From b8d989e13b6c4c1e9dec3d795f511f32e21321ff Mon Sep 17 00:00:00 2001
From: SomberNight <somber.night@protonmail.com>
Date: Tue, 19 Aug 2025 14:49:38 +0000
Subject: [PATCH] lnpeer: rate-limit reply_channel_range

---
 electrum/lnpeer.py | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/electrum/lnpeer.py b/electrum/lnpeer.py
index 216bdd895..1b10d2c40 100644
--- a/electrum/lnpeer.py
+++ b/electrum/lnpeer.py
@@ -106,7 +106,7 @@ class Peer(Logger, EventListener):
         assert self.node_ids[0] != self.node_ids[1]
         self.last_message_time = 0
         self.pong_event = asyncio.Event()
-        self.reply_channel_range = asyncio.Queue()
+        self.reply_channel_range = None  # type: Optional[asyncio.Queue]
         # gossip uses a single queue to preserve message order
         self.recv_gossip_queue = asyncio.Queue(maxsize=self.RECV_GOSSIP_QUEUE_HARD_MAXSIZE)
         self.our_gossip_timestamp_filter = None  # type: Optional[GossipTimestampFilter]
@@ -709,6 +709,7 @@ class Peer(Logger, EventListener):
             self.outgoing_gossip_reply = False
 
     async def get_channel_range(self):
+        self.reply_channel_range = asyncio.Queue()
         first_block = constants.net.BLOCK_HEIGHT_FIRST_LIGHTNING_CHANNELS
         num_blocks = self.lnworker.network.get_local_height() - first_block
         self.query_channel_range(first_block, num_blocks)
@@ -747,6 +748,7 @@ class Peer(Logger, EventListener):
                 a, b = intervals[0]
                 if a <= first_block and b >= first_block + num_blocks:
                     break
+        self.reply_channel_range = None
         return ids, complete
 
     def request_gossip(self, timestamp=0):
@@ -784,7 +786,7 @@ class Peer(Logger, EventListener):
         ids = [decoded[i:i+8] for i in range(0, len(decoded), 8)]
         return ids
 
-    def on_reply_channel_range(self, payload):
+    async def on_reply_channel_range(self, payload):
         first = payload['first_blocknum']
         num = payload['number_of_blocks']
         complete = bool(int.from_bytes(payload['sync_complete'], 'big'))
@@ -792,6 +794,12 @@ class Peer(Logger, EventListener):
         ids = self.decode_short_ids(encoded)
         # self.logger.info(f"on_reply_channel_range. >>> first_block {first}, num_blocks {num}, "
         #                  f"num_ids {len(ids)}, complete {complete}")
+        if self.reply_channel_range is None:
+            raise Exception("received 'reply_channel_range' without corresponding 'query_channel_range'")
+        while self.reply_channel_range.qsize() > 10:
+            # we block process_message until the queue gets consumed
+            self.logger.info("reply_channel_range queue is overflowing. sleeping...")
+            await asyncio.sleep(0.1)
         self.reply_channel_range.put_nowait((first, num, complete, ids))
 
     async def _send_reply_short_channel_ids(self, payload: dict):