Previously if a payment was sent with custom records attached, path
finding wouldn't perform a check whether the final node was capable of
receiving custom records in a tlv payload.
This commit prepares for more manipulation of custom records. A list of
tlv.Record types is more difficult to use than the more basic
map[uint64][]byte.
Furthermore fields and variables are renamed to make them more
consistent.
A unified policy differs between local channels and other channels on
the network. There is more information available for local channels and
this is used in the unified policy.
Previously we used the pathfinding source pubkey to determine whether to
apply the local channel logic or not. If queryroutes is executed with a
source node that isn't the self node, this wouldn't work.
When the (virtual) payment attempt cost is set to zero, probabilities
are no longer a factor in determining the best route. In case of routes
with equal costs, we'd just go with the first one found. This commit
refines this behavior by picking the route with the highest probability.
So even though probability doesn't affect the route cost, it is still
used as a tie breaker.
This prepares for routing to self. When checking the condition at the
start, the loop would terminate immediately because the source is equal
to the target.
This commit modifies the FetchPayment method to return MPPayment structs
converted from the legacy on-disk format. This allows us to attach the
HTLCs to the events given to clients subscribing to the outcome of an
HTLC.
This commit also bubbles up to the routerrpc/router_server, by
populating HTLCAttempts in the response and extracting the legacy route
field from the HTLCAttempts.
Previously we used the a priori probability also for our own untried
channels. This led to local channels that had seen a success already
being prioritized over untried local channels. In some cases, depending
on the configured payment attempt cost, this could lead to the payment
taking a two hop route while a direct payment was also possible.
An InvalidOnionPayload implies that the onion was successfully received
by the reporting node, but that they were unable to extract the
contents. Since we assume our own behavior is correct, this mostly
likely poins to an error in the reporter's implementation or that we
sent an unknown required type. Therefore we only penalize that single
hop, and consider the failure terminal if the receiver reported it.
Probabilities are no longer returned for querymc calls. To still provide
some insight into the mission control internals, this commit adds a new
rpc that calculates a success probability estimate for a specific node
pair and amount.
This prepares for decoupling the result interpretation of a single
payment attempt from the information stored in mission control memory
on the history of a node pair. A planned follow-up where we store both
the last success and last failure requires this decoupling.
In this commit we change path finding to no longer consider all channels
between a pair of nodes individually. We assume that nodes forward
non-strict and when we attempt a connection between two nodes, we don't
want to try multiple channels because their policies may not be identical.
Having distinct policies for channel to the same peer is against the
recommendation in the spec, but it happens in the wild. Especially since
we recently changed the default cltv delta value.
What this commit introduces is a unified policy. This can be looked upon
as the greatest common denominator of all policies and should maximize
the probability of getting the payment forwarded.
distance map now holds the edge the current path is coming from,
removing the need for next map.
Both distance map and distanceHeap now hold pointers instead of the full
struct to reduce allocations and copies.
Both these changes reduced path finding time by ~5% and memory usage by
~2mb.
Pre-sizing these structures avoids a lot of map resizing, which causes
copies and rehashing of entries. We mostly know that the map won't
exceed that size, and it doesn't affect memory usage in any significant
way.
Calling `ForEachNode` hits the DB, and allocates and parses every node
in the graph. Walking the channels also loads nodes from the DB, so this
meant that each node was read/parsed/allocated several times per run.
This reduces runtime by ~10ms and memory usage by ~4mb.
This commit changes mission control to partially base the estimated
probability for untried connections on historical results obtained in
previous payment attempts. This incentivizes routing nodes to keep all
of their channels in good shape.
Probability estimates are amount dependent. Previously we assumed an
amount, but that starts to make less sense when we make probability more
dependent on amounts in the future.
This commit modifies the interpretation of node-level failures.
Previously only the failing node was marked. With this commit, also the
incoming and outgoing connections involved in the route are marked as
failed.
The change prepares for the removal of node-level failures in mission
control probability estimation.
This commit changes the in-memory structure of the mission control
state. It prepares for calculation of a node probability. For this we
need to be able to efficiently look up the last results for all channels
of a node.
With the introduction of the max CLTV limit parameter, nodes are able to
reject HTLCs that exceed it. This should also be applied to path
finding, otherwise HTLCs crafted by the same node that exceed it never
left the switch. This wasn't a big deal since the previous max CLTV
limit was ~5000 blocks. Once it was lowered to 1008, the issue became
more apparent. Therefore, all of our path finding attempts now have a
restriction of said limit in in order to properly carry out HTLCs to the
network.
In the process of moving to use the new package, we no longer need to
fetch the outpoint directly, and instead only need to pass the funding
transaction into the new verification logic.
In this commit, we update the router and link to support users
updating the max HTLC policy for their channels. By updating these internal
systems before updating the RPC server and lncli, we protect users from
being shown an option that doesn't actually work.
The policy update logic that resided part in the gossiper and
part in the rpc server is extracted into its own object.
This prepares for additional validation logic to be added for policy
updates that would otherwise make the gossiper heavier.
It is also a small first step towards separation of our own channel data
from the rest of the graph.
Extends the invalid payment details failure with the new accept height
field. This allows sender to distinguish between a genuine invalid
details situation and a delay caused by intermediate nodes.
Currently the underlying array backing the hop's TLVRecords is modified
when combining custom records with the primitive forwarding info. This
commit uses a fresh slice to prevent modifications from mutating the
hop itself.
This commit modifies paymentLifecycle so that it not only feeds
failures into mission control, but successes as well.
This allows for more accurate probability estimates. Previously,
the success probability for a successful pair and a pair with
no history was equal. There was no force that pushed towards
previously successful routes.
In this commit, we extend the path finding to be able to recognize when
a node needs the new TLV format, or the legacy format based on the
feature bits they expose. We also extend the `LightningPayment` struct
to allow the caller to specify an arbitrary set of TLV records which can
be used for a number of use-cases including various variants of
spontaneous payments.
In this commit, we extend the Hop struct to carry an arbitrary set of
TLV values, and add a new field that allows us to distinguish between
the modern and legacy TLV payload.
We add a new `PackPayload` method that will be used to encode the
combined required routing TLV fields along any set of TLV fields that
were specified as part of path finding.
Finally, the `ToSphinxPath` has been extended to be able to recognize if
a hop needs the modern, or legacy payload.
This commit overhauls the interpretation of failed payments. It changes
the interpretation rules so that we always apply the strongest possible
set of penalties, without making assumptions that would hurt good nodes.
Main changes are:
- Apply different rule sets for intermediate and final nodes. Both types
of nodes have different sets of failures that we expect. Penalize nodes
that send unexpected failure messages.
- Distinguish between direct payments and multi-hop payments. For direct
payments, we can infer more about the performance of our peer because we
trust ourselves.
- In many cases it is impossible for the sender to determine which of
the two nodes in a pair is responsible for the failure. In this
situation, we now penalize bidirectionally. This does not hurt the good
node of the pair, because only its connection to a bad node is
penalized.
- Previously we always penalized the outgoing connection of the
reporting node. This is incorrect for policy related failures. For
policy related failures, it could also be that the reporting node
received a wrongly crafted htlc from its predecessor. By penalizing the
incoming channel, we surely hit the responsible node.
- FailExpiryTooSoon is a failure that could have been caused by any node
up to the reporting node by delaying forwarding of the htlc. We don't
know which node is responsible, therefore we now penalize all node pairs
in the route.
When an undecryptable failure comes back for a payment attempt, we
previously only penalized our own outgoing connection. However,
any node could have caused this failure. It is therefore better to
penalize all node connections along the route. Then at least we know for
sure that we will hit the responsible node.
This commit updates existing tests to not rely on mission control for
pruning of local channels. Information about local channels should
already be up to date before path finding starts. If not, the problem
should be fixed where bandwidth hints are set up.
