Automatically update fees on outbound channels as fees change
[rust-lightning] / lightning / src / ln / channel.rs
index 78f08ca5366696f5452410b6f731ec67ac09e95a..dc09dc8242f9e43fd390ab75f3a66c73f5765563 100644 (file)
@@ -275,6 +275,14 @@ enum HTLCInitiator {
        RemoteOffered,
 }
 
+/// An enum gathering stats on pending HTLCs, either inbound or outbound side.
+struct HTLCStats {
+       pending_htlcs: u32,
+       pending_htlcs_value_msat: u64,
+       on_counterparty_tx_dust_exposure_msat: u64,
+       on_holder_tx_dust_exposure_msat: u64,
+}
+
 /// Used when calculating whether we or the remote can afford an additional HTLC.
 struct HTLCCandidate {
        amount_msat: u64,
@@ -607,8 +615,8 @@ impl<Signer: Sign> Channel<Signer> {
                } else { None };
 
                if let Some(shutdown_scriptpubkey) = &shutdown_scriptpubkey {
-                       if !shutdown_scriptpubkey.is_compatible(their_features) {
-                               return Err(APIError::APIMisuseError { err: format!("Provided a scriptpubkey format not accepted by peer. script: ({})", shutdown_scriptpubkey.clone().into_inner().to_bytes().to_hex()) });
+                       if !shutdown_scriptpubkey.is_compatible(&their_features) {
+                               return Err(APIError::IncompatibleShutdownScript { script: shutdown_scriptpubkey.clone() });
                        }
                }
 
@@ -843,7 +851,7 @@ impl<Signer: Sign> Channel<Signer> {
                                        } else {
                                                match ShutdownScript::try_from((script.clone(), their_features)) {
                                                        Ok(shutdown_script) => Some(shutdown_script.into_inner()),
-                                                       Err(_) => return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format. script: ({})", script.to_bytes().to_hex()))),
+                                                       Err(_) => return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format: {}", script))),
                                                }
                                        }
                                },
@@ -860,7 +868,7 @@ impl<Signer: Sign> Channel<Signer> {
 
                if let Some(shutdown_scriptpubkey) = &shutdown_scriptpubkey {
                        if !shutdown_scriptpubkey.is_compatible(&their_features) {
-                               return Err(ChannelError::Close(format!("Provided a scriptpubkey format not accepted by peer. script: ({})", shutdown_scriptpubkey.clone().into_inner().to_bytes().to_hex())));
+                               return Err(ChannelError::Close(format!("Provided a scriptpubkey format not accepted by peer: {}", shutdown_scriptpubkey)));
                        }
                }
 
@@ -1587,7 +1595,7 @@ impl<Signer: Sign> Channel<Signer> {
                                        } else {
                                                match ShutdownScript::try_from((script.clone(), their_features)) {
                                                        Ok(shutdown_script) => Some(shutdown_script.into_inner()),
-                                                       Err(_) => return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format. script: ({})", script.to_bytes().to_hex()))),
+                                                       Err(_) => return Err(ChannelError::Close(format!("Peer is signaling upfront_shutdown but has provided an unacceptable scriptpubkey format: {}", script))),
                                                }
                                        }
                                },
@@ -1842,32 +1850,63 @@ impl<Signer: Sign> Channel<Signer> {
                Ok(())
        }
 
-       /// Returns (inbound_htlc_count, htlc_inbound_value_msat)
-       fn get_inbound_pending_htlc_stats(&self) -> (u32, u64) {
-               let mut htlc_inbound_value_msat = 0;
+       /// Returns a HTLCStats about inbound pending htlcs
+       fn get_inbound_pending_htlc_stats(&self) -> HTLCStats {
+               let mut stats = HTLCStats {
+                       pending_htlcs: self.pending_inbound_htlcs.len() as u32,
+                       pending_htlcs_value_msat: 0,
+                       on_counterparty_tx_dust_exposure_msat: 0,
+                       on_holder_tx_dust_exposure_msat: 0,
+               };
+
+               let counterparty_dust_limit_timeout_sat = (self.get_dust_buffer_feerate() as u64 * HTLC_TIMEOUT_TX_WEIGHT / 1000) + self.counterparty_dust_limit_satoshis;
+               let holder_dust_limit_success_sat = (self.get_dust_buffer_feerate() as u64 * HTLC_SUCCESS_TX_WEIGHT / 1000) + self.holder_dust_limit_satoshis;
                for ref htlc in self.pending_inbound_htlcs.iter() {
-                       htlc_inbound_value_msat += htlc.amount_msat;
+                       stats.pending_htlcs_value_msat += htlc.amount_msat;
+                       if htlc.amount_msat / 1000 < counterparty_dust_limit_timeout_sat {
+                               stats.on_counterparty_tx_dust_exposure_msat += htlc.amount_msat;
+                       }
+                       if htlc.amount_msat / 1000 < holder_dust_limit_success_sat {
+                               stats.on_holder_tx_dust_exposure_msat += htlc.amount_msat;
+                       }
                }
-               (self.pending_inbound_htlcs.len() as u32, htlc_inbound_value_msat)
+               stats
        }
 
-       /// Returns (outbound_htlc_count, htlc_outbound_value_msat) *including* pending adds in our
-       /// holding cell.
-       fn get_outbound_pending_htlc_stats(&self) -> (u32, u64) {
-               let mut htlc_outbound_value_msat = 0;
+       /// Returns a HTLCStats about pending outbound htlcs, *including* pending adds in our holding cell.
+       fn get_outbound_pending_htlc_stats(&self) -> HTLCStats {
+               let mut stats = HTLCStats {
+                       pending_htlcs: self.pending_outbound_htlcs.len() as u32,
+                       pending_htlcs_value_msat: 0,
+                       on_counterparty_tx_dust_exposure_msat: 0,
+                       on_holder_tx_dust_exposure_msat: 0,
+               };
+
+               let counterparty_dust_limit_success_sat = (self.get_dust_buffer_feerate() as u64 * HTLC_SUCCESS_TX_WEIGHT / 1000) + self.counterparty_dust_limit_satoshis;
+               let holder_dust_limit_timeout_sat = (self.get_dust_buffer_feerate() as u64 * HTLC_TIMEOUT_TX_WEIGHT / 1000) + self.holder_dust_limit_satoshis;
                for ref htlc in self.pending_outbound_htlcs.iter() {
-                       htlc_outbound_value_msat += htlc.amount_msat;
+                       stats.pending_htlcs_value_msat += htlc.amount_msat;
+                       if htlc.amount_msat / 1000 < counterparty_dust_limit_success_sat {
+                               stats.on_counterparty_tx_dust_exposure_msat += htlc.amount_msat;
+                       }
+                       if htlc.amount_msat / 1000 < holder_dust_limit_timeout_sat {
+                               stats.on_holder_tx_dust_exposure_msat += htlc.amount_msat;
+                       }
                }
 
-               let mut htlc_outbound_count = self.pending_outbound_htlcs.len();
                for update in self.holding_cell_htlc_updates.iter() {
                        if let &HTLCUpdateAwaitingACK::AddHTLC { ref amount_msat, .. } = update {
-                               htlc_outbound_count += 1;
-                               htlc_outbound_value_msat += amount_msat;
+                               stats.pending_htlcs += 1;
+                               stats.pending_htlcs_value_msat += amount_msat;
+                               if *amount_msat / 1000 < counterparty_dust_limit_success_sat {
+                                       stats.on_counterparty_tx_dust_exposure_msat += amount_msat;
+                               }
+                               if *amount_msat / 1000 < holder_dust_limit_timeout_sat {
+                                       stats.on_holder_tx_dust_exposure_msat += amount_msat;
+                               }
                        }
                }
-
-               (htlc_outbound_count as u32, htlc_outbound_value_msat)
+               stats
        }
 
        /// Get the available (ie not including pending HTLCs) inbound and outbound balance in msat.
@@ -1879,11 +1918,11 @@ impl<Signer: Sign> Channel<Signer> {
                (
                        cmp::max(self.channel_value_satoshis as i64 * 1000
                                - self.value_to_self_msat as i64
-                               - self.get_inbound_pending_htlc_stats().1 as i64
+                               - self.get_inbound_pending_htlc_stats().pending_htlcs_value_msat as i64
                                - Self::get_holder_selected_channel_reserve_satoshis(self.channel_value_satoshis) as i64 * 1000,
                        0) as u64,
                        cmp::max(self.value_to_self_msat as i64
-                               - self.get_outbound_pending_htlc_stats().1 as i64
+                               - self.get_outbound_pending_htlc_stats().pending_htlcs_value_msat as i64
                                - self.counterparty_selected_channel_reserve_satoshis.unwrap_or(0) as i64 * 1000,
                        0) as u64
                )
@@ -2095,12 +2134,13 @@ impl<Signer: Sign> Channel<Signer> {
                        return Err(ChannelError::Close(format!("Remote side tried to send less than our minimum HTLC value. Lower limit: ({}). Actual: ({})", self.holder_htlc_minimum_msat, msg.amount_msat)));
                }
 
-               let (inbound_htlc_count, htlc_inbound_value_msat) = self.get_inbound_pending_htlc_stats();
-               if inbound_htlc_count + 1 > OUR_MAX_HTLCS as u32 {
+               let inbound_stats = self.get_inbound_pending_htlc_stats();
+               let outbound_stats = self.get_outbound_pending_htlc_stats();
+               if inbound_stats.pending_htlcs + 1 > OUR_MAX_HTLCS as u32 {
                        return Err(ChannelError::Close(format!("Remote tried to push more than our max accepted HTLCs ({})", OUR_MAX_HTLCS)));
                }
                let holder_max_htlc_value_in_flight_msat = Channel::<Signer>::get_holder_max_htlc_value_in_flight_msat(self.channel_value_satoshis);
-               if htlc_inbound_value_msat + msg.amount_msat > holder_max_htlc_value_in_flight_msat {
+               if inbound_stats.pending_htlcs_value_msat + msg.amount_msat > holder_max_htlc_value_in_flight_msat {
                        return Err(ChannelError::Close(format!("Remote HTLC add would put them over our max HTLC value ({})", holder_max_htlc_value_in_flight_msat)));
                }
                // Check holder_selected_channel_reserve_satoshis (we're getting paid, so they have to at least meet
@@ -2124,8 +2164,28 @@ impl<Signer: Sign> Channel<Signer> {
                        }
                }
 
+               let exposure_dust_limit_timeout_sats = (self.get_dust_buffer_feerate() as u64 * HTLC_TIMEOUT_TX_WEIGHT / 1000) + self.counterparty_dust_limit_satoshis;
+               if msg.amount_msat / 1000 < exposure_dust_limit_timeout_sats {
+                       let on_counterparty_tx_dust_htlc_exposure_msat = inbound_stats.on_counterparty_tx_dust_exposure_msat + outbound_stats.on_counterparty_tx_dust_exposure_msat + msg.amount_msat;
+                       if on_counterparty_tx_dust_htlc_exposure_msat > self.get_max_dust_htlc_exposure_msat() {
+                               log_info!(logger, "Cannot accept value that would put our exposure to dust HTLCs at {} over the limit {} on counterparty commitment tx",
+                                       on_counterparty_tx_dust_htlc_exposure_msat, self.get_max_dust_htlc_exposure_msat());
+                               pending_forward_status = create_pending_htlc_status(self, pending_forward_status, 0x1000|7);
+                       }
+               }
+
+               let exposure_dust_limit_success_sats = (self.get_dust_buffer_feerate() as u64 * HTLC_SUCCESS_TX_WEIGHT / 1000) + self.holder_dust_limit_satoshis;
+               if msg.amount_msat / 1000 < exposure_dust_limit_success_sats {
+                       let on_holder_tx_dust_htlc_exposure_msat = inbound_stats.on_holder_tx_dust_exposure_msat + outbound_stats.on_holder_tx_dust_exposure_msat + msg.amount_msat;
+                       if on_holder_tx_dust_htlc_exposure_msat > self.get_max_dust_htlc_exposure_msat() {
+                               log_info!(logger, "Cannot accept value that would put our exposure to dust HTLCs at {} over the limit {} on holder commitment tx",
+                                       on_holder_tx_dust_htlc_exposure_msat, self.get_max_dust_htlc_exposure_msat());
+                               pending_forward_status = create_pending_htlc_status(self, pending_forward_status, 0x1000|7);
+                       }
+               }
+
                let pending_value_to_self_msat =
-                       self.value_to_self_msat + htlc_inbound_value_msat - removed_outbound_total_msat;
+                       self.value_to_self_msat + inbound_stats.pending_htlcs_value_msat - removed_outbound_total_msat;
                let pending_remote_value_msat =
                        self.channel_value_satoshis * 1000 - pending_value_to_self_msat;
                if pending_remote_value_msat < msg.amount_msat {
@@ -2845,7 +2905,7 @@ impl<Signer: Sign> Channel<Signer> {
                        panic!("Cannot update fee while peer is disconnected/we're awaiting a monitor update (ChannelManager should have caught this)");
                }
 
-               if (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32)) == (ChannelState::AwaitingRemoteRevoke as u32) {
+               if (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32 | ChannelState::MonitorUpdateFailed as u32)) != 0 {
                        self.holding_cell_update_fee = Some(feerate_per_kw);
                        return None;
                }
@@ -3295,7 +3355,7 @@ impl<Signer: Sign> Channel<Signer> {
                                assert!(send_shutdown);
                                let shutdown_scriptpubkey = keys_provider.get_shutdown_scriptpubkey();
                                if !shutdown_scriptpubkey.is_compatible(their_features) {
-                                       return Err(ChannelError::Close(format!("Provided a scriptpubkey format not accepted by peer. script: ({})", shutdown_scriptpubkey.clone().into_inner().to_bytes().to_hex())));
+                                       return Err(ChannelError::Close(format!("Provided a scriptpubkey format not accepted by peer: {}", shutdown_scriptpubkey)));
                                }
                                self.shutdown_scriptpubkey = Some(shutdown_scriptpubkey);
                                true
@@ -3558,11 +3618,23 @@ impl<Signer: Sign> Channel<Signer> {
                cmp::max(self.config.cltv_expiry_delta, MIN_CLTV_EXPIRY_DELTA)
        }
 
-       #[cfg(test)]
+       pub fn get_max_dust_htlc_exposure_msat(&self) -> u64 {
+               self.config.max_dust_htlc_exposure_msat
+       }
+
        pub fn get_feerate(&self) -> u32 {
                self.feerate_per_kw
        }
 
+       pub fn get_dust_buffer_feerate(&self) -> u32 {
+               // When calculating our exposure to dust HTLCs, we assume that the channel feerate
+               // may, at any point, increase by at least 10 sat/vB (i.e 2530 sat/kWU) or 25%,
+               // whichever is higher. This ensures that we aren't suddenly exposed to significantly
+               // more dust balance if the feerate increases when we have several HTLCs pending
+               // which are near the dust limit.
+               cmp::max(2530, self.feerate_per_kw * 1250 / 1000)
+       }
+
        pub fn get_cur_holder_commitment_transaction_number(&self) -> u64 {
                self.cur_holder_commitment_transaction_number + 1
        }
@@ -4207,12 +4279,13 @@ impl<Signer: Sign> Channel<Signer> {
                        return Err(ChannelError::Ignore("Cannot send an HTLC while disconnected from channel counterparty".to_owned()));
                }
 
-               let (outbound_htlc_count, htlc_outbound_value_msat) = self.get_outbound_pending_htlc_stats();
-               if outbound_htlc_count + 1 > self.counterparty_max_accepted_htlcs as u32 {
+               let inbound_stats = self.get_inbound_pending_htlc_stats();
+               let outbound_stats = self.get_outbound_pending_htlc_stats();
+               if outbound_stats.pending_htlcs + 1 > self.counterparty_max_accepted_htlcs as u32 {
                        return Err(ChannelError::Ignore(format!("Cannot push more than their max accepted HTLCs ({})", self.counterparty_max_accepted_htlcs)));
                }
                // Check their_max_htlc_value_in_flight_msat
-               if htlc_outbound_value_msat + amount_msat > self.counterparty_max_htlc_value_in_flight_msat {
+               if outbound_stats.pending_htlcs_value_msat + amount_msat > self.counterparty_max_htlc_value_in_flight_msat {
                        return Err(ChannelError::Ignore(format!("Cannot send value that would put us over the max HTLC value in flight our peer will accept ({})", self.counterparty_max_htlc_value_in_flight_msat)));
                }
 
@@ -4227,7 +4300,25 @@ impl<Signer: Sign> Channel<Signer> {
                        }
                }
 
-               let pending_value_to_self_msat = self.value_to_self_msat - htlc_outbound_value_msat;
+               let exposure_dust_limit_success_sats = (self.get_dust_buffer_feerate() as u64 * HTLC_SUCCESS_TX_WEIGHT / 1000) + self.counterparty_dust_limit_satoshis;
+               if amount_msat / 1000 < exposure_dust_limit_success_sats {
+                       let on_counterparty_dust_htlc_exposure_msat = inbound_stats.on_counterparty_tx_dust_exposure_msat + outbound_stats.on_counterparty_tx_dust_exposure_msat + amount_msat;
+                       if on_counterparty_dust_htlc_exposure_msat > self.get_max_dust_htlc_exposure_msat() {
+                               return Err(ChannelError::Ignore(format!("Cannot send value that would put our exposure to dust HTLCs at {} over the limit {} on counterparty commitment tx",
+                                       on_counterparty_dust_htlc_exposure_msat, self.get_max_dust_htlc_exposure_msat())));
+                       }
+               }
+
+               let exposure_dust_limit_timeout_sats = (self.get_dust_buffer_feerate() as u64 * HTLC_TIMEOUT_TX_WEIGHT / 1000) + self.holder_dust_limit_satoshis;
+               if amount_msat / 1000 <  exposure_dust_limit_timeout_sats {
+                       let on_holder_dust_htlc_exposure_msat = inbound_stats.on_holder_tx_dust_exposure_msat + outbound_stats.on_holder_tx_dust_exposure_msat + amount_msat;
+                       if on_holder_dust_htlc_exposure_msat > self.get_max_dust_htlc_exposure_msat() {
+                               return Err(ChannelError::Ignore(format!("Cannot send value that would put our exposure to dust HTLCs at {} over the limit {} on holder commitment tx",
+                                       on_holder_dust_htlc_exposure_msat, self.get_max_dust_htlc_exposure_msat())));
+                       }
+               }
+
+               let pending_value_to_self_msat = self.value_to_self_msat - outbound_stats.pending_htlcs_value_msat;
                if pending_value_to_self_msat < amount_msat {
                        return Err(ChannelError::Ignore(format!("Cannot send value that would overdraw remaining funds. Amount: {}, pending value to self {}", amount_msat, pending_value_to_self_msat)));
                }
@@ -4487,7 +4578,7 @@ impl<Signer: Sign> Channel<Signer> {
                        None => {
                                let shutdown_scriptpubkey = keys_provider.get_shutdown_scriptpubkey();
                                if !shutdown_scriptpubkey.is_compatible(their_features) {
-                                       return Err(APIError::APIMisuseError { err: format!("Provided a scriptpubkey format not accepted by peer. script: ({})", shutdown_scriptpubkey.clone().into_inner().to_bytes().to_hex()) });
+                                       return Err(APIError::IncompatibleShutdownScript { script: shutdown_scriptpubkey.clone() });
                                }
                                self.shutdown_scriptpubkey = Some(shutdown_scriptpubkey);
                                true
@@ -5253,15 +5344,17 @@ mod tests {
                let seed = [42; 32];
                let network = Network::Testnet;
                let keys_provider = test_utils::TestKeysInterface::new(&seed, network);
-               keys_provider.expect(OnGetShutdownScriptpubkey { returns: non_v0_segwit_shutdown_script });
+               keys_provider.expect(OnGetShutdownScriptpubkey {
+                       returns: non_v0_segwit_shutdown_script.clone(),
+               });
 
                let fee_estimator = TestFeeEstimator { fee_est: 253 };
                let secp_ctx = Secp256k1::new();
                let node_id = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[42; 32]).unwrap());
                let config = UserConfig::default();
                match Channel::<EnforcingSigner>::new_outbound(&&fee_estimator, &&keys_provider, node_id, &features, 10000000, 100000, 42, &config) {
-                       Err(APIError::APIMisuseError { err }) => {
-                               assert_eq!(err, "Provided a scriptpubkey format not accepted by peer. script: (60020028)");
+                       Err(APIError::IncompatibleShutdownScript { script }) => {
+                               assert_eq!(script.into_inner(), non_v0_segwit_shutdown_script.into_inner());
                        },
                        Err(e) => panic!("Unexpected error: {:?}", e),
                        Ok(_) => panic!("Expected error"),