[tor-bugs] #7678 [Tor]: Check if a stream could send a cell but the circuit hasn't asked it to

[Tor Bug Tracker & Wiki]

#7678: Check if a stream could send a cell but the circuit hasn't asked it to
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 Reporter:  arma         |          Owner:                  
     Type:  enhancement  |         Status:  new             
 Priority:  normal       |      Milestone:  Tor: unspecified
Component:  Tor          |        Version:                  
 Keywords:  tor-relay    |         Parent:                  
   Points:               |   Actualpoints:                  
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 Our #snackbug friend may have encountered a situation where somehow a
 circuit decides to never check again whether a stream had something to
 say, so when the circuit could send more, it doesn't, until the next time
 it gets told to check if any streams are ready to send.

 For example, the exit relay waits with its 'connected' relay cell until a
 new stream is created, and then it suddenly notices that it had one it
 wanted to send.

 Seems like we should sort out exactly what the invariant is supposed to be
 ("if the package window is at least this, and the cell queue is less than
 this water mark, then it should never be the case that a stream on that
 circuit has something ready to send but hasn't sent it"), and check it in
 some smart places and log if it's violated.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/7678>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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