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

[rust-lightning] / lightning / src / ln / channelmanager.rs

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),