mctpd: query endpoint id directly via destination eid

Since downstream endpoints are behind the bridge, available
query_get_endpoint_id() won't be able to redirect the
GET_ENDPOINT_ID command packet behind the bridge physical
address of downstream endpoint would be same as bridge's own.

But we can do direct query to endpoint since routes have already
been layed out when bridge was allocated the eid pool space.

Signed-off-by: Faizan Ali <faizana@nvidia.com>

Author: faizana-nvidia

src/mctpd.c

@@ -2290,6 +2290,53 @@ static int get_endpoint_peer(struct ctx *ctx, sd_bus_error *berr,
 	return 0;
 }
 
+/* DSP0236 section 8.17.6 Reclaiming EIDs from hot-plug devices
+ *
+ * The bus owner/bridge can detect a removed device or devices by
+ * validating the EIDs that are presently allocated to endpoints that
+ * are directly on the bus and identifying which EIDs are missing.
+ * It can do this by attempting to access each endpoint that the bridge
+ * has listed in its routing table as being a device that is directly on
+ * the particular bus. Attempting to access each endpoint can be accomplished
+ * by issuing the Get Endpoint ID command...
+
+
+ * since bridged endpoints are routed from bridge, direct query
+ * to eid should work if gateway routes are in place.
+ */
+static int query_endpoint_poll_commmand(struct peer *peer, mctp_eid_t *resp_eid)
+{
+	struct sockaddr_mctp_ext addr = {0};
+	struct mctp_ctrl_cmd_get_eid req = {0};
+	struct mctp_ctrl_resp_get_eid *resp = NULL;
+
+	uint8_t *buf = NULL;
+	size_t buf_size;
+	uint8_t iid;
+	int rc;
+
+	iid = mctp_next_iid(peer->ctx);
+	mctp_ctrl_msg_hdr_init_req(&req.ctrl_hdr, iid,
+				   MCTP_CTRL_CMD_GET_ENDPOINT_ID);
+	rc = endpoint_query_peer(peer, MCTP_CTRL_HDR_MSG_TYPE, &req,
+				 sizeof(req), &buf, &buf_size, &addr);
+	if (rc < 0)
+		goto out;
+
+	rc = mctp_ctrl_validate_response(buf, buf_size, sizeof(*resp),
+					 peer_tostr_short(peer), iid,
+					 MCTP_CTRL_CMD_GET_ENDPOINT_ID);
+	if (rc)
+		goto out;
+
+	resp = (void *)buf;
+	*resp_eid = resp->eid;
+
+out:
+	free(buf);
+	return rc;
+}
+
 static int query_get_peer_msgtypes(struct peer *peer)
 {
 	struct sockaddr_mctp_ext addr;