lightningd: cancel watching original funding when we switch to the new one via splice.

This happens if the channel is *not* announcable yet.  Then we hit the assertion
in funding_depth_cb that the txid is the same as the current funding.txid.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-EXPERIMENTAL: fixed crash when we splice a channel which hasn't been announced yet.

Author: rustyrussell

lightningd/channel_control.c

@@ -1125,14 +1125,17 @@ static void handle_peer_splice_locked(struct channel *channel, const u8 *msg)
 	wallet_htlcsigs_confirm_inflight(channel->peer->ld->wallet, channel,
 					 &inflight->funding->outpoint);
 
-	update_channel_from_inflight(channel->peer->ld, channel, inflight, true);
+	/* Stop watching previous funding tx (could be, for announcement) */
+	channel_unwatch_funding(channel->peer->ld, channel);
 
 	/* Stash prev funding data so we can log it after scid is updated
 	 * (to get the blockheight) */
 	prev_our_msats = channel->our_msat;
 	prev_funding_sats = channel->funding_sats;
 	prev_funding_out = channel->funding;
 
+	update_channel_from_inflight(channel->peer->ld, channel, inflight, true);
+
 	channel->our_msat.millisatoshis += splice_amnt * 1000; /* Raw: splicing */
 	channel->msat_to_us_min.millisatoshis += splice_amnt * 1000; /* Raw: splicing */
 	channel->msat_to_us_max.millisatoshis += splice_amnt * 1000; /* Raw: splicing */

lightningd/peer_control.c

@@ -2347,6 +2347,14 @@ void channel_watch_wrong_funding(struct lightningd *ld, struct channel *channel)
 	}
 }
 
+/* We need to do this before we change channel funding (for splice), otherwise
+ * funding_depth_cb will fail the assertion that it's the current funding tx */
+void channel_unwatch_funding(struct lightningd *ld, struct channel *channel)
+{
+	tal_free(find_txwatch(ld->topology,
+			      &channel->funding.txid, funding_depth_cb, channel));
+}
+
 void channel_watch_funding(struct lightningd *ld, struct channel *channel)
 {
 	log_debug(channel->log, "Watching for funding txid: %s",

lightningd/peer_control.h

@@ -131,6 +131,7 @@ void update_channel_from_inflight(struct lightningd *ld,
 				  const struct channel_inflight *inflight,
 				  bool is_splice);
 
+void channel_unwatch_funding(struct lightningd *ld, struct channel *channel);
 void channel_watch_funding(struct lightningd *ld, struct channel *channel);
 
 /* If this channel has a "wrong funding" shutdown, watch that too. */

lightningd/test/run-invoice-select-inchan.c

@@ -244,6 +244,16 @@ struct channel *find_channel_by_id(const struct peer *peer UNNEEDED,
 struct plugin *find_plugin_for_command(struct lightningd *ld UNNEEDED,
 				       const char *cmd_name UNNEEDED)
 { fprintf(stderr, "find_plugin_for_command called!\n"); abort(); }
+/* Generated stub for find_txwatch_ */
+struct txwatch *find_txwatch_(struct chain_topology *topo UNNEEDED,
+			      const struct bitcoin_txid *txid UNNEEDED,
+			      enum watch_result (*cb)(struct lightningd *ld UNNEEDED,
+						      const struct bitcoin_txid * UNNEEDED,
+						      const struct bitcoin_tx * UNNEEDED,
+						      unsigned int depth UNNEEDED,
+						      void *arg) UNNEEDED,
+			    void *arg UNNEEDED)
+{ fprintf(stderr, "find_txwatch_ called!\n"); abort(); }
 /* Generated stub for fixup_htlcs_out */
 void fixup_htlcs_out(struct lightningd *ld UNNEEDED)
 { fprintf(stderr, "fixup_htlcs_out called!\n"); abort(); }

tests/test_splicing.py

@@ -558,8 +558,9 @@ def test_route_by_old_scid(node_factory, bitcoind):
     l1.rpc.waitsendpay(inv2['payment_hash'])
 
 
-@pytest.mark.xfail(strict=True)
 @unittest.skipIf(TEST_NETWORK != 'regtest', 'elementsd doesnt yet support PSBT features we need')
+@pytest.mark.openchannel('v1')
+@pytest.mark.openchannel('v2')
 def test_splice_unannounced(node_factory, bitcoind):
     l1, l2 = node_factory.line_graph(2, fundamount=1000000, wait_for_announce=False, opts={'experimental-splicing': None})
 

wallet/test/run-wallet.c

@@ -243,6 +243,16 @@ void   fatal(const char *fmt UNNEEDED, ...)
 /* Generated stub for fatal_vfmt */
 void  fatal_vfmt(const char *fmt UNNEEDED, va_list ap UNNEEDED)
 { fprintf(stderr, "fatal_vfmt called!\n"); abort(); }
+/* Generated stub for find_txwatch_ */
+struct txwatch *find_txwatch_(struct chain_topology *topo UNNEEDED,
+			      const struct bitcoin_txid *txid UNNEEDED,
+			      enum watch_result (*cb)(struct lightningd *ld UNNEEDED,
+						      const struct bitcoin_txid * UNNEEDED,
+						      const struct bitcoin_tx * UNNEEDED,
+						      unsigned int depth UNNEEDED,
+						      void *arg) UNNEEDED,
+			    void *arg UNNEEDED)
+{ fprintf(stderr, "find_txwatch_ called!\n"); abort(); }
 /* Generated stub for force_peer_disconnect */
 void force_peer_disconnect(struct lightningd *ld UNNEEDED,
 			   const struct peer *peer UNNEEDED,