MPP receive: allow payer to retry after mpp timeout

electrum/lnpeer.py

@@ -1576,10 +1576,10 @@ class Peer(Logger):
         invoice_msat = info.amount_msat
         if not (invoice_msat is None or invoice_msat <= total_msat <= 2 * invoice_msat):
             raise exc_incorrect_or_unknown_pd
-        accepted, expired = self.lnworker.htlc_received(chan.short_channel_id, htlc, total_msat)
-        if accepted:
+        mpp_status = self.lnworker.add_received_htlc(chan.short_channel_id, htlc, total_msat)
+        if mpp_status == True:
             return preimage
-        elif expired:
+        elif mpp_status == False:
             raise OnionRoutingFailure(code=OnionFailureCode.MPP_TIMEOUT, data=b'')
         else:
             return None

electrum/lnworker.py

@@ -657,7 +657,7 @@ class LNWallet(LNWorker):
             self._channels[bfh(channel_id)] = Channel(c, sweep_address=self.sweep_address, lnworker=self)
 
         self.sent_htlcs = defaultdict(asyncio.Queue)  # type: Dict[bytes, asyncio.Queue[HtlcLog]]
-        self.received_htlcs = defaultdict(set) # type: Dict[bytes, set]
+        self.received_htlcs = dict()                  # RHASH -> mpp_status, htlc_set
         self.htlc_routes = dict()
 
         self.swap_manager = SwapManager(wallet=self.wallet, lnworker=self)
@@ -1682,24 +1682,30 @@ class LNWallet(LNWorker):
             self.payments[key] = info.amount_msat, info.direction, info.status
         self.wallet.save_db()
 
-    def htlc_received(self, short_channel_id, htlc: UpdateAddHtlc, expected_msat: int):
-        status = self.get_payment_status(htlc.payment_hash)
-        if status == PR_PAID:
-            return True, None
-        s = self.received_htlcs[htlc.payment_hash]
-        if (short_channel_id, htlc) not in s:
-            s.add((short_channel_id, htlc))
-        total = sum([htlc.amount_msat for scid, htlc in s])
-        first_timestamp = min([htlc.timestamp for scid, htlc in s])
-        expired = time.time() - first_timestamp > MPP_EXPIRY
-        if total == expected_msat and not expired:
-            # status must be persisted
-            self.set_payment_status(htlc.payment_hash, PR_PAID)
-            util.trigger_callback('request_status', self.wallet, htlc.payment_hash.hex(), PR_PAID)
-            return True, None
-        if expired:
-            return None, True
-        return None, None
+    def add_received_htlc(self, short_channel_id, htlc: UpdateAddHtlc, expected_msat: int) -> Optional[bool]:
+        """ return MPP status: True (accepted), False (expired) or None """
+        payment_hash = htlc.payment_hash
+        mpp_status, htlc_set = self.received_htlcs.get(payment_hash, (None, set()))
+        key = (short_channel_id, htlc)
+        if key not in htlc_set:
+            htlc_set.add(key)
+        if mpp_status is None:
+            total = sum([_htlc.amount_msat for scid, _htlc in htlc_set])
+            first_timestamp = min([_htlc.timestamp for scid, _htlc in htlc_set])
+            expired = time.time() - first_timestamp > MPP_EXPIRY
+            if expired:
+                mpp_status = False
+            elif total == expected_msat:
+                mpp_status = True
+                self.set_payment_status(payment_hash, PR_PAID)
+                util.trigger_callback('request_status', self.wallet, payment_hash.hex(), PR_PAID)
+        if mpp_status is not None:
+            htlc_set.remove(key)
+        if len(htlc_set) > 0:
+            self.received_htlcs[payment_hash] = mpp_status, htlc_set
+        elif payment_hash in self.received_htlcs:
+            self.received_htlcs.pop(payment_hash)
+        return mpp_status
 
     def get_payment_status(self, payment_hash):
         info = self.get_payment_info(payment_hash)

electrum/tests/test_lnpeer.py

@@ -132,7 +132,7 @@ class MockLNWallet(Logger, NetworkRetryManager[LNPeerAddr]):
         # used in tests
         self.enable_htlc_settle = asyncio.Event()
         self.enable_htlc_settle.set()
-        self.received_htlcs = defaultdict(set)
+        self.received_htlcs = dict()
         self.sent_htlcs = defaultdict(asyncio.Queue)
         self.htlc_routes = defaultdict(list)
 
@@ -170,7 +170,7 @@ class MockLNWallet(Logger, NetworkRetryManager[LNPeerAddr]):
     set_invoice_status = LNWallet.set_invoice_status
     set_payment_status = LNWallet.set_payment_status
     get_payment_status = LNWallet.get_payment_status
-    htlc_received = LNWallet.htlc_received
+    add_received_htlc = LNWallet.add_received_htlc
     htlc_fulfilled = LNWallet.htlc_fulfilled
     htlc_failed = LNWallet.htlc_failed
     save_preimage = LNWallet.save_preimage