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lnpeer: reestablish_channel - replay un-acked local updates

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Replay un-acked local updates (including commitment_signed) byte-for-byte.
If we have sent them a commitment signature that they "lost" (due to disconnect),
we need to make sure we replay the same local updates, as otherwise they could
end up with two (or more) signed valid commitment transactions at the same ctn.
Multiple valid ctxs at the same ctn is a major headache for pre-signing spending txns,
e.g. for watchtowers, hence we must ensure these ctxs coincide.
This commit is contained in:
SomberNight
2019-08-02 17:55:45 +02:00
committed by ThomasV
parent e81ae1921b
commit 014b921393
2 changed files with 40 additions and 6 deletions
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32
electrum/lnpeer.py
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@@ -93,7 +93,19 @@ class Peer(Logger):
def send_message(self, message_name: str, **kwargs):
assert type(message_name) is str
self.logger.debug(f"Sending {message_name.upper()}")
self.transport.send_bytes(encode_msg(message_name, **kwargs))
raw_msg = encode_msg(message_name, **kwargs)
self._store_raw_msg_if_local_update(raw_msg, message_name=message_name, channel_id=kwargs.get("channel_id"))
self.transport.send_bytes(raw_msg)
def _store_raw_msg_if_local_update(self, raw_msg: bytes, *, message_name: str, channel_id: Optional[bytes]):
if not (message_name.startswith("update_") or message_name == "commitment_signed"):
return
assert channel_id
chan = self.lnworker.channels[channel_id] # type: Channel
chan.hm.store_local_update_raw_msg(raw_msg)
if message_name == "commitment_signed":
# saving now, to ensure replaying updates works (in case of channel reestablishment)
self.lnworker.save_channel(chan)
async def initialize(self):
if isinstance(self.transport, LNTransport):
@@ -733,11 +745,21 @@ class Peer(Logger):
should_close_they_are_ahead = False
# compare remote ctns
if next_remote_ctn != their_next_local_ctn:
self.logger.warning(f"channel_reestablish: expected remote ctn {next_remote_ctn}, got {their_next_local_ctn}")
if their_next_local_ctn < next_remote_ctn:
should_close_we_are_ahead = True
if their_next_local_ctn == latest_remote_ctn and chan.hm.is_revack_pending(REMOTE):
# Replay un-acked local updates (including commitment_signed) byte-for-byte.
# If we have sent them a commitment signature that they "lost" (due to disconnect),
# we need to make sure we replay the same local updates, as otherwise they could
# end up with two (or more) signed valid commitment transactions at the same ctn.
# Multiple valid ctxs at the same ctn is a major headache for pre-signing spending txns,
# e.g. for watchtowers, hence we must ensure these ctxs coincide.
for raw_upd_msg in chan.hm.get_unacked_local_updates():
self.transport.send_bytes(raw_upd_msg)
else:
should_close_they_are_ahead = True
self.logger.warning(f"channel_reestablish: expected remote ctn {next_remote_ctn}, got {their_next_local_ctn}")
if their_next_local_ctn < next_remote_ctn:
should_close_we_are_ahead = True
else:
should_close_they_are_ahead = True
# compare local ctns
if oldest_unrevoked_local_ctn != their_oldest_unrevoked_remote_ctn:
if oldest_unrevoked_local_ctn - 1 == their_oldest_unrevoked_remote_ctn: