Expose the amount of funds available for claim in ChannelMonitor
[rust-lightning] / lightning / src / chain / channelmonitor.rs
index b2ed3d99de7f39e26c590cecf5e75401d84f2921..30e2793dcb9c2145648e32beadab177d45d24f8d 100644 (file)
@@ -535,6 +535,59 @@ impl_writeable_tlv_based_enum_upgradable!(ChannelMonitorUpdateStep,
        },
 );
 
+/// Details about the balance(s) available for spending once the channel appears on chain.
+///
+/// See [`ChannelMonitor::get_claimable_balances`] for more details on when these will or will not
+/// be provided.
+#[derive(Clone, Debug, PartialEq, Eq)]
+#[cfg_attr(test, derive(PartialOrd, Ord))]
+pub enum Balance {
+       /// The channel is not yet closed (or the commitment or closing transaction has not yet
+       /// appeared in a block). The given balance is claimable (less on-chain fees) if the channel is
+       /// force-closed now.
+       ClaimableOnChannelClose {
+               /// The amount available to claim, in satoshis, excluding the on-chain fees which will be
+               /// required to do so.
+               claimable_amount_satoshis: u64,
+       },
+       /// The channel has been closed, and the given balance is ours but awaiting confirmations until
+       /// we consider it spendable.
+       ClaimableAwaitingConfirmations {
+               /// The amount available to claim, in satoshis, possibly excluding the on-chain fees which
+               /// were spent in broadcasting the transaction.
+               claimable_amount_satoshis: u64,
+               /// The height at which an [`Event::SpendableOutputs`] event will be generated for this
+               /// amount.
+               confirmation_height: u32,
+       },
+       /// The channel has been closed, and the given balance should be ours but awaiting spending
+       /// transaction confirmation. If the spending transaction does not confirm in time, it is
+       /// possible our counterparty can take the funds by broadcasting an HTLC timeout on-chain.
+       ///
+       /// Once the spending transaction confirms, before it has reached enough confirmations to be
+       /// considered safe from chain reorganizations, the balance will instead be provided via
+       /// [`Balance::ClaimableAwaitingConfirmations`].
+       ContentiousClaimable {
+               /// The amount available to claim, in satoshis, excluding the on-chain fees which will be
+               /// required to do so.
+               claimable_amount_satoshis: u64,
+               /// The height at which the counterparty may be able to claim the balance if we have not
+               /// done so.
+               timeout_height: u32,
+       },
+       /// HTLCs which we sent to our counterparty which are claimable after a timeout (less on-chain
+       /// fees) if the counterparty does not know the preimage for the HTLCs. These are somewhat
+       /// likely to be claimed by our counterparty before we do.
+       MaybeClaimableHTLCAwaitingTimeout {
+               /// The amount available to claim, in satoshis, excluding the on-chain fees which will be
+               /// required to do so.
+               claimable_amount_satoshis: u64,
+               /// The height at which we will be able to claim the balance if our counterparty has not
+               /// done so.
+               claimable_height: u32,
+       },
+}
+
 /// An HTLC which has been irrevocably resolved on-chain, and has reached ANTI_REORG_DELAY.
 #[derive(PartialEq)]
 struct IrrevocablyResolvedHTLC {
@@ -1302,6 +1355,173 @@ impl<Signer: Sign> ChannelMonitor<Signer> {
        pub fn current_best_block(&self) -> BestBlock {
                self.inner.lock().unwrap().best_block.clone()
        }
+
+       /// Gets the balances in this channel which are either claimable by us if we were to
+       /// force-close the channel now or which are claimable on-chain (possibly awaiting
+       /// confirmation).
+       ///
+       /// Any balances in the channel which are available on-chain (excluding on-chain fees) are
+       /// included here until an [`Event::SpendableOutputs`] event has been generated for the
+       /// balance, or until our counterparty has claimed the balance and accrued several
+       /// confirmations on the claim transaction.
+       ///
+       /// Note that the balances available when you or your counterparty have broadcasted revoked
+       /// state(s) may not be fully captured here.
+       // TODO, fix that ^
+       ///
+       /// See [`Balance`] for additional details on the types of claimable balances which
+       /// may be returned here and their meanings.
+       pub fn get_claimable_balances(&self) -> Vec<Balance> {
+               let mut res = Vec::new();
+               let us = self.inner.lock().unwrap();
+
+               let mut confirmed_txid = us.funding_spend_confirmed;
+               let mut pending_commitment_tx_conf_thresh = None;
+               let funding_spend_pending = us.onchain_events_awaiting_threshold_conf.iter().find_map(|event| {
+                       if let OnchainEvent::FundingSpendConfirmation { .. } = event.event {
+                               Some((event.txid, event.confirmation_threshold()))
+                       } else { None }
+               });
+               if let Some((txid, conf_thresh)) = funding_spend_pending {
+                       debug_assert!(us.funding_spend_confirmed.is_none(),
+                               "We have a pending funding spend awaiting anti-reorg confirmation, we can't have confirmed it already!");
+                       confirmed_txid = Some(txid);
+                       pending_commitment_tx_conf_thresh = Some(conf_thresh);
+               }
+
+               macro_rules! walk_htlcs {
+                       ($holder_commitment: expr, $htlc_iter: expr) => {
+                               for htlc in $htlc_iter {
+                                       if let Some(htlc_input_idx) = htlc.transaction_output_index {
+                                               if us.htlcs_resolved_on_chain.iter().any(|v| v.input_idx == htlc_input_idx) {
+                                                       assert!(us.funding_spend_confirmed.is_some());
+                                               } else if htlc.offered == $holder_commitment {
+                                                       // If the payment was outbound, check if there's an HTLCUpdate
+                                                       // indicating we have spent this HTLC with a timeout, claiming it back
+                                                       // and awaiting confirmations on it.
+                                                       let htlc_update_pending = us.onchain_events_awaiting_threshold_conf.iter().find_map(|event| {
+                                                               if let OnchainEvent::HTLCUpdate { input_idx: Some(input_idx), .. } = event.event {
+                                                                       if input_idx == htlc_input_idx { Some(event.confirmation_threshold()) } else { None }
+                                                               } else { None }
+                                                       });
+                                                       if let Some(conf_thresh) = htlc_update_pending {
+                                                               res.push(Balance::ClaimableAwaitingConfirmations {
+                                                                       claimable_amount_satoshis: htlc.amount_msat / 1000,
+                                                                       confirmation_height: conf_thresh,
+                                                               });
+                                                       } else {
+                                                               res.push(Balance::MaybeClaimableHTLCAwaitingTimeout {
+                                                                       claimable_amount_satoshis: htlc.amount_msat / 1000,
+                                                                       claimable_height: htlc.cltv_expiry,
+                                                               });
+                                                       }
+                                               } else if us.payment_preimages.get(&htlc.payment_hash).is_some() {
+                                                       // Otherwise (the payment was inbound), only expose it as claimable if
+                                                       // we know the preimage.
+                                                       // Note that if there is a pending claim, but it did not use the
+                                                       // preimage, we lost funds to our counterparty! We will then continue
+                                                       // to show it as ContentiousClaimable until ANTI_REORG_DELAY.
+                                                       let htlc_spend_pending = us.onchain_events_awaiting_threshold_conf.iter().find_map(|event| {
+                                                               if let OnchainEvent::HTLCSpendConfirmation { input_idx, preimage, .. } = event.event {
+                                                                       if input_idx == htlc_input_idx {
+                                                                               Some((event.confirmation_threshold(), preimage.is_some()))
+                                                                       } else { None }
+                                                               } else { None }
+                                                       });
+                                                       if let Some((conf_thresh, true)) = htlc_spend_pending {
+                                                               res.push(Balance::ClaimableAwaitingConfirmations {
+                                                                       claimable_amount_satoshis: htlc.amount_msat / 1000,
+                                                                       confirmation_height: conf_thresh,
+                                                               });
+                                                       } else {
+                                                               res.push(Balance::ContentiousClaimable {
+                                                                       claimable_amount_satoshis: htlc.amount_msat / 1000,
+                                                                       timeout_height: htlc.cltv_expiry,
+                                                               });
+                                                       }
+                                               }
+                                       }
+                               }
+                       }
+               }
+
+               if let Some(txid) = confirmed_txid {
+                       let mut found_commitment_tx = false;
+                       if Some(txid) == us.current_counterparty_commitment_txid || Some(txid) == us.prev_counterparty_commitment_txid {
+                               walk_htlcs!(false, us.counterparty_claimable_outpoints.get(&txid).unwrap().iter().map(|(a, _)| a));
+                               if let Some(conf_thresh) = pending_commitment_tx_conf_thresh {
+                                       if let Some(value) = us.onchain_events_awaiting_threshold_conf.iter().find_map(|event| {
+                                               if let OnchainEvent::MaturingOutput {
+                                                       descriptor: SpendableOutputDescriptor::StaticPaymentOutput(descriptor)
+                                               } = &event.event {
+                                                       Some(descriptor.output.value)
+                                               } else { None }
+                                       }) {
+                                               res.push(Balance::ClaimableAwaitingConfirmations {
+                                                       claimable_amount_satoshis: value,
+                                                       confirmation_height: conf_thresh,
+                                               });
+                                       } else {
+                                               // If a counterparty commitment transaction is awaiting confirmation, we
+                                               // should either have a StaticPaymentOutput MaturingOutput event awaiting
+                                               // confirmation with the same height or have never met our dust amount.
+                                       }
+                               }
+                               found_commitment_tx = true;
+                       } else if txid == us.current_holder_commitment_tx.txid {
+                               walk_htlcs!(true, us.current_holder_commitment_tx.htlc_outputs.iter().map(|(a, _, _)| a));
+                               if let Some(conf_thresh) = pending_commitment_tx_conf_thresh {
+                                       res.push(Balance::ClaimableAwaitingConfirmations {
+                                               claimable_amount_satoshis: us.current_holder_commitment_tx.to_self_value_sat,
+                                               confirmation_height: conf_thresh,
+                                       });
+                               }
+                               found_commitment_tx = true;
+                       } else if let Some(prev_commitment) = &us.prev_holder_signed_commitment_tx {
+                               if txid == prev_commitment.txid {
+                                       walk_htlcs!(true, prev_commitment.htlc_outputs.iter().map(|(a, _, _)| a));
+                                       if let Some(conf_thresh) = pending_commitment_tx_conf_thresh {
+                                               res.push(Balance::ClaimableAwaitingConfirmations {
+                                                       claimable_amount_satoshis: prev_commitment.to_self_value_sat,
+                                                       confirmation_height: conf_thresh,
+                                               });
+                                       }
+                                       found_commitment_tx = true;
+                               }
+                       }
+                       if !found_commitment_tx {
+                               if let Some(conf_thresh) = pending_commitment_tx_conf_thresh {
+                                       // We blindly assume this is a cooperative close transaction here, and that
+                                       // neither us nor our counterparty misbehaved. At worst we've under-estimated
+                                       // the amount we can claim as we'll punish a misbehaving counterparty.
+                                       res.push(Balance::ClaimableAwaitingConfirmations {
+                                               claimable_amount_satoshis: us.current_holder_commitment_tx.to_self_value_sat,
+                                               confirmation_height: conf_thresh,
+                                       });
+                               }
+                       }
+                       // TODO: Add logic to provide claimable balances for counterparty broadcasting revoked
+                       // outputs.
+               } else {
+                       let mut claimable_inbound_htlc_value_sat = 0;
+                       for (htlc, _, _) in us.current_holder_commitment_tx.htlc_outputs.iter() {
+                               if htlc.transaction_output_index.is_none() { continue; }
+                               if htlc.offered {
+                                       res.push(Balance::MaybeClaimableHTLCAwaitingTimeout {
+                                               claimable_amount_satoshis: htlc.amount_msat / 1000,
+                                               claimable_height: htlc.cltv_expiry,
+                                       });
+                               } else if us.payment_preimages.get(&htlc.payment_hash).is_some() {
+                                       claimable_inbound_htlc_value_sat += htlc.amount_msat / 1000;
+                               }
+                       }
+                       res.push(Balance::ClaimableOnChannelClose {
+                               claimable_amount_satoshis: us.current_holder_commitment_tx.to_self_value_sat + claimable_inbound_htlc_value_sat,
+                       });
+               }
+
+               res
+       }
 }
 
 /// Compares a broadcasted commitment transaction's HTLCs with those in the latest state,
@@ -2488,7 +2708,7 @@ impl<Signer: Sign> ChannelMonitorImpl<Signer> {
                                                                        // we've already failed the HTLC as the commitment transaction
                                                                        // which was broadcasted was revoked. In that case, we should
                                                                        // spend the HTLC output here immediately, and expose that fact
-                                                                       // as a ClaimableBalance, something which we do not yet do.
+                                                                       // as a Balance, something which we do not yet do.
                                                                        // TODO: Track the above as claimable!
                                                                }
                                                                continue 'outer_loop;