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channeld: fail channel on zero next_commitment_number #9435

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channeld: fail channel on zero next_commitment_number #9435

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07b6f3f
tests: reproduce zero next_commitment_number on advanced channel
vincenzopalazzo Aug 18, 2026
bb2efbc
channeld: fail channel on zero next_commitment_number
vincenzopalazzo Aug 18, 2026
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13 changes: 5 additions & 8 deletions channeld/channeld.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5990,6 +5990,11 @@ static void peer_reconnect(struct peer *peer,
* - MUST NOT retransmit `channel_ready`, but MAY send `channel_ready` with
* a different `short_channel_id` `alias` field.
*/
if (next_commitment_number == 0)
peer_failed_err(peer->pps,
&peer->channel_id,
"bad reestablish commitment_number: %"PRIu64,
next_commitment_number);

if (peer->channel_ready[LOCAL]
&& peer->next_index[LOCAL] == 1
Expand Down Expand Up @@ -6102,14 +6107,6 @@ static void peer_reconnect(struct peer *peer,
* `commitment_signed`.
*/
if (next_commitment_number == peer->next_index[REMOTE] - 1) {
/* We completed opening, we don't re-transmit that one! */
if (next_commitment_number == 0)
peer_failed_err(peer->pps,
&peer->channel_id,
"bad reestablish commitment_number: %"
PRIu64,
next_commitment_number);

if (!recv_tlvs || !recv_tlvs->next_funding)
retransmit_commitment_signed = true;
else
Expand Down
42 changes: 42 additions & 0 deletions tests/test_connection.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3050,6 +3050,48 @@ def test_opener_simple_reconnect(node_factory, bitcoind):
l1.pay(l2, 200000000)


def test_reestablish_zero_commitment_number(node_factory, bitcoind):
"""BOLT #2: next_commitment_number 0 must fail the channel."""
l2priv = '12' * 32
l1, l2 = node_factory.get_nodes(2, opts=[{'may_reconnect': True},
{'dev-force-privkey': l2priv}])
l1.rpc.connect(l2.info['id'], 'localhost', l2.port)
l1.fundchannel(l2, 10**6)

# Advance so next_index[REMOTE] > 1; otherwise 0 is the
# "we completed opening" case already handled in-tree.
l1.pay(l2, 10**8)

channel_id = first_channel_id(l1, l2)
l2_id = l2.info['id']
l2.stop()
wait_for(lambda: l1.rpc.getpeer(l2_id)['connected'] is False)

lc = wire.connect(wire.PrivateKey(bytes.fromhex(l2priv)),
wire.PublicKey(bytes.fromhex(l1.info['id'])),
'127.0.0.1', l1.port)
init = lc.read_message()
assert int.from_bytes(init[:2], 'big') == 16
lc.send_message(init)

while True:
msg = lc.read_message()
if int.from_bytes(msg[:2], 'big') == 136:
break

# channel_reestablish: both numbers 0, dummy secret and point.
lc.send_message(bytes.fromhex('0088')
+ bytes.fromhex(channel_id)
+ (0).to_bytes(8, 'big')
+ (0).to_bytes(8, 'big')
+ bytes(32)
+ bytes.fromhex(l2_id))

l1.daemon.wait_for_log('bad reestablish commitment_number: 0')
l1.daemon.wait_for_log('State changed from CHANNELD_NORMAL to AWAITING_UNILATERAL')
l1.wait_for_channel_onchain(l2_id)


@unittest.skipIf(os.getenv('TEST_DB_PROVIDER', 'sqlite3') != 'sqlite3', "sqlite3-specific DB rollback")
@pytest.mark.openchannel('v1')
@pytest.mark.openchannel('v2')
Expand Down
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