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Diffstat (limited to 'tor-spec.txt')
| -rw-r--r-- | tor-spec.txt | 36 |
1 files changed, 18 insertions, 18 deletions
diff --git a/tor-spec.txt b/tor-spec.txt index b03d3f5..0e9622b 100644 --- a/tor-spec.txt +++ b/tor-spec.txt @@ -1068,28 +1068,28 @@ see tor-design.pdf. 5.1.1. Choosing circuit IDs in create cells - The CircID for a CREATE/CREATE2 cell is an arbitrarily chosen - nonzero integer, selected by the node (OP or OR) that sends the - CREATE/CREATE2 cell. In link protocol 3 or lower, CircIDs are 2 - bytes long; in protocol 4 or higher, CircIDs are 4 bytes long. - - To prevent CircID collisions, when one node sends a CREATE/CREATE2 - cell to another, it chooses from only one half of the possible - values based on the ORs' public identity keys. - - In link protocol version 3 or lower, if the sending node has a lower - key, it chooses a CircID with an MSB of 0; otherwise, it chooses a - CircID with an MSB of 1. (Public keys are compared numerically by - modulus.) With protocol version 3 or lower, a client with no public key - MAY choose any CircID it wishes, since clients never need to process a - CREATE/CREATE2 cell. + The CircID for a CREATE/CREATE2 cell is a nonzero integer, selected + by the node (OP or OR) that sends the CREATE/CREATED2 cell. + Depending on the link protocol version, there are certain rules for + choosing the value of CircID which MUST be obeyed, as implementations + MAY decide to refuse in case of a violation. In link protocol 3 or + lower, CircIDs are 2 bytes long; in protocol 4 or higher, CircIDs are + 4 bytes long. + + In link protocol version 3 or lower, the nodes choose from only one + half of the possible values based on the ORs' public identity keys, + in order to avoid collisions. If the sending node has a lower key, + it chooses a CircID with an MSB of 0; otherwise, it chooses a CircID + with an MSB of 1. (Public keys are compared numerically by modulus.) + A client with no public key MAY choose any CircID it wishes, since + clients never need to process CREATE/CREATE2 cells. In link protocol version 4 or higher, whichever node initiated the - connection sets its MSB to 1, and whichever node didn't initiate the - connection sets its MSB to 0. + connection MUST set its MSB to 1, and whichever node didn't initiate + the connection MUST set its MSB to 0. The CircID value 0 is specifically reserved for cells that do not - belong to any circuit: CircID 0 must not be used for circuits. No + belong to any circuit: CircID 0 MUST not be used for circuits. No other CircID value, including 0x8000 or 0x80000000, is reserved. Existing Tor implementations choose their CircID values at random from |