commit cbdf43150a9671a42cb301fd9741b76f93f27762
parent b27c6d22774529f6ef56fa2e311ee4df76968562
Author: Jared Tobin <jared@jtobin.io>
Date: Sun, 25 Jan 2026 15:54:32 +0400
Merge impl/table: known features table
Adds lib/Lightning/Protocol/BOLT9/Features.hs with:
- Feature record type (name, baseBit, contexts, dependencies, assumed)
- Complete table of 22 features from BOLT #9 spec
- featureByBit and featureByName lookup functions
- knownFeatures list
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Diffstat:
2 files changed, 109 insertions(+), 0 deletions(-)
diff --git a/lib/Lightning/Protocol/BOLT9/Features.hs b/lib/Lightning/Protocol/BOLT9/Features.hs
@@ -0,0 +1,108 @@
+{-# OPTIONS_HADDOCK prune #-}
+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE DeriveGeneric #-}
+
+-- |
+-- Module: Lightning.Protocol.BOLT9.Features
+-- Copyright: (c) 2025 Jared Tobin
+-- License: MIT
+-- Maintainer: Jared Tobin <jared@ppad.tech>
+--
+-- Known feature table for the Lightning Network, per
+-- [BOLT #9](https://github.com/lightning/bolts/blob/master/09-features.md).
+
+module Lightning.Protocol.BOLT9.Features (
+ -- * Context
+ Context(..)
+
+ -- * Feature
+ , Feature(..)
+
+ -- * Lookup
+ , featureByBit
+ , featureByName
+
+ -- * Known features table
+ , knownFeatures
+ ) where
+
+import Control.DeepSeq (NFData)
+import Data.List (find)
+import Data.Word (Word16)
+import GHC.Generics (Generic)
+
+-- | Contexts in which a feature may be presented.
+data Context
+ = Init -- ^ 'I': presented in the @init@ message.
+ | NodeAnnouncement -- ^ 'N': presented in @node_announcement@ messages.
+ | ChannelAnnouncement
+ -- ^ 'C': presented in @channel_announcement@ messages.
+ | Invoice -- ^ '9': presented in BOLT 11 invoices.
+ | BlindedPath -- ^ 'B': presented in @allowed_features@ of a
+ -- blinded path.
+ | ChannelType -- ^ 'T': used in @channel_type@ field when opening
+ -- channels.
+ deriving (Eq, Ord, Show, Generic)
+
+instance NFData Context
+
+-- | A known feature from the BOLT #9 specification.
+data Feature = Feature {
+ featureName :: !String
+ -- ^ The canonical name of the feature.
+ , featureBaseBit :: {-# UNPACK #-} !Word16
+ -- ^ The even (compulsory) bit number; the odd (optional) bit is
+ -- @baseBit + 1@.
+ , featureContexts :: ![Context]
+ -- ^ Contexts in which this feature may be presented.
+ , featureDependencies :: ![String]
+ -- ^ Names of features this feature depends on.
+ , featureAssumed :: !Bool
+ -- ^ Whether this feature is assumed to be universally supported.
+ }
+ deriving (Eq, Show, Generic)
+
+instance NFData Feature
+
+-- | The complete table of known features from BOLT #9.
+knownFeatures :: [Feature]
+knownFeatures = [
+ Feature "option_data_loss_protect" 0 [] [] True
+ , Feature "option_upfront_shutdown_script" 4 [Init, NodeAnnouncement] [] False
+ , Feature "gossip_queries" 6 [] [] False
+ , Feature "var_onion_optin" 8 [] [] True
+ , Feature "gossip_queries_ex" 10 [Init, NodeAnnouncement] [] False
+ , Feature "option_static_remotekey" 12 [] [] True
+ , Feature "payment_secret" 14 [] [] True
+ , Feature "basic_mpp" 16 [Init, NodeAnnouncement, Invoice]
+ ["payment_secret"] False
+ , Feature "option_support_large_channel" 18 [Init, NodeAnnouncement] [] False
+ , Feature "option_anchors" 22 [Init, NodeAnnouncement, ChannelType] [] False
+ , Feature "option_route_blinding" 24 [Init, NodeAnnouncement, Invoice] [] False
+ , Feature "option_shutdown_anysegwit" 26 [Init, NodeAnnouncement] [] False
+ , Feature "option_dual_fund" 28 [Init, NodeAnnouncement] [] False
+ , Feature "option_quiesce" 34 [Init, NodeAnnouncement] [] False
+ , Feature "option_attribution_data" 36 [Init, NodeAnnouncement, Invoice]
+ [] False
+ , Feature "option_onion_messages" 38 [Init, NodeAnnouncement] [] False
+ , Feature "option_provide_storage" 42 [Init, NodeAnnouncement] [] False
+ , Feature "option_channel_type" 44 [] [] True
+ , Feature "option_scid_alias" 46 [Init, NodeAnnouncement, ChannelType] [] False
+ , Feature "option_payment_metadata" 48 [Invoice] [] False
+ , Feature "option_zeroconf" 50 [Init, NodeAnnouncement, ChannelType]
+ ["option_scid_alias"] False
+ , Feature "option_simple_close" 60 [Init, NodeAnnouncement]
+ ["option_shutdown_anysegwit"] False
+ ]
+
+-- | Look up a feature by bit number.
+--
+-- Accepts either the even (compulsory) or odd (optional) bit of the pair.
+featureByBit :: Word16 -> Maybe Feature
+featureByBit !bit =
+ let baseBit = bit - (bit `mod` 2) -- round down to even
+ in find (\f -> featureBaseBit f == baseBit) knownFeatures
+
+-- | Look up a feature by its canonical name.
+featureByName :: String -> Maybe Feature
+featureByName !name = find (\f -> featureName f == name) knownFeatures
diff --git a/ppad-bolt9.cabal b/ppad-bolt9.cabal
@@ -25,6 +25,7 @@ library
-Wall
exposed-modules:
Lightning.Protocol.BOLT9
+ Lightning.Protocol.BOLT9.Features
Lightning.Protocol.BOLT9.Types
build-depends:
base >= 4.9 && < 5
