ReleaseNotes

  o Minor bugfixes (directory authority, backport from 0.4.1.2-alpha):
    - Move the "bandwidth-file-headers" line in directory authority
      votes so that it conforms to dir-spec.txt. Fixes bug 30316; bugfix
      on 0.3.5.1-alpha.

  o Minor bugfixes (error handling, backport from 0.4.2.1-alpha):
    - On abort, try harder to flush the output buffers of log messages.
      On some platforms (macOS), log messages could be discarded when
      the process terminates. Fixes bug 31571; bugfix on 0.3.5.1-alpha.
    - Report the tor version whenever an assertion fails. Previously, we
      only reported the Tor version on some crashes, and some non-fatal
      assertions. Fixes bug 31571; bugfix on 0.3.5.1-alpha.

  o Minor bugfixes (FreeBSD, PF-based proxy, IPv6, backport from 0.4.2.1-alpha):
    - When extracting an IPv6 address from a PF-based proxy, verify that
      we are actually configured to receive an IPv6 address, and log an
      internal error if not. Fixes part of bug 31687; bugfix
      on 0.2.3.4-alpha.

  o Minor bugfixes (guards, backport from 0.4.2.1-alpha):
    - When tor is missing descriptors for some primary entry guards,
      make the log message less alarming. It's normal for descriptors to
      expire, as long as tor fetches new ones soon after. Fixes bug
      31657; bugfix on 0.3.3.1-alpha.

  o Minor bugfixes (logging, backport from 0.4.1.1-alpha):
    - Do not log a warning when running with an OpenSSL version other
      than the one Tor was compiled with, if the two versions should be
      compatible. Previously, we would warn whenever the version was
      different. Fixes bug 30190; bugfix on 0.2.4.2-alpha.

  o Minor bugfixes (logging, backport from 0.4.2.1-alpha):
    - Change log level of message "Hash of session info was not as
      expected" to LOG_PROTOCOL_WARN. Fixes bug 12399; bugfix
      on 0.1.1.10-alpha.

  o Minor bugfixes (logging, backport from 0.4.2.2-alpha):
    - Rate-limit our the logging message about the obsolete .exit
      notation. Previously, there was no limit on this warning, which
      could potentially be triggered many times by a hostile website.
      Fixes bug 31466; bugfix on 0.2.2.1-alpha.

  o Minor bugfixes (logging, protocol violations, backport from 0.4.2.2-alpha):
    - Do not log a nonfatal assertion failure when receiving a VERSIONS
      cell on a connection using the obsolete v1 link protocol. Log a
      protocol_warn instead. Fixes bug 31107; bugfix on 0.2.4.4-alpha.

  o Minor bugfixes (mainloop, periodic events, in-process API, backport from 0.4.2.3-alpha):
    - Reset the periodic events' "enabled" flag when Tor is shut down
      cleanly. Previously, this flag was left on, which caused periodic
      events not to be re-enabled when Tor was relaunched in-process
      with tor_api.h after a shutdown. Fixes bug 32058; bugfix
      on 0.3.3.1-alpha.

  o Minor bugfixes (memory leak, backport from 0.4.1.1-alpha):
    - Avoid a minor memory leak that could occur on relays when failing
      to create a "keys" directory. Fixes bug 30148; bugfix
      on 0.3.3.1-alpha.

  o Minor bugfixes (memory leak, backport from 0.4.1.4-rc):
    - Fix a trivial memory leak when parsing an invalid value
      from a download schedule in the configuration. Fixes bug
      30894; bugfix on 0.3.4.1-alpha.

  o Minor bugfixes (NetBSD, backport from 0.4.1.2-alpha):
    - Fix usage of minherit() on NetBSD and other platforms that define
      MAP_INHERIT_{ZERO,NONE} instead of INHERIT_{ZERO,NONE}. Fixes bug
      30614; bugfix on 0.4.0.2-alpha. Patch from Taylor Campbell.

  o Minor bugfixes (onion services, backport from 0.4.1.1-alpha):
    - Avoid a GCC 9.1.1 warning (and possible crash depending on libc
      implemenation) when failing to load an onion service client
      authorization file. Fixes bug 30475; bugfix on 0.3.5.1-alpha.

  o Minor bugfixes (out-of-memory handler, backport from 0.4.1.2-alpha):
    - When purging the DNS cache because of an out-of-memory condition,
      try purging just the older entries at first. Previously, we would
      always purge the whole thing. Fixes bug 29617; bugfix
      on 0.3.5.1-alpha.

  o Minor bugfixes (portability, backport from 0.4.1.2-alpha):
    - Avoid crashing in our tor_vasprintf() implementation on systems
      that define neither vasprintf() nor _vscprintf(). (This bug has
      been here long enough that we question whether people are running
      Tor on such systems, but we're applying the fix out of caution.)
      Fixes bug 30561; bugfix on 0.2.8.2-alpha. Found and fixed by
      Tobias Stoeckmann.

  o Minor bugfixes (process management, backport from 0.4.2.3-alpha):
    - Remove overly strict assertions that triggered when a pluggable
      transport failed to launch. Fixes bug 31091; bugfix
      on 0.4.0.1-alpha.
    - Remove an assertion in the Unix process backend. This assertion
      would trigger when we failed to find the executable for a child
      process. Fixes bug 31810; bugfix on 0.4.0.1-alpha.

  o Minor bugfixes (relay, backport from 0.4.2.2-alpha):
    - Avoid crashing when starting with a corrupt keys directory where
      the old ntor key and the new ntor key are identical. Fixes bug
      30916; bugfix on 0.2.4.8-alpha.

  o Minor bugfixes (rust, backport from 0.4.2.1-alpha):
    - Correctly exclude a redundant rust build job in Travis. Fixes bug
      31463; bugfix on 0.3.5.4-alpha.

  o Minor bugfixes (testing, backport from 0.4.2.3-alpha):
    - When testing port rebinding, don't busy-wait for tor to log.
      Instead, actually sleep for a short time before polling again.
      Also improve the formatting of control commands and log messages.
      Fixes bug 31837; bugfix on 0.3.5.1-alpha.

  o Minor bugfixes (tls, logging, backport from 0.4.2.3-alpha):
    - Log bugs about the TLS read buffer's length only once, rather than
      filling the logs with similar warnings. Fixes bug 31939; bugfix
      on 0.3.0.4-rc.

  o Minor bugfixes (v2 single onion services, backport from 0.4.2.1-alpha):
    - Always retry v2 single onion service intro and rend circuits with
      a 3-hop path. Previously, v2 single onion services used a 3-hop
      path when rendezvous circuits were retried after a remote or
      delayed failure, but a 1-hop path for immediate retries. Fixes bug
      23818; bugfix on 0.2.9.3-alpha.
    - Make v3 single onion services fall back to a 3-hop intro, when all
      intro points are unreachable via a 1-hop path. Previously, v3
      single onion services failed when all intro nodes were unreachable
      via a 1-hop path. Fixes bug 23507; bugfix on 0.3.2.1-alpha.

  o Documentation (backport from 0.4.2.1-alpha):
    - Use RFC 2397 data URL scheme to embed an image into tor-exit-
      notice.html so that operators no longer have to host it
      themselves. Closes ticket 31089.

  o Testing (backport from 0.4.1.2-alpha):
    - Specify torrc paths (with empty files) when launching tor in
      integration tests; refrain from reading user and system torrcs.
      Resolves issue 29702.

  o Testing (continuous integration, backport from 0.4.1.1-alpha):
    - In Travis, show stem's tor log after failure. Closes ticket 30234.

  o Testing (continuous integration, backport from 0.4.1.5):
    - In Travis, make stem log a controller trace to the console, and
      tail stem's tor log after failure. Closes ticket 30591.
    - In Travis, only run the stem tests that use a tor binary. Closes
      ticket 30694.

  o Testing (continuous integration, backport from 0.4.2.3-alpha):
    - Disable all but one Travis CI macOS build, to mitigate slow
      scheduling of Travis macOS jobs. Closes ticket 32177.
    - Run the chutney IPv6 networks as part of Travis CI. Closes
      ticket 30860.
    - Simplify the Travis CI build matrix, and optimise for build time.
      Closes ticket 31859.
    - Use Windows Server 2019 instead of Windows Server 2016 in our
      Appveyor builds. Closes ticket 32086.

  o Testing (continuous integration, backport from 0.4.2.4-rc):
    - Use Ubuntu Bionic images for our Travis CI builds, so we can get a
      recent version of coccinelle. But leave chutney on Ubuntu Trusty,
      until we can fix some Bionic permissions issues (see ticket
      32240). Related to ticket 31919.
    - Install the mingw OpenSSL package in Appveyor. This makes sure
      that the OpenSSL headers and libraries match in Tor's Appveyor
      builds. (This bug was triggered by an Appveyor image update.)
      Fixes bug 32449; bugfix on 0.3.5.6-rc.
    - In Travis, use Xcode 11.2 on macOS 10.14. Closes ticket 32241.

  o Testing (continuous integration, backport from 0.4.2.5):
    - Require C99 standards-conforming code in Travis CI, but allow GNU gcc
      extensions. Also activates clang's -Wtypedef-redefinition warnings.
      Build some jobs with -std=gnu99, and some jobs without.
      Closes ticket 32500.


Changes in version 0.3.5.9 - 2019-12-09
  Tor 0.3.5.9 backports serveral fixes from later releases, including
  several that affect bridge users, relay stability, onion services,
  and much more.

  o Directory authority changes (backport from 0.4.1.5):
    - The directory authority "dizum" has a new IP address. Closes
      ticket 31406.

  o Major bugfixes (bridges, backport from 0.4.1.2-alpha):
    - Consider our directory information to have changed when our list
      of bridges changes. Previously, Tor would not re-compute the
      status of its directory information when bridges changed, and
      therefore would not realize that it was no longer able to build
      circuits. Fixes part of bug 29875.
    - Do not count previously configured working bridges towards our
      total of working bridges. Previously, when Tor's list of bridges
      changed, it would think that the old bridges were still usable,
      and delay fetching router descriptors for the new ones. Fixes part
      of bug 29875; bugfix on 0.3.0.1-alpha.

  o Major bugfixes (circuit build, guard, backport from 0.4.1.4-rc):
    - When considering upgrading circuits from "waiting for guard" to
      "open", always ignore circuits that are marked for close. Otherwise,
      we can end up in the situation where a subsystem is notified that
      a closing circuit has just opened, leading to undesirable
      behavior. Fixes bug 30871; bugfix on 0.3.0.1-alpha.

  o Major bugfixes (NSS, relay, backport from 0.4.0.4-rc):
    - When running with NSS, disable TLS 1.2 ciphersuites that use
      SHA384 for their PRF. Due to an NSS bug, the TLS key exporters for
      these ciphersuites don't work -- which caused relays to fail to
      handshake with one another when these ciphersuites were enabled.
      Fixes bug 29241; bugfix on 0.3.5.1-alpha.

  o Major bugfixes (Onion service reachability, backport from 0.4.1.3-alpha):
    - Properly clean up the introduction point map when circuits change
      purpose from onion service circuits to pathbias, measurement, or
      other circuit types. This should fix some service-side instances
      of introduction point failure. Fixes bug 29034; bugfix
      on 0.3.2.1-alpha.

  o Major bugfixes (onion service v3, backport from 0.4.1.1-alpha):
    - Fix an unreachable bug in which an introduction point could try to
      send an INTRODUCE_ACK with a status code that Trunnel would refuse
      to encode, leading the relay to assert(). We've consolidated the
      ABI values into Trunnel now. Fixes bug 30454; bugfix
      on 0.3.0.1-alpha.
    - Clients can now handle unknown status codes from INTRODUCE_ACK
      cells. (The NACK behavior will stay the same.) This will allow us
      to extend status codes in the future without breaking the normal
      client behavior. Fixes another part of bug 30454; bugfix
      on 0.3.0.1-alpha.

  o Major bugfixes (torrc parsing, backport from 0.4.2.2-alpha):
    - Stop ignoring torrc options after an %include directive, when the
      included directory ends with a file that does not contain any
      config options (but does contain comments or whitespace). Fixes
      bug 31408; bugfix on 0.3.1.1-alpha.

  o Major bugfixes (v3 onion services, backport from 0.4.2.3-alpha):
    - Onion services now always use the exact number of intro points
      configured with the HiddenServiceNumIntroductionPoints option (or
      fewer if nodes are excluded). Before, a service could sometimes
      pick more intro points than configured. Fixes bug 31548; bugfix
      on 0.3.2.1-alpha.

  o Minor features (address selection, backport from 0.4.0.3-alpha):
    - Treat the subnet 100.64.0.0/10 as public for some purposes;
      private for others. This subnet is the RFC 6598 (Carrier Grade
      NAT) IP range, and is deployed by many ISPs as an alternative to
      RFC 1918 that does not break existing internal networks. Tor now
      blocks SOCKS and control ports on these addresses and warns users
      if client ports or ExtORPorts are listening on a RFC 6598 address.
      Closes ticket 28525. Patch by Neel Chauhan.

  o Minor features (bandwidth authority, backport from 0.4.0.4-rc):
    - Make bandwidth authorities ignore relays that are reported in the
      bandwidth file with the flag "vote=0". This change allows us to
      report unmeasured relays for diagnostic reasons without including
      their bandwidth in the bandwidth authorities' vote. Closes
      ticket 29806.

  o Minor features (compile-time modules, backport from version 0.4.1.1-alpha):
    - Add a "--list-modules" command to print a list of which compile-
      time modules are enabled. Closes ticket 30452.

  o Minor features (continuous integration, backport from 0.4.0.4-rc):
    - On Travis Rust builds, cleanup Rust registry and refrain from
      caching the "target/" directory to speed up builds. Resolves
      issue 29962.

  o Minor features (continuous integration, backport from 0.4.0.5):
    - In Travis, tell timelimit to use stem's backtrace signals, and
      launch python directly from timelimit, so python receives the
      signals from timelimit, rather than make. Closes ticket 30117.

  o Minor features (continuous integration, backport from 0.4.1.1-alpha):
    - Remove sudo configuration lines from .travis.yml as they are no
      longer needed with current Travis build environment. Resolves
      issue 30213.

  o Minor features (continuous integration, backport from 0.4.1.4-rc):
    - Our Travis configuration now uses Chutney to run some network
      integration tests automatically. Closes ticket 29280.

  o Minor features (continuous integration, backport from 0.4.2.2-alpha):
    - When building on Appveyor and Travis, pass the "-k" flag to make,
      so that we are informed of all compilation failures, not just the
      first one or two. Closes ticket 31372.

  o Minor features (fallback directory list, backport from 0.4.1.4-rc):
    - Replace the 157 fallbacks originally introduced in Tor 0.3.5.6-rc
      in December 2018 (of which ~122 were still functional), with a
      list of 148 fallbacks (70 new, 78 existing, 79 removed) generated
      in June 2019. Closes ticket 28795.

  o Minor features (geoip, backport from 0.4.2.5):
    - Update geoip and geoip6 to the December 3 2019 Maxmind GeoLite2
      Country database. Closes ticket 32685.

  o Minor features (NSS, diagnostic, backport from 0.4.0.4-rc):
    - Try to log an error from NSS (if there is any) and a more useful
      description of our situation if we are using NSS and a call to
      SSL_ExportKeyingMaterial() fails. Diagnostic for ticket 29241.

  o Minor features (stem tests, backport from 0.4.2.1-alpha):
    - Change "make test-stem" so it only runs the stem tests that use
      tor. This change makes test-stem faster and more reliable. Closes
      ticket 31554.

  o Minor bugfixes (security, backport from 0.4.0.4-rc):
    - Verify in more places that we are not about to create a buffer
      with more than INT_MAX bytes, to avoid possible OOB access in the
      event of bugs. Fixes bug 30041; bugfix on 0.2.0.16. Found and
      fixed by Tobias Stoeckmann.
    - Fix a potential double free bug when reading huge bandwidth files.
      The issue is not exploitable in the current Tor network because
      the vulnerable code is only reached when directory authorities
      read bandwidth files, but bandwidth files come from a trusted
      source (usually the authorities themselves). Furthermore, the
      issue is only exploitable in rare (non-POSIX) 32-bit architectures,
      which are not used by any of the current authorities. Fixes bug
      30040; bugfix on 0.3.5.1-alpha. Bug found and fixed by
      Tobias Stoeckmann.

  o Minor bugfix (continuous integration, backport from 0.4.0.4-rc):
    - Reset coverage state on disk after Travis CI has finished. This
      should prevent future coverage merge errors from causing the test
      suite for the "process" subsystem to fail. The process subsystem
      was introduced in 0.4.0.1-alpha. Fixes bug 29036; bugfix
      on 0.2.9.15.
    - Terminate test-stem if it takes more than 9.5 minutes to run.
      (Travis terminates the job after 10 minutes of no output.)
      Diagnostic for 29437. Fixes bug 30011; bugfix on 0.3.5.4-alpha.

  o Minor bugfixes (Appveyor CI, backport from 0.4.2.2-alpha):
    - Avoid spurious errors when Appveyor CI fails before the install step.
      Fixes bug 31884; bugfix on 0.3.4.2-alpha.

  o Minor bugfixes (build system, backport form 0.4.2.1-alpha):
    - Do not include the deprecated <sys/sysctl.h> on Linux or Windows
      systems. Fixes bug 31673; bugfix on 0.2.5.4-alpha.

  o Minor bugfixes (C correctness, backport from 0.4.0.4-rc):
    - Fix an unlikely memory leak in consensus_diff_apply(). Fixes bug
      29824; bugfix on 0.3.1.1-alpha. This is Coverity warning
      CID 1444119.

  o Minor bugfixes (circuit isolation, backport from 0.4.1.3-alpha):
    - Fix a logic error that prevented the SessionGroup sub-option from
      being accepted. Fixes bug 22619; bugfix on 0.2.7.2-alpha.

  o Minor bugfixes (client, onion service v3, backport from 0.4.2.4-rc):
    - Fix a BUG() assertion that occurs within a very small race window
      between when a client intro circuit opens and when its descriptor
      gets cleaned up from the cache. The circuit is now closed early,
      which will trigger a re-fetch of the descriptor and continue the
      connection. Fixes bug 28970; bugfix on 0.3.2.1-alpha.

  o Minor bugfixes (clock skew detection, backport from 0.4.1.5):
    - Don't believe clock skew results from NETINFO cells that appear to
      arrive before we sent the VERSIONS cells they are responding to.
      Previously, we would accept them up to 3 minutes "in the past".
      Fixes bug 31343; bugfix on 0.2.4.4-alpha.

  o Minor bugfixes (compilation warning, backport from 0.4.1.5):
    - Fix a compilation warning on Windows about casting a function
      pointer for GetTickCount64(). Fixes bug 31374; bugfix
      on 0.2.9.1-alpha.

  o Minor bugfixes (compilation, backport from 0.4.0.2-alpha):
    - Silence a compiler warning in test-memwipe.c on OpenBSD. Fixes bug
      29145; bugfix on 0.2.9.3-alpha. Patch from Kris Katterjohn.

  o Minor bugfixes (compilation, backport from 0.4.1.5):
    - Avoid using labs() on time_t, which can cause compilation warnings
      on 64-bit Windows builds. Fixes bug 31343; bugfix on 0.2.4.4-alpha.

  o Minor bugfixes (compilation, backport from 0.4.2.1-alpha):
    - Suppress spurious float-conversion warnings from GCC when calling
      floating-point classifier functions on FreeBSD. Fixes part of bug
      31687; bugfix on 0.3.1.5-alpha.

  o Minor bugfixes (compilation, unusual configurations, backport from 0.4.1.1-alpha):
    - Avoid failures when building with the ALL_BUGS_ARE_FATAL option
      due to missing declarations of abort(), and prevent other such
      failures in the future. Fixes bug 30189; bugfix on 0.3.4.1-alpha.

  o Minor bugfixes (configuration, proxies, backport from 0.4.1.2-alpha):
    - Fix a bug that prevented us from supporting SOCKS5 proxies that
      want authentication along with configured (but unused!)
      ClientTransportPlugins. Fixes bug 29670; bugfix on 0.2.6.1-alpha.

  o Minor bugfixes (connections, backport from 0.4.2.3-rc):
    - Avoid trying to read data from closed connections, which can cause
      needless loops in Libevent and infinite loops in Shadow. Fixes bug
      30344; bugfix on 0.1.1.1-alpha.

  o Minor bugfixes (continuous integration, backport from 0.4.1.3-alpha):
    - Allow the test-stem job to fail in Travis, because it sometimes
      hangs. Fixes bug 30744; bugfix on 0.3.5.4-alpha.
    - Skip test_rebind on macOS in Travis, because it is unreliable on
      macOS on Travis. Fixes bug 30713; bugfix on 0.3.5.1-alpha.
    - Skip test_rebind when the TOR_SKIP_TEST_REBIND environment
      variable is set. Fixes bug 30713; bugfix on 0.3.5.1-alpha.

  o Minor bugfixes (crash on exit, backport from 0.4.1.4-rc):
    - Avoid a set of possible code paths that could try to use freed
      memory in routerlist_free() while Tor was exiting. Fixes bug
      31003; bugfix on 0.1.2.2-alpha.

  o Minor bugfixes (directory authorities, backport from 0.4.1.3-alpha):
    - Stop crashing after parsing an unknown descriptor purpose
      annotation. We think this bug can only be triggered by modifying a
      local file. Fixes bug 30781; bugfix on 0.2.0.8-alpha.

  o Minor bugfixes (directory authority, backport from 0.4.1.2-alpha):
    - Move the "bandwidth-file-headers" line in directory authority
      votes so that it conforms to dir-spec.txt. Fixes bug 30316; bugfix
      on 0.3.5.1-alpha.

  o Minor bugfixes (error handling, backport from 0.4.2.1-alpha):
    - On abort, try harder to flush the output buffers of log messages.
      On some platforms (macOS), log messages could be discarded when
      the process terminates. Fixes bug 31571; bugfix on 0.3.5.1-alpha.
    - Report the tor version whenever an assertion fails. Previously, we
      only reported the Tor version on some crashes, and some non-fatal
      assertions. Fixes bug 31571; bugfix on 0.3.5.1-alpha.

  o Minor bugfixes (FreeBSD, PF-based proxy, IPv6, backport from 0.4.2.1-alpha):
    - When extracting an IPv6 address from a PF-based proxy, verify that
      we are actually configured to receive an IPv6 address, and log an
      internal error if not. Fixes part of bug 31687; bugfix
      on 0.2.3.4-alpha.

  o Minor bugfixes (guards, backport from 0.4.2.1-alpha):
    - When tor is missing descriptors for some primary entry guards,
      make the log message less alarming. It's normal for descriptors to
      expire, as long as tor fetches new ones soon after. Fixes bug
      31657; bugfix on 0.3.3.1-alpha.

  o Minor bugfixes (logging, backport from 0.4.0.2-alpha):
    - Avoid logging that we are relaxing a circuit timeout when that
      timeout is fixed. Fixes bug 28698; bugfix on 0.2.4.7-alpha.

  o Minor bugfixes (logging, backport from 0.4.0.3-alpha):
    - Correct a misleading error message when IPv4Only or IPv6Only is
      used but the resolved address can not be interpreted as an address
      of the specified IP version. Fixes bug 13221; bugfix on
      0.2.3.9-alpha. Patch from Kris Katterjohn.
    - Log the correct port number for listening sockets when "auto" is
      used to let Tor pick the port number. Previously, port 0 was
      logged instead of the actual port number. Fixes bug 29144; bugfix
      on 0.3.5.1-alpha. Patch from Kris Katterjohn.
    - Stop logging a BUG() warning when Tor is waiting for exit
      descriptors. Fixes bug 28656; bugfix on 0.3.5.1-alpha.

  o Minor bugfixes (logging, backport from 0.4.1.1-alpha):
    - Do not log a warning when running with an OpenSSL version other
      than the one Tor was compiled with, if the two versions should be
      compatible. Previously, we would warn whenever the version was
      different. Fixes bug 30190; bugfix on 0.2.4.2-alpha.

  o Minor bugfixes (logging, backport from 0.4.2.1-alpha):
    - Change log level of message "Hash of session info was not as
      expected" to LOG_PROTOCOL_WARN. Fixes bug 12399; bugfix
      on 0.1.1.10-alpha.

  o Minor bugfixes (logging, backport from 0.4.2.2-alpha):
    - Rate-limit our the logging message about the obsolete .exit
      notation. Previously, there was no limit on this warning, which
      could potentially be triggered many times by a hostile website.
      Fixes bug 31466; bugfix on 0.2.2.1-alpha.

  o Minor bugfixes (logging, protocol violations, backport from 0.4.2.2-alpha):
    - Do not log a nonfatal assertion failure when receiving a VERSIONS
      cell on a connection using the obsolete v1 link protocol. Log a
      protocol_warn instead. Fixes bug 31107; bugfix on 0.2.4.4-alpha.

  o Minor bugfixes (mainloop, periodic events, in-process API, backport from 0.4.2.3-alpha):
    - Reset the periodic events' "enabled" flag when Tor is shut down
      cleanly. Previously, this flag was left on, which caused periodic
      events not to be re-enabled when Tor was relaunched in-process
      with tor_api.h after a shutdown. Fixes bug 32058; bugfix
      on 0.3.3.1-alpha.

  o Minor bugfixes (memory leak, backport from 0.4.1.1-alpha):
    - Avoid a minor memory leak that could occur on relays when failing
      to create a "keys" directory. Fixes bug 30148; bugfix
      on 0.3.3.1-alpha.

  o Minor bugfixes (memory leak, backport from 0.4.1.4-rc):
    - Fix a trivial memory leak when parsing an invalid value
      from a download schedule in the configuration. Fixes bug
      30894; bugfix on 0.3.4.1-alpha.

  o Minor bugfixes (memory management, backport from 0.4.0.3-alpha):
    - Refactor the shared random state's memory management so that it
      actually takes ownership of the shared random value pointers.
      Fixes bug 29706; bugfix on 0.2.9.1-alpha.

  o Minor bugfixes (memory management, testing, backport from 0.4.0.3-alpha):
    - Stop leaking parts of the shared random state in the shared-random
      unit tests. Fixes bug 29599; bugfix on 0.2.9.1-alpha.

  o Minor bugfixes (onion services, backport from 0.4.1.1-alpha):
    - Avoid a GCC 9.1.1 warning (and possible crash depending on libc
      implemenation) when failing to load an onion service client
      authorization file. Fixes bug 30475; bugfix on 0.3.5.1-alpha.

  o Minor bugfixes (out-of-memory handler, backport from 0.4.1.2-alpha):
    - When purging the DNS cache because of an out-of-memory condition,
      try purging just the older entries at first. Previously, we would
      always purge the whole thing. Fixes bug 29617; bugfix
      on 0.3.5.1-alpha.

  o Minor bugfixes (portability, backport from 0.4.1.2-alpha):
    - Avoid crashing in our tor_vasprintf() implementation on systems
      that define neither vasprintf() nor _vscprintf(). (This bug has
      been here long enough that we question whether people are running
      Tor on such systems, but we're applying the fix out of caution.)
      Fixes bug 30561; bugfix on 0.2.8.2-alpha. Found and fixed by
      Tobias Stoeckmann.

  o Minor bugfixes (relay, backport from 0.4.2.2-alpha):
    - Avoid crashing when starting with a corrupt keys directory where
      the old ntor key and the new ntor key are identical. Fixes bug
      30916; bugfix on 0.2.4.8-alpha.

  o Minor bugfixes (rust, backport from 0.4.0.5):
    - Abort on panic in all build profiles, instead of potentially
      unwinding into C code. Fixes bug 27199; bugfix on 0.3.3.1-alpha.

  o Minor bugfixes (rust, backport from 0.4.2.1-alpha):
    - Correctly exclude a redundant rust build job in Travis. Fixes bug
      31463; bugfix on 0.3.5.4-alpha.

  o Minor bugfixes (single onion services, backport from 0.4.0.3-alpha):
    - Allow connections to single onion services to remain idle without
      being disconnected. Previously, relays acting as rendezvous points
      for single onion services were mistakenly closing idle rendezvous
      circuits after 60 seconds, thinking that they were unused
      directory-fetching circuits that had served their purpose. Fixes
      bug 29665; bugfix on 0.2.1.26.

  o Minor bugfixes (stats, backport from 0.4.0.3-alpha):
    - When ExtraInfoStatistics is 0, stop including PaddingStatistics in
      relay and bridge extra-info documents. Fixes bug 29017; bugfix
      on 0.3.1.1-alpha.

  o Minor bugfixes (testing, backport from 0.4.0.3-alpha):
    - Downgrade some LOG_ERR messages in the address/* tests to
      warnings. The LOG_ERR messages were occurring when we had no
      configured network. We were failing the unit tests, because we
      backported 28668 to 0.3.5.8, but did not backport 29530. Fixes bug
      29530; bugfix on 0.3.5.8.
    - Fix our gcov wrapper script to look for object files at the
      correct locations. Fixes bug 29435; bugfix on 0.3.5.1-alpha.

  o Minor bugfixes (testing, backport from 0.4.0.4-rc):
    - Backport the 0.3.4 src/test/test-network.sh to 0.2.9. We need a
      recent test-network.sh to use new chutney features in CI. Fixes
      bug 29703; bugfix on 0.2.9.1-alpha.
    - Fix a test failure on Windows caused by an unexpected "BUG"
      warning in our tests for tor_gmtime_r(-1). Fixes bug 29922; bugfix
      on 0.2.9.3-alpha.

  o Minor bugfixes (testing, backport from 0.4.2.3-alpha):
    - When testing port rebinding, don't busy-wait for tor to log.
      Instead, actually sleep for a short time before polling again.
      Also improve the formatting of control commands and log messages.
      Fixes bug 31837; bugfix on 0.3.5.1-alpha.

  o Minor bugfixes (TLS protocol, backport form 0.4.0.4-rc):
    - When classifying a client's selection of TLS ciphers, if the
      client ciphers are not yet available, do not cache the result.
      Previously, we had cached the unavailability of the cipher list
      and never looked again, which in turn led us to assume that the
      client only supported the ancient V1 link protocol. This, in turn,
      was causing Stem integration tests to stall in some cases. Fixes
      bug 30021; bugfix on 0.2.4.8-alpha.

  o Minor bugfixes (tls, logging, backport from 0.4.2.3-alpha):
    - Log bugs about the TLS read buffer's length only once, rather than
      filling the logs with similar warnings. Fixes bug 31939; bugfix
      on 0.3.0.4-rc.

  o Minor bugfixes (v2 single onion services, backport from 0.4.2.1-alpha):
    - Always retry v2 single onion service intro and rend circuits with
      a 3-hop path. Previously, v2 single onion services used a 3-hop
      path when rendezvous circuits were retried after a remote or
      delayed failure, but a 1-hop path for immediate retries. Fixes bug
      23818; bugfix on 0.2.9.3-alpha.
    - Make v3 single onion services fall back to a 3-hop intro, when all
      intro points are unreachable via a 1-hop path. Previously, v3
      single onion services failed when all intro nodes were unreachable
      via a 1-hop path. Fixes bug 23507; bugfix on 0.3.2.1-alpha.

  o Minor bugfixes (Windows, CI, backport from 0.4.0.3-alpha):
    - Skip the Appveyor 32-bit Windows Server 2016 job, and 64-bit
      Windows Server 2012 R2 job. The remaining 2 jobs still provide
      coverage of 64/32-bit, and Windows Server 2016/2012 R2. Also set
      fast_finish, so failed jobs terminate the build immediately. Fixes
      bug 29601; bugfix on 0.3.5.4-alpha.

  o Documentation (backport from 0.4.2.1-alpha):
    - Use RFC 2397 data URL scheme to embed an image into tor-exit-
      notice.html so that operators no longer have to host it
      themselves. Closes ticket 31089.

  o Testing (backport from 0.4.1.2-alpha):
    - Specify torrc paths (with empty files) when launching tor in
      integration tests; refrain from reading user and system torrcs.
      Resolves issue 29702.

  o Testing (continuous integration, backport from 0.4.1.1-alpha):
    - In Travis, show stem's tor log after failure. Closes ticket 30234.

  o Testing (continuous integration, backport from 0.4.1.5):
    - In Travis, make stem log a controller trace to the console, and
      tail stem's tor log after failure. Closes ticket 30591.
    - In Travis, only run the stem tests that use a tor binary. Closes
      ticket 30694.

  o Testing (continuous integration, backport from 0.4.2.3-alpha):
    - Disable all but one Travis CI macOS build, to mitigate slow
      scheduling of Travis macOS jobs. Closes ticket 32177.
    - Run the chutney IPv6 networks as part of Travis CI. Closes
      ticket 30860.
    - Simplify the Travis CI build matrix, and optimise for build time.
      Closes ticket 31859.
    - Use Windows Server 2019 instead of Windows Server 2016 in our
      Appveyor builds. Closes ticket 32086.

  o Testing (continuous integration, backport from 0.4.2.4-rc):
    - Use Ubuntu Bionic images for our Travis CI builds, so we can get a
      recent version of coccinelle. But leave chutney on Ubuntu Trusty,
      until we can fix some Bionic permissions issues (see ticket
      32240). Related to ticket 31919.
    - Install the mingw OpenSSL package in Appveyor. This makes sure
      that the OpenSSL headers and libraries match in Tor's Appveyor
      builds. (This bug was triggered by an Appveyor image update.)
      Fixes bug 32449; bugfix on 0.3.5.6-rc.
    - In Travis, use Xcode 11.2 on macOS 10.14. Closes ticket 32241.

  o Testing (continuous integration, backport from 0.4.2.5):
    - Require C99 standards-conforming code in Travis CI, but allow GNU gcc
      extensions. Also activates clang's -Wtypedef-redefinition warnings.
      Build some jobs with -std=gnu99, and some jobs without.
      Closes ticket 32500.


Changes in version 0.4.1.6 - 2019-09-19
  This release backports several bugfixes to improve stability and
  correctness.  Anyone experiencing build problems or crashes with 0.4.1.5,
  or experiencing reliability issues with single onion services, should
  upgrade.

  o Major bugfixes (crash, Linux, Android, backport from 0.4.2.1-alpha):
    - Tolerate systems (including some Android installations) where
      madvise and MADV_DONTDUMP are available at build-time, but not at
      run time. Previously, these systems would notice a failed syscall
      and abort. Fixes bug 31570; bugfix on 0.4.1.1-alpha.
    - Tolerate systems (including some Linux installations) where
      madvise and/or MADV_DONTFORK are available at build-time, but not
      at run time. Previously, these systems would notice a failed
      syscall and abort. Fixes bug 31696; bugfix on 0.4.1.1-alpha.

  o Minor features (stem tests, backport from 0.4.2.1-alpha):
    - Change "make test-stem" so it only runs the stem tests that use
      tor. This change makes test-stem faster and more reliable. Closes
      ticket 31554.

  o Minor bugfixes (build system, backport form 0.4.2.1-alpha):
    - Do not include the deprecated <sys/sysctl.h> on Linux or Windows
      systems. Fixes bug 31673; bugfix on 0.2.5.4-alpha.

  o Minor bugfixes (compilation, backport from 0.4.2.1-alpha):
    - Add more stub functions to fix compilation on Android with link-
      time optimization when --disable-module-dirauth is used.
      Previously, these compilation settings would make the compiler
      look for functions that didn't exist. Fixes bug 31552; bugfix
      on 0.4.1.1-alpha.
    - Suppress spurious float-conversion warnings from GCC when calling
      floating-point classifier functions on FreeBSD. Fixes part of bug
      31687; bugfix on 0.3.1.5-alpha.

  o Minor bugfixes (controller protocol):
    - Fix the MAPADDRESS controller command to accept one or more
      arguments. Previously, it required two or more arguments, and ignored
      the first. Fixes bug 31772; bugfix on 0.4.1.1-alpha.

  o Minor bugfixes (FreeBSD, PF-based proxy, IPv6, backport from 0.4.2.1-alpha):
    - When extracting an IPv6 address from a PF-based proxy, verify that
      we are actually configured to receive an IPv6 address, and log an
      internal error if not. Fixes part of bug 31687; bugfix
      on 0.2.3.4-alpha.

  o Minor bugfixes (guards, backport from 0.4.2.1-alpha):
    - When tor is missing descriptors for some primary entry guards,
      make the log message less alarming. It's normal for descriptors to
      expire, as long as tor fetches new ones soon after. Fixes bug
      31657; bugfix on 0.3.3.1-alpha.

  o Minor bugfixes (logging, backport from 0.4.2.1-alpha):
    - Change log level of message "Hash of session info was not as
      expected" to LOG_PROTOCOL_WARN. Fixes bug 12399; bugfix
      on 0.1.1.10-alpha.

  o Minor bugfixes (rust, backport from 0.4.2.1-alpha):
    - Correctly exclude a redundant rust build job in Travis. Fixes bug
      31463; bugfix on 0.3.5.4-alpha.

  o Minor bugfixes (v2 single onion services, backport from 0.4.2.1-alpha):
    - Always retry v2 single onion service intro and rend circuits with
      a 3-hop path. Previously, v2 single onion services used a 3-hop
      path when rendezvous circuits were retried after a remote or
      delayed failure, but a 1-hop path for immediate retries. Fixes bug
      23818; bugfix on 0.2.9.3-alpha.

  o Minor bugfixes (v3 single onion services, backport from 0.4.2.1-alpha):
    - Always retry v3 single onion service intro and rend circuits with
      a 3-hop path. Previously, v3 single onion services used a 3-hop
      path when rend circuits were retried after a remote or delayed
      failure, but a 1-hop path for immediate retries. Fixes bug 23818;
      bugfix on 0.3.2.1-alpha.
    - Make v3 single onion services fall back to a 3-hop intro, when all
      intro points are unreachable via a 1-hop path. Previously, v3
      single onion services failed when all intro nodes were unreachable
      via a 1-hop path. Fixes bug 23507; bugfix on 0.3.2.1-alpha.

  o Documentation (backport from 0.4.2.1-alpha):
    - Use RFC 2397 data URL scheme to embed an image into tor-exit-
      notice.html so that operators no longer have to host it
      themselves. Closes ticket 31089.


Changes in version 0.4.1.5 - 2019-08-20
  This is the first stable release in the 0.4.1.x series. This series
  adds experimental circuit-level padding, authenticated SENDME cells to
  defend against certain attacks, and several performance improvements
  to save on CPU consumption. It fixes bugs in bootstrapping and v3
  onion services. It also includes numerous smaller features and
  bugfixes on earlier versions.

  Per our support policy, we will support the 0.4.1.x series for nine
  months, or until three months after the release of a stable 0.4.2.x:
  whichever is longer. If you need longer-term support, please stick
  with 0.3.5.x, which will we plan to support until Feb 2022.

  Below are the changes since 0.4.0.5. For a list of only the changes
  since 0.4.1.4-rc, see the ChangeLog file.

  o Directory authority changes:
    - The directory authority "dizum" has a new IP address. Closes
      ticket 31406.

  o Major features (circuit padding):
    - Onion service clients now add padding cells at the start of their
      INTRODUCE and RENDEZVOUS circuits, to make those circuits' traffic
      look more like general purpose Exit traffic. The overhead for this
      is 2 extra cells in each direction for RENDEZVOUS circuits, and 1
      extra upstream cell and 10 downstream cells for INTRODUCE
      circuits. This feature is only enabled when also supported by the
      circuit's middle node. (Clients may specify fixed middle nodes
      with the MiddleNodes option, and may force-disable this feature
      with the CircuitPadding option.) Closes ticket 28634.

  o Major features (code organization):
    - Tor now includes a generic publish-subscribe message-passing
      subsystem that we can use to organize intermodule dependencies. We
      hope to use this to reduce dependencies between modules that don't
      need to be related, and to generally simplify our codebase. Closes
      ticket 28226.

  o Major features (controller protocol):
    - Controller commands are now parsed using a generalized parsing
      subsystem. Previously, each controller command was responsible for
      parsing its own input, which led to strange inconsistencies.
      Closes ticket 30091.

  o Major features (flow control):
    - Implement authenticated SENDMEs as detailed in proposal 289. A
      SENDME cell now includes the digest of the traffic that it
      acknowledges, so that once an end point receives the SENDME, it
      can confirm the other side's knowledge of the previous cells that
      were sent, and prevent certain types of denial-of-service attacks.
      This behavior is controlled by two new consensus parameters: see
      the proposal for more details. Fixes ticket 26288.

  o Major features (performance):
    - Our node selection algorithm now excludes nodes in linear time.
      Previously, the algorithm was quadratic, which could slow down
      heavily used onion services. Closes ticket 30307.

  o Major features (performance, RNG):
    - Tor now constructs a fast secure pseudorandom number generator for
      each thread, to use when performance is critical. This PRNG is
      based on AES-CTR, using a buffering construction similar to
      libottery and the (newer) OpenBSD arc4random() code. It
      outperforms OpenSSL 1.1.1a's CSPRNG by roughly a factor of 100 for
      small outputs. Although we believe it to be cryptographically
      strong, we are only using it when necessary for performance.
      Implements tickets 29023 and 29536.

  o Major bugfixes (bridges):
    - Consider our directory information to have changed when our list
      of bridges changes. Previously, Tor would not re-compute the
      status of its directory information when bridges changed, and
      therefore would not realize that it was no longer able to build
      circuits. Fixes part of bug 29875.
    - Do not count previously configured working bridges towards our
      total of working bridges. Previously, when Tor's list of bridges
      changed, it would think that the old bridges were still usable,
      and delay fetching router descriptors for the new ones. Fixes part
      of bug 29875; bugfix on 0.3.0.1-alpha.

  o Major bugfixes (circuit build, guard):
    - On relays, properly check that a padding machine is absent before
      logging a warning about it being absent. Fixes bug 30649; bugfix
      on 0.4.0.1-alpha.
    - When considering upgrading circuits from "waiting for guard" to
      "open", always ignore circuits that are marked for close. Otherwise,
      we can end up in the situation where a subsystem is notified that
      a closing circuit has just opened, leading to undesirable
      behavior. Fixes bug 30871; bugfix on 0.3.0.1-alpha.

  o Major bugfixes (onion service reachability):
    - Properly clean up the introduction point map when circuits change
      purpose from onion service circuits to pathbias, measurement, or
      other circuit types. This should fix some service-side instances
      of introduction point failure. Fixes bug 29034; bugfix
      on 0.3.2.1-alpha.

  o Major bugfixes (onion service v3):
    - Fix an unreachable bug in which an introduction point could try to
      send an INTRODUCE_ACK with a status code that Trunnel would refuse
      to encode, leading the relay to assert(). We've consolidated the
      ABI values into Trunnel now. Fixes bug 30454; bugfix
      on 0.3.0.1-alpha.
    - Clients can now handle unknown status codes from INTRODUCE_ACK
      cells. (The NACK behavior will stay the same.) This will allow us
      to extend status codes in the future without breaking the normal
      client behavior. Fixes another part of bug 30454; bugfix
      on 0.3.0.1-alpha.

  o Minor features (authenticated SENDME):
    - Ensure that there is enough randomness on every circuit to prevent
      an attacker from successfully predicting the hashes they will need
      to include in authenticated SENDME cells. At a random interval, if
      we have not sent randomness already, we now leave some extra space
      at the end of a cell that we can fill with random bytes. Closes
      ticket 26846.

  o Minor features (circuit padding logging):
    - Demote noisy client-side warn logs about circuit padding to protocol
      warnings. Add additional log messages and circuit ID fields to help
      with bug 30992 and any other future issues.

  o Minor features (circuit padding):
    - We now use a fast PRNG when scheduling circuit padding. Part of
      ticket 28636.
    - Allow the padding machine designer to pick the edges of their
      histogram instead of trying to compute them automatically using an
      exponential formula. Resolves some undefined behavior in the case
      of small histograms and allows greater flexibility on machine
      design. Closes ticket 29298; bugfix on 0.4.0.1-alpha.
    - Allow circuit padding machines to hold a circuit open until they
      are done padding it. Closes ticket 28780.

  o Minor features (compile-time modules):
    - Add a "--list-modules" command to print a list of which compile-
      time modules are enabled. Closes ticket 30452.

  o Minor features (continuous integration):
    - Our Travis configuration now uses Chutney to run some network
      integration tests automatically. Closes ticket 29280.
    - When running coverage builds on Travis, we now set
      TOR_TEST_RNG_SEED, to avoid RNG-based coverage differences. Part
      of ticket 28878.
    - Remove sudo configuration lines from .travis.yml as they are no
      longer needed with current Travis build environment. Resolves
      issue 30213.
    - In Travis, show stem's tor log after failure. Closes ticket 30234.

  o Minor features (controller):
    - Add onion service version 3 support to the HSFETCH command.
      Previously, only version 2 onion services were supported. Closes
      ticket 25417. Patch by Neel Chauhan.

  o Minor features (debugging):
    - Introduce tor_assertf() and tor_assertf_nonfatal() to enable
      logging of additional information during assert failure. Now we
      can use format strings to include information for trouble
      shooting. Resolves ticket 29662.

  o Minor features (defense in depth):
    - In smartlist_remove_keeporder(), set unused pointers to NULL, in
      case a bug causes them to be used later. Closes ticket 30176.
      Patch from Tobias Stoeckmann.
    - Tor now uses a cryptographically strong PRNG even for decisions
      that we do not believe are security-sensitive. Previously, for
      performance reasons, we had used a trivially predictable linear
      congruential generator algorithm for certain load-balancing and
      statistical sampling decisions. Now we use our fast RNG in those
      cases. Closes ticket 29542.

  o Minor features (developer tools):
    - Tor's "practracker" test script now checks for files and functions
      that seem too long and complicated. Existing overlong functions
      and files are accepted for now, but should eventually be
      refactored. Closes ticket 29221.
    - Add some scripts used for git maintenance to scripts/git. Closes
      ticket 29391.
    - Call practracker from pre-push and pre-commit git hooks to let
      developers know if they made any code style violations. Closes
      ticket 30051.
    - Add a script to check that each header has a well-formed and
      unique guard macro. Closes ticket 29756.

  o Minor features (fallback directory list):
    - Replace the 157 fallbacks originally introduced in Tor 0.3.5.6-rc
      in December 2018 (of which ~122 were still functional), with a
      list of 148 fallbacks (70 new, 78 existing, 79 removed) generated
      in June 2019. Closes ticket 28795.

  o Minor features (geoip):
    - Update geoip and geoip6 to the June 10 2019 Maxmind GeoLite2
      Country database. Closes ticket 30852.
    - Update geoip and geoip6 to the May 13 2019 Maxmind GeoLite2
      Country database. Closes ticket 30522.

  o Minor features (HTTP tunnel):
    - Return an informative web page when the HTTPTunnelPort is used as
      an HTTP proxy. Closes ticket 27821, patch by "eighthave".

  o Minor features (IPv6, v3 onion services):
    - Make v3 onion services put IPv6 addresses in service descriptors.
      Before this change, service descriptors only contained IPv4
      addresses. Implements 26992.

  o Minor features (logging):
    - Give a more useful assertion failure message if we think we have
      minherit() but we fail to make a region non-inheritable. Give a
      compile-time warning if our support for minherit() is incomplete.
      Closes ticket 30686.

  o Minor features (maintenance):
    - Add a new "make autostyle" target that developers can use to apply
      all automatic Tor style and consistency conversions to the
      codebase. Closes ticket 30539.

  o Minor features (modularity):
    - The "--disable-module-dirauth" compile-time option now disables
      even more dirauth-only code. Closes ticket 30345.

  o Minor features (performance):
    - Use OpenSSL's implementations of SHA3 when available (in OpenSSL
      1.1.1 and later), since they tend to be faster than tiny-keccak.
      Closes ticket 28837.

  o Minor features (testing):
    - The circuitpadding tests now use a reproducible RNG implementation,
      so that if a test fails, we can learn why. Part of ticket 28878.
    - Tor's tests now support an environment variable, TOR_TEST_RNG_SEED,
      to set the RNG seed for tests that use a reproducible RNG. Part of
      ticket 28878.
    - When running tests in coverage mode, take additional care to make
      our coverage deterministic, so that we can accurately track
      changes in code coverage. Closes ticket 30519.
    - Tor's unit test code now contains helper functions to replace the
      PRNG with a deterministic or reproducible version for testing.
      Previously, various tests implemented this in various ways.
      Implements ticket 29732.
    - We now have a script, cov-test-determinism.sh, to identify places
      where our unit test coverage has become nondeterministic. Closes
      ticket 29436.
    - Check that representative subsets of values of `int` and `unsigned
      int` can be represented by `void *`. Resolves issue 29537.

  o Minor bugfixes (bridge authority):
    - Bridge authorities now set bridges as running or non-running when
      about to dump their status to a file. Previously, they set bridges
      as running in response to a GETINFO command, but those shouldn't
      modify data structures. Fixes bug 24490; bugfix on 0.2.0.13-alpha.
      Patch by Neel Chauhan.

  o Minor bugfixes (channel padding statistics):
    - Channel padding write totals and padding-enabled totals are now
      counted properly in relay extrainfo descriptors. Fixes bug 29231;
      bugfix on 0.3.1.1-alpha.

  o Minor bugfixes (circuit isolation):
    - Fix a logic error that prevented the SessionGroup sub-option from
      being accepted. Fixes bug 22619; bugfix on 0.2.7.2-alpha.

  o Minor bugfixes (circuit padding):
    - Add a "CircuitPadding" torrc option to disable circuit padding.
      Fixes bug 28693; bugfix on 0.4.0.1-alpha.
    - Allow circuit padding machines to specify that they do not
      contribute much overhead, and provide consensus flags and torrc
      options to force clients to only use these low overhead machines.
      Fixes bug 29203; bugfix on 0.4.0.1-alpha.
    - Provide a consensus parameter to fully disable circuit padding, to
      be used in emergency network overload situations. Fixes bug 30173;