net: lwm2m_client_utils: Handle retried FOTA writes

When Block N=0 is retransmitted, our FOTA handler might see that
as a completely new FOTA process, if previous one failed.
We should instead return failure if the FOTA is retried as
we already know that we failed the previous time.

If we instead accept the first block, then retries are just
skipped and handled normally.

Signed-off-by: Seppo Takalo <[email protected]>

Author: SeppoTakalo

subsys/net/lib/lwm2m_client_utils/lwm2m/lwm2m_firmware.c

@@ -23,7 +23,7 @@
 #include <zephyr/settings/settings.h>
 /* Firmware update needs access to internal functions as well */
 #include <lwm2m_engine.h>
-
+#include <zephyr/net/coap.h>
 #include <modem/modem_info.h>
 #include <pm_config.h>
 #include <zephyr/sys/reboot.h>
@@ -670,6 +670,34 @@ static void dfu_target_cb(enum dfu_target_evt_id evt)
 	ARG_UNUSED(evt);
 }
 
+static bool is_duplicate_token(void)
+{
+	static uint8_t prev_token[COAP_TOKEN_MAX_LEN];
+	static uint8_t prev_token_len;
+	struct lwm2m_ctx *ctx;
+	struct lwm2m_message *msg;
+
+	ctx = lwm2m_rd_client_ctx();
+	if (!ctx) {
+		return false;
+	}
+
+	msg = (struct lwm2m_message *) ctx->processed_req;
+	if (!msg) {
+		return false;
+	}
+	if (msg->tkl == 0) {
+		return false;
+	}
+	if (msg->tkl == prev_token_len &&
+	    memcmp(msg->token, prev_token, prev_token_len) == 0) {
+		return true;
+	}
+	memcpy(prev_token, msg->token, msg->tkl);
+	prev_token_len = msg->tkl;
+	return false;
+}
+
 static int firmware_block_received_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,
 				      size_t total_size, size_t offset)
@@ -691,6 +719,11 @@ static int firmware_block_received_cb(uint16_t obj_inst_id, uint16_t res_id, uin
 			return -EAGAIN;
 		}
 
+		if (is_duplicate_token()) {
+			LOG_DBG("Duplicate token, don't restart DFU");
+			return -EAGAIN;
+		}
+
 		ongoing_obj_id = obj_inst_id;
 		client_acknowledge();