do dry runs in planning stage to estimate size of all sends

endpoint/endpoint.go

@@ -75,16 +75,19 @@ func (p *Sender) Send(ctx context.Context, r *pdu.SendReq) (*pdu.SendRes, io.Rea
 		return nil, nil, replication.NewFilteredError(r.Filesystem)
 	}
 
-	size, err := zfs.ZFSSendDry(r.Filesystem, r.From, r.To)
-	if err != nil {
-		return nil, nil, err
+	if r.DryRun {
+		size, err := zfs.ZFSSendDry(r.Filesystem, r.From, r.To)
+		if err != nil {
+			return nil, nil, err
+		}
+		return &pdu.SendRes{ExpectedSize: size}, nil, nil
+	} else {
+		stream, err := zfs.ZFSSend(r.Filesystem, r.From, r.To)
+		if err != nil {
+			return nil, nil, err
+		}
+		return &pdu.SendRes{}, stream, nil
 	}
-
-	stream, err := zfs.ZFSSend(r.Filesystem, r.From, r.To)
-	if err != nil {
-		return nil, nil, err
-	}
-	return &pdu.SendRes{ExpectedSize: size}, stream, nil
 }
 
 func (p *Sender) DestroySnapshots(ctx context.Context, req *pdu.DestroySnapshotsReq) (*pdu.DestroySnapshotsRes, error) {