In `or.h`, we define the reason to close a circuit: ``` /* Reasons why we (or a remote OR) might close a circuit. See tor-spec.txt for * documentation of these. */ #define END_CIRC_REASON_MIN_ 0 #define END_CIRC_REASON_NONE 0 #define END_CIRC_REASON_TORPROTOCOL 1 #define END_CIRC_REASON_INTERNAL 2 #define END_CIRC_REASON_REQUESTED 3 ... ``` Even though it says "See tor-spec.txt", those values aren't defined at all in tor-spec.txt, only the stream reasons are. This is a bit annoying because these values don't have any documentation on why and when they should be used.