a0178bf873
In this PR, we create a new package, `protofsm` which is intended to
abstract away from something we've done dozens of time in the daemon:
create a new event-drive protocol FSM. One example of this is the co-op
close state machine, and also the channel state machine itself.
This packages picks out the common themes of:
* clear states and transitions between them
* calling out to special daemon adapters for I/O such as transaction
broadcast or sending a message to a peer
* cleaning up after state machine execution
* notifying relevant callers of updates to the state machine
The goal of this PR, is that devs can now implement a state machine
based off of this primary interface:
```go
// State defines an abstract state along, namely its state transition function
// that takes as input an event and an environment, and returns a state
// transition (next state, and set of events to emit). As state can also either
// be terminal, or not, a terminal event causes state execution to halt.
type State[Event any, Env Environment] interface {
// ProcessEvent takes an event and an environment, and returns a new
// state transition. This will be iteratively called until either a
// terminal state is reached, or no further internal events are
// emitted.
ProcessEvent(event Event, env Env) (*StateTransition[Event, Env], error)
// IsTerminal returns true if this state is terminal, and false otherwise.
IsTerminal() bool
}
```
With their focus being _only_ on each state transition, rather than all
the boiler plate involved (processing new events, advancing to
completion, doing I/O, etc, etc).
Instead, they just make their states, then create the state machine
given the starting state and env. The only other custom component needed
is something capable of mapping wire messages or other events from the
"outside world" into the domain of the state machine.
The set of types is based on a pseudo sum type system wherein you
declare an interface, make the sole method private, then create other
instances based on that interface. This restricts call sites (must pass
in that interface) type, and with some tooling, exhaustive matching can
also be enforced via a linter.
The best way to get a hang of the pattern proposed here is to check out
the tests. They make a mock state machine, and then use the new executor
to drive it to completion. You'll also get a view of how the code will
actually look, with the focus being on the: input event, current state,
and output transition (can also emit events to drive itself forward).
Lightning Network Daemon
The Lightning Network Daemon (lnd) - is a complete implementation of a
Lightning Network node. lnd has several pluggable back-end
chain services including btcd (a
full-node), bitcoind, and
neutrino (a new experimental light client). The project's codebase uses the
btcsuite set of Bitcoin libraries, and also
exports a large set of isolated re-usable Lightning Network related libraries
within it. In the current state lnd is capable of:
- Creating channels.
- Closing channels.
- Completely managing all channel states (including the exceptional ones!).
- Maintaining a fully authenticated+validated channel graph.
- Performing path finding within the network, passively forwarding incoming payments.
- Sending outgoing onion-encrypted payments through the network.
- Updating advertised fee schedules.
- Automatic channel management (
autopilot).
Lightning Network Specification Compliance
lnd fully conforms to the Lightning Network specification
(BOLTs). BOLT stands for:
Basis of Lightning Technology. The specifications are currently being drafted
by several groups of implementers based around the world including the
developers of lnd. The set of specification documents as well as our
implementation of the specification are still a work-in-progress. With that
said, the current status of lnd's BOLT compliance is:
- BOLT 1: Base Protocol
- BOLT 2: Peer Protocol for Channel Management
- BOLT 3: Bitcoin Transaction and Script Formats
- BOLT 4: Onion Routing Protocol
- BOLT 5: Recommendations for On-chain Transaction Handling
- BOLT 7: P2P Node and Channel Discovery
- BOLT 8: Encrypted and Authenticated Transport
- BOLT 9: Assigned Feature Flags
- BOLT 10: DNS Bootstrap and Assisted Node Location
- BOLT 11: Invoice Protocol for Lightning Payments
Developer Resources
The daemon has been designed to be as developer friendly as possible in order
to facilitate application development on top of lnd. Two primary RPC
interfaces are exported: an HTTP REST API, and a gRPC
service. The exported APIs are not yet stable, so be warned: they may change
drastically in the near future.
An automatically generated set of documentation for the RPC APIs can be found at api.lightning.community. A set of developer resources including guides, articles, example applications and community resources can be found at: docs.lightning.engineering.
Finally, we also have an active
Slack where protocol developers, application developers, testers and users gather to
discuss various aspects of lnd and also Lightning in general.
Installation
In order to build from source, please see the installation instructions.
Docker
To run lnd from Docker, please see the main Docker instructions
IRC
- irc.libera.chat
- channel #lnd
- webchat
Safety
When operating a mainnet lnd node, please refer to our operational safety
guidelines. It is important to note that lnd is still
beta software and that ignoring these operational guidelines can lead to
loss of funds.
Security
The developers of lnd take security very seriously. The disclosure of
security vulnerabilities helps us secure the health of lnd, privacy of our
users, and also the health of the Lightning Network as a whole. If you find
any issues regarding security or privacy, please disclose the information
responsibly by sending an email to security at lightning dot engineering,
preferably encrypted using our designated PGP key
(91FE464CD75101DA6B6BAB60555C6465E5BCB3AF) which can be found
here.