mctpd: Add Network1.LearnEndpoint

Our current support for bridged endpoints requires static EIDs to be
allocated in advance. To handle that case, add a new dbus call:
LearnEndpoint, on the net object (au.com.codeconstruct.MCTP.Network1).

This takes an EID, performs a discovery query, and publishes a new
endpoint object if that query was sucessful. This allows dbus clients to
enumerate briged EPs.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>

Author: jk-ozlabs

CHANGELOG.md

@@ -11,7 +11,11 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 1. New debug tool, `mctp-bench`, for sending and receiving a stream of MCTP
    messages between two processes.
 
-2. mctpd: Add `au.com.codeconstruct.MCTP.Network1` interface
+2. mctpd: Add `au.com.codeconstruct.MCTP.Network1` interface, including
+    - a `LocalEIDs` property, representing the local EIDs assigned on this
+      network
+    - a `LearnEndpoint` method, for enumerating endpoints that already have an
+      address assigned, and are routable
 
 3. tests: the fake mctp environment can now be run standalone, allowing
    experimentation with different system and network configurations

docs/mctpd.md

@@ -156,11 +156,22 @@ All MCTP networks objects host the `au.com.codeconstruct.MCTP.Network1` dbus
 interface:
 
 ```
-NAME                                 TYPE      SIGNATURE RESULT/VALUE FLAGS
+NAME                                TYPE      SIGNATURE RESULT/VALUE FLAGS
 au.com.codeconstruct.MCTP.Network1  interface -         -            -
+.LearnEndpoint                      method    y         sb           -
 .LocalEIDs                          property  ay        1 8          const
 ```
 
+### `.LearnEndpoint`: `y`
+
+The `LearnEndpoint` method allows a caller to perform enumeration of a
+static endpoint that we can already route to. This may be useful to discover
+bridged endpoints, where the EID assigment has already been handled by the
+bridge.
+
+`LearnEndpoint` takes an EID as its only argument, and returns the endpoint's
+path, and a boolean indicating whether the endpoint was newly discovered.
+
 The D-Bus interface includes the `LocalEIDs` property which reports BMC local EIDs
 in the network.
 

src/mctpd.c

@@ -2731,6 +2731,46 @@ static int method_endpoint_set_mtu(sd_bus_message *call, void *data,
 	return rc;
 }
 
+static int method_net_learn_endpoint(sd_bus_message *call, void *data,
+				     sd_bus_error *berr)
+{
+	const char *peer_path = NULL;
+	struct net *net = data;
+	struct ctx *ctx = net->ctx;
+	dest_phys dest = { 0 };
+	mctp_eid_t eid = 0;
+	struct peer *peer;
+	int rc;
+
+	rc = sd_bus_message_read(call, "y", &eid);
+	if (rc < 0)
+		goto err;
+
+	peer = find_peer_by_addr(ctx, eid, net->net);
+	/* already known? */
+	if (peer)
+		return sd_bus_reply_method_return(call, "sb",
+						  path_from_peer(peer), false);
+
+	rc = add_peer(ctx, &dest, eid, net->net, &peer);
+	if (rc) {
+		warnx("can't add peer: %s", strerror(-rc));
+		goto err;
+	}
+
+	query_peer_properties(peer);
+
+	publish_peer(peer, false);
+
+	peer_path = path_from_peer(peer);
+	if (!peer_path)
+		goto err;
+	return sd_bus_reply_method_return(call, "sb", peer_path, 1);
+err:
+	set_berr(ctx, rc, berr);
+	return rc;
+}
+
 // Testing code
 static int cb_test_timer(sd_event_source *s, uint64_t t, void* data)
 {
@@ -3110,6 +3150,14 @@ static const sd_bus_vtable bus_link_vtable[] = {
 
 static const sd_bus_vtable bus_network_vtable[] = {
 	SD_BUS_VTABLE_START(0),
+	SD_BUS_METHOD_WITH_NAMES("LearnEndpoint",
+		"y",
+		SD_BUS_PARAM(physaddr),
+		"sb",
+		SD_BUS_PARAM(path)
+		SD_BUS_PARAM(found),
+		method_net_learn_endpoint,
+		0),
 	SD_BUS_PROPERTY("LocalEIDs",
 			"ay",
 			bus_network_get_prop,

tests/test_mctpd.py

@@ -483,3 +483,21 @@ async def test_network_local_eids_none(dbus, mctpd):
     eids = list(await net.get_local_eids())
 
     assert eids == []
+
+""" Bridged EP can be discovered via Network1.LearnEndpoint """
+async def test_bridged_learn_endpoint(dbus, mctpd):
+    iface = mctpd.system.interfaces[0]
+    ep = mctpd.network.endpoints[0]
+    br_ep = Endpoint(iface, bytes(), eid = 10, types = [0, 2])
+    ep.add_bridged_ep(br_ep)
+    mctpd.network.add_endpoint(br_ep)
+
+    await mctpd.system.add_route(mctpd.system.Route(iface, br_ep.eid, 1))
+    # static neighbour; no gateway route support at present
+    await mctpd.system.add_neighbour(mctpd.system.Neighbour(iface, ep.lladdr, br_ep.eid))
+
+    net = await mctpd_mctp_network_obj(dbus, iface.net)
+    (path, new) = await net.call_learn_endpoint(br_ep.eid)
+
+    assert path == f'/au/com/codeconstruct/mctp1/networks/1/endpoints/{br_ep.eid}'
+    assert new