Single hop connections?

Prithula Dhungel prithula.dhungel at
Fri Jun 26 18:39:08 UTC 2009

Hi all,
  Thanks for the quick response. I am starting to do a project related to
Tor that would require me to build 1-hop circuits and communicate from my OP
to a webserver via the one single OR.
I was going though the Tor code and came across this function:

connection_exit_begin_conn(cell_t *cell, circuit_t *circ();

in the file src/or/connection_edge.c

Particularly, in line number: 2252

if (or_circ && or_circ->is_first_hop) {
      /* Don't let clients use us as a single-hop proxy; it attracts
       * and users who'd be better off with, well, single-hop proxies.
             "Attempt to open a stream on first hop of circuit. Closing.");
      end_payload[0] = END_STREAM_REASON_TORPROTOCOL;
      relay_send_command_from_edge(rh.stream_id, circ, RELAY_COMMAND_END,
                                   end_payload, 1, NULL);
      return 0;

I'm afraid this means that no OR will allow an OP to use it as a single-hop
router (except for the director server connections?)

I tried making a one - hop circuit. It worked. However, when I try to attach
a stream to the one-hop circuit, I get a RELAY_CELL_END immediately after I
send a RELAY_SEND_BEGIN on that circuit.

Any suggestions? Maybe I'm getting the code all wrong?


On Fri, Jun 26, 2009 at 12:35 PM, Damian Johnson <atagar1 at> wrote:

> Tor caters to several different audiences. For individuals that want Tor
> for counter-censorship rather than privacy (ex. Chinese users) single-hop
> circuits make a lot of sense, IMHO. It would be faster for them and place
> less load on the Tor network (assuming exit nodes aren't the bottleneck).
> Chinese users use open proxies all the time simply to get around the great
> firewall, and this would allow them to use the Tor network like a big proxy
> grab-bag. If they don't need privacy then making them go through extra hops
> seems a lose-lose for both them and us.
> However, it's not all roses and sunshine. One gotcha dr|z3d brought up on
> irc was: "The point about single hops is that it exposing the node operator
> to inordinate risk of legal pressure." Another issue might be making the
> network appear more desirable to p2p traffic (allowing for more speed
> probably means more abuse in that regard). Cheers! -Damian
> On Fri, Jun 26, 2009 at 8:53 AM, Alberto M. Scattolo <
> thedarkfreesoul at> wrote:
>> Hi Prithula,
>> I'm very new to Tor but I think this is not possible, unless you
>> change Tor source code and force it to do it. With one-hop-circuit you
>> would lose all anonymity. As far as I know Tor needs at least 2 hops
>> but 3 is much better.
>> Why do you want a single-hop circuit?
>> --
>> Alberto Maria Scattolo
>> Google profile:

Prithula Dhungel
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