[tor-bugs] #8111 [Tor]: Refactor our checking of whether we should be reading/writing on a connection to use a set of reason-flags

[Tor Bug Tracker & Wiki]

#8111: Refactor our checking of whether we should be reading/writing on a
connection to use a set of reason-flags
-------------------------+--------------------------------------------------
 Reporter:  nickm        |          Owner:                  
     Type:  enhancement  |         Status:  new             
 Priority:  normal       |      Milestone:  Tor: unspecified
Component:  Tor          |        Version:                  
 Keywords:  tor-relay    |         Parent:                  
   Points:               |   Actualpoints:                  
-------------------------+--------------------------------------------------
 There are plenty of things that can block reading or writing on a
 connection: being out of bandwidth, not having anything more to say,
 having an internal buffer get too full, etc.

 There are too many places where one of the things that would block
 read/write becomes false, and so we check all of the *other* potential
 reasons not to read/write before we re-enable reading/writing.

 There's a much better pattern we could use: have a flags variable for
 "read_blocked" and a flags variable for "write_blocked", each bit of which
 represents a reason not to be reading or writing.  Instead of calling
 connection_{stop,start}_{reading,writing} directly, we would call
 {un,}block_{reading,writing}(conn, reason), which would set or clear a bit
 corresponding to 'reason', and block/unblock reading/writing accordingly.

 I haven't yet verified that this is a win; we should audit all the uses of
 connection_{stop,start}_{reading,writing} reading to see.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/8111>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online