[tor-bugs] #15515 [Tor]: Don't allow multiple INTRODUCE1s on the same circuit

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#15515: Don't allow multiple INTRODUCE1s on the same circuit
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     Reporter:  asn      |      Owner:
         Type:  defect   |     Status:  needs_review
     Priority:  normal   |  Milestone:  Tor: 0.2.6.x-final
    Component:  Tor      |    Version:
   Resolution:           |   Keywords:  026-backport 025-backport
Actual Points:           |  024-backport
       Points:           |  Parent ID:  #15463
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Comment (by dgoulet):

 Replying to [comment:9 asn]:
 > Replying to [comment:3 asn]:
 > > some more thoughts:
 > > 16:31 < qwerty1> maybe it would be better to return 0 instead of goto
 err
 > > 16:31 < qwerty1> if they get a nack they will know to try a new
 circuit
 > > 16:32 < asn> qwerty1: hm plausible. maybe we should also not waste
 cells for them.
 >
 > As discussed yesterday, I implemented this alternative behavior in a
 fixup commit on my branch `bug15515_025` which is based on nick's rebase.
 Basically, it marks the circuit as closed and does not send a NAK, if we
 detect multiple `INTRODUCE1` cells.
 >
 > The fixup commit should probably also be applied on master. It should
 apply cleanly I think.

 lgtm. ACK.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/15515#comment:12>
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