yggdrasil-go/CHANGELOG.md

# Changelog

All notable changes to this project will be documented in this file.

The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).

<!-- Use this as a template
## [X.Y.Z] - YYYY-MM-DD
### Added
- for new features.

### Changed
- for changes in existing functionality.

### Deprecated
- for soon-to-be removed features.

### Removed
- for now removed features.

### Fixed
- for any bug fixes.

### Security
- in case of vulnerabilities.
-->

## [0.5.5] - 2024-01-27

### Added

* A new peer option `?maxbackoff=X` has been added to control the maximum backoff time for a given peer, supports duration values like `5m`, `1h` etc

### Changed

* The maximum backoff period for failing peer connections has been reduced to just over 1 hour, compared to 4.5 hours before
* The `getPeers` endpoint now sorts peers in a more stable fashion
* Upgrade dependencies

### Fixed

* A bug where QUIC listeners could stop listening for incoming connections unexpectedly has been fixed
* The priority tiebreak between multiple peerings to the same node has been fixed
* Peer connection ordering is no longer sensitive to poor system time resolution
* The admin socket now verifies the length of input public keys
* The `PPROFLISTEN` environment variable has been fixed and now starts the pprof listener correctly
* A panic in `getPeers` has been fixed when using abstract UNIX sockets on Linux

## [0.5.4] - 2023-11-27

### Fixed

* Fixed a crash that could happen when calculating the size of bloom filters during encoding

## [0.5.3] - 2023-11-26

### Fixed

* Fixed a data race from buffered pathfinder traffic
* Fix a bug where the next-hop selection may not take shortcuts through treespace
* Backoffs are now reset correctly when a successful handshake is completed
* Backoffs will no longer exceed roughly 4.5 hours when peers are down for a long time
* The `-normaliseconf` option will now work correctly with `PrivateKeyPath`
* Improved the reliability of QUIC peering setup by disabling 0-RTT

## [0.5.2] - 2023-11-06

### Added

* New `-publickey` command line option that prints the derived public key from a configuration file
* Support for connecting to TLS peers via SOCKS with the new `sockstls://` link schema

### Changed

* Stabilise tree parent selection algorithm
* Improved logging when the TUN interface fails to set up

### Fixed

* Fixed a panic that could occur when a connection reaches an inconsistent error state
* The admin socket will now report more peering handshake error conditions in `getPeers`
* Yggdrasil will no longer panic at startup when duplicate peers are configured
* The `build` script will no longer incorrectly import `LDFLAGS` from the environment

## [0.5.1] - 2023-10-28

### Fixed

* Fix the Debian package so that upgrades are handled more smoothly

## [0.5.0] - 2023-10-28

### Added

* Authenticated peering handshake with optional password, i.e.
  * For listeners: `tls://[::]:12345?password=123456abcdef`
  * For peers: `tls://a.b.c.d:12345?password=123456abcdef`
  * For multicast interfaces with the new `Password` option in each `MulticastInterfaces` section
  * Maximum password length is 64 characters
* QUIC support for peerings, by using the new `quic://` scheme in `Listen` and `Peers`
  * This has not been extensively tested and may perform worse than TCP or TLS peers
* The private key can now be stored in PEM format separately to the main configuration file with the new `PrivateKeyPath` configuration file option
  * Use the `-exportkey` flag to export the key to a file from an existing config

### Changed

* New routing scheme, which is backwards incompatible with previous versions of Yggdrasil
  * The wire protocol version number, exchanged as part of the peer setup handshake, has been increased to 0.5
  * Nodes running this new version **will not** be able to peer with earlier versions of Yggdrasil
  * A DHT is no longer used to map public keys and routes through treespace
  * Bloom filters are used to track on-tree links and nodes reachable via that link
  * Nodes now gossip separate per-link information which is tracked in CRDT structures, forcing local consistency and preventing unnecessary flapping when a route to the root node has changed or is broken
  * Greedy routing is once again used instead of source routing
  * Per-link keepalives have been replaced with periodic acknowledgements, reducing idle bandwidth
* The link handshake and multicast beacon formats have been revised for better future extensibility
* The link code has been refactored for more robust tracking of peering states
  * As a result, the admin socket is now able to report information about configured peerings that are down
  * Reconnect intervals are now tracked separately for each configured peer with exponential backoffs

### Removed

* Yggdrasil will no longer request BBR congestion control for TCP and TLS peerings on Linux

## [0.4.7] - 2022-11-20

### Added

* Dropped outbound peerings will now try to reconnect after a single second, rather than waiting up to 60 seconds for the normal peer timer

### Changed

* Session encryption keys are now rotated at most once per minute, which reduces CPU usage and improves throughput on fast low latency links
* Buffers are now reused in the session encryption handler, which improves session throughput and reduces memory allocations
* Buffers are now reused in the router for DHT and path traffic, which improves overall routing throughput and reduces memory allocations

### Fixed

* A bug in the admin socket where requests fail unless `arguments` is specified has been fixed
* Certificates on TLS listeners will no longer expire after a year
* The `-address` and `-subnet` command line options now return a useful warning when no configuration is specified

## [0.4.6] - 2022-10-25

### Added

* Support for prioritising multiple peerings to the same node has been added, useful for nodes with multiple network interfaces
  * The priority can be configured by specifying `?priority=X` in a `Peers` or `Listen` URI, or by specifying `Priority` within a `MulticastInterfaces` configuration entry
  * Priorities are values between 0 and 254 (default is 0), lower numbers are prioritised and nodes will automatically negotiate the higher of the two values

### Changed

* On Linux, `SO_REUSEADDR` is now used on the multicast port instead of `SO_REUSEPORT`, which should allow processes running under different users to run simultaneously

### Fixed

* Adding peers using the `InterfacePeers` configuration option should now work correctly again
* Multiple connections from the same remote IP address will no longer be incorrectly dropped
* The admin socket will no longer incorrectly claim TCP connections as TLS
* A panic that could occur when calling `GetPeers` while a peering link is being set up has been fixed

## [0.4.5] - 2022-10-15

### Added

* Support for peering over UNIX sockets is now available, by configuring `Listen` and peering URIs in the `unix:///path/to/socket.sock` format

### Changed

* `yggdrasilctl` has been refactored and now has cleaner output
* It is now possible to `addPeer` and `removePeer` using the admin socket again
* The `getSessions` admin socket call reports number of bytes received and transmitted again
* The link setup code has been refactored, making it easier to support new peering types in the future
* Yggdrasil now maintains configuration internally, rather than relying on a shared and potentially mutable structure

### Fixed

* Tracking information about expired root nodes has been fixed, which should hopefully resolve issues with reparenting and connection failures when the root node disappears
* A bug in the mobile framework code which caused a crash on Android when multicast failed to set up has been fixed
* Yggdrasil should now shut down gracefully and clean up correctly when running as a Windows service

## [0.4.4] - 2022-07-07

### Fixed

* ICMPv6 "Packet Too Big" payload size has been increased, which should fix Path MTU Discovery (PMTUD) when two nodes have different `IfMTU` values configured
* A crash has been fixed when handling debug packet responses
* `yggdrasilctl getSelf` should now report coordinates correctly again

### Changed

* Go 1.17 is now required to build Yggdrasil

## [0.4.3] - 2022-02-06

### Added

* `bytes_sent`, `bytes_recvd` and `uptime` have been added to `getPeers`
* Clearer logging when connections are rejected due to incompatible peer versions

### Fixed

* Latency-based parent selection tiebreak is now reliable on platforms even with low timer resolution
* Tree distance calculation offsets have been corrected

## [0.4.2] - 2021-11-03

### Fixed

* Reverted a dependency update which resulted in problems building with Go 1.16 and running on Windows

## [0.4.1] - 2021-11-03

### Added

* TLS peerings now support Server Name Indication (SNI)
  * The SNI is sent automatically if the peering URI contains a DNS name
  * A custom SNI can be specified by adding the `?sni=domain.com` parameter to the peering URI
* A new `ipv6rwc` API package now implements the IPv6-specific logic separate from the `tun` package

### Fixed

* A crash when calculating the partial public key for very high IPv6 addresses has been fixed
* A crash due to a concurrent map write has been fixed
* A crash due to missing TUN configuration has been fixed
* A race condition in the keystore code has been fixed

## [0.4.0] - 2021-07-04

### Added

* New routing scheme, which is backwards incompatible with previous versions of Yggdrasil
  * The wire protocol version number, exchanged as part of the peer setup handshake, has been increased to 0.4
  * Nodes running this new version **will not** be able to peer with earlier versions of Yggdrasil
  * Please note that **the network may be temporarily unstable** while infrastructure is being upgraded to the new release
* TLS connections now use public key pinning
  * If no public key was already pinned, then the public key received as part of the TLS handshake is pinned to the connection
  * The public key received as part of the handshake is checked against the pinned keys, and if no match is found, the connection is rejected

### Changed

* IP addresses are now derived from ed25519 public (signing) keys
  * Previously, addresses were derived from a hash of X25519 (Diffie-Hellman) keys
  * Importantly, this means that **all internal IPv6 addresses will change with this release** — this will affect anyone running public services or relying on Yggdrasil for remote access
* It is now recommended to peer over TLS
  * Link-local peers from multicast peer discovery will now connect over TLS, with the key from the multicast beacon pinned to the connection
  * `socks://` peers now expect the destination endpoint to be a `tls://` listener, instead of a `tcp://` listener
* Multicast peer discovery is now more configurable
  * There are separate configuration options to control if beacons are sent, what port to listen on for incoming connections (if sending beacons), and whether or not to listen for beacons from other nodes (and open connections when receiving a beacon)
  * Each configuration entry in the list specifies a regular expression to match against interface names
  * If an interface matches multiple regex in the list, it will use the settings for the first entry in the list that it matches with
* The session and routing code has been entirely redesigned and rewritten
  * This is still an early work-in-progress, so the code hasn't been as well tested or optimized as the old code base — please bear with us for these next few releases as we work through any bugs or issues
  * Generally speaking, we expect to see reduced bandwidth use and improved reliability with the new design, especially in cases where nodes move around or change peerings frequently
  * Cryptographic sessions no longer use a single shared (ephemeral) secret for the entire life of the session. Keys are now rotated regularly for ongoing sessions (currently rotated at least once per round trip exchange of traffic, subject to change in future releases)
  * Source routing has been added. Under normal circumstances, this is what is used to forward session traffic (e.g. the user's IPv6 traffic)
  * DHT-based routing has been added. This is used when the sender does not know a source route to the destination. Forwarding through the DHT is less efficient, but the only information that it requires the sender to know is the destination node's (static) key. This is primarily used during the key exchange at session setup, or as a temporary fallback when a source route fails due to changes in the network
  * The new DHT design is no longer RPC-based, does not support crawling and does not inherently allow nodes to look up the owner of an arbitrary key. Responding to lookups is now implemented at the application level and a response is only sent if the destination key matches the node's `/128` IP or `/64` prefix
  * The greedy routing scheme, used to forward all traffic in previous releases, is now only used for protocol traffic (i.e. DHT setup and source route discovery)
  * The routing logic now lives in a [standalone library](https://github.com/Arceliar/ironwood). You are encouraged **not** to use it, as it's still considered pre-alpha, but it's available for those who want to experiment with the new routing algorithm in other contexts
  * Session MTUs may be slightly lower now, in order to accommodate large packet headers if required
* Many of the admin functions available over `yggdrasilctl` have been changed or removed as part of rewrites to the code
  * Several remote `debug` functions have been added temporarily, to allow for crawling and census gathering during the transition to the new version, but we intend to remove this at some point in the (possibly distant) future
  * The list of available functions will likely be expanded in future releases
* The configuration file format has been updated in response to the changed/removed features

### Removed

* Tunnel routing (a.k.a. crypto-key routing or "CKR") has been removed
  * It was far too easy to accidentally break routing altogether by capturing the route to peers with the TUN adapter
  * We recommend tunnelling an existing standard over Yggdrasil instead (e.g. `ip6gre`, `ip6gretap` or other similar encapsulations, using Yggdrasil IPv6 addresses as the tunnel endpoints)
  * All `TunnelRouting` configuration options will no longer take effect
* Session firewall has been removed
  * This was never a true firewall — it didn't behave like a stateful IP firewall, often allowed return traffic unexpectedly and was simply a way to prevent a node from being flooded with unwanted sessions, so the name could be misleading and usually lead to a false sense of security
  * Due to design changes, the new code needs to address the possible memory exhaustion attacks in other ways and a single configurable list no longer makes sense
  * Users who want a firewall or other packet filter mechansim should configure something supported by their OS instead (e.g. `ip6tables`)
  * All `SessionFirewall` configuration options will no longer take effect
* `SIGHUP` handling to reload the configuration at runtime has been removed
  * It was not obvious which parts of the configuration could be reloaded at runtime, and which required the application to be killed and restarted to take effect
  * Reloading the config without restarting was also a delicate and bug-prone process, and was distracting from more important developments
  * `SIGHUP` will be handled normally (i.e. by exiting)
* `cmd/yggrasilsim` has been removed, and is unlikely to return to this repository

## [0.3.16] - 2021-03-18

### Added

* New simulation code under `cmd/yggdrasilsim` (work-in-progress)

### Changed

* Multi-threading in the switch
  * Swich lookups happen independently for each (incoming) peer connection, instead of being funneled to a single dedicated switch worker
  * Packets are queued for each (outgoing) peer connection, instead of being handled by a single dedicated switch worker
* Queue logic rewritten
  * Heap structure per peer that traffic is routed to, with one FIFO queue per traffic flow
  * The total size of each heap is configured automatically (we basically queue packets until we think we're blocked on a socket write)
  * When adding to a full heap, the oldest packet from the largest queue is dropped
  * Packets are popped from the queue in FIFO order (oldest packet from among all queues in the heap) to prevent packet reordering at the session level
* Removed global `sync.Pool` of `[]byte`
  * Local `sync.Pool`s are used in the hot loops, but not exported, to avoid memory corruption if libraries are reused by other projects
  * This may increase allocations (and slightly reduce speed in CPU-bound benchmarks) when interacting with the tun/tap device, but traffic forwarded at the switch layer should be unaffected
* Upgrade dependencies
* Upgrade build to Go 1.16

### Fixed

* Fixed a bug where the connection listener could exit prematurely due to resoruce exhaustion (if e.g. too many connections were opened)
* Fixed DefaultIfName for OpenBSD (`/dev/tun0` -> `tun0`)
* Fixed an issue where a peer could sometimes never be added to the switch
* Fixed a goroutine leak that could occur if a peer with an open connection continued to spam additional connection attempts

## [0.3.15] - 2020-09-27

### Added

* Support for pinning remote public keys in peering strings has been added, e.g.
  * By signing public key: `tcp://host:port?ed25519=key`
  * By encryption public key: `tcp://host:port?curve25519=key`
  * By both: `tcp://host:port?ed25519=key&curve25519=key`
  * By multiple, in case of DNS round-robin or similar: `tcp://host:port?curve25519=key&curve25519=key&ed25519=key&ed25519=key`
* Some checks to prevent Yggdrasil-over-Yggdrasil peerings have been added
* Added support for SOCKS proxy authentication, e.g. `socks://user@password:host/...`

### Fixed

* Some bugs in the multicast code that could cause unnecessary CPU usage have been fixed
* A possible multicast deadlock on macOS when enumerating interfaces has been fixed
* A deadlock in the connection code has been fixed
* Updated HJSON dependency that caused some build problems

### Changed

* `DisconnectPeer` and `RemovePeer` have been separated and implemented properly now
* Less nodes are stored in the DHT now, reducing ambient network traffic and possible instability
* Default config file for FreeBSD is now at `/usr/local/etc/yggdrasil.conf` instead of `/etc/yggdrasil.conf`

## [0.3.14] - 2020-03-28

### Fixed

* Fixes a memory leak that may occur if packets are incorrectly never removed from a switch queue

### Changed

* Make DHT searches a bit more reliable by tracking the 16 most recently visited nodes

## [0.3.13] - 2020-02-21

### Added

* Support for the Wireguard TUN driver, which now replaces Water and provides far better support and performance on Windows
* Windows `.msi` installer files are now supported (bundling the Wireguard TUN driver)
* NodeInfo code is now actorised, should be more reliable
* The DHT now tries to store the two closest nodes in either direction instead of one, such that if a node goes offline, the replacement is already known
* The Yggdrasil API now supports dialing a remote node using the public key instead of the Node ID

### Changed

* The `-loglevel` command line parameter is now cumulative and automatically includes all levels below the one specified
* DHT search code has been significantly simplified and processes rumoured nodes in parallel, speeding up search time
* DHT search results are now sorted
* The systemd service now handles configuration generation in a different unit
* The Yggdrasil API now returns public keys instead of node IDs when querying for local and remote addresses

### Fixed

* The multicast code no longer panics when shutting down the node
* A potential OOB error when calculating IPv4 flow labels (when tunnel routing is enabled) has been fixed
* A bug resulting in incorrect idle notifications in the switch should now be fixed
* MTUs are now using a common datatype throughout the codebase

### Removed

* TAP mode has been removed entirely, since it is no longer supported with the Wireguard TUN package. Please note that if you are using TAP mode, you may need to revise your config!
* NetBSD support has been removed until the Wireguard TUN package supports NetBSD

## [0.3.12] - 2019-11-24

### Added

* New API functions `SetMaximumSessionMTU` and `GetMaximumSessionMTU`
* New command line parameters `-address` and `-subnet` for getting the address/subnet from the config file, for use with `-useconffile` or `-useconf`
* A warning is now produced in the Yggdrasil output at startup when the MTU in the config is invalid or has been adjusted for some reason

### Changed

* On Linux, outgoing `InterfacePeers` connections now use `SO_BINDTODEVICE` to prefer an outgoing interface
* The `genkeys` utility is now in `cmd` rather than `misc`

### Fixed

* A data race condition has been fixed when updating session coordinates
* A crash when shutting down when no multicast interfaces are configured has been fixed
* A deadlock when calling `AddPeer` multiple times has been fixed
* A typo in the systemd unit file (for some Linux packages) has been fixed
* The NodeInfo and admin socket now report `unknown` correctly when no build name/version is available in the environment at build time
* The MTU calculation now correctly accounts for ethernet headers when running in TAP mode

## [0.3.11] - 2019-10-25

### Added

* Support for TLS listeners and peers has been added, allowing the use of `tls://host:port` in `Peers`, `InterfacePeers` and `Listen` configuration settings - this allows hiding Yggdrasil peerings inside regular TLS connections

### Changed

* Go 1.13 or later is now required for building Yggdrasil
* Some exported API functions have been updated to work with standard Go interfaces:
  * `net.Conn` instead of `yggdrasil.Conn`
  * `net.Dialer` (the interface it would satisfy if it wasn't a concrete type) instead of `yggdrasil.Dialer`
  * `net.Listener` instead of `yggdrasil.Listener`
* Session metadata is now updated correctly when a search completes for a node to which we already have an open session
* Multicast module reloading behaviour has been improved

### Fixed

* An incorrectly held mutex in the crypto-key routing code has been fixed
* Multicast module no longer opens a listener socket if no multicast interfaces are configured

## [0.3.10] - 2019-10-10

### Added

* The core library now includes several unit tests for peering and `yggdrasil.Conn` connections

### Changed

* On recent Linux kernels, Yggdrasil will now set the `tcp_congestion_control` algorithm used for its own TCP sockets to [BBR](https://github.com/google/bbr), which reduces latency under load
* The systemd service configuration in `contrib` (and, by extension, some of our packages) now attempts to load the `tun` module, in case TUN/TAP support is available but not loaded, and it restricts Yggdrasil to the `CAP_NET_ADMIN` capability for managing the TUN/TAP adapter, rather than letting it do whatever the (typically `root`) user can do

### Fixed

* The `yggdrasil.Conn.RemoteAddr()` function no longer blocks, fixing a deadlock when CKR is used while under heavy load

## [0.3.9] - 2019-09-27

### Added

* Yggdrasil will now complain more verbosely when a peer URI is incorrectly formatted
* Soft-shutdown methods have been added, allowing a node to shut down gracefully when terminated
* New multicast interval logic which sends multicast beacons more often when Yggdrasil is first started to increase the chance of finding nearby nodes quickly after startup

### Changed

* The switch now buffers packets more eagerly in an attempt to give the best link a chance to send, which appears to reduce packet reordering when crossing aggregate sets of peerings
* Substantial amounts of the codebase have been refactored to use the actor model, which should substantially reduce the chance of deadlocks
* Nonce tracking in sessions has been modified so that memory usage is reduced whilst still only allowing duplicate packets within a small window
* Soft-reconfiguration support has been simplified using new actor functions
* The garbage collector threshold has been adjusted for mobile builds
* The maximum queue size is now managed exclusively by the switch rather than by the core

### Fixed

* The broken `hjson-go` dependency which affected builds of the previous version has now been resolved in the module manifest
* Some minor memory leaks in the switch have been fixed, which improves memory usage on mobile builds
* A memory leak in the add-peer loop has been fixed
* The admin socket now reports the correct URI strings for SOCKS peers in `getPeers`
* A race condition when dialing a remote node by both the node address and routed prefix simultaneously has been fixed
* A race condition between the router and the dial code resulting in a panic has been fixed
* A panic which could occur when the TUN/TAP interface disappears (e.g. during soft-shutdown) has been fixed
* A bug in the semantic versioning script which accompanies Yggdrasil for builds has been fixed
* A panic which could occur when the TUN/TAP interface reads an undersized/corrupted packet has been fixed

### Removed

* A number of legacy debug functions have now been removed and a number of exported API functions are now better documented

## [0.3.8] - 2019-08-21

### Changed

* Yggdrasil can now send multiple packets from the switch at once, which results in improved throughput with smaller packets or lower MTUs
* Performance has been slightly improved by not allocating cancellations where not necessary
* Crypto-key routing options have been renamed for clarity
  * `IPv4Sources` is now named `IPv4LocalSubnets`
  * `IPv6Sources` is now named `IPv6LocalSubnets`
  * `IPv4Destinations` is now named `IPv4RemoteSubnets`
  * `IPv6Destinations` is now named `IPv6RemoteSubnets`
  * The old option names will continue to be accepted by the configuration parser for now but may not be indefinitely
* When presented with multiple paths between two nodes, the switch now prefers the most recently used port when possible instead of the least recently used, helping to reduce packet reordering
* New nonce tracking should help to reduce the number of packets dropped as a result of multiple/aggregate paths or congestion control in the switch

### Fixed

* A deadlock was fixed in the session code which could result in Yggdrasil failing to pass traffic after some time

### Security

* Address verification was not strict enough, which could result in a malicious session sending traffic with unexpected or spoofed source or destination addresses which Yggdrasil could fail to reject
  * Versions `0.3.6` and `0.3.7` are vulnerable - users of these versions should upgrade as soon as possible
  * Versions `0.3.5` and earlier are not affected

## [0.3.7] - 2019-08-14

### Changed

* The switch should now forward packets along a single path more consistently in cases where congestion is low and multiple equal-length paths exist, which should improve stability and result in fewer out-of-order packets
* Sessions should now be more tolerant of out-of-order packets, by replacing a bitmask with a variable sized heap+map structure to track recently received nonces, which should reduce the number of packets dropped due to reordering when multiple paths are used or multiple independent flows are transmitted through the same session
* The admin socket can no longer return a dotfile representation of the known parts of the network, this could be rebuilt by clients using information from `getSwitchPeers`,`getDHT` and `getSessions`

### Fixed

* A number of significant performance regressions introduced in version 0.3.6 have been fixed, resulting in better performance
* Flow labels are now used to prioritise traffic flows again correctly
* In low-traffic scenarios where there are multiple peerings between a pair of nodes, Yggdrasil now prefers the most active peering instead of the least active, helping to reduce packet reordering
* The `Listen` statement, when configured as a string rather than an array, will now be parsed correctly
* The admin socket now returns `coords` as a correct array of unsigned 64-bit integers, rather than the internal representation
* The admin socket now returns `box_pub_key` in string format again
* Sessions no longer leak/block when no listener (e.g. TUN/TAP) is configured
* Incoming session connections no longer block when a session already exists, which results in less leaked goroutines
* Flooded sessions will no longer block other sessions
* Searches are now cleaned up properly and a couple of edge-cases with duplicate searches have been fixed
* A number of minor allocation and pointer fixes

## [0.3.6] - 2019-08-03

### Added

* Yggdrasil now has a public API with interfaces such as `yggdrasil.ConnDialer`, `yggdrasil.ConnListener` and `yggdrasil.Conn` for using Yggdrasil as a transport directly within applications
* Session gatekeeper functions, part of the API, which can be used to control whether to allow or reject incoming or outgoing sessions dynamically (compared to the previous fixed whitelist/blacklist approach)
* Support for logging to files or syslog (where supported)
* Platform defaults now include the ability to set sane defaults for multicast interfaces

### Changed

* Following a massive refactoring exercise, Yggdrasil's codebase has now been broken out into modules
* Core node functionality in the `yggdrasil` package with a public API
  * This allows Yggdrasil to be integrated directly into other applications and used as a transport
  * IP-specific code has now been moved out of the core `yggdrasil` package, making Yggdrasil effectively protocol-agnostic
* Multicast peer discovery functionality is now in the `multicast` package
* Admin socket functionality is now in the `admin` package and uses the Yggdrasil public API
* TUN/TAP, ICMPv6 and all IP-specific functionality is now in the `tuntap` package
* `PPROF` debug output is now sent to `stderr` instead of `stdout`
* Node IPv6 addresses on macOS are now configured as `secured`
* Upstream dependency references have been updated, which includes a number of fixes in the Water library

### Fixed

* Multicast discovery is no longer disabled if the nominated interfaces aren't available on the system yet, e.g. during boot
* Multicast interfaces are now re-evaluated more frequently so that Yggdrasil doesn't need to be restarted to use interfaces that have become available since startup
* Admin socket error cases are now handled better
* Various fixes in the TUN/TAP module, particularly surrounding Windows platform support
* Invalid keys will now cause the node to fail to start, rather than starting but silently not working as before
* Session MTUs are now always calculated correctly, in some cases they were incorrectly defaulting to 1280 before
* Multiple searches now don't take place for a single connection
* Concurrency bugs fixed
* Fixed a number of bugs in the ICMPv6 neighbor solicitation in the TUN/TAP code
* A case where peers weren't always added correctly if one or more peers were unreachable has been fixed
* Searches which include the local node are now handled correctly
* Lots of small bug tweaks and clean-ups throughout the codebase

## [0.3.5] - 2019-03-13

### Fixed

* The `AllowedEncryptionPublicKeys` option has now been fixed to handle incoming connections properly and no longer blocks outgoing connections (this was broken in v0.3.4)
* Multicast TCP listeners will now be stopped correctly when the link-local address on the interface changes or disappears altogether

## [0.3.4] - 2019-03-12

### Added

* Support for multiple listeners (although currently only TCP listeners are supported)
* New multicast behaviour where each multicast interface is given its own link-local listener and does not depend on the `Listen` configuration
* Blocking detection in the switch to avoid parenting a blocked peer
* Support for adding and removing listeners and multicast interfaces when reloading configuration during runtime
* Yggdrasil will now attempt to clean up UNIX admin sockets on startup if left behind by a previous crash
* Admin socket `getTunnelRouting` and `setTunnelRouting` calls for enabling and disabling crypto-key routing during runtime
* On macOS, Yggdrasil will now try to wake up AWDL on start-up when `awdl0` is a configured multicast interface, to keep it awake after system sleep, and to stop waking it when no longer needed
* Added `LinkLocalTCPPort` option for controlling the port number that link-local TCP listeners will listen on by default when setting up `MulticastInterfaces` (a node restart is currently required for changes to `LinkLocalTCPPort` to take effect - it cannot be updated by reloading config during runtime)

### Changed

* The `Listen` configuration statement is now an array instead of a string
* The `Listen` configuration statement should now conform to the same formatting as peers with the protocol prefix, e.g. `tcp://[::]:0`
* Session workers are now non-blocking
* Multicast interval is now fixed at every 15 seconds and network interfaces are reevaluated for eligibility on each interval (where before the interval depended upon the number of configured multicast interfaces and evaluation only took place at startup)
* Dead connections are now closed in the link handler as opposed to the switch
* Peer forwarding is now prioritised instead of randomised

### Fixed

* Admin socket `getTunTap` call now returns properly instead of claiming no interface is enabled in all cases
* Handling of `getRoutes` etc in `yggdrasilctl` is now working
* Local interface names are no longer leaked in multicast packets
* Link-local TCP connections, particularly those initiated because of multicast beacons, are now always correctly scoped for the target interface
* Yggdrasil now correctly responds to multicast interfaces going up and down during runtime

## [0.3.3] - 2019-02-18

### Added

* Dynamic reconfiguration, which allows reloading the configuration file to make changes during runtime by sending a `SIGHUP` signal (note: this only works with `-useconffile` and not `-useconf` and currently reconfiguring TUN/TAP is not supported)
* Support for building Yggdrasil as an iOS or Android framework if the appropriate tools (e.g. `gomobile`/`gobind` + SDKs) are available
* Connection contexts used for TCP connections which allow more exotic socket options to be set, e.g.
  * Reusing the multicast socket to allow multiple running Yggdrasil instances without having to disable multicast
  * Allowing supported Macs to peer with other nearby Macs that aren't even on the same Wi-Fi network using AWDL
* Flexible logging support, which allows for logging at different levels of verbosity

### Changed

* Switch changes to improve parent selection
* Node configuration is now stored centrally, rather than having fragments/copies distributed at startup time
* Significant refactoring in various areas, including for link types (TCP, AWDL etc), generic streams and adapters
* macOS builds through CircleCI are now 64-bit only

### Fixed

* Simplified `systemd` service now in `contrib`

### Removed

* `ReadTimeout` option is now deprecated

## [0.3.2] - 2018-12-26

### Added

* The admin socket is now multithreaded, greatly improving performance of the crawler and allowing concurrent lookups to take place
* The ability to hide NodeInfo defaults through either setting the `NodeInfoPrivacy` option or through setting individual `NodeInfo` attributes to `null`

### Changed

* The `armhf` build now targets ARMv6 instead of ARMv7, adding support for Raspberry Pi Zero and other older models, amongst others

### Fixed

* DHT entries are now populated using a copy in memory to fix various potential DHT bugs
* DHT traffic should now throttle back exponentially to reduce idle traffic
* Adjust how nodes are inserted into the DHT which should help to reduce some incorrect DHT traffic
* In TAP mode, the NDP target address is now correctly used when populating the peer MAC table. This fixes serious connectivity problems when in TAP mode, particularly on BSD
* In TUN mode, ICMPv6 packets are now ignored whereas they were incorrectly processed before

## [0.3.1] - 2018-12-17

### Added

* Build name and version is now imprinted onto the binaries if available/specified during build
* Ability to disable admin socket with `AdminListen: none`
* `AF_UNIX` domain sockets for the admin socket
* Cache size restriction for crypto-key routes
* `NodeInfo` support for specifying node information, e.g. node name or contact, which can be used in network crawls or surveys
* `getNodeInfo` request added to admin socket
* Adds flags `-c`, `-l` and `-t` to `build` script for specifying `GCFLAGS`, `LDFLAGS` or whether to keep symbol/DWARF tables

### Changed

* Default `AdminListen` in newly generated config is now `unix:///var/run/yggdrasil.sock`
* Formatting of `getRoutes` in the admin socket has been improved
* Debian package now adds `yggdrasil` group to assist with `AF_UNIX` admin socket permissions
* Crypto, address and other utility code refactored into separate Go packages

### Fixed

* Switch peer convergence is now much faster again (previously it was taking up to a minute once the peering was established)
* `yggdrasilctl` is now less prone to crashing when parameters are specified incorrectly
* Panic fixed when `Peers` or `InterfacePeers` was commented out

## [0.3.0] - 2018-12-12

### Added

* Crypto-key routing support for tunnelling both IPv4 and IPv6 over Yggdrasil
* Add advanced `SwitchOptions` in configuration file for tuning the switch
* Add `dhtPing` to the admin socket to aid in crawling the network
* New macOS .pkgs built automatically by CircleCI
* Add Dockerfile to repository for Docker support
* Add `-json` command line flag for generating and normalising configuration in plain JSON instead of HJSON
* Build name and version numbers are now imprinted onto the build, accessible through `yggdrasil -version` and `yggdrasilctl getSelf`
* Add ability to disable admin socket by setting `AdminListen` to `"none"`
* `yggdrasilctl` now tries to look for the default configuration file to find `AdminListen` if `-endpoint` is not specified
* `yggdrasilctl` now returns more useful logging in the event of a fatal error

### Changed

* Switched to Chord DHT (instead of Kademlia, although still compatible at the protocol level)
* The `AdminListen` option and `yggdrasilctl` now default to `unix:///var/run/yggdrasil.sock` on BSDs, macOS and Linux
* Cleaned up some of the parameter naming in the admin socket
* Latency-based parent selection for the switch instead of uptime-based (should help to avoid high latency links somewhat)
* Real peering endpoints now shown in the admin socket `getPeers` call to help identify peerings
* Reuse the multicast port on supported platforms so that multiple Yggdrasil processes can run
* `yggdrasilctl` now has more useful help text (with `-help` or when no arguments passed)

### Fixed

* Memory leaks in the DHT fixed
* Crash fixed where the ICMPv6 NDP goroutine would incorrectly start in TUN mode
* Removing peers from the switch table if they stop sending switch messages but keep the TCP connection alive

## [0.2.7] - 2018-10-13

### Added

* Session firewall, which makes it possible to control who can open sessions with your node
* Add `getSwitchQueues` to admin socket
* Add `InterfacePeers` for configuring static peerings via specific network interfaces
* More output shown in `getSwitchPeers`
* FreeBSD service script in `contrib`

## Changed

* CircleCI builds are now built with Go 1.11 instead of Go 1.9

## Fixed

* Race condition in the switch table, reported by trn
* Debug builds are now tested by CircleCI as well as platform release builds
* Port number fixed on admin graph from unknown nodes

## [0.2.6] - 2018-07-31

### Added

* Configurable TCP timeouts to assist in peering over Tor/I2P
* Prefer IPv6 flow label when extending coordinates to sort backpressure queues
* `arm64` builds through CircleCI

### Changed

* Sort dot graph links by integer value

## [0.2.5] - 2018-07-19

### Changed

* Make `yggdrasilctl` less case sensitive
* More verbose TCP disconnect messages

### Fixed

* Fixed debug builds
* Cap maximum MTU on Linux in TAP mode
* Process successfully-read TCP traffic before checking for / handling errors (fixes EOF behavior)

## [0.2.4] - 2018-07-08

### Added

* Support for UNIX domain sockets for the admin socket using `unix:///path/to/file.sock`
* Centralised platform-specific defaults

### Changed

* Backpressure tuning, including reducing resource consumption

### Fixed

* macOS local ping bug, which previously prevented you from pinging your own `utun` adapter's IPv6 address

## [0.2.3] - 2018-06-29

### Added

* Begin keeping changelog (incomplete and possibly inaccurate information before this point).
* Build RPMs in CircleCI using alien. This provides package support for Fedora, Red Hat Enterprise Linux, CentOS and other RPM-based distributions.

### Changed

* Local backpressure improvements.
* Change `box_pub_key` to `key` in admin API for simplicity.
* Session cleanup.

## [0.2.2] - 2018-06-21

### Added

* Add `yggdrasilconf` utility for testing with the `vyatta-yggdrasil` package.
* Add a randomized retry delay after TCP disconnects, to prevent synchronization livelocks.

### Changed

* Update build script to strip by default, which significantly reduces the size of the binary.
* Add debug `-d` and UPX `-u` flags to the `build` script.
* Start pprof in debug builds based on an environment variable (e.g. `PPROFLISTEN=localhost:6060`), instead of a flag.

### Fixed

* Fix typo in big-endian BOM so that both little-endian and big-endian UTF-16 files are detected correctly.

## [0.2.1] - 2018-06-15

### Changed

* The address range was moved from `fd00::/8` to `200::/7`. This range was chosen as it is marked as deprecated. The change prevents overlap with other ULA privately assigned ranges.

### Fixed

* UTF-16 detection conversion for configuration files, which can particularly be a problem on Windows 10 if a configuration file is generated from within PowerShell.
* Fixes to the Debian package control file.
* Fixes to the launchd service for macOS.
* Fixes to the DHT and switch.

## [0.2.0] - 2018-06-13

### Added

* Exchange version information during connection setup, to prevent connections with incompatible versions.

### Changed

* Wire format changes (backwards incompatible).
* Less maintenance traffic per peer.
* Exponential back-off for DHT maintenance traffic (less maintenance traffic for known good peers).
* Iterative DHT (added sometime between v0.1.0 and here).
* Use local queue sizes for a sort of local-only backpressure routing, instead of the removed bandwidth estimates, when deciding where to send a packet.

### Removed

* UDP peering, this may be added again if/when a better implementation appears.
* Per peer bandwidth estimation, as this has been replaced with an early local backpressure implementation.

## [0.1.0] - 2018-02-01

### Added

* Adopt semantic versioning.

### Changed

* Wire format changes (backwards incompatible).
* Many other undocumented changes leading up to this release and before the next one.

## [0.0.1] - 2017-12-28

### Added

* First commit.
* Initial public release.