Re: URGENT: patch needed ASAP for authority bug

[Scott Bennett <bennett@xxxxxxxxxx>]

     On Thu, 15 Apr 2010 09:13:16 -0400 Roger Dingledine <arma@xxxxxxx>
wrote:
>On Thu, Apr 15, 2010 at 07:42:46AM -0500, Scott Bennett wrote:
>>      I believe I spotted an authority bug with pretty severe consequences
>[snip]
>>      Here's what I found.  blutmagie's torrc is set up for a target
>> throughput rate of 18000 KB/s and a maximum burst rate of 24000 KB/s.
>> Olaf noticed that blutmagie was being swamped by a horrendous load of
>> incoming connections nearly all the time, so he tried using
>> MaxAdvertisedBandwidth to reduce the frequency of inbound connections.
>[snip]
>>      The problem lies in the consensus document, where it shows (or did
>> an hour or so ago),
>[snip]
>>      The authorities are currently disregarding the limit published in every
>> node's descriptor and instead are conjuring up their own numbers.  This needs
>> to stop and right away.
>
>This behavior is actually a feature. We cut the latency of the Tor

     You appear to be using the Micro$lop definition of "feature" here. :-(

>network in half by rebalancing the network to send more traffic to the
>relays that could handle it.

     Please produce the evidence in support of such a claim.  Like I wrote
in response to Sebastian earlier, there has certainly been no such effect
visible from here.
>
>See also
>https://blog.torproject.org/blog/torflow-node-capacity-integrity-and-reliability-measurements-hotpets

     That was an interesting read, Roger.  Thank you for the reference.
My assessments (after a single reading) are that the first section looked
very good, especially the analysis of circuit construction failure rates.
Those results are quite valuable and immediately applicable information
to have.  The third section, which describes the exit node security-scanning
project also looks quite good, but it is obvious that that will be an
ongoing project for many years because the potential for further enhancement
seems almost endless.  The middle section, though, while describing a fairly
fancy processing approach, is nevertheless built upon a choice of a useless
source of data, as I continue to point out.
>
>One downside of this new feature is that the old trick we had,
>MaxAdvertisedBandwidth, doesn't as much do what you want.

     Does it do *anything* at all anymore besides adjust what a node
publishes in its descriptor?  It not only doesn't do what we want or
what the documentation still says it does, it also removes some important
operational control from the person most responsible for the node's
operation and its impact upon the system and network in which the node
runs.  That flies in the face of the philosophy prior to this change
of leaving such control of operational characteristics in the hands of
those we wish to encourage to run relays.  If relay operators discover
that they can't limit consumption by tor of one or more resources anymore,
they may choose, or even be forced to choose, to stop running them at all.
     What will be in later versions of tor?  Allocation of exit policies
by the authorities?
>
>But that said, there does seem to be a problem here: we're seeing way
>more directory requests than we were a few weeks ago. That's translating
>into more connections seen by relays.
>
>Is that because we're seeing way more users? Or are Tor clients generating
>more directory requests than they "should"? Hm.
>
     More bad news, I guess, but I don't see any direct connection to
the problems central to this thread so far.  That doesn't mean there isn't
such a connection, but none appears very obvious to me at the moment.


                                  Scott Bennett, Comm. ASMELG, CFIAG
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