From 5b28744755a4a5ef0303c9cbf927502495194055 Mon Sep 17 00:00:00 2001 From: Valentine Wallace Date: Fri, 12 Mar 2021 14:23:20 -0500 Subject: [PATCH] Add CounterpartyForwardingInfo field to channel. This will be filled in in upcoming commits, then exposed in ChannelDetails to allow constructing route hints for invoices. Also update the cltv_expiry_deta comment in msgs::ChannelUpdate Co-authored-by: Valentine Wallace Co-authored-by: Antoine Riard --- lightning/src/ln/channel.rs | 40 +++++++++++++++++++++++++++++++++++++ lightning/src/ln/msgs.rs | 9 ++++++++- 2 files changed, 48 insertions(+), 1 deletion(-) diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs index 9e4bb081c..426083dd8 100644 --- a/lightning/src/ln/channel.rs +++ b/lightning/src/ln/channel.rs @@ -281,6 +281,18 @@ impl HTLCCandidate { } } +/// Information needed for constructing an invoice route hint for this channel. +pub struct CounterpartyForwardingInfo { + /// Base routing fee in millisatoshis. + pub fee_base_msat: u32, + /// Amount in millionths of a satoshi the channel will charge per transferred satoshi. + pub fee_proportional_millionths: u32, + /// The minimum difference in cltv_expiry between an ingoing HTLC and its outgoing counterpart, + /// such that the outgoing HTLC is forwardable to this counterparty. See `msgs::ChannelUpdate`'s + /// `cltv_expiry_delta` for more details. + pub cltv_expiry_delta: u16, +} + // TODO: We should refactor this to be an Inbound/OutboundChannel until initial setup handshaking // has been completed, and then turn into a Channel to get compiler-time enforcement of things like // calling channel_id() before we're set up or things like get_outbound_funding_signed on an @@ -391,6 +403,8 @@ pub(super) struct Channel { //implied by OUR_MAX_HTLCS: max_accepted_htlcs: u16, minimum_depth: u32, + counterparty_forwarding_info: Option, + pub(crate) channel_transaction_parameters: ChannelTransactionParameters, counterparty_cur_commitment_point: Option, @@ -577,6 +591,8 @@ impl Channel { counterparty_max_accepted_htlcs: 0, minimum_depth: 0, // Filled in in accept_channel + counterparty_forwarding_info: None, + channel_transaction_parameters: ChannelTransactionParameters { holder_pubkeys: pubkeys, holder_selected_contest_delay: config.own_channel_config.our_to_self_delay, @@ -813,6 +829,8 @@ impl Channel { counterparty_max_accepted_htlcs: msg.max_accepted_htlcs, minimum_depth: config.own_channel_config.minimum_depth, + counterparty_forwarding_info: None, + channel_transaction_parameters: ChannelTransactionParameters { holder_pubkeys: pubkeys, holder_selected_contest_delay: config.own_channel_config.our_to_self_delay, @@ -4437,6 +4455,16 @@ impl Writeable for Channel { self.counterparty_max_accepted_htlcs.write(writer)?; self.minimum_depth.write(writer)?; + match &self.counterparty_forwarding_info { + Some(info) => { + 1u8.write(writer)?; + info.fee_base_msat.write(writer)?; + info.fee_proportional_millionths.write(writer)?; + info.cltv_expiry_delta.write(writer)?; + }, + None => 0u8.write(writer)? + } + self.channel_transaction_parameters.write(writer)?; self.counterparty_cur_commitment_point.write(writer)?; @@ -4597,6 +4625,16 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel let counterparty_max_accepted_htlcs = Readable::read(reader)?; let minimum_depth = Readable::read(reader)?; + let counterparty_forwarding_info = match ::read(reader)? { + 0 => None, + 1 => Some(CounterpartyForwardingInfo { + fee_base_msat: Readable::read(reader)?, + fee_proportional_millionths: Readable::read(reader)?, + cltv_expiry_delta: Readable::read(reader)?, + }), + _ => return Err(DecodeError::InvalidValue), + }; + let channel_parameters = Readable::read(reader)?; let counterparty_cur_commitment_point = Readable::read(reader)?; @@ -4667,6 +4705,8 @@ impl<'a, Signer: Sign, K: Deref> ReadableArgs<&'a K> for Channel counterparty_max_accepted_htlcs, minimum_depth, + counterparty_forwarding_info, + channel_transaction_parameters: channel_parameters, counterparty_cur_commitment_point, diff --git a/lightning/src/ln/msgs.rs b/lightning/src/ln/msgs.rs index 3042b4d32..004bd3d99 100644 --- a/lightning/src/ln/msgs.rs +++ b/lightning/src/ln/msgs.rs @@ -543,7 +543,14 @@ pub struct UnsignedChannelUpdate { pub timestamp: u32, /// Channel flags pub flags: u8, - /// The number of blocks to subtract from incoming HTLC cltv_expiry values + /// The number of blocks such that if: + /// `incoming_htlc.cltv_expiry < outgoing_htlc.cltv_expiry + cltv_expiry_delta` + /// then we need to fail the HTLC backwards. When forwarding an HTLC, cltv_expiry_delta determines + /// the outgoing HTLC's minimum cltv_expiry value -- so, if an incoming HTLC comes in with a + /// cltv_expiry of 100000, and the node we're forwarding to has a cltv_expiry_delta value of 10, + /// then we'll check that the outgoing HTLC's cltv_expiry value is at least 100010 before + /// forwarding. Note that the HTLC sender is the one who originally sets this value when + /// constructing the route. pub cltv_expiry_delta: u16, /// The minimum HTLC size incoming to sender, in milli-satoshi pub htlc_minimum_msat: u64, -- 2.39.5