Also suggest a submarine swap if the user creates a 0 amount invoice and
has 0 sat incoming liquidity as it won't be possible to receive
anything.
Users potentially just open a channel, then want to create a lightning invoice
without amount like they are used to from onchain addresses, and then
wonder why receiving doesn't work. So we should at least propose a swap
if there is no inbound liquidity at all.
Removes the persisted payment info from lnworker once a swap got failed.
Stops persisting the OnionRoutingFailure as it is sufficient to delete
the payment info to fail potential incoming htlcs.
Deletes stored swap leftovers in lnworker and SwapManager
Adds `max_cltv` and `max_fee_msat` parameters to the `lnpay` cli command which allow to
specify the maximum total locktime of the payment and the maximum
absolute fee budget. This is enabled by
constructing a custom `PaymentFeeBudget` object in the lnpay command and
passing it as argument to `LNWallet.pay_invoice()`.
Allowing to specify a `max_cltv` value can be useful for certain
usecases, e.g. see https://github.com/spesmilo/electrum/issues/10056.
Closes#10056
fixes broken test_trampoline_mpp_consolidation caused to fail by
https://github.com/spesmilo/electrum/pull/9845 by allowing single
channel splits for trampoline payments if TEST_FORCE_MPP is Trues
as the test relies on mpp through a single channel (it tests mpp and
there is only a single channel on the graph).
part configs
I noticed certain ln payments become very unreliable. These payments are ~21k sat, from gossip to gossip sender, with direct, unannounced channel.
Due to the recent fix https://github.com/spesmilo/electrum/pull/9723 `LNPathFinder.get_shortest_path_hops()` will not use channels for the last hop of a route anymore that aren't also passed to it in `my_sending_channels`:
```python
if edge_startnode == nodeA and my_sending_channels: # payment outgoing, on our channel
if edge_channel_id not in my_sending_channels:
continue
```
Conceptually this makes sense as we only want to send through `my_sending_channels`, however if the only channel between us and the receiver is a direct channel that we got from the r_tag and it's not passed in `my_sending_channel` it's not able to construct a route now.
Previously this type of payment worked as `get_shortest_path_hops()` knew of the direct channel between us and `nodeB` from the invoices r_tag and then just used this channel as the route, even though it was (often) not contained in `my_sending_channels`.
`my_sending_channels`, passed in `LNWallet.create_routes_for_payment()` is either a single channel or all our channels, depending on `is_multichan_mpp`:
```python
for sc in split_configurations:
is_multichan_mpp = len(sc.config.items()) > 1
```
This causes the unreliable, random behavior as `LNWallet.suggest_splits()` is supposed to `exclude_single_part_payments` if the amount is > `MPP_SPLIT_PART_MINAMT_SAT` (5000 sat).
As `mpp_split.py suggest_splits()` is selecting channels randomly, and then removes single part configs, it sometimes doesn't return a single configuration, as it removes single part splits, and also removes multi part splits if a part is below 10 000 sat:
```python
if target_parts > 1 and config.is_any_amount_smaller_than_min_part_size():
continue
```
This will result in a fallback to allow single part payments:
```python
split_configurations = get_splits()
if not split_configurations and exclude_single_part_payments:
exclude_single_part_payments = False
split_configurations = get_splits()
```
Then the payment works as all our channels are passed as `my_sending_channels` to `LNWallet.create_routes_for_payment()`.
However sometimes this fallback doesn't happen, because a few mpp configurations found in the first iteration of `suggest_splits` have been kept, e.g. [10500, 10500], but at the same time most others have been removed as they crossed the limit, e.g. [11001, 9999], (which happens sometimes with payments ~20k sat), this makes `suggest_splits` return very few usable channels/configurations (sometimes just one or two, even with way more available channels).
This makes payments in this range unreliable as we do not retry to generate new split configurations if the following path finding fails with `NoPathFound()`, and there is no single part configuration that allows the path finding to access all channels. Also this does not only affect direct channel payments, but all gossip payments in this amount range.
There seem to be multiple ways to fix this, i think one simple approach is to just disable `exclude_single_part_payments` if the splitting loop already begins to sort out configs on the second iteration (the first split), as this indicates that the amount may be too small to split within the given limits, and prevents the issue of having only few valid splits returned and not going into the fallback. However this also results in increased usage of single part payments.
the update_fee logic for lightning channels was not adapted to anchor
channels causing us to send update_fee with a eta target of 2 blocks.
This causes force closes when there are mempool spikes as the fees we
try to update to are a lot higher than e.g. eclair uses. Eclair will
force close if our fee is 10x > than their fee.
The option to add a 2nd trampoline hop to legacy trampoline payments requires too much space in the trampoline onion.
Because the trampoline onion has only limited space of 400b and the payload with 2nd t hop and no r_tags already requires 392b it is essentially unusable for payments that require routing hints to be included in the onion
(because the receiver has no direct channel to the 2nd trampoline node)
as there is no space left to include them (1r_tag == ~52b).
