AaronFiore/electrum
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lnworker: rework num_sats_can_receive and routing_hints_for_invoice

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follow-up https://github.com/spesmilo/electrum/pull/7818

- note it matters whether a sender pays us end-to-end-trampoline or just via legacy
  - consider: Alice has 0.1 BTC recv cap in chan1 and 1 BTC recv cap in chan2, both with border-node T1
    - if sender is paying e2e trampoline, it can realistically pay even ~1.1 BTC, as T1 can resplit the HTLCs
    - if sender is paying legacy, it will have a hard time trying to pay more than 1 BTC, in practice
      - although note if T1 has implemented non-strict-forwarding (see BOLT-04), achieving 1 BTC is easy,
        as T1 can redirect HTLCs (but cannot split them, in this case)
  - to make num_sats_can_receive realistic, it assumes the legacy case
- To calc num_sats_can_receive, we sort our channels in decreasing order of receive-capacities, iterate over them
  and calculate a running sum - we stop adding channels when the next chan's recv cap is small compared to
  the running total.
- When putting routing hints in an invoice, we do the same, with the added condition that we keep adding channels
  if their recv cap is larger than the invoice amount.
  - consider: Alice has 0.1 BTC recv cap in chan1 with Bob, and 1 BTC recv cap in chan2 with Carol
    - if Alice wants to recv 100 sats, it is useful to add hints for both channels into the invoice, for redundancy
    - if Alice wants to recv 0.9 BTC, it is questionable whether adding the smaller chan is useful - the code here won't add it
This commit is contained in:
SomberNight
2022-05-19 18:28:04 +02:00
parent 232e38e27d
commit dd5cb2a5c1
2 changed files with 43 additions and 39 deletions
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2
electrum/tests/test_lnpeer.py
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@@ -243,7 +243,7 @@ class MockLNWallet(Logger, NetworkRetryManager[LNPeerAddr]):
get_channel_by_id = LNWallet.get_channel_by_id
channels_for_peer = LNWallet.channels_for_peer
calc_routing_hints_for_invoice = LNWallet.calc_routing_hints_for_invoice
border_nodes_that_can_receive = LNWallet.border_nodes_that_can_receive
get_channels_to_include_in_invoice = LNWallet.get_channels_to_include_in_invoice
handle_error_code_from_failed_htlc = LNWallet.handle_error_code_from_failed_htlc
is_trampoline_peer = LNWallet.is_trampoline_peer
wait_for_received_pending_htlcs_to_get_removed = LNWallet.wait_for_received_pending_htlcs_to_get_removed