Add `total_value_received` to `ClaimableHTLC` for claim validation

This is pre-work for allowing nodes to overshoot onion values and
changing validation for MPP completion. This adds a field to
`ClaimableHTLC` that is separate from the onion values, which
represents the actual received amount reported in `PaymentClaimable`
which is what we want to validate against when a user goes to claim.

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index 6bd9148e98734d5ce833f5e6d9e7db3d14256280..199beeae525a6a01bcb21894120ac495030704b2 100644 (file)
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -194,7 +194,10 @@ struct ClaimableHTLC {
        value: u64,
        onion_payload: OnionPayload,
        timer_ticks: u8,
-       /// The sum total of all MPP parts
+       /// The total value received for a payment (sum of all MPP parts if the payment is a MPP).
+       /// Gets set to the amount reported when pushing [`Event::PaymentClaimable`].
+       total_value_received: Option<u64>,
+       /// The sender intended sum total of all MPP parts specified in the onion
        total_msat: u64,
 }
 
@@ -3272,7 +3275,7 @@ where
                                                                                panic!("short_channel_id == 0 should imply any pending_forward entries are of type Receive");
                                                                        }
                                                                };
-                                                               let claimable_htlc = ClaimableHTLC {
+                                                               let mut claimable_htlc = ClaimableHTLC {
                                                                        prev_hop: HTLCPreviousHopData {
                                                                                short_channel_id: prev_short_channel_id,
                                                                                outpoint: prev_funding_outpoint,
@@ -3282,6 +3285,7 @@ where
                                                                        },
                                                                        value: outgoing_amt_msat,
                                                                        timer_ticks: 0,
+                                                                       total_value_received: None,
                                                                        total_msat: if let Some(data) = &payment_data { data.total_msat } else { outgoing_amt_msat },
                                                                        cltv_expiry,
                                                                        onion_payload,
@@ -3326,7 +3330,7 @@ where
                                                                                        fail_htlc!(claimable_htlc, payment_hash);
                                                                                        continue
                                                                                }
-                                                                               let (_, htlcs) = claimable_payments.claimable_htlcs.entry(payment_hash)
+                                                                               let (_, ref mut htlcs) = claimable_payments.claimable_htlcs.entry(payment_hash)
                                                                                        .or_insert_with(|| (purpose(), Vec::new()));
                                                                                if htlcs.len() == 1 {
                                                                                        if let OnionPayload::Spontaneous(_) = htlcs[0].onion_payload {
@@ -3357,11 +3361,13 @@ where
                                                                                } else if total_value == $payment_data.total_msat {
                                                                                        let prev_channel_id = prev_funding_outpoint.to_channel_id();
                                                                                        htlcs.push(claimable_htlc);
+                                                                                       let amount_msat = htlcs.iter().map(|htlc| htlc.value).sum();
+                                                                                       htlcs.iter_mut().for_each(|htlc| htlc.total_value_received = Some(amount_msat));
                                                                                        new_events.push(events::Event::PaymentClaimable {
                                                                                                receiver_node_id: Some(receiver_node_id),
                                                                                                payment_hash,
                                                                                                purpose: purpose(),
-                                                                                               amount_msat: total_value,
+                                                                                               amount_msat,
                                                                                                via_channel_id: Some(prev_channel_id),
                                                                                                via_user_channel_id: Some(prev_user_channel_id),
                                                                                        });
@@ -3415,6 +3421,8 @@ where
                                                                                                }
                                                                                                match claimable_payments.claimable_htlcs.entry(payment_hash) {
                                                                                                        hash_map::Entry::Vacant(e) => {
+                                                                                                               let amount_msat = claimable_htlc.value;
+                                                                                                               claimable_htlc.total_value_received = Some(amount_msat);
                                                                                                                let purpose = events::PaymentPurpose::SpontaneousPayment(preimage);
                                                                                                                e.insert((purpose.clone(), vec![claimable_htlc]));
                                                                                                                let prev_channel_id = prev_funding_outpoint.to_channel_id();
@@ -3960,6 +3968,7 @@ where
                // provide the preimage, so worrying too much about the optimal handling isn't worth
                // it.
                let mut claimable_amt_msat = 0;
+               let mut prev_total_msat = None;
                let mut expected_amt_msat = None;
                let mut valid_mpp = true;
                let mut errs = Vec::new();
@@ -3987,14 +3996,22 @@ where
                                break;
                        }
 
-                       if expected_amt_msat.is_some() && expected_amt_msat != Some(htlc.total_msat) {
-                               log_error!(self.logger, "Somehow ended up with an MPP payment with different total amounts - this should not be reachable!");
+                       if prev_total_msat.is_some() && prev_total_msat != Some(htlc.total_msat) {
+                               log_error!(self.logger, "Somehow ended up with an MPP payment with different expected total amounts - this should not be reachable!");
                                debug_assert!(false);
                                valid_mpp = false;
                                break;
                        }
+                       prev_total_msat = Some(htlc.total_msat);
+
+                       if expected_amt_msat.is_some() && expected_amt_msat != htlc.total_value_received {
+                               log_error!(self.logger, "Somehow ended up with an MPP payment with different received total amounts - this should not be reachable!");
+                               debug_assert!(false);
+                               valid_mpp = false;
+                               break;
+                       }
+                       expected_amt_msat = htlc.total_value_received;
 
-                       expected_amt_msat = Some(htlc.total_msat);
                        if let OnionPayload::Spontaneous(_) = &htlc.onion_payload {
                                // We don't currently support MPP for spontaneous payments, so just check
                                // that there's one payment here and move on.
@@ -6795,6 +6812,7 @@ impl Writeable for ClaimableHTLC {
                        (1, self.total_msat, required),
                        (2, self.value, required),
                        (4, payment_data, option),
+                       (5, self.total_value_received, option),
                        (6, self.cltv_expiry, required),
                        (8, keysend_preimage, option),
                });
@@ -6808,6 +6826,7 @@ impl Readable for ClaimableHTLC {
                let mut value = 0;
                let mut payment_data: Option<msgs::FinalOnionHopData> = None;
                let mut cltv_expiry = 0;
+               let mut total_value_received = None;
                let mut total_msat = None;
                let mut keysend_preimage: Option<PaymentPreimage> = None;
                read_tlv_fields!(reader, {
@@ -6815,6 +6834,7 @@ impl Readable for ClaimableHTLC {
                        (1, total_msat, option),
                        (2, value, required),
                        (4, payment_data, option),
+                       (5, total_value_received, option),
                        (6, cltv_expiry, required),
                        (8, keysend_preimage, option)
                });
@@ -6842,6 +6862,7 @@ impl Readable for ClaimableHTLC {
                        prev_hop: prev_hop.0.unwrap(),
                        timer_ticks: 0,
                        value,
+                       total_value_received,
                        total_msat: total_msat.unwrap(),
                        onion_payload,
                        cltv_expiry,