[tor-dev] Proposal 185: Directory caches without DirPort

Karsten Loesing karsten.loesing at gmx.net
Fri Sep 23 06:51:39 UTC 2011

Looks like we lost tor-dev somewhere.  Quoting Nick's reply without
cutting out stuff I have no comments to.

On 9/22/11 10:16 PM, Nick Mathewson wrote:
> On Thu, Sep 22, 2011 at 4:49 AM, Karsten Loesing
> <karsten.loesing at gmx.net> wrote:
>> Hi Nick,
>> and here are a few comments to your proposal 185:
>> On 9/20/11 9:34 PM, Nick Mathewson wrote:
>>> Configuration:
>>>   Add a new torrc option, "DirCache".  Its values can be "0", "1",
>>>   and "auto".  If it is 0, we never act as a directory cache, even
>>>   if DirPort is set.
>> Do these relays set "dir-cache 0" in their router descriptors?  Or do
>> they just not include "dir-cache 1"?
> They just do not include "dir-cache 1".  I'll make this more explicit.
>> But if they set a non-zero
>> DirPort, how will the directory authorities and clients know that the
>> node doesn't want to act as a directory cache?
> If you don't want to act as a directory cache, you don't publish DirPort.
> "dir-cache 0" wouldn't work to disable a dirport published in your
> "router" line, since old Tors wouldn't recognize the dir-cache option,
> and so wouldn't know that they weren't supposed to use DirPort.
>>>  If it is 1, then we act as a directory cache
>>>   according to same rules as those used for nodes that set a
>>>   DirPort.  If it is "auto", then Tor decides whether to act as a
>>>   directory cache.
>> What are the rules when setting a DirPort?  Successful self-test and
>> minimum advertised bandwidth?
> I believe so, except of course you don't need to have a reachable
> DirPort in this case.
>> How's "1" different from "auto" if Tor
>> decides whether to act as a directory cache in both cases?
> "1" is "I want to be a directory cache"; "auto" is "use me as a
> directory cache if that would help".  I think that auto might be in
> the future be more adaptive, depending on the state of the network and
> the number of directory caches.
> I would like "DirCache auto" to be something we're comfortable making
> the new default.
>>> Consensus:
>>>   Authorities should assign a "DirCache" flag to all nodes running
>>>   as a directory cache that do not set a DirPort.
>> Would it make sense to have them assign the "DirCache" flag for nodes
>> with a non-zero DirPort, too?
> IMO that would just use up space.  Is there an argument in favor?

Yup, I agree with you that it uses up space.

My thinking was that clients wouldn't have to check two things (non-zero
Dir port or DirCache flag) to learn whether a relay has directory info
for them, but just one thing.  And it could lead to some confusion when
people try to understand dir-spec.txt or the TorStatus output (once it
displays this flag).  Not very strong arguments though.

I also wasn't certain if the proposal was wrong here and you really
meant that the flag would be assigned to all directory caches.  If the
proposal says what you meant, carry on. :)


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