[tor-bugs] #11565 [Tor]: Make it clear if circ_id for create cell can be zero with non zero MSB

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#11565: Make it clear if circ_id for create cell can be zero with non zero MSB
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 Reporter:  cypherpunks  |          Owner:
     Type:  defect       |         Status:  new
 Priority:  normal       |      Milestone:
Component:  Tor          |        Version:
 Keywords:               |  Actual Points:
Parent ID:               |         Points:
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 It's unclear if zero circ_id with non zero MSB allowed by specification.
 Why 0x80..00 should be allowed and 0x00..00 shouldn't?
 With current implementation initiator never choose zero circ_id with or
 without set of MSB.
 But command_process_create_cell() refuse only 0x00..00 and passes 0x80..00
 {{{
   if (cell->circ_id == 0) {
     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
            "Received a create cell (type %d) from %s with zero circID; "
            " ignoring.", (int)cell->command,
            channel_get_actual_remote_descr(chan));
     return;
   }
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/11565>
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