When a payment fails, a payer needs to know when they can consider
a payment as fully-failed, and when only some of the HTLCs in the
payment have failed. This isn't possible with the current event
scheme, as discovered recently and as described in the previous
commit.
This adds a new event which describes when a payment is fully and
irrevocably failed, generating it only after the payment has
expired or been marked as expired with
`ChannelManager::mark_retries_exceeded` *and* all HTLCs for it
have failed. With this, a payer can more simply deduce when a
payment has failed and use that to remove payment state or
finalize a payment failure.
During event handling, ChannelManager methods may need to be called as
indicated in the Event documentation. Ensure that these calls are
idempotent for the same event rather than panicking. This allows users
to persist events for later handling without needing to worry about
processing the same event twice (e.g., if ChannelManager is not
persisted but the events were, the restarted ChannelManager would return
some of the same events).
A peer providing a channel_reserve_satoshis of 0 (or less than our
dust limit) is insecure, but only for them. Because some LSPs do it
with some level of trust of the clients (for a substantial UX
improvement), we explicitly allow it. Because its unlikely to
happen often in normal testing, we test it explicitly here.
A single PaymentSent event is generated when a payment is fulfilled.
This is occurs when the preimage is revealed on the first claimed HTLC.
For subsequent HTLCs, the event is not generated.
In order to score channels involved with a successful payments, the
scorer must be notified of each successful path involved in the payment.
Add a PaymentPathSuccessful event for this purpose. Generate it whenever
a part is removed from a pending outbound payment. This avoids duplicate
events when reconnecting to a peer.
In upcoming commits, we'll be making the payment secret and payment hash/preimage
derivable from info about the payment + a node secret. This means we don't
need to store any info about incoming payments and can eventually get rid of the
channelmanager::pending_inbound_payments map.
Scorer uses time to determine how much to penalize a channel after a
failure occurs. Parameterizing it by time cleans up the code such that
no-std support is in a single AlwaysPresent struct, which implements the
Time trait. Time is implemented for std::time::Instant when std is
available.
This parameterization also allows for deterministic testing since a
clock could be devised to advance forward as needed.
NetworkGraph is owned by NetGraphMsgHandler, but DefaultRouter requires
a reference to it. Introduce shared ownership to NetGraphMsgHandler so
that both can use the same NetworkGraph.
As payments fail, the channel responsible for the failure may be
penalized. Implement Scorer::payment_path_failed to penalize the failed
channel using a configured penalty. As time passes, the penalty is
reduced using exponential decay, though penalties will accumulate if the
channel continues to fail. The decay interval is also configurable.
The payment_hash may not uniquely identify the payment if it has been
reused. Include the payment_id in PaymentSent events so it can
correlated with the send_payment call.
This stores and tracks HTLC payee information with HTLCSource info,
allowing us to provide it back to the user if the HTLC fails and
ensuring persistence by keeping it with the HTLC itself as it
passes between Channel and ChannelMonitor.
A payee can be identified by a pubkey and optionally have an associated
set of invoice features and route hints. Use this in get_route instead
of three separate parameters. This may be included in PaymentPathFailed
later to use when finding a new route.
Failed payments may be retried, but calling get_route may return a Route
with the same failing path. Add a routing::Score trait used to
parameterize get_route, which it calls to determine how much a channel
should be penalized in terms of msats willing to pay to avoid the
channel.
Also, add a Scorer struct that implements routing::Score with a constant
constant penalty. Subsequent changes will allow for more robust scoring
by feeding back payment path success and failure to the scorer via event
handling.
Exposing a `RwLock<HashMap<>>` directly was always a bit strange,
and in upcoming changes we'd like to change the internal
datastructure in `ChainMonitor`.
Further, the use of `RwLock` and `HashMap` meant we weren't able
to expose the ChannelMonitors themselves to users in bindings,
leaving a bindings/rust API gap.
Thus, we take this opportunity go expose ChannelMonitors directly
via a wrapper, hiding the internals of `ChainMonitor` behind
getters. We also update tests to use the new API.
The interface for get_route will change to take a scorer. Using
get_route_and_payment_hash whenever possible allows for keeping the
scorer inside get_route_and_payment_hash rather than at every call site.
Replace get_route with get_route_and_payment_hash wherever possible.
Additionally, update get_route_and_payment_hash to use the known invoice
features and the sending node's logger.
This makes it more practical for users to track channels prior to
funding, especially if the channel fails because the peer rejects
it for a parameter mismatch.
During the event of a channel close, if the funding transaction
is yet to be broadcasted then a DiscardFunding event is issued
along with the ChannelClose event.
When we detect a channel `is_shutdown()` or call on it
`force_shutdown()`, we notify the user with a Event::ChannelClosed
informing about the id and closure reason.
