SLM Application: Unable to specify custom HTTP host header.

RE: SLM Application: Unable to specify custom HTTP host header.

Ivan Herrera — Wed, 14 Sep 2022 14:26:17 GMT

Hi Hakon!

Thanks for your reply. We will resort to your solution.

RE: SLM Application: Unable to specify custom HTTP host header.

Håkon Alseth — Mon, 12 Sep 2022 13:34:56 GMT

Hi,

[quote user="Ivan Herrera"]Correct, we want to replace the default Host header but not in the https_client example. In the SLM-application (Serial LTE Modem[/quote]

Yes, I took the https_client sample as it states "host:" in plain text.

[quote user="Ivan Herrera"]

Assume the following situation:

There is a HTTP-server running at IP 127.0.0.1, and it is hosting the following domains:

- test1.nordicsemi.com
- test2.nordicsemi.com

The webserver uses the "Host: <hostname>" HTTP-header to differentiate which website to serve. Our device wants to send requests to both domains. Hence we connect to the webserver by the following command:

- AT#XHTTPCCON=1,"127.0.0.1",80

There is now a connection open with the webserver. We want to send two requests, one to test1.nordicsemi.com and one to test2.nordicsemi.com

We use the following command to specify a request to test1.nordicsemi.com:

[/quote]

You're working around not having DNS.

Wouldn't the workaround be that you provide a valid DNS?

Have you tried setting a secondary DNS manually, via this function call?

https://github.com/nrfconnect/sdk-nrfxlib/blob/v2.1.0-rc1/nrf_modem/include/nrf_socket.h#L809

Here's an example implementation:

struct nrf_in_addr dns;
int err = nrf_inet_pton(NRF_AF_INET, "8.8.8.8", &dns);
if (err != 1) {
    LOG_ERR("Failed to convert custom DNS address to %s, err %d", "8.8.8.8", errno);
    return ;
}
err = nrf_setdnsaddr(NRF_AF_INET, &dns);
if (err) {
    LOG_ERR("Failed to set custom DNS address to %s, err %d", "8.8.8.8", errno);
    return ;
}

Kind regards,

Håkon

RE: SLM Application: Unable to specify custom HTTP host header.

Ivan Herrera — Mon, 12 Sep 2022 12:19:15 GMT

Correct, we want to replace the default Host header but not in the https_client example. In the SLM-application (Serial LTE Modem https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/applications/serial_lte_modem/README.html).

You implemented the following commands:

- AT#XHTTPCCON=<op>[,<host>,<port>[,<sec_tag>]]

- AT#XHTTPCREQ=<method>,<resource>[,<headers>[,<content_type>,<content_length>[,<chunked_transfer>]]]

Assume the following situation:

There is a HTTP-server running at IP 127.0.0.1, and it is hosting the following domains:

- test1.nordicsemi.com
- test2.nordicsemi.com

- AT#XHTTPCCON=1,"127.0.0.1",80

There is now a connection open with the webserver. We want to send two requests, one to test1.nordicsemi.com and one to test2.nordicsemi.com

We use the following command to specify a request to test1.nordicsemi.com:

AT#XHTTPCREQ=GET,"/api/version","Host: test1.nordicsemi.com\r\n"

What we expect to happen is for the SLM to send the following HTTP request:

GET /api/version HTTP/1.1
Host: test1.nordicsemi.com

What actually happens, is that the Nordic Serial LTE Modem application assumes that the IP we provided in XHTTPCON is also the hostname we want to provide in the HTTP-header. The following (invalid) request gets sent out:

GET /api/version HTTP/1.1
Host: 127.0.0.1
Host: test1.nordicsemi.com

Naturally, the HTTP-server responds with status code 400: Invalid request, as there is a duplicate host header in the HTTP-request, which is illegal. We propose that the SLM does not provide its own host-header when the user specifies one themselves.

RE: SLM Application: Unable to specify custom HTTP host header.

Håkon Alseth — Mon, 12 Sep 2022 12:04:49 GMT

Hi,

Just to ensure that I understand the scenario fully, it is the "Host: ..." string in the http-template that you want to replace?

If yes, this is a bit of a strange scenario, as it seems to me that you're requesting a http proxy functionality.

At this point, the DNS (ie. getaddrinfo()) has already been run, and you're connected to the server you're communicating with.

Or is the root problem here the getaddrinfo() call, which is called through slm_util.c::util_resolve_host() ?

Kind regards,

Håkon