lnchannel: implement freezing channels (for receiving)

A bit weird, I know... :)
It allows for rebalancing our own channels! :P

electrum/gui/qt/channels_list.py

@@ -146,10 +146,15 @@ class ChannelsList(MyTreeView):
         cc.addAction(_("Long Channel ID"), lambda: self.place_text_on_clipboard(channel_id.hex(),
                                                                                 title=_("Long Channel ID")))
 
-        if not chan.is_frozen():
+        if not chan.is_frozen_for_sending():
-            menu.addAction(_("Freeze"), lambda: chan.set_frozen(True))
+            menu.addAction(_("Freeze (for sending)"), lambda: chan.set_frozen_for_sending(True))
         else:
-            menu.addAction(_("Unfreeze"), lambda: chan.set_frozen(False))
+            menu.addAction(_("Unfreeze (for sending)"), lambda: chan.set_frozen_for_sending(False))
+        if not chan.is_frozen_for_receiving():
+            menu.addAction(_("Freeze (for receiving)"), lambda: chan.set_frozen_for_receiving(True))
+        else:
+            menu.addAction(_("Unfreeze (for receiving)"), lambda: chan.set_frozen_for_receiving(False))
+
 
         funding_tx = self.parent.wallet.db.get_transaction(chan.funding_outpoint.txid)
         if funding_tx:
@@ -212,18 +217,22 @@ class ChannelsList(MyTreeView):
 
     def _update_chan_frozen_bg(self, *, chan: Channel, items: Sequence[QStandardItem]):
         assert self._default_item_bg_brush is not None
-        for col in [
+        # frozen for sending
-            self.Columns.LOCAL_BALANCE,
+        item = items[self.Columns.LOCAL_BALANCE]
-            self.Columns.REMOTE_BALANCE,
+        if chan.is_frozen_for_sending():
-            self.Columns.CHANNEL_STATUS,
+            item.setBackground(ColorScheme.BLUE.as_color(True))
-        ]:
+            item.setToolTip(_("This channel is frozen for sending. It will not be used for outgoing payments."))
-            item = items[col]
+        else:
-            if chan.is_frozen():
+            item.setBackground(self._default_item_bg_brush)
-                item.setBackground(ColorScheme.BLUE.as_color(True))
+            item.setToolTip("")
-                item.setToolTip(_("This channel is frozen. Frozen channels will not be used for outgoing payments."))
+        # frozen for receiving
-            else:
+        item = items[self.Columns.REMOTE_BALANCE]
-                item.setBackground(self._default_item_bg_brush)
+        if chan.is_frozen_for_receiving():
-                item.setToolTip("")
+            item.setBackground(ColorScheme.BLUE.as_color(True))
+            item.setToolTip(_("This channel is frozen for receiving. It will not be included in invoices."))
+        else:
+            item.setBackground(self._default_item_bg_brush)
+            item.setToolTip("")
 
     def update_can_send(self, lnworker: LNWallet):
         msg = _('Can send') + ' ' + self.parent.format_amount(lnworker.num_sats_can_send())\

electrum/lnchannel.py

@@ -392,18 +392,30 @@ class Channel(Logger):
     def is_redeemed(self):
         return self.get_state() == channel_states.REDEEMED
 
-    def is_frozen(self) -> bool:
+    def is_frozen_for_sending(self) -> bool:
-        """Whether the user has marked this channel as frozen.
+        """Whether the user has marked this channel as frozen for sending.
         Frozen channels are not supposed to be used for new outgoing payments.
         (note that payment-forwarding ignores this option)
         """
         return self.storage.get('frozen_for_sending', False)
 
-    def set_frozen(self, b: bool) -> None:
+    def set_frozen_for_sending(self, b: bool) -> None:
         self.storage['frozen_for_sending'] = bool(b)
         if self.lnworker:
             self.lnworker.network.trigger_callback('channel', self)
 
+    def is_frozen_for_receiving(self) -> bool:
+        """Whether the user has marked this channel as frozen for receiving.
+        Frozen channels are not supposed to be used for new incoming payments.
+        (note that payment-forwarding ignores this option)
+        """
+        return self.storage.get('frozen_for_receiving', False)
+
+    def set_frozen_for_receiving(self, b: bool) -> None:
+        self.storage['frozen_for_receiving'] = bool(b)
+        if self.lnworker:
+            self.lnworker.network.trigger_callback('channel', self)
+
     def _assert_can_add_htlc(self, *, htlc_proposer: HTLCOwner, amount_msat: int) -> None:
         """Raises PaymentFailure if the htlc_proposer cannot add this new HTLC.
         (this is relevant both for forwarding and endpoint)
@@ -437,11 +449,9 @@ class Channel(Logger):
         if amount_msat > LN_MAX_HTLC_VALUE_MSAT and not self._ignore_max_htlc_value:
             raise PaymentFailure(f"HTLC value over protocol maximum: {amount_msat} > {LN_MAX_HTLC_VALUE_MSAT} msat")
 
-    def can_pay(self, amount_msat: int) -> bool:
+    def can_pay(self, amount_msat: int, *, check_frozen=False) -> bool:
-        """Returns whether we can initiate a new payment of given value.
+        """Returns whether we can add an HTLC of given value."""
-        (we are the payer, not just a forwarding node)
+        if check_frozen and self.is_frozen_for_sending():
-        """
-        if self.is_frozen():
             return False
         try:
             self._assert_can_add_htlc(htlc_proposer=LOCAL, amount_msat=amount_msat)
@@ -449,6 +459,16 @@ class Channel(Logger):
             return False
         return True
 
+    def can_receive(self, amount_msat: int, *, check_frozen=False) -> bool:
+        """Returns whether the remote can add an HTLC of given value."""
+        if check_frozen and self.is_frozen_for_receiving():
+            return False
+        try:
+            self._assert_can_add_htlc(htlc_proposer=REMOTE, amount_msat=amount_msat)
+        except PaymentFailure:
+            return False
+        return True
+
     def should_try_to_reestablish_peer(self) -> bool:
         return channel_states.PREOPENING < self._state < channel_states.FORCE_CLOSING and self.peer_state == peer_states.DISCONNECTED
 

electrum/lnrouter.py

@@ -205,11 +205,12 @@ class LNPathFinder(Logger):
             is_mine = edge_channel_id in my_channels
             if is_mine:
                 if edge_startnode == nodeA:  # payment outgoing, on our channel
-                    if not my_channels[edge_channel_id].can_pay(amount_msat):
+                    if not my_channels[edge_channel_id].can_pay(amount_msat, check_frozen=True):
                         return
                 else:  # payment incoming, on our channel. (funny business, cycle weirdness)
                     assert edge_endnode == nodeA, (bh2u(edge_startnode), bh2u(edge_endnode))
-                    pass  # TODO?
+                    if not my_channels[edge_channel_id].can_receive(amount_msat, check_frozen=True):
+                        return
             edge_cost, fee_for_edge_msat = self._edge_cost(
                 edge_channel_id,
                 start_node=edge_startnode,

electrum/lnworker.py

@@ -1266,12 +1266,7 @@ class LNWallet(LNWorker):
                                if chan.short_channel_id is not None}
         # note: currently we add *all* our channels; but this might be a privacy leak?
         for chan in channels:
-            # check channel is open
+            if not chan.can_receive(amount_sat, check_frozen=True):
-            if chan.get_state() != channel_states.OPEN:
-                continue
-            # check channel has sufficient balance
-            # FIXME because of on-chain fees of ctx, this check is insufficient
-            if amount_sat and chan.balance(REMOTE) // 1000 < amount_sat:
                 continue
             chan_id = chan.short_channel_id
             assert isinstance(chan_id, bytes), chan_id