Provide commitment point to monitor with the remote txn update

This extends 1b33064 by
re-simplifying the ChannelMonitor <-> Channel interface a bit as we
never have any use for the latest remote commitment point until we
have knowledge of a remote transaction generated using it.

Author: TheBlueMatt

src/ln/channel.rs

@@ -633,7 +633,6 @@ impl Channel {
 		                                              &chan_keys.htlc_base_key, &chan_keys.payment_base_key, &keys_provider.get_shutdown_pubkey(), BREAKDOWN_TIMEOUT,
 		                                              keys_provider.get_destination_script(), logger.clone());
 		channel_monitor.set_their_base_keys(&msg.htlc_basepoint, &msg.delayed_payment_basepoint);
-		channel_monitor.provide_their_next_revocation_point(Some((INITIAL_COMMITMENT_NUMBER, msg.first_per_commitment_point)));
 		channel_monitor.set_their_to_self_delay(msg.to_self_delay);
 
 		let mut chan = Channel {
@@ -1358,7 +1357,6 @@ impl Channel {
 		}
 
 		self.channel_monitor.set_their_base_keys(&msg.htlc_basepoint, &msg.delayed_payment_basepoint);
-		self.channel_monitor.provide_their_next_revocation_point(Some((INITIAL_COMMITMENT_NUMBER, msg.first_per_commitment_point)));
 
 		self.their_dust_limit_satoshis = msg.dust_limit_satoshis;
 		self.their_max_htlc_value_in_flight_msat = cmp::min(msg.max_htlc_value_in_flight_msat, self.channel_value_satoshis * 1000);
@@ -1434,7 +1432,7 @@ impl Channel {
 
 		// Now that we're past error-generating stuff, update our local state:
 
-		self.channel_monitor.provide_latest_remote_commitment_tx_info(&remote_initial_commitment_tx, Vec::new(), self.cur_remote_commitment_transaction_number);
+		self.channel_monitor.provide_latest_remote_commitment_tx_info(&remote_initial_commitment_tx, Vec::new(), self.cur_remote_commitment_transaction_number, self.their_cur_commitment_point.unwrap());
 		self.last_local_commitment_txn = vec![local_initial_commitment_tx.clone()];
 		self.channel_monitor.provide_latest_local_commitment_tx_info(local_initial_commitment_tx, local_keys, self.feerate_per_kw, Vec::new());
 		self.channel_state = ChannelState::FundingSent as u32;
@@ -1506,7 +1504,6 @@ impl Channel {
 			return Err(ChannelError::Close("Peer sent a funding_locked at a strange time"));
 		}
 
-		self.channel_monitor.provide_their_next_revocation_point(Some((INITIAL_COMMITMENT_NUMBER - 1 , msg.next_per_commitment_point)));
 		self.their_prev_commitment_point = self.their_cur_commitment_point;
 		self.their_cur_commitment_point = Some(msg.next_per_commitment_point);
 		Ok(())
@@ -1901,7 +1898,6 @@ impl Channel {
 		}
 		self.channel_monitor.provide_secret(self.cur_remote_commitment_transaction_number + 1, msg.per_commitment_secret)
 			.map_err(|e| ChannelError::Close(e.0))?;
-		self.channel_monitor.provide_their_next_revocation_point(Some((self.cur_remote_commitment_transaction_number - 1, msg.next_per_commitment_point)));
 
 		// Update state now that we've passed all the can-fail calls...
 		// (note that we may still fail to generate the new commitment_signed message, but that's
@@ -3002,7 +2998,7 @@ impl Channel {
 		let temporary_channel_id = self.channel_id;
 
 		// Now that we're past error-generating stuff, update our local state:
-		self.channel_monitor.provide_latest_remote_commitment_tx_info(&commitment_tx, Vec::new(), self.cur_remote_commitment_transaction_number);
+		self.channel_monitor.provide_latest_remote_commitment_tx_info(&commitment_tx, Vec::new(), self.cur_remote_commitment_transaction_number, self.their_cur_commitment_point.unwrap());
 		self.channel_state = ChannelState::FundingCreated as u32;
 		self.channel_id = funding_txo.to_channel_id();
 		self.cur_remote_commitment_transaction_number -= 1;
@@ -3214,7 +3210,7 @@ impl Channel {
 		match self.send_commitment_no_state_update() {
 			Ok((res, remote_commitment_tx)) => {
 				// Update state now that we've passed all the can-fail calls...
-				self.channel_monitor.provide_latest_remote_commitment_tx_info(&remote_commitment_tx.0, remote_commitment_tx.1, self.cur_remote_commitment_transaction_number);
+				self.channel_monitor.provide_latest_remote_commitment_tx_info(&remote_commitment_tx.0, remote_commitment_tx.1, self.cur_remote_commitment_transaction_number, self.their_cur_commitment_point.unwrap());
 				self.channel_state |= ChannelState::AwaitingRemoteRevoke as u32;
 				Ok((res, self.channel_monitor.clone()))
 			},

src/ln/channelmonitor.rs

@@ -461,37 +461,11 @@ impl ChannelMonitor {
 		Ok(())
 	}
 
-	/// Tracks the next revocation point which may be required to claim HTLC outputs which we know
-	/// the preimage of in case the remote end force-closes using their latest state. When called at
-	/// channel opening revocation point is the CURRENT one used for first commitment tx. Needed in case of sizeable push_msat.
-	pub(super) fn provide_their_next_revocation_point(&mut self, their_next_revocation_point: Option<(u64, PublicKey)>) {
-		if let Some(new_revocation_point) = their_next_revocation_point {
-			match self.their_cur_revocation_points {
-				Some(old_points) => {
-					if old_points.0 == new_revocation_point.0 + 1 {
-						self.their_cur_revocation_points = Some((old_points.0, old_points.1, Some(new_revocation_point.1)));
-					} else if old_points.0 == new_revocation_point.0 + 2 {
-						if let Some(old_second_point) = old_points.2 {
-							self.their_cur_revocation_points = Some((old_points.0 - 1, old_second_point, Some(new_revocation_point.1)));
-						} else {
-							self.their_cur_revocation_points = Some((new_revocation_point.0, new_revocation_point.1, None));
-						}
-					} else {
-						self.their_cur_revocation_points = Some((new_revocation_point.0, new_revocation_point.1, None));
-					}
-				},
-				None => {
-					self.their_cur_revocation_points = Some((new_revocation_point.0, new_revocation_point.1, None));
-				}
-			}
-		}
-	}
-
 	/// Informs this monitor of the latest remote (ie non-broadcastable) commitment transaction.
 	/// The monitor watches for it to be broadcasted and then uses the HTLC information (and
 	/// possibly future revocation/preimage information) to claim outputs where possible.
 	/// We cache also the mapping hash:commitment number to lighten pruning of old preimages by watchtowers.
-	pub(super) fn provide_latest_remote_commitment_tx_info(&mut self, unsigned_commitment_tx: &Transaction, htlc_outputs: Vec<HTLCOutputInCommitment>, commitment_number: u64) {
+	pub(super) fn provide_latest_remote_commitment_tx_info(&mut self, unsigned_commitment_tx: &Transaction, htlc_outputs: Vec<HTLCOutputInCommitment>, commitment_number: u64, their_revocation_point: PublicKey) {
 		// TODO: Encrypt the htlc_outputs data with the single-hash of the commitment transaction
 		// so that a remote monitor doesn't learn anything unless there is a malicious close.
 		// (only maybe, sadly we cant do the same for local info, as we need to be aware of
@@ -501,6 +475,25 @@ impl ChannelMonitor {
 		}
 		self.remote_claimable_outpoints.insert(unsigned_commitment_tx.txid(), htlc_outputs);
 		self.current_remote_commitment_number = commitment_number;
+		//TODO: Merge this into the other per-remote-transaction output storage stuff
+		match self.their_cur_revocation_points {
+			Some(old_points) => {
+				if old_points.0 == commitment_number + 1 {
+					self.their_cur_revocation_points = Some((old_points.0, old_points.1, Some(their_revocation_point)));
+				} else if old_points.0 == commitment_number + 2 {
+					if let Some(old_second_point) = old_points.2 {
+						self.their_cur_revocation_points = Some((old_points.0 - 1, old_second_point, Some(their_revocation_point)));
+					} else {
+						self.their_cur_revocation_points = Some((commitment_number, their_revocation_point, None));
+					}
+				} else {
+					self.their_cur_revocation_points = Some((commitment_number, their_revocation_point, None));
+				}
+			},
+			None => {
+				self.their_cur_revocation_points = Some((commitment_number, their_revocation_point, None));
+			}
+		}
 	}
 
 	/// Informs this monitor of the latest local (ie broadcastable) commitment transaction. The
@@ -2161,10 +2154,10 @@ mod tests {
 		let logger = Arc::new(TestLogger::new());
 		let dummy_sig = Signature::from_der(&secp_ctx, &hex::decode("3045022100fa86fa9a36a8cd6a7bb8f06a541787d51371d067951a9461d5404de6b928782e02201c8b7c334c10aed8976a3a465be9a28abff4cb23acbf00022295b378ce1fa3cd").unwrap()[..]).unwrap();
 
+		let dummy_key = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&secp_ctx, &[42; 32]).unwrap());
 		macro_rules! dummy_keys {
 			() => {
 				{
-					let dummy_key = PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&secp_ctx, &[42; 32]).unwrap());
 					TxCreationKeys {
 						per_commitment_point: dummy_key.clone(),
 						revocation_key: dummy_key.clone(),
@@ -2233,10 +2226,10 @@ mod tests {
 		monitor.set_their_to_self_delay(10);
 
 		monitor.provide_latest_local_commitment_tx_info(dummy_tx.clone(), dummy_keys!(), 0, preimages_to_local_htlcs!(preimages[0..10]));
-		monitor.provide_latest_remote_commitment_tx_info(&dummy_tx, preimages_slice_to_htlc_outputs!(preimages[5..15]), 281474976710655);
-		monitor.provide_latest_remote_commitment_tx_info(&dummy_tx, preimages_slice_to_htlc_outputs!(preimages[15..20]), 281474976710654);
-		monitor.provide_latest_remote_commitment_tx_info(&dummy_tx, preimages_slice_to_htlc_outputs!(preimages[17..20]), 281474976710653);
-		monitor.provide_latest_remote_commitment_tx_info(&dummy_tx, preimages_slice_to_htlc_outputs!(preimages[18..20]), 281474976710652);
+		monitor.provide_latest_remote_commitment_tx_info(&dummy_tx, preimages_slice_to_htlc_outputs!(preimages[5..15]), 281474976710655, dummy_key);
+		monitor.provide_latest_remote_commitment_tx_info(&dummy_tx, preimages_slice_to_htlc_outputs!(preimages[15..20]), 281474976710654, dummy_key);
+		monitor.provide_latest_remote_commitment_tx_info(&dummy_tx, preimages_slice_to_htlc_outputs!(preimages[17..20]), 281474976710653, dummy_key);
+		monitor.provide_latest_remote_commitment_tx_info(&dummy_tx, preimages_slice_to_htlc_outputs!(preimages[18..20]), 281474976710652, dummy_key);
 		for &(ref preimage, ref hash) in preimages.iter() {
 			monitor.provide_payment_preimage(hash, preimage);
 		}