secret_id_key

[Roger Dingledine]

On Wed, Jul 08, 2009 at 12:42:55PM +0200, Olaf Selke wrote:
> about three weeks ago my exit node traffic dropped from about 45 MBit/s
> to 10-20 MBit/s. There's no explanation regarding network connectivity
> or server environment. Within the last three weeks the traffic didn't
> recover to the former value > 40 MBit/s until I generated a new
> identity. With a new secret_id_key file the traffic recovered to the old
> value after one day.
> 
> Does anyone have an explanation for this?

About three weeks ago we got an influx of new relays, and many of them
were exit relays. In particular, we got enough that Tor Exits were
allowed to be marked Guards again too.

To understand what I just said, see Sec 3.3 of
https://git.torproject.org/checkout/tor/master/doc/spec/dir-spec.txt
  If the total bandwidth of active non-BadExit Exit servers is less
  than one third of the total bandwidth of all active servers, no Exit is
  listed as a Guard.

So before mid June, relays had either Guard flags or Exit flags but
never both.

My guess is that having both of those flags makes clients less willing
to use you as the middle hop, so your traffic drops.

When you threw away your key, you lost your Guard flag, so the middle-hop
traffic returned.

This is a special case of another bug I've been working on:
http://archives.seul.org/or/cvs/Apr-2009/msg00074.html
which is that the longer you've been a guard, the more clients you
attract, and new guards have almost no clients. That's fixed in Tor
0.2.1.14-rc, but we need most people to upgrade before it matters much.

--Roger