mctpd: Send Discovery Notify on Endpoint role set

Implement the first step of partial discovery, which is notifying the
bus owner of our presence on the bus.

Tested: Discovery Notify message is sent when setting role on interface.

    Jul 15 08:33:42 evb-endpoint mctpd[3322]: mctpd: read_message got from sockaddr_mctp_ext eid 8 net 1 type 0x00 if 2 hw len 2 0x80:08 len 3
    Jul 15 08:33:42 evb-endpoint mctpd[3322]: mctpd: Failure completion code 0x05 from physaddr if 2 hw len 2 0x00:00
    Jul 15 08:33:42 evb-endpoint mctpd[3322]: mctpd: Warning: discovery notify on interface 'mctppcie0' failed: Connection refused

(My Root Complex does not handle Discovery Notify message yet, but
can confirm that the message is sent)

Signed-off-by: Khang Nguyen Duy <khangng@amperecomputing.com>

Author: Khang Nguyen

CHANGELOG.md

@@ -15,6 +15,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 5. mctpd: New test infrastructure for control procotol messaging to mctpd
 6. mctpd: Add a configuration file facility, defaulting to /etc/mctpd.conf.
 7. mctpd: Add mctp/interfaces/<name> D-Bus object
+8. mctpd: Send Discovery Notify on Endpoint role set
 
 ### Changed
 

src/mctpd.c

@@ -2893,6 +2893,49 @@ static int bus_link_get_prop(sd_bus *bus,
 	return rc;
 }
 
+static int notify_discovery(ctx *ctx, int ifindex)
+{
+	int rc = 0;
+	dest_phys desti = { 0 }, *dest = &desti;
+	struct mctp_ctrl_cmd_discovery_notify req = { 0 };
+	struct mctp_ctrl_resp_discovery_notify *resp;
+	uint8_t *buf;
+	size_t buf_size;
+	struct sockaddr_mctp_ext resp_addr;
+
+	dest->ifindex = ifindex;
+	assert(mctp_nl_ifaddr_byindex(ctx->nl, dest->ifindex,
+				      &dest->hwaddr_len));
+	memset(dest->hwaddr, 0, sizeof dest->hwaddr);
+
+	req.ctrl_hdr.command_code = MCTP_CTRL_CMD_DISCOVERY_NOTIFY;
+	req.ctrl_hdr.rq_dgram_inst = RQDI_REQ;
+
+	rc = endpoint_query_phys(ctx, 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(dest));
+		rc = -ENOMSG;
+		goto free_buf;
+	}
+	resp = (void *)buf;
+
+	if (resp->completion_code != 0) {
+		// TODO: make this a debug message?
+		warnx("Failure completion code 0x%02x from %s",
+		      resp->completion_code, dest_phys_tostr(dest));
+		rc = -ECONNREFUSED;
+		goto free_buf;
+	}
+free_buf:
+	free(buf);
+	return rc;
+}
+
 static int bus_link_set_prop(sd_bus *bus,
 		const char *path, const char *interface, const char *property,
 		sd_bus_message *value, void *userdata, sd_bus_error *berr)
@@ -2904,6 +2947,7 @@ static int bus_link_set_prop(sd_bus *bus,
 	link_userdata *lmUserData;
 	int rc;
 	struct role role;
+	int ifindex;
 
 	if (!is_interfaces_path(path)) {
 		sd_bus_error_setf(berr, SD_BUS_ERROR_INVALID_ARGS,
@@ -2919,11 +2963,13 @@ static int bus_link_set_prop(sd_bus *bus,
 		goto out;
 	}
 
-	lmUserData = mctp_nl_get_link_userdata_byname(ctx->nl, link_name);
-	if (!lmUserData) {
+	ifindex = mctp_nl_ifindex_byname(ctx->nl, link_name);
+	if (!ifindex) {
 		rc = -ENOENT;
 		goto out;
 	}
+	lmUserData = mctp_nl_get_link_userdata(ctx->nl, ifindex);
+	assert(lmUserData);
 
 	if (strcmp(property, "Role") != 0) {
 		printf("Unknown property '%s' for %s iface %s\n", property, path, interface);
@@ -2954,6 +3000,16 @@ static int bus_link_set_prop(sd_bus *bus,
 	}
 	lmUserData->role = role.role;
 
+	// Announce on the bus we are endpoint, print warning and ignore error if failed
+	if (lmUserData->role == ENDPOINT_ROLE_ENDPOINT) {
+		rc = notify_discovery(ctx, ifindex);
+		if (rc) {
+			warnx("Warning: discovery notify on interface '%s' failed: %s", link_name,
+			      strerror(-rc));
+			rc = 0;
+		}
+	}
+
 out:
 	set_berr(ctx, rc, berr);
 	return rc;