New Release: Tor 0.4.5.6

by nickm | February 15, 2021

After months of work, we have a new stable release series! If you build Tor from source, you can download the source code for 0.4.5.6 on the download page. Packages should be available within the next several weeks, with a new Tor Browser likely next week.

The Tor 0.4.5.x release series is dedicated to the memory of Karsten Loesing (1979-2020), Tor developer, cypherpunk, husband, and father. Karsten is best known for creating the Tor metrics portal and leading the metrics team, but he was involved in Tor from the early days. For example, while he was still a student he invented and implemented the v2 onion service directory design, and he also served as an ambassador to the many German researchers working in the anonymity field. We loved him and respected him for his patience, his consistency, and his welcoming approach to growing our community.

This release series introduces significant improvements in relay IPv6 address discovery, a new "MetricsPort" mechanism for relay operators to measure performance, LTTng support, build system improvements to help when using Tor as a static library, and significant bugfixes related to Windows relay performance. It also includes numerous smaller features and bugfixes.

Below are the changes since 0.4.4.7. For a list of changes since 0.4.5.5-rc, see the ChangeLog file.

Changes in version 0.4.5.6 - 2021-02-15

  • Major features (build):
    • When building Tor, first link all object files into a single static library. This may help with embedding Tor in other programs. Note that most Tor functions do not constitute a part of a stable or supported API: only those functions in tor_api.h should be used if embedding Tor. Closes ticket 40127.
  • Major features (metrics):
    • Introduce a new MetricsPort which exposes, through an HTTP interface, a series of metrics that tor collects at runtime. At the moment, the only supported output format is Prometheus data model. Closes ticket 40063. See the manual page for more information and security considerations.