Add support for option_payment_metadata (#313)

* Filter init, node and invoice features

We should explicitly filter features based on where they can be included
(`init`, `node_announcement` or `invoice`) as specified in Bolt 9.

We also introduce the option_payment_metadata feature which helps our
test cases since it's only allowed in invoices.

* Refactor onion to dedicated namespace

This commit doesn't contain any logic, it simply prefixes some classes
to make it obvious that they are payment-related, rename files and
moves some classes.

We will update the payment onion, so it was a good time to do this small
refactoring which will also be necessary for onion messages.

* Add support for option_payment_metadata

Add support for lightning/bolts#912

Whenever we find a payment metadata field in an invoice, we send it in
the onion payload for the final recipient.

We include a payment metadata in every invoice we generate. This lets us
see whether our payers support it or not, which is important data to have
before we make it mandatory and use it for storage-less invoices.

lightning-kmp-test-fixtures/src/commonMain/kotlin/fr/acinq/lightning/tests/TestConstants.kt

@@ -54,6 +54,7 @@ object TestConstants {
                 Feature.StaticRemoteKey to FeatureSupport.Mandatory,
                 Feature.AnchorOutputs to FeatureSupport.Mandatory,
                 Feature.ChannelType to FeatureSupport.Mandatory,
+                Feature.PaymentMetadata to FeatureSupport.Optional,
                 Feature.TrampolinePayment to FeatureSupport.Optional,
                 Feature.WakeUpNotificationProvider to FeatureSupport.Optional,
                 Feature.PayToOpenProvider to FeatureSupport.Optional,
@@ -129,6 +130,7 @@ object TestConstants {
                 Feature.StaticRemoteKey to FeatureSupport.Mandatory,
                 Feature.AnchorOutputs to FeatureSupport.Mandatory,
                 Feature.ChannelType to FeatureSupport.Mandatory,
+                Feature.PaymentMetadata to FeatureSupport.Optional,
                 Feature.TrampolinePayment to FeatureSupport.Optional,
                 Feature.WakeUpNotificationClient to FeatureSupport.Optional,
                 Feature.PayToOpenClient to FeatureSupport.Optional,

lightning-kmp-test-fixtures/src/commonMain/kotlin/fr/acinq/lightning/tests/io/peer/builders.kt

@@ -65,9 +65,9 @@ public suspend fun newPeers(
     }
 
     // Initialize Bob with Alice's features
-    bob.send(BytesReceived(LightningMessage.encode(Init(features = nodeParams.first.features.toByteArray().toByteVector()))))
+    bob.send(BytesReceived(LightningMessage.encode(Init(features = nodeParams.first.features.initFeatures().toByteArray().toByteVector()))))
     // Initialize Alice with Bob's features
-    alice.send(BytesReceived(LightningMessage.encode(Init(features = nodeParams.second.features.toByteArray().toByteVector()))))
+    alice.send(BytesReceived(LightningMessage.encode(Init(features = nodeParams.second.features.initFeatures().toByteArray().toByteVector()))))
 
     // TODO update to depend on the initChannels size
     if (initChannels.isNotEmpty()) {
@@ -124,7 +124,7 @@ public suspend fun CoroutineScope.newPeer(
 
     remotedNodeChannelState?.let { state ->
         // send Init from remote node
-        val theirInit = Init(features = state.staticParams.nodeParams.features.toByteArray().toByteVector())
+        val theirInit = Init(features = state.staticParams.nodeParams.features.initFeatures().toByteArray().toByteVector())
 
         val initMsg = LightningMessage.encode(theirInit)
         peer.send(BytesReceived(initMsg))

src/commonMain/kotlin/fr/acinq/lightning/Features.kt

@@ -6,6 +6,9 @@ import fr.acinq.lightning.utils.leftPaddedCopyOf
 import fr.acinq.lightning.utils.or
 import kotlinx.serialization.Serializable
 
+/** Feature scope as defined in Bolt 9. */
+enum class FeatureScope { Init, Node, Invoice }
+
 enum class FeatureSupport {
     Mandatory {
         override fun toString() = "mandatory"
@@ -20,6 +23,7 @@ sealed class Feature {
 
     abstract val rfcName: String
     abstract val mandatory: Int
+    abstract val scopes: Set<FeatureScope>
     val optional: Int get() = mandatory + 1
 
     fun supportBit(support: FeatureSupport): Int = when (support) {
@@ -33,6 +37,7 @@ sealed class Feature {
     object OptionDataLossProtect : Feature() {
         override val rfcName get() = "option_data_loss_protect"
         override val mandatory get() = 0
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
     @Serializable
@@ -41,66 +46,84 @@ sealed class Feature {
 
         // reserved but not used as per lightningnetwork/lightning-rfc/pull/178
         override val mandatory get() = 2
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init)
     }
 
     @Serializable
     object ChannelRangeQueries : Feature() {
         override val rfcName get() = "gossip_queries"
         override val mandatory get() = 6
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
     @Serializable
     object VariableLengthOnion : Feature() {
         override val rfcName get() = "var_onion_optin"
         override val mandatory get() = 8
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node, FeatureScope.Invoice)
     }
 
     @Serializable
     object ChannelRangeQueriesExtended : Feature() {
         override val rfcName get() = "gossip_queries_ex"
         override val mandatory get() = 10
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
     @Serializable
     object StaticRemoteKey : Feature() {
         override val rfcName get() = "option_static_remotekey"
         override val mandatory get() = 12
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
     @Serializable
     object PaymentSecret : Feature() {
         override val rfcName get() = "payment_secret"
         override val mandatory get() = 14
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node, FeatureScope.Invoice)
     }
 
     @Serializable
     object BasicMultiPartPayment : Feature() {
         override val rfcName get() = "basic_mpp"
         override val mandatory get() = 16
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node, FeatureScope.Invoice)
     }
 
     @Serializable
     object Wumbo : Feature() {
         override val rfcName get() = "option_support_large_channel"
         override val mandatory get() = 18
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
     @Serializable
     object AnchorOutputs : Feature() {
         override val rfcName get() = "option_anchor_outputs"
         override val mandatory get() = 20
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
     @Serializable
     object ShutdownAnySegwit : Feature() {
         override val rfcName get() = "option_shutdown_anysegwit"
         override val mandatory get() = 26
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
     @Serializable
     object ChannelType : Feature() {
         override val rfcName get() = "option_channel_type"
         override val mandatory get() = 44
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
+    }
+
+    @Serializable
+    object PaymentMetadata : Feature() {
+        override val rfcName get() = "option_payment_metadata"
+        override val mandatory get() = 48
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Invoice)
     }
 
     // The following features have not been standardised, hence the high feature bits to avoid conflicts.
@@ -109,76 +132,87 @@ sealed class Feature {
     object TrampolinePayment : Feature() {
         override val rfcName get() = "trampoline_payment"
         override val mandatory get() = 50
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node, FeatureScope.Invoice)
     }
 
     /** This feature bit should be activated when a node accepts having their channel reserve set to 0. */
     @Serializable
     object ZeroReserveChannels : Feature() {
         override val rfcName get() = "zero_reserve_channels"
         override val mandatory get() = 128
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
     /** This feature bit should be activated when a node accepts unconfirmed channels (will set min_depth to 0 in accept_channel). */
     @Serializable
     object ZeroConfChannels : Feature() {
         override val rfcName get() = "zero_conf_channels"
         override val mandatory get() = 130
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
     /** This feature bit should be activated when a mobile node supports waking up via push notifications. */
     @Serializable
     object WakeUpNotificationClient : Feature() {
         override val rfcName get() = "wake_up_notification_client"
         override val mandatory get() = 132
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init)
     }
 
     /** This feature bit should be activated when a node supports waking up their peers via push notifications. */
     @Serializable
     object WakeUpNotificationProvider : Feature() {
         override val rfcName get() = "wake_up_notification_provider"
         override val mandatory get() = 134
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
     /** This feature bit should be activated when a node accepts on-the-fly channel creation. */
     @Serializable
     object PayToOpenClient : Feature() {
         override val rfcName get() = "pay_to_open_client"
         override val mandatory get() = 136
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init)
     }
 
     /** This feature bit should be activated when a node supports opening channels on-the-fly when liquidity is missing to receive a payment. */
     @Serializable
     object PayToOpenProvider : Feature() {
         override val rfcName get() = "pay_to_open_provider"
         override val mandatory get() = 138
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
     /** This feature bit should be activated when a node accepts channel creation via trusted swaps-in. */
     @Serializable
     object TrustedSwapInClient : Feature() {
         override val rfcName get() = "trusted_swap_in_client"
         override val mandatory get() = 140
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init)
     }
 
     /** This feature bit should be activated when a node supports opening channels in exchange for on-chain funds (swap-in). */
     @Serializable
     object TrustedSwapInProvider : Feature() {
         override val rfcName get() = "trusted_swap_in_provider"
         override val mandatory get() = 142
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 
     /** This feature bit should be activated when a node wants to send channel backups to their peers. */
     @Serializable
     object ChannelBackupClient : Feature() {
         override val rfcName get() = "channel_backup_client"
         override val mandatory get() = 144
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init)
     }
 
     /** This feature bit should be activated when a node stores channel backups for their peers. */
     @Serializable
     object ChannelBackupProvider : Feature() {
         override val rfcName get() = "channel_backup_provider"
         override val mandatory get() = 146
+        override val scopes: Set<FeatureScope> get() = setOf(FeatureScope.Init, FeatureScope.Node)
     }
 }
 
@@ -188,9 +222,16 @@ data class UnknownFeature(val bitIndex: Int)
 @Serializable
 data class Features(val activated: Map<Feature, FeatureSupport>, val unknown: Set<UnknownFeature> = emptySet()) {
 
-    fun hasFeature(feature: Feature, support: FeatureSupport? = null): Boolean =
-        if (support != null) activated[feature] == support
-        else activated.containsKey(feature)
+    fun hasFeature(feature: Feature, support: FeatureSupport? = null): Boolean = when (support) {
+        null -> activated.containsKey(feature)
+        else -> activated[feature] == support
+    }
+
+    fun initFeatures(): Features = Features(activated.filter { it.key.scopes.contains(FeatureScope.Init) }, unknown)
+
+    fun nodeAnnouncementFeatures(): Features = Features(activated.filter { it.key.scopes.contains(FeatureScope.Node) }, unknown)
+
+    fun invoiceFeatures(): Features = Features(activated.filter { it.key.scopes.contains(FeatureScope.Invoice) }, unknown)
 
     /** NB: this method is not reflexive, see [[Features.areCompatible]] if you want symmetric validation. */
     fun areSupported(remoteFeatures: Features): Boolean {
@@ -236,6 +277,7 @@ data class Features(val activated: Map<Feature, FeatureSupport>, val unknown: Se
             Feature.AnchorOutputs,
             Feature.ShutdownAnySegwit,
             Feature.ChannelType,
+            Feature.PaymentMetadata,
             Feature.TrampolinePayment,
             Feature.ZeroReserveChannels,
             Feature.ZeroConfChannels,

src/commonMain/kotlin/fr/acinq/lightning/channel/Commitments.kt

@@ -11,7 +11,7 @@ import fr.acinq.lightning.blockchain.fee.FeerateTolerance
 import fr.acinq.lightning.crypto.Generators
 import fr.acinq.lightning.crypto.KeyManager
 import fr.acinq.lightning.crypto.ShaChain
-import fr.acinq.lightning.payment.OutgoingPacket
+import fr.acinq.lightning.payment.OutgoingPaymentPacket
 import fr.acinq.lightning.transactions.CommitmentSpec
 import fr.acinq.lightning.transactions.Transactions
 import fr.acinq.lightning.transactions.Transactions.TransactionWithInputInfo.CommitTx
@@ -370,7 +370,7 @@ data class Commitments(
             // we have already sent a fail/fulfill for this htlc
             alreadyProposed(localChanges.proposed, htlc.id) -> Either.Left(UnknownHtlcId(channelId, cmd.id))
             else -> {
-                when (val result = OutgoingPacket.buildHtlcFailure(nodeSecret, htlc.paymentHash, htlc.onionRoutingPacket, cmd.reason)) {
+                when (val result = OutgoingPaymentPacket.buildHtlcFailure(nodeSecret, htlc.paymentHash, htlc.onionRoutingPacket, cmd.reason)) {
                     is Either.Right -> {
                         val fail = UpdateFailHtlc(channelId, cmd.id, result.value)
                         val commitments1 = addLocalProposal(fail)

src/commonMain/kotlin/fr/acinq/lightning/io/Peer.kt

@@ -115,7 +115,7 @@ class Peer(
 
     private val features = nodeParams.features
 
-    private val ourInit = Init(features.toByteArray().toByteVector())
+    private val ourInit = Init(features.initFeatures().toByteArray().toByteVector())
     private var theirInit: Init? = null
 
     public val currentTipFlow = MutableStateFlow<Pair<Int, BlockHeader>?>(null)