[tor-dev] Torspec proposal for adding new X- fields to relay descriptor

Damian Johnson atagar at torproject.org
Thu Jul 3 16:29:08 UTC 2014

Hi Virgil. Few quick thoughts...

* Your proposal doesn't mention what descriptor type you're talking
about. I suspect you mean server descriptors but the proposal should
make this clear. Maybe this would be more fitting for the extrainfo

* Please describe in your proposal the use cases that you plan to use
this for. I dislike the idea of expanding descriptors if we don't have
a user of those changes right away ('premature optimization...').

* Addition of fields means larger documents, which in turn means more
load for the authorities, directory mirrors, and clients if they don't
opt for microdescriptors (... which admittedly isn't common). In this
case it's an arbitrary amount of extra content determined by relay
torrcs. The proposal should make it clear why the value this feature
provides is greater than that cost.

* Proposals should be detailed enough to be used as patches for the
spec. That is to say, describing how dir-spec should be amended. In
particular this is missing 'what section are we modifying' and 'what
is the precise format'. Your proposal attempts to answer the later but
the format we're looking for is...


Cheers! -Damian

On Thu, Jul 3, 2014 at 3:13 AM, Virgil Griffith <i at virgil.gr> wrote:
> URL:
> https://dl.dropboxusercontent.com/u/3308162/ExtraRelayDescriptorFields.txt
> Fulltext below.  Comments appreciated.
> -V
> =======================
> Filename: ExtraRelayDescriptorFields.txt
> Title: Adding new X- fields to relay descriptor
> Author: Virgil Griffith, Nick Mathewson
> Created: 2014-06-03
> Status: Open
> 1. Motivation
> We wish to allow developers to build new applications atop relays. Towards
> this
> end, we wish to add the ability for users to specify arbitrary new key-value
> entries under the "X-" namespace.
> 2. Proposal
> Allow optional key-value lines in the relay's torrc file.  These lines will
> be
> mirrored in the relay's descriptor which is then published in the directory
> consensus.
> The format is:
> X-key value
> For example:
> X-bitcoin 19mP9FKrXqL46Si58pHdhGKow88SUPy1V8
> X-gravatar https://s.gravatar.com/avatar/d27fce46c9ac41a41bb52455ae75701d
> X-nameid virgil.gr
> X-favoritequote Be excellent to each other.  Party on dudes!
> The value field must be printable ASCII (characters 32-126).  The value must
> not under any condition contain a newline.  The key may contain lowercase
> ASCII letters (a-z), digits, underscore, or dash.  In regex, [-_0-9a-z].
> There may need to be a maximum sum length of the X- entries.  This is
> left to the developers.  I propose a maximum sum length of 5 kilobytes.
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