gossipd: return channel_announcement features for listchannels.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSON API: `listchannels` now shows channel `features`.

gossipd/gossipd.c

@@ -966,6 +966,41 @@ static struct gossip_halfchannel_entry *hc_entry(const tal_t *ctx,
 	return e;
 }
 
+/*~ We don't keep channel features in memory; they're rarely used.  So we
+ * remember if it exists, and load it off disk when needed. */
+static u8 *get_channel_features(const tal_t *ctx,
+				struct gossip_store *gs,
+				const struct chan *chan)
+{
+	secp256k1_ecdsa_signature sig;
+	u8 *features;
+	struct bitcoin_blkid chain_hash;
+	struct short_channel_id short_channel_id;
+	struct node_id node_id;
+	struct pubkey bitcoin_key;
+	struct amount_sat sats;
+	const u8 *ann;
+
+	/* This is where we stash a flag to indicate it exists. */
+	if (!chan->half[0].any_features)
+		return NULL;
+
+	/* Could be a channel_announcement, could be a local_add_channel */
+	ann = gossip_store_get(tmpctx, gs, chan->bcast.index);
+	if (!fromwire_channel_announcement(ctx, ann, &sig, &sig, &sig, &sig,
+					   &features, &chain_hash,
+					   &short_channel_id,
+					   &node_id, &node_id,
+					   &bitcoin_key, &bitcoin_key)
+	    && !fromwire_gossipd_local_add_channel(ctx, ann, &short_channel_id,
+						   &node_id, &sats, &features))
+		status_failed(STATUS_FAIL_INTERNAL_ERROR,
+			      "bad channel_announcement / local_add_channel at %u: %s",
+			      chan->bcast.index, tal_hex(tmpctx, ann));
+
+	return features;
+}
+
 /*~ Marshal (possibly) both channel directions into entries. */
 static void append_channel(struct routing_state *rstate,
 			   const struct gossip_getchannels_entry ***entries,
@@ -980,6 +1015,7 @@ static void append_channel(struct routing_state *rstate,
 	e->local_disabled = is_chan_local_disabled(rstate, chan);
 	e->public = is_chan_public(chan);
 	e->short_channel_id = chan->scid;
+	e->features = get_channel_features(e, rstate->gs, chan);
 	if (!srcfilter || node_id_eq(&e->node[0], srcfilter))
 		e->e[0] = hc_entry(*entries, chan, 0);
 	else

lightningd/gossip_control.c

@@ -482,6 +482,7 @@ static void json_add_halfchan(struct json_stream *response,
 	json_add_num(response, "delay", he->delay);
 	json_add_amount_msat_only(response, "htlc_minimum_msat", he->min);
 	json_add_amount_msat_only(response, "htlc_maximum_msat", he->max);
+	json_add_hex_talarr(response, "features", e->features);
 	json_object_end(response);
 }
 

lightningd/gossip_msg.c

@@ -143,6 +143,8 @@ fromwire_gossip_getchannels_entry(const tal_t *ctx,
 	fromwire_short_channel_id(pptr, max, &entry->short_channel_id);
 	entry->public = fromwire_bool(pptr, max);
 	entry->local_disabled = fromwire_bool(pptr, max);
+	entry->features = fromwire_tal_arrn(entry,
+					    pptr, max, fromwire_u16(pptr, max));
 
 	if (fromwire_bool(pptr, max)) {
 		entry->e[0] = tal(entry, struct gossip_halfchannel_entry);
@@ -180,6 +182,8 @@ void towire_gossip_getchannels_entry(u8 **pptr,
 	towire_short_channel_id(pptr, &entry->short_channel_id);
 	towire_bool(pptr, entry->public);
 	towire_bool(pptr, entry->local_disabled);
+	towire_u16(pptr, tal_bytelen(entry->features));
+	towire_u8_array(pptr, entry->features, tal_bytelen(entry->features));
 	if (entry->e[0]) {
 		towire_bool(pptr, true);
 		towire_gossip_halfchannel_entry(pptr, entry->e[0]);

lightningd/gossip_msg.h

@@ -33,6 +33,7 @@ struct gossip_getchannels_entry {
 	bool local_disabled;
 	/* NULL if we haven't received an update */
 	struct gossip_halfchannel_entry *e[2];
+	u8 *features;
 };
 
 struct gossip_getnodes_entry *

tests/test_gossip.py

@@ -1709,7 +1709,9 @@ def test_gossip_store_upgrade_v7_v8(node_factory):
          'fee_per_millionth': 10,
          'delay': 6,
          'htlc_minimum_msat': Millisatoshi(0),
-         'htlc_maximum_msat': Millisatoshi(990000000)},
+         'htlc_maximum_msat': Millisatoshi(990000000),
+         # This store was created on an experimental branch (OPT_ONION_MESSAGES)
+         'features': '80000000000000000000000000'},
         {'source': '0266e4598d1d3c415f572a8488830b60f7e744ed9235eb0b1ba93283b315c03518',
          'destination': '022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59',
          'short_channel_id': '103x1x1',
@@ -1724,4 +1726,5 @@ def test_gossip_store_upgrade_v7_v8(node_factory):
          'fee_per_millionth': 10,
          'delay': 6,
          'htlc_minimum_msat': Millisatoshi(0),
-         'htlc_maximum_msat': Millisatoshi(990000000)}]
+         'htlc_maximum_msat': Millisatoshi(990000000),
+         'features': '80000000000000000000000000'}]

tests/utils.py

@@ -18,3 +18,12 @@ def expected_node_features():
     """Return the expected node features hexstring for this configuration"""
     # features 1, 3, 7, 9, 11, 13, 15, 17 and 55 (0x8000000002aaa2).
     return "8000000002aaa2"
+
+
+def expected_channel_features():
+    """Return the expected channel features hexstring for this configuration"""
+    # experimental OPT_ONION_MESSAGES
+    if EXPERIMENTAL_FEATURES:
+        return '80000000000000000000000000'
+    else:
+        return ''