mctpd: Send Discovery Notify on Endpoint role set

This commit adds support for Discovery Notify messages, specified in
DSP0236 section 12.14.

In our implementation, a Discovery Notify message is sent when mctpd
sets an interface role from Unknown to Endpoint.

To avoid notify discovery messages getting lost, retry the messages for
a few time with delays.

Signed-off-by: Khang D Nguyen <[email protected]>

Author: khangng-ampere

src/mctpd.c

@@ -126,7 +126,6 @@ enum discovery_state {
 };
 
 struct link {
-	enum discovery_state discovered;
 	bool published;
 	int ifindex;
 	enum endpoint_role role;
@@ -135,6 +134,14 @@ struct link {
 	sd_bus_slot *slot_iface;
 	sd_bus_slot *slot_busowner;
 
+	struct {
+		enum discovery_state flag;
+		sd_event_source *notify_source;
+		dest_phys notify_dest;
+		uint64_t notify_retry_delay;
+		uint8_t notify_retries_left;
+	} discovery;
+
 	struct ctx *ctx;
 };
 
@@ -793,8 +800,8 @@ static int handle_control_set_endpoint_id(struct ctx *ctx, int sd,
 			warnx("ERR: cannot add bus owner to object lists");
 		}
 
-		if (link_data->discovered != DISCOVERY_UNSUPPORTED) {
-			link_data->discovered = DISCOVERY_DISCOVERED;
+		if (link_data->discovery.flag != DISCOVERY_UNSUPPORTED) {
+			link_data->discovery.flag = DISCOVERY_DISCOVERED;
 		}
 		resp->status =
 			SET_MCTP_EID_ASSIGNMENT_STATUS(MCTP_SET_EID_ACCEPTED) |
@@ -805,13 +812,13 @@ static int handle_control_set_endpoint_id(struct ctx *ctx, int sd,
 		return reply_message(ctx, sd, resp, resp_len, addr);
 
 	case MCTP_SET_EID_DISCOVERED:
-		if (link_data->discovered == DISCOVERY_UNSUPPORTED) {
+		if (link_data->discovery.flag == DISCOVERY_UNSUPPORTED) {
 			resp->completion_code = MCTP_CTRL_CC_ERROR_INVALID_DATA;
 			resp_len = sizeof(struct mctp_ctrl_resp);
 			return reply_message(ctx, sd, resp, resp_len, addr);
 		}
 
-		link_data->discovered = DISCOVERY_DISCOVERED;
+		link_data->discovery.flag = DISCOVERY_DISCOVERED;
 		resp->status =
 			SET_MCTP_EID_ASSIGNMENT_STATUS(MCTP_SET_EID_REJECTED) |
 			SET_MCTP_EID_ALLOCATION_STATUS(MCTP_SET_EID_POOL_NONE);
@@ -1009,16 +1016,16 @@ static int handle_control_prepare_endpoint_discovery(
 	resp = (void *)resp;
 	mctp_ctrl_msg_hdr_init_resp(&resp->ctrl_hdr, *req);
 
-	if (link_data->discovered == DISCOVERY_UNSUPPORTED) {
+	if (link_data->discovery.flag == DISCOVERY_UNSUPPORTED) {
 		warnx("received prepare for discovery request to unsupported interface %d",
 		      addr->smctp_ifindex);
 		resp->completion_code = MCTP_CTRL_CC_ERROR_UNSUPPORTED_CMD;
 		return reply_message_phys(ctx, sd, resp,
 					  sizeof(struct mctp_ctrl_resp), addr);
 	}
 
-	if (link_data->discovered == DISCOVERY_DISCOVERED) {
-		link_data->discovered = DISCOVERY_UNDISCOVERED;
+	if (link_data->discovery.flag == DISCOVERY_DISCOVERED) {
+		link_data->discovery.flag = DISCOVERY_UNDISCOVERED;
 		warnx("clear discovered flag of interface %d",
 		      addr->smctp_ifindex);
 	}
@@ -1053,13 +1060,13 @@ handle_control_endpoint_discovery(struct ctx *ctx, int sd,
 		return 0;
 	}
 
-	if (link_data->discovered == DISCOVERY_UNSUPPORTED) {
+	if (link_data->discovery.flag == DISCOVERY_UNSUPPORTED) {
 		resp->completion_code = MCTP_CTRL_CC_ERROR_INVALID_DATA;
 		return reply_message(ctx, sd, resp,
 				     sizeof(struct mctp_ctrl_resp), addr);
 	}
 
-	if (link_data->discovered == DISCOVERY_DISCOVERED) {
+	if (link_data->discovery.flag == DISCOVERY_DISCOVERED) {
 		// if we are already discovered (i.e, assigned an EID), then no reply
 		return 0;
 	}
@@ -3460,6 +3467,81 @@ static int bus_link_get_prop(sd_bus *bus, const char *path,
 	return rc;
 }
 
+static int query_discovery_notify(struct link *link)
+{
+	struct mctp_ctrl_cmd_discovery_notify req = { 0 };
+	struct mctp_ctrl_resp_discovery_notify *resp;
+	struct sockaddr_mctp_ext resp_addr;
+	size_t buf_size;
+	uint8_t *buf;
+	int rc;
+
+	mctp_ctrl_msg_hdr_init_req(&req.ctrl_hdr, mctp_next_iid(link->ctx),
+				   MCTP_CTRL_CMD_DISCOVERY_NOTIFY);
+
+	rc = endpoint_query_phys(link->ctx, &link->discovery.notify_dest,
+				 MCTP_CTRL_HDR_MSG_TYPE, &req, sizeof(req),
+				 &buf, &buf_size, &resp_addr);
+	if (rc < 0)
+		goto free_buf;
+
+	if (buf_size != sizeof(*resp)) {
+		warnx("%s: wrong reply length %zu bytes. dest %s", __func__,
+		      buf_size, dest_phys_tostr(&link->discovery.notify_dest));
+		rc = -ENOMSG;
+		goto free_buf;
+	}
+
+	resp = (void *)buf;
+	if (resp->completion_code != 0) {
+		warnx("Failure completion code 0x%02x from %s",
+		      resp->completion_code,
+		      dest_phys_tostr(&link->discovery.notify_dest));
+		rc = -ECONNREFUSED;
+		goto free_buf;
+	}
+
+free_buf:
+	free(buf);
+	return rc;
+}
+
+static int link_discovery_notify_callback(sd_event_source *source,
+					  uint64_t time, void *userdata)
+{
+	struct link *link = userdata;
+	struct ctx *ctx = link->ctx;
+	int rc;
+
+	// sanity check
+	assert(link->discovery.notify_source == source);
+
+	// Discovery notify succeeded
+	if (link->discovery.flag == DISCOVERY_DISCOVERED) {
+		sd_event_source_disable_unref(source);
+		link->discovery.notify_source = NULL;
+		return 0;
+	}
+
+	rc = query_discovery_notify(link);
+	if (rc < 0) {
+		if (ctx->verbose) {
+			warnx("failed to send discovery notify at retry %d: %s",
+			      link->discovery.notify_retries_left,
+			      strerror(-rc));
+		}
+	}
+	link->discovery.notify_retries_left -= 1;
+	if (link->discovery.notify_retries_left == 0) {
+		warnx("failed to send discovery notify after all retries");
+		sd_event_source_disable_unref(source);
+	} else {
+		sd_event_source_set_time_relative(
+			source, link->discovery.notify_retry_delay);
+	}
+	return 0;
+}
+
 static int bus_link_set_prop(sd_bus *bus, const char *path,
 			     const char *interface, const char *property,
 			     sd_bus_message *value, void *userdata,
@@ -4279,7 +4361,7 @@ static int add_interface(struct ctx *ctx, int ifindex)
 	if (!link)
 		return -ENOMEM;
 
-	link->discovered = DISCOVERY_UNSUPPORTED;
+	link->discovery.flag = DISCOVERY_UNSUPPORTED;
 	link->published = false;
 	link->ifindex = ifindex;
 	link->ctx = ctx;
@@ -4309,7 +4391,29 @@ static int add_interface(struct ctx *ctx, int ifindex)
 	}
 
 	if (phys_binding == MCTP_PHYS_BINDING_PCIE_VDM) {
-		link->discovered = DISCOVERY_UNDISCOVERED;
+		link->discovery.flag = DISCOVERY_UNDISCOVERED;
+		// TODO: These numbers are respectively MN1 and MT4, specified in DSP0239
+		// control message timing.
+		//
+		// Might need to extract these to macros like MCTP_I2C_TSYM_* in this file,
+		// or a commit to actually centralize those timing at one place, now that
+		// we have support for detecting link binding type.
+		link->discovery.notify_retries_left = 2;
+		link->discovery.notify_retry_delay = 5000000;
+
+		// For PCIe-VDM, we want an all zeroes address for Route-to-Root-Complex.
+		mctp_nl_hwaddr_len_byindex(
+			ctx->nl, ifindex,
+			&link->discovery.notify_dest.hwaddr_len);
+		memset(link->discovery.notify_dest.hwaddr, 0,
+		       link->discovery.notify_dest.hwaddr_len);
+		link->discovery.notify_dest.ifindex = ifindex;
+
+		sd_event_add_time_relative(ctx->event,
+					   &link->discovery.notify_source,
+					   CLOCK_MONOTONIC, 0, 0,
+					   link_discovery_notify_callback,
+					   link);
 	}
 
 	link->published = true;

tests/test_mctpd_endpoint.py

@@ -22,11 +22,16 @@ async def iface():
 
 
 @pytest.fixture
-async def sysnet(iface):
+async def bo(iface):
+    return Endpoint(iface, bytes([0x10]), eid=8)
+
+
+@pytest.fixture
+async def sysnet(iface, bo):
     system = System()
     await system.add_interface(iface)
     network = Network()
-    network.add_endpoint(Endpoint(iface, bytes([0x10]), eid=8))
+    network.add_endpoint(bo)
     return Sysnet(system, network)
 
 
@@ -113,12 +118,37 @@ class TestDiscovery:
     async def iface(self):
         return System.Interface("mctp0", 1, 1, bytes([0x1D]), 68, 254, True, PhysicalBinding.PCIE_VDM)
 
+    @pytest.fixture
+    async def bo(self, iface):
+        return TestDiscovery.BusOwnerEndpoint(iface, bytes([0x00]), eid=8)
+
+
+    class BusOwnerEndpoint(Endpoint):
+        def __init__(self, *args, **kwargs):
+            super().__init__(*args, **kwargs)
+            self.sem = trio.Semaphore(initial_value=0)
+
+        async def handle_mctp_control(self, sock, addr, data):
+            print(addr, data)
+            flags, opcode = data[0:2]
+            if opcode != 0x0D:
+                return await super().handle_mctp_control(sock, addr, data)
+            dst_addr = MCTPSockAddr.for_ep_resp(self, addr, sock.addr_ext)
+            await sock.send(dst_addr, bytes([flags & 0x1F, opcode, 0x00]))
+            self.sem.release()
+
+
     """ Test simple Discovery sequence """
     async def test_simple_discovery_sequence(self, dbus, mctpd):
         bo = mctpd.network.endpoints[0]
 
         assert len(mctpd.system.addresses) == 0
 
+        # BMC should send a Discovery Notify message
+        with trio.move_on_after(5) as expected:
+            await bo.sem.acquire()
+        assert not expected.cancelled_caught
+
         # no EID yet
         rsp = await bo.send_control(mctpd.network.mctp_socket, MCTPControlCommand(True, 0, 0x02))
         assert rsp.hex(' ') == '00 02 00 00 02 00'