lnpeer.pay: also log hops_data for trampoline_onion

We were already logging the outer-layer hops_data,
now we also log the inner trampoline-onion hops_data.

Example:
```
  1.12 | I | P/lnpeer.Peer.[MockLNWallet, alice->bob] | lnpeer.pay len(route)=1
  1.12 | I | P/lnpeer.Peer.[MockLNWallet, alice->bob] |   0: edge=9926297x9781928x61754 hop_data=<OnionHopsDataSingle. payload={'amt_to_forward': {'amt_to_forward': 100000000}, 'outgoing_cltv_value': {'outgoing_cltv_value': 601299}, 'payment_data': {'payment_secret': b'\xd2\x9cl\xdfV\xd4\xea_\x06{\xed\xc9\xc7\xa6\xf5\xc0\n\x1a\x95\xad\xad\xd2F\xb8;&\x9f\xa1\xe1\xd1\x07H', 'total_msat': 100000000, 'amount_msat': 100000000}}. hmac=None>
  1.12 | I | P/lnpeer.Peer.[MockLNWallet, alice->bob] | adding trampoline onion to final payload
  1.12 | I | P/lnpeer.Peer.[MockLNWallet, alice->bob] | lnpeer.pay len(t_route)=3
  1.12 | I | P/lnpeer.Peer.[MockLNWallet, alice->bob] |   0: t_node=02389c93b85ef8f7264c6fa3d3b239341c2631c2cab97e815b33453bd8d0254e77 hop_data=<OnionHopsDataSingle. payload={'amt_to_forward': {'amt_to_forward': 100000000}, 'outgoing_cltv_value': {'outgoing_cltv_value': 600723}, 'outgoing_node_id': {'outgoing_node_id': b'\x03\x06\xd9,\x9c\xabRe\x83Mr\x0b\x14(\xf5\x81\xf9\xfb\x9b\xfeV\xc1q\x85&L\xda\xffs\xe5y(\x81'}}. hmac=b'\xe7\x04\xe2>\x9a\xd9\xf0\x92<\xf8Q\xe4\xf4\xd8\x8cr{\x1e\xb1\xee\xb0\xd4R\xba\xe5\xfd\x83\xfc\xd7\xa7\x1dt'>
  1.12 | I | P/lnpeer.Peer.[MockLNWallet, alice->bob] |   1: t_node=0306d92c9cab5265834d720b1428f581f9fb9bfe56c17185264cdaff73e5792881 hop_data=<OnionHopsDataSingle. payload={'amt_to_forward': {'amt_to_forward': 100000000}, 'outgoing_cltv_value': {'outgoing_cltv_value': 600147}, 'outgoing_node_id': {'outgoing_node_id': b'\x03\x85v\xac:\xf8AUW\xcf\x1d\x12e\xcc\xff\xb1\xea\xd6\x01\xd5\x17HX?\x12\x83\x9cD\xbe\xebC\x82o'}}. hmac=b's-\xe1\xdb\xbc\xa5\x88\x90\xc0\xafu\xab\xba\xb6k\x81\xeae)#\x85\x12fm\xe6\xc3\xbd\xf6\x86eR\xd2'>
  1.12 | I | P/lnpeer.Peer.[MockLNWallet, alice->bob] |   2: t_node=038576ac3af8415557cf1d1265ccffb1ead601d51748583f12839c44beeb43826f hop_data=<OnionHopsDataSingle. payload={'amt_to_forward': {'amt_to_forward': 100000000}, 'outgoing_cltv_value': {'outgoing_cltv_value': 600147}, 'payment_data': {'payment_secret': b'B-P\x01\xc3\x1e#\x19\xf9!\xbb\xd8\xd1pu\xc7J\x11A\xa8J\xfe\xb8\x8a\xb8\xc4Oi\x0f\xe8\xac\xab', 'total_msat': 100000000}}. hmac=b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'>
  1.12 | I | P/lnpeer.Peer.[MockLNWallet, alice->bob] | starting payment. len(route)=1.
```

electrum/lnonion.py

@@ -117,6 +117,9 @@ class OnionPacket:
         self.hmac = hmac
         if not ecc.ECPubkey.is_pubkey_bytes(public_key):
             raise InvalidOnionPubkey()
+        # for debugging our own onions:
+        self._debug_hops_data = None  # type: Optional[Sequence[OnionHopsDataSingle]]
+        self._debug_route = None      # type: Optional[LNPaymentRoute]
 
     def to_bytes(self) -> bytes:
         ret = bytes([self.version])

electrum/lnpeer.py

@@ -1478,7 +1478,7 @@ class Peer(Logger):
             payment_hash: bytes,
             min_final_cltv_expiry: int,
             payment_secret: bytes,
-            trampoline_onion=None,
+            trampoline_onion: Optional[OnionPacket] = None,
     ):
         # add features learned during "init" for direct neighbour:
         route[0].node_features |= self.features
@@ -1506,6 +1506,12 @@ class Peer(Logger):
                 "hops_data": trampoline_onion.hops_data,
                 "hmac": trampoline_onion.hmac
             }
+            if t_hops_data := trampoline_onion._debug_hops_data:  # None if trampoline-forwarding
+                t_route = trampoline_onion._debug_route
+                assert t_route is not None
+                self.logger.info(f"lnpeer.pay len(t_route)={len(t_route)}")
+                for i in range(len(t_route)):
+                    self.logger.info(f"  {i}: t_node={t_route[i].end_node.hex()} hop_data={t_hops_data[i]!r}")
         # create onion packet
         payment_path_pubkeys = [x.node_id for x in route]
         onion = new_onion_packet(payment_path_pubkeys, session_key, hops_data, associated_data=payment_hash) # must use another sessionkey
@@ -1540,7 +1546,7 @@ class Peer(Logger):
             payment_hash: bytes,
             min_final_cltv_expiry: int,
             payment_secret: bytes,
-            trampoline_onion=None,
+            trampoline_onion: Optional[OnionPacket] = None,
         ) -> UpdateAddHtlc:
 
         assert amount_msat > 0, "amount_msat is not greater zero"

electrum/lnworker.py

@@ -1560,7 +1560,7 @@ class LNWallet(LNWorker):
             paysession: PaySession,
             sent_htlc_info: SentHtlcInfo,
             min_cltv_expiry: int,
-            trampoline_onion: bytes = None,
+            trampoline_onion: Optional[OnionPacket] = None,
     ) -> None:
         """Sends a single HTLC."""
         shi = sent_htlc_info

electrum/trampoline.py

@@ -9,6 +9,10 @@ from .lnonion import calc_hops_data_for_payment, new_onion_packet
 from .lnrouter import RouteEdge, TrampolineEdge, LNPaymentRoute, is_route_sane_to_use
 from .lnutil import NoPathFound, LNPeerAddr
 from . import constants
+from .logging import get_logger
+
+
+_logger = get_logger(__name__)
 
 # trampoline nodes are supposed to advertise their fee and cltv in node_update message
 TRAMPOLINE_FEES = [
@@ -307,6 +311,8 @@ def create_trampoline_onion(
             }
     trampoline_session_key = os.urandom(32)
     trampoline_onion = new_onion_packet(payment_path_pubkeys, trampoline_session_key, hops_data, associated_data=payment_hash, trampoline=True)
+    trampoline_onion._debug_hops_data = hops_data
+    trampoline_onion._debug_route = route
     return trampoline_onion, amount_msat, cltv