Re: descriptor lost by authorities?

[Scott Bennett <bennett@xxxxxxxxxx>]

     On Wed, 1 Apr 2009 08:29:48 -0400 Roger Dingledine <arma@xxxxxxx> wrote:
>On Wed, Apr 01, 2009 at 06:59:22AM -0500, Scott Bennett wrote:
>>      In the past several hours, traffic through my tor node has almost stopped.
>> The last time an exit was taken through my node was over three and a half hours
>> ago.  I see that the descriptor for my node, MYCROFTsOtherChild, is no longer
>> in the consensus document nor was it ever distributed back to my node in
>> directory updates.
>
>Hm. moria1 isn't voting for it either, currently.
>
>The last descriptor I have for it is from
>published 2009-03-31 11:24:33
>(GMT) which matches your first log lines.

     Good catch, Roger.  I had copied those lines from a
"tail -f /var/log/tor/info.log|fgrep pload" that I keep running in a spare
xterm.  I should have looked into this further before posting.  Looking at the
actual file, as well as /var/log/messages, I see lots of signs that my network
connection may have failed about an hour earlier.  Then /var/log/messages shows

Apr  1 02:14:35 hellas kernel: bge0: link state changed to DOWN
Apr  1 02:14:36 hellas kernel: bge0: link state changed to UP

after which the messages from inadyn(8) complaining that it can't check the
dyndns.org server stop appearing.  The DOWN-UP sequence suggests that Comcast
had a problem covering a wider area than just my connection, fixed it, and
caused a cable modem reset.
>
>>      The relevant info-level log entries from the last two descriptor
>> updates posted are below.  Timestamps are for CDT.  The first update did work,
>> but the next one at roughly 18 hours later appears to have been ignored or
>> discarded by the authorities.  I would like to know why.
>> 
>> Mar 31 06:24:37.522 [info] directory_post_to_dirservers(): Uploading an extrainfo (length 1978)
>[snip]
>> Apr 01 00:25:03.710 [info] directory_post_to_dirservers(): Uploading an extrainfo (length 1936)
>
>I'd like to know why also. :) There's no hint in moria1's logs about
>rejecting it for whatever reason. Can you post more of your info-level
>logs around the "Apr 01 00:25:03.710" timeframe? (If it's large, no need
>to spam all 1000+ people on this list.)

     If you still want it, I can send that part to you directly, but I doubt
there's much point in it now.
>
>The best theory I've heard so far for this phenomenon is that a brief
>network hiccup around the time of publishing will make you fail to upload,
>and you won't try for another 18 hours (meaning 12 hours of being missing
>from the consensus).

     Yes, that appears to be what happened in this case.
>
>We have some partial plans for having relays recognize when their upload
>failed: see directories_have_accepted_server_descriptor() and look for
>"rejected = 1" in connection_dir_client_reached_eof(), both in
>https://svn.torproject.org/svn/tor/trunk/src/or/directory.c
>but for various reasons we haven't finished that feature yet.

     That would be great to have!  Upon recognizing a failed upload at the
time of the attempt could cause a retry to be scheduled after a delay of
something less than an hour.  However, there is also another situation to
be looked for that would deal with the problem of the relay forgetting to
post.  Upon receiving a new consensus document more than one hour after the
relay was initialized, the relay should check to see whether its own entry.
If that entry is missing, the relay should immediately attempt to post a
descriptor with current values in it.
>
>It would be good to confirm if this is what's going wrong, or if it's
>something else. I'm going to put yet more debugging log messages in,
>both on the relay side and the authority side, to help track this down.
>
     Yeah, all the evidence this time points to a Comcast problem.  My
apologies to the list for the noise.


                                  Scott Bennett, Comm. ASMELG, CFIAG
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