pass blacklist to lnrouter.find_route, so that lnrouter is stateless (see #6778)

electrum/lnutil.py

@@ -8,7 +8,7 @@ import json
 from collections import namedtuple, defaultdict
 from typing import NamedTuple, List, Tuple, Mapping, Optional, TYPE_CHECKING, Union, Dict, Set, Sequence
 import re
-
+import time
 import attr
 from aiorpcx import NetAddress
 
@@ -1313,3 +1313,17 @@ class OnionFailureCodeMetaFlag(IntFlag):
     NODE     = 0x2000
     UPDATE   = 0x1000
 
+
+class ChannelBlackList:
+
+    def __init__(self):
+        self.blacklist = dict() # short_chan_id -> timestamp
+
+    def add(self, short_channel_id: ShortChannelID):
+        now = int(time.time())
+        self.blacklist[short_channel_id] = now
+
+    def get_current_list(self) -> Set[ShortChannelID]:
+        BLACKLIST_DURATION = 3600
+        now = int(time.time())
+        return set(k for k, t in self.blacklist.items() if now - t < BLACKLIST_DURATION)