Expose outbound SCID alias in `ChannelDetails` and use in routing

This supports routing outbound over 0-conf channels by utilizing
the outbound SCID alias that we assign to all channels to refer to
the selected channel when routing.

diff --git a/fuzz/src/router.rs b/fuzz/src/router.rs
index 786bfa3e589eb05dc393a807be90efc46c5febf7..80ea1f1bc73d6932e4ab3db1a2da8904b0f77f14 100644 (file)
--- a/fuzz/src/router.rs
+++ b/fuzz/src/router.rs
@@ -222,6 +222,7 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
                                                                channel_type: None,
                                                                short_channel_id: Some(scid),
                                                                inbound_scid_alias: None,
+                                                               outbound_scid_alias: None,
                                                                channel_value_satoshis: capacity,
                                                                user_channel_id: 0, inbound_capacity_msat: 0,
                                                                unspendable_punishment_reserve: None,

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index 8193ba443c2da58cd75a5ad79e7c098b4e2ecace..8053f9c32cc2410651e5cef2c686310e4238a8d9 100644 (file)
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -968,9 +968,25 @@ pub struct ChannelDetails {
        /// Note that if [`inbound_scid_alias`] is set, it must be used for invoices and inbound
        /// payments instead of this. See [`get_inbound_payment_scid`].
        ///
+       /// For channels with [`confirmations_required`] set to `Some(0)`, [`outbound_scid_alias`] may
+       /// be used in place of this in outbound routes. See [`get_outbound_payment_scid`].
+       ///
        /// [`inbound_scid_alias`]: Self::inbound_scid_alias
+       /// [`outbound_scid_alias`]: Self::outbound_scid_alias
        /// [`get_inbound_payment_scid`]: Self::get_inbound_payment_scid
+       /// [`get_outbound_payment_scid`]: Self::get_outbound_payment_scid
+       /// [`confirmations_required`]: Self::confirmations_required
        pub short_channel_id: Option<u64>,
+       /// An optional [`short_channel_id`] alias for this channel, randomly generated by us and
+       /// usable in place of [`short_channel_id`] to reference the channel in outbound routes when
+       /// the channel has not yet been confirmed (as long as [`confirmations_required`] is
+       /// `Some(0)`).
+       ///
+       /// This will be `None` as long as the channel is not available for routing outbound payments.
+       ///
+       /// [`short_channel_id`]: Self::short_channel_id
+       /// [`confirmations_required`]: Self::confirmations_required
+       pub outbound_scid_alias: Option<u64>,
        /// An optional [`short_channel_id`] alias for this channel, randomly generated by our
        /// counterparty and usable in place of [`short_channel_id`] in invoice route hints. Our
        /// counterparty will recognize the alias provided here in place of the [`short_channel_id`]
@@ -1088,6 +1104,16 @@ impl ChannelDetails {
        pub fn get_inbound_payment_scid(&self) -> Option<u64> {
                self.inbound_scid_alias.or(self.short_channel_id)
        }
+
+       /// Gets the current SCID which should be used to identify this channel for outbound payments.
+       /// This should be used in [`Route`]s to describe the first hop or in other contexts where
+       /// we're sending or forwarding a payment outbound over this channel.
+       ///
+       /// This is either the [`ChannelDetails::short_channel_id`], if set, or the
+       /// [`ChannelDetails::outbound_scid_alias`]. See those for more information.
+       pub fn get_outbound_payment_scid(&self) -> Option<u64> {
+               self.short_channel_id.or(self.outbound_scid_alias)
+       }
 }
 
 /// If a payment fails to send, it can be in one of several states. This enum is returned as the
@@ -1714,6 +1740,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                        // `have_received_message` indicates that type negotiation has completed.
                                        channel_type: if channel.have_received_message() { Some(channel.get_channel_type().clone()) } else { None },
                                        short_channel_id: channel.get_short_channel_id(),
+                                       outbound_scid_alias: if channel.is_usable() { Some(channel.outbound_scid_alias()) } else { None },
                                        inbound_scid_alias: channel.latest_inbound_scid_alias(),
                                        channel_value_satoshis: channel.get_value_satoshis(),
                                        unspendable_punishment_reserve: to_self_reserve_satoshis,
@@ -5984,6 +6011,7 @@ impl_writeable_tlv_based!(ChannelDetails, {
        (2, channel_id, required),
        (3, channel_type, option),
        (4, counterparty, required),
+       (5, outbound_scid_alias, option),
        (6, funding_txo, option),
        (8, short_channel_id, option),
        (10, channel_value_satoshis, required),

diff --git a/lightning/src/ln/priv_short_conf_tests.rs b/lightning/src/ln/priv_short_conf_tests.rs
index ed11b993fc75f7535bf8716b926448e0cfda1c83..24a0e47876130b24c05ddbe220db869e9869bd58 100644 (file)
--- a/lightning/src/ln/priv_short_conf_tests.rs
+++ b/lightning/src/ln/priv_short_conf_tests.rs
@@ -639,4 +639,6 @@ fn test_simple_0conf_channel() {
 
        assert_eq!(nodes[0].node.list_usable_channels().len(), 1);
        assert_eq!(nodes[1].node.list_usable_channels().len(), 1);
+
+       send_payment(&nodes[0], &[&nodes[1]], 100_000);
 }

diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs
index dc094b9b6e0309a8fc51cd01a75a1ad480c3d432..c02da4d705f16db53cf056bc1a83d2c548d7131a 100644 (file)
--- a/lightning/src/routing/router.rs
+++ b/lightning/src/routing/router.rs
@@ -368,7 +368,7 @@ enum CandidateRouteHop<'a> {
 impl<'a> CandidateRouteHop<'a> {
        fn short_channel_id(&self) -> u64 {
                match self {
-                       CandidateRouteHop::FirstHop { details } => details.short_channel_id.unwrap(),
+                       CandidateRouteHop::FirstHop { details } => details.get_outbound_payment_scid().unwrap(),
                        CandidateRouteHop::PublicHop { short_channel_id, .. } => *short_channel_id,
                        CandidateRouteHop::PrivateHop { hint } => hint.short_channel_id,
                }
@@ -777,7 +777,7 @@ where L::Target: Logger {
                HashMap::with_capacity(if first_hops.is_some() { first_hops.as_ref().unwrap().len() } else { 0 });
        if let Some(hops) = first_hops {
                for chan in hops {
-                       if chan.short_channel_id.is_none() {
+                       if chan.get_outbound_payment_scid().is_none() {
                                panic!("first_hops should be filled in with usable channels, not pending ones");
                        }
                        if chan.counterparty.node_id == *our_node_pubkey {
@@ -1331,7 +1331,7 @@ where L::Target: Logger {
                                        let mut features_set = false;
                                        if let Some(first_channels) = first_hop_targets.get(&ordered_hops.last().unwrap().0.node_id) {
                                                for details in first_channels {
-                                                       if details.short_channel_id.unwrap() == ordered_hops.last().unwrap().0.candidate.short_channel_id() {
+                                                       if details.get_outbound_payment_scid().unwrap() == ordered_hops.last().unwrap().0.candidate.short_channel_id() {
                                                                ordered_hops.last_mut().unwrap().1 = details.counterparty.features.to_context();
                                                                features_set = true;
                                                                break;
@@ -1742,6 +1742,7 @@ mod tests {
                        funding_txo: Some(OutPoint { txid: bitcoin::Txid::from_slice(&[0; 32]).unwrap(), index: 0 }),
                        channel_type: None,
                        short_channel_id,
+                       outbound_scid_alias: None,
                        inbound_scid_alias: None,
                        channel_value_satoshis: 0,
                        user_channel_id: 0,
@@ -5474,6 +5475,7 @@ mod benches {
                        channel_type: None,
                        short_channel_id: Some(1),
                        inbound_scid_alias: None,
+                       outbound_scid_alias: None,
                        channel_value_satoshis: 10_000_000,
                        user_channel_id: 0,
                        balance_msat: 10_000_000,