gossipd: don't "unmark" dying channels' updates if we receive them.

This looked like a test flake, but was real:

```
        l1.daemon.wait_for_log("closing soon due to the funding outpoint being spent")
    
        # We won't gossip the dead channel any more (but we still propagate node_announcement).  But connectd is not explicitly synced, so wait for "a bit".
        time.sleep(1)
>       assert len(get_gossip(l1)) == 2
E       assert 4 == 2
```

We can see that two channel_updates come in *after* we mark it dying:

```
gossipd: channel 103x1x0 closing soon due to the funding outpoint being spent
gossipd: REPLY WIRE_GOSSIPD_NEW_BLOCKHEIGHT_REPLY with 0 fds
022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59-gossipd: Received channel_update for channel 103x1x0/0 now DISABLED
022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59-gossipd: Received channel_update for channel 103x1x0/1 now DISABLED
```

We should keep marking channel_updates the same way.

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

gossipd/gossip_store.c

@@ -70,7 +70,7 @@ static ssize_t gossip_pwritev(int fd, const struct iovec *iov, int iovcnt,
 #endif /* !HAVE_PWRITEV */
 
 static bool append_msg(int fd, const u8 *msg, u32 timestamp,
-		       bool zombie, bool spam, u64 *len)
+		       bool zombie, bool spam, bool dying, u64 *len)
 {
 	struct gossip_hdr hdr;
 	u32 msglen;
@@ -86,6 +86,8 @@ static bool append_msg(int fd, const u8 *msg, u32 timestamp,
 		hdr.flags |= CPU_TO_BE16(GOSSIP_STORE_RATELIMIT_BIT);
 	if (zombie)
 		hdr.flags |= CPU_TO_BE16(GOSSIP_STORE_ZOMBIE_BIT);
+	if (dying)
+		hdr.flags |= CPU_TO_BE16(GOSSIP_STORE_DYING_BIT);
 	hdr.crc = cpu_to_be32(crc32c(timestamp, msg, msglen));
 	hdr.timestamp = cpu_to_be32(timestamp);
 
@@ -246,7 +248,7 @@ static u32 gossip_store_compact_offline(struct routing_state *rstate)
 	oldlen = lseek(old_fd, SEEK_END, 0);
 	newlen = lseek(new_fd, SEEK_END, 0);
 	append_msg(old_fd, towire_gossip_store_ended(tmpctx, newlen),
-		   0, false, false, &oldlen);
+		   0, false, false, false, &oldlen);
 	close(old_fd);
 	status_debug("gossip_store_compact_offline: %zu deleted, %zu copied",
 		     deleted, count);
@@ -526,7 +528,7 @@ bool gossip_store_compact(struct gossip_store *gs)
 
 	/* Write end marker now new one is ready */
 	append_msg(gs->fd, towire_gossip_store_ended(tmpctx, len),
-		   0, false, false, &gs->len);
+		   0, false, false, false, &gs->len);
 
 	gs->count = count;
 	gs->deleted = 0;
@@ -547,19 +549,19 @@ disable:
 
 u64 gossip_store_add(struct gossip_store *gs, const u8 *gossip_msg,
 		     u32 timestamp, bool zombie,
-		     bool spam, const u8 *addendum)
+		     bool spam, bool dying, const u8 *addendum)
 {
 	u64 off = gs->len;
 
 	/* Should never get here during loading! */
 	assert(gs->writable);
 
-	if (!append_msg(gs->fd, gossip_msg, timestamp, zombie, spam, &gs->len)) {
+	if (!append_msg(gs->fd, gossip_msg, timestamp, zombie, spam, dying, &gs->len)) {
 		status_broken("Failed writing to gossip store: %s",
 			      strerror(errno));
 		return 0;
 	}
-	if (addendum && !append_msg(gs->fd, addendum, 0, false, false, &gs->len)) {
+	if (addendum && !append_msg(gs->fd, addendum, 0, false, false, false, &gs->len)) {
 		status_broken("Failed writing addendum to gossip store: %s",
 			      strerror(errno));
 		return 0;
@@ -576,7 +578,7 @@ u64 gossip_store_add_private_update(struct gossip_store *gs, const u8 *update)
 	/* A local update for an unannounced channel: not broadcastable, but
 	 * otherwise the same as a normal channel_update */
 	const u8 *pupdate = towire_gossip_store_private_update(tmpctx, update);
-	return gossip_store_add(gs, pupdate, 0, false, false, NULL);
+	return gossip_store_add(gs, pupdate, 0, false, false, false, NULL);
 }
 
 void gossip_store_mark_dying(struct gossip_store *gs,
@@ -684,7 +686,7 @@ void gossip_store_mark_channel_deleted(struct gossip_store *gs,
 				       const struct short_channel_id *scid)
 {
 	gossip_store_add(gs, towire_gossip_store_delete_chan(tmpctx, scid),
-			 0, false, false, NULL);
+			 0, false, false, false, NULL);
 }
 
 static void mark_zombie(struct gossip_store *gs,

gossipd/gossip_store.h

@@ -38,14 +38,14 @@ u64 gossip_store_add_private_update(struct gossip_store *gs, const u8 *update);
  * @gs: gossip store
  * @gossip_msg: the gossip message to insert.
  * @timestamp: the timestamp for filtering of this messsage.
- * @push: true if this should be sent to peers despite any timestamp filters.
- * @spam: true if this message is rate-limited and squelched to peers.
  * @zombie: true if this channel is missing a current channel_update.
+ * @spam: true if this message is rate-limited and squelched to peers.
+ * @dying: true if this message is for a dying channel.
  * @addendum: another message to append immediately after this
  *            (for appending amounts to channel_announcements for internal use).
  */
 u64 gossip_store_add(struct gossip_store *gs, const u8 *gossip_msg,
-		     u32 timestamp, bool zombie, bool spam,
+		     u32 timestamp, bool zombie, bool spam, bool dying,
 		     const u8 *addendum);
 
 

gossipd/routing.c

@@ -465,6 +465,7 @@ static void force_node_announce_rexmit(struct routing_state *rstate,
 					     node->bcast.timestamp,
 					     false,
 					     false,
+					     false,
 					     NULL);
 	if (node->rgraph.index == initial_bcast_index){
 		node->rgraph.index = node->bcast.index;
@@ -478,6 +479,7 @@ static void force_node_announce_rexmit(struct routing_state *rstate,
 						      node->rgraph.timestamp,
 						      false,
 						      true,
+						      false,
 						      NULL);
 	}
 }
@@ -847,6 +849,7 @@ static void add_channel_announce_to_broadcast(struct routing_state *rstate,
 						     chan->bcast.timestamp,
 						     false,
 						     false,
+						     false,
 						     addendum);
 	rstate->local_channel_announced |= is_local;
 }
@@ -1315,6 +1318,16 @@ static void delete_spam_update(struct routing_state *rstate,
 	hc->rgraph.timestamp = hc->bcast.timestamp;
 }
 
+static bool is_chan_dying(struct routing_state *rstate,
+			  const struct short_channel_id *scid)
+{
+	for (size_t i = 0; i < tal_count(rstate->dying_channels); i++) {
+		if (short_channel_id_eq(&rstate->dying_channels[i].scid, scid))
+			return true;
+	}
+	return false;
+}
+
 bool routing_add_channel_update(struct routing_state *rstate,
 				const u8 *update TAKES,
 				u32 index,
@@ -1339,6 +1352,7 @@ bool routing_add_channel_update(struct routing_state *rstate,
 	struct amount_sat sat;
 	bool spam;
 	bool zombie;
+	bool dying;
 
 	/* Make sure we own msg, even if we don't save it. */
 	if (taken(update))
@@ -1360,6 +1374,7 @@ bool routing_add_channel_update(struct routing_state *rstate,
 		uc = NULL;
 		sat = chan->sat;
 		zombie = is_chan_zombie(chan);
+		dying = is_chan_dying(rstate, &short_channel_id);
 	} else {
 		/* Maybe announcement was waiting for this update? */
 		uc = get_unupdated_channel(rstate, &short_channel_id);
@@ -1369,6 +1384,7 @@ bool routing_add_channel_update(struct routing_state *rstate,
 		sat = uc->sat;
 		/* When loading zombies from the store. */
 		zombie = force_zombie_flag;
+		dying = false;
 	}
 
 	/* Reject update if the `htlc_maximum_msat` is greater
@@ -1531,7 +1547,7 @@ bool routing_add_channel_update(struct routing_state *rstate,
 		chan->bcast.index =
 			gossip_store_add(rstate->gs, zombie_announcement,
 					 chan->bcast.timestamp,
-					 false, false, zombie_addendum);
+					 false, false, false, zombie_addendum);
 		/* Deletion of the old addendum is optional. */
 		/* This opposing channel_update has been stashed away.  Now that
 		 * there are two valid updates, this one gets restored. */
@@ -1554,12 +1570,12 @@ bool routing_add_channel_update(struct routing_state *rstate,
 		chan->half[!direction].bcast.index =
 			gossip_store_add(rstate->gs, zombie_update[0],
 					 chan->half[!direction].bcast.timestamp,
-					 false, false, NULL);
+					 false, false, false, NULL);
 		if (zombie_update[1])
 			chan->half[!direction].rgraph.index =
 				gossip_store_add(rstate->gs, zombie_update[1],
 						 chan->half[!direction].rgraph.timestamp,
-						 false, true, NULL);
+						 false, true, false, NULL);
 		else
 			chan->half[!direction].rgraph.index = chan->half[!direction].bcast.index;
 
@@ -1577,7 +1593,7 @@ bool routing_add_channel_update(struct routing_state *rstate,
 	} else {
 		hc->rgraph.index
 			= gossip_store_add(rstate->gs, update, timestamp,
-					   zombie, spam, NULL);
+					   zombie, spam, dying, NULL);
 		if (hc->bcast.timestamp > rstate->last_timestamp
 		    && hc->bcast.timestamp < time_now().ts.tv_sec)
 			rstate->last_timestamp = hc->bcast.timestamp;
@@ -1596,8 +1612,9 @@ bool routing_add_channel_update(struct routing_state *rstate,
 	}
 
 	status_peer_debug(source_peer,
-			  "Received %schannel_update for channel %s/%d now %s",
+			  "Received %schannel_update for %schannel %s/%d now %s",
 			  ignore_timestamp ? "(forced) " : "",
+			  dying ? "dying ": "",
 			  type_to_string(tmpctx, struct short_channel_id,
 					 &short_channel_id),
 			  channel_flags & 0x01,
@@ -1899,7 +1916,7 @@ bool routing_add_node_announcement(struct routing_state *rstate,
 	} else {
 		node->rgraph.index
 			= gossip_store_add(rstate->gs, msg, timestamp,
-					   false, spam, NULL);
+					   false, spam, false, NULL);
 		if (node->bcast.timestamp > rstate->last_timestamp
 		    && node->bcast.timestamp < time_now().ts.tv_sec)
 			rstate->last_timestamp = node->bcast.timestamp;
@@ -2131,7 +2148,7 @@ bool routing_add_private_channel(struct routing_state *rstate,
 		u8 *msg = towire_gossip_store_private_channel(tmpctx,
 							      capacity,
 							      chan_ann);
-		index = gossip_store_add(rstate->gs, msg, 0, false, false,
+		index = gossip_store_add(rstate->gs, msg, 0, false, false, false,
 					 NULL);
 	}
 	chan->bcast.index = index;
@@ -2277,7 +2294,7 @@ void routing_channel_spent(struct routing_state *rstate,
 
 	/* Save to gossip_store in case we restart */
 	msg = towire_gossip_store_chan_dying(tmpctx, &chan->scid, deadline);
-	index = gossip_store_add(rstate->gs, msg, 0, false, false, NULL);
+	index = gossip_store_add(rstate->gs, msg, 0, false, false, false, NULL);
 
 	/* Mark it dying, so we don't gossip it */
 	gossip_store_mark_dying(rstate->gs, &chan->bcast,

gossipd/test/run-check_channel_announcement.c

@@ -61,7 +61,7 @@ bool cupdate_different(struct gossip_store *gs UNNEEDED,
 { fprintf(stderr, "cupdate_different called!\n"); abort(); }
 /* Generated stub for gossip_store_add */
 u64 gossip_store_add(struct gossip_store *gs UNNEEDED, const u8 *gossip_msg UNNEEDED,
-		     u32 timestamp UNNEEDED, bool zombie UNNEEDED, bool spam UNNEEDED,
+		     u32 timestamp UNNEEDED, bool zombie UNNEEDED, bool spam UNNEEDED, bool dying UNNEEDED,
 		     const u8 *addendum UNNEEDED)
 { fprintf(stderr, "gossip_store_add called!\n"); abort(); }
 /* Generated stub for gossip_store_add_private_update */

gossipd/test/run-txout_failure.c

@@ -32,7 +32,7 @@ bool cupdate_different(struct gossip_store *gs UNNEEDED,
 { fprintf(stderr, "cupdate_different called!\n"); abort(); }
 /* Generated stub for gossip_store_add */
 u64 gossip_store_add(struct gossip_store *gs UNNEEDED, const u8 *gossip_msg UNNEEDED,
-		     u32 timestamp UNNEEDED, bool zombie UNNEEDED, bool spam UNNEEDED,
+		     u32 timestamp UNNEEDED, bool zombie UNNEEDED, bool spam UNNEEDED, bool dying UNNEEDED,
 		     const u8 *addendum UNNEEDED)
 { fprintf(stderr, "gossip_store_add called!\n"); abort(); }
 /* Generated stub for gossip_store_add_private_update */