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.

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.