watchtower/server/server: server skeleton
This commit is contained in:
Conner Fromknecht
Conner Fromknecht
parent
fd6024c306
commit
73709530e3
611
watchtower/server/server.go
Normal file
611
watchtower/server/server.go
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@ -0,0 +1,611 @@
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package server
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import (
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"bytes"
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"errors"
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"fmt"
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"net"
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"sync"
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"sync/atomic"
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"time"
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"github.com/btcsuite/btcd/btcec"
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"github.com/btcsuite/btcd/connmgr"
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"github.com/btcsuite/btcutil"
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"github.com/lightningnetwork/lnd/lnwire"
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"github.com/lightningnetwork/lnd/watchtower/wtdb"
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"github.com/lightningnetwork/lnd/watchtower/wtwire"
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)
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var (
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// ErrPeerAlreadyConnected signals that a peer with the same session id
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// is already active within the server.
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ErrPeerAlreadyConnected = errors.New("peer already connected")
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)
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// Config abstracts the primary components and dependencies of the server.
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type Config struct {
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// DB provides persistent access to the server's sessions and for
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// storing state updates.
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DB DB
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// NodePrivKey is private key to be used in accepting new brontide
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// connections.
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NodePrivKey *btcec.PrivateKey
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// Listeners specifies which address to which clients may connect.
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Listeners []net.Listener
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// ReadTimeout specifies how long a client may go without sending a
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// message.
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ReadTimeout time.Duration
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// WriteTimeout specifies how long a client may go without reading a
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// message from the other end, if the connection has stopped buffering
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// the server's replies.
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WriteTimeout time.Duration
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// NewAddress is used to generate reward addresses, where a cut of
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// successfully sent funds can be received.
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NewAddress func() (btcutil.Address, error)
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}
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// Server houses the state required to handle watchtower peers. It's primary job
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// is to accept incoming connections, and dispatch processing of the client
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// message streams.
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type Server struct {
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started int32 // atomic
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shutdown int32 // atomic
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cfg *Config
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connMgr *connmgr.ConnManager
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clientMtx sync.RWMutex
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clients map[wtdb.SessionID]Peer
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globalFeatures *lnwire.RawFeatureVector
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localFeatures *lnwire.RawFeatureVector
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wg sync.WaitGroup
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quit chan struct{}
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}
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// New creates a new server to handle watchtower clients. The server will accept
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// clients connecting to the listener addresses, and allows them to open
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// sessions and send state updates.
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func New(cfg *Config) (*Server, error) {
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localFeatures := lnwire.NewRawFeatureVector(
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wtwire.WtSessionsOptional,
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)
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s := &Server{
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cfg: cfg,
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clients: make(map[wtdb.SessionID]Peer),
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globalFeatures: lnwire.NewRawFeatureVector(),
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localFeatures: localFeatures,
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quit: make(chan struct{}),
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}
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connMgr, err := connmgr.New(&connmgr.Config{
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Listeners: cfg.Listeners,
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OnAccept: s.inboundPeerConnected,
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Dial: noDial,
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})
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if err != nil {
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return nil, err
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}
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s.connMgr = connMgr
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return s, nil
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}
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// Start begins listening on the server's listeners.
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func (s *Server) Start() error {
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// Already running?
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if !atomic.CompareAndSwapInt32(&s.started, 0, 1) {
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return nil
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}
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s.connMgr.Start()
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return nil
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}
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// Stop shutdowns down the server's listeners and any active requests.
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func (s *Server) Stop() error {
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// Bail if we're already shutting down.
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if !atomic.CompareAndSwapInt32(&s.shutdown, 0, 1) {
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return nil
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}
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s.connMgr.Stop()
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close(s.quit)
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s.wg.Wait()
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return nil
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}
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// inboundPeerConnected is the callback given to the connection manager, and is
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// called each time a new connection is made to the watchtower. This method
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// proxies the new peers by filtering out those that do not satisfy the
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// server.Peer interface, and closes their connection. Successful connections
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// will be passed on to the public InboundPeerConnected method.
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func (s *Server) inboundPeerConnected(c net.Conn) {
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peer, ok := c.(Peer)
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if !ok {
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log.Warnf("incoming connection %T does not satisfy "+
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"server.Peer interface", c)
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c.Close()
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return
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}
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s.InboundPeerConnected(peer)
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}
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// InboundPeerConnected accepts a server.Peer, and handles the request submitted
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// by the client. This method serves also as a public endpoint for locally
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// registering new clients with the server.
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func (s *Server) InboundPeerConnected(peer Peer) {
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s.wg.Add(1)
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go s.handleClient(peer)
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}
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// handleClient processes a series watchtower messages sent by a client. The
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// client may either send:
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// * a single CreateSession message.
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// * a series of StateUpdate messages.
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//
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// This method uses the server's peer map to ensure at most one peer using the
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// same session id can enter the main event loop. The connection will be
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// dropped by the watchtower if no messages are sent or received by the
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// configured Read/WriteTimeouts.
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//
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// NOTE: This method MUST be run as a goroutine.
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func (s *Server) handleClient(peer Peer) {
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defer s.wg.Done()
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// Use the connection's remote pubkey as the client's session id.
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id := wtdb.NewSessionIDFromPubKey(peer.RemotePub())
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// Register this peer in the server's client map, and defer the
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// connection's cleanup. If the peer already exists, we will close the
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// connection and exit immediately.
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err := s.addPeer(&id, peer)
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if err != nil {
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peer.Close()
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return
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}
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defer s.removePeer(&id)
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msg, err := s.readMessage(peer)
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remoteInit, ok := msg.(*wtwire.Init)
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if !ok {
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log.Errorf("Client %s@%s did not send Init msg as first "+
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"message", id, peer.RemoteAddr())
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return
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}
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localInit := wtwire.NewInitMessage(
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s.localFeatures, s.globalFeatures,
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)
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err = s.sendMessage(peer, localInit)
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if err != nil {
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log.Errorf("Unable to send Init msg to %s: %v", id, err)
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return
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}
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if err = s.handleInit(localInit, remoteInit); err != nil {
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log.Errorf("Cannot support client %s: %v", id, err)
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return
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}
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// stateUpdateOnlyMode will become true if the client's first message is
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// a StateUpdate. If instead, it is a CreateSession, this method will exit
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// immediately after replying. We track this to ensure that the client
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// can't send a CreateSession after having already sent a StateUpdate.
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var stateUpdateOnlyMode bool
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for {
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select {
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case <-s.quit:
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return
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default:
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}
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nextMsg, err := s.readMessage(peer)
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if err != nil {
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log.Errorf("Unable to read watchtower msg from %x: %v",
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id[:], err)
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return
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}
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// Process the request according to the message's type.
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switch msg := nextMsg.(type) {
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// A CreateSession indicates a request to establish a new session
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// with our watchtower.
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case *wtwire.CreateSession:
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// Ensure CreateSession can only be sent as the first
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// message.
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if stateUpdateOnlyMode {
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log.Errorf("client %x sent CreateSession after "+
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"StateUpdate", id)
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return
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}
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log.Infof("Received CreateSession from %s, "+
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"version=%d nupdates=%d rewardrate=%d "+
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"sweepfeerate=%d", id, msg.BlobVersion,
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msg.MaxUpdates, msg.RewardRate,
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msg.SweepFeeRate)
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// Attempt to open a new session for this client.
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err := s.handleCreateSession(peer, &id, msg)
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if err != nil {
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log.Errorf("unable to handle CreateSession "+
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"from %s: %v", id, err)
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}
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// Exit after replying to CreateSession.
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return
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// A StateUpdate indicates an existing client attempting to
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// back-up a revoked commitment state.
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case *wtwire.StateUpdate:
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log.Infof("Received SessionUpdate from %s, seqnum=%d "+
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"lastapplied=%d complete=%v hint=%x", id,
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msg.SeqNum, msg.LastApplied, msg.IsComplete,
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msg.Hint[:])
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// Try to accept the state update from the client.
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err := s.handleStateUpdate(peer, &id, msg)
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if err != nil {
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log.Errorf("unable to handle StateUpdate "+
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"from %s: %v", id, err)
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return
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}
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// If the client signals that this is last StateUpdate
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// message, we can disconnect the client.
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if msg.IsComplete == 1 {
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return
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}
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// The client has signaled that more StateUpdates are
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// yet to come. Enter state-update-only mode to disallow
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// future sends of CreateSession messages.
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stateUpdateOnlyMode = true
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default:
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log.Errorf("received unsupported message type: %T "+
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"from %s", nextMsg, id)
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return
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}
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}
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}
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func (s *Server) handleInit(localInit, remoteInit *wtwire.Init) error {
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remoteLocalFeatures := lnwire.NewFeatureVector(
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remoteInit.LocalFeatures, wtwire.LocalFeatures,
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)
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remoteGlobalFeatures := lnwire.NewFeatureVector(
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remoteInit.GlobalFeatures, wtwire.GlobalFeatures,
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)
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unknownLocalFeatures := remoteLocalFeatures.UnknownRequiredFeatures()
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if len(unknownLocalFeatures) > 0 {
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err := fmt.Errorf("Peer set unknown local feature bits: %v",
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unknownLocalFeatures)
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return err
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}
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unknownGlobalFeatures := remoteGlobalFeatures.UnknownRequiredFeatures()
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if len(unknownGlobalFeatures) > 0 {
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err := fmt.Errorf("Peer set unknown global feature bits: %v",
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unknownGlobalFeatures)
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return err
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}
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return nil
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}
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func (s *Server) readMessage(peer Peer) (wtwire.Message, error) {
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// Set a read timeout to ensure we drop the client if not sent in a
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// timely manner.
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err := peer.SetReadDeadline(time.Now().Add(s.cfg.ReadTimeout))
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if err != nil {
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err = fmt.Errorf("unable to set read deadline: %v", err)
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return nil, err
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}
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// Pull the next message off the wire, and parse it according to the
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// watchtower wire specification.
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rawMsg, err := peer.ReadNextMessage()
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if err != nil {
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err = fmt.Errorf("unable to read message: %v", err)
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return nil, err
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}
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msgReader := bytes.NewReader(rawMsg)
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nextMsg, err := wtwire.ReadMessage(msgReader, 0)
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if err != nil {
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err = fmt.Errorf("unable to parse message: %v", err)
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return nil, err
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}
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return nextMsg, nil
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}
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// handleCreateSession processes a CreateSession message from the peer, and returns
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// a CreateSessionReply in response. This method will only succeed if no existing
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// session info is known about the session id. If an existing session is found,
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// the reward address is returned in case the client lost our reply.
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func (s *Server) handleCreateSession(peer Peer, id *wtdb.SessionID,
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init *wtwire.CreateSession) error {
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// TODO(conner): validate accept against policy
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// Query the db for session info belonging to the client's session id.
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existingInfo, err := s.cfg.DB.GetSessionInfo(id)
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switch {
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// We already have a session corresponding to this session id, return an
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// error signaling that it already exists in our database. We return the
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// reward address to the client in case they were not able to process
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// our reply earlier.
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case err == nil:
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log.Debugf("Already have session for %s", id)
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return s.replyCreateSession(
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peer, id, wtwire.CreateSessionCodeAlreadyExists,
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[]byte(existingInfo.RewardAddress),
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)
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// Some other database error occurred, return a temporary failure.
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case err != wtdb.ErrSessionNotFound:
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log.Errorf("unable to load session info for %s", id)
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return s.replyCreateSession(
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peer, id, wtwire.CodeTemporaryFailure, nil,
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)
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}
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// Now that we've established that this session does not exist in the
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// database, retrieve the sweep address that will be given to the
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// client. This address is to be included by the client when signing
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// sweep transactions destined for this tower, if its negotiated output
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// is not dust.
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rewardAddress, err := s.cfg.NewAddress()
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if err != nil {
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log.Errorf("unable to generate reward addr for %s", id)
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return s.replyCreateSession(
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peer, id, wtwire.CodeTemporaryFailure, nil,
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)
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}
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rewardAddrBytes := rewardAddress.ScriptAddress()
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// TODO(conner): create invoice for upfront payment
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// Assemble the session info using the agreed upon parameters, reward
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// address, and session id.
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info := wtdb.SessionInfo{
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ID: *id,
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Version: init.BlobVersion,
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MaxUpdates: init.MaxUpdates,
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RewardRate: init.RewardRate,
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SweepFeeRate: init.SweepFeeRate,
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RewardAddress: rewardAddrBytes,
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}
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// Insert the session info into the watchtower's database. If
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// successful, the session will now be ready for use.
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err = s.cfg.DB.InsertSessionInfo(&info)
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if err != nil {
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log.Errorf("unable to create session for %s", id)
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return s.replyCreateSession(
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peer, id, wtwire.CodeTemporaryFailure, nil,
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)
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}
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log.Infof("Accepted session for %s", id)
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return s.replyCreateSession(
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peer, id, wtwire.CodeOK, rewardAddrBytes,
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)
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}
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// handleStateUpdate processes a StateUpdate message request from a client. An
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// attempt will be made to insert the update into the db, where it is validated
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// against the client's session. The possible errors are then mapped back to
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// StateUpdateCodes specified by the watchtower wire protocol, and sent back
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// using a StateUpdateReply message.
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func (s *Server) handleStateUpdate(peer Peer, id *wtdb.SessionID,
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update *wtwire.StateUpdate) error {
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var (
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lastApplied uint16
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failCode wtwire.ErrorCode
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err error
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)
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sessionUpdate := wtdb.SessionStateUpdate{
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ID: *id,
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Hint: update.Hint,
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SeqNum: update.SeqNum,
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LastApplied: update.LastApplied,
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EncryptedBlob: update.EncryptedBlob,
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}
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lastApplied, err = s.cfg.DB.InsertStateUpdate(&sessionUpdate)
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switch {
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case err == nil:
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log.Infof("State update %d accepted for %s",
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update.SeqNum, id)
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failCode = wtwire.CodeOK
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// Return a permanent failure if a client tries to send an update for
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// which we have no session.
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case err == wtdb.ErrSessionNotFound:
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failCode = wtwire.CodePermanentFailure
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case err == wtdb.ErrSeqNumAlreadyApplied:
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failCode = wtwire.CodePermanentFailure
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// TODO(conner): remove session state for protocol
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// violation. Could also double as clean up method for
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// session-related state.
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case err == wtdb.ErrLastAppliedReversion:
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failCode = wtwire.StateUpdateCodeClientBehind
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case err == wtdb.ErrSessionConsumed:
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failCode = wtwire.StateUpdateCodeMaxUpdatesExceeded
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case err == wtdb.ErrUpdateOutOfOrder:
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failCode = wtwire.StateUpdateCodeSeqNumOutOfOrder
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default:
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failCode = wtwire.CodeTemporaryFailure
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}
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return s.replyStateUpdate(
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peer, id, failCode, lastApplied,
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)
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}
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// connFailure is a default error used when a request failed with a non-zero
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// error code.
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type connFailure struct {
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ID wtdb.SessionID
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Code uint16
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}
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// Error displays the SessionID and Code that caused the connection failure.
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func (f *connFailure) Error() string {
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return fmt.Sprintf("connection with %s failed with code=%v",
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f.ID, f.Code,
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)
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}
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// replyCreateSession sends a response to a CreateSession from a client. If the
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// status code in the reply is OK, the error from the write will be bubbled up.
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// Otherwise, this method returns a connection error to ensure we don't continue
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// communication with the client.
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func (s *Server) replyCreateSession(peer Peer, id *wtdb.SessionID,
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code wtwire.ErrorCode, data []byte) error {
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msg := &wtwire.CreateSessionReply{
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Code: code,
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Data: data,
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}
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err := s.sendMessage(peer, msg)
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if err != nil {
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log.Errorf("unable to send CreateSessionReply to %s", id)
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}
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|
||||
// Return the write error if the request succeeded.
|
||||
if code == wtwire.CodeOK {
|
||||
return err
|
||||
}
|
||||
|
||||
// Otherwise the request failed, return a connection failure to
|
||||
// disconnect the client.
|
||||
return &connFailure{
|
||||
ID: *id,
|
||||
Code: uint16(code),
|
||||
}
|
||||
}
|
||||
|
||||
// replyStateUpdate sends a response to a StateUpdate from a client. If the
|
||||
// status code in the reply is OK, the error from the write will be bubbled up.
|
||||
// Otherwise, this method returns a connection error to ensure we don't continue
|
||||
// communication with the client.
|
||||
func (s *Server) replyStateUpdate(peer Peer, id *wtdb.SessionID,
|
||||
code wtwire.StateUpdateCode, lastApplied uint16) error {
|
||||
|
||||
msg := &wtwire.StateUpdateReply{
|
||||
Code: code,
|
||||
LastApplied: lastApplied,
|
||||
}
|
||||
|
||||
err := s.sendMessage(peer, msg)
|
||||
if err != nil {
|
||||
log.Errorf("unable to send StateUpdateReply to %s", id)
|
||||
}
|
||||
|
||||
// Return the write error if the request succeeded.
|
||||
if code == wtwire.CodeOK {
|
||||
return err
|
||||
}
|
||||
|
||||
// Otherwise the request failed, return a connection failure to
|
||||
// disconnect the client.
|
||||
return &connFailure{
|
||||
ID: *id,
|
||||
Code: uint16(code),
|
||||
}
|
||||
}
|
||||
|
||||
// sendMessage sends a watchtower wire message to the target peer.
|
||||
func (s *Server) sendMessage(peer Peer, msg wtwire.Message) error {
|
||||
// TODO(conner): use buffer pool?
|
||||
|
||||
var b bytes.Buffer
|
||||
_, err := wtwire.WriteMessage(&b, msg, 0)
|
||||
if err != nil {
|
||||
err = fmt.Errorf("unable to encode msg: %v", err)
|
||||
return err
|
||||
}
|
||||
|
||||
err = peer.SetWriteDeadline(time.Now().Add(s.cfg.WriteTimeout))
|
||||
if err != nil {
|
||||
err = fmt.Errorf("unable to set write deadline: %v", err)
|
||||
return err
|
||||
}
|
||||
|
||||
_, err = peer.Write(b.Bytes())
|
||||
return err
|
||||
}
|
||||
|
||||
// addPeer stores a client in the server's client map. An error is returned if a
|
||||
// client with the same session id already exists.
|
||||
func (s *Server) addPeer(id *wtdb.SessionID, peer Peer) error {
|
||||
s.clientMtx.Lock()
|
||||
defer s.clientMtx.Unlock()
|
||||
|
||||
if existingPeer, ok := s.clients[*id]; ok {
|
||||
log.Infof("Already connected to peer %s@%s, disconnecting %s",
|
||||
id, existingPeer.RemoteAddr(), peer.RemoteAddr())
|
||||
return ErrPeerAlreadyConnected
|
||||
}
|
||||
s.clients[*id] = peer
|
||||
|
||||
log.Infof("Accepted incoming peer %s@%s",
|
||||
id, peer.RemoteAddr())
|
||||
|
||||
return nil
|
||||
}
|
||||
|
||||
// removePeer deletes a client from the server's client map. If a peer is found,
|
||||
// this method will close the peer's connection.
|
||||
func (s *Server) removePeer(id *wtdb.SessionID) {
|
||||
log.Infof("Releasing incoming peer %s", id)
|
||||
|
||||
s.clientMtx.Lock()
|
||||
peer, ok := s.clients[*id]
|
||||
delete(s.clients, *id)
|
||||
s.clientMtx.Unlock()
|
||||
|
||||
if ok {
|
||||
peer.Close()
|
||||
}
|
||||
}
|
||||
|
||||
// noDial is a dummy dial method passed to the server's connmgr.
|
||||
func noDial(_ net.Addr) (net.Conn, error) {
|
||||
return nil, fmt.Errorf("watchtower cannot make outgoing conns")
|
||||
}
|
||||
Loading…
Reference in New Issue
Block a user