- better error handling: previously we stopped all attempts on any of
TRAMPOLINE_EXPIRY_TOO_SOON, UNKNOWN_NEXT_PEER, TEMPORARY_NODE_FAILURE.
Instead we should retry (but see code comments).
- previously payments failed if ALL of the following criteria applied:
- sender is paying via trampoline, but not via the ACINQ node (which is
special cased)
- receiver only has private channels and has put r_tags into invoice, along
with setting the trampoline feature bit in the invoice, however the receiver
is not connected to any trampoline forwarders directly
The sender would then assume that the private routing hints in the invoice
correspond to trampoline forwarders.
- also, previously if both the sender and the recipient used trampoline and
they shared a trampoline forwarder (that they were both connected to), the
private channels the recipient had (with nodes other than the shared TF)
would never be attempted.
Previously for incoming transports, the diagnostic_name (for log messages)
was just "responder" -- not sufficient to distinguish peers.
We now use the pubkey instead.
For outgoing transports it is f"{host}:{port}" (unchanged).
We could just use the pubkey for both uniformly; but it is quite long, and
it is hard to distinguish them at a glance.
Note that this will not fix the value for already existing channels
that have been created with onchain backup; one would need a wallet_db
upgrade in order to fix them (probably not worth the effort).
- 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.
This is re the channel update for the incoming direction of our own channels.
This message can only come from the counterparty itself so maybe the sig check
is redundant... but for sanity I think we should check it anyway.
Counter-intuitively, the motivation is to be able to *send* more htlcs,
for MPP trickery. We don't offer more htlcs than this limit, to be
conservative with what we send, and to interoperate with clightning.
defaults of other clients:
eclair: 30
clightning: 30
lnd: 483
- 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
- raise OnionRoutingFailure whenever we want to fail a htlc
- catch that exception in htlc_switch
- this will avoid code duplication in the case of trampoline
- 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.
If we get a revack after reestablish, but the fail_htlc was already
committed in a previous app-session, the fail_htlc will not be re-sent and
we will not have the reason (as it's not persisted).
fixes#6675
