Default to anchor channels

Set `negotiate_anchors_zero_fee_htlc_tx` default
to true.

Author: elnosh

fuzz/src/chanmon_consistency.rs

@@ -710,8 +710,8 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 			config.channel_config.forwarding_fee_proportional_millionths = 0;
 			config.channel_handshake_config.announce_for_forwarding = true;
 			config.reject_inbound_splices = false;
-			if anchors {
-				config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = true;
+			if !anchors {
+				config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = false;
 			}
 			let network = Network::Bitcoin;
 			let best_block_timestamp = genesis_block(network).header.time;
@@ -760,8 +760,8 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 		config.channel_config.forwarding_fee_proportional_millionths = 0;
 		config.channel_handshake_config.announce_for_forwarding = true;
 		config.reject_inbound_splices = false;
-		if anchors {
-			config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = true;
+		if !anchors {
+			config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = false;
 		}
 
 		let mut monitors = new_hash_map();

lightning-background-processor/src/lib.rs

@@ -2447,6 +2447,8 @@ mod tests {
 			));
 			let best_block = BestBlock::from_network(network);
 			let params = ChainParameters { network, best_block };
+			let mut config = UserConfig::default();
+			config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = false;
 			let manager = Arc::new(ChannelManager::new(
 				Arc::clone(&fee_estimator),
 				Arc::clone(&chain_monitor),
@@ -2457,7 +2459,7 @@ mod tests {
 				Arc::clone(&keys_manager),
 				Arc::clone(&keys_manager),
 				Arc::clone(&keys_manager),
-				UserConfig::default(),
+				config,
 				params,
 				genesis_block.header.time,
 			));

lightning/src/ln/channel.rs

@@ -16026,7 +16026,8 @@ mod tests {
 
 		// Create Node A's channel pointing to Node B's pubkey
 		let node_b_node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
-		let config = UserConfig::default();
+		let mut config = UserConfig::default();
+		config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = false;
 		let mut node_a_chan = OutboundV1Channel::<&TestKeysInterface>::new(&feeest, &&keys_provider, &&keys_provider, node_b_node_id, &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42, None, &logger).unwrap();
 
 		// Create Node B's channel by receiving Node A's open_channel message
@@ -16116,7 +16117,8 @@ mod tests {
 		let logger = TestLogger::new();
 
 		let node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
-		let config = UserConfig::default();
+		let mut config = UserConfig::default();
+		config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = false;
 		let mut chan = OutboundV1Channel::<&TestKeysInterface>::new(&fee_est, &&keys_provider, &&keys_provider, node_id, &channelmanager::provided_init_features(&config), 10000000, 100000, 42, &config, 0, 42, None, &logger).unwrap();
 
 		let commitment_tx_fee_0_htlcs = commit_tx_fee_sat(chan.context.feerate_per_kw, 0, chan.funding.get_channel_type()) * 1000;

lightning/src/ln/channel_open_tests.rs

@@ -172,8 +172,7 @@ fn test_0conf_limiting() {
 
 #[test]
 fn test_inbound_anchors_manual_acceptance() {
-	let mut anchors_cfg = test_default_channel_config();
-	anchors_cfg.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = true;
+	let anchors_cfg = test_default_anchors_channel_config();
 	do_test_manual_inbound_accept_with_override(anchors_cfg, None);
 }
 
@@ -191,9 +190,7 @@ fn test_inbound_anchors_config_overridden() {
 		update_overrides: None,
 	};
 
-	let mut anchors_cfg = test_default_channel_config();
-	anchors_cfg.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = true;
-
+	let mut anchors_cfg = test_default_anchors_channel_config();
 	let accept_message = do_test_manual_inbound_accept_with_override(anchors_cfg, Some(overrides));
 	assert_eq!(accept_message.common_fields.max_htlc_value_in_flight_msat, 5_000_000);
 	assert_eq!(accept_message.common_fields.htlc_minimum_msat, 1_000);
@@ -1066,6 +1063,7 @@ pub fn test_user_configurable_csv_delay() {
 pub fn test_accept_inbound_channel_config_override() {
 	let mut conf = UserConfig::default();
 	conf.channel_handshake_config.minimum_depth = 1;
+	conf.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = false;
 
 	let chanmon_cfgs = create_chanmon_cfgs(2);
 	let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);

lightning/src/ln/channel_type_tests.rs

@@ -34,8 +34,10 @@ fn test_option_anchors_zero_fee_initial() {
 	let mut expected_type = ChannelTypeFeatures::only_static_remote_key();
 	expected_type.set_anchors_zero_fee_htlc_tx_required();
 
+	let mut start_cfg = UserConfig::default();
+	start_cfg.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = false;
 	do_test_get_initial_channel_type(
-		UserConfig::default(),
+		start_cfg,
 		InitFeatures::empty(),
 		ChannelTypeFeatures::only_static_remote_key(),
 		|cfg: &mut UserConfig| {
@@ -225,13 +227,15 @@ fn do_test_supports_channel_type(config: UserConfig, expected_channel_type: Chan
 	let node_id_b =
 		PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[2; 32]).unwrap());
 
+	let mut non_anchors_config = UserConfig::default();
+	non_anchors_config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = false;
 	// Assert that we get `static_remotekey` when no custom config is negotiated.
 	let channel_a = OutboundV1Channel::<&TestKeysInterface>::new(
 		&fee_estimator,
 		&&keys_provider,
 		&&keys_provider,
 		node_id_b,
-		&channelmanager::provided_init_features(&UserConfig::default()),
+		&channelmanager::provided_init_features(&non_anchors_config),
 		10000000,
 		100000,
 		42,

lightning/src/ln/channelmanager.rs

@@ -2028,7 +2028,7 @@ impl<
 ///
 /// ## Opening Channels
 ///
-/// To an open a channel with a peer, call [`create_channel`]. This will initiate the process of
+/// To open a channel with a peer, call [`create_channel`]. This will initiate the process of
 /// opening an outbound channel, which requires self-funding when handling
 /// [`Event::FundingGenerationReady`].
 ///
@@ -5344,7 +5344,7 @@ impl<
 	/// using [`ChannelMonitorUpdateStatus::InProgress`]), the payment may be lost on restart. See
 	/// [`ChannelManager::list_recent_payments`] for more information.
 	///
-	/// Routes are automatically found using the [`Router] provided on startup. To fix a route for a
+	/// Routes are automatically found using the [`Router`] provided on startup. To fix a route for a
 	/// particular payment, use [`Self::send_payment_with_route`] or match the [`PaymentId`] passed to
 	/// [`Router::find_route_with_id`].
 	///

lightning/src/ln/functional_test_utils.rs

@@ -4534,6 +4534,7 @@ pub fn create_node_cfgs_with_node_id_message_router<'a>(
 
 pub fn test_default_channel_config() -> UserConfig {
 	let mut default_config = UserConfig::default();
+	default_config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx = false;
 	// Set cltv_expiry_delta slightly lower to keep the final CLTV values inside one byte in our
 	// tests so that our script-length checks don't fail (see ACCEPTED_HTLC_SCRIPT_WEIGHT).
 	default_config.channel_config.cltv_expiry_delta = MIN_CLTV_EXPIRY_DELTA;

lightning/src/util/config.rs

@@ -178,7 +178,7 @@ pub struct ChannelHandshakeConfig {
 	/// counterparties that do not support the `anchors_zero_fee_htlc_tx` option; we will simply
 	/// fall back to a `static_remote_key` channel.
 	///
-	/// Default value: `false` (This value is likely to change to `true` in the future.)
+	/// Default value: `true`
 	///
 	/// [`ChannelManager`]: crate::ln::channelmanager::ChannelManager
 	/// [`ChannelManager::accept_inbound_channel`]: crate::ln::channelmanager::ChannelManager::accept_inbound_channel
@@ -252,7 +252,7 @@ impl Default for ChannelHandshakeConfig {
 			announce_for_forwarding: false,
 			commit_upfront_shutdown_pubkey: true,
 			their_channel_reserve_proportional_millionths: 10_000,
-			negotiate_anchors_zero_fee_htlc_tx: false,
+			negotiate_anchors_zero_fee_htlc_tx: true,
 			negotiate_anchor_zero_fee_commitments: false,
 			our_max_accepted_htlcs: 50,
 		}

pending_changelog/4337-manual-channel-accept-default-anchors.txt

@@ -0,0 +1,18 @@
+# API Updates
+
+ * `ChannelHandshakeConfig::negotiate_anchors_zero_fee_htlc_tx`
+   now defaults to `true` (previously `false`). This means anchor output channels
+   will be negotiated by default for all new channels if the counterparty supports
+   it, requiring users to maintain an on-chain reserve for fee bumping in the
+   event of force-closes.
+
+ * All inbound channels now require manual acceptance.
+   `UserConfig::manually_accept_inbound_channels` has been removed, and
+   `Event::OpenChannelRequest` will now always be generated for inbound channel
+   requests. Users must handle this event and call either
+   `ChannelManager::accept_inbound_channel` (or
+   `accept_inbound_channel_from_trusted_peer_0conf` for zero-conf channels) to
+   accept the channel, or `ChannelManager::force_close_broadcasting_latest_txn`
+   to reject it. This ensures users can verify they have sufficient on-chain
+   funds before accepting channels with anchor outputs.
+