lnd.xprv/lnrpc/chainrpc/chainnotifier_server.go

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// +build chainrpc
package chainrpc
import (
"bytes"
"context"
"errors"
"io/ioutil"
"os"
"path/filepath"
"sync"
"github.com/btcsuite/btcd/chaincfg/chainhash"
"github.com/btcsuite/btcd/wire"
"github.com/lightningnetwork/lnd/chainntnfs"
"github.com/lightningnetwork/lnd/lnrpc"
"google.golang.org/grpc"
"gopkg.in/macaroon-bakery.v2/bakery"
)
const (
// subServerName is the name of the RPC sub-server. We'll use this name
// to register ourselves, and we also require that the main
// SubServerConfigDispatcher instance recognize this as the name of the
// config file that we need.
subServerName = "ChainRPC"
)
var (
// macaroonOps are the set of capabilities that our minted macaroon (if
// it doesn't already exist) will have.
macaroonOps = []bakery.Op{
{
Entity: "onchain",
Action: "read",
},
}
// macPermissions maps RPC calls to the permissions they require.
macPermissions = map[string][]bakery.Op{
"/chainrpc.ChainNotifier/RegisterConfirmationsNtfn": {{
Entity: "onchain",
Action: "read",
}},
"/chainrpc.ChainNotifier/RegisterSpendNtfn": {{
Entity: "onchain",
Action: "read",
}},
"/chainrpc.ChainNotifier/RegisterBlockEpochNtfn": {{
Entity: "onchain",
Action: "read",
}},
}
// DefaultChainNotifierMacFilename is the default name of the chain
// notifier macaroon that we expect to find via a file handle within the
// main configuration file in this package.
DefaultChainNotifierMacFilename = "chainnotifier.macaroon"
// ErrChainNotifierServerShuttingDown is an error returned when we are
// waiting for a notification to arrive but the chain notifier server
// has been shut down.
ErrChainNotifierServerShuttingDown = errors.New("chain notifier RPC " +
"subserver shutting down")
)
// fileExists reports whether the named file or directory exists.
func fileExists(name string) bool {
if _, err := os.Stat(name); err != nil {
if os.IsNotExist(err) {
return false
}
}
return true
}
// Server is a sub-server of the main RPC server: the chain notifier RPC. This
// RPC sub-server allows external callers to access the full chain notifier
// capabilities of lnd. This allows callers to create custom protocols, external
// to lnd, even backed by multiple distinct lnd across independent failure
// domains.
type Server struct {
started sync.Once
stopped sync.Once
cfg Config
quit chan struct{}
}
// New returns a new instance of the chainrpc ChainNotifier sub-server. We also
// return the set of permissions for the macaroons that we may create within
// this method. If the macaroons we need aren't found in the filepath, then
// we'll create them on start up. If we're unable to locate, or create the
// macaroons we need, then we'll return with an error.
func New(cfg *Config) (*Server, lnrpc.MacaroonPerms, error) {
// If the path of the chain notifier macaroon wasn't generated, then
// we'll assume that it's found at the default network directory.
if cfg.ChainNotifierMacPath == "" {
cfg.ChainNotifierMacPath = filepath.Join(
cfg.NetworkDir, DefaultChainNotifierMacFilename,
)
}
// Now that we know the full path of the chain notifier macaroon, we can
// check to see if we need to create it or not.
macFilePath := cfg.ChainNotifierMacPath
if cfg.MacService != nil && !fileExists(macFilePath) {
log.Infof("Baking macaroons for ChainNotifier RPC Server at: %v",
macFilePath)
// At this point, we know that the chain notifier macaroon
// doesn't yet, exist, so we need to create it with the help of
// the main macaroon service.
chainNotifierMac, err := cfg.MacService.Oven.NewMacaroon(
context.Background(), bakery.LatestVersion, nil,
macaroonOps...,
)
if err != nil {
return nil, nil, err
}
chainNotifierMacBytes, err := chainNotifierMac.M().MarshalBinary()
if err != nil {
return nil, nil, err
}
err = ioutil.WriteFile(macFilePath, chainNotifierMacBytes, 0644)
if err != nil {
os.Remove(macFilePath)
return nil, nil, err
}
}
return &Server{
cfg: *cfg,
quit: make(chan struct{}),
}, macPermissions, nil
}
// Compile-time checks to ensure that Server fully implements the
// ChainNotifierServer gRPC service and lnrpc.SubServer interface.
var _ ChainNotifierServer = (*Server)(nil)
var _ lnrpc.SubServer = (*Server)(nil)
// Start launches any helper goroutines required for the server to function.
//
// NOTE: This is part of the lnrpc.SubServer interface.
func (s *Server) Start() error {
s.started.Do(func() {})
return nil
}
// Stop signals any active goroutines for a graceful closure.
//
// NOTE: This is part of the lnrpc.SubServer interface.
func (s *Server) Stop() error {
s.stopped.Do(func() {
close(s.quit)
})
return nil
}
// Name returns a unique string representation of the sub-server. This can be
// used to identify the sub-server and also de-duplicate them.
//
// NOTE: This is part of the lnrpc.SubServer interface.
func (s *Server) Name() string {
return subServerName
}
// RegisterWithRootServer will be called by the root gRPC server to direct a RPC
// sub-server to register itself with the main gRPC root server. Until this is
// called, each sub-server won't be able to have requests routed towards it.
//
// NOTE: This is part of the lnrpc.SubServer interface.
func (s *Server) RegisterWithRootServer(grpcServer *grpc.Server) error {
// We make sure that we register it with the main gRPC server to ensure
// all our methods are routed properly.
RegisterChainNotifierServer(grpcServer, s)
log.Debug("ChainNotifier RPC server successfully register with root " +
"gRPC server")
return nil
}
// RegisterConfirmationsNtfn is a synchronous response-streaming RPC that
// registers an intent for a client to be notified once a confirmation request
// has reached its required number of confirmations on-chain.
//
// A client can specify whether the confirmation request should be for a
// particular transaction by its hash or for an output script by specifying a
// zero hash.
//
// NOTE: This is part of the chainrpc.ChainNotifierService interface.
func (s *Server) RegisterConfirmationsNtfn(in *ConfRequest,
confStream ChainNotifier_RegisterConfirmationsNtfnServer) error {
// We'll start by reconstructing the RPC request into what the
// underlying ChainNotifier expects.
var txid chainhash.Hash
copy(txid[:], in.Txid)
// We'll then register for the spend notification of the request.
confEvent, err := s.cfg.ChainNotifier.RegisterConfirmationsNtfn(
&txid, in.Script, in.NumConfs, in.HeightHint,
)
if err != nil {
return err
}
defer confEvent.Cancel()
// With the request registered, we'll wait for its spend notification to
// be dispatched.
for {
select {
// The transaction satisfying the request has confirmed on-chain
// and reached its required number of confirmations. We'll
// dispatch an event to the caller indicating so.
case details, ok := <-confEvent.Confirmed:
if !ok {
return chainntnfs.ErrChainNotifierShuttingDown
}
var rawTxBuf bytes.Buffer
err := details.Tx.Serialize(&rawTxBuf)
if err != nil {
return err
}
rpcConfDetails := &ConfDetails{
RawTx: rawTxBuf.Bytes(),
BlockHash: details.BlockHash[:],
BlockHeight: details.BlockHeight,
TxIndex: details.TxIndex,
}
conf := &ConfEvent{
Event: &ConfEvent_Conf{
Conf: rpcConfDetails,
},
}
if err := confStream.Send(conf); err != nil {
return err
}
// The transaction satisfying the request has been reorged out
// of the chain, so we'll send an event describing so.
case _, ok := <-confEvent.NegativeConf:
if !ok {
return chainntnfs.ErrChainNotifierShuttingDown
}
reorg := &ConfEvent{
Event: &ConfEvent_Reorg{Reorg: &Reorg{}},
}
if err := confStream.Send(reorg); err != nil {
return err
}
// The transaction satisfying the request has confirmed and is
// no longer under the risk of being reorged out of the chain,
// so we can safely exit.
case _, ok := <-confEvent.Done:
if !ok {
return chainntnfs.ErrChainNotifierShuttingDown
}
return nil
// The response stream's context for whatever reason has been
// closed. We'll return the error indicated by the context
// itself to the caller.
case <-confStream.Context().Done():
return confStream.Context().Err()
// The server has been requested to shut down.
case <-s.quit:
return ErrChainNotifierServerShuttingDown
}
}
}
// RegisterSpendNtfn is a synchronous response-streaming RPC that registers an
// intent for a client to be notification once a spend request has been spent by
// a transaction that has confirmed on-chain.
//
// A client can specify whether the spend request should be for a particular
// outpoint or for an output script by specifying a zero outpoint.
//
// NOTE: This is part of the chainrpc.ChainNotifierService interface.
func (s *Server) RegisterSpendNtfn(in *SpendRequest,
spendStream ChainNotifier_RegisterSpendNtfnServer) error {
// We'll start by reconstructing the RPC request into what the
// underlying ChainNotifier expects.
var op *wire.OutPoint
if in.Outpoint != nil {
var txid chainhash.Hash
copy(txid[:], in.Outpoint.Hash)
op = &wire.OutPoint{Hash: txid, Index: in.Outpoint.Index}
}
// We'll then register for the spend notification of the request.
spendEvent, err := s.cfg.ChainNotifier.RegisterSpendNtfn(
op, in.Script, in.HeightHint,
)
if err != nil {
return err
}
defer spendEvent.Cancel()
// With the request registered, we'll wait for its spend notification to
// be dispatched.
for {
select {
// A transaction that spends the given has confirmed on-chain.
// We'll return an event to the caller indicating so that
// includes the details of the spending transaction.
case details, ok := <-spendEvent.Spend:
if !ok {
return chainntnfs.ErrChainNotifierShuttingDown
}
var rawSpendingTxBuf bytes.Buffer
err := details.SpendingTx.Serialize(&rawSpendingTxBuf)
if err != nil {
return err
}
rpcSpendDetails := &SpendDetails{
SpendingOutpoint: &Outpoint{
Hash: details.SpentOutPoint.Hash[:],
Index: details.SpentOutPoint.Index,
},
RawSpendingTx: rawSpendingTxBuf.Bytes(),
SpendingTxHash: details.SpenderTxHash[:],
SpendingInputIndex: details.SpenderInputIndex,
SpendingHeight: uint32(details.SpendingHeight),
}
spend := &SpendEvent{
Event: &SpendEvent_Spend{
Spend: rpcSpendDetails,
},
}
if err := spendStream.Send(spend); err != nil {
return err
}
// The spending transaction of the request has been reorged of
// the chain. We'll return an event to the caller indicating so.
case _, ok := <-spendEvent.Reorg:
if !ok {
return chainntnfs.ErrChainNotifierShuttingDown
}
reorg := &SpendEvent{
Event: &SpendEvent_Reorg{Reorg: &Reorg{}},
}
if err := spendStream.Send(reorg); err != nil {
return err
}
// The spending transaction of the requests has confirmed
// on-chain and is no longer under the risk of being reorged out
// of the chain, so we can safely exit.
case _, ok := <-spendEvent.Done:
if !ok {
return chainntnfs.ErrChainNotifierShuttingDown
}
return nil
// The response stream's context for whatever reason has been
// closed. We'll return the error indicated by the context
// itself to the caller.
case <-spendStream.Context().Done():
return spendStream.Context().Err()
// The server has been requested to shut down.
case <-s.quit:
return ErrChainNotifierServerShuttingDown
}
}
}
// RegisterBlockEpochNtfn is a synchronous response-streaming RPC that registers
// an intent for a client to be notified of blocks in the chain. The stream will
// return a hash and height tuple of a block for each new/stale block in the
// chain. It is the client's responsibility to determine whether the tuple
// returned is for a new or stale block in the chain.
//
// A client can also request a historical backlog of blocks from a particular
// point. This allows clients to be idempotent by ensuring that they do not
// missing processing a single block within the chain.
//
// NOTE: This is part of the chainrpc.ChainNotifierService interface.
func (s *Server) RegisterBlockEpochNtfn(in *BlockEpoch,
epochStream ChainNotifier_RegisterBlockEpochNtfnServer) error {
// We'll start by reconstructing the RPC request into what the
// underlying ChainNotifier expects.
var hash chainhash.Hash
copy(hash[:], in.Hash)
// If the request isn't for a zero hash and a zero height, then we
// should deliver a backlog of notifications from the given block
// (hash/height tuple) until tip, and continue delivering epochs for
// new blocks.
var blockEpoch *chainntnfs.BlockEpoch
if hash != chainntnfs.ZeroHash && in.Height != 0 {
blockEpoch = &chainntnfs.BlockEpoch{
Hash: &hash,
Height: int32(in.Height),
}
}
epochEvent, err := s.cfg.ChainNotifier.RegisterBlockEpochNtfn(blockEpoch)
if err != nil {
return err
}
defer epochEvent.Cancel()
for {
select {
// A notification for a block has been received. This block can
// either be a new block or stale.
case blockEpoch, ok := <-epochEvent.Epochs:
if !ok {
return chainntnfs.ErrChainNotifierShuttingDown
}
epoch := &BlockEpoch{
Hash: blockEpoch.Hash[:],
Height: uint32(blockEpoch.Height),
}
if err := epochStream.Send(epoch); err != nil {
return err
}
// The response stream's context for whatever reason has been
// closed. We'll return the error indicated by the context
// itself to the caller.
case <-epochStream.Context().Done():
return epochStream.Context().Err()
// The server has been requested to shut down.
case <-s.quit:
return ErrChainNotifierServerShuttingDown
}
}
}