Allow plugins to set a dual funding contribution (#2829)

We support dual funding, but we cannot decide for the node operator when
to contribute to channels that are being opened to us. Node operators
may want very different policies depending on their goals. Instead of
trying to figure out a general set of policies, we let plugins decide
when to contribute to channels and how much. Node operators are thus
free to implement whatever logic makes sense for them in a plugin.

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

@@ -67,7 +67,7 @@ case class InterceptOpenChannelReceived(replyTo: ActorRef[InterceptOpenChannelRe
 }
 
 sealed trait InterceptOpenChannelResponse
-case class AcceptOpenChannel(temporaryChannelId: ByteVector32, defaultParams: DefaultParams) extends InterceptOpenChannelResponse
+case class AcceptOpenChannel(temporaryChannelId: ByteVector32, defaultParams: DefaultParams, localFundingAmount_opt: Option[Satoshi]) extends InterceptOpenChannelResponse
 case class RejectOpenChannel(temporaryChannelId: ByteVector32, error: Error) extends InterceptOpenChannelResponse
 // @formatter:on
 

eclair-core/src/main/scala/fr/acinq/eclair/io/OpenChannelInterceptor.scala

@@ -167,7 +167,8 @@ private class OpenChannelInterceptor(peer: ActorRef[Any],
         nodeParams.pluginOpenChannelInterceptor match {
           case Some(plugin) => queryPlugin(plugin, request, localParams, ChannelConfig.standard, channelType)
           case None =>
-            peer ! SpawnChannelNonInitiator(request.open, ChannelConfig.standard, channelType, localParams, request.peerConnection.toClassic)
+            // NB: we don't add a contribution to the funding amount.
+            peer ! SpawnChannelNonInitiator(request.open, ChannelConfig.standard, channelType, localParams, None, request.peerConnection.toClassic)
             waitForRequest()
         }
       case PendingChannelsRateLimiterResponse(PendingChannelsRateLimiter.ChannelRateLimited) =>
@@ -186,7 +187,7 @@ private class OpenChannelInterceptor(peer: ActorRef[Any],
       receiveCommandMessage[QueryPluginCommands](context, "queryPlugin") {
         case PluginOpenChannelResponse(pluginResponse: AcceptOpenChannel) =>
           val localParams1 = updateLocalParams(localParams, pluginResponse.defaultParams)
-          peer ! SpawnChannelNonInitiator(request.open, channelConfig, channelType, localParams1, request.peerConnection.toClassic)
+          peer ! SpawnChannelNonInitiator(request.open, channelConfig, channelType, localParams1, pluginResponse.localFundingAmount_opt, request.peerConnection.toClassic)
           timers.cancel(PluginTimeout)
           waitForRequest()
         case PluginOpenChannelResponse(pluginResponse: RejectOpenChannel) =>

eclair-core/src/main/scala/fr/acinq/eclair/io/Peer.scala

@@ -199,7 +199,7 @@ class Peer(val nodeParams: NodeParams,
             stay()
         }
 
-      case Event(SpawnChannelNonInitiator(open, channelConfig, channelType, localParams, peerConnection), d: ConnectedData) =>
+      case Event(SpawnChannelNonInitiator(open, channelConfig, channelType, localParams, localFundingAmount_opt, peerConnection), d: ConnectedData) =>
         val temporaryChannelId = open.fold(_.temporaryChannelId, _.temporaryChannelId)
         if (peerConnection == d.peerConnection) {
           val channel = spawnChannel()
@@ -209,8 +209,7 @@ class Peer(val nodeParams: NodeParams,
               channel ! INPUT_INIT_CHANNEL_NON_INITIATOR(open.temporaryChannelId, None, dualFunded = false, None, localParams, d.peerConnection, d.remoteInit, channelConfig, channelType)
               channel ! open
             case Right(open) =>
-              // NB: we don't add a contribution to the funding amount.
-              channel ! INPUT_INIT_CHANNEL_NON_INITIATOR(open.temporaryChannelId, None, dualFunded = true, None, localParams, d.peerConnection, d.remoteInit, channelConfig, channelType)
+              channel ! INPUT_INIT_CHANNEL_NON_INITIATOR(open.temporaryChannelId, localFundingAmount_opt, dualFunded = true, None, localParams, d.peerConnection, d.remoteInit, channelConfig, channelType)
               channel ! open
           }
           stay() using d.copy(channels = d.channels + (TemporaryChannelId(temporaryChannelId) -> channel))
@@ -545,7 +544,7 @@ object Peer {
   }
 
   case class SpawnChannelInitiator(replyTo: akka.actor.typed.ActorRef[OpenChannelResponse], cmd: Peer.OpenChannel, channelConfig: ChannelConfig, channelType: SupportedChannelType, localParams: LocalParams)
-  case class SpawnChannelNonInitiator(open: Either[protocol.OpenChannel, protocol.OpenDualFundedChannel], channelConfig: ChannelConfig, channelType: SupportedChannelType, localParams: LocalParams, peerConnection: ActorRef)
+  case class SpawnChannelNonInitiator(open: Either[protocol.OpenChannel, protocol.OpenDualFundedChannel], channelConfig: ChannelConfig, channelType: SupportedChannelType, localParams: LocalParams, localFundingAmount_opt: Option[Satoshi], peerConnection: ActorRef)
 
   case class GetPeerInfo(replyTo: Option[typed.ActorRef[PeerInfoResponse]])
   sealed trait PeerInfoResponse { def nodeId: PublicKey }

eclair-core/src/test/scala/fr/acinq/eclair/io/OpenChannelInterceptorSpec.scala

@@ -87,13 +87,14 @@ class OpenChannelInterceptorSpec extends ScalaTestWithActorTestKit(ConfigFactory
     val openChannelNonInitiator = OpenChannelNonInitiator(remoteNodeId, Left(openChannel), Features.empty, Features.empty, peerConnection.ref, remoteAddress)
     openChannelInterceptor ! openChannelNonInitiator
     pendingChannelsRateLimiter.expectMessageType[AddOrRejectChannel].replyTo ! PendingChannelsRateLimiter.AcceptOpenChannel
-    pluginInterceptor.expectMessageType[InterceptOpenChannelReceived].replyTo ! AcceptOpenChannel(randomBytes32(), defaultParams)
-    val updatedLocalParams = peer.expectMessageType[SpawnChannelNonInitiator].localParams
-    assert(updatedLocalParams.dustLimit == defaultParams.dustLimit)
-    assert(updatedLocalParams.htlcMinimum == defaultParams.htlcMinimum)
-    assert(updatedLocalParams.maxAcceptedHtlcs == defaultParams.maxAcceptedHtlcs)
-    assert(updatedLocalParams.maxHtlcValueInFlightMsat == defaultParams.maxHtlcValueInFlightMsat)
-    assert(updatedLocalParams.toSelfDelay == defaultParams.toSelfDelay)
+    pluginInterceptor.expectMessageType[InterceptOpenChannelReceived].replyTo ! AcceptOpenChannel(randomBytes32(), defaultParams, Some(50_000 sat))
+    val response = peer.expectMessageType[SpawnChannelNonInitiator]
+    assert(response.localFundingAmount_opt.contains(50_000 sat))
+    assert(response.localParams.dustLimit == defaultParams.dustLimit)
+    assert(response.localParams.htlcMinimum == defaultParams.htlcMinimum)
+    assert(response.localParams.maxAcceptedHtlcs == defaultParams.maxAcceptedHtlcs)
+    assert(response.localParams.maxHtlcValueInFlightMsat == defaultParams.maxHtlcValueInFlightMsat)
+    assert(response.localParams.toSelfDelay == defaultParams.toSelfDelay)
   }
 
   test("continue channel open if no interceptor plugin registered and pending channels rate limiter accepts it") { f =>
@@ -146,7 +147,7 @@ class OpenChannelInterceptorSpec extends ScalaTestWithActorTestKit(ConfigFactory
     assert(peer.expectMessageType[OutgoingMessage].msg.asInstanceOf[Error].channelId == ByteVector32.One)
 
     // original request accepted after plugin accepts it
-    pluginInterceptor.expectMessageType[InterceptOpenChannelReceived].replyTo ! AcceptOpenChannel(randomBytes32(), defaultParams)
+    pluginInterceptor.expectMessageType[InterceptOpenChannelReceived].replyTo ! AcceptOpenChannel(randomBytes32(), defaultParams, None)
     assert(peer.expectMessageType[SpawnChannelNonInitiator].open == Left(openChannel))
     eventListener.expectMessageType[ChannelAborted]
   }

eclair-core/src/test/scala/fr/acinq/eclair/io/PeerSpec.scala

@@ -629,7 +629,7 @@ class PeerSpec extends FixtureSpec {
     val open = createOpenChannelMessage()
     system.eventStream.subscribe(probe.ref, classOf[ChannelAborted])
     connect(remoteNodeId, peer, peerConnection, switchboard)
-    peer ! SpawnChannelNonInitiator(Left(open), ChannelConfig.standard, ChannelTypes.Standard(), localParams, ActorRef.noSender)
+    peer ! SpawnChannelNonInitiator(Left(open), ChannelConfig.standard, ChannelTypes.Standard(), localParams, None, ActorRef.noSender)
     val channelAborted = probe.expectMsgType[ChannelAborted]
     assert(channelAborted.remoteNodeId == remoteNodeId)
     assert(channelAborted.channelId == open.temporaryChannelId)