Add max path length knob to PaymentParameters.

[rust-lightning] / lightning / src / routing / router.rs

diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs
index 8744761e72d01aaf5bc5ad1e6961f03123fe8c8b..4a4063f52f99e8ce89bf5e52e7e0fbf07cce2370 100644 (file)
--- a/lightning/src/routing/router.rs
+++ b/lightning/src/routing/router.rs
@@ -654,6 +654,8 @@ const DEFAULT_MAX_CHANNEL_SATURATION_POW_HALF: u8 = 2;
 // The median hop CLTV expiry delta currently seen in the network.
 const MEDIAN_HOP_CLTV_EXPIRY_DELTA: u32 = 40;
 
+/// Estimated maximum number of hops that can be included in a payment path. May be inaccurate if
+/// payment metadata, custom TLVs, or blinded paths are included in the payment.
 // During routing, we only consider paths shorter than our maximum length estimate.
 // In the TLV onion format, there is no fixed maximum length, but the `hop_payloads`
 // field is always 1300 bytes. As the `tlv_payload` for each hop may vary in length, we have to
@@ -665,7 +667,7 @@ const MEDIAN_HOP_CLTV_EXPIRY_DELTA: u32 = 40;
 // (payment_secret and total_msat) = 93 bytes for the final hop.
 // Since the length of the potentially included `payment_metadata` is unknown to us, we round
 // down from (1300-93) / 61 = 19.78... to arrive at a conservative estimate of 19.
-const MAX_PATH_LENGTH_ESTIMATE: u8 = 19;
+pub const MAX_PATH_LENGTH_ESTIMATE: u8 = 19;
 
 /// Information used to route a payment.
 #[derive(Clone, Debug, Hash, PartialEq, Eq)]
@@ -684,6 +686,10 @@ pub struct PaymentParameters {
        /// Defaults to [`DEFAULT_MAX_PATH_COUNT`].
        pub max_path_count: u8,
 
+       /// The maximum number of [`Path::hops`] in any returned path.
+       /// Defaults to [`MAX_PATH_LENGTH_ESTIMATE`].
+       pub max_path_length: u8,
+
        /// Selects the maximum share of a channel's total capacity which will be sent over a channel,
        /// as a power of 1/2. A higher value prefers to send the payment using more MPP parts whereas
        /// a lower value prefers to send larger MPP parts, potentially saturating channels and
@@ -730,6 +736,7 @@ impl Writeable for PaymentParameters {
                        (8, *blinded_hints, optional_vec),
                        (9, self.payee.final_cltv_expiry_delta(), option),
                        (11, self.previously_failed_blinded_path_idxs, required_vec),
+                       (13, self.max_path_length, required),
                });
                Ok(())
        }
@@ -749,6 +756,7 @@ impl ReadableArgs<u32> for PaymentParameters {
                        (8, blinded_route_hints, optional_vec),
                        (9, final_cltv_expiry_delta, (default_value, default_final_cltv_expiry_delta)),
                        (11, previously_failed_blinded_path_idxs, optional_vec),
+                       (13, max_path_length, (default_value, MAX_PATH_LENGTH_ESTIMATE)),
                });
                let blinded_route_hints = blinded_route_hints.unwrap_or(vec![]);
                let payee = if blinded_route_hints.len() != 0 {
@@ -773,6 +781,7 @@ impl ReadableArgs<u32> for PaymentParameters {
                        expiry_time,
                        previously_failed_channels: previously_failed_channels.unwrap_or(Vec::new()),
                        previously_failed_blinded_path_idxs: previously_failed_blinded_path_idxs.unwrap_or(Vec::new()),
+                       max_path_length: _init_tlv_based_struct_field!(max_path_length, (default_value, unused)),
                })
        }
 }
@@ -789,6 +798,7 @@ impl PaymentParameters {
                        expiry_time: None,
                        max_total_cltv_expiry_delta: DEFAULT_MAX_TOTAL_CLTV_EXPIRY_DELTA,
                        max_path_count: DEFAULT_MAX_PATH_COUNT,
+                       max_path_length: MAX_PATH_LENGTH_ESTIMATE,
                        max_channel_saturation_power_of_half: DEFAULT_MAX_CHANNEL_SATURATION_POW_HALF,
                        previously_failed_channels: Vec::new(),
                        previously_failed_blinded_path_idxs: Vec::new(),
@@ -828,6 +838,7 @@ impl PaymentParameters {
                        expiry_time: None,
                        max_total_cltv_expiry_delta: DEFAULT_MAX_TOTAL_CLTV_EXPIRY_DELTA,
                        max_path_count: DEFAULT_MAX_PATH_COUNT,
+                       max_path_length: MAX_PATH_LENGTH_ESTIMATE,
                        max_channel_saturation_power_of_half: DEFAULT_MAX_CHANNEL_SATURATION_POW_HALF,
                        previously_failed_channels: Vec::new(),
                        previously_failed_blinded_path_idxs: Vec::new(),