- all forwarding types use the same flow
- forwarding callback returns a htlc_key or None
- forwarding info is persisted in lnworker:
- ongoing_forwardings
- downstream to upstream htlc_key
- htlc_key -> error_bytes
- a node scid alias is derived from the node ID
- the channel opening fee is sent in a TLV field of open_channel
- the server requires htlc settlement before broadcasting
(server does not trust client)
- introduce PaymentFeeBudget, which contains limits for fee budget and cltv budget
- when splitting a payment,
- the fee budget is linearly distributed between the parts
- this resolves a FIXME in lnrouter ("FIXME in case of MPP")
- the cltv budget is simply copied
- we could also add other kinds of budgets later, e.g. for the num in-flight htlcs
- resolves TODO in lnworker ("todo: compare to the fee of the actual route we found")
The convention is that edges (start_node -> edge_node) store
the policy/fees for the *start_node*.
This is what the non-trampoline edges were already using (for a long time),
but the trampoline ones were off-by-one (policy was for end_node),
which was then worked around in multiple places, to correct for...
i.e. I think because of all the workarounds, there was no actual bug,
but it was just very confusing.
Also note that the prior usage of trampoline edges would not work if
we (sender) were not directly connected to a TF (trampoline-forwarder)
but had extra edges in the route to even get to the first TF.
Having the policy corresponding to the start_node of the edge would work
even in that case.
Note: this issue is currently not detected in python unittests,
it shows up only in regtest, and is not currently tested.
One would need to use a proper LNWallet instance in unit tests.
propageate back to the sender.
lnworker: in htlc_fulfilled and htlc_failed, return early if the
htlc was forwarded, so that we do not trigger invoice callbacks
- see comment in lnaddr.py
- Previously we used feature bit 50/51 for trampoline.
The spec subsequently defined fbit 50/51 as option_zeroconf, which
requires fbit 46/47 (option_scid_alias) to also be set.
We moved the non-standard trampoline fbit to a different int.
However, old wallets might have old invoices saved that set fbit 50/51
for trampoline, and those would not have the dependent bit set.
Invoices are parsed at wallet-open, so if the parser ran these checks,
those wallets could not be opened.
- note: we could potentially also run lnaddr.validate_and_compare_features
when saving new invoices into the wallet but this is not done here
Somewhat a follow-up to 649ce979ab.
This adds some safety belts so we don't accidentally sign a tx that
contains a dummy address.
Specifically we check that tx does not contain output for dummy addr:
- in wallet.sign_transaction
- in network.broadcast_transaction
The second one is perhaps redundant, but I think it does not hurt.
- when creating an invoice, if we had multiple chans with the same trampoline,
were putting duplicate t-hints into the invoice
- when paying an invoice that had duplicate t-hints, we would sometimes
construct invalid paths (SRC>T1->T1->DST)
