lnrouter: filter out unsuitable channels

electrum/lnbase.py

@@ -14,6 +14,7 @@ from typing import List
 
 import aiorpcx
 
+from .crypto import sha256
 from . import bitcoin
 from . import ecc
 from .ecc import sig_string_from_r_and_s, get_r_and_s_from_sig_string
@@ -921,22 +922,8 @@ class Peer(PrintError):
         hops_data += [OnionHopsDataSingle(OnionPerHop(b"\x00"*8, amount_msat.to_bytes(8, "big"), (final_cltv_expiry_without_deltas).to_bytes(4, "big")))]
         onion = new_onion_packet([x.node_id for x in route], secret_key, hops_data, associated_data)
         amount_msat += total_fee
-        # FIXME this below will probably break with multiple HTLCs
-        msat_local = chan.balance(LOCAL) - amount_msat
-        msat_remote = chan.balance(REMOTE) + amount_msat
+        chan.check_can_pay(amount_msat)
         htlc = {'amount_msat':amount_msat, 'payment_hash':payment_hash, 'cltv_expiry':final_cltv_expiry_with_deltas}
-        # FIXME if we raise here, this channel will not get blacklisted, and the payment can never succeed,
-        # as we will just keep retrying this same path. using the current blacklisting is not a solution as
-        # then no other payment can use this channel either.
-        # we need finer blacklisting -- e.g. a blacklist for just this "payment session"?
-        # or blacklist entries could store an msat value and also expire
-        if len(chan.htlcs(LOCAL, only_pending=True)) + 1 > chan.config[REMOTE].max_accepted_htlcs:
-            raise PaymentFailure('too many HTLCs already in channel')
-        if htlcsum(chan.htlcs(LOCAL, only_pending=True)) + amount_msat > chan.config[REMOTE].max_htlc_value_in_flight_msat:
-            raise PaymentFailure('HTLC value sum would exceed max allowed: {} msat'.format(chan.config[REMOTE].max_htlc_value_in_flight_msat))
-        if msat_local < 0:
-            # FIXME what about channel_reserve_satoshis? will the remote fail the channel if we go below? test.
-            raise PaymentFailure('not enough local balance')
         htlc_id = chan.add_htlc(htlc)
         chan.onion_keys[htlc_id] = secret_key
         self.attempted_route[(chan.channel_id, htlc_id)] = route

electrum/lnchan.py

@@ -143,6 +143,25 @@ class Channel(PrintError):
     def get_state(self):
         return self._state
 
+    def check_can_pay(self, amount_msat):
+        # FIXME what about channel_reserve_satoshis? will the remote fail the channel if we go below? test.
+        # FIXME what about tx fees
+        if self.get_state() != 'OPEN':
+            raise PaymentFailure('Channel not open')
+        if self.balance(LOCAL) < amount_msat:
+            raise PaymentFailure('Not enough local balance')
+        if len(self.htlcs(LOCAL, only_pending=True)) + 1 > self.config[REMOTE].max_accepted_htlcs:
+            raise PaymentFailure('Too many HTLCs already in channel')
+        if htlcsum(self.htlcs(LOCAL, only_pending=True)) + amount_msat > self.config[REMOTE].max_htlc_value_in_flight_msat:
+            raise PaymentFailure('HTLC value sum would exceed max allowed: {} msat'.format(chan.config[REMOTE].max_htlc_value_in_flight_msat))
+
+    def can_pay(self, amount_msat):
+        try:
+            self.check_can_pay(amount_msat)
+        except:
+            return False
+        return True
+
     def set_funding_txo_spentness(self, is_spent: bool):
         assert isinstance(is_spent, bool)
         self._is_funding_txo_spent = is_spent

electrum/lnrouter.py

@@ -519,7 +519,7 @@ class LNPathFinder(PrintError):
 
     @profiler
     def find_path_for_payment(self, from_node_id: bytes, to_node_id: bytes,
-                              amount_msat: int=None) -> Sequence[Tuple[bytes, bytes]]:
+                              amount_msat: int=None, my_channels: dict={}) -> Sequence[Tuple[bytes, bytes]]:
         """Return a path between from_node_id and to_node_id.
 
         Returns a list of (node_id, short_channel_id) representing a path.
@@ -527,6 +527,8 @@ class LNPathFinder(PrintError):
         i.e. an element reads as, "to get to node_id, travel through short_channel_id"
         """
         if amount_msat is not None: assert type(amount_msat) is int
+        unable_channels = set(map(lambda x: x.short_channel_id, filter(lambda x: not x.can_pay(amount_msat), my_channels.values())))
+
         # TODO find multiple paths??
 
         # run Dijkstra
@@ -546,7 +548,8 @@ class LNPathFinder(PrintError):
                 # so there are duplicates in the queue, that we discard now:
                 continue
             for edge_channel_id in self.channel_db.get_channels_for_node(cur_node):
-                if edge_channel_id in self.blacklist: continue
+                if edge_channel_id in self.blacklist or edge_channel_id in unable_channels:
+                    continue
                 channel_info = self.channel_db.get_channel_info(edge_channel_id)
                 node1, node2 = channel_info.node_id_1, channel_info.node_id_2
                 neighbour = node2 if node1 == cur_node else node1

electrum/lnworker.py

@@ -280,7 +280,7 @@ class LNWorker(PrintError):
         for private_route in r_tags:
             if len(private_route) == 0: continue
             border_node_pubkey = private_route[0][0]
-            path = self.network.path_finder.find_path_for_payment(self.node_keypair.pubkey, border_node_pubkey, amount_msat)
+            path = self.network.path_finder.find_path_for_payment(self.node_keypair.pubkey, border_node_pubkey, amount_msat, self.channels)
             if path is None: continue
             route = self.network.path_finder.create_route_from_path(path, self.node_keypair.pubkey)
             # we need to shift the node pubkey by one towards the destination:
@@ -293,7 +293,7 @@ class LNWorker(PrintError):
             break
         # if could not find route using any hint; try without hint now
         if route is None:
-            path = self.network.path_finder.find_path_for_payment(self.node_keypair.pubkey, invoice_pubkey, amount_msat)
+            path = self.network.path_finder.find_path_for_payment(self.node_keypair.pubkey, invoice_pubkey, amount_msat, self.channels)
             if path is None:
                 raise PaymentFailure(_("No path found"))
             route = self.network.path_finder.create_route_from_path(path, self.node_keypair.pubkey)