write_to_buf` for CONN_TYPE_CONTROL allows immediate
 flush of the outbuf. Then if code tries to log something and
 `control_event_logmsg` is involved then it call of
 `connection_write_to_buf` recursively. Consequence calls blocked by
 `++disable_log_messages` only then.

 Three ways to fix:
 1. Remove ability for immediate flush of the outbuf by
 `connection_write_to_buf`
 2. Check `in_connection_handle_write` flag at start of
 `connection_handle_write`
 3. Guard call of `connection_handle_write` by `disable_control_logging`
 and `enable_control_logging`

 Every way have negative and positive impacts.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16480>
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