Bug report #5231 mentions cannibalized circuits:

This can happen when we cannibalize a circuit which has already been cannibalized.

What are cannibalized circuits and how they're used in Tor? And why a spooky term like cannibalization?

For those who wants to check the related code, circuit_find_to_cannibalize seems like a good starting point.

1 Answer 1


Tor often builds circuits well in advance of actually needing them. This speeds up various operations since building circuits are quite expensive and time consuming. Circuits it has build are earmarked for a specific purpose, say making exit connections out of the Tor network.

If Tor wants to do some specific operation (say connect to an introduction point) but does not have a pre-built circuit for a specific purpose, it may instead use a circuit it prepared for another job if that one hasn't been used yet. That's what Tor calls cannabalizing.

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