[tor-bugs] #5552 [Tor Client]: Reported amount of uploaded data occasionally inflated by several gigabytes

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#5552: Reported amount of uploaded data occasionally inflated by several gigabytes
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 Reporter:  fk          |          Owner:                     
     Type:  defect      |         Status:  new                
 Priority:  normal      |      Milestone:                     
Component:  Tor Client  |        Version:  Tor: 0.2.3.13-alpha
 Keywords:              |         Parent:                     
   Points:              |   Actualpoints:                     
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Comment(by nickm):

 So, the wrap-around issue mentioned in the libevent comment is actually
 safe: It's for if the internal num_read or num_written field in openssl
 overflows past 4GB.  Like, before the call, you have written 2**32 - 100.
 Then you write 200 bytes.  The new value will be 100. So (100 - (2**32 -
 100)) will overflow to 200, which is what we wanted.

 rransom is right that we need to track down the root cause here: anything
 that can add 4GB to the total-written amount will thereby screw up other
 stuff too.  One way to do this would be by adding appropriate asserts to
 bufferevent_ratelim's bufferevent_decrement_write_buckets function in
 ratelim.c, then getting a stack trace once the assertions hit.  That would
 tell us what exactly is decrementing by the insane value, and maybe give
 us a clue on how to fix it.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/5552#comment:5>
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