handle_error_code_from_failed_htlc: omg brainfart :(

follow-up 85841ba20d

electrum/lnworker.py

@@ -7,7 +7,7 @@ import os
 from decimal import Decimal
 import random
 import time
-from typing import Optional, Sequence, Tuple, List, Dict, TYPE_CHECKING, NamedTuple, Union, Mapping
+from typing import Optional, Sequence, Tuple, List, Dict, TYPE_CHECKING, NamedTuple, Union, Mapping, Any
 import threading
 import socket
 import aiohttp
@@ -968,21 +968,10 @@ class LNWallet(LNWorker):
             offset = failure_codes[code]
             channel_update_len = int.from_bytes(data[offset:offset+2], byteorder="big")
             channel_update_as_received = data[offset+2: offset+2+channel_update_len]
-            channel_update_typed = (258).to_bytes(length=2, byteorder="big") + channel_update_as_received
-            # note: some nodes put channel updates in error msgs with the leading msg_type already there.
-            #       we try decoding both ways here.
-            try:
-                message_type, payload = decode_msg(channel_update_typed)
-                if not payload['chain_hash'] != constants.net.rev_genesis_bytes(): raise Exception()
-                payload['raw'] = channel_update_typed
-            except:  # FIXME: too broad
-                try:
-                    message_type, payload = decode_msg(channel_update_as_received)
-                    if not payload['chain_hash'] != constants.net.rev_genesis_bytes(): raise Exception()
-                    payload['raw'] = channel_update_as_received
-                except:
-                    self.logger.info(f'could not decode channel_update for failed htlc: {channel_update_as_received.hex()}')
-                    return True
+            payload = self._decode_channel_update_msg(channel_update_as_received)
+            if payload is None:
+                self.logger.info(f'could not decode channel_update for failed htlc: {channel_update_as_received.hex()}')
+                return True
             r = self.channel_db.add_channel_update(payload)
             blacklist = False
             short_channel_id = ShortChannelID(payload['short_channel_id'])
@@ -1005,6 +994,26 @@ class LNWallet(LNWorker):
             blacklist = True
         return blacklist
 
+    @classmethod
+    def _decode_channel_update_msg(cls, chan_upd_msg: bytes) -> Optional[Dict[str, Any]]:
+        channel_update_as_received = chan_upd_msg
+        channel_update_typed = (258).to_bytes(length=2, byteorder="big") + channel_update_as_received
+        # note: some nodes put channel updates in error msgs with the leading msg_type already there.
+        #       we try decoding both ways here.
+        try:
+            message_type, payload = decode_msg(channel_update_typed)
+            if payload['chain_hash'] != constants.net.rev_genesis_bytes(): raise Exception()
+            payload['raw'] = channel_update_typed
+            return payload
+        except:  # FIXME: too broad
+            try:
+                message_type, payload = decode_msg(channel_update_as_received)
+                if payload['chain_hash'] != constants.net.rev_genesis_bytes(): raise Exception()
+                payload['raw'] = channel_update_as_received
+                return payload
+            except:
+                return None
+
     @staticmethod
     def _check_invoice(invoice: str, *, amount_msat: int = None) -> LnAddr:
         addr = lndecode(invoice, expected_hrp=constants.net.SEGWIT_HRP)

electrum/tests/test_lnutil.py

@@ -11,6 +11,7 @@ from electrum.lnutil import (RevocationStore, get_per_commitment_secret_from_see
                              ScriptHtlc, extract_nodeid, calc_fees_for_commitment_tx, UpdateAddHtlc, LnFeatures)
 from electrum.util import bh2u, bfh, MyEncoder
 from electrum.transaction import Transaction, PartialTransaction
+from electrum.lnworker import LNWallet
 
 from . import ElectrumTestCase
 
@@ -805,3 +806,23 @@ class TestLNUtil(ElectrumTestCase):
                          features.for_invoice())
         features = LnFeatures.BASIC_MPP_OPT | LnFeatures.PAYMENT_SECRET_REQ | LnFeatures.VAR_ONION_REQ
         self.assertEqual(features, features.for_invoice())
+
+    def test_lnworker_decode_channel_update_msg(self):
+        msg_without_prefix = bytes.fromhex("439b71c8ddeff63004e4ff1f9764a57dcf20232b79d9d669aef0e31c42be8e44208f7d868d0133acb334047f30e9399dece226ccd98e5df5330adf7f356290516fe28c0ab6f1b372c1a6a246ae63f74f931e8365e15a089c68d619000000000008762700054a00005ef2cf9c0101009000000000000003e80000000000000001000000002367b880")
+        # good messages
+        self.assertNotEqual(
+            None,
+            LNWallet._decode_channel_update_msg(msg_without_prefix))
+        self.assertNotEqual(
+            None,
+            LNWallet._decode_channel_update_msg(bytes.fromhex("0102") + msg_without_prefix))
+        # bad messages
+        self.assertEqual(
+            None,
+            LNWallet._decode_channel_update_msg(bytes.fromhex("0102030405")))
+        self.assertEqual(
+            None,
+            LNWallet._decode_channel_update_msg(bytes.fromhex("ffff") + msg_without_prefix))
+        self.assertEqual(
+            None,
+            LNWallet._decode_channel_update_msg(bytes.fromhex("0101") + msg_without_prefix))