plugins/fetchinvoice: allow use of expired offers *for recurrence*.

We added this to the recurrence spec: the offer expiration only applies to the
first request, not subsequent ones.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Author: rustyrussell

plugins/fetchinvoice.c

@@ -863,9 +863,16 @@ struct command_result *json_fetchinvoice(struct command *cmd,
 	 *   - if the current time is after `offer_absolute_expiry`:
 	 *     - MUST NOT respond to the offer.
 	 */
+	/* BOLT-recurrence #12:
+	 *   - if the current time is after `offer_absolute_expiry`:
+	 *      - MUST NOT make an initial response to the offer
+	 *        (i.e. continuing an existing offer with recurrence is ok)
+	 */
 	if (sent->offer->offer_absolute_expiry
-	    && time_now().ts.tv_sec > *sent->offer->offer_absolute_expiry)
+	    && time_now().ts.tv_sec > *sent->offer->offer_absolute_expiry
+	    && (!recurrence_counter || *recurrence_counter == 0)) {
 		return command_fail(cmd, OFFER_EXPIRED, "Offer expired");
+	}
 
 	/* BOLT #12:
 	 * The writer:

plugins/offers_invreq_hook.c

@@ -848,9 +848,16 @@ static struct command_result *listoffers_done(struct command *cmd,
 					json_tok_full(buf, offertok));
 	}
 
+	/* BOLT-recurrence #12:
+	 * - if `offer_absolute_expiry` is present, and
+	 *   `invreq_recurrence_counter` is either not present or equal to 0:
+	 *    - MUST reject the invoice request if the current time is after
+	 *      `offer_absolute_expiry`.
+	 */
 	if (ir->invreq->offer_absolute_expiry
+	    && (!ir->invreq->invreq_recurrence_counter
+		|| *ir->invreq->invreq_recurrence_counter == 0)
 	    && time_now().ts.tv_sec >= *ir->invreq->offer_absolute_expiry) {
-		/* FIXME: do deloffer to disable it */
 		return fail_invreq(cmd, ir, "Offer expired");
 	}
 

tests/test_pay.py

@@ -4725,6 +4725,26 @@ def test_fetchinvoice_recurrence(node_factory, bitcoind):
                                      'recurrence_label': 'test paywindow'})
 
 
+def test_recurrence_expired_offer(node_factory, bitcoind):
+    """We *can* use an expired offer for successive recurrences"""
+    l1, l2 = node_factory.line_graph(2)
+
+    offer = l2.rpc.offer(amount='1msat',
+                         description='paywindow test',
+                         recurrence='20seconds',
+                         absolute_expiry=int(time.time()) + 15)
+    ret = l1.rpc.fetchinvoice(offer=offer['bolt12'],
+                              recurrence_counter=0,
+                              recurrence_label='test_recurrence_expired_offer')
+    l1.rpc.pay(ret['invoice'], label='test_recurrence_expired_offer')
+
+    time.sleep(16)
+    ret = l1.rpc.fetchinvoice(offer=offer['bolt12'],
+                              recurrence_counter=1,
+                              recurrence_label='test_recurrence_expired_offer')
+    l1.rpc.pay(ret['invoice'], label='test_recurrence_expired_offer')
+
+
 def test_fetchinvoice_autoconnect(node_factory, bitcoind):
     """We should autoconnect if we need to, to route."""