net: lwm2m: Add support for blockwise GET and FETCH

include/zephyr/net/coap.h

@@ -713,6 +713,20 @@ int coap_get_option_int(const struct coap_packet *cpkt, uint16_t code);
  */
 int coap_get_block1_option(const struct coap_packet *cpkt, bool *has_more, uint8_t *block_number);
 
+/**
+ * @brief Get values from CoAP block2 option.
+ *
+ * Decode block number and block size from option. Ignore the has_more flag
+ * as it should always be zero on queries.
+ *
+ * @param cpkt Packet to be inspected
+ * @param block_number Is set to the number of the block
+ *
+ * @return Integer value of the block size in case of success
+ * or negative in case of error.
+ */
+int coap_get_block2_option(const struct coap_packet *cpkt, uint8_t *block_number);
+
 /**
  * @brief Retrieves BLOCK{1,2} and SIZE{1,2} from @a cpkt and updates
  * @a ctx accordingly.

subsys/net/lib/coap/coap.c

@@ -1303,6 +1303,19 @@ int coap_get_block1_option(const struct coap_packet *cpkt, bool *has_more, uint8
 	return ret;
 }
 
+int coap_get_block2_option(const struct coap_packet *cpkt, uint8_t *block_number)
+{
+	int ret = coap_get_option_int(cpkt, COAP_OPTION_BLOCK2);
+
+	if (ret < 0) {
+		return ret;
+	}
+
+	*block_number = GET_NUM(ret);
+	ret = 1 << (GET_BLOCK_SIZE(ret) + 4);
+	return ret;
+}
+
 int insert_option(struct coap_packet *cpkt, uint16_t code, const uint8_t *value, uint16_t len)
 {
 	uint16_t offset = cpkt->hdr_len;

subsys/net/lib/lwm2m/CMakeLists.txt

@@ -14,6 +14,7 @@ zephyr_library_sources(
     lwm2m_obj_device.c
     lwm2m_rw_link_format.c
     lwm2m_rw_plain_text.c
+    lwm2m_rw_opaque.c
     lwm2m_util.c
     lwm2m_rd_client.c
     )

subsys/net/lib/lwm2m/Kconfig

@@ -83,6 +83,8 @@ config LWM2M_COAP_BLOCK_TRANSFER
 	help
 	  LwM2M messages with a big body that exceed the block size will be split
 	  into blocks for sending.
+	  To append CoAP ETag option into outgoing block transfers, CONFIG_SYS_HASH_FUNC32 should
+	  be enabled.
 
 config LWM2M_CANCEL_OBSERVE_BY_PATH
 	bool "Use path matching as fallback for cancel-observe"

subsys/net/lib/lwm2m/lwm2m_engine.c

@@ -642,7 +642,7 @@ static int socket_recv_message(struct lwm2m_ctx *client_ctx)
 	}
 
 	in_buf[len] = 0U;
-	lwm2m_udp_receive(client_ctx, in_buf, len, &from_addr, handle_request);
+	lwm2m_udp_receive(client_ctx, in_buf, len, &from_addr);
 
 	return 0;
 }
@@ -675,7 +675,9 @@ static int socket_send_message(struct lwm2m_ctx *client_ctx)
 	}
 
 	if (msg->type != COAP_TYPE_CON) {
-		lwm2m_reset_message(msg, true);
+		if (!lwm2m_outgoing_is_part_of_blockwise(msg)) {
+			lwm2m_reset_message(msg, true);
+		}
 	}
 
 	return rc;