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Re: [tor-talk] understanding metrics bw graphs

On 05/08/14 01:33, Nusenu wrote:
>>> Which would bring me to the next question (which would be 
>>> required to actually do the required accounting for (b)): Is a 
>>> relay able to tell whether it is being used as first or second 
>>> hop solely by looking at packets (not their source)?
>> Looking at the packet source and comparing it to the list of
>> known relays would probably be the most reliable way for counting
>> bytes as first or second hop.  But this is not implemented, and
>> there are plans to implement this, to the best of my knowledge.
> If relays are unable to tell in which position they are used, how
> does AllowSingleHopExits work? I guess by simple checking if the
> client IP matches an IP in the consensus?

From a quick look at the code: yes.


Relays also distinguish whether a circuit was created using a
CREATE_FAST or a CREATE cell, but that distinction is going away with
CREATE_FAST cells being phased out.  See proposal 221 for details.


So, yes, by comparing the identity presented by the previous hop with
the identities contained in the known consensus.

All the best,
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