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  • Case ID: 287438
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FOTA in nRF91 SLM gets 404 due to double `/` in file path

user115230

I am unable to do a FOTA with the SLM application on a nRF9160. When I try to do a FOTA with the command below, I get a 404 even though I know the URL exists (real host name redacted). For reference, this is on NCS v1.9.1.

AT#XFOTA=1,"http://our.website.com/app_update.bin"

After digging a bit more, I realized that the http_parser_url lib used from Zephyr is returning the file path including the prefixed /. However, it looks like the Nordic download_client library is also adding an implicit / at the beginning of HTTP GET requests. I confirmed that the HTTP GET request was indeed sending up the path //app_update.bin with some added debug logging statements which explains the 404 I was seeing. See: https://github.com/nrfconnect/sdk-nrf/blob/v1.9.1/subsys/net/lib/download_client/src/http.c#L21. As far as I can tell, my usage of the XFOTA AT command follows the examples in the docs here: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/applications/serial_lte_modem/doc/FOTA_AT_commands.html#example

I was able to do a FOTA update by modifying the download_client's GET templates to remove the extra leading /, but this doesn't feel quite right to me, nor a good production solution. I hope I'm missing something simple.

Could I get some input on if I am doing something wrong on my end, and if not if there is a bug here and what a possible fix is?

Thanks!

  • 0

    A little follow up info, I have a work around solution for now in my code that works for now. This might help shed some light on whats going on.

    // File: slm_at_fota.c
// function: do_fota_start

	if (parser.field_set & (1 << UF_PATH)) {
		/* This is a hack to remove the leading '/' in the file path. The Noridc
		 * download_client library adds another implicit leading `/` which will
		 * result in a 404 due to a double `//` on the path. This looks to be a
		 * bug in Noridc code, but we're not sure at this point.
		 * See: https://devzone.nordicsemi.com/f/nordic-q-a/86861/fota-in-nrf91-slm-gets-404-due-to-double-in-file-path
		 */
		if (parser.field_data[UF_PATH].len >= 1 &&
		    file_uri[parser.field_data[UF_PATH].off] == '/') {
			parser.field_data[UF_PATH].off++;
			parser.field_data[UF_PATH].len--;
		}

		strncpy(path, file_uri + parser.field_data[UF_PATH].off,
			parser.field_data[UF_PATH].len);
	} else {
		LOG_ERR("Parse path error");
		return -EINVAL;
	}

  • 0

    Hi Matt,

    Thanks for reporting and sharing your solution. I will forward it to our developer for further investigation.

    Have a good easter holiday!

    Best regards,

    Charlie

  • 0 in reply to user93921

    Hi Charlie, is there any update from the developers? I'm eager to know if this is a bug in the SLM or an error on my side.

  • +1

    Hi Matt,

    Sorry for the late reply, lost your case by mistake.

    I can confirm your fix is correct and this will be fixed on the next NCS  release. Thanks for your contribution.

    Best regards,

    Charlie

  • 0 in reply to user93921

    Thank you Charlie, that's great news. I have a follow on question, does this mean that FOTA update was completely broken in v1.9.1 for the SLM? If so, I'm curious on the details of how that bug slipped in to a production release. We intend to use the SLM in production, and breakage of a critical feature like FOTA update in an SDK release needs some understanding from our side.

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