net: lwm2m: Fix composite read on SenML-CBOR

Composite read was incorrectly trying to parse CoAP packet
instead of payload of the packet.

Signed-off-by: Seppo Takalo <seppo.takalo@nordicsemi.no>

subsys/net/lib/lwm2m/lwm2m_message_handling.c

@@ -413,12 +413,6 @@ STATIC int prepare_msg_for_send(struct lwm2m_message *msg)
 
 #endif
 
-bool lwm2m_outgoing_is_part_of_blockwise(struct lwm2m_message *msg)
-{
-	return msg->block_send;
-}
-
-
 void lwm2m_engine_context_close(struct lwm2m_ctx *client_ctx)
 {
 	struct lwm2m_message *msg;

subsys/net/lib/lwm2m/lwm2m_message_handling.h

@@ -75,6 +75,10 @@ enum coap_block_size lwm2m_default_block_size(void);
 
 int lwm2m_parse_peerinfo(char *url, struct lwm2m_ctx *client_ctx, bool is_firmware_uri);
 void lwm2m_clear_block_contexts(void);
-bool lwm2m_outgoing_is_part_of_blockwise(struct lwm2m_message *msg);
+
+static inline bool lwm2m_outgoing_is_part_of_blockwise(struct lwm2m_message *msg)
+{
+	return msg->block_send;
+}
 
 #endif /* LWM2M_MESSAGE_HANDLING_H */

subsys/net/lib/lwm2m/lwm2m_rw_senml_cbor.c

@@ -836,12 +836,15 @@ static uint8_t parse_composite_read_paths(struct lwm2m_message *msg,
 	uint_fast8_t dret;
 	int len;
 	int ret;
+	char *payload;
+	uint16_t in_len;
 
 	setup_in_fmt_data(msg);
 
 	fd = engine_get_in_user_data(&msg->in);
+	payload = (char *)coap_packet_get_payload(msg->in.in_cpkt, &in_len);
 
-	dret = cbor_decode_lwm2m_senml(ICTX_BUF_R_REGION(&msg->in), &fd->dcd, &isize);
+	dret = cbor_decode_lwm2m_senml(payload, in_len, &fd->dcd, &isize);
 
 	if (dret != ZCBOR_SUCCESS) {
 		__ASSERT_NO_MSG(false);