``` Filename: 172-circ-getinfo-option.txt Title: GETINFO controller option for circuit information Author: Damian Johnson Created: 03-June-2010 Status: Reserve Overview: This details an additional GETINFO option that would provide information concerning a relay's current circuits. Motivation: The original proposal was for connection related information, but Jake make the excellent point that any information retrieved from the control port is... 1. completely ineffectual for auditing purposes since either (a) these results can be fetched from netstat already or (b) the information would only be provided via tor and can't be validated. 2. The more useful uses for connection information can be achieved with much less (and safer) information. Hence the proposal is now for circuit based rather than connection based information. This would strip the most controversial and sensitive data entirely (ip addresses, ports, and connection based bandwidth breakdowns) while still being useful for the following purposes: - Basic Relay Usage Questions How is the bandwidth I'm contributing broken down? Is it being evenly distributed or is someone hogging most of it? Do these circuits belong to the hidden service I'm running or something else? Now that I'm using exit policy X am I desirable as an exit, or are most people just using me as a relay? - Debugging Say a relay has a restrictive firewall policy for outbound connections, with the ORPort whitelisted but doesn't realize that tor needs random high ports. Tor would report success ("your orport is reachable - excellent") yet the relay would be nonfunctional. This proposed information would reveal numerous RELAY -> YOU -> UNESTABLISHED circuits, giving a good indicator of what's wrong. - Visualization A nice benefit of visualizing tor's behavior is that it becomes a helpful tool in puzzling out how tor works. For instance, tor spawns numerous client connections at startup (even if unused as a client). As a newcomer to tor these asymmetric (outbound only) connections mystified me for quite a while until until Roger explained their use to me. The proposed TYPE_FLAGS would let controllers clearly label them as being client related, making their purpose a bit clearer. At the moment connection data can only be retrieved via commands like netstat, ss, and lsof. However, providing an alternative via the control port provides several advantages: - scrubbing for private data Raw connection data has no notion of what's sensitive and what is not. The relay's flags and cached consensus can be used to take educated guesses concerning which connections could possibly belong to client or exit traffic, but this is both difficult and inaccurate. Anything provided via the control port can scrubbed to make sure we aren't providing anything we think relay operators should not see. - additional information All connection querying commands strictly provide the ip address and port of connections, and nothing else. However, for the uses listed above the far more interesting attributes are the circuit's type, bandwidth usage and uptime. - improved performance Querying connection data is an expensive activity, especially for busy relays or low end processors (such as mobile devices). Tor already internally knows its circuits, allowing for vastly quicker lookups. - cross platform capability The connection querying utilities mentioned above not only aren't available under Windows, but differ widely among different *nix platforms. FreeBSD in particular takes a very unique approach, dropping important options from netstat and assigning ss to a spreadsheet application instead. A controller interface, however, would provide a uniform means of retrieving this information. Security Implications: This is an open question. This proposal lacks the most controversial pieces of information (ip addresses and ports) and insight into potential threats this would pose would be very welcomed! Specification: The following addition would be made to the control-spec's GETINFO section: "rcirc/id/" -- Provides entry for the associated relay circuit, formatted as: CIRC_ID= CREATED= UPDATED= TYPE= READ= WRITE= none of the parameters contain whitespace, and additional results must be ignored to allow for future expansion. Parameters are defined as follows: CIRC_ID - Unique numeric identifier for the circuit this belongs to. CREATED - Unix timestamp (as seconds since the Epoch) for when the circuit was created. UPDATED - Unix timestamp for when this information was last updated. TYPE - Single character flags indicating attributes in the circuit: (E)ntry : has a connection that doesn't belong to a known Tor server, indicating that this is either the first hop or bridged E(X)it : has been used for at least one exit stream (R)elay : has been extended Rende(Z)vous : is being used for a rendezvous point (I)ntroduction : is being used for a hidden service introduction (N)one of the above: none of the above have happened yet. READ - Total bytes transmitted toward the exit over the circuit. WRITE - Total bytes transmitted toward the client over the circuit. "rcirc/all" -- The 'rcirc/id/*' output for all current circuits, joined by newlines. The following would be included for circ info update events. 4.1.X. Relay circuit status changed The syntax is: "650" SP "RCIRC" SP CircID SP Notice [SP Created SP Updated SP Type SP Read SP Write] CRLF Notice = "NEW" / ; first information being provided for this circuit "UPDATE" / ; update for a previously reported circuit "CLOSED" ; notice that the circuit no longer exists Notice indicating that queryable information on a relay related circuit has changed. If the Notice parameter is either "NEW" or "UPDATE" then this provides the same fields that would be given by calling "GETINFO rcirc/id/" with the CircID. ```