Support for logging Onion Service circuit IDs

Tasks

• Add support for logging Onion Service circuit IDs using the HiddenServiceExportCircuitID C Tor configuration.
• Test the feature.

Specs

Implementation building blocks:

• Protocols:
  • HAProxy's PROXY protocol Versions 1 & 2.
• Software:
  • An EOTK fork with the following changes:
    • Setting C Tor's HiddenServiceExportCircuitID config.
    • Accepting the PROXY Protocol | NGINX Documentation, which may be also available on OpenResty.
    • Including $proxy_protocol_addr into the NGINX logs. It would be safer to include this variable in the end of the log format.

Time estimation

• Complexity: medium (3 days)
• Uncertainty: high (x2)
• Reference (adapted)