Allow including routing hints when creating Bolt 11 invoice (#2909)

When nodes only have private channels, they must include routing hints
in their Bolt 11 invoices to be able to receive payments. We add a
parameter to the `createinvoice` RPC for this. Note that this may leak
the channel outpoint if `scid_alias` isn't used.

Fixes #2802

docs/release-notes/eclair-vnext.md

@@ -27,6 +27,7 @@ Eclair will not allow remote peers to open new obsolete channels that do not sup
 ### API changes
 
 - `channelstats` now takes optional parameters `--count` and `--skip` to control pagination. By default, it will return first 10 entries. (#2890)
+- `createinvoice` now takes an optional `--privateChannelIds` parameter that can be used to add routing hints through private channels. (#2909)
 
 ### Miscellaneous improvements and bug fixes
 

eclair-core/src/main/scala/fr/acinq/eclair/Eclair.scala

@@ -114,7 +114,7 @@ trait Eclair {
 
   def nodes(nodeIds_opt: Option[Set[PublicKey]] = None)(implicit timeout: Timeout): Future[Iterable[NodeAnnouncement]]
 
-  def receive(description: Either[String, ByteVector32], amount_opt: Option[MilliSatoshi], expire_opt: Option[Long], fallbackAddress_opt: Option[String], paymentPreimage_opt: Option[ByteVector32])(implicit timeout: Timeout): Future[Bolt11Invoice]
+  def receive(description: Either[String, ByteVector32], amount_opt: Option[MilliSatoshi], expire_opt: Option[Long], fallbackAddress_opt: Option[String], paymentPreimage_opt: Option[ByteVector32], privateChannelIds_opt: Option[List[ByteVector32]])(implicit timeout: Timeout): Future[Bolt11Invoice]
 
   def newAddress(): Future[String]
 
@@ -330,14 +330,28 @@ class EclairImpl(appKit: Kit) extends Eclair with Logging {
     }
   }
 
-  override def receive(description: Either[String, ByteVector32], amount_opt: Option[MilliSatoshi], expire_opt: Option[Long], fallbackAddress_opt: Option[String], paymentPreimage_opt: Option[ByteVector32])(implicit timeout: Timeout): Future[Bolt11Invoice] = {
+  override def receive(description: Either[String, ByteVector32], amount_opt: Option[MilliSatoshi], expire_opt: Option[Long], fallbackAddress_opt: Option[String], paymentPreimage_opt: Option[ByteVector32], privateChannelIds_opt: Option[List[ByteVector32]])(implicit timeout: Timeout): Future[Bolt11Invoice] = {
     fallbackAddress_opt.foreach { fa =>
+      // If it's not a valid bitcoin address we throw an exception.
       addressToPublicKeyScript(appKit.nodeParams.chainHash, fa) match {
         case Left(failure) => throw new IllegalArgumentException(failure.toString)
         case Right(_) => ()
       }
-    } // if it's not a bitcoin address throws an exception
-    appKit.paymentHandler.toTyped.ask(ref => ReceiveStandardPayment(ref, amount_opt, description, expire_opt, fallbackAddress_opt = fallbackAddress_opt, paymentPreimage_opt = paymentPreimage_opt))
+    }
+    for {
+      routingHints <- getInvoiceRoutingHints(privateChannelIds_opt)
+      invoice <- appKit.paymentHandler.toTyped.ask[Bolt11Invoice](ref => ReceiveStandardPayment(ref, amount_opt, description, expire_opt, routingHints, fallbackAddress_opt, paymentPreimage_opt))
+    } yield invoice
+  }
+
+  private def getInvoiceRoutingHints(privateChannelIds_opt: Option[List[ByteVector32]])(implicit timeout: Timeout): Future[List[List[Bolt11Invoice.ExtraHop]]] = {
+    privateChannelIds_opt match {
+      case Some(channelIds) =>
+        (appKit.router ? GetRouterData).mapTo[Router.Data].map {
+          d => channelIds.flatMap(cid => d.privateChannels.get(cid)).flatMap(_.toIncomingExtraHop).map(hop => hop :: Nil)
+        }
+      case None => Future.successful(Nil)
+    }
   }
 
   override def newAddress(): Future[String] = {

eclair-core/src/test/scala/fr/acinq/eclair/EclairImplSpec.scala

@@ -313,15 +313,15 @@ class EclairImplSpec extends TestKitBaseClass with FixtureAnyFunSuiteLike with I
 
     val fallBackAddressRaw = "muhtvdmsnbQEPFuEmxcChX58fGvXaaUoVt"
     val eclair = new EclairImpl(kit)
-    eclair.receive(Left("some desc"), Some(123 msat), Some(456), Some(fallBackAddressRaw), None)
+    eclair.receive(Left("some desc"), Some(123 msat), Some(456), Some(fallBackAddressRaw), None, None)
     val receive = paymentHandler.expectMsgType[ReceiveStandardPayment]
 
     assert(receive.amount_opt.contains(123 msat))
     assert(receive.expirySeconds_opt.contains(456))
     assert(receive.fallbackAddress_opt.contains(fallBackAddressRaw))
 
     // try with wrong address format
-    assertThrows[IllegalArgumentException](eclair.receive(Left("some desc"), Some(123 msat), Some(456), Some("wassa wassa"), None))
+    assertThrows[IllegalArgumentException](eclair.receive(Left("some desc"), Some(123 msat), Some(456), Some("wassa wassa"), None, None))
   }
 
   test("passing a payment_preimage to /createinvoice should result in an invoice with payment_hash=H(payment_preimage)") { f =>
@@ -331,7 +331,7 @@ class EclairImplSpec extends TestKitBaseClass with FixtureAnyFunSuiteLike with I
     val eclair = new EclairImpl(kitWithPaymentHandler)
     val paymentPreimage = randomBytes32()
 
-    eclair.receive(Left("some desc"), None, None, None, Some(paymentPreimage)).pipeTo(sender.ref)
+    eclair.receive(Left("some desc"), None, None, None, Some(paymentPreimage), None).pipeTo(sender.ref)
     assert(sender.expectMsgType[Invoice].paymentHash == Crypto.sha256(paymentPreimage))
   }
 

eclair-node/src/main/scala/fr/acinq/eclair/api/handlers/Invoice.scala

@@ -18,6 +18,7 @@ package fr.acinq.eclair.api.handlers
 
 import akka.http.scaladsl.server.Route
 import fr.acinq.bitcoin.scalacompat.ByteVector32
+import fr.acinq.bitcoin.scalacompat.Crypto.PublicKey
 import fr.acinq.eclair.api.Service
 import fr.acinq.eclair.api.directives.EclairDirectives
 import fr.acinq.eclair.api.serde.FormParamExtractors._
@@ -28,9 +29,9 @@ trait Invoice {
   import fr.acinq.eclair.api.serde.JsonSupport.{formats, marshaller, serialization}
 
   val createInvoice: Route = postRequest("createinvoice") { implicit t =>
-    formFields("description".as[String].?, "descriptionHash".as[ByteVector32].?, amountMsatFormParam.?, "expireIn".as[Long].?, "fallbackAddress".as[String].?, "paymentPreimage".as[ByteVector32](bytes32Unmarshaller).?) {
-      case (Some(desc), None, amountMsat, expire, fallBackAddress, paymentPreimage_opt) => complete(eclairApi.receive(Left(desc), amountMsat, expire, fallBackAddress, paymentPreimage_opt))
-      case (None, Some(desc), amountMsat, expire, fallBackAddress, paymentPreimage_opt) => complete(eclairApi.receive(Right(desc), amountMsat, expire, fallBackAddress, paymentPreimage_opt))
+    formFields("description".as[String].?, "descriptionHash".as[ByteVector32].?, amountMsatFormParam.?, "expireIn".as[Long].?, "fallbackAddress".as[String].?, "paymentPreimage".as[ByteVector32](bytes32Unmarshaller).?, "privateChannelIds".as[List[ByteVector32]](bytes32ListUnmarshaller).?) {
+      case (Some(desc), None, amountMsat, expire, fallBackAddress, paymentPreimage_opt, privateChannelIds_opt) => complete(eclairApi.receive(Left(desc), amountMsat, expire, fallBackAddress, paymentPreimage_opt, privateChannelIds_opt))
+      case (None, Some(desc), amountMsat, expire, fallBackAddress, paymentPreimage_opt, privateChannelIds_opt) => complete(eclairApi.receive(Right(desc), amountMsat, expire, fallBackAddress, paymentPreimage_opt, privateChannelIds_opt))
       case _ => failWith(new RuntimeException("Either 'description' (string) or 'descriptionHash' (sha256 hash of description string) must be supplied"))
     }
   }