Vidalia feature-spec.txt Desired Feature 3.2
Feature 3.2 in feature-spec.txt states:
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3.2. Circuit latency information
Users are often interested in how their current circuit is performing, so they may be interested to see the additional delay added by routing their traffic through the Tor network. One could imagine an implementation as follows:
Vidalia creates a circuit using the same sequence of nodes in the circuit whose performance we wish to measure. Vidalia then connects to itself through that circuit and sends small chunks of data to itself, measuring the delay between the time the chunk of data is sent and the time it is received. Vidalia is essentially "pinging" itself through a circuit.
A technical problem with the above approach is that, if the user has a firewall configured, it must accept connections from the exit node of the circuit being measured otherwise Vidalia would be unable to connect back to itself. Also, an adversary who can observe the user would see that a Tor exit node is connecting back to the user and sending these "pings", yielding the identity of this user's exit node.
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I believe the statement above concerning a firewall is wrong. Peer-to-peer file sharing networks regularly punch through NAT and firewall devices. The trick would be to open a socket on the user machine and connect to the IP:port of the end point Tor router; at the same time set the connecting socket with the SO_REUSEADDR option and then listen on the same socket for an incoming connection from the Tor end point router.
Trac:
Username: rtoepfer