Builder for creating static invoices from offers

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

diff --git a/lightning/src/ln/onion_utils.rs b/lightning/src/ln/onion_utils.rs
index 2aba2c75748ed4ad74813206b7e302964d594075..9a207c9e52d1dd1805592bf039dd9ff84387a6b4 100644 (file)
--- a/lightning/src/ln/onion_utils.rs
+++ b/lightning/src/ln/onion_utils.rs
@@ -10,12 +10,14 @@
 use crate::blinded_path::BlindedHop;
 use crate::crypto::chacha20::ChaCha20;
 use crate::crypto::streams::ChaChaReader;
+use crate::ln::channel::TOTAL_BITCOIN_SUPPLY_SATOSHIS;
 use crate::ln::channelmanager::{HTLCSource, RecipientOnionFields};
+use crate::ln::features::{ChannelFeatures, NodeFeatures};
 use crate::ln::msgs;
 use crate::ln::types::{PaymentHash, PaymentPreimage};
 use crate::ln::wire::Encode;
 use crate::routing::gossip::NetworkUpdate;
-use crate::routing::router::{Path, RouteHop};
+use crate::routing::router::{Path, RouteHop, RouteParameters};
 use crate::sign::NodeSigner;
 use crate::util::errors::{self, APIError};
 use crate::util::logger::Logger;
@@ -310,6 +312,77 @@ where
        Ok((cur_value_msat, cur_cltv))
 }
 
+pub(crate) const MIN_FINAL_VALUE_ESTIMATE_WITH_OVERPAY: u64 = 100_000_000;
+
+pub(crate) fn set_max_path_length(
+       route_params: &mut RouteParameters, recipient_onion: &RecipientOnionFields,
+       keysend_preimage: Option<PaymentPreimage>, best_block_height: u32,
+) -> Result<(), ()> {
+       const PAYLOAD_HMAC_LEN: usize = 32;
+       let unblinded_intermed_payload_len = msgs::OutboundOnionPayload::Forward {
+               short_channel_id: 42,
+               amt_to_forward: TOTAL_BITCOIN_SUPPLY_SATOSHIS,
+               outgoing_cltv_value: route_params.payment_params.max_total_cltv_expiry_delta,
+       }
+       .serialized_length()
+       .saturating_add(PAYLOAD_HMAC_LEN);
+
+       const OVERPAY_ESTIMATE_MULTIPLER: u64 = 3;
+       let final_value_msat_with_overpay_buffer = core::cmp::max(
+               route_params.final_value_msat.saturating_mul(OVERPAY_ESTIMATE_MULTIPLER),
+               MIN_FINAL_VALUE_ESTIMATE_WITH_OVERPAY,
+       );
+
+       let blinded_tail_opt = route_params
+               .payment_params
+               .payee
+               .blinded_route_hints()
+               .iter()
+               .map(|(_, path)| path)
+               .max_by_key(|path| path.serialized_length())
+               .map(|largest_path| BlindedTailHopIter {
+                       hops: largest_path.blinded_hops.iter(),
+                       blinding_point: largest_path.blinding_point,
+                       final_value_msat: final_value_msat_with_overpay_buffer,
+                       excess_final_cltv_expiry_delta: 0,
+               });
+
+       let unblinded_route_hop = RouteHop {
+               pubkey: PublicKey::from_slice(&[2; 33]).unwrap(),
+               node_features: NodeFeatures::empty(),
+               short_channel_id: 42,
+               channel_features: ChannelFeatures::empty(),
+               fee_msat: final_value_msat_with_overpay_buffer,
+               cltv_expiry_delta: route_params.payment_params.max_total_cltv_expiry_delta,
+               maybe_announced_channel: false,
+       };
+       let mut num_reserved_bytes: usize = 0;
+       let build_payloads_res = build_onion_payloads_callback(
+               core::iter::once(&unblinded_route_hop),
+               blinded_tail_opt,
+               final_value_msat_with_overpay_buffer,
+               &recipient_onion,
+               best_block_height,
+               &keysend_preimage,
+               |_, payload| {
+                       num_reserved_bytes = num_reserved_bytes
+                               .saturating_add(payload.serialized_length())
+                               .saturating_add(PAYLOAD_HMAC_LEN);
+               },
+       );
+       debug_assert!(build_payloads_res.is_ok());
+
+       let max_path_length = 1300usize
+               .checked_sub(num_reserved_bytes)
+               .map(|p| p / unblinded_intermed_payload_len)
+               .and_then(|l| u8::try_from(l.saturating_add(1)).ok())
+               .ok_or(())?;
+
+       route_params.payment_params.max_path_length =
+               core::cmp::min(max_path_length, route_params.payment_params.max_path_length);
+       Ok(())
+}
+
 /// Length of the onion data packet. Before TLV-based onions this was 20 65-byte hops, though now
 /// the hops can be of variable length.
 pub(crate) const ONION_DATA_LEN: usize = 20 * 65;