[tor-dev] New Fallback Directory File Format

teor teor2345 at gmail.com
Fri Dec 22 14:53:35 UTC 2017

Hi all,

Some time in the next few weeks, the Tor fallback directory mirror file
format will change. This affects stem and Relay Search, which parse this

Change Description

Here is a list of changes to the file format:
* the "weight" line has been removed, and replaced with a Tor config
  default (#24679, #24681)
* the comma that separates fallback C strings is now on its own line
* a "nickname" comment has been added (#24600)
* an optional "extrainfo" comment has been added (#22759)

The added fields will be populated with placeholders until the list is
rebuilt (#22271). This will hopefully happen some time in the next few

Requesting More Extra Info Caches

There are only a few fallbacks that cache extra-info documents.
I checked 67, and only 4 cached extra-info documents.

atagar, do you want me to ask some fallback operators to set
DownloadExtraInfo 1?

What number or proportion would you like?

(We allow approximately 25% of fallbacks to go down before we start to rebuild
the list. In the worst case, this can mean that ~40% are down at some point.)

Example Entries

A sample entry in the new format, using actual relay info:

" orport=9001 id=0756B7CD4DFC8182BE23143FAC0642F515182CEB"
" ipv6=[2a01:4f8:162:51e2::2]:9001"
/* nickname=rueckgrat */
/* extrainfo=1 */

The current fallback file in the new format, with placeholders:

A small sample fallback file in the new format, with actual relay info:

Please let me know if you would like any changes to the format.


Tim Wilson-Brown (teor)

teor2345 at gmail dot com
PGP C855 6CED 5D90 A0C5 29F6 4D43 450C BA7F 968F 094B
xmpp: teor at torproject dot org

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