plugins/topology: add direction field to listchannels.

It's a core concept in the spec which isn't directly exposed.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSON-RPC: `listchannels` added a `direction` field (0 or 1) as per gossip specification.

.msggen.json

@@ -545,6 +545,7 @@
             "ListChannels.channels[].channel_flags": 7,
             "ListChannels.channels[].delay": 12,
             "ListChannels.channels[].destination": 2,
+            "ListChannels.channels[].direction": 16,
             "ListChannels.channels[].features": 15,
             "ListChannels.channels[].fee_per_millionth": 11,
             "ListChannels.channels[].htlc_maximum_msat": 14,

contrib/pyln-testing/pyln/testing/grpc2py.py

@@ -258,6 +258,7 @@ def listchannels_channels2py(m):
         "source": hexlify(m.source),  # PrimitiveField in generate_composite
         "destination": hexlify(m.destination),  # PrimitiveField in generate_composite
         "short_channel_id": m.short_channel_id,  # PrimitiveField in generate_composite
+        "direction": m.direction,  # PrimitiveField in generate_composite
         "public": m.public,  # PrimitiveField in generate_composite
         "amount_msat": amount2msat(m.amount_msat),  # PrimitiveField in generate_composite
         "message_flags": m.message_flags,  # PrimitiveField in generate_composite

doc/lightning-listchannels.7.md

@@ -36,6 +36,7 @@ On success, an object containing **channels** is returned.  It is an array of ob
 - **source** (pubkey): the source node
 - **destination** (pubkey): the destination node
 - **short\_channel\_id** (short\_channel\_id): short channel id of channel
+- **direction** (u32): direction (0 if source < destination, 1 otherwise).
 - **public** (boolean): true if this is announced (otherwise it must be our channel)
 - **amount\_msat** (msat): the total capacity of this channel (always a whole number of satoshis)
 - **message\_flags** (u8): as defined by BOLT #7
@@ -79,4 +80,4 @@ Lightning RFC site
 -   BOLT \#7:
     <https://github.com/lightning/bolts/blob/master/07-routing-gossip.md>
 
-[comment]: # ( SHA256STAMP:d8d52272963a9ec4708fd3ae41585ddd8120bb5444c03219a7b728f0b2e09ec3)
+[comment]: # ( SHA256STAMP:78f59780528ae5cd33c3607ed11b128cc94e1e0a5e2babd59cb99574a3f5f956)

doc/schemas/listchannels.schema.json

@@ -15,6 +15,7 @@
           "source",
           "destination",
           "short_channel_id",
+          "direction",
           "public",
           "amount_msat",
           "message_flags",
@@ -40,6 +41,10 @@
             "type": "short_channel_id",
             "description": "short channel id of channel"
           },
+          "direction": {
+            "type": "u32",
+            "description": "direction (0 if source < destination, 1 otherwise)."
+          },
           "public": {
             "type": "boolean",
             "description": "true if this is announced (otherwise it must be our channel)"

plugins/topology.c

@@ -244,6 +244,7 @@ static void json_add_halfchan(struct json_stream *response,
 		json_add_node_id(response, "source", &node_id[dir]);
 		json_add_node_id(response, "destination", &node_id[!dir]);
 		json_add_short_channel_id(response, "short_channel_id", &scid);
+		json_add_num(response, "direction", dir);
 		json_add_bool(response, "public", !c->private);
 
 		gossmap_chan_get_update_details(gossmap, c, dir,

tests/test_gossip.py

@@ -425,13 +425,21 @@ def test_gossip_jsonrpc(node_factory):
     channels2 = l2.rpc.listchannels(source=l1.info['id'])['channels']
     assert only_one(channels1)['source'] == l1.info['id']
     assert only_one(channels1)['destination'] == l2.info['id']
+    if l1.info['id'] > l2.info['id']:
+        assert only_one(channels1)['direction'] == 1
+    else:
+        assert only_one(channels1)['direction'] == 0
     assert channels1 == channels2
 
     # 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']
+    if l2.info['id'] > l1.info['id']:
+        assert only_one(channels1)['direction'] == 1
+    else:
+        assert only_one(channels1)['direction'] == 0
     assert channels1 == channels2
 
     # Test only one of short_channel_id, source or destination can be supplied