channeld: Fix the shutdown_sent billboard direction

[cdecker]

While debugging a hanging channel with a user I noticed that they
called close on a channel, resulting in the channel showing
CHANNELD_SHUTTING_DOWN, but the billboard seemed to show the
information the wrong way around:

{
   "peers": [
      {
         "connected": true,
	 // ...
         "channels": [
            {
               "state": "CHANNELD_SHUTTING_DOWN",
	       // ...
               "status": [
                  "CHANNELD_SHUTTING_DOWN:Reconnected, and reestablished.",
                  "CHANNELD_SHUTTING_DOWN:Funding transaction locked. They need our announcement signatures. They've sent shutdown, waiting for ours"
               ],
	       // ...
            }
         ]
      }
   ]
}

Aside from the hung channel, the switch in direction of the status
seemed weird. Checking the billboard code seems to have the status
switched as well:

lightning/channeld/channeld.c

Lines 223 to 226 in ff88308

	else if (!peer->shutdown_sent[LOCAL] && peer->shutdown_sent[REMOTE])
	shutdown_status = " We've send shutdown, waiting for theirs";
	else if (peer->shutdown_sent[LOCAL] && !peer->shutdown_sent[REMOTE])
	shutdown_status = " They've sent shutdown, waiting for ours";

We set shutdown_sent[LOCAL] when we send the shutdown:

lightning/channeld/channeld.c

Lines 823 to 839 in ff88308

	static void maybe_send_shutdown(struct peer *peer)
	{
	u8 *msg;
	if (!peer->send_shutdown)
	return;
	/* Send a disable channel_update so others don't try to route
	* over us */
	send_channel_update(peer, ROUTING_FLAGS_DISABLED);
	msg = towire_shutdown(NULL, &peer->channel_id, peer->final_scriptpubkey);
	sync_crypto_write(peer->pps, take(msg));
	peer->send_shutdown = false;
	peer->shutdown_sent[LOCAL] = true;
	billboard_update(peer);
	}

And we set shutdown_sent[REMOTE] when we receive the shutdown:

lightning/channeld/channeld.c

Lines 1730 to 1781 in ff88308

	static void handle_peer_shutdown(struct peer *peer, const u8 *shutdown)
	{
	struct channel_id channel_id;
	u8 *scriptpubkey;
	/* Disable the channel. */
	send_channel_update(peer, ROUTING_FLAGS_DISABLED);
	if (!fromwire_shutdown(tmpctx, shutdown, &channel_id, &scriptpubkey))
	peer_failed(peer->pps,
	&peer->channel_id,
	"Bad shutdown %s", tal_hex(peer, shutdown));
	/* BOLT #2:
	*
	* - if both nodes advertised the `option_upfront_shutdown_script`
	* feature, and the receiving node received a non-zero-length
	* `shutdown_scriptpubkey` in `open_channel` or `accept_channel`, and
	* that `shutdown_scriptpubkey` is not equal to `scriptpubkey`:
	* - MUST fail the connection.
	*/
	/* openingd only sets this if feature was negotiated at opening. */
	if (tal_count(peer->remote_upfront_shutdown_script)
	&& !memeq(scriptpubkey, tal_count(scriptpubkey),
	peer->remote_upfront_shutdown_script,
	tal_count(peer->remote_upfront_shutdown_script)))
	peer_failed(peer->pps,
	&peer->channel_id,
	"scriptpubkey %s is not as agreed upfront (%s)",
	tal_hex(peer, scriptpubkey),
	tal_hex(peer, peer->remote_upfront_shutdown_script));
	/* Tell master: we don't have to wait because on reconnect other end
	* will re-send anyway. */
	wire_sync_write(MASTER_FD,
	take(towire_channeld_got_shutdown(NULL, scriptpubkey)));
	peer->shutdown_sent[REMOTE] = true;
	/* BOLT #2:
	*
	* A receiving node:
	* ...
	* - once there are no outstanding updates on the peer, UNLESS
	* it has already sent a `shutdown`:
	* - MUST reply to a `shutdown` message with a `shutdown`
	*/
	if (!peer->shutdown_sent[LOCAL]) {
	peer->send_shutdown = true;
	start_commit_timer(peer);
	}
	billboard_update(peer);
	}

So I think the billboard code just needs to be switched around.

Changelog-Fixed: JSON-RPC: The status of the shutdown meesages being exchanged is now displayed correctly.

[rustyrussell]

Ack 9c355bc