[tor-dev] DEFAULT_ROUTE_LEN [was: Silly (or not so silly) question]

Yawning Angel yawning at schwanenlied.me
Thu Jul 24 21:10:14 UTC 2014

On Thu, 24 Jul 2014 16:48:21 -0400
grarpamp <grarpamp at gmail.com> wrote:

> On Wed, Jul 23, 2014 at 6:34 PM, Roger Dingledine <arma at mit.edu>
> wrote:
> > On Wed, Jul 23, 2014 at 11:24:47PM +0100, Noel David Torres Taño
> > wrote:
> >> What would happen if a Tor node changes behaviour and uses four or
> >> five relay steps instead of three?
> At around DEFAULT_ROUTE_LEN 8 or above I get a lot of these, with
> EXTEND being shown in various command locations, and no connectivity
> to hidden services. Lower values or 4 or 5 probably work just fine
> but I didn't bother testing more than a couple clearnet and onion
> circuits since it's not yet a controller/config tunable and thus takes
> edit/compile/run time. So even my test of 9 > 5 > 7 > 8 take with
> salt. Don't know if this likely represent a bug to test more, or just
> timeouts... the circuits that did work setup in times not feeling
> much more than time/3*LEN. I'd suggest an undocumented tunable and
> unit test if it's worth research/statistic/function_checking purpose.
> relay_send_command_from_edge_(): Bug: Uh-oh.  We're sending a
> RELAY_COMMAND_EXTEND cell, but we have run out of RELAY_EARLY cells on
> that circuit. Commands sent before:
> (unrecognized),(unrecognized),(unrecognized),(unrecognized),EXTEND,EXTEND,(unrecognized)

This is working exactly as specified, and despite the error message, is
not a Bug.  The number of hops each circuit can extend to is limited by
the number of RELAY_EARLY cells allowed per circuit (8), as EXTENDs
that are not contained in RELAY_EARLY are dropped.

Roger linked prop 110, but this is also documented in the tor-spec
(section 5.6).


Yawning Angel
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