Merge pull request #967 from valentinewallace/2021-06-keysend
[rust-lightning] / lightning / src / ln / channelmanager.rs
index 22a7982b1de4a26a8136557a01f35685be7eba9e..1fbdde870095576edba2505addfcb91f6d0f9077 100644 (file)
@@ -99,6 +99,10 @@ enum PendingHTLCRouting {
                payment_data: msgs::FinalOnionHopData,
                incoming_cltv_expiry: u32, // Used to track when we should expire pending HTLCs that go unclaimed
        },
+       ReceiveKeysend {
+               payment_preimage: PaymentPreimage,
+               incoming_cltv_expiry: u32, // Used to track when we should expire pending HTLCs that go unclaimed
+       },
 }
 
 #[derive(Clone)] // See Channel::revoke_and_ack for why, tl;dr: Rust bug
@@ -153,14 +157,20 @@ pub(crate) struct HTLCPreviousHopData {
        outpoint: OutPoint,
 }
 
-struct ClaimableHTLC {
-       prev_hop: HTLCPreviousHopData,
-       value: u64,
+enum OnionPayload {
        /// Contains a total_msat (which may differ from value if this is a Multi-Path Payment) and a
        /// payment_secret which prevents path-probing attacks and can associate different HTLCs which
        /// are part of the same payment.
-       payment_data: msgs::FinalOnionHopData,
+       Invoice(msgs::FinalOnionHopData),
+       /// Contains the payer-provided preimage.
+       Spontaneous(PaymentPreimage),
+}
+
+struct ClaimableHTLC {
+       prev_hop: HTLCPreviousHopData,
        cltv_expiry: u32,
+       value: u64,
+       onion_payload: OnionPayload,
 }
 
 /// Tracks the inbound corresponding to an outbound HTLC
@@ -1437,121 +1447,141 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                };
 
                let pending_forward_info = if next_hop_hmac == [0; 32] {
-                               #[cfg(test)]
-                               {
-                                       // In tests, make sure that the initial onion pcket data is, at least, non-0.
-                                       // We could do some fancy randomness test here, but, ehh, whatever.
-                                       // This checks for the issue where you can calculate the path length given the
-                                       // onion data as all the path entries that the originator sent will be here
-                                       // as-is (and were originally 0s).
-                                       // Of course reverse path calculation is still pretty easy given naive routing
-                                       // algorithms, but this fixes the most-obvious case.
-                                       let mut next_bytes = [0; 32];
-                                       chacha_stream.read_exact(&mut next_bytes).unwrap();
-                                       assert_ne!(next_bytes[..], [0; 32][..]);
-                                       chacha_stream.read_exact(&mut next_bytes).unwrap();
-                                       assert_ne!(next_bytes[..], [0; 32][..]);
-                               }
-
-                               // OUR PAYMENT!
-                               // final_expiry_too_soon
-                               // We have to have some headroom to broadcast on chain if we have the preimage, so make sure we have at least
-                               // HTLC_FAIL_BACK_BUFFER blocks to go.
-                               // Also, ensure that, in the case of an unknown payment hash, our payment logic has enough time to fail the HTLC backward
-                               // before our onchain logic triggers a channel closure (see HTLC_FAIL_BACK_BUFFER rational).
-                               if (msg.cltv_expiry as u64) <= self.best_block.read().unwrap().height() as u64 + HTLC_FAIL_BACK_BUFFER as u64 + 1 {
-                                       return_err!("The final CLTV expiry is too soon to handle", 17, &[0;0]);
-                               }
-                               // final_incorrect_htlc_amount
-                               if next_hop_data.amt_to_forward > msg.amount_msat {
-                                       return_err!("Upstream node sent less than we were supposed to receive in payment", 19, &byte_utils::be64_to_array(msg.amount_msat));
-                               }
-                               // final_incorrect_cltv_expiry
-                               if next_hop_data.outgoing_cltv_value != msg.cltv_expiry {
-                                       return_err!("Upstream node set CLTV to the wrong value", 18, &byte_utils::be32_to_array(msg.cltv_expiry));
-                               }
-
-                               let payment_data = match next_hop_data.format {
-                                       msgs::OnionHopDataFormat::Legacy { .. } => None,
-                                       msgs::OnionHopDataFormat::NonFinalNode { .. } => return_err!("Got non final data with an HMAC of 0", 0x4000 | 22, &[0;0]),
-                                       msgs::OnionHopDataFormat::FinalNode { payment_data } => payment_data,
-                               };
+                       #[cfg(test)]
+                       {
+                               // In tests, make sure that the initial onion pcket data is, at least, non-0.
+                               // We could do some fancy randomness test here, but, ehh, whatever.
+                               // This checks for the issue where you can calculate the path length given the
+                               // onion data as all the path entries that the originator sent will be here
+                               // as-is (and were originally 0s).
+                               // Of course reverse path calculation is still pretty easy given naive routing
+                               // algorithms, but this fixes the most-obvious case.
+                               let mut next_bytes = [0; 32];
+                               chacha_stream.read_exact(&mut next_bytes).unwrap();
+                               assert_ne!(next_bytes[..], [0; 32][..]);
+                               chacha_stream.read_exact(&mut next_bytes).unwrap();
+                               assert_ne!(next_bytes[..], [0; 32][..]);
+                       }
 
-                               if payment_data.is_none() {
-                                       return_err!("We require payment_secrets", 0x4000|0x2000|3, &[0;0]);
-                               }
+                       // OUR PAYMENT!
+                       // final_expiry_too_soon
+                       // We have to have some headroom to broadcast on chain if we have the preimage, so make sure
+                       // we have at least HTLC_FAIL_BACK_BUFFER blocks to go.
+                       // Also, ensure that, in the case of an unknown preimage for the received payment hash, our
+                       // payment logic has enough time to fail the HTLC backward before our onchain logic triggers a
+                       // channel closure (see HTLC_FAIL_BACK_BUFFER rationale).
+                       if (msg.cltv_expiry as u64) <= self.best_block.read().unwrap().height() as u64 + HTLC_FAIL_BACK_BUFFER as u64 + 1 {
+                               return_err!("The final CLTV expiry is too soon to handle", 17, &[0;0]);
+                       }
+                       // final_incorrect_htlc_amount
+                       if next_hop_data.amt_to_forward > msg.amount_msat {
+                               return_err!("Upstream node sent less than we were supposed to receive in payment", 19, &byte_utils::be64_to_array(msg.amount_msat));
+                       }
+                       // final_incorrect_cltv_expiry
+                       if next_hop_data.outgoing_cltv_value != msg.cltv_expiry {
+                               return_err!("Upstream node set CLTV to the wrong value", 18, &byte_utils::be32_to_array(msg.cltv_expiry));
+                       }
 
-                               // Note that we could obviously respond immediately with an update_fulfill_htlc
-                               // message, however that would leak that we are the recipient of this payment, so
-                               // instead we stay symmetric with the forwarding case, only responding (after a
-                               // delay) once they've send us a commitment_signed!
+                       let routing = match next_hop_data.format {
+                               msgs::OnionHopDataFormat::Legacy { .. } => return_err!("We require payment_secrets", 0x4000|0x2000|3, &[0;0]),
+                               msgs::OnionHopDataFormat::NonFinalNode { .. } => return_err!("Got non final data with an HMAC of 0", 0x4000 | 22, &[0;0]),
+                               msgs::OnionHopDataFormat::FinalNode { payment_data, keysend_preimage } => {
+                                       if payment_data.is_some() && keysend_preimage.is_some() {
+                                               return_err!("We don't support MPP keysend payments", 0x4000|22, &[0;0]);
+                                       } else if let Some(data) = payment_data {
+                                               PendingHTLCRouting::Receive {
+                                                       payment_data: data,
+                                                       incoming_cltv_expiry: msg.cltv_expiry,
+                                               }
+                                       } else if let Some(payment_preimage) = keysend_preimage {
+                                               // We need to check that the sender knows the keysend preimage before processing this
+                                               // payment further. Otherwise, an intermediary routing hop forwarding non-keysend-HTLC X
+                                               // could discover the final destination of X, by probing the adjacent nodes on the route
+                                               // with a keysend payment of identical payment hash to X and observing the processing
+                                               // time discrepancies due to a hash collision with X.
+                                               let hashed_preimage = PaymentHash(Sha256::hash(&payment_preimage.0).into_inner());
+                                               if hashed_preimage != msg.payment_hash {
+                                                       return_err!("Payment preimage didn't match payment hash", 0x4000|22, &[0;0]);
+                                               }
 
-                               PendingHTLCStatus::Forward(PendingHTLCInfo {
-                                       routing: PendingHTLCRouting::Receive {
-                                               payment_data: payment_data.unwrap(),
-                                               incoming_cltv_expiry: msg.cltv_expiry,
-                                       },
-                                       payment_hash: msg.payment_hash.clone(),
-                                       incoming_shared_secret: shared_secret,
-                                       amt_to_forward: next_hop_data.amt_to_forward,
-                                       outgoing_cltv_value: next_hop_data.outgoing_cltv_value,
-                               })
-                       } else {
-                               let mut new_packet_data = [0; 20*65];
-                               let read_pos = chacha_stream.read(&mut new_packet_data).unwrap();
-                               #[cfg(debug_assertions)]
-                               {
-                                       // Check two things:
-                                       // a) that the behavior of our stream here will return Ok(0) even if the TLV
-                                       //    read above emptied out our buffer and the unwrap() wont needlessly panic
-                                       // b) that we didn't somehow magically end up with extra data.
-                                       let mut t = [0; 1];
-                                       debug_assert!(chacha_stream.read(&mut t).unwrap() == 0);
-                               }
-                               // Once we've emptied the set of bytes our peer gave us, encrypt 0 bytes until we
-                               // fill the onion hop data we'll forward to our next-hop peer.
-                               chacha_stream.chacha.process_in_place(&mut new_packet_data[read_pos..]);
+                                               PendingHTLCRouting::ReceiveKeysend {
+                                                       payment_preimage,
+                                                       incoming_cltv_expiry: msg.cltv_expiry,
+                                               }
+                                       } else {
+                                               return_err!("We require payment_secrets", 0x4000|0x2000|3, &[0;0]);
+                                       }
+                               },
+                       };
 
-                               let mut new_pubkey = msg.onion_routing_packet.public_key.unwrap();
+                       // Note that we could obviously respond immediately with an update_fulfill_htlc
+                       // message, however that would leak that we are the recipient of this payment, so
+                       // instead we stay symmetric with the forwarding case, only responding (after a
+                       // delay) once they've send us a commitment_signed!
+
+                       PendingHTLCStatus::Forward(PendingHTLCInfo {
+                               routing,
+                               payment_hash: msg.payment_hash.clone(),
+                               incoming_shared_secret: shared_secret,
+                               amt_to_forward: next_hop_data.amt_to_forward,
+                               outgoing_cltv_value: next_hop_data.outgoing_cltv_value,
+                       })
+               } else {
+                       let mut new_packet_data = [0; 20*65];
+                       let read_pos = chacha_stream.read(&mut new_packet_data).unwrap();
+                       #[cfg(debug_assertions)]
+                       {
+                               // Check two things:
+                               // a) that the behavior of our stream here will return Ok(0) even if the TLV
+                               //    read above emptied out our buffer and the unwrap() wont needlessly panic
+                               // b) that we didn't somehow magically end up with extra data.
+                               let mut t = [0; 1];
+                               debug_assert!(chacha_stream.read(&mut t).unwrap() == 0);
+                       }
+                       // Once we've emptied the set of bytes our peer gave us, encrypt 0 bytes until we
+                       // fill the onion hop data we'll forward to our next-hop peer.
+                       chacha_stream.chacha.process_in_place(&mut new_packet_data[read_pos..]);
 
-                               let blinding_factor = {
-                                       let mut sha = Sha256::engine();
-                                       sha.input(&new_pubkey.serialize()[..]);
-                                       sha.input(&shared_secret);
-                                       Sha256::from_engine(sha).into_inner()
-                               };
+                       let mut new_pubkey = msg.onion_routing_packet.public_key.unwrap();
 
-                               let public_key = if let Err(e) = new_pubkey.mul_assign(&self.secp_ctx, &blinding_factor[..]) {
-                                       Err(e)
-                               } else { Ok(new_pubkey) };
+                       let blinding_factor = {
+                               let mut sha = Sha256::engine();
+                               sha.input(&new_pubkey.serialize()[..]);
+                               sha.input(&shared_secret);
+                               Sha256::from_engine(sha).into_inner()
+                       };
 
-                               let outgoing_packet = msgs::OnionPacket {
-                                       version: 0,
-                                       public_key,
-                                       hop_data: new_packet_data,
-                                       hmac: next_hop_hmac.clone(),
-                               };
+                       let public_key = if let Err(e) = new_pubkey.mul_assign(&self.secp_ctx, &blinding_factor[..]) {
+                               Err(e)
+                       } else { Ok(new_pubkey) };
 
-                               let short_channel_id = match next_hop_data.format {
-                                       msgs::OnionHopDataFormat::Legacy { short_channel_id } => short_channel_id,
-                                       msgs::OnionHopDataFormat::NonFinalNode { short_channel_id } => short_channel_id,
-                                       msgs::OnionHopDataFormat::FinalNode { .. } => {
-                                               return_err!("Final Node OnionHopData provided for us as an intermediary node", 0x4000 | 22, &[0;0]);
-                                       },
-                               };
+                       let outgoing_packet = msgs::OnionPacket {
+                               version: 0,
+                               public_key,
+                               hop_data: new_packet_data,
+                               hmac: next_hop_hmac.clone(),
+                       };
 
-                               PendingHTLCStatus::Forward(PendingHTLCInfo {
-                                       routing: PendingHTLCRouting::Forward {
-                                               onion_packet: outgoing_packet,
-                                               short_channel_id,
-                                       },
-                                       payment_hash: msg.payment_hash.clone(),
-                                       incoming_shared_secret: shared_secret,
-                                       amt_to_forward: next_hop_data.amt_to_forward,
-                                       outgoing_cltv_value: next_hop_data.outgoing_cltv_value,
-                               })
+                       let short_channel_id = match next_hop_data.format {
+                               msgs::OnionHopDataFormat::Legacy { short_channel_id } => short_channel_id,
+                               msgs::OnionHopDataFormat::NonFinalNode { short_channel_id } => short_channel_id,
+                               msgs::OnionHopDataFormat::FinalNode { .. } => {
+                                       return_err!("Final Node OnionHopData provided for us as an intermediary node", 0x4000 | 22, &[0;0]);
+                               },
                        };
 
+                       PendingHTLCStatus::Forward(PendingHTLCInfo {
+                               routing: PendingHTLCRouting::Forward {
+                                       onion_packet: outgoing_packet,
+                                       short_channel_id,
+                               },
+                               payment_hash: msg.payment_hash.clone(),
+                               incoming_shared_secret: shared_secret,
+                               amt_to_forward: next_hop_data.amt_to_forward,
+                               outgoing_cltv_value: next_hop_data.outgoing_cltv_value,
+                       })
+               };
+
                channel_state = Some(self.channel_state.lock().unwrap());
                if let &PendingHTLCStatus::Forward(PendingHTLCInfo { ref routing, ref amt_to_forward, ref outgoing_cltv_value, .. }) = &pending_forward_info {
                        // If short_channel_id is 0 here, we'll reject the HTLC as there cannot be a channel
@@ -1689,7 +1719,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
        }
 
        // Only public for testing, this should otherwise never be called direcly
-       pub(crate) fn send_payment_along_path(&self, path: &Vec<RouteHop>, payment_hash: &PaymentHash, payment_secret: &Option<PaymentSecret>, total_value: u64, cur_height: u32) -> Result<(), APIError> {
+       pub(crate) fn send_payment_along_path(&self, path: &Vec<RouteHop>, payment_hash: &PaymentHash, payment_secret: &Option<PaymentSecret>, total_value: u64, cur_height: u32, keysend_preimage: &Option<PaymentPreimage>) -> Result<(), APIError> {
                log_trace!(self.logger, "Attempting to send payment for path with next hop {}", path.first().unwrap().short_channel_id);
                let prng_seed = self.keys_manager.get_secure_random_bytes();
                let session_priv_bytes = self.keys_manager.get_secure_random_bytes();
@@ -1697,7 +1727,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
 
                let onion_keys = onion_utils::construct_onion_keys(&self.secp_ctx, &path, &session_priv)
                        .map_err(|_| APIError::RouteError{err: "Pubkey along hop was maliciously selected"})?;
-               let (onion_payloads, htlc_msat, htlc_cltv) = onion_utils::build_onion_payloads(path, total_value, payment_secret, cur_height)?;
+               let (onion_payloads, htlc_msat, htlc_cltv) = onion_utils::build_onion_payloads(path, total_value, payment_secret, cur_height, keysend_preimage)?;
                if onion_utils::route_size_insane(&onion_payloads) {
                        return Err(APIError::RouteError{err: "Route size too large considering onion data"});
                }
@@ -1806,6 +1836,10 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
        /// bit set (either as required or as available). If multiple paths are present in the Route,
        /// we assume the invoice had the basic_mpp feature set.
        pub fn send_payment(&self, route: &Route, payment_hash: PaymentHash, payment_secret: &Option<PaymentSecret>) -> Result<(), PaymentSendFailure> {
+               self.send_payment_internal(route, payment_hash, payment_secret, None)
+       }
+
+       fn send_payment_internal(&self, route: &Route, payment_hash: PaymentHash, payment_secret: &Option<PaymentSecret>, keysend_preimage: Option<PaymentPreimage>) -> Result<(), PaymentSendFailure> {
                if route.paths.len() < 1 {
                        return Err(PaymentSendFailure::ParameterError(APIError::RouteError{err: "There must be at least one path to send over"}));
                }
@@ -1839,7 +1873,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                let cur_height = self.best_block.read().unwrap().height() + 1;
                let mut results = Vec::new();
                for path in route.paths.iter() {
-                       results.push(self.send_payment_along_path(&path, &payment_hash, payment_secret, total_value, cur_height));
+                       results.push(self.send_payment_along_path(&path, &payment_hash, payment_secret, total_value, cur_height, &keysend_preimage));
                }
                let mut has_ok = false;
                let mut has_err = false;
@@ -1863,6 +1897,28 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                }
        }
 
+       /// Send a spontaneous payment, which is a payment that does not require the recipient to have
+       /// generated an invoice. Optionally, you may specify the preimage. If you do choose to specify
+       /// the preimage, it must be a cryptographically secure random value that no intermediate node
+       /// would be able to guess -- otherwise, an intermediate node may claim the payment and it will
+       /// never reach the recipient.
+       ///
+       /// Similar to regular payments, you MUST NOT reuse a `payment_preimage` value. See
+       /// [`send_payment`] for more information about the risks of duplicate preimage usage.
+       ///
+       /// [`send_payment`]: Self::send_payment
+       pub fn send_spontaneous_payment(&self, route: &Route, payment_preimage: Option<PaymentPreimage>) -> Result<PaymentHash, PaymentSendFailure> {
+               let preimage = match payment_preimage {
+                       Some(p) => p,
+                       None => PaymentPreimage(self.keys_manager.get_secure_random_bytes()),
+               };
+               let payment_hash = PaymentHash(Sha256::hash(&preimage.0).into_inner());
+               match self.send_payment_internal(route, payment_hash, &None, Some(preimage)) {
+                       Ok(()) => Ok(payment_hash),
+                       Err(e) => Err(e)
+               }
+       }
+
        /// Handles the generation of a funding transaction, optionally (for tests) with a function
        /// which checks the correctness of the funding transaction given the associated channel.
        fn funding_transaction_generated_intern<FundingOutput: Fn(&Channel<Signer>, &Transaction) -> Result<OutPoint, APIError>>
@@ -2248,9 +2304,17 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                        for forward_info in pending_forwards.drain(..) {
                                                match forward_info {
                                                        HTLCForwardInfo::AddHTLC { prev_short_channel_id, prev_htlc_id, forward_info: PendingHTLCInfo {
-                                                                       routing: PendingHTLCRouting::Receive { payment_data, incoming_cltv_expiry },
-                                                                       incoming_shared_secret, payment_hash, amt_to_forward, .. },
+                                                                       routing, incoming_shared_secret, payment_hash, amt_to_forward, .. },
                                                                        prev_funding_outpoint } => {
+                                                               let (cltv_expiry, onion_payload) = match routing {
+                                                                       PendingHTLCRouting::Receive { payment_data, incoming_cltv_expiry } =>
+                                                                               (incoming_cltv_expiry, OnionPayload::Invoice(payment_data)),
+                                                                       PendingHTLCRouting::ReceiveKeysend { payment_preimage, incoming_cltv_expiry } =>
+                                                                               (incoming_cltv_expiry, OnionPayload::Spontaneous(payment_preimage)),
+                                                                       _ => {
+                                                                               panic!("short_channel_id == 0 should imply any pending_forward entries are of type Receive");
+                                                                       }
+                                                               };
                                                                let claimable_htlc = ClaimableHTLC {
                                                                        prev_hop: HTLCPreviousHopData {
                                                                                short_channel_id: prev_short_channel_id,
@@ -2259,8 +2323,8 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                                incoming_packet_shared_secret: incoming_shared_secret,
                                                                        },
                                                                        value: amt_to_forward,
-                                                                       payment_data: payment_data.clone(),
-                                                                       cltv_expiry: incoming_cltv_expiry,
+                                                                       cltv_expiry,
+                                                                       onion_payload,
                                                                };
 
                                                                macro_rules! fail_htlc {
@@ -2289,10 +2353,38 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                let mut payment_secrets = self.pending_inbound_payments.lock().unwrap();
                                                                match payment_secrets.entry(payment_hash) {
                                                                        hash_map::Entry::Vacant(_) => {
-                                                                               log_trace!(self.logger, "Failing new HTLC with payment_hash {} as we didn't have a corresponding inbound payment.", log_bytes!(payment_hash.0));
-                                                                               fail_htlc!(claimable_htlc);
+                                                                               match claimable_htlc.onion_payload {
+                                                                                       OnionPayload::Invoice(_) => {
+                                                                                               log_trace!(self.logger, "Failing new HTLC with payment_hash {} as we didn't have a corresponding inbound payment.", log_bytes!(payment_hash.0));
+                                                                                               fail_htlc!(claimable_htlc);
+                                                                                       },
+                                                                                       OnionPayload::Spontaneous(preimage) => {
+                                                                                               match channel_state.claimable_htlcs.entry(payment_hash) {
+                                                                                                       hash_map::Entry::Vacant(e) => {
+                                                                                                               e.insert(vec![claimable_htlc]);
+                                                                                                               new_events.push(events::Event::PaymentReceived {
+                                                                                                                       payment_hash,
+                                                                                                                       amt: amt_to_forward,
+                                                                                                                       purpose: events::PaymentPurpose::SpontaneousPayment(preimage),
+                                                                                                               });
+                                                                                                       },
+                                                                                                       hash_map::Entry::Occupied(_) => {
+                                                                                                               log_trace!(self.logger, "Failing new keysend HTLC with payment_hash {} for a duplicative payment hash", log_bytes!(payment_hash.0));
+                                                                                                               fail_htlc!(claimable_htlc);
+                                                                                                       }
+                                                                                               }
+                                                                                       }
+                                                                               }
                                                                        },
                                                                        hash_map::Entry::Occupied(inbound_payment) => {
+                                                                               let payment_data =
+                                                                                       if let OnionPayload::Invoice(ref data) = claimable_htlc.onion_payload {
+                                                                                               data.clone()
+                                                                                       } else {
+                                                                                               log_trace!(self.logger, "Failing new keysend HTLC with payment_hash {} because we already have an inbound payment with the same payment hash", log_bytes!(payment_hash.0));
+                                                                                               fail_htlc!(claimable_htlc);
+                                                                                               continue
+                                                                                       };
                                                                                if inbound_payment.get().payment_secret != payment_data.payment_secret {
                                                                                        log_trace!(self.logger, "Failing new HTLC with payment_hash {} as it didn't match our expected payment secret.", log_bytes!(payment_hash.0));
                                                                                        fail_htlc!(claimable_htlc);
@@ -2304,15 +2396,27 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                                        let mut total_value = 0;
                                                                                        let htlcs = channel_state.claimable_htlcs.entry(payment_hash)
                                                                                                .or_insert(Vec::new());
+                                                                                       if htlcs.len() == 1 {
+                                                                                               if let OnionPayload::Spontaneous(_) = htlcs[0].onion_payload {
+                                                                                                       log_trace!(self.logger, "Failing new HTLC with payment_hash {} as we already had an existing keysend HTLC with the same payment hash", log_bytes!(payment_hash.0));
+                                                                                                       fail_htlc!(claimable_htlc);
+                                                                                                       continue
+                                                                                               }
+                                                                                       }
                                                                                        htlcs.push(claimable_htlc);
                                                                                        for htlc in htlcs.iter() {
                                                                                                total_value += htlc.value;
-                                                                                               if htlc.payment_data.total_msat != payment_data.total_msat {
-                                                                                                       log_trace!(self.logger, "Failing HTLCs with payment_hash {} as the HTLCs had inconsistent total values (eg {} and {})",
-                                                                                                               log_bytes!(payment_hash.0), payment_data.total_msat, htlc.payment_data.total_msat);
-                                                                                                       total_value = msgs::MAX_VALUE_MSAT;
+                                                                                               match &htlc.onion_payload {
+                                                                                                       OnionPayload::Invoice(htlc_payment_data) => {
+                                                                                                               if htlc_payment_data.total_msat != payment_data.total_msat {
+                                                                                                                       log_trace!(self.logger, "Failing HTLCs with payment_hash {} as the HTLCs had inconsistent total values (eg {} and {})",
+                                                                                                                                                                log_bytes!(payment_hash.0), payment_data.total_msat, htlc_payment_data.total_msat);
+                                                                                                                       total_value = msgs::MAX_VALUE_MSAT;
+                                                                                                               }
+                                                                                                               if total_value >= msgs::MAX_VALUE_MSAT { break; }
+                                                                                                       },
+                                                                                                       _ => unreachable!(),
                                                                                                }
-                                                                                               if total_value >= msgs::MAX_VALUE_MSAT { break; }
                                                                                        }
                                                                                        if total_value >= msgs::MAX_VALUE_MSAT || total_value > payment_data.total_msat {
                                                                                                log_trace!(self.logger, "Failing HTLCs with payment_hash {} as the total value {} ran over expected value {} (or HTLCs were inconsistent)",
@@ -2323,10 +2427,12 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                                        } else if total_value == payment_data.total_msat {
                                                                                                new_events.push(events::Event::PaymentReceived {
                                                                                                        payment_hash,
-                                                                                                       payment_preimage: inbound_payment.get().payment_preimage,
-                                                                                                       payment_secret: payment_data.payment_secret,
+                                                                                                       purpose: events::PaymentPurpose::InvoicePayment {
+                                                                                                               payment_preimage: inbound_payment.get().payment_preimage,
+                                                                                                               payment_secret: payment_data.payment_secret,
+                                                                                                               user_payment_id: inbound_payment.get().user_payment_id,
+                                                                                                       },
                                                                                                        amt: total_value,
-                                                                                                       user_payment_id: inbound_payment.get().user_payment_id,
                                                                                                });
                                                                                                // Only ever generate at most one PaymentReceived
                                                                                                // per registered payment_hash, even if it isn't
@@ -2341,9 +2447,6 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                                                        },
                                                                };
                                                        },
-                                                       HTLCForwardInfo::AddHTLC { .. } => {
-                                                               panic!("short_channel_id == 0 should imply any pending_forward entries are of type Receive");
-                                                       },
                                                        HTLCForwardInfo::FailHTLC { .. } => {
                                                                panic!("Got pending fail of our own HTLC");
                                                        }
@@ -3318,6 +3421,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
                                        match channel_state.forward_htlcs.entry(match forward_info.routing {
                                                        PendingHTLCRouting::Forward { short_channel_id, .. } => short_channel_id,
                                                        PendingHTLCRouting::Receive { .. } => 0,
+                                                       PendingHTLCRouting::ReceiveKeysend { .. } => 0,
                                        }) {
                                                hash_map::Entry::Occupied(mut entry) => {
                                                        entry.get_mut().push(HTLCForwardInfo::AddHTLC { prev_short_channel_id, prev_funding_outpoint,
@@ -3773,7 +3877,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
        /// The [`PaymentHash`] (and corresponding [`PaymentPreimage`]) must be globally unique. This
        /// method may return an Err if another payment with the same payment_hash is still pending.
        ///
-       /// `user_payment_id` will be provided back in [`PaymentReceived::user_payment_id`] events to
+       /// `user_payment_id` will be provided back in [`PaymentPurpose::InvoicePayment::user_payment_id`] events to
        /// allow tracking of which events correspond with which calls to this and
        /// [`create_inbound_payment`]. `user_payment_id` has no meaning inside of LDK, it is simply
        /// copied to events and otherwise ignored. It may be used to correlate PaymentReceived events
@@ -3807,7 +3911,7 @@ impl<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref> ChannelMana
        ///
        /// [`create_inbound_payment`]: Self::create_inbound_payment
        /// [`PaymentReceived`]: events::Event::PaymentReceived
-       /// [`PaymentReceived::user_payment_id`]: events::Event::PaymentReceived::user_payment_id
+       /// [`PaymentPurpose::InvoicePayment::user_payment_id`]: events::PaymentPurpose::InvoicePayment::user_payment_id
        pub fn create_inbound_payment_for_hash(&self, payment_hash: PaymentHash, min_value_msat: Option<u64>, invoice_expiry_delta_secs: u32, user_payment_id: u64) -> Result<PaymentSecret, APIError> {
                self.set_payment_hash_secret_map(payment_hash, None, min_value_msat, invoice_expiry_delta_secs, user_payment_id)
        }
@@ -4471,7 +4575,11 @@ impl_writeable_tlv_based_enum!(PendingHTLCRouting,
        (1, Receive) => {
                (0, payment_data, required),
                (2, incoming_cltv_expiry, required),
-       }
+       },
+       (2, ReceiveKeysend) => {
+               (0, payment_preimage, required),
+               (2, incoming_cltv_expiry, required),
+       },
 ;);
 
 impl_writeable_tlv_based!(PendingHTLCInfo, {
@@ -4498,12 +4606,63 @@ impl_writeable_tlv_based!(HTLCPreviousHopData, {
        (6, incoming_packet_shared_secret, required)
 });
 
-impl_writeable_tlv_based!(ClaimableHTLC, {
-       (0, prev_hop, required),
-       (2, value, required),
-       (4, payment_data, required),
-       (6, cltv_expiry, required),
-});
+impl Writeable for ClaimableHTLC {
+       fn write<W: Writer>(&self, writer: &mut W) -> Result<(), ::std::io::Error> {
+               let payment_data = match &self.onion_payload {
+                       OnionPayload::Invoice(data) => Some(data.clone()),
+                       _ => None,
+               };
+               let keysend_preimage = match self.onion_payload {
+                       OnionPayload::Invoice(_) => None,
+                       OnionPayload::Spontaneous(preimage) => Some(preimage.clone()),
+               };
+               write_tlv_fields!
+               (writer,
+                {
+                  (0, self.prev_hop, required), (2, self.value, required),
+                  (4, payment_data, option), (6, self.cltv_expiry, required),
+                        (8, keysend_preimage, option),
+                });
+               Ok(())
+       }
+}
+
+impl Readable for ClaimableHTLC {
+       fn read<R: Read>(reader: &mut R) -> Result<Self, DecodeError> {
+               let mut prev_hop = ::util::ser::OptionDeserWrapper(None);
+               let mut value = 0;
+               let mut payment_data: Option<msgs::FinalOnionHopData> = None;
+               let mut cltv_expiry = 0;
+               let mut keysend_preimage: Option<PaymentPreimage> = None;
+               read_tlv_fields!
+               (reader,
+                {
+                  (0, prev_hop, required), (2, value, required),
+                  (4, payment_data, option), (6, cltv_expiry, required),
+                        (8, keysend_preimage, option)
+                });
+               let onion_payload = match keysend_preimage {
+                       Some(p) => {
+                               if payment_data.is_some() {
+                                       return Err(DecodeError::InvalidValue)
+                               }
+                               OnionPayload::Spontaneous(p)
+                       },
+                       None => {
+                               if payment_data.is_none() {
+                                       return Err(DecodeError::InvalidValue)
+                               }
+                               OnionPayload::Invoice(payment_data.unwrap())
+                       },
+               };
+               Ok(Self {
+                       prev_hop: prev_hop.0.unwrap(),
+                       value,
+                       onion_payload,
+                       cltv_expiry,
+               })
+       }
+}
 
 impl_writeable_tlv_based_enum!(HTLCSource,
        (0, OutboundRoute) => {
@@ -4950,14 +5109,21 @@ impl<'a, Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref, L: Deref>
 
 #[cfg(test)]
 mod tests {
-       use ln::channelmanager::PersistenceNotifier;
-       use sync::Arc;
+       use bitcoin::hashes::Hash;
+       use bitcoin::hashes::sha256::Hash as Sha256;
        use core::sync::atomic::{AtomicBool, Ordering};
-       use std::thread;
        use core::time::Duration;
+       use ln::{PaymentPreimage, PaymentHash, PaymentSecret};
+       use ln::channelmanager::PersistenceNotifier;
+       use ln::features::{InitFeatures, InvoiceFeatures};
        use ln::functional_test_utils::*;
-       use ln::features::InitFeatures;
+       use ln::msgs;
        use ln::msgs::ChannelMessageHandler;
+       use routing::router::{get_keysend_route, get_route};
+       use util::events::{Event, MessageSendEvent, MessageSendEventsProvider};
+       use util::test_utils;
+       use std::sync::Arc;
+       use std::thread;
 
        #[cfg(feature = "std")]
        #[test]
@@ -5073,6 +5239,265 @@ mod tests {
                assert_ne!(nodes[0].node.list_channels()[0], node_a_chan_info);
                assert_ne!(nodes[1].node.list_channels()[0], node_b_chan_info);
        }
+
+       #[test]
+       fn test_keysend_dup_hash_partial_mpp() {
+               // Test that a keysend payment with a duplicate hash to an existing partial MPP payment fails as
+               // expected.
+               let chanmon_cfgs = create_chanmon_cfgs(2);
+               let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+               let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
+               let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+               create_announced_chan_between_nodes(&nodes, 0, 1, InitFeatures::known(), InitFeatures::known());
+               let logger = test_utils::TestLogger::new();
+
+               // First, send a partial MPP payment.
+               let net_graph_msg_handler = &nodes[0].net_graph_msg_handler;
+               let route = get_route(&nodes[0].node.get_our_node_id(), &net_graph_msg_handler.network_graph.read().unwrap(), &nodes[1].node.get_our_node_id(), Some(InvoiceFeatures::known()), None, &Vec::new(), 100_000, TEST_FINAL_CLTV, &logger).unwrap();
+               let (payment_preimage, our_payment_hash, payment_secret) = get_payment_preimage_hash!(&nodes[1]);
+               // Use the utility function send_payment_along_path to send the payment with MPP data which
+               // indicates there are more HTLCs coming.
+               let cur_height = CHAN_CONFIRM_DEPTH + 1; // route_payment calls send_payment, which adds 1 to the current height. So we do the same here to match.
+               nodes[0].node.send_payment_along_path(&route.paths[0], &our_payment_hash, &Some(payment_secret), 200_000, cur_height, &None).unwrap();
+               check_added_monitors!(nodes[0], 1);
+               let mut events = nodes[0].node.get_and_clear_pending_msg_events();
+               assert_eq!(events.len(), 1);
+               pass_along_path(&nodes[0], &[&nodes[1]], 200_000, our_payment_hash, Some(payment_secret), events.drain(..).next().unwrap(), false, None);
+
+               // Next, send a keysend payment with the same payment_hash and make sure it fails.
+               nodes[0].node.send_spontaneous_payment(&route, Some(payment_preimage)).unwrap();
+               check_added_monitors!(nodes[0], 1);
+               let mut events = nodes[0].node.get_and_clear_pending_msg_events();
+               assert_eq!(events.len(), 1);
+               let ev = events.drain(..).next().unwrap();
+               let payment_event = SendEvent::from_event(ev);
+               nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &payment_event.msgs[0]);
+               check_added_monitors!(nodes[1], 0);
+               commitment_signed_dance!(nodes[1], nodes[0], payment_event.commitment_msg, false);
+               expect_pending_htlcs_forwardable!(nodes[1]);
+               expect_pending_htlcs_forwardable!(nodes[1]);
+               check_added_monitors!(nodes[1], 1);
+               let updates = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
+               assert!(updates.update_add_htlcs.is_empty());
+               assert!(updates.update_fulfill_htlcs.is_empty());
+               assert_eq!(updates.update_fail_htlcs.len(), 1);
+               assert!(updates.update_fail_malformed_htlcs.is_empty());
+               assert!(updates.update_fee.is_none());
+               nodes[0].node.handle_update_fail_htlc(&nodes[1].node.get_our_node_id(), &updates.update_fail_htlcs[0]);
+               commitment_signed_dance!(nodes[0], nodes[1], updates.commitment_signed, true, true);
+               expect_payment_failed!(nodes[0], our_payment_hash, true);
+
+               // Send the second half of the original MPP payment.
+               nodes[0].node.send_payment_along_path(&route.paths[0], &our_payment_hash, &Some(payment_secret), 200_000, cur_height, &None).unwrap();
+               check_added_monitors!(nodes[0], 1);
+               let mut events = nodes[0].node.get_and_clear_pending_msg_events();
+               assert_eq!(events.len(), 1);
+               pass_along_path(&nodes[0], &[&nodes[1]], 200_000, our_payment_hash, Some(payment_secret), events.drain(..).next().unwrap(), true, None);
+
+               // Claim the full MPP payment. Note that we can't use a test utility like
+               // claim_funds_along_route because the ordering of the messages causes the second half of the
+               // payment to be put in the holding cell, which confuses the test utilities. So we exchange the
+               // lightning messages manually.
+               assert!(nodes[1].node.claim_funds(payment_preimage));
+               check_added_monitors!(nodes[1], 2);
+               let bs_first_updates = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
+               nodes[0].node.handle_update_fulfill_htlc(&nodes[1].node.get_our_node_id(), &bs_first_updates.update_fulfill_htlcs[0]);
+               nodes[0].node.handle_commitment_signed(&nodes[1].node.get_our_node_id(), &bs_first_updates.commitment_signed);
+               check_added_monitors!(nodes[0], 1);
+               let (as_first_raa, as_first_cs) = get_revoke_commit_msgs!(nodes[0], nodes[1].node.get_our_node_id());
+               nodes[1].node.handle_revoke_and_ack(&nodes[0].node.get_our_node_id(), &as_first_raa);
+               check_added_monitors!(nodes[1], 1);
+               let bs_second_updates = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
+               nodes[1].node.handle_commitment_signed(&nodes[0].node.get_our_node_id(), &as_first_cs);
+               check_added_monitors!(nodes[1], 1);
+               let bs_first_raa = get_event_msg!(nodes[1], MessageSendEvent::SendRevokeAndACK, nodes[0].node.get_our_node_id());
+               nodes[0].node.handle_update_fulfill_htlc(&nodes[1].node.get_our_node_id(), &bs_second_updates.update_fulfill_htlcs[0]);
+               nodes[0].node.handle_commitment_signed(&nodes[1].node.get_our_node_id(), &bs_second_updates.commitment_signed);
+               check_added_monitors!(nodes[0], 1);
+               let as_second_raa = get_event_msg!(nodes[0], MessageSendEvent::SendRevokeAndACK, nodes[1].node.get_our_node_id());
+               nodes[0].node.handle_revoke_and_ack(&nodes[1].node.get_our_node_id(), &bs_first_raa);
+               let as_second_updates = get_htlc_update_msgs!(nodes[0], nodes[1].node.get_our_node_id());
+               check_added_monitors!(nodes[0], 1);
+               nodes[1].node.handle_revoke_and_ack(&nodes[0].node.get_our_node_id(), &as_second_raa);
+               check_added_monitors!(nodes[1], 1);
+               nodes[1].node.handle_commitment_signed(&nodes[0].node.get_our_node_id(), &as_second_updates.commitment_signed);
+               check_added_monitors!(nodes[1], 1);
+               let bs_third_raa = get_event_msg!(nodes[1], MessageSendEvent::SendRevokeAndACK, nodes[0].node.get_our_node_id());
+               nodes[0].node.handle_revoke_and_ack(&nodes[1].node.get_our_node_id(), &bs_third_raa);
+               check_added_monitors!(nodes[0], 1);
+
+               // There's an existing bug that generates a PaymentSent event for each MPP path, so handle that here.
+               let events = nodes[0].node.get_and_clear_pending_events();
+               match events[0] {
+                       Event::PaymentSent { payment_preimage: ref preimage } => {
+                               assert_eq!(payment_preimage, *preimage);
+                       },
+                       _ => panic!("Unexpected event"),
+               }
+               match events[1] {
+                       Event::PaymentSent { payment_preimage: ref preimage } => {
+                               assert_eq!(payment_preimage, *preimage);
+                       },
+                       _ => panic!("Unexpected event"),
+               }
+       }
+
+       #[test]
+       fn test_keysend_dup_payment_hash() {
+               // (1): Test that a keysend payment with a duplicate payment hash to an existing pending
+               //      outbound regular payment fails as expected.
+               // (2): Test that a regular payment with a duplicate payment hash to an existing keysend payment
+               //      fails as expected.
+               let chanmon_cfgs = create_chanmon_cfgs(2);
+               let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+               let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
+               let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+               create_announced_chan_between_nodes(&nodes, 0, 1, InitFeatures::known(), InitFeatures::known());
+               let logger = test_utils::TestLogger::new();
+
+               // To start (1), send a regular payment but don't claim it.
+               let expected_route = [&nodes[1]];
+               let (payment_preimage, payment_hash, _) = route_payment(&nodes[0], &expected_route, 100_000);
+
+               // Next, attempt a keysend payment and make sure it fails.
+               let route = get_route(&nodes[0].node.get_our_node_id(), &nodes[0].net_graph_msg_handler.network_graph.read().unwrap(), &expected_route.last().unwrap().node.get_our_node_id(), Some(InvoiceFeatures::known()), None, &Vec::new(), 100_000, TEST_FINAL_CLTV, &logger).unwrap();
+               nodes[0].node.send_spontaneous_payment(&route, Some(payment_preimage)).unwrap();
+               check_added_monitors!(nodes[0], 1);
+               let mut events = nodes[0].node.get_and_clear_pending_msg_events();
+               assert_eq!(events.len(), 1);
+               let ev = events.drain(..).next().unwrap();
+               let payment_event = SendEvent::from_event(ev);
+               nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &payment_event.msgs[0]);
+               check_added_monitors!(nodes[1], 0);
+               commitment_signed_dance!(nodes[1], nodes[0], payment_event.commitment_msg, false);
+               expect_pending_htlcs_forwardable!(nodes[1]);
+               expect_pending_htlcs_forwardable!(nodes[1]);
+               check_added_monitors!(nodes[1], 1);
+               let updates = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
+               assert!(updates.update_add_htlcs.is_empty());
+               assert!(updates.update_fulfill_htlcs.is_empty());
+               assert_eq!(updates.update_fail_htlcs.len(), 1);
+               assert!(updates.update_fail_malformed_htlcs.is_empty());
+               assert!(updates.update_fee.is_none());
+               nodes[0].node.handle_update_fail_htlc(&nodes[1].node.get_our_node_id(), &updates.update_fail_htlcs[0]);
+               commitment_signed_dance!(nodes[0], nodes[1], updates.commitment_signed, true, true);
+               expect_payment_failed!(nodes[0], payment_hash, true);
+
+               // Finally, claim the original payment.
+               claim_payment(&nodes[0], &expected_route, payment_preimage);
+
+               // To start (2), send a keysend payment but don't claim it.
+               let payment_preimage = PaymentPreimage([42; 32]);
+               let route = get_route(&nodes[0].node.get_our_node_id(), &nodes[0].net_graph_msg_handler.network_graph.read().unwrap(), &expected_route.last().unwrap().node.get_our_node_id(), Some(InvoiceFeatures::known()), None, &Vec::new(), 100_000, TEST_FINAL_CLTV, &logger).unwrap();
+               let payment_hash = nodes[0].node.send_spontaneous_payment(&route, Some(payment_preimage)).unwrap();
+               check_added_monitors!(nodes[0], 1);
+               let mut events = nodes[0].node.get_and_clear_pending_msg_events();
+               assert_eq!(events.len(), 1);
+               let event = events.pop().unwrap();
+               let path = vec![&nodes[1]];
+               pass_along_path(&nodes[0], &path, 100_000, payment_hash, None, event, true, Some(payment_preimage));
+
+               // Next, attempt a regular payment and make sure it fails.
+               let payment_secret = PaymentSecret([43; 32]);
+               nodes[0].node.send_payment(&route, payment_hash, &Some(payment_secret)).unwrap();
+               check_added_monitors!(nodes[0], 1);
+               let mut events = nodes[0].node.get_and_clear_pending_msg_events();
+               assert_eq!(events.len(), 1);
+               let ev = events.drain(..).next().unwrap();
+               let payment_event = SendEvent::from_event(ev);
+               nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &payment_event.msgs[0]);
+               check_added_monitors!(nodes[1], 0);
+               commitment_signed_dance!(nodes[1], nodes[0], payment_event.commitment_msg, false);
+               expect_pending_htlcs_forwardable!(nodes[1]);
+               expect_pending_htlcs_forwardable!(nodes[1]);
+               check_added_monitors!(nodes[1], 1);
+               let updates = get_htlc_update_msgs!(nodes[1], nodes[0].node.get_our_node_id());
+               assert!(updates.update_add_htlcs.is_empty());
+               assert!(updates.update_fulfill_htlcs.is_empty());
+               assert_eq!(updates.update_fail_htlcs.len(), 1);
+               assert!(updates.update_fail_malformed_htlcs.is_empty());
+               assert!(updates.update_fee.is_none());
+               nodes[0].node.handle_update_fail_htlc(&nodes[1].node.get_our_node_id(), &updates.update_fail_htlcs[0]);
+               commitment_signed_dance!(nodes[0], nodes[1], updates.commitment_signed, true, true);
+               expect_payment_failed!(nodes[0], payment_hash, true);
+
+               // Finally, succeed the keysend payment.
+               claim_payment(&nodes[0], &expected_route, payment_preimage);
+       }
+
+       #[test]
+       fn test_keysend_hash_mismatch() {
+               // Test that if we receive a keysend `update_add_htlc` msg, we fail as expected if the keysend
+               // preimage doesn't match the msg's payment hash.
+               let chanmon_cfgs = create_chanmon_cfgs(2);
+               let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+               let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
+               let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+
+               let payer_pubkey = nodes[0].node.get_our_node_id();
+               let payee_pubkey = nodes[1].node.get_our_node_id();
+               nodes[0].node.peer_connected(&payee_pubkey, &msgs::Init { features: InitFeatures::known() });
+               nodes[1].node.peer_connected(&payer_pubkey, &msgs::Init { features: InitFeatures::known() });
+
+               let _chan = create_chan_between_nodes(&nodes[0], &nodes[1], InitFeatures::known(), InitFeatures::known());
+               let network_graph = nodes[0].net_graph_msg_handler.network_graph.read().unwrap();
+               let first_hops = nodes[0].node.list_usable_channels();
+               let route = get_keysend_route(&payer_pubkey, &network_graph, &payee_pubkey,
+                                  Some(&first_hops.iter().collect::<Vec<_>>()), &vec![], 10000, 40,
+                                  nodes[0].logger).unwrap();
+
+               let test_preimage = PaymentPreimage([42; 32]);
+               let mismatch_payment_hash = PaymentHash([43; 32]);
+               let _ = nodes[0].node.send_payment_internal(&route, mismatch_payment_hash, &None, Some(test_preimage)).unwrap();
+               check_added_monitors!(nodes[0], 1);
+
+               let updates = get_htlc_update_msgs!(nodes[0], nodes[1].node.get_our_node_id());
+               assert_eq!(updates.update_add_htlcs.len(), 1);
+               assert!(updates.update_fulfill_htlcs.is_empty());
+               assert!(updates.update_fail_htlcs.is_empty());
+               assert!(updates.update_fail_malformed_htlcs.is_empty());
+               assert!(updates.update_fee.is_none());
+               nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &updates.update_add_htlcs[0]);
+
+               nodes[1].logger.assert_log_contains("lightning::ln::channelmanager".to_string(), "Payment preimage didn't match payment hash".to_string(), 1);
+       }
+
+       #[test]
+       fn test_keysend_msg_with_secret_err() {
+               // Test that we error as expected if we receive a keysend payment that includes a payment secret.
+               let chanmon_cfgs = create_chanmon_cfgs(2);
+               let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+               let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
+               let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+
+               let payer_pubkey = nodes[0].node.get_our_node_id();
+               let payee_pubkey = nodes[1].node.get_our_node_id();
+               nodes[0].node.peer_connected(&payee_pubkey, &msgs::Init { features: InitFeatures::known() });
+               nodes[1].node.peer_connected(&payer_pubkey, &msgs::Init { features: InitFeatures::known() });
+
+               let _chan = create_chan_between_nodes(&nodes[0], &nodes[1], InitFeatures::known(), InitFeatures::known());
+               let network_graph = nodes[0].net_graph_msg_handler.network_graph.read().unwrap();
+               let first_hops = nodes[0].node.list_usable_channels();
+               let route = get_keysend_route(&payer_pubkey, &network_graph, &payee_pubkey,
+                                  Some(&first_hops.iter().collect::<Vec<_>>()), &vec![], 10000, 40,
+                                  nodes[0].logger).unwrap();
+
+               let test_preimage = PaymentPreimage([42; 32]);
+               let test_secret = PaymentSecret([43; 32]);
+               let payment_hash = PaymentHash(Sha256::hash(&test_preimage.0).into_inner());
+               let _ = nodes[0].node.send_payment_internal(&route, payment_hash, &Some(test_secret), Some(test_preimage)).unwrap();
+               check_added_monitors!(nodes[0], 1);
+
+               let updates = get_htlc_update_msgs!(nodes[0], nodes[1].node.get_our_node_id());
+               assert_eq!(updates.update_add_htlcs.len(), 1);
+               assert!(updates.update_fulfill_htlcs.is_empty());
+               assert!(updates.update_fail_htlcs.is_empty());
+               assert!(updates.update_fail_malformed_htlcs.is_empty());
+               assert!(updates.update_fee.is_none());
+               nodes[1].node.handle_update_add_htlc(&nodes[0].node.get_our_node_id(), &updates.update_add_htlcs[0]);
+
+               nodes[1].logger.assert_log_contains("lightning::ln::channelmanager".to_string(), "We don't support MPP keysend payments".to_string(), 1);
+       }
 }
 
 #[cfg(all(any(test, feature = "_test_utils"), feature = "unstable"))]
@@ -5089,7 +5514,7 @@ pub mod bench {
        use routing::router::get_route;
        use util::test_utils;
        use util::config::UserConfig;
-       use util::events::{Event, MessageSendEvent, MessageSendEventsProvider};
+       use util::events::{Event, MessageSendEvent, MessageSendEventsProvider, PaymentPurpose};
 
        use bitcoin::hashes::Hash;
        use bitcoin::hashes::sha256::Hash as Sha256;