openingd: Implement sendcustommsg handling in openingd

Most of the work is done in `lightningd`, here we just need to queue the
message itself.

openingd/openingd.c

@@ -1355,6 +1355,14 @@ static void handle_dev_memleak(struct state *state, const u8 *msg)
 			take(towire_opening_dev_memleak_reply(NULL,
 							      found_leak)));
 }
+
+/* We were told to send a custommsg to the peer by `lightningd`. All the
+ * verification is done on the side of `lightningd` so we should be good to
+ * just forward it here. */
+static void openingd_send_custommsg(struct state *state, const u8 *msg)
+{
+	sync_crypto_write(state->pps, take(msg));
+}
 #endif /* DEVELOPER */
 
 /* Standard lightningd-fd-is-ready-to-read demux code.  Again, we could hang
@@ -1418,7 +1426,7 @@ static u8 *handle_master_in(struct state *state)
 	switch ((enum common_wire_type)t) {
 #if DEVELOPER
 	case WIRE_CUSTOMMSG_OUT:
-		/* TODO(cdecker) Add handling of custom messages. */
+		openingd_send_custommsg(state, msg);
 		return NULL;
 #else
 	case WIRE_CUSTOMMSG_OUT:

tests/test_misc.py

@@ -2060,3 +2060,47 @@ def test_waitblockheight(node_factory, executor, bitcoind):
     bitcoind.generate_block(1)
     sync_blockheight(bitcoind, [node])
     fut2.result(5)
+
+
+@unittest.skipIf(not DEVELOPER, "Needs dev-sendcustommsg")
+def test_sendcustommsg(node_factory):
+    """Check that we can send custommsgs to peers in various states.
+
+    `l2` is the node under test. `l1` has a channel with `l2` and should
+    therefore be attached to `channeld`. `l4` is just connected, so it should
+    be attached to `openingd`. `l3` has a channel open, but is disconnected
+    and we can't send to it.
+
+    """
+    l1, l2, l3 = node_factory.line_graph(3, opts={'log-level': 'io'})
+    l4 = node_factory.get_node(options={'log-level': 'io'})
+    l2.connect(l4)
+    l3.stop()
+    msg = r'ff' * 32
+    serialized = r'04070020' + msg
+
+    # This address doesn't exist so we should get an error when we try sending
+    # a message to it.
+    node_id = '02df5ffe895c778e10f7742a6c5b8a0cefbe9465df58b92fadeb883752c8107c8f'
+    with pytest.raises(RpcError, match=r'No such peer'):
+        l1.rpc.dev_sendcustommsg(node_id, msg)
+
+    # `l3` is disconnected and we can't send messages to it
+    assert(not l2.rpc.listpeers(l3.info['id'])['peers'][0]['connected'])
+    with pytest.raises(RpcError, match=r'Peer is not connected'):
+        l2.rpc.dev_sendcustommsg(l3.info['id'], msg)
+
+    # We should not be able to send a bogus `ping` message, since it collides
+    # with a message defined in the spec, and could potentially mess up our
+    # internal state.
+    with pytest.raises(RpcError, match=r'Cannot send messages of type 18 .WIRE_PING.'):
+        l2.rpc.dev_sendcustommsg(l2.info['id'], r'0012')
+
+    l2.rpc.dev_sendcustommsg(l1.info['id'], msg)
+    l2.rpc.dev_sendcustommsg(l4.info['id'], msg)
+    l2.daemon.wait_for_log(
+        r'{peer_id}-openingd-chan#[0-9]: \[OUT\] {serialized}'.format(
+            serialized=serialized, peer_id=l4.info['id']
+        )
+    )
+    l4.daemon.wait_for_log(r'\[IN\] {}'.format(serialized))

wallet/test/run-wallet.c

@@ -640,6 +640,12 @@ struct txowatch *watch_txo(const tal_t *ctx UNNEEDED,
 						   size_t input_num UNNEEDED,
 						   const struct block *block))
 { fprintf(stderr, "watch_txo called!\n"); abort(); }
+/* Generated stub for wire_type_is_defined */
+bool wire_type_is_defined(u16 type UNNEEDED)
+{ fprintf(stderr, "wire_type_is_defined called!\n"); abort(); }
+/* Generated stub for wire_type_name */
+const char *wire_type_name(int e UNNEEDED)
+{ fprintf(stderr, "wire_type_name called!\n"); abort(); }
 /* AUTOGENERATED MOCKS END */
 
 #if DEVELOPER