feat: listchannels filter by destination

contrib/pyln-client/pyln/client/lightning.py

@@ -844,13 +844,15 @@ def invoice(self, msatoshi, label, description, expiry=None, fallbacks=None, pre
         }
         return self.call("invoice", payload)
 
-    def listchannels(self, short_channel_id=None, source=None):
+    def listchannels(self, short_channel_id=None, source=None, destination=None):
         """
-        Show all known channels, accept optional {short_channel_id} or {source}.
+        Show all known channels or filter by optional
+        {short_channel_id}, {source} or {destination}.
         """
         payload = {
             "short_channel_id": short_channel_id,
-            "source": source
+            "source": source,
+            "destination": destination
         }
         return self.call("listchannels", payload)
 

doc/lightning-listchannels.7.md

@@ -4,7 +4,7 @@ lightning-listchannels -- Command to query active lightning channels in the enti
 SYNOPSIS
 --------
 
-**listchannels** \[*short\_channel\_id*\] \[*source*\]
+**listchannels** \[*short\_channel\_id*\] \[*source*\] \[*destination*\]
 
 DESCRIPTION
 -----------
@@ -19,7 +19,11 @@ matching *short\_channel\_id* are returned.  Otherwise, it must be null.
 If *source* is a node id, then only channels leading from that node id
 are returned.
 
-If neither is supplied, data on all lightning channels known to this
+If *destination* is a node id, then only channels leading to that node id
+are returned.
+
+Only one of *short\_channgel\_id*, *source* or *destination* can be supplied.
+If nothing is supplied, data on all lightning channels known to this
 node, are returned. These can be local channels or public channels
 broadcast on the gossip network.
 
@@ -44,8 +48,8 @@ On success, an object containing **channels** is returned.  It is an array of ob
 - **htlc_maximum_msat** (msat, optional): The largest payment *source* will allow via this channel
 [comment]: # (GENERATE-FROM-SCHEMA-END)
 
-If *short\_channel\_id* or *source* is supplied and no matching channels
-are found, a "channels" object with an empty list is returned.
+If one of *short\_channel\_id*, *source* or *destination* is supplied and no
+matching channels are found, a "channels" object with an empty list is returned.
 
 On error the returned object will contain `code` and `message` properties,
 with `code` being one of the following:

plugins/topology.c

@@ -371,6 +371,7 @@ static void json_add_halfchan(struct json_stream *response,
 
 struct listchannels_opts {
 	struct node_id *source;
+	struct node_id *destination;
 	struct short_channel_id *scid;
 };
 
@@ -456,6 +457,18 @@ static struct command_result *listpeers_done(struct command *cmd,
 						  c, 1 << dir);
 			}
 		}
+	} else if (opts->destination) {
+		struct gossmap_node *dst;
+
+		dst = gossmap_find_node(gossmap, opts->destination);
+		if (dst) {
+			for (size_t i = 0; i < dst->num_chans; i++) {
+				int dir;
+				c = gossmap_nth_chan(gossmap, dst, i, &dir);
+				json_add_halfchan(js, gossmap, connected,
+						  c, 1 << !dir);
+			}
+		}
 	} else {
 		for (c = gossmap_first_chan(gossmap);
 		     c;
@@ -480,12 +493,15 @@ static struct command_result *json_listchannels(struct command *cmd,
 		   p_opt("short_channel_id", param_short_channel_id,
 			 &opts->scid),
 		   p_opt("source", param_node_id, &opts->source),
+		   p_opt("destination", param_node_id, &opts->destination),
 		   NULL))
 		return command_param_failed();
 
-	if (opts->scid && opts->source)
+	if (!!opts->scid + !!opts->source + !!opts->destination > 1)
 		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
-				    "Cannot specify both source and short_channel_id");
+				    "Can only specify one of "
+				    "`short_channel_id`, "
+				    "`source` or `destination`");
 	req = jsonrpc_request_start(cmd->plugin, cmd, "listpeers",
 				    listpeers_done, forward_error, opts);
 	return send_outreq(cmd->plugin, req);
@@ -694,7 +710,8 @@ static const struct plugin_command commands[] = {
 		"listchannels",
 		"channels",
 		"List all known channels in the network",
-		"Show channel {short_channel_id} or {source} (or all known channels, if not specified)",
+		"Show channels for {short_channel_id}, {source} or {destination} "
+		"(or all known channels, if not specified)",
 		json_listchannels,
 	},
 	{

tests/test_gossip.py

@@ -281,7 +281,18 @@ def test_gossip_jsonrpc(node_factory):
     assert only_one(channels1)['destination'] == l2.info['id']
     assert channels1 == channels2
 
-    l2.rpc.listchannels()['channels']
+    # Test listchannels-by-destination
+    channels1 = l1.rpc.listchannels(destination=l1.info['id'])['channels']
+    channels2 = l2.rpc.listchannels(destination=l1.info['id'])['channels']
+    assert only_one(channels1)['destination'] == l1.info['id']
+    assert only_one(channels1)['source'] == l2.info['id']
+    assert channels1 == channels2
+
+    # Test only one of short_channel_id, source or destination can be supplied
+    with pytest.raises(RpcError, match=r"Can only specify one of.*"):
+        l1.rpc.listchannels(source=l1.info['id'], destination=l2.info['id'])
+    with pytest.raises(RpcError, match=r"Can only specify one of.*"):
+        l1.rpc.listchannels(short_channel_id="1x1x1", source=l2.info['id'])
 
     # Now proceed to funding-depth and do a full gossip round
     l1.bitcoin.generate_block(5)