In current commit big shift have been made in direction of unit testable
payments scenarios. Previosly two additional structures have been added
which had been spreaded in the lnd package before, and now we apply
them in the lnd itself:
1. ChannelLink - is an interface which represents the subsystem for
managing the incoming htlc requests, applying the changes to the
channel, and also propagating/forwarding it to htlc switch.
2. Switch - is a central messaging bus for all incoming/outgoing htlc's.
The goal of the switch is forward the incoming/outgoing htlc messages
from one channel to another, and also propagate the settle/fail htlc
messages back to original requester.
With this abtractions the folowing schema becomes nearly complete:
abstraction
^
|
| - - - - - - - - - - - - Lightning - - - - - - - - - - - - -
|
| (Switch) (Switch) (Switch)
| Alice <-- channel link --> Bob <-- channel link --> Carol
|
| - - - - - - - - - - - - - TCP - - - - - - - - - - - - - - -
|
| (Peer) (Peer) (Peer)
| Alice <----- tcp conn --> Bob <---- tcp conn -----> Carol
In this commit usage of the pending packet queue have been added.
This queue will consume the downstream packets if state machine return
the error that we do not have enough capacity for htlc in commitment
transaction. Upon receiving settle/fail payment descriptors - add htlc
have been removed, we release the slot, and process pending add htlc
requests.
In this commit pending packet queue have been added. This queue
consumes the htlc packet, store it inside the golang list and send it
to the pending channel upon release notification.
Step #5 in making htlcManager (aka channelLink) testable:
Combine all that have been done so far and add test framework for channel
links which allow unit test:
* message ordering
* detect redundant messages
* single hop payment
* multihop payment
* several cancel payment scenarios
In order to be able to use the DeriveRevocationRoot in the createChannel
function inside the htlcswicth package we need to make it public.
NOTE: The original lnwallet.CreateChannel function haven't been
sufficient as far it not takes the private keys as input.
add rhash to the payment descriptor when receiving the settle htlc in
order to be able to pass it during settle htlc packet generation and
later find the user pending payment by rhash without additional hashing.
Because processing of onion blob have been moved in another place we
could get rid of the variables which are not needed any more.
NOTE: pendingBatch have been replaced with batchCounter variable, but
it should be removed at all, because number of pending batch updates
might be counted by the state machine itself.
Step №4 in making htlcManager (aka channelLink) testable:
This step consist of two:
1. Start using the hop iterator abstraction, the concrete
implementation of which will be added later, basically it will we the
same sphinx onion packet processor, but wrapped in hop iterator
abstraction.
2. The RevokAndAck processing part have been replaced by the
"processLockedInHtlcs" function which implement the same logic, but make
it a bit simpler.
Such changes will allow as to get rid of the the unnecessary variables.
Short: such abstraction give as ability to test the channel link in the
future.
Long: hop iterator represents the entity which is be able to give payment
route hop by hop. This interface will be used to have an abstraction
over the algorithm which we use to determine the next hope in htlc route
and also helps the unit test to create mock representation of such
algorithm which uses simple array of hops.
Step №2 in making htlcManager (aka channelLink) testable:
Implement the ChannelLink interface which is needed to use it in pair
with htlc switch. With this commit channel link impelements interface,
but isn't able to operate properly yet.
In this commit all initial code which will be transformed into channel
link have been added. Rather than changing the in the same commit is
better to create the standalone commit, in order to see the changes
which have been applied to relocated code.
This commit gives the start for making the htlc manager and htlc switch
testable. The testability of htlc switch have been achieved by mocking
all external subsystems. The concrete list of updates:
1. create standalone package for htlc switch.
2. add "ChannelLink" interface, which represent the previous htlc link.
3. add "Peer" interface, which represent the remote node inside our
subsystem.
4. add htlc switch config to htlc switch susbystem, which stores the
handlers which are not elongs to any of the above interfaces.
With this commit we are able test htlc switch even without having
the concrete implementation of Peer, ChannelLink structures, they will
be added later.
Add hop id structure wich represent the next lnd node in sphinx payment
route. This structure will be removed when we switch to use the channel
id as the pointers to the htlc update.
In this commit we made state machine to be responsible for returning
proper available balance - amount of satoshi which we able to use at
current moment. This will help us in constrction channel link
abstraction.
In this commit severe bug have been fixed which allows the state of the
nodes to be desychnorinesed in the moments of high htlc flow. We limit
the number of the htlc which we can add to commitment transaction
to half of the available capcity. This change fixes the bug when
commimtment transaction on the verge of being full, in this case race
condition might occures and remote htlc will be rejected, but at the
same time they will be added on remote side, the same situiation will
happen with htlc we have added, which cause the commitment transactions
to be different.
This commit adds a set of additional comments around the new channel
closure workflow and also includes two minor fixes:
* The error when parsing a signature previously wasn’t checked and is
now.
* As a result, we should only track the new signature iff it parses
correctly and we agree to the details as specified w.r.t to the fee
for the final closing transaction.
Additionally, as set of TODO’s has been added detailing the additional
work that needs to be done before the closing workflow is fully
compliant with the specification.
This commit changes the cooperative channel close workflow to comply
with the latest spec. This adds steps to handle and send shutdown
messages as well as moving responsibility for sending the channel close
message from the initiator to the responder.
This commit fixes a bug in the switch which would manifest only in the
case of a multi-hop payment which _reused_ the same payment hash over
several distinct payments. In this case, after the first few payments
were settled, the circuit would be deleted, meaning that once the
remainder of the payment were forwarded, the switch wouldn’t know to
_whom_ to settle them to.
We fix this issue by using the refCount field to only garbage collect a
circuit after there are no more references.
This commit fixes an issue that would at times cause the htlcManager
which manages the link that’s the final hop to settle in an HTLC flow.
Previously, a case would arise wherein a set of HTLC’s were settled to,
but not properly committed to in the commitment transaction of the
remote node. This wasn’t an issue with HTLC’s which were added but
uncleared, as that batch was tracked independently.
In order to fix this issue, we now track pending HTLC settles
independently. This is a temporary fix, as has been noted in a TODO
within this commit.
This commit fixed an issue in the htlcManager goroutine which manages
channel state updates. Due to lack of a mutex protecting the two maps
written in the goroutine launched to forward HTLC’s to the switch.
This issue was detected by golang’s runtime which is able to detect
invalid concurrent map writes.
This commit modifies the funding workflow slightly to move the querying
to the fee estimator (for the new channel) into the fundingManager
rather than within the LightningWallet layer. When querying to
FeePerWeight, we now multiply by 1000 to arrive at fee-per-kw.
Additionally, we now also properly thread through the fee-per-kw
offered by the initiator the to the responder of the channel workflow.
This commit modifies the fee calculation logic when creating or
accepting a new commitment transaction to use the set FeePerKw within
the channel rather then re-query the estimator each time. The prior
behavior was benign as we currently use a static fee estimator, but the
dynamic setting this could’ve caused a state divergence.
This commit corrects an error in the scaling as currently implemented
in the default static fee estimator. The spec draft has an error and
erroneously recommends multiplying by 4 to arrive at the fee-per-weight
from the fee-per-byte. This is incorrect as with the segwit block-size
increase, the ratio is 1/4 rather than 4.
This commit modifies the coin selection logic around selecting inputs
for a funding transaction to query the fee estimator directly (and use
fee-per-byte), rather than use the fee estimate which was passed into
the context.
We also use the value passed into the InitChannelReservation method
directly rather than make a call to the fee estimator. With this
change, the responder to a funding workflow will now properly adopt the
fee-per-kw suggested by the funder of the channel.
The remote balance in the case of a single funder workflow is simply
what ever the pushSat amount is. The capacity - fundingAmt in this
scenario would always be zero, so we simply just set it directly to
pushSat.
This commit modifies the name of a field in the OpenChannel struct to
better reflect its actual usage within this protocol. The FeePerKw
represents the amount of satoshi to be paid as fees per kilo-weight.
This field is set at the opening of a transaction and will be able to
be updated properly via the usage of the update_fee method.
