commit 014b92139353145b67dff467fb4bb4743a9688b0
parent e81ae1921b84fa7ce67e5e8dded92575bdbe5501
Author: SomberNight <somber.night@protonmail.com>
Date: Fri, 2 Aug 2019 17:55:45 +0200
lnpeer: reestablish_channel - replay un-acked local updates
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.
Diffstat:
2 files changed, 40 insertions(+), 6 deletions(-)
diff --git a/electrum/lnhtlc.py b/electrum/lnhtlc.py
@@ -2,7 +2,7 @@ from copy import deepcopy
from typing import Optional, Sequence, Tuple, List
from .lnutil import SENT, RECEIVED, LOCAL, REMOTE, HTLCOwner, UpdateAddHtlc, Direction, FeeUpdate
-from .util import bh2u
+from .util import bh2u, bfh
class HTLCManager:
@@ -34,6 +34,9 @@ class HTLCManager:
log[sub]['fails'] = {int(htlc_id): coerceHtlcOwner2IntMap(ctns) for htlc_id, ctns in log[sub]['fails'].items()}
# "side who initiated fee update" -> action -> list of FeeUpdates
log[sub]['fee_updates'] = [FeeUpdate.from_dict(fee_upd) for fee_upd in log[sub]['fee_updates']]
+ if 'unacked_local_updates' not in log:
+ log['unacked_local_updates'] = []
+ log['unacked_local_updates'] = [bfh(upd) for upd in log['unacked_local_updates']]
# maybe bootstrap fee_updates if initial_feerate was provided
if initial_feerate is not None:
assert type(initial_feerate) is int
@@ -68,6 +71,7 @@ class HTLCManager:
log[sub]['adds'] = d
# fee_updates
log[sub]['fee_updates'] = [FeeUpdate.to_dict(fee_upd) for fee_upd in log[sub]['fee_updates']]
+ log['unacked_local_updates'] = [bh2u(upd) for upd in log['unacked_local_updates']]
return log
##### Actions on channel:
@@ -166,6 +170,8 @@ class HTLCManager:
for fee_update in self.log[LOCAL]['fee_updates']:
if fee_update.ctns[LOCAL] is None and fee_update.ctns[REMOTE] <= self.ctn_latest(REMOTE):
fee_update.ctns[LOCAL] = self.ctn_latest(LOCAL) + 1
+ # no need to keep local update raw msgs anymore, they have just been ACKed.
+ self.log['unacked_local_updates'].clear()
def discard_unsigned_remote_updates(self):
"""Discard updates sent by the remote, that the remote itself
@@ -186,6 +192,12 @@ class HTLCManager:
if fee_update.ctns[LOCAL] > self.ctn_latest(LOCAL):
del self.log[REMOTE]['fee_updates'][i]
+ def store_local_update_raw_msg(self, raw_update_msg: bytes):
+ self.log['unacked_local_updates'].append(raw_update_msg)
+
+ def get_unacked_local_updates(self) -> Sequence[bytes]:
+ return self.log['unacked_local_updates']
+
##### Queries re HTLCs:
def htlcs_by_direction(self, subject: HTLCOwner, direction: Direction,
diff --git a/electrum/lnpeer.py b/electrum/lnpeer.py
@@ -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:
