Replace usages of `Features::is_subset` and remove it

It turns out all the places we use `Features::is_subset` we could
as well be using `Features::requires_unknown_bits_from`. Further,
in the next commit `Features` will move to a different crate so any
methods which the `lightning` crate uses will need to be public. As
the `is_subset` API is prety confusing (it doesn't consider
optional/required bits, only whether the bits themselves are
strictly a subset) it'd be nice to not have to expose it, which is
enabled here.

diff --git a/lightning/src/chain/package.rs b/lightning/src/chain/package.rs
index b0dfca4c207018366c9beee09b8ab98cf383645e..361e12fa5634ce3ed38b3018fd122474420a0cef 100644 (file)
--- a/lightning/src/chain/package.rs
+++ b/lightning/src/chain/package.rs
@@ -93,7 +93,7 @@ pub(crate) fn verify_channel_type_features(channel_type_features: &Option<Channe
                        supported_feature_set |= additional_permitted_features;
                }
 
-               if !features.is_subset(&supported_feature_set) {
+               if features.requires_unknown_bits_from(&supported_feature_set) {
                        return Err(DecodeError::UnknownRequiredFeature);
                }
        }

diff --git a/lightning/src/ln/chan_utils.rs b/lightning/src/ln/chan_utils.rs
index 4d2572e895f1e12090877c233a740b771ba9daf4..8c811c920c0fadaa3434e8859073d097b9b9e1fe 100644 (file)
--- a/lightning/src/ln/chan_utils.rs
+++ b/lightning/src/ln/chan_utils.rs
@@ -772,10 +772,12 @@ pub(crate) fn legacy_deserialization_prevention_marker_for_channel_type_features
        legacy_version_bit_set.set_scid_privacy_required();
        legacy_version_bit_set.set_zero_conf_required();
 
-       if features.is_subset(&legacy_version_bit_set) {
-               None
-       } else {
+       debug_assert!(!legacy_version_bit_set.supports_any_optional_bits());
+       debug_assert!(!features.supports_any_optional_bits());
+       if features.requires_unknown_bits_from(&legacy_version_bit_set) {
                Some(())
+       } else {
+               None
        }
 }
 

diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index afd4e73578fad563999f8fd1bdd689d67ed2bbe1..7ba94998a0a4781a39a42304d560853cd4c04d8c 100644 (file)
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -1877,7 +1877,8 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
                }
 
                let channel_type = get_initial_channel_type(&config, their_features);
-               debug_assert!(channel_type.is_subset(&channelmanager::provided_channel_type_features(&config)));
+               debug_assert!(!channel_type.supports_any_optional_bits());
+               debug_assert!(!channel_type.requires_unknown_bits_from(&channelmanager::provided_channel_type_features(&config)));
 
                let (commitment_conf_target, anchor_outputs_value_msat)  = if channel_type.supports_anchors_zero_fee_htlc_tx() {
                        (ConfirmationTarget::AnchorChannelFee, ANCHOR_OUTPUT_VALUE_SATOSHI * 2 * 1000)
@@ -7967,7 +7968,7 @@ pub(super) fn channel_type_from_open_channel(
                        return Err(ChannelError::close("Channel Type was not understood - we require static remote key".to_owned()));
                }
                // Make sure we support all of the features behind the channel type.
-               if !channel_type.is_subset(our_supported_features) {
+               if channel_type.requires_unknown_bits_from(&our_supported_features) {
                        return Err(ChannelError::close("Channel Type contains unsupported features".to_owned()));
                }
                let announced_channel = if (common_fields.channel_flags & 1) == 1 { true } else { false };
@@ -9355,7 +9356,7 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, u32, &'c Ch
                }
 
                let chan_features = channel_type.as_ref().unwrap();
-               if !chan_features.is_subset(our_supported_features) {
+               if chan_features.supports_any_optional_bits() || chan_features.requires_unknown_bits_from(&our_supported_features) {
                        // If the channel was written by a new version and negotiated with features we don't
                        // understand yet, refuse to read it.
                        return Err(DecodeError::UnknownRequiredFeature);

diff --git a/lightning/src/ln/features.rs b/lightning/src/ln/features.rs
index 79bf871de7294ec951189c4524e60b119609e9ef..3b041cbc5c2b9783ee71f8a051ea8345cf2dc944 100644 (file)
--- a/lightning/src/ln/features.rs
+++ b/lightning/src/ln/features.rs
@@ -834,24 +834,6 @@ impl<T: sealed::Context> Features<T> {
                })
        }
 
-       // Returns true if the features within `self` are a subset of the features within `other`.
-       pub(crate) fn is_subset(&self, other: &Self) -> bool {
-               for (idx, byte) in self.flags.iter().enumerate() {
-                       if let Some(other_byte) = other.flags.get(idx) {
-                               if byte & other_byte != *byte {
-                                       // `self` has bits set that `other` doesn't.
-                                       return false;
-                               }
-                       } else {
-                               if *byte > 0 {
-                                       // `self` has a non-zero byte that `other` doesn't.
-                                       return false;
-                               }
-                       }
-               }
-               true
-       }
-
        /// Sets a required feature bit. Errors if `bit` is outside the feature range as defined
        /// by [BOLT 9].
        ///