Title: Extending link specifiers to include the directory port
Author: Nick Mathewson
Created: 27 May 2020
Status: Open


Directory ports remain the only way to contact a (non-bridge) Tor relay that isn't expressible as a Link Specifier. We haven't specified a link specifier of this kind so far, since it isn't a way to contact a relay to create a channel.

But authorities still expose directory ports, and encourage relays to use them preferentially for uploading and downloading. And with Walking Onions, it would be convenient to try to make every kind of "address" a link specifier -- we'd like want authorities to be able to specify a list of link specifiers that can be used to contact them for uploads and downloads.

It is possible that after revision, Walking Onions won't need a way to specify this information. If so, this proposal should be moved to "Reserve" status as generally unuseful.


We reserve a new link specifier type "dir-url", for use with the directory system. This is a variable-length link specifier, containing a URL prefix. The only currently supported URL schema is "http://". Implementations SHOULD ignore unrecognized schemas. IPv4 and IPv6 addresses MAY be used directory; hostnames are also allowed. Implementations MAY ignore hostnames and only use raw addresses.

The URL prefix includes everything through the string "tor" in the directory hierarchy.

A dir-url link specifier SHOULD NOT appear in an EXTEND cell; implementations SHOULD reject them if they do appear.