net: lwm2m: add gateway callback to handle prefixed messages

Adding a callback for handling lwm2m messages with prefixed paths defined
by the gateway object. If CONFIG_LWM2M_GATEWAY_OBJ_SUPPORT is set,
each path is checked for the prefix stored in the object instances of the
gateway object 25. If prefixes match the msg is passed to the gw_msg_cb.

Signed-off-by: Simon Walz <[email protected]>

subsys/net/lib/lwm2m/lwm2m_message_handling.c

@@ -46,6 +46,7 @@ LOG_MODULE_REGISTER(LOG_MODULE_NAME);
 #include "lwm2m_object.h"
 #include "lwm2m_obj_access_control.h"
 #include "lwm2m_obj_server.h"
+#include "lwm2m_obj_gateway.h"
 #include "lwm2m_rw_link_format.h"
 #include "lwm2m_rw_oma_tlv.h"
 #include "lwm2m_rw_plain_text.h"
@@ -479,7 +480,7 @@ void lwm2m_engine_context_init(struct lwm2m_ctx *client_ctx)
 }
 /* utility functions */
 
-static int coap_options_to_path(struct coap_option *opt, int options_count,
+int coap_options_to_path(struct coap_option *opt, int options_count,
 				struct lwm2m_obj_path *path)
 {
 	uint16_t len,
@@ -2268,6 +2269,15 @@ static int handle_request(struct coap_packet *request, struct lwm2m_message *msg
 		msg->token = token;
 	}
 
+	if (IS_ENABLED(CONFIG_LWM2M_GATEWAY_OBJ_SUPPORT)) {
+		r = lwm2m_gw_handle_req(msg);
+		if (r == 0) {
+			return 0;
+		} else if (r != -ENOENT) {
+			goto error;
+		}
+	}
+
 	/* parse the URL path into components */
 	r = coap_find_options(msg->in.in_cpkt, COAP_OPTION_URI_PATH, options, ARRAY_SIZE(options));
 	if (r < 0) {

subsys/net/lib/lwm2m/lwm2m_message_handling.h

@@ -39,6 +39,8 @@
 #define NUM_OUTPUT_BLOCK_CONTEXT CONFIG_LWM2M_NUM_OUTPUT_BLOCK_CONTEXT
 #endif
 
+int coap_options_to_path(struct coap_option *opt, int options_count,
+				struct lwm2m_obj_path *path);
 /* LwM2M message functions */
 struct lwm2m_message *lwm2m_get_message(struct lwm2m_ctx *client_ctx);
 struct lwm2m_message *find_msg(struct coap_pending *pending, struct coap_reply *reply);

subsys/net/lib/lwm2m/lwm2m_obj_gateway.c

@@ -59,6 +59,7 @@ static struct lwm2m_engine_obj_field fields[] = {
 static struct lwm2m_engine_obj_inst inst[MAX_INSTANCE_COUNT];
 static struct lwm2m_engine_res res[MAX_INSTANCE_COUNT][GATEWAY_MAX_ID];
 static struct lwm2m_engine_res_inst res_inst[MAX_INSTANCE_COUNT][RESOURCE_INSTANCE_COUNT];
+lwm2m_engine_gateway_msg_cb gateway_msg_cb[MAX_INSTANCE_COUNT];
 
 static int prefix_validation_cb(uint16_t obj_inst_id, uint16_t res_id, uint16_t res_inst_id,
 				uint8_t *data, uint16_t data_len, bool last_block,
@@ -146,6 +147,57 @@ static struct lwm2m_engine_obj_inst *lwm2m_gw_create(uint16_t obj_inst_id)
 	return &inst[index];
 }
 
+int lwm2m_gw_handle_req(struct lwm2m_message *msg)
+{
+	struct coap_option options[4];
+	int ret;
+
+	ret = coap_find_options(msg->in.in_cpkt, COAP_OPTION_URI_PATH, options,
+				ARRAY_SIZE(options));
+	if (ret < 0) {
+		return ret;
+	}
+
+	for (int index = 0; index < MAX_INSTANCE_COUNT; index++) {
+		/* Skip uninitialized objects */
+		if (!inst[index].obj) {
+			continue;
+		}
+
+		char *prefix = device_table[index].prefix;
+		size_t prefix_len = strlen(prefix);
+
+		if (prefix_len != options[0].len) {
+			continue;
+		}
+		if (strncmp(options[0].value, prefix, prefix_len) != 0) {
+			continue;
+		}
+
+		if (gateway_msg_cb[index] == NULL) {
+			return -ENOENT;
+		}
+		/* Delete prefix from path*/
+		ret = coap_options_to_path(&options[1], ret - 1, &msg->path);
+		if (ret < 0) {
+			return ret;
+		}
+		return gateway_msg_cb[index](msg);
+	}
+	return -ENOENT;
+}
+
+int lwm2m_register_gw_callback(uint16_t obj_inst_id, lwm2m_engine_gateway_msg_cb cb)
+{
+	for (int index = 0; index < MAX_INSTANCE_COUNT; index++) {
+		if (inst[index].obj_inst_id == obj_inst_id) {
+			gateway_msg_cb[index] = cb;
+			return 0;
+		}
+	}
+	return -ENOENT;
+}
+
 static int lwm2m_gw_init(void)
 {
 	int ret = 0;

subsys/net/lib/lwm2m/lwm2m_obj_gateway.h

@@ -9,6 +9,8 @@
 #ifndef __LWM2M_OBJ_GATEWAY__
 #define __LWM2M_OBJ_GATEWAY__
 
+#include <lwm2m_object.h>
+
 /* LwM2M Gateway resource IDs */
 /* clang-format off */
 #define LWM2M_GATEWAY_DEVICE_RID             0
@@ -17,4 +19,42 @@
 #define LWM2M_GATEWAY_IOT_DEVICE_OBJECTS_RID 3
 /* clang-format on */
 
+/**
+ * @brief A callback which handles the prefixed messages from the server.
+ *
+ * The callback gets triggered each time the prefix in front of a received lwm2m
+ * msg path matches the prefix set in the LWM2M_GATEWAY_PREFIX_RID buffer.
+ *
+ * It must handle the content of the coap message completely.
+ * In case of success the LwM2M engine will then send the formatted coap message,
+ * otherwise a coap response code is sent.
+ *
+ * Example of returning CoAP response:
+ * @code{.c}
+ * lwm2m_init_message(msg);
+ * // Write CoAP packet to msg->out.out_cpkt
+ * return 0;
+ * @endcode
+ *
+ *
+ * @return 0 if msg contains a  valid CoAP response.
+ * @return  negative error code otherwise.
+ */
+typedef int (*lwm2m_engine_gateway_msg_cb)(struct lwm2m_message *msg);
+/**
+ * @brief Register a callback which handles the prefixed messages from the server.
+ *
+ * @return 0 on success
+ * @return -ENOENT if no object instance with obj_inst_id was found
+ */
+int lwm2m_register_gw_callback(uint16_t obj_inst_id, lwm2m_engine_gateway_msg_cb cb);
+/**
+ * @brief Check if given message is handled by Gateway callback.
+ *
+ * @return 0 if msg was handled by Gateawy and contains a valid response. Negative error code
+ * otherwise.
+ * @return -ENOENT if this msg was not handled by Gateway object.
+ */
+int lwm2m_gw_handle_req(struct lwm2m_message *msg);
+
 #endif /* __LWM2M_OBJ_GATEWAY__ */