lnd: add support for pushing funds as part of channel funding

This commit adds daemon level support for pushing funds as part of the
single funder channel workflow. This new feature allows the user to
open a channel and simultaneously make a channel at the same time which
can improve the UX when setting up a channel for the first time.

fundingmanager.go

@@ -348,8 +348,9 @@ func (f *fundingManager) handleFundingRequest(fmsg *fundingRequestMsg) {
 	delay := msg.CsvDelay
 
 	// TODO(roasbeef): error if funding flow already ongoing
-	fndgLog.Infof("Recv'd fundingRequest(amt=%v, delay=%v, pendingId=%v) "+
+	fndgLog.Infof("Recv'd fundingRequest(amt=%v, push=%v, delay=%v, pendingId=%v) "+
-		"from peerID(%v)", amt, delay, msg.ChannelID, fmsg.peer.id)
+		"from peerID(%v)", amt, msg.PushSatoshis, delay, msg.ChannelID,
+		fmsg.peer.id)
 
 	ourDustLimit := lnwallet.DefaultDustLimit()
 	theirDustlimit := msg.DustLimit
@@ -364,7 +365,7 @@ func (f *fundingManager) handleFundingRequest(fmsg *fundingRequestMsg) {
 	// port with default advertised port
 	reservation, err := f.wallet.InitChannelReservation(amt, 0,
 		fmsg.peer.addr.IdentityKey, fmsg.peer.addr.Address, 1, delay,
-		ourDustLimit)
+		ourDustLimit, msg.PushSatoshis)
 	if err != nil {
 		// TODO(roasbeef): push ErrorGeneric message
 		fndgLog.Errorf("Unable to initialize reservation: %v", err)
@@ -890,14 +891,15 @@ func (f *fundingManager) handleInitFundingMsg(msg *initFundingMsg) {
 
 	fndgLog.Infof("Initiating fundingRequest(localAmt=%v, remoteAmt=%v, "+
 		"capacity=%v, numConfs=%v, addr=%v, dustLimit=%v)", localAmt,
-		remoteAmt, ourDustLimit, capacity, numConfs,
+		msg.pushAmt, capacity, numConfs, msg.peer.addr.Address,
-		msg.peer.addr.Address)
+		ourDustLimit)
 
 	// Initialize a funding reservation with the local wallet. If the
 	// wallet doesn't have enough funds to commit to this channel, then
 	// the request will fail, and be aborted.
 	reservation, err := f.wallet.InitChannelReservation(capacity, localAmt,
-		nodeID, msg.peer.addr.Address, uint16(numConfs), 4, ourDustLimit)
+		nodeID, msg.peer.addr.Address, uint16(numConfs), 4,
+		ourDustLimit, msg.pushAmt)
 	if err != nil {
 		msg.err <- err
 		return
@@ -951,6 +953,7 @@ func (f *fundingManager) handleInitFundingMsg(msg *initFundingMsg) {
 		contribution.MultiSigKey,
 		deliveryScript,
 		ourDustLimit,
+		msg.pushAmt,
 	)
 	msg.peer.queueMsg(fundingReq, nil)
 }

rpcserver.go

@@ -233,10 +233,18 @@ func (r *rpcServer) OpenChannel(in *lnrpc.OpenChannelRequest,
 
 	rpcsLog.Tracef("[openchannel] request to peerid(%v) "+
 		"allocation(us=%v, them=%v) numconfs=%v", in.TargetPeerId,
-		in.LocalFundingAmount, in.RemoteFundingAmount, in.NumConfs)
+		in.LocalFundingAmount, in.PushSat, in.NumConfs)
 
 	localFundingAmt := btcutil.Amount(in.LocalFundingAmount)
-	remoteFundingAmt := btcutil.Amount(in.RemoteFundingAmount)
+	remoteInitialBalance := btcutil.Amount(in.PushSat)
+
+	// Ensure that the initial balance of the remote party (if pushing
+	// satoshis) does not execeed the amount the local party has requested
+	// for funding.
+	if remoteInitialBalance >= localFundingAmt {
+		return fmt.Errorf("amount pushed to remote peer for initial " +
+			"state must be below the local funding amount")
+	}
 
 	// TODO(roasbeef): make it optional
 	nodepubKey, err := btcec.ParsePubKey(in.NodePubkey, btcec.S256())
@@ -248,7 +256,7 @@ func (r *rpcServer) OpenChannel(in *lnrpc.OpenChannelRequest,
 	// open a new channel. A stream is returned in place, this stream will
 	// be used to consume updates of the state of the pending channel.
 	updateChan, errChan := r.server.OpenChannel(in.TargetPeerId,
-		nodepubKey, localFundingAmt, remoteFundingAmt, in.NumConfs)
+		nodepubKey, localFundingAmt, remoteInitialBalance, in.NumConfs)
 
 	var outpoint wire.OutPoint
 out:
@@ -257,7 +265,8 @@ out:
 		case err := <-errChan:
 			rpcsLog.Errorf("unable to open channel to "+
 				"identityPub(%x) nor peerID(%v): %v",
-				nodepubKey, in.TargetPeerId, err)
+				nodepubKey.SerializeCompressed(),
+				in.TargetPeerId, err)
 			return err
 		case fundingUpdate := <-updateChan:
 			rpcsLog.Tracef("[openchannel] sending update: %v",
@@ -299,7 +308,7 @@ func (r *rpcServer) OpenChannelSync(ctx context.Context,
 
 	rpcsLog.Tracef("[openchannel] request to peerid(%v) "+
 		"allocation(us=%v, them=%v) numconfs=%v", in.TargetPeerId,
-		in.LocalFundingAmount, in.RemoteFundingAmount, in.NumConfs)
+		in.LocalFundingAmount, in.PushSat, in.NumConfs)
 
 	// Decode the provided target node's public key, parsing it into a pub
 	// key object. For all sync call, byte slices are expected to be
@@ -314,10 +323,18 @@ func (r *rpcServer) OpenChannelSync(ctx context.Context,
 	}
 
 	localFundingAmt := btcutil.Amount(in.LocalFundingAmount)
-	remoteFundingAmt := btcutil.Amount(in.RemoteFundingAmount)
+	remoteInitialBalance := btcutil.Amount(in.PushSat)
+
+	// Ensure that the initial balance of the remote party (if pushing
+	// satoshis) does not execeed the amount the local party has requested
+	// for funding.
+	if remoteInitialBalance >= localFundingAmt {
+		return nil, fmt.Errorf("amount pushed to remote peer for " +
+			"initial state must be below the local funding amount")
+	}
 
 	updateChan, errChan := r.server.OpenChannel(in.TargetPeerId,
-		nodepubKey, localFundingAmt, remoteFundingAmt, in.NumConfs)
+		nodepubKey, localFundingAmt, remoteInitialBalance, in.NumConfs)
 
 	select {
 	// If an error occurs them immediately return the error to the client.

server.go

@@ -566,6 +566,8 @@ type openChanReq struct {
 	localFundingAmt  btcutil.Amount
 	remoteFundingAmt btcutil.Amount
 
+	pushAmt btcutil.Amount
+
 	numConfs uint32
 
 	updates chan *lnrpc.OpenStatusUpdate
@@ -777,20 +779,20 @@ func (s *server) ConnectToPeer(addr *lnwire.NetAddress) (int32, error) {
 // OpenChannel sends a request to the server to open a channel to the specified
 // peer identified by ID with the passed channel funding paramters.
 func (s *server) OpenChannel(peerID int32, nodeKey *btcec.PublicKey,
-	localAmt, remoteAmt btcutil.Amount,
+	localAmt, pushAmt btcutil.Amount,
 	numConfs uint32) (chan *lnrpc.OpenStatusUpdate, chan error) {
 
 	errChan := make(chan error, 1)
 	updateChan := make(chan *lnrpc.OpenStatusUpdate, 1)
 
 	req := &openChanReq{
-		targetPeerID:     peerID,
+		targetPeerID:    peerID,
-		targetPubkey:     nodeKey,
+		targetPubkey:    nodeKey,
-		localFundingAmt:  localAmt,
+		localFundingAmt: localAmt,
-		remoteFundingAmt: remoteAmt,
+		pushAmt:         pushAmt,
-		numConfs:         numConfs,
+		numConfs:        numConfs,
-		updates:          updateChan,
+		updates:         updateChan,
-		err:              errChan,
+		err:             errChan,
 	}
 
 	s.queries <- req