Update channel-type implementation to upstream spec as merged

Somehow, our channel type implementation doesn't echo back the
channel type as we believe it was negotiated, as we should. Though
the spec doesn't explicitly require this, some implementations may
require it and it appears to have been in the BOLTs from the start
of the channel type logic.

Author: TheBlueMatt

lightning/src/ln/channel.rs

@@ -1895,6 +1895,16 @@ impl<Signer: Sign> Channel<Signer> {
 			return Err(ChannelError::Close("Minimum confirmation depth must be at least 1".to_owned()));
 		}
 
+		if let Some(ty) = &msg.channel_type {
+			if *ty != self.channel_type {
+				return Err(ChannelError::Close("Channel Type in accept_channel didn't match the one sent in open_channel.".to_owned()));
+			}
+		} else if their_features.supports_channel_type() {
+			// Assume they've accepted the channel type as they said they understand it.
+		} else {
+			self.channel_type = ChannelTypeFeatures::from_counterparty_init(&their_features)
+		}
+
 		let counterparty_shutdown_scriptpubkey = if their_features.supports_upfront_shutdown_script() {
 			match &msg.shutdown_scriptpubkey {
 				&OptionalField::Present(ref script) => {
@@ -4720,6 +4730,7 @@ impl<Signer: Sign> Channel<Signer> {
 				Some(script) => script.clone().into_inner(),
 				None => Builder::new().into_script(),
 			}),
+			channel_type: Some(self.channel_type.clone()),
 		}
 	}
 

lightning/src/ln/msgs.rs

@@ -204,6 +204,12 @@ pub struct AcceptChannel {
 	pub first_per_commitment_point: PublicKey,
 	/// Optionally, a request to pre-set the to-sender output's scriptPubkey for when we collaboratively close
 	pub shutdown_scriptpubkey: OptionalField<Script>,
+	/// The channel type that this channel will represent. If none is set, we derive the channel
+	/// type from the intersection of our feature bits with our counterparty's feature bits from
+	/// the Init message.
+	///
+	/// This is required to match the equivalent field in [`OpenChannel::channel_type`].
+	pub channel_type: Option<ChannelTypeFeatures>,
 }
 
 /// A funding_created message to be sent or received from a peer
@@ -1064,7 +1070,9 @@ impl_writeable_msg!(AcceptChannel, {
 	htlc_basepoint,
 	first_per_commitment_point,
 	shutdown_scriptpubkey
-}, {});
+}, {
+	(1, channel_type, option),
+});
 
 impl_writeable_msg!(AnnouncementSignatures, {
 	channel_id,
@@ -2191,7 +2199,8 @@ mod tests {
 			delayed_payment_basepoint: pubkey_4,
 			htlc_basepoint: pubkey_5,
 			first_per_commitment_point: pubkey_6,
-			shutdown_scriptpubkey: if shutdown { OptionalField::Present(Address::p2pkh(&::bitcoin::PublicKey{compressed: true, key: pubkey_1}, Network::Testnet).script_pubkey()) } else { OptionalField::Absent }
+			shutdown_scriptpubkey: if shutdown { OptionalField::Present(Address::p2pkh(&::bitcoin::PublicKey{compressed: true, key: pubkey_1}, Network::Testnet).script_pubkey()) } else { OptionalField::Absent },
+			channel_type: None,
 		};
 		let encoded_value = accept_channel.encode();
 		let mut target_value = hex::decode("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").unwrap();