vanishing HSDIR flags

[Sebastian Hahn]

On Aug 21, 2010, at 3:35 PM, Scott Bennett wrote:

> Hi Sebastian,
>     Thanks for responding.
>     On  Sat, 21 Aug 2010 15:17:19 +0200 Sebastian Hahn <mail at sebastianhahn.net 
> >
>> wrote:
>> On Aug 21, 2010, at 1:49 PM, Scott Bennett wrote:
>>
>>>    Yesterday (Friday) the number of relays given HSDir flags by the
>>> directory authorities was reduced by a bit more than 50% from only a
>>> day earlier.  My node, MYCROFTsOtherChild, was and still is among  
>>> the
>>> bereft.  This same situation happened a couple of weeks ago, also
>>> affecting my node.  That time the flag reappeared several hours  
>>> after
>>> I first noticed what had happened.  This time the flag is still
>>> missing.
>>>    It is not obvious to me why the HSDir flag has been stripped from
>>> so many relays, especially relays that have, like mine, been up and
>>> running for weeks since the last restart.  Has a bug been  
>>> triggered in
>>> the authority code?
>>
>> Apparently enough authorities have upgraded to 0.2.2.15-alpha. See
>> the changelog for details.
>>
>     Yes, I see that entry now in the Changelog, although I don't see  
> the
> reasoning behind it.  HSDir requests differ in just about every  
> imaginable
> way from ordinary directory requests.  The protocol is different, the
> HSDir entry format is different, the request frequency is lower by  
> orders
> of magnitude, the requests are--or at least as I recall--intended to  
> be
> handled over internal circuits rather than via a DirPort, and so  
> on.  I
> just don't see any reason to tie the HSDir service to the presence/ 
> absence
> of a DirPort.
>     Also, given the switch from decentralized traffic distribution to
> centralized traffic distribution in recent tor versions, nodes  
> advertising
> throughput capacities of, say, 49 KB/s or less (I don't really know  
> where
> the curve becomes steeper) get little use already.  Given that  
> DirPort is
> ignored when the advertised throughput capacity is less than 50 KB/ 
> s, tying
> HSDir service to the presence/absence of an active DirPort means that
> relatively unused relays cannot even help out with handling the  
> trivial
> traffic volume of HSDir requests.  Doesn't that seem rather  
> counterproductive?

The issue is that there is a bug in relays that checks for the DirPort  
to
be enabled before it answer directory requests, including hsdir
stuff. Before a complete fix for that is developed, the short-term
workaround to make hidden services more stable is to make remove
the nodes without a dirport from the dht. As soon as a fix is
developed, the authorities can start assigning the flag again based on
Tor version.

Sebastian