f fail to deser if PaymentClaimable has skimmed fee present

Author: valentinewallace

lightning/src/events/mod.rs

@@ -848,7 +848,7 @@ impl Writeable for Event {
 				// We never write out FundingGenerationReady events as, upon disconnection, peers
 				// drop any channels which have not yet exchanged funding_signed.
 			},
-			&Event::PaymentClaimable { ref payment_hash, ref amount_msat, ref counterparty_skimmed_fee_msat,
+			&Event::PaymentClaimable { ref payment_hash, ref amount_msat, counterparty_skimmed_fee_msat,
 				ref purpose, ref receiver_node_id, ref via_channel_id, ref via_user_channel_id,
 				ref claim_deadline, ref onion_fields
 			} => {
@@ -864,6 +864,8 @@ impl Writeable for Event {
 						payment_preimage = Some(*preimage);
 					}
 				}
+				let skimmed_fee_opt = if counterparty_skimmed_fee_msat == 0 { None }
+					else { Some(counterparty_skimmed_fee_msat) };
 				write_tlv_fields!(writer, {
 					(0, payment_hash, required),
 					(1, receiver_node_id, option),
@@ -875,7 +877,7 @@ impl Writeable for Event {
 					(7, claim_deadline, option),
 					(8, payment_preimage, option),
 					(9, onion_fields, option),
-					(11, counterparty_skimmed_fee_msat, required),
+					(10, skimmed_fee_opt, option),
 				});
 			},
 			&Event::PaymentSent { ref payment_id, ref payment_preimage, ref payment_hash, ref fee_paid_msat } => {
@@ -1093,7 +1095,7 @@ impl MaybeReadable for Event {
 						(7, claim_deadline, option),
 						(8, payment_preimage, option),
 						(9, onion_fields, option),
-						(11, counterparty_skimmed_fee_msat_opt, option),
+						(10, counterparty_skimmed_fee_msat_opt, option),
 					});
 					let purpose = match payment_secret {
 						Some(secret) => PaymentPurpose::InvoicePayment {

pending_changelog/forward-underpaying-htlc.txt

@@ -0,0 +1,4 @@
+## Backwards Compat
+
+* Setting `ChannelConfig::accept_underpaying_htlcs` may break compatibility with versions of LDK
+	prior to 0.0.116, and unsetting the feature between restarts may lead to payment failures.