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.
We have supported sending to any witness version since Electrum 3.0, using
addresses as specified in BIP-0173 (bech32 encoding).
BIP-0350 makes a breaking change in address encoding, and recommends using
(and using only) a new encoding (bech32m) for sending to witness version 1
and later. The address encoding for currently in use witness v0 addresses
remains the same, as in BIP-0173; following the BIP-0350 spec.
closes https://github.com/spesmilo/electrum/issues/6949
related:
cd3885c0fb/bip-0350.mediawikihttps://github.com/bitcoin/bitcoin/pull/20861
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.
