Add a next-outbound-HTLC minimum field to chan details and use it

In the coming commits, in order to ensure all routes we generate
are usable, we'll start calculating the next-HTLC minimum for our
channels and using it in the router. Here we set this up by adding
an always-0 field for it in `ChannelDetails` and use it when
routing.

diff --git a/fuzz/src/router.rs b/fuzz/src/router.rs
index 00c53dfe58e5d2ca7ed365bc6381f0de6fb4427b..72935f153eab861f00509c310f88d5d822ea10fd 100644 (file)
--- a/fuzz/src/router.rs
+++ b/fuzz/src/router.rs
@@ -265,6 +265,7 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
                                                                balance_msat: 0,
                                                                outbound_capacity_msat: capacity.saturating_mul(1000),
                                                                next_outbound_htlc_limit_msat: capacity.saturating_mul(1000),
+                                                               next_outbound_htlc_minimum_msat: 0,
                                                                inbound_htlc_minimum_msat: None,
                                                                inbound_htlc_maximum_msat: None,
                                                                config: None,

diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index 23e56f94bd78d4e7b2418aea9a9fe6c834f38e18..03acb73309d7bb171e4ce4cb7a91e313fcd13007 100644 (file)
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -73,6 +73,8 @@ pub struct AvailableBalances {
        pub outbound_capacity_msat: u64,
        /// The maximum value we can assign to the next outbound HTLC
        pub next_outbound_htlc_limit_msat: u64,
+       /// The minimum value we can assign to the next outbound HTLC
+       pub next_outbound_htlc_minimum_msat: u64,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq)]
@@ -2762,6 +2764,7 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
                                0) as u64,
                        outbound_capacity_msat,
                        next_outbound_htlc_limit_msat: available_capacity_msat,
+                       next_outbound_htlc_minimum_msat: 0,
                        balance_msat,
                }
        }

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index 30eab9066fd0b4190ef65167d8e82c98c51c9be1..b5e7d603411f259ff3b9dda02c9f153661717cc8 100644 (file)
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -1274,8 +1274,14 @@ pub struct ChannelDetails {
        /// the current state and per-HTLC limit(s). This is intended for use when routing, allowing us
        /// to use a limit as close as possible to the HTLC limit we can currently send.
        ///
-       /// See also [`ChannelDetails::balance_msat`] and [`ChannelDetails::outbound_capacity_msat`].
+       /// See also [`ChannelDetails::next_outbound_htlc_minimum_msat`],
+       /// [`ChannelDetails::balance_msat`], and [`ChannelDetails::outbound_capacity_msat`].
        pub next_outbound_htlc_limit_msat: u64,
+       /// The minimum value for sending a single HTLC to the remote peer. This is the equivalent of
+       /// [`ChannelDetails::next_outbound_htlc_limit_msat`] but represents a lower-bound, rather than
+       /// an upper-bound. This is intended for use when routing, allowing us to ensure we pick a
+       /// route which is valid.
+       pub next_outbound_htlc_minimum_msat: u64,
        /// The available inbound capacity for the remote peer to send HTLCs to us. This does not
        /// include any pending HTLCs which are not yet fully resolved (and, thus, whose balance is not
        /// available for inclusion in new inbound HTLCs).
@@ -1395,6 +1401,7 @@ impl ChannelDetails {
                        inbound_capacity_msat: balance.inbound_capacity_msat,
                        outbound_capacity_msat: balance.outbound_capacity_msat,
                        next_outbound_htlc_limit_msat: balance.next_outbound_htlc_limit_msat,
+                       next_outbound_htlc_minimum_msat: balance.next_outbound_htlc_minimum_msat,
                        user_channel_id: channel.get_user_id(),
                        confirmations_required: channel.minimum_depth(),
                        confirmations: Some(channel.get_funding_tx_confirmations(best_block_height)),
@@ -6951,10 +6958,9 @@ impl Writeable for ChannelDetails {
                        (14, user_channel_id_low, required),
                        (16, self.balance_msat, required),
                        (18, self.outbound_capacity_msat, required),
-                       // Note that by the time we get past the required read above, outbound_capacity_msat will be
-                       // filled in, so we can safely unwrap it here.
-                       (19, self.next_outbound_htlc_limit_msat, (default_value, outbound_capacity_msat.0.unwrap() as u64)),
+                       (19, self.next_outbound_htlc_limit_msat, required),
                        (20, self.inbound_capacity_msat, required),
+                       (21, self.next_outbound_htlc_minimum_msat, required),
                        (22, self.confirmations_required, option),
                        (24, self.force_close_spend_delay, option),
                        (26, self.is_outbound, required),
@@ -6991,6 +6997,7 @@ impl Readable for ChannelDetails {
                        // filled in, so we can safely unwrap it here.
                        (19, next_outbound_htlc_limit_msat, (default_value, outbound_capacity_msat.0.unwrap() as u64)),
                        (20, inbound_capacity_msat, required),
+                       (21, next_outbound_htlc_minimum_msat, (default_value, 0)),
                        (22, confirmations_required, option),
                        (24, force_close_spend_delay, option),
                        (26, is_outbound, required),
@@ -7024,6 +7031,7 @@ impl Readable for ChannelDetails {
                        balance_msat: balance_msat.0.unwrap(),
                        outbound_capacity_msat: outbound_capacity_msat.0.unwrap(),
                        next_outbound_htlc_limit_msat: next_outbound_htlc_limit_msat.0.unwrap(),
+                       next_outbound_htlc_minimum_msat: next_outbound_htlc_minimum_msat.0.unwrap(),
                        inbound_capacity_msat: inbound_capacity_msat.0.unwrap(),
                        confirmations_required,
                        confirmations,

diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs
index ef6fef0a7eb42ea87b8d0876f0b11f99112d83cb..bf854aed63745b0bbfd7d5749ffa8704c705c4ac 100644 (file)
--- a/lightning/src/routing/router.rs
+++ b/lightning/src/routing/router.rs
@@ -929,7 +929,7 @@ impl<'a> CandidateRouteHop<'a> {
 
        fn htlc_minimum_msat(&self) -> u64 {
                match self {
-                       CandidateRouteHop::FirstHop { .. } => 0,
+                       CandidateRouteHop::FirstHop { details } => details.next_outbound_htlc_minimum_msat,
                        CandidateRouteHop::PublicHop { info, .. } => info.direction().htlc_minimum_msat,
                        CandidateRouteHop::PrivateHop { hint } => hint.htlc_minimum_msat.unwrap_or(0),
                }
@@ -2460,6 +2460,7 @@ mod tests {
                        balance_msat: 0,
                        outbound_capacity_msat,
                        next_outbound_htlc_limit_msat: outbound_capacity_msat,
+                       next_outbound_htlc_minimum_msat: 0,
                        inbound_capacity_msat: 42,
                        unspendable_punishment_reserve: None,
                        confirmations_required: None,
@@ -6121,6 +6122,7 @@ pub(crate) mod bench_utils {
                        user_channel_id: 0,
                        balance_msat: 10_000_000_000,
                        outbound_capacity_msat: 10_000_000_000,
+                       next_outbound_htlc_minimum_msat: 0,
                        next_outbound_htlc_limit_msat: 10_000_000_000,
                        inbound_capacity_msat: 0,
                        unspendable_punishment_reserve: None,