Dry-up InputMaterial::Funding

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

diff --git a/lightning/src/ln/channelmonitor.rs b/lightning/src/ln/channelmonitor.rs
index 7e961a129eb19407d8531b61588e53429da1d8ad..da8ba03a7271a7d359f7e58dcf51851c617ee790 100644 (file)
--- a/lightning/src/ln/channelmonitor.rs
+++ b/lightning/src/ln/channelmonitor.rs
@@ -383,6 +383,28 @@ pub(crate) const LATENCY_GRACE_PERIOD_BLOCKS: u32 = 3;
 /// solved by a previous claim tx. What we want to avoid is reorg evicting our claim tx and us not
 /// keeping bumping another claim tx to solve the outpoint.
 pub(crate) const ANTI_REORG_DELAY: u32 = 6;
+/// Number of blocks before confirmation at which we fail back an un-relayed HTLC or at which we
+/// refuse to accept a new HTLC.
+///
+/// This is used for a few separate purposes:
+/// 1) if we've received an MPP HTLC to us and it expires within this many blocks and we are
+///    waiting on additional parts (or waiting on the preimage for any HTLC from the user), we will
+///    fail this HTLC,
+/// 2) if we receive an HTLC within this many blocks of its expiry (plus one to avoid a race
+///    condition with the above), we will fail this HTLC without telling the user we received it,
+/// 3) if we are waiting on a connection or a channel state update to send an HTLC to a peer, and
+///    that HTLC expires within this many blocks, we will simply fail the HTLC instead.
+///
+/// (1) is all about protecting us - we need enough time to update the channel state before we hit
+/// CLTV_CLAIM_BUFFER, at which point we'd go on chain to claim the HTLC with the preimage.
+///
+/// (2) is the same, but with an additional buffer to avoid accepting an HTLC which is immediately
+/// in a race condition between the user connecting a block (which would fail it) and the user
+/// providing us the preimage (which would claim it).
+///
+/// (3) is about our counterparty - we don't want to relay an HTLC to a counterparty when they may
+/// end up force-closing the channel on us to claim it.
+pub(crate) const HTLC_FAIL_BACK_BUFFER: u32 = CLTV_CLAIM_BUFFER + LATENCY_GRACE_PERIOD_BLOCKS;
 
 #[derive(Clone, PartialEq)]
 struct LocalSignedTx {
@@ -420,9 +442,7 @@ pub(crate) enum InputMaterial {
                preimage: Option<PaymentPreimage>,
                amount: u64,
        },
-       Funding {
-               channel_value: u64,
-       }
+       Funding {}
 }
 
 impl Writeable for InputMaterial  {
@@ -449,9 +469,8 @@ impl Writeable for InputMaterial  {
                                preimage.write(writer)?;
                                writer.write_all(&byte_utils::be64_to_array(*amount))?;
                        },
-                       &InputMaterial::Funding { ref channel_value } => {
+                       &InputMaterial::Funding {} => {
                                writer.write_all(&[3; 1])?;
-                               channel_value.write(writer)?;
                        }
                }
                Ok(())
@@ -498,10 +517,7 @@ impl Readable for InputMaterial {
                                }
                        },
                        3 => {
-                               let channel_value = Readable::read(reader)?;
-                               InputMaterial::Funding {
-                                       channel_value
-                               }
+                               InputMaterial::Funding {}
                        }
                        _ => return Err(DecodeError::InvalidValue),
                };
@@ -1842,7 +1858,7 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
                }
                let should_broadcast = self.would_broadcast_at_height(height);
                if should_broadcast {
-                       claimable_outpoints.push(ClaimRequest { absolute_timelock: height, aggregable: false, outpoint: BitcoinOutPoint { txid: self.funding_info.0.txid.clone(), vout: self.funding_info.0.index as u32 }, witness_data: InputMaterial::Funding { channel_value: self.channel_value_satoshis }});
+                       claimable_outpoints.push(ClaimRequest { absolute_timelock: height, aggregable: false, outpoint: BitcoinOutPoint { txid: self.funding_info.0.txid.clone(), vout: self.funding_info.0.index as u32 }, witness_data: InputMaterial::Funding {}});
                }
                if should_broadcast {
                        if let Some(commitment_tx) = self.onchain_tx_handler.get_fully_signed_local_tx() {