rework on_channel_closed in LNWorker:

- use detect_who_closed; this allows us to redeem to_remote of breach ctx
 - do not redeem to_local of breach ctx, because it is redundant with lnwatcher
 - rename a few methods

electrum/lnchannel.py

@@ -46,8 +46,7 @@ from .lnutil import (Outpoint, LocalConfig, RemoteConfig, Keypair, OnlyPubkeyKey
                     HTLC_TIMEOUT_WEIGHT, HTLC_SUCCESS_WEIGHT, extract_ctn_from_tx_and_chan, UpdateAddHtlc,
                     funding_output_script, SENT, RECEIVED, LOCAL, REMOTE, HTLCOwner, make_commitment_outputs,
                     ScriptHtlc, PaymentFailure, calc_onchain_fees, RemoteMisbehaving, make_htlc_output_witness_script)
-from .lnsweep import create_sweeptxs_for_their_just_revoked_ctx
-from .lnsweep import create_sweeptxs_for_our_latest_ctx, create_sweeptxs_for_their_latest_ctx
+from .lnsweep import create_sweeptxs_for_their_revoked_ctx
 from .lnhtlc import HTLCManager
 
 
@@ -168,6 +167,7 @@ class Channel(Logger):
 
         self.local_commitment = None
         self.remote_commitment = None
+        self.sweep_info = None
 
     def get_payments(self):
         out = {}
@@ -186,13 +186,9 @@ class Channel(Logger):
         ctn = extract_ctn_from_tx_and_chan(ctx, self)
         assert self.signature_fits(ctx), (self.hm.log[LOCAL])
         self.local_commitment = ctx
-        if self.sweep_address is not None:
-            self.local_sweeptxs = create_sweeptxs_for_our_latest_ctx(self, self.local_commitment, self.sweep_address)
 
     def set_remote_commitment(self):
         self.remote_commitment = self.current_commitment(REMOTE)
-        if self.sweep_address is not None:
-            self.remote_sweeptxs = create_sweeptxs_for_their_latest_ctx(self, self.remote_commitment, self.sweep_address)
 
     def open_with_first_pcp(self, remote_pcp, remote_sig):
         self.remote_commitment_to_be_revoked = self.pending_commitment(REMOTE)
@@ -460,7 +456,7 @@ class Channel(Logger):
             return
         outpoint = self.funding_outpoint.to_str()
         ctx = self.remote_commitment_to_be_revoked  # FIXME can't we just reconstruct it?
-        sweeptxs = create_sweeptxs_for_their_just_revoked_ctx(self, ctx, per_commitment_secret, self.sweep_address)
+        sweeptxs = create_sweeptxs_for_their_revoked_ctx(self, ctx, per_commitment_secret, self.sweep_address)
         for prev_txid, tx in sweeptxs.items():
             if tx is not None:
                 self.lnwatcher.add_sweep_tx(outpoint, prev_txid, str(tx))

electrum/lnsweep.py

@@ -56,8 +56,8 @@ def maybe_create_sweeptx_for_their_ctx_to_local(ctx: Transaction, revocation_pri
     return sweep_tx
 
 
-def create_sweeptxs_for_their_just_revoked_ctx(chan: 'Channel', ctx: Transaction, per_commitment_secret: bytes,
-                                               sweep_address: str) -> Dict[str,Transaction]:
+def create_sweeptxs_for_their_revoked_ctx(chan: 'Channel', ctx: Transaction, per_commitment_secret: bytes,
+                                          sweep_address: str) -> Dict[str,Transaction]:
     """Presign sweeping transactions using the just received revoked pcs.
     These will only be utilised if the remote breaches.
     Sweep 'to_local', and all the HTLCs (two cases: directly from ctx, or from HTLC tx).
@@ -135,12 +135,8 @@ class ChannelClosedBy(Enum):
     UNKNOWN = auto()
 
 
-class ChannelCloseSituationReport(NamedTuple):
-    closed_by: ChannelClosedBy
-    is_breach: Optional[bool]
 
-
-def detect_how_channel_was_closed(chan: 'Channel', ctx: Transaction) -> ChannelCloseSituationReport:
+def detect_who_closed(chan: 'Channel', ctx: Transaction) -> ChannelClosedBy:
     ctn = extract_ctn_from_tx_and_chan(ctx, chan)
     our_conf, their_conf = get_ordered_channel_configs(chan=chan, for_us=True)
 
@@ -193,19 +189,19 @@ def detect_how_channel_was_closed(chan: 'Channel', ctx: Transaction) -> ChannelC
     to_local_address, to_remote_address, is_breach = get_to_local_and_to_remote_addresses_for_our_ctx()
     if (to_local_address and ctx.get_output_idx_from_address(to_local_address) is not None
             or to_remote_address and ctx.get_output_idx_from_address(to_remote_address) is not None):
-        return ChannelCloseSituationReport(closed_by=ChannelClosedBy.US, is_breach=is_breach)
+        return ChannelClosedBy.US
 
     # their ctx?
     to_local_address, to_remote_address, is_breach = get_to_local_and_to_remote_addresses_for_their_ctx()
     if (to_local_address and ctx.get_output_idx_from_address(to_local_address) is not None
             or to_remote_address and ctx.get_output_idx_from_address(to_remote_address) is not None):
-        return ChannelCloseSituationReport(closed_by=ChannelClosedBy.THEM, is_breach=is_breach)
+        return ChannelClosedBy.THEM
 
-    return ChannelCloseSituationReport(closed_by=ChannelClosedBy.UNKNOWN, is_breach=None)
+    return ChannelClosedBy.UNKNOWN
 
 
-def create_sweeptxs_for_our_latest_ctx(chan: 'Channel', ctx: Transaction,
-                                       sweep_address: str) -> Dict[str,Transaction]:
+def create_sweeptxs_for_our_ctx(chan: 'Channel', ctx: Transaction,
+                                sweep_address: str) -> Dict[str,Transaction]:
     """Handle the case where we force close unilaterally with our latest ctx.
     Construct sweep txns for 'to_local', and for all HTLCs (2 txns each).
     'to_local' can be swept even if this is a breach (by us),
@@ -277,8 +273,8 @@ def create_sweeptxs_for_our_latest_ctx(chan: 'Channel', ctx: Transaction,
     return txs
 
 
-def create_sweeptxs_for_their_latest_ctx(chan: 'Channel', ctx: Transaction,
-                                         sweep_address: str) -> Dict[str,Transaction]:
+def create_sweeptxs_for_their_ctx(chan: 'Channel', ctx: Transaction,
+                                  sweep_address: str) -> Dict[str,Transaction]:
     """Handle the case when the remote force-closes with their ctx.
     Regardless of it is a breach or not, construct sweep tx for 'to_remote'.
     If it is a breach, also construct sweep tx for 'to_local'.
@@ -313,18 +309,7 @@ def create_sweeptxs_for_their_latest_ctx(chan: 'Channel', ctx: Transaction,
     other_payment_privkey = ecc.ECPrivkey.from_secret_scalar(other_payment_privkey)
 
     txs = {}
-    if per_commitment_secret:  # breach
-        # to_local
-        other_revocation_privkey = derive_blinded_privkey(other_conf.revocation_basepoint.privkey,
-                                                          per_commitment_secret)
-        this_delayed_pubkey = derive_pubkey(this_conf.delayed_basepoint.pubkey, their_pcp)
-        sweep_tx = maybe_create_sweeptx_for_their_ctx_to_local(ctx=ctx,
-                                                               revocation_privkey=other_revocation_privkey,
-                                                               to_self_delay=other_conf.to_self_delay,
-                                                               delayed_pubkey=this_delayed_pubkey,
-                                                               sweep_address=sweep_address)
-        if sweep_tx:
-            txs[sweep_tx.prevout(0)] = sweep_tx
+    # to_local is handled by lnwatcher
     # to_remote
     sweep_tx = maybe_create_sweeptx_for_their_ctx_to_remote(ctx=ctx,
                                                             sweep_address=sweep_address,

electrum/lnworker.py

@@ -46,6 +46,7 @@ from .lnrouter import RouteEdge, is_route_sane_to_use
 from .address_synchronizer import TX_HEIGHT_LOCAL
 from . import lnsweep
 from .lnsweep import ChannelClosedBy
+from .lnsweep import create_sweeptxs_for_their_ctx, create_sweeptxs_for_our_ctx
 
 if TYPE_CHECKING:
     from .network import Network
@@ -511,24 +512,24 @@ class LNWallet(LNWorker):
         # remove from channel_db
         if chan.short_channel_id is not None:
             self.channel_db.remove_channel(chan.short_channel_id)
-        # detect who closed
-        assert closing_tx, f"no closing tx... {repr(closing_tx)}"
-        sitrep = lnsweep.detect_how_channel_was_closed(chan, closing_tx)
-        if sitrep.closed_by == ChannelClosedBy.US:
-            self.logger.info(f'we force closed {funding_outpoint}. sitrep: {repr(sitrep)}')
-            encumbered_sweeptxs = chan.local_sweeptxs
-        elif sitrep.closed_by == ChannelClosedBy.THEM and sitrep.is_breach is False:
-            self.logger.info(f'they force closed {funding_outpoint}. sitrep: {repr(sitrep)}')
-            encumbered_sweeptxs = chan.remote_sweeptxs
-        else:
-            self.logger.info(f'not sure who closed {funding_outpoint} {closing_txid}. sitrep: {repr(sitrep)}')
-            return
-        # sweep
-        for prevout, spender in spenders.items():
-            e_tx = encumbered_sweeptxs.get(prevout)
-            if e_tx is None:
-                continue
-            if spender is not None:
+
+        # detect who closed and set sweep_info
+        if chan.sweep_info is None:
+            closed_by = lnsweep.detect_who_closed(chan, closing_tx)
+            if closed_by == ChannelClosedBy.US:
+                self.logger.info(f'we force closed {funding_outpoint}.')
+                chan.sweep_info = create_sweeptxs_for_our_ctx(chan, closing_tx, chan.sweep_address)
+            elif closed_by == ChannelClosedBy.THEM:
+                self.logger.info(f'they force closed {funding_outpoint}.')
+                chan.sweep_info = create_sweeptxs_for_their_ctx(chan, closing_tx, chan.sweep_address)
+            else:
+                self.logger.info(f'not sure who closed {funding_outpoint} {closing_txid}.')
+                chan.sweep_info = {}
+            self.logger.info(f'{repr(chan.sweep_info)}')
+
+        # create and broadcast transaction
+        for prevout, e_tx in chan.sweep_info.items():
+            if spenders.get(prevout) is not None:
                 self.logger.info(f'outpoint already spent {prevout}')
                 continue
             prev_txid, prev_index = prevout.split(':')