lnonion: add total_msat to onion payment data

electrum/lnonion.py

@@ -261,7 +261,7 @@ def new_onion_packet(payment_path_pubkeys: Sequence[bytes], session_key: bytes,
         hmac=next_hmac)
 
 
-def calc_hops_data_for_payment(route: 'LNPaymentRoute', amount_msat: int,
+def calc_hops_data_for_payment(route: 'LNPaymentRoute', amount_msat: int, total_msat: int,
                                final_cltv: int, *, payment_secret: bytes = None) \
         -> Tuple[List[OnionHopsDataSingle], int, int]:
     """Returns the hops_data to be used for constructing an onion packet,
@@ -277,8 +277,14 @@ def calc_hops_data_for_payment(route: 'LNPaymentRoute', amount_msat: int,
         "amt_to_forward": {"amt_to_forward": amt},
         "outgoing_cltv_value": {"outgoing_cltv_value": cltv},
     }
+    # for multipart payments we need to tell the reciever about the total and
+    # partial amounts
     if payment_secret is not None:
-        hop_payload["payment_data"] = {"payment_secret": payment_secret, "total_msat": amt}
+        hop_payload["payment_data"] = {
+            "payment_secret": payment_secret,
+            "total_msat": total_msat,
+            "amount_msat": amt
+        }
     hops_data = [OnionHopsDataSingle(is_tlv_payload=route[-1].has_feature_varonion(),
                                      payload=hop_payload)]
     # payloads, backwards from last hop (but excluding the first edge):

electrum/lnpeer.py

@@ -1196,7 +1196,7 @@ class Peer(Logger):
         self.send_message("commitment_signed", channel_id=chan.channel_id, signature=sig_64, num_htlcs=len(htlc_sigs), htlc_signature=b"".join(htlc_sigs))
 
     def pay(self, *, route: 'LNPaymentRoute', chan: Channel, amount_msat: int,
-            payment_hash: bytes, min_final_cltv_expiry: int,
+            total_msat: int, payment_hash: bytes, min_final_cltv_expiry: int,
             payment_secret: bytes = None, fwd_trampoline_onion=None) -> UpdateAddHtlc:
         assert amount_msat > 0, "amount_msat is not greater zero"
         assert len(route) > 0
@@ -1206,8 +1206,13 @@ class Peer(Logger):
         route[0].node_features |= self.features
         local_height = self.network.get_local_height()
         final_cltv = local_height + min_final_cltv_expiry
-        hops_data, amount_msat, cltv = calc_hops_data_for_payment(route, amount_msat, final_cltv,
+        hops_data, amount_msat, cltv = calc_hops_data_for_payment(
-                                                                  payment_secret=payment_secret)
+            route,
+            amount_msat,
+            total_msat,
+            final_cltv,
+            payment_secret=payment_secret
+        )
         self.logger.info(f"lnpeer.pay len(route)={len(route)}")
         for i in range(len(route)):
             self.logger.info(f"  {i}: edge={route[i].short_channel_id} hop_data={hops_data[i]!r}")

electrum/lnworker.py

@@ -1090,7 +1090,7 @@ class LNWallet(LNWorker):
                     routes = [(route, amount_to_send)]
                 # 2. send htlcs
                 for route, amount_msat in routes:
-                    await self.pay_to_route(route, amount_msat, payment_hash, payment_secret, min_cltv_expiry, trampoline_onion)
+                    await self.pay_to_route(route, amount_msat, amount_to_pay, payment_hash, payment_secret, min_cltv_expiry, trampoline_onion)
                     amount_inflight += amount_msat
                 util.trigger_callback('invoice_status', self.wallet, payment_hash.hex())
             # 3. await a queue
@@ -1106,8 +1106,9 @@ class LNWallet(LNWorker):
             # if we get a channel update, we might retry the same route and amount
             self.handle_error_code_from_failed_htlc(htlc_log)
 
-
+    async def pay_to_route(self, route: LNPaymentRoute, amount_msat: int,
-    async def pay_to_route(self, route: LNPaymentRoute, amount_msat:int, payment_hash:bytes, payment_secret:bytes, min_cltv_expiry:int, trampoline_onion:bytes =None):
+                           total_msat: int, payment_hash: bytes, payment_secret: bytes,
+                           min_cltv_expiry: int, trampoline_onion: bytes=None):
         # send a single htlc
         short_channel_id = route[0].short_channel_id
         chan = self.get_channel_by_short_id(short_channel_id)
@@ -1119,6 +1120,7 @@ class LNWallet(LNWorker):
             route=route,
             chan=chan,
             amount_msat=amount_msat,
+            total_msat=total_msat,
             payment_hash=payment_hash,
             min_final_cltv_expiry=min_cltv_expiry,
             payment_secret=payment_secret,

electrum/tests/test_lnpeer.py

@@ -497,6 +497,7 @@ class TestPeer(ElectrumTestCase):
                 route=route1,
                 chan=alice_channel,
                 amount_msat=lnaddr2.get_amount_msat(),
+                total_msat=lnaddr2.get_amount_msat(),
                 payment_hash=lnaddr2.paymenthash,
                 min_final_cltv_expiry=lnaddr2.get_min_final_cltv_expiry(),
                 payment_secret=lnaddr2.payment_secret,
@@ -509,6 +510,7 @@ class TestPeer(ElectrumTestCase):
                 route=route2,
                 chan=bob_channel,
                 amount_msat=lnaddr1.get_amount_msat(),
+                total_msat=lnaddr1.get_amount_msat(),
                 payment_hash=lnaddr1.paymenthash,
                 min_final_cltv_expiry=lnaddr1.get_min_final_cltv_expiry(),
                 payment_secret=lnaddr1.payment_secret,
@@ -663,6 +665,7 @@ class TestPeer(ElectrumTestCase):
             htlc = p1.pay(route=route,
                           chan=alice_channel,
                           amount_msat=lnaddr.get_amount_msat(),
+                          total_msat=lnaddr.get_amount_msat(),
                           payment_hash=lnaddr.paymenthash,
                           min_final_cltv_expiry=lnaddr.get_min_final_cltv_expiry(),
                           payment_secret=lnaddr.payment_secret)
@@ -771,7 +774,7 @@ class TestPeer(ElectrumTestCase):
             min_cltv_expiry = lnaddr.get_min_final_cltv_expiry()
             payment_hash = lnaddr.paymenthash
             payment_secret = lnaddr.payment_secret
-            pay = w1.pay_to_route(route, amount_msat, payment_hash, payment_secret, min_cltv_expiry)
+            pay = w1.pay_to_route(route, amount_msat, amount_msat, payment_hash, payment_secret, min_cltv_expiry)
             await asyncio.gather(pay, p1._message_loop(), p2._message_loop(), p1.htlc_switch(), p2.htlc_switch())
         with self.assertRaises(PaymentFailure):
             run(f())