Add handle_message_received function in ChannelMessageHandler

- Handle behavior triggered when any message from any peer is received.
- Manage retry mechanism for InvoiceRequest messages in ChannelManager
  related to PendingOutboundPayments.
- Retrieve the InvoiceRequest, use a new reply path, and enqueue the
  messages for retry.
- Ensure retries of InvoiceRequest messages if initial attempts fail
  due to connection loss, retrying when back online and receiving messages
  from peers.

Author: shaavan

lightning-net-tokio/src/lib.rs

@@ -658,6 +658,7 @@ mod tests {
 		fn get_chain_hashes(&self) -> Option<Vec<ChainHash>> {
 			Some(vec![ChainHash::using_genesis_block(Network::Testnet)])
 		}
+		fn handle_message_received(&self) -> Result<(), ()> { Ok(()) }
 	}
 	impl MessageSendEventsProvider for MsgHandler {
 		fn get_and_clear_pending_msg_events(&self) -> Vec<MessageSendEvent> {

lightning/src/ln/channelmanager.rs

@@ -10132,6 +10132,21 @@ where
 			"Dual-funded channels not supported".to_owned(),
 			 msg.channel_id.clone())), *counterparty_node_id);
 	}
+
+	fn handle_message_received(&self) -> Result<(), ()> {
+		let invoice_requests = self.pending_outbound_payments.get_invoice_request_awaiting_invoice();
+		if invoice_requests.is_empty() { return Ok(());}
+
+		let reply_path = self.create_blinded_path()?;
+		let mut pending_offers_messages = self.pending_offers_messages.lock().unwrap();
+
+		for invoice_request in invoice_requests {
+			pending_offers_messages.extend(self.create_invoice_request_messages(
+				invoice_request, reply_path.clone()).map_err(|_| ())?);
+		}
+
+		Ok(())
+	}
 }
 
 impl<M: Deref, T: Deref, ES: Deref, NS: Deref, SP: Deref, F: Deref, R: Deref, L: Deref>

lightning/src/ln/msgs.rs

@@ -1550,6 +1550,13 @@ pub trait ChannelMessageHandler : MessageSendEventsProvider {
 	/// If it's `None`, then no particular network chain hash compatibility will be enforced when
 	/// connecting to peers.
 	fn get_chain_hashes(&self) -> Option<Vec<ChainHash>>;
+
+	/// Retries the [`InvoiceRequest`] message for pending outbound payments
+	/// that are still awaiting a [`Bolt12Invoice`].
+	///
+	/// [`InvoiceRequest`]: crate::offers::invoice_request::InvoiceRequest
+	/// [`Bolt12Invoice`]: crate::offers::invoice::Bolt12Invoice
+	fn handle_message_received(&self) -> Result<(), ()>;
 }
 
 /// A trait to describe an object which can receive routing messages.

lightning/src/ln/peer_handler.rs

@@ -379,6 +379,8 @@ impl ChannelMessageHandler for ErroringMessageHandler {
 	fn handle_tx_abort(&self, their_node_id: &PublicKey, msg: &msgs::TxAbort) {
 		ErroringMessageHandler::push_error(self, their_node_id, msg.channel_id);
 	}
+
+	fn handle_message_received(&self) -> Result<(), ()> { Ok(()) }
 }
 
 impl Deref for ErroringMessageHandler {
@@ -1742,6 +1744,8 @@ impl<Descriptor: SocketDescriptor, CM: Deref, RM: Deref, OM: Deref, L: Deref, CM
 			log_trace!(logger, "Received message {:?} from {}", message, log_pubkey!(their_node_id));
 		}
 
+		let _ = self.message_handler.chan_handler.handle_message_received();
+
 		let mut should_forward = None;
 
 		match message {

lightning/src/util/test_utils.rs

@@ -907,6 +907,8 @@ impl msgs::ChannelMessageHandler for TestChannelMessageHandler {
 	fn handle_tx_abort(&self, _their_node_id: &PublicKey, msg: &msgs::TxAbort) {
 		self.received_msg(wire::Message::TxAbort(msg.clone()));
 	}
+
+	fn handle_message_received(&self) -> Result<(), ()> { Ok(()) }
 }
 
 impl events::MessageSendEventsProvider for TestChannelMessageHandler {