Adds liquidity hints for the sending capabilities of routing channels in the
graph. The channel blacklist is incorporated into liquidity hints.
Liquidity hints are updated when a payment fails with a temporary
channel failure or when it succeeds. Liquidity hints are used to give a
penalty in the _edge_cost heuristics used by the pathfinding algorithm.
The base penalty in (_edge_cost) is removed because it is now part of the
liquidity penalty. We don't return early from get_distances, as we want
to explore all channels.
- use_recoverable_channel is a user setting, available
only in standard wallets with a 'segwit' seed_type
- if enabled, 'lightning_xprv' is derived from seed
- otherwise, wallets use the existing 'lightning_privkey2'
Recoverable channels:
- channel recovery data is added funding tx using an OP_RETURN
- recovery data = 4 magic bytes + node id[0:16]
- recovery data is chacha20 encrypted using funding_address as nonce.
(this will allow to fund multiple channels in the same tx)
GUI:
- whether channels are recoverable is shown in wallet info dialog.
- if the wallet can have recoverable channels but has an old node_id,
users are told to close their channels and restore from seed
to have that feature.
Note that for a required feature, BOLT-09 allows setting either:
- only the REQ bit
- both the REQ bit and the OPT bit
Hence, when checking if a feature is supported by e.g. an invoice, both
bits should be checked.
Note that in lnpeer.py, in self.features specifically, REQ implies OPT,
as it is set by ln_compare_features.
- trampoline is enabled by default in config, to prevent download of `gossip_db`.
(if disabled, `gossip_db` will be downloaded, regardless of the existence of channels)
- if trampoline is enabled:
- the wallet can only open channels with trampoline nodes
- already-existing channels with non-trampoline nodes are frozen for sending.
- there are two types of trampoline payments: legacy and end-to-end (e2e).
- we decide to perform legacy or e2e based on the invoice:
- we use trampoline_routing_opt in features to detect Eclair and Phoenix invoices
- we use trampoline_routing_hints to detect Electrum invoices
- when trying a legacy payment, we add a second trampoline to the path to preserve privacy.
(we fall back to a single trampoline if the payment fails for all trampolines)
- the trampoline list is hardcoded, it will remain so until `trampoline_routing_opt` feature flag is in INIT.
- there are currently only two nodes in the hardcoded list, it would be nice to have more.
- similar to Phoenix, we find the fee/cltv by trial-and-error.
- if there is a second trampoline in the path, we use the same fee for both.
- the final spec should add fee info in error messages, so we will be able to fine-tune fees
- LNWorker is notified about htlc events and creates payment events.
- LNWorker._pay is a while loop that calls create_routes_from_invoice.
- create_route_from_invoices should decide whether to split the payment,
using graph knowledge and feedback from previous attempts (not in this commit)
- data structures for payment logs are simplified into a single type, HtlcLog
Upfront shutdown script is a script provided on channel opening,
which will be used by the peer to enforce us closing to this script
on collaborative channel close.
before:
node_id -> set of (host, port, ts)
after:
node_id -> NetAddress -> timestamp
Look at e.g. add_recent_peer; we only want to store
the last connection time, not all of them.
non-positive values do not make sense... but some nodes set it to 0
and if we enforce >= 1 then we can't open channels with those...
lnchannel._assert_can_add_htlc enforces positive values for HTLCs in any case.
SomberNight