Rebuild manager forwarded htlcs maps from Channels

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index 080ecef..e2a3db8 100644
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -18267,6 +18267,76 @@ where
 			}
 		}
 
+		// Remove HTLCs from `forward_htlcs` if they are also present in `decode_update_add_htlcs`.
+		//
+		// In the future, the full set of pending HTLCs will be pulled from `Channel{Monitor}` data and
+		// placed in `ChannelManager::decode_update_add_htlcs` on read, to be handled on the next call
+		// to `process_pending_htlc_forwards`. This is part of a larger effort to remove the requirement
+		// of regularly persisting the `ChannelManager`. The new pipeline is supported for HTLC forwards
+		// received on LDK 0.3+ but not <= 0.2, so prune non-legacy HTLCs from `forward_htlcs`.
+		forward_htlcs_legacy.retain(|scid, pending_fwds| {
+			for fwd in pending_fwds {
+				let (prev_scid, prev_htlc_id) = match fwd {
+					HTLCForwardInfo::AddHTLC(htlc) => {
+						(htlc.prev_outbound_scid_alias, htlc.prev_htlc_id)
+					},
+					HTLCForwardInfo::FailHTLC { htlc_id, .. }
+					| HTLCForwardInfo::FailMalformedHTLC { htlc_id, .. } => (*scid, *htlc_id),
+				};
+				if let Some(pending_update_adds) = decode_update_add_htlcs.get_mut(&prev_scid) {
+					if pending_update_adds
+						.iter()
+						.any(|update_add| update_add.htlc_id == prev_htlc_id)
+					{
+						return false;
+					}
+				}
+			}
+			true
+		});
+		// Remove intercepted HTLC forwards if they are also present in `decode_update_add_htlcs`. See
+		// the above comment.
+		pending_intercepted_htlcs_legacy.retain(|id, fwd| {
+			let prev_scid = fwd.prev_outbound_scid_alias;
+			if let Some(pending_update_adds) = decode_update_add_htlcs.get_mut(&prev_scid) {
+				if pending_update_adds
+					.iter()
+					.any(|update_add| update_add.htlc_id == fwd.prev_htlc_id)
+				{
+					pending_events_read.retain(
+						|(ev, _)| !matches!(ev, Event::HTLCIntercepted { intercept_id, .. } if intercept_id == id),
+					);
+					return false;
+				}
+			}
+			if !pending_events_read.iter().any(
+				|(ev, _)| matches!(ev, Event::HTLCIntercepted { intercept_id, .. } if intercept_id == id),
+			) {
+				match create_htlc_intercepted_event(*id, &fwd) {
+					Ok(ev) => pending_events_read.push_back((ev, None)),
+					Err(()) => debug_assert!(false),
+				}
+			}
+			true
+		});
+		// Add legacy update_adds that were received on LDK <= 0.2 that are not present in the
+		// `decode_update_add_htlcs` map that was rebuilt from `Channel{Monitor}` data, see above
+		// comment.
+		for (scid, legacy_update_adds) in decode_update_add_htlcs_legacy.drain() {
+			match decode_update_add_htlcs.entry(scid) {
+				hash_map::Entry::Occupied(mut update_adds) => {
+					for legacy_update_add in legacy_update_adds {
+						if !update_adds.get().contains(&legacy_update_add) {
+							update_adds.get_mut().push(legacy_update_add);
+						}
+					}
+				},
+				hash_map::Entry::Vacant(entry) => {
+					entry.insert(legacy_update_adds);
+				},
+			}
+		}
+
 		let best_block = BestBlock::new(best_block_hash, best_block_height);
 		let flow = OffersMessageFlow::new(
 			chain_hash,
@@ -18296,7 +18366,7 @@ where
 			pending_intercepted_htlcs: Mutex::new(pending_intercepted_htlcs_legacy),
 
 			forward_htlcs: Mutex::new(forward_htlcs_legacy),
-			decode_update_add_htlcs: Mutex::new(decode_update_add_htlcs_legacy),
+			decode_update_add_htlcs: Mutex::new(decode_update_add_htlcs),
 			claimable_payments: Mutex::new(ClaimablePayments {
 				claimable_payments,
 				pending_claiming_payments: pending_claiming_payments.unwrap(),
diff --git a/lightning/src/ln/functional_test_utils.rs b/lightning/src/ln/functional_test_utils.rs
index ff33d75..3a5940c 100644
--- a/lightning/src/ln/functional_test_utils.rs
+++ b/lightning/src/ln/functional_test_utils.rs
@@ -1382,9 +1382,10 @@ macro_rules! reload_node {
 		$node.onion_messenger.set_async_payments_handler(&$new_channelmanager);
 	};
 	($node: expr, $chanman_encoded: expr, $monitors_encoded: expr, $persister: ident, $new_chain_monitor: ident, $new_channelmanager: ident) => {
+		let config = $node.node.get_current_config();
 		reload_node!(
 			$node,
-			test_default_channel_config(),
+			config,
 			$chanman_encoded,
 			$monitors_encoded,
 			$persister,
diff --git a/lightning/src/ln/reload_tests.rs b/lightning/src/ln/reload_tests.rs
index 2e9471a..cd56074 100644
--- a/lightning/src/ln/reload_tests.rs
+++ b/lightning/src/ln/reload_tests.rs
@@ -508,7 +508,7 @@ fn test_manager_serialize_deserialize_inconsistent_monitor() {
 
 #[cfg(feature = "std")]
 fn do_test_data_loss_protect(reconnect_panicing: bool, substantially_old: bool, not_stale: bool) {
-	use crate::ln::channelmanager::Retry;
+	use crate::ln::outbound_payment::Retry;
 	use crate::types::string::UntrustedString;
 	// When we get a data_loss_protect proving we're behind, we immediately panic as the
 	// chain::Watch API requirements have been violated (e.g. the user restored from a backup). The
@@ -1173,6 +1173,91 @@ fn removed_payment_no_manager_persistence() {
 	expect_payment_failed!(nodes[0], payment_hash, false);
 }
 
+#[test]
+fn manager_persisted_pre_outbound_edge_forward() {
+	do_manager_persisted_pre_outbound_edge_forward(false);
+}
+
+#[test]
+fn manager_persisted_pre_outbound_edge_intercept_forward() {
+	do_manager_persisted_pre_outbound_edge_forward(true);
+}
+
+fn do_manager_persisted_pre_outbound_edge_forward(intercept_htlc: bool) {
+	let chanmon_cfgs = create_chanmon_cfgs(3);
+	let node_cfgs = create_node_cfgs(3, &chanmon_cfgs);
+	let persister;
+	let new_chain_monitor;
+	let mut intercept_forwards_config = test_default_channel_config();
+	intercept_forwards_config.accept_intercept_htlcs = true;
+	let node_chanmgrs = create_node_chanmgrs(3, &node_cfgs, &[None, Some(intercept_forwards_config), None]);
+	let nodes_1_deserialized;
+	let mut nodes = create_network(3, &node_cfgs, &node_chanmgrs);
+
+	let chan_id_1 = create_announced_chan_between_nodes(&nodes, 0, 1).2;
+	let chan_id_2 = create_announced_chan_between_nodes(&nodes, 1, 2).2;
+
+	// Lock in the HTLC from node_a <> node_b.
+	let amt_msat = 5000;
+	let (mut route, payment_hash, payment_preimage, payment_secret) = get_route_and_payment_hash!(nodes[0], nodes[2], amt_msat);
+	if intercept_htlc {
+		route.paths[0].hops[1].short_channel_id = nodes[1].node.get_intercept_scid();
+	}
+	nodes[0].node.send_payment_with_route(route, payment_hash, RecipientOnionFields::secret_only(payment_secret), PaymentId(payment_hash.0)).unwrap();
+	check_added_monitors(&nodes[0], 1);
+	let updates = get_htlc_update_msgs(&nodes[0], &nodes[1].node.get_our_node_id());
+	nodes[1].node.handle_update_add_htlc(nodes[0].node.get_our_node_id(), &updates.update_add_htlcs[0]);
+	do_commitment_signed_dance(&nodes[1], &nodes[0], &updates.commitment_signed, false, false);
+
+	// Decode the HTLC onion but don't forward it to the next hop, such that the HTLC ends up in
+	// `ChannelManager::forward_htlcs` or `ChannelManager::pending_intercepted_htlcs`.
+	nodes[1].node.test_process_pending_update_add_htlcs();
+
+	// Disconnect peers and reload the forwarding node_b.
+	nodes[0].node.peer_disconnected(nodes[1].node.get_our_node_id());
+	nodes[2].node.peer_disconnected(nodes[1].node.get_our_node_id());
+
+	let node_b_encoded = nodes[1].node.encode();
+
+	let chan_0_monitor_serialized = get_monitor!(nodes[1], chan_id_1).encode();
+	let chan_1_monitor_serialized = get_monitor!(nodes[1], chan_id_2).encode();
+	reload_node!(nodes[1], node_b_encoded, &[&chan_0_monitor_serialized, &chan_1_monitor_serialized], persister, new_chain_monitor, nodes_1_deserialized);
+
+	reconnect_nodes(ReconnectArgs::new(&nodes[1], &nodes[0]));
+	let mut args_b_c = ReconnectArgs::new(&nodes[1], &nodes[2]);
+	args_b_c.send_channel_ready = (true, true);
+	args_b_c.send_announcement_sigs = (true, true);
+	reconnect_nodes(args_b_c);
+
+	// Forward the HTLC and ensure we can claim it post-reload.
+	nodes[1].node.process_pending_htlc_forwards();
+
+	if intercept_htlc {
+		let events = nodes[1].node.get_and_clear_pending_events();
+		assert_eq!(events.len(), 1);
+		let (intercept_id, expected_outbound_amt_msat) = match events[0] {
+			Event::HTLCIntercepted { intercept_id, expected_outbound_amount_msat, .. } => {
+				(intercept_id, expected_outbound_amount_msat)
+			},
+			_ => panic!()
+		};
+		nodes[1].node.forward_intercepted_htlc(intercept_id, &chan_id_2,
+			nodes[2].node.get_our_node_id(), expected_outbound_amt_msat).unwrap();
+		nodes[1].node.process_pending_htlc_forwards();
+	}
+	check_added_monitors(&nodes[1], 1);
+
+	let updates = get_htlc_update_msgs(&nodes[1], &nodes[2].node.get_our_node_id());
+	nodes[2].node.handle_update_add_htlc(nodes[1].node.get_our_node_id(), &updates.update_add_htlcs[0]);
+	do_commitment_signed_dance(&nodes[2], &nodes[1], &updates.commitment_signed, false, false);
+	expect_and_process_pending_htlcs(&nodes[2], false);
+
+	expect_payment_claimable!(nodes[2], payment_hash, payment_secret, amt_msat, None, nodes[2].node.get_our_node_id());
+	let path: &[&[_]] = &[&[&nodes[1], &nodes[2]]];
+	do_claim_payment_along_route(ClaimAlongRouteArgs::new(&nodes[0], path, payment_preimage));
+	expect_payment_sent(&nodes[0], payment_preimage, None, true, true);
+}
+
 #[test]
 fn test_reload_partial_funding_batch() {
 	let chanmon_cfgs = create_chanmon_cfgs(3);