disable mpp flags in invoice creation if jit channel is required, check against available liquidity if we need a jit channel

Author: f321x

electrum/lnpeer.py

@@ -1870,7 +1870,7 @@ def log_fail_reason(reason: str):
         next_chan = self.lnworker.get_channel_by_short_id(next_chan_scid)
 
         if self.lnworker.features.supports(LnFeatures.OPTION_ZEROCONF_OPT):
-            next_peer = self.lnworker.get_peer_by_scid_alias(next_chan_scid)
+            next_peer = self.lnworker.get_peer_by_static_jit_scid_alias(next_chan_scid)
         else:
             next_peer = None
 

electrum/lnworker.py

@@ -1152,7 +1152,7 @@ async def handle_onchain_state(self, chan: Channel):
                 self.logger.info('REBROADCASTING CLOSING TX')
                 await self.network.try_broadcasting(force_close_tx, 'force-close')
 
-    def get_peer_by_scid_alias(self, scid_alias: bytes) -> Optional[Peer]:
+    def get_peer_by_static_jit_scid_alias(self, scid_alias: bytes) -> Optional[Peer]:
         for nodeid, peer in self.peers.items():
             if scid_alias == self._scid_alias_of_node(nodeid):
                 return peer
@@ -1161,7 +1161,7 @@ def _scid_alias_of_node(self, nodeid: bytes) -> bytes:
         # scid alias for just-in-time channels
         return sha256(b'Electrum' + nodeid)[0:8]
 
-    def get_scid_alias(self) -> bytes:
+    def get_static_jit_scid_alias(self) -> bytes:
         return self._scid_alias_of_node(self.node_keypair.pubkey)
 
     @log_exceptions
@@ -2112,11 +2112,15 @@ def get_bolt11_invoice(
 
         assert amount_msat is None or amount_msat > 0
         timestamp = int(time.time())
-        routing_hints = self.calc_routing_hints_for_invoice(amount_msat, channels=channels)
-        self.logger.info(f"creating bolt11 invoice with routing_hints: {routing_hints}")
+        needs_jit: bool = self.receive_requires_jit_channel(amount_msat)
+        routing_hints = self.calc_routing_hints_for_invoice(amount_msat, channels=channels, needs_jit=needs_jit)
+        self.logger.info(f"creating bolt11 invoice with routing_hints: {routing_hints}, jit: {needs_jit}")
         invoice_features = self.features.for_invoice()
         if not self.uses_trampoline():
             invoice_features &= ~ LnFeatures.OPTION_TRAMPOLINE_ROUTING_OPT_ELECTRUM
+        if needs_jit:
+            # jit only works with single htlcs, mpp will cause LSP to open channels for each htlc
+            invoice_features &= ~ LnFeatures.BASIC_MPP_OPT & ~ LnFeatures.BASIC_MPP_REQ
         payment_secret = self.get_payment_secret(payment_hash)
         amount_btc = amount_msat/Decimal(COIN*1000) if amount_msat else None
         if expiry == 0:
@@ -2505,14 +2509,14 @@ def htlc_failed(
             else:
                 self.logger.info(f"waiting for other htlcs to fail (phash={payment_hash.hex()})")
 
-    def calc_routing_hints_for_invoice(self, amount_msat: Optional[int], channels=None):
+    def calc_routing_hints_for_invoice(self, amount_msat: Optional[int], channels=None, needs_jit=False):
         """calculate routing hints (BOLT-11 'r' field)"""
         routing_hints = []
-        if self.config.ZEROCONF_TRUSTED_NODE:
+        if needs_jit:
             node_id, rest = extract_nodeid(self.config.ZEROCONF_TRUSTED_NODE)
-            alias_or_scid = self.get_scid_alias()
+            alias_or_scid = self.get_static_jit_scid_alias()
             routing_hints.append(('r', [(node_id, alias_or_scid, 0, 0, 144)]))
-            # no need for more
+            # no need for more because we cannot receive enough through the others and mpp is disabled for jit
             channels = []
         else:
             if channels is None:
@@ -2665,6 +2669,21 @@ def recv_capacity(chan):
         can_receive_msat = max(recv_chan_msats)
         return Decimal(can_receive_msat) / 1000
 
+    def receive_requires_jit_channel(self, amount_msat: Optional[int]) -> bool:
+        """Returns true if we cannot receive the amount and have set up a trusted LSP node.
+        Cannot work reliably with 0 amount invoices as we don't know if we are able to receive it.
+        """
+        # a trusted zeroconf node is configured
+        if (self.config.ZEROCONF_TRUSTED_NODE
+                # the zeroconf node is a peer, it doesn't make sense to request a channel from an offline LSP
+                and extract_nodeid(self.config.ZEROCONF_TRUSTED_NODE)[0] in self.peers
+                # we cannot receive the amount specified
+                and ((amount_msat and self.num_sats_can_receive() < (amount_msat // 1000))
+                    # or we cannot receive anything, and it's a 0 amount invoice
+                    or (not amount_msat and self.num_sats_can_receive() < 1))):
+            return True
+        return False
+
     def _suggest_channels_for_rebalance(self, direction, amount_sat) -> Sequence[Tuple[Channel, int]]:
         """
         Suggest a channel and amount to send/receive with that channel, so that we will be able to receive/send amount_sat