[fuzz] Check that channels don't get stuck in chanmon_consistency

This adds a new command string in the chanmon_consistency fuzzer
which tests that, once all pending HTLCs are settled, at least one
side of a channel can still send funds.

While this should have caught the recent(ish) spec bug where
channels could get stuck, I did not attempt to reproduce said bug
with this patch.

diff --git a/fuzz/src/chanmon_consistency.rs b/fuzz/src/chanmon_consistency.rs
index 441931d654c4d1a5c4d365571bf28b397897dc05..377ac8d7b5702c439e84dcc7b1db898645483428 100644 (file)
--- a/fuzz/src/chanmon_consistency.rs
+++ b/fuzz/src/chanmon_consistency.rs
@@ -542,7 +542,9 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
                                        bc_events.clear();
                                        new_events
                                } else { Vec::new() };
+                               let mut had_events = false;
                                for event in events.iter().chain(nodes[$node].get_and_clear_pending_msg_events().iter()) {
+                                       had_events = true;
                                        match event {
                                                events::MessageSendEvent::UpdateHTLCs { ref node_id, updates: CommitmentUpdate { ref update_add_htlcs, ref update_fail_htlcs, ref update_fulfill_htlcs, ref update_fail_malformed_htlcs, ref update_fee, ref commitment_signed } } => {
                                                        for dest in nodes.iter() {
@@ -599,6 +601,7 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
                                                _ => panic!("Unhandled message event"),
                                        }
                                }
+                               had_events
                        } }
                }
 
@@ -678,6 +681,7 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
                                                } else { Ordering::Equal }
                                        } else { Ordering::Equal }
                                });
+                               let had_events = !events.is_empty();
                                for event in events.drain(..) {
                                        match event {
                                                events::Event::PaymentReceived { payment_hash, payment_secret, amt } => {
@@ -697,6 +701,7 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
                                                _ => panic!("Unhandled event"),
                                        }
                                }
+                               had_events
                        } }
                }
 
@@ -764,18 +769,18 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
                                }
                        },
 
-                       0x10 => process_msg_events!(0, true),
-                       0x11 => process_msg_events!(0, false),
-                       0x12 => process_events!(0, true),
-                       0x13 => process_events!(0, false),
-                       0x14 => process_msg_events!(1, true),
-                       0x15 => process_msg_events!(1, false),
-                       0x16 => process_events!(1, true),
-                       0x17 => process_events!(1, false),
-                       0x18 => process_msg_events!(2, true),
-                       0x19 => process_msg_events!(2, false),
-                       0x1a => process_events!(2, true),
-                       0x1b => process_events!(2, false),
+                       0x10 => { process_msg_events!(0, true); },
+                       0x11 => { process_msg_events!(0, false); },
+                       0x12 => { process_events!(0, true); },
+                       0x13 => { process_events!(0, false); },
+                       0x14 => { process_msg_events!(1, true); },
+                       0x15 => { process_msg_events!(1, false); },
+                       0x16 => { process_events!(1, true); },
+                       0x17 => { process_events!(1, false); },
+                       0x18 => { process_msg_events!(2, true); },
+                       0x19 => { process_msg_events!(2, false); },
+                       0x1a => { process_events!(2, true); },
+                       0x1b => { process_events!(2, false); },
 
                        0x1c => {
                                if !chan_a_disconnected {
@@ -875,6 +880,62 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
                        0x5c => { send_hop_payment(&nodes[0], &nodes[1], chan_a, &nodes[2], chan_b, 1, &mut payment_id); },
                        0x5d => { send_hop_payment(&nodes[2], &nodes[1], chan_b, &nodes[0], chan_a, 1, &mut payment_id); },
 
+                       0xff => {
+                               // Test that no channel is in a stuck state where neither party can send funds even
+                               // after we resolve all pending events.
+                               // First make sure there are no pending monitor updates, resetting the error state
+                               // and calling channel_monitor_updated for each monitor.
+                               *monitor_a.update_ret.lock().unwrap() = Ok(());
+                               *monitor_b.update_ret.lock().unwrap() = Ok(());
+                               *monitor_c.update_ret.lock().unwrap() = Ok(());
+
+                               if let Some((id, _)) = monitor_a.latest_monitors.lock().unwrap().get(&chan_1_funding) {
+                                       nodes[0].channel_monitor_updated(&chan_1_funding, *id);
+                               }
+                               if let Some((id, _)) = monitor_b.latest_monitors.lock().unwrap().get(&chan_1_funding) {
+                                       nodes[1].channel_monitor_updated(&chan_1_funding, *id);
+                               }
+                               if let Some((id, _)) = monitor_b.latest_monitors.lock().unwrap().get(&chan_2_funding) {
+                                       nodes[1].channel_monitor_updated(&chan_2_funding, *id);
+                               }
+                               if let Some((id, _)) = monitor_c.latest_monitors.lock().unwrap().get(&chan_2_funding) {
+                                       nodes[2].channel_monitor_updated(&chan_2_funding, *id);
+                               }
+
+                               // Next, make sure peers are all connected to each other
+                               if chan_a_disconnected {
+                                       nodes[0].peer_connected(&nodes[1].get_our_node_id(), &Init { features: InitFeatures::empty() });
+                                       nodes[1].peer_connected(&nodes[0].get_our_node_id(), &Init { features: InitFeatures::empty() });
+                                       chan_a_disconnected = false;
+                               }
+                               if chan_b_disconnected {
+                                       nodes[1].peer_connected(&nodes[2].get_our_node_id(), &Init { features: InitFeatures::empty() });
+                                       nodes[2].peer_connected(&nodes[1].get_our_node_id(), &Init { features: InitFeatures::empty() });
+                                       chan_b_disconnected = false;
+                               }
+
+                               for i in 0..std::usize::MAX {
+                                       if i == 100 { panic!("It may take may iterations to settle the state, but it should not take forever"); }
+                                       // Then, make sure any current forwards make their way to their destination
+                                       if process_msg_events!(0, false) { continue; }
+                                       if process_msg_events!(1, false) { continue; }
+                                       if process_msg_events!(2, false) { continue; }
+                                       // ...making sure any pending PendingHTLCsForwardable events are handled and
+                                       // payments claimed.
+                                       if process_events!(0, false) { continue; }
+                                       if process_events!(1, false) { continue; }
+                                       if process_events!(2, false) { continue; }
+                                       break;
+                               }
+
+                               // Finally, make sure that at least one end of each channel can make a substantial payment.
+                               assert!(
+                                       send_payment(&nodes[0], &nodes[1], chan_a, 10_000_000, &mut payment_id) ||
+                                       send_payment(&nodes[1], &nodes[0], chan_a, 10_000_000, &mut payment_id));
+                               assert!(
+                                       send_payment(&nodes[1], &nodes[2], chan_b, 10_000_000, &mut payment_id) ||
+                                       send_payment(&nodes[2], &nodes[1], chan_b, 10_000_000, &mut payment_id));
+                       },
                        _ => test_return!(),
                }