This commit removes the overflowQueue from the link. We do so in order
to promote better UX for senders, so that HTLCs are failed faster when
the commitment is full. This gives the sender the opportunity to try
another, more open path, rather than perceive the HTLC as being stuck.
At the same time, we remove the total number of active goroutines in lnd
by a factor of N where N is the number of active channels.
This commit is preparation for the test added in the subsequent commit.
We modify makeHoldPayment to return any failures direectly when trying
to add an HTLC to the switch. This lets us know that the HTLC was indeed
sent without failure when the method returns.
A following commits will move/modify callsites of AckPacket, Start, and
Stop, none of which use the return value and ultimately cause the linter
to complain. However, none of these in-memory operations can fail so we
just remove the returned errors altogether.
The linter complains about not checking the return value from
WipeChannel in certain places. Instead of checking we simply remove the
returned error because the in-memory modifications cannot fail.
This commit changes the switch to only log an error if update_fail_htlc
comes in and closeCircuit returns ErrUnknownCircuit. Rationale
being that only settles should hit this code path, anything else
is a result of a link flap and should be treated as an error.
This commit modifies updateCommitTx to error with ErrLinkShuttingDown
when we try to send a ContractUpdate on the htlcUpdates chan and the
link has closed the quit chan. It also changes the order of the call
to ackDownStreamPackets and contract update call for consistency since
the packets should be acknowledged before the link goes down.
This commit changes the fallback in NextLocalHtlcIndex to
RemoteCommitment since the LocalHtlcIndex field lags behind
on the LocalCommitment. Without this bug fix, open circuits
would get prematurely trimmed, resulting in more erroneous
logs. A test case is included to check that the fix works.
This commit adds link failure notifications for failures which occur
on our incoming link. These failures may be receives which we failed or
forwards which we could not parse.
Add notifications for local initiated sends settles and forwarding
failures. As with link failures, local send settles and forwarding
failures are reported directly to the router so must have their own
notification handling.
Notify link failures for our own payments. Separate handling code is
required for local payment link failures because we do not pass these
failures back through the switch (like we do for link failures for
forwards), but rather send them straight back to the router. Our own
sends have the payment ID saved in the incoming htlc ID of the packet's
incoming circuit. This change replaces that value with for the sake
of consistent notifying of sends and receives from our node.
This commit adds notifications for htlcs which are forwarded through
our node. Forwards are notified when the htlc is added on our ougoing
link, settles when we send a settle message to the downstream peer.
If a failure occurs, we check whether it occurred at our node, then
notify a link or forwarding failure accordingly.
Note that this change also adds forward event notifications for sends
which are initiated by our node because the handling code for adding
a htlc which originates from our node is the same as that for handling
forwards. Htlcs for our locally initiated sends have our internal pid
set in the incoming htlcs id field, so we extract this value and notify
with a zero htlc id to be consistent with receives (which have zero
outgoing circuits). Subsequent settles or failures are not noitfied
for local sends in this commit, and will be handled in a follow up.
This commit sets more fields on the htlcPacket created to fail adding
a htlc packet to the switch for notification purposes. This new data is
copied by value from the original packet. The packet is then failed
back to the peer that forwarded us the packet, which is handled by
handledownstream packet. The values added to the packet are not used
in the handling of a failed packet.
In this commit, a htlcNotifier interface is added to allow for easy
unit testing. Instances of the HtlcNotifier are added to the server,
switch and link.
This commit adds a HTLCNotifier to htlcswitch which HTLC events
will be piped through to provide clients with subscriptions to
HTLC level events.
The event types added are forward events (which occur for sends
from and forwards through our node), forward failues (when a
send or forward fails down the line), settles for forwards or
receives to our node and link failures which occur when a htlc
is failed at our node (which may occur for a send, receive or
foreward).
Since we want to handle the edge case where paying the HTLC fee would
take the initiator below the reserve, we move the subtraction of the
reserve into availableBalance where this calculation will be performed.
This commit enables the user to specify he is not interested in
automatically close channels with pending payments that their
corresponding htlcs have timed-out.
By requiring a configurable grace period uptime of our node
before closing such channels, we give a chance to the other node to
properly cancel the htlc and avoid unnecessary on-chain transaction.
In mobile it is very important for the user experience as otherwise
channels will be force closed more frequently.
This commit adds LinkErrors with failure details to htlcs which fail on
our incoming link. This change is made with the intention of notifying
detailed htlc failure reasons in sendHTLCError. The FailureDetail
interface is implemented on FailureResolutionResults so that they can
directly be used to enrich LinkErrors. sendHtlcError is updated to
take a LinkError in preparation for the addition of a htlcnotifier
which will notify the detail of the error.
This commit adds a linkError field to track the value of failures
which occur at our node. This field is set when local payments or
multi hop htlcs fail in the switch or on our outgoing link. This
addition is required for the addition of a htlc notifier which will
notify these failures in handleDownstreamPacket.
The passing of link error to failAddPacket removes the need for an
additional error field, because the link error's failure detail will
contain any additional metadata. In the places where the failure detail
does not cover all the metadata that was previously supplied by addr
err, the error is logged before calling failAddPacket so that this
change does not reduce the amount of information we log.
Add a FailureDetail interface which allows us have different kinds of
failures for link errors. This interface will be used to cover failures
that occur when on invoice payment, because the errors have already
been enumerated in the invoices package.
Rename FailureDetail in a separate commit so that a FailureDetail
interface can be introduced in the following commit.
OutgoingFailureOnionDecode is renamed to OutgoingFailureDecodeError
to specifically indicate that we could not decode the wire
failure that our payment experienced.
This commit repalces the htlcResolution struct with an interface.
This interface is implemeted by failure, settle and accept resolution
structs. Only settles and fails are exported because the existing
code that handles htlc resolutions uses a nil resolution to indicate
that a htlc was accepted. The accept resolution is used internally
to report on the resolution result of the accepted htlc, but a nil
resolution is surfaced. Further refactoring of all the functions
that call NotifyExitHopHtlc to handle a htlc accept case (rather than
having a nil check) is required.
Add a CheckCircularForward function which detects packets which are
forwards over the same incoming and outgoing link, and errors if the
node is configured to disallow forwards of this nature. This check is
added to increase the cost of a liquidity lockup attack, because it
increases the length of the route required to lock up an individual
node's bandwidth. Since nodes are currently limited to 20 hops,
increasing the length of the route needed to lock up capital increases
the number of malicious payments an attacker will have to route, which
increases the capital requirement of the attack overall.
Update the ChannelLink interface to specifically
return the LinkError struct. This error implements
the ClearTextError interface, so will be picked
up as a routing realted error by the router.
With LinkErrors implemented, the switch now
returns a LinkError for all failures on our
incoming/outgoing link and ForwardingError when
the failure occurs down the line.
Update the type check used for checking local payment
failures to check on the ClearTextError interface rather
than on the ForwardingError type. This change prepares
for splitting payment errors up into Link and Forwarding
errors.
This change introduces a LinkError implementation
of the ClearTextError interface. This error is intended
to represent failures which occur on our incoming and
outgoing link when sending, receiving and forwarding
htlcs. Paired with ForwardingError, which is represents
failures that did not occur at our node, this error
covers all non-opaque errors that the switch experiences.
This commit adds a ClearTextError interface
which is implemented by non-opaque errors that
we know the underlying wire failure message for.
This interface is implemented by ForwardingErrors,
because we can fully decrypt the onion blob to
obtain the underlying failure reason. This interface
will also be implemented by errors which originate
at our node in following commits, because we know
the failure reason when we fail the htlc.
The lnwire interface is un-embedded in the
ForwardingError struct in favour of implementing
this interface. This change is made to protect
against accidental passing of a ForwardingError
to the wire, where the embedded FailureMessage
interface will present as wire failure but
will not serialize properly.
Add a constructor for the creation of forwarding errors.
A special constructor is added for the case where we have
an unknown wire failure, and must set a nil failure message.
We abstract away how keys are generated for the different channel types
types (currently tweak(less)).
Intention is that more of the logic that is unique for each commitment
type lives in commitment.go, making the channel state machine oblivious
to the keys and outputs being created on the commitment tx for a given
channel state.
This commit adds a getResolutionFailure function
which returns an appropriate wire failure based
on the outcome of a htlc resolution. It also updates
the MissionControlStore test to ensure that lnd
can handle failures which occur due to mpp timeout.
